CONTROL OF SO _X EMISSIONS DURING CATALYST MANUFACTURE This application claims the benefit of priority to PCT Application No. PCT/CN2020/088770, filed May 6, 2020, the contents of which are incorporated by reference herein in their entirety. The present disclosure relates generally to the field of exhaust gas treatment catalysts and methods for the preparation thereof. Over time, the harmful components of nitrogen oxides (NO _x ) have led to atmospheric pollution. NOx is contained in exhaust gases, such as from internal combustion engines (e.g., in automobiles and trucks), from combustion installations (e.g., power stations heated by natural gas, oil, or coal), and from nitric acid production plants. Various treatment methods have been used for the treatment of NO _x -containing gas mixtures to decrease atmospheric pollution. One type of treatment involves catalytic reduction of nitrogen oxides. There are two processes: (1) a nonselective reduction process where carbon monoxide, hydrogen, or a lower hydrocarbon is used as a reducing agent; and (2) a selective reduction process where ammonia or an ammonia precursor is used as a reducing agent. In the selective reduction process, a high degree of nitrogen oxide removal can be achieved with a small amount of reducing agent. The selective reduction process is referred to as a Selective Catalytic Reduction (SCR) process. The SCR process uses catalytic reduction of nitrogen oxides with a reductant (e.g., ammonia) in the presence of atmospheric oxygen, resulting in the formation predominantly of nitrogen and steam: 4NO+4NH ₃ +O ₂ → 4N ₂ +6H ₂ O (standard SCR reaction) 2NO2+4NH3+O2 → 3N2+6H2O (slow SCR reaction) NO+NO2+2NH3 → 2N2+3H2O (fast SCR reaction) Catalysts employed in the SCR process may retain good catalytic activity over a wide range of temperature conditions of use, for example, 200 °C to 600 °C or higher, under hydrothermal conditions. SCR catalysts are employed in hydrothermal conditions, such as during the regeneration of a soot filter, as a component of the exhaust gas treatment system used for the removal of particles. Suitable catalysts for use in the SCR process include metal-promoted zeolites, which have been used in SCR of nitrogen oxides with a reductant, such as ammonia, urea, or a hydrocarbon in the presence of oxygen. Another suitable type of SCR catalyst includes vanadia (V ₂ O ₅ ) and/or tungsta (WO ₃ ) as active agents, which are supported on titania (titanium dioxide, TiO ₂ ). These so-called "V-SCR" catalysts are attractive because of their high NOx conversion, low cost, resistance to sulfur poisoning, and ability to reduce hydrocarbon emissions. Titania is a refractory metal oxide which is used not only as such V-SCR catalysts, but also as a support material for various catalytic species in, for example, Diesel Oxidation Catalysts (DOCs). Titania, as well as other catalyst raw materials, are prepared using a process which utilizes sulfate salts. Materials such as titania so produced may contain residual sulfate ions. Subsequent catalyst preparation may utilize such materials as water- based slurries (e.g., in the production of V-SCR catalysts from tungsta-titania support material), and processes involving water-based slurries include drying and calcination steps. In some processes, drying occurs near 100 °C to remove process water. Thereafter, the catalyst is calcined (e.g., further heated to between 450 °C and 600 °C) to decompose and oxidize precursor materials (e.g., organic and metal salts), providing the active catalyst. During the calcination step, these sulfates may be decomposed and released from the calcining oven in the form of sulfur-containing off- gases. Such sulfur-containing off-gases are present as a mixture of sulfur dioxide (SO ₂ ) and sulfur trioxide (SO3), and together are often abbreviated as sulfur oxides (SOx). These sulfur oxides can react with water to form corrosive acids (e.g., sulfuric acid), leading to premature failure of oven duct work materials. Sulfuric acid also has health and environmental consequences if released to the environment. Reducing material failure due to sulfuric acid corrosion may include use of special and often expensive corrosion resistant materials. Federal, state and local authorities have enacted regulations to minimize SO _x emissions to the environment. Compliance with these regulations often involve the installation and operation of expensive equipment called scrubbers. In some industries, a way to avoid these costs is to substitute the sulfate-containing raw material for other materials that do not contain sulfates. However, this is not presently a viable option for preparation of exhaust gas treatment catalysts, due to the unique nature of the requisite materials and their properties. Preventing SO _x emission would reduce maintenance requirements in the production plant, would allow for the use of cheaper, less corrosion resistant duct work materials, and would reduce the cost of compliance with local air quality standards. Accordingly, there is a need in the art for avoiding the release of SO _x during the calcination of sulfate-containing catalyst materials, such as titania-based catalyst materials. The present disclosure generally provides means to control SOx (e.g., sulfur oxides, such as SO2 and/or SO3) emissions during the calcination of refractory support materials containing residual sulfate. In some embodiments according to the present disclosure, some water soluble, sulfate-forming components may combine with such residual sulfate to form thermally stable sulfates, which are effective in preventing the release of SOx during calcination. Accordingly, in one aspect is provided a process for preparing a catalyst component comprising a refractory metal oxide. The process comprises: preparing a mixture comprising a residual sulfate-containing refractory metal oxide and a water soluble, sulfur-free metal salt; drying the mixture to form a dried material; and calcining the dried material to form a catalyst composition comprising a refractory metal oxide and a thermally stable metal sulfate comprising a metal of the water soluble, sulfur-free metal salt. In some embodiments, at least a portion of the metal salt from the water, soluble sulfur-free metal salt reacts with the residual sulfate from the residual sulfate-containing refractory metal oxide during one or more of the preparing, drying, or calcining steps, wherein forming the thermally stable metal sulfate. In some embodiments, the emission of sulfur oxides during calcining is reduced by sequestering the residual sulfate in the thermally stable metal sulfate. In some embodiments, preparing the mixture comprises impregnating the residual sulfate-containing refractory metal oxide with an aqueous solution of the water-soluble, sulfur-free metal salt. In some embodiments, the drying is performed at a temperature ranging from about 25 °C to about 200 °C. In some embodiments, the calcining is performed at a temperature ranging from about 400 °C to about 600 °C. In some embodiments, the thermally stable metal sulfate is stable toward thermal decomposition at a temperature of up to about 600 °C. In some embodiments, the metal salt has a solubility in water of at least about 1 g/100 ml at a temperature of about 20 °C. In some embodiments, the metal of the metal salt is an alkaline earth metal or a rare earth metal. In some embodiments, the metal of the metal salt is chosen from magnesium, calcium, strontium, barium, cerium, and combinations thereof. In some embodiments, the metal of the metal salt is barium. In some embodiments, the metal salt comprises anions chosen from acetate, nitrate, carbonate, bicarbonate, citrate, chloride, hydroxide, and mixtures thereof. In some embodiments, the residual sulfate-containing refractory metal oxide comprises residual sulfate in a quantity ranging from about 0.1 % to about 10 % by weight. In some embodiments, the metal salt is added in at least a stoichiometric quantity, based on the amount of residual sulfate present in the residual sulfate-containing refractory metal oxide. In some embodiments, the metal salt is added in amount by weight on a metal basis ranging from about 0.001 grams to about 0.75 grams per gram of refractory metal oxide, from about 0.01 grams to about 0.7 grams per gram of refractory metal oxide, from about 0.03 grams to about 0.6 grams per gram of refractory metal oxide, from about 0.05 grams to about 0.5 grams per gram of refractory metal oxide, or from about 0.1 grams to about 0.35 grams per gram of refractory metal oxide. In some embodiments, the residual sulfate-containing refractory metal oxide comprises titania, alumina, silica, zirconia, ceria, or combinations thereof. In some embodiments, the residual sulfate-containing refractory metal oxide comprises titania. In some embodiments, the titania further comprises an oxide of tungsten, vanadium, iron, molybdenum, nickel, cobalt, copper, chromium, manganese, tin, or combination(s) thereof. In some embodiments, the residual sulfate-containing refractory metal oxide is titania containing tungsten (VI) oxide. In some embodiments, the catalyst component comprising the refractory metal oxide is a selective catalytic reduction catalyst component. In some embodiments, process further comprises impregnating the refractory metal oxide with a vanadium component. In another aspect is provided a catalyst component comprising a refractory metal oxide, the catalyst component prepared by a process comprising: preparing a mixture comprising a residual-sulfate-containing refractory metal oxide, and a water soluble, sulfur- free metal salt; drying the mixture to form a dried material; and calcining the dried material to form a catalyst composition comprising the refractory metal oxide and a thermally stable metal sulfate comprising a metal of the metal salt. In another aspect is provided a catalyst component comprising a refractory metal oxide and a non-exogenous, thermally stable metal sulfate. Example Embodiments: The disclosure includes, without limitation, the following embodiments. Embodiment 1: A process for preparing a catalyst component, the process comprising: preparing a mixture comprising a residual sulfate-containing refractory metal oxide and a water soluble, sulfur-free metal salt; drying the mixture to form a dried material; and calcining the dried material to form a catalyst composition comprising a refractory metal oxide and a thermally stable metal sulfate comprising a metal of the water soluble, sulfur- free metal salt. Embodiment 2: The process of embodiment 1, wherein at least a portion of the metal salt from the water, soluble sulfur-free metal salt reacts with the residual sulfate from the residual sulfate-containing refractory metal oxide during one or more of the preparing, drying, or calcining steps, wherein forming the thermally stable metal sulfate. Embodiment 3: The process of embodiment 1 or 2, wherein the emission of sulfur oxides during calcining is reduced by sequestering the residual sulfate in the thermally stable metal sulfate. Embodiment 4: The process of any one of embodiments 1-3, wherein preparing the mixture comprises impregnating the residual sulfate-containing refractory metal oxide with an aqueous solution of the water-soluble, sulfur-free metal salt. Embodiment 5: The process of any one of embodiments 1-4, wherein the drying is performed at a temperature ranging from about 25 °C to about 200 °C. Embodiment 6: The process of any one of embodiments 1-5, wherein the calcining is performed at a temperature ranging from about 400 °C to about 600 °C. Embodiment 7: The process of any one of embodiments 1-6, wherein the thermally stable metal sulfate is stable toward thermal decomposition at a temperature of up to about 600 °C. Embodiment 8: The process of any one of embodiments 1-7, wherein the metal salt has a solubility in water of at least about 1 g/100 ml at a temperature of about 20 °C. Embodiment 9: The process of any one of embodiments 1-8, wherein the metal of the metal salt is an alkaline earth metal or a rare earth metal. Embodiment 10: The process of any one of embodiments 1-9, wherein the metal of the metal salt is chosen from magnesium, calcium, strontium, barium, cerium, and combinations thereof. Embodiment 11: The process of any one of embodiments 1-10, wherein the metal of the metal salt is barium. Embodiment 12: The process of any one of embodiments 1-11, wherein the metal salt comprises anions chosen from acetate, nitrate, carbonate, bicarbonate, citrate, chloride, hydroxide, and mixtures thereof. Embodiment 13: The process of any one of embodiments 1-12, wherein the metal salt is added in at least a stoichiometric quantity, based on the amount of residual sulfate present in the residual sulfate-containing refractory metal oxide. Embodiment 14: The process of any one of embodiments 1-13, wherein the residual sulfate- containing refractory metal oxide comprises residual sulfate in a quantity ranging from about 0.1% to about 10% by weight. Embodiment 15: The process of any one of embodiments 1-14, wherein the metal salt is added in amount by weight on a metal basis ranging from about 0.001 grams to about 0.75 grams per gram of refractory metal oxide, from about 0.01 grams to about 0.7 grams per gram of refractory metal oxide, from about 0.03 grams to about 0.6 grams per gram of refractory metal oxide, from about 0.05 grams to about 0.5 grams per gram of refractory metal oxide, or from about 0.1 grams to about 0.35 grams per gram of refractory metal oxide material. Embodiment 16: The process of any one of embodiments 1-15, wherein the residual sulfate-containing refractory metal oxide comprises titania, alumina, silica, zirconia, ceria, or combinations thereof. Embodiment 17: The process of any one of embodiments 1-16, wherein the residual sulfate-containing refractory metal oxide comprises titania. Embodiment 18: The process of any one of embodiments 1-17, wherein the residual sulfate-containing refractory metal oxide further comprises an oxide of tungsten, vanadium, iron, molybdenum, nickel, cobalt, copper, chromium, manganese, tin, or a combination thereof. Embodiment 19: The process of any one of embodiments 1-18, wherein the residual sulfate- containing refractory metal oxide is titania containing tungsten (VI) oxide. Embodiment 20: The process of any one of embodiments 1-19, wherein the catalyst component comprising the refractory metal oxide is a selective catalytic reduction catalyst component. Embodiment 21: The process of any one of embodiments 1-20, further comprising impregnating the refractory metal oxide with a vanadium component. Embodiment 22: A catalyst component comprising a refractory metal oxide, the catalyst component prepared by a process comprising: preparing a mixture comprising a residual sulfate-containing refractory metal oxide, and a water soluble, sulfur-free metal salt; drying the mixture to form a dried material; and calcining the dried material to form a catalyst composition comprising the refractory metal oxide and a thermally stable metal sulfate comprising a metal of the metal salt. Embodiment 23: A catalyst component comprising a refractory metal oxide and a non-exogenous thermally stable metal sulfate. These and other features, aspects, and advantages of the disclosure will be apparent from a reading of the following detailed description together with the accompanying drawings, which are briefly described below. The disclosure includes any combination of two, three, four, or more of the above-noted embodiments as well as combinations of any two, three, four, or more features or elements set forth in this disclosure, regardless of whether such features or elements are expressly combined in a specific embodiment description herein. This disclosure is intended to be read holistically such that any separable features or elements of the disclosed disclosure, in any of its various aspects and embodiments, should be viewed as intended to be combinable unless the context clearly dictates otherwise. Other aspects and advantages of the present disclosure will become apparent from the following. BRIEF DESCRIPTION OF THE DRAWINGS In order to provide an understanding of embodiments of the disclosure, reference is made to the appended drawings, in which reference numerals refer to components of example embodiments of the disclosure. The drawings are provided as examples only, and should not be construed as limiting the disclosure. The disclosure described herein is illustrated by way of example and not by way of limitation in the accompanying figures. For simplicity and clarity of illustration, features illustrated in the figures are not necessarily drawn to scale. Further, where considered appropriate, reference labels have been repeated among the figures to indicate corresponding or analogous elements. FIG. 1 depicts a perspective view of a honeycomb-type substrate which may comprise a catalyst (e.g., a selective catalytic reduction catalyst) washcoat composition, in accordance with some embodiments of the present disclosure. FIG. 2 depicts a is a cross-sectional view of a section of a wall-flow filter substrate, in accordance with some embodiments of the present disclosure, FIG. 3A depicts a cross-sectional view of a layered catalytic article, in accordance with some embodiments of the present disclosure. FIG. 3B depicts a cross-sectional view of a zoned catalytic article, in accordance with some embodiments of the present disclosure. FIG. 3C depicts a cross-sectional view of a layered and zoned catalytic article, in accordance with some embodiments of the present disclosure. FIG. 4 illustrates a schematic depiction of an emission treatment system in which a catalyst article of the present disclosure is utilized, in accordance some embodiments of the present disclosure. FIG.5 depicts line graphs providing changes of percent of original sample weight in accordance with change of temperature, in accordance with some embodiments of the present disclosure. FIG. 6 depicts a graph of the mass spectrometry ion abundance signal versus temperature at a mass-to-charge ratio of 64, in accordance with some embodiments of the present disclosure. FIG. 7 depicts a graph of the mass spectrometry ion abundance signal versus temperature at a mass-to-charge ratio of 46, in accordance with some embodiments of the present disclosure. FIG. 8 depicts an infrared spectrum characterizing the sulfur-oxygen bonds of an example and a reference example, in accordance with some embodiments of the present disclosure. FIG. 9 depicts a bar graph illustrating the NOx reduction of an example and a reference example, before and after calcination, in accordance with some embodiments of the present disclosure. The present disclosure generally provides a method for preparing a catalyst component comprising a refractory metal oxide. The method comprises preparing a mixture comprising a refractory metal oxide including a residual sulfate, and a water soluble, sulfur- free, metal salt; drying the mixture to form a dried material; and calcining the dried material to form a catalyst composition comprising the refractory metal oxide and a thermally stable metal sulfate comprising the metal of the metal salt. According to the present disclosure, residual sulfate present in a refractory metal oxide (e.g., titania) can react under appropriate conditions with an added water soluble metal salt, forming a new and thermally stable sulfate. Further, the presence of such thermally stable sulfates in the refractory metal oxide does not decrease catalytic activity of the catalyst composition comprising the refractory metal oxide. Definitions The articles "a" or "an" herein refers to one or to more than one (e.g. at least one) of the object. As such, the terms “a” (or “an”), “one or more”, and “at least one” are used interchangeably herein. Any ranges cited herein are inclusive. The term "about" used throughout is used to describe and account for small variations. For instance, "about" may mean the numeric value may be modified by ±5%, ±4%, ±3%, ±2%, ±1%, ±0.5%, ±0.4%, ±0.3%, ±0.2%, ±0.1% or ±0.05%. All numeric values are modified by the term "about" whether or not explicitly indicated. Numeric values modified by the term "about" include the specific identified value. For example, "about 5.0" includes 5.0. The term "abatement" means a decrease in the amount, caused by any means. The term "associated" means for instance "equipped with", "connected to" or in "communication with", for example "electrically connected" or in "fluid communication with" or otherwise connected in a way to perform a function. The term "associated" may mean directly associated with or indirectly associated with, for instance through one or more other articles or elements. The term "catalyst" refers to a material that promotes a chemical reaction. The catalyst includes the "catalytically active species" and the "support" that carries or supports the active species. For example, refractory metal oxide particles may be a support for platinum group metal catalytic species. The term "catalytic article" in the disclosure means an article comprising a substrate having a catalyst coating composition. "CSF" refers to a catalyzed soot filter, which is a wall-flow monolith. A wall-flow filter consists of alternating inlet channels and outlet channels, where the inlet channels are plugged on the outlet end and the outlet channels are plugged on the inlet end. A soot- carrying exhaust gas stream entering the inlet channels is forced to pass through the filter walls before exiting from the outlet channels. In addition to soot filtration and regeneration, A CSF may carry oxidation catalysts to oxidize CO and HC to CO2 and H2O, or oxidize NO to NO2 to accelerate the downstream SCR catalysis or to facilitate the oxidation of soot particles at lower temperatures. An SCR catalyst composition can also be coated directly onto a wall-flow filter, which is called SCRoF. As used herein, the phrase "catalyst system" refers to a combination of two or more catalysts, for example, a combination of a first low-temperature NO _x adsorber (LT-NA) catalyst and a second catalyst which may be a diesel oxidation catalyst (DOC), a LNT or a SCR catalyst article. The catalyst system may alternatively be in the form of a washcoat in which the two catalysts are mixed together or coated in separate layers. The term "configured" as used in the description and claims is intended to be an open-ended term as are the terms "comprising" or "containing". The term "configured" is not meant to exclude other possible articles or elements. The term "configured" may be equivalent to "adapted". "DOC" refers to a diesel oxidation catalyst, which converts hydrocarbons and carbon monoxide in the exhaust gas of a diesel engine, as well as oxidizing nitric oxide (NO) to nitrogen dioxide (NO2). In some embodiments, a DOC comprises one or more platinum group metals such as palladium and/or platinum; a support material such as alumina; a zeolite for HC storage; and optionally, promoters and/or stabilizers. In general, the term "effective" means, for example, from about 35% to 100% effective, for instance from about 40%, about 45%, about 50% or about 55% to about 60%, about 65%, about 70%, about 75%, about 80%, about 85%, about 90%, or about 95%, regarding the defined catalytic activity or storage/release activity, by weight or by moles. The term "exhaust stream" or "exhaust gas stream" refers to any combination of flowing gas that may contain solid or liquid particulate matter. The stream comprises gaseous components and is, for example, exhaust of a lean burn engine, which may contain certain non-gaseous components such as liquid droplets, solid particulates and the like. The exhaust gas stream of a combustion engine may further comprise combustion products (CO2 and H2O), products of incomplete combustion (carbon monoxide (CO) and hydrocarbons (HC)), oxides of nitrogen (NOx), combustible and/or carbonaceous particulate matter (soot), and un-reacted oxygen and nitrogen. As used herein, the terms "upstream" and "downstream" refer to relative directions according to the flow of an engine exhaust gas stream from an engine towards a tailpipe, with the engine in an upstream location and the tailpipe and any pollution abatement articles such as filters and catalysts being downstream from the engine. The inlet end of a substrate is synonymous with the "upstream" end or "front" end. The outlet end is synonymous with the "downstream" end or "rear" end. An upstream zone is upstream of a downstream zone. An upstream zone may be closer to the engine or manifold, and a downstream zone may be further away from the engine or manifold. The term "in fluid communication" is used to refer to articles positioned on the same exhaust line, e.g., a common exhaust stream passes through articles that are in fluid communication with each other. Articles in fluid communication may be adjacent to each other in the exhaust line. Alternatively, articles in fluid communication may be separated by one or more articles, also referred to as "washcoated monoliths." The term "functional article" in the disclosure means an article comprising a substrate having a functional coating composition disposed thereon, such as a catalyst and/or sorbent coating composition. As used herein, "impregnated" or "impregnation" refers to permeation of the catalytic material into the porous structure of the support material. "LNT" refers to a lean NOx trap, which is a catalyst containing a platinum group metal, ceria, and an alkaline earth trap material suitable to adsorb NOx during lean conditions (for example, BaO or MgO). Under rich conditions, NOx is released and reduced to nitrogen. As used herein, the terms "nitrogen oxides" or "NO _x " designate the oxides of nitrogen, such as NO, NO2 or N2O. The terms "on" and "over" in reference to a coating layer may be used synonymously. The term "directly on" means in direct contact with. The disclosed articles are referred to in certain embodiments as comprising one coating layer "on" a second coating layer, and such language is intended to encompass embodiments with intervening layers, where direct contact between the coating layers is not required (e.g., "on" is not equated with "directly on"). As used herein, the term "promoted" refers to a component that is added to, e.g., a support material, as opposed to impurities inherent in the support material. As used herein, the term "selective catalytic reduction" (SCR) refers to the catalytic process of reducing oxides of nitrogen to dinitrogen (N ₂ ) using a nitrogenous reductant. As used herein, the term "substrate" refers to the monolithic material onto which the catalyst composition, e.g., catalytic coating, is disposed, in the form of a washcoat. In one or more embodiments, the substrates are flow-through monoliths and monolithic wall-flow filters. Flow-through and wall-flow substrates are also taught, for example, in International Application Publication No. WO2016/070090, which is incorporated herein by reference. A washcoat is formed by preparing a slurry containing a specified solids content (e.g., 30%- 90% by weight) of catalyst in a liquid, which is then coated onto a substrate and dried to provide a washcoat layer. Reference to "monolithic substrate" means a unitary structure that is homogeneous and continuous from inlet to outlet. A washcoat is formed by preparing a slurry containing a certain solid content (e.g., 20%- 90% by weight) of particles in a liquid vehicle, which is then coated onto a substrate and dried to provide a washcoat layer. As used herein, the term "support" refers to any high surface area material, usually a refractory metal oxide material, upon which a catalytic material may be applied. As used herein, the term "washcoat" has its usual meaning in the art of a thin, adherent coating of a catalytic or other material applied to a substrate material, such as a honeycomb-type substrate, which is sufficiently porous to permit the passage of the gas stream being treated. The washcoat can optionally comprise a binder selected from silica, alumina, titania, zirconia, ceria, or a combination thereof. The loading of the binder is generally from about 0.1 to about 10 wt%, based on the weight of the washcoat. As used herein and as described in Heck, Ronald and Farrauto, Robert, Catalytic Air Pollution Control, New York: Wiley-Interscience, 2002, pp. 18-19, a washcoat layer includes a compositionally distinct layer of material disposed on the surface of a monolithic substrate or an underlying washcoat layer. A substrate can contain one or more washcoat layers, and each washcoat layer can be different in some way (e.g., may differ in physical properties thereof such as, for example particle size) and/or may differ in the chemical catalytic functions. "Weight percent (wt%)," if not otherwise indicated, is based on an entire composition free of any volatiles, that is, based on dry solids content. Unless otherwise indicated, all parts and percentages are by weight. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., "such as") provided herein, is intended merely to better illuminate the materials and methods and does not pose a limitation on the scope unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the disclosed materials and methods. All U.S. patent applications, Pre-Grant publications and patents referred to herein are hereby incorporated by reference in their entireties. Process for Preparing A Catalyst Component As a non-limiting example description, the process disclosed herein comprises contacting a residual sulfate-containing refractory metal oxide and a water soluble, sulfur- free, metal salt in a manner such that the residual sulfate reacts with the metal salt, forming a thermally sulfate. In some embodiments, certain refractory metal oxides, for example, titania, contain residual sulfates which are not thermally stable, and decompose under elevated temperature conditions, such as those encountered during calcining of catalyst materials including such refractory metal oxides, resulting in off gassing of sulfur oxides (SOx). Accordingly, in one aspect is provided a process for preparing a catalyst component comprising a refractory metal oxide, the process comprising: preparing a mixture comprising a refractory metal oxide containing a residual sulfate, and a water soluble metal salt; drying the mixture; and calcining the dried mixture. Preparing A Mixture The method as disclosed herein comprises preparing a mixture comprising the residual sulfate-containing refractory metal oxide and the water soluble, sulfur-free metal salt. The mixture can be prepared by any suitable method which provides intimate contact between the components, allowing a reaction between the residual sulfate and the sulfate forming component to at least begin, forming the thermally stable sulfate. In some embodiments, preparing a mixture comprises impregnating the residual sulfate-containing refractory metal oxide with an aqueous solution of the metal salt. As used herein, the term "impregnating" means that a solution containing the water soluble, sulfate- forming component is put into the pores of the residual sulfate-containing refractory metal oxide. In some embodiments, impregnation is achieved by incipient wetness, where a volume of a diluted solution containing water soluble, sulfate-forming component is approximately equal to the pore volume of the refractory metal oxide. Capillary action draws the solution into the pores of the support. Solution added in excess of the support pore volume causes the solution transport to change from a capillary action process to a diffusion process, which is slower. The support material, e.g., in particulate from, can be dry enough to adsorb substantially all of the solution to form a moist solid. Incipient wetness impregnation techniques, also called capillary impregnation or dry impregnation, can be used for the synthesis of heterogeneous materials, e.g., catalysts. Incipient wetness impregnation can lead to a substantially uniform distribution of the solution of the metal salt throughout the pore system of the residual sulfate-containing refractory metal oxide. In some embodiments, preparing a mixture comprises adding the residual sulfate- containing refractory metal oxide and the metal salt to some water to form a slurry. The addition of the residual sulfate-containing refractory metal oxide and the metal salt may be performed sequentially, in either order, or both may be combined and added as a solid mixture. The addition may be performed by adding both components as solid materials to a sufficient quantity of water, or may be performed by adding water to a mixture of both components as solid materials. The resulting slurry may be mixed to ensure adequate contact between the mixture components. One non-limiting example includes mixing in a planetary mixer. The mixture can be mixed for various time periods. For example, the time period can be in the range of 1 second to about 24 hours, such as from about 1 second to about 1 minute; or from about 1 minute, about 5 minutes, about 10 minutes, or about 15 minutes, to about 30 minutes, about 45 minutes, or about 1 hour; or from about 1 hour, about 2 hours, about 3 hours, about 4 hours, about 5 hours, or about 6 hours, to about 12 hours, or about 24 hours. The mixing can be performed at varying temperatures. In some embodiments, the mixing is performed at room temperature. In some embodiments, the mixing is performed at an elevated temperature (e.g., greater than room temperature, such as from about 25 °C to about 100 °C). These manners of preparing a mixture should not be construed as limiting, and other ways of bringing the components into intimate contact which may be known to one of skill in the art are within the scope of the present disclosure. Residual Sulfate-Containing Refractory Metal Oxide The slurry as disclosed herein comprises a residual sulfate-containing refractory metal oxide. As used herein, "refractory metal oxide" (e.g., refractory metal oxide material) refers to porous, metal-containing oxide materials exhibiting chemical and physical stability at high temperatures, such as the temperatures associated with diesel engine exhaust. Example refractory metal oxides include alumina, silica, zirconia, titania, ceria, and physical mixtures or chemical combinations thereof, including atomically-doped combinations and including high surface area or activated compounds, such as activated alumina. As used herein, "residual sulfate-containing" or "including a residual sulfate" means that the refractory metal oxide contains an amount of a sulfate (SO4 ^2- ) species by virtue of the method of production, and which is a thermally unstable sulfate species. To be clear, the refractory metal oxide does not contain sulfate species that are added additionally. Instead, they are present as a generally undesirable impurity. For example, commercial titania is produced by the sulfate process, in which titania is precipitated by hydrolysis of titanyl sulfate. Commercially available titania may contain anywhere from 100 parts per million up to 10% by weight of residual sulfate, but can be in a range of about 1% by weight of sulfate, calculated as H2SO4 and based on the total weight of the titania (TiO2). In some embodiments, the refractory metal oxide material contains (e.g., "includes") residual sulfate in a quantity of from about 0.1% to about 10% by weight, calculated as H2SO4 and based on the total weight of the titania, for example, from about 0.1% to about 1%, or from about 1% to about 10% by weight. To be clear, as used herein, the term "residual sulfate" does not comprise, and may exclude, a sulfate of an alkaline earth metal or rare earth metal, e.g., excluding a sulfate of magnesium, calcium, strontium, barium, or cerium. In some embodiments, the refractory metal oxide material including a residual sulfate comprises alumina (Al2O3), silica (SiO2), zirconia (ZrO2), titania (TiO2), ceria (CeO2), or physical mixtures or chemical combinations thereof. Mixed metal oxides include, but are not limited to, zirconia-alumina, ceria-zirconia, ceria-alumina, lanthana-alumina, baria-alumina, and silica-alumina. In some embodiments, the refractory metal oxide material including a residual sulfate comprises doped alumina materials, such as Si-doped alumina materials (including, but not limited to 1% - 10% SiO2-Al2O3), doped titania materials, such as Si-doped titania materials (including, but not limited to 1% - 10% SiO ₂ -TiO ₂ ) or tungsten-doped titania materials (including, but not limited to 1% - 10% WO ₃ -TiO ₂ ), or doped zirconia materials, such as Si-doped ZrO2 (including, but not limited to 5% - 30% SiO2-ZrO2). In some embodiments, the refractory metal oxide material including a residual sulfate comprises titania. In some embodiments, the titania further comprises an oxide of tungsten, vanadium, iron, molybdenum, nickel, cobalt, copper, chromium, manganese, tin, or a combination thereof. In some embodiments, the refractory metal oxide material including a residual sulfate is titania containing tungsten (VI) oxide (WO ₃ ). In some embodiments, the tungsten oxide is present in an amount of from about 1% to about 10% by weight of the titania, for example, about 1%, about 2%, about 3%, about 4%, about 5%, about 6%, about 7%, about 8%, about 9%, or about 10% by weight of tungsten oxide. Water Soluble, Sulfur-free Metal Salt The process as disclosed herein uses a water soluble, sulfur-free metal salt. As used herein, the term "water soluble" means that the sulfate-forming component readily dissolves in water to form a solution. By "readily dissolves", it is meant that the water solubility of the sulfate-forming component at a temperature of about 20 °C is at least about 1 g per 100 ml of water. For example, suitable water soluble, sulfate-forming components will have a water solubility at about 20 °C of from about 1 g, about 10 g, or about 50 g, to about 100 g, per 100 ml of water. As will be recognized by one of skill in the art, solubility generally rises with increasing temperature. As used herein, the term "sulfur free" means that the metal salt does not comprise, and excludes, sulfur-containing ions, such as sulfate. Metal salts useful in the present process can form a thermally stable sulfate when allowed to react with sulfate ions (e.g., residual sulfate in the refractory metal oxide material). Such metal salts (e.g., in solution) provide the corresponding metal ions which react with sulfate ions (e.g., the residual sulfate present in the refractory metal oxide), forming a new sulfate which is thermally stable. In some embodiments, the term "thermally stable" means that the sulfate material does not decompose to liberate sulfur oxides, when heated to temperatures of up to about 600 °C. In some embodiments, the thermally stable sulfate is stable toward thermal decomposition at temperatures up to about 700 °C, about 800 °C, about 900 °C, or about 1000 °C. For example, the thermal decomposition of barium sulfate takes place at a temperature of over 1580 °C, the thermal decomposition of calcium sulfate takes place at a temperature of 1350 °C - 1400 °C, the thermal decomposition of strontium sulfate takes place at a temperature of over 1300 °C, and the thermal decomposition of magnesium sulfate takes place at a temperature of about 1,124 °C. In some embodiments, the metal of the metal salt is an alkaline earth metal or a rare earth metal. In some embodiments, the metal of the metal salt is chosen from magnesium, calcium, strontium, barium, cerium, and combinations thereof. In some embodiments, the metal is barium. In some embodiments, the metal is calcium. In some embodiments, the metal is magnesium. In some embodiments, the metal is cerium. In some embodiments, the metal is strontium. In some embodiments, each of these metals produces thermally stable sulfates which do not adversely affect catalyst performance. In some embodiments, a salt comprising such metals, and possessing the required water solubility, is suitable. One of skill in the art will recognize suitable salts of the foregoing metals. In some embodiments, the metal salt comprises anions chosen from acetate, nitrate, carbonate, bicarbonate, citrate, chloride, hydroxide, and mixtures thereof. In some embodiments, the metal salt comprises anions chosen from acetate, chloride, and nitrate. In one embodiment, the metal salt is barium acetate. In one embodiment, the metal salt is barium nitrate. In one embodiment, the metal salt is cerium nitrate. The metal salt may be added in various quantities. For example, the metal salt is added in an amount at least sufficient to react with the quantity of residual sulfate present in the refractory metal oxide (e.g., stoichiometric). In some embodiments, the metal salt is added in a stoichiometric quantity, based on the amount of residual sulfate present in the refractory metal oxide. In some embodiments, the metal salt is added in excess of the stoichiometric quantity. In some embodiments, at least a portion of the water-soluble, sulfate-forming component reacts with the residual sulfate, converting substantially all of the residual sulfate to a thermally stable sulfate. In some embodiments, the metal salt is added in amount by weight (on a metal basis) of from about 0.001 to about 0.75 grams per gram of refractory metal oxide material, from about 0.01 to about 0.7 grams per gram of refractory metal oxide material, from about 0.03 to about 0.6 grams per gram of refractory metal oxide material, from about 0.05 to about 0.5 grams per gram of refractory metal oxide material, or from about 0.1 grams to about 0.35 grams per gram of refractory metal oxide material. In some embodiments, at least a portion of the metal salt reacts with the residual sulfate during one or more of the preparing the mixture, drying the mixture, or calcining the mixture, forming a thermally stable sulfate material. In some embodiments, substantially all of the metal salt reacts with the residual sulfate during one or more of the preparing the mixture, drying the mixture, or calcining the mixture, forming a thermally stable sulfate material. Drying Following preparation of the mixture, the mixture is dried, e.g., at a temperature ranging from about 25 °C to about 200 °C, for example, at a temperature ranging from about 100 °C to about 150 °C) for a period of time (e.g., from 1 hour - 3 hours). During this drying, the reaction between the residual sulfate and the sulfate forming component may continue, or may be complete prior to drying. Optionally, depending on the moisture content of the mixture, drying may be accomplished directly during the calcining step. Calcining Following the drying step, the dried slurry is then calcined by heating, e.g., at a temperature ranging from about 400 °C to about 600 °C, e.g., for a time ranging from about 10 minutes to about 3 hours. Following calcining, the catalyst component can be viewed as essentially solvent-free, and the conversion of residual sulfate to the thermally stable sulfate material completes. Catalyst Compositions and Methods In another aspect is provided a catalyst component comprising a refractory metal oxide, the catalyst component prepared by the method disclosed here. In a still further aspect is provided a catalyst component comprising a refractory metal oxide and a thermally stable metal sulfate, each as described herein, wherein the thermally stable metal sulfate is non-exogenous. In some embodiments, "non-exogenous" means that the thermally stable metal sulfate was not initially present in the refractory metal oxide, and has been formed in situ by the reaction of an added metal salt and residual sulfate present in the refractory metal oxide. In some embodiments, the catalyst component prepared according to the disclosed process may be useful as a support material for catalytic species in a number of different catalyst types having various compositions. As non-limiting examples, the refractory metal oxide materials prepared as disclosed herein may be used in selective catalytic reduction catalyst (SCR) compositions, oxidation catalyst compositions (e.g., Diesel Oxidation Catalysts (DOC), and lean NOx trap (LNT) catalysts. In some embodiments, catalytic species (e.g., catalytic metals such as platinum group metals, base metals, and/or transition metals) may be supported on the catalyst component comprising the refractory metal oxide to provide such catalysts. Accordingly, in some embodiments, the process further comprises impregnating the refractory metal oxide with a catalytic species. In some embodiments, the catalytic species is a vanadium component or a platinum group metal (PGM) component. This further impregnation step may be performed either after calcining, or before (e.g., during the mixture preparation). In some embodiments, impregnation with the catalytic species is performed on a calcined refractory metal oxide as disclosed herein. In some embodiments, impregnation with the catalytic species is performed on a refractory metal oxide as disclosed herein which has not been calcined, followed by a subsequent calcination. SCR Compositions In one aspect is provided an SCR catalyst comprising a refractory metal oxide comprising a thermally stable sulfate as disclosed herein. In some embodiments, the refractory metal oxide comprises titania. In some embodiments, the SCR catalyst composition is a so-called "V-SCR", comprising one or more vanadium components supported on a refractory metal oxide (e.g., TiO2, SiO2, WO3, Al2O3, ZrO2, or a combination thereof). Such compositions are generally referred to herein as "vanadia-based compositions." In some embodiments, the vanadium can be in various forms, e.g., including but not limited to, free vanadium, vanadium ion, or vanadium oxides (vanadia), such as vanadium pentoxide (V2O5). As used herein, "vanadia" or "vanadium oxide" is intended to cover any oxide of vanadium, including vanadium pentoxide. In certain embodiments, a vanadia-based composition comprises a mixed oxide comprising vanadia. The amount of vanadia in the mixed oxide can vary and, in some embodiments, ranges from about 1 percent to about 10 percent by weight based on the total weight of the mixed oxide. For example, the amount of vanadia can be at least 1 percent, at least 2 percent, at least 3 percent, at least 4 percent, at least 5 percent, or at least 6 percent, with an upper limit of about 10 percent by weight or no more than 10 percent, no more than 9 percent, no more than 8 percent, no more than 7 percent, no more than 6 percent, no more than 5 percent, or no more than 4 percent, with a lower limit of about 1 percent by weight. Certain useful SCR compositions comprising vanadium supported on a refractory metal oxide such as alumina, silica, zirconia, titania, ceria, and combinations thereof, are described in for example, U.S. Patent Nos. 4,010,238 to Shiraishi et al., 4,085,193 to Nakajima et al., 5,137,855 to Hegedus et al., and 4,466,947 to Imanari et al., as well as in U.S. Patent Application Publication No. 2017/0341026 to Chen et al., each of which are incorporated by reference herein in their entireties. In some embodiments, the SCR catalyst comprises a mixed oxide comprising vanadia/titania (V2O5/TiO2), e.g., in the form of titania onto which vanadia has been dispersed. The vanadia/titania can optionally be activated or stabilized with tungsten (e.g., WO3) to provide V2O5/TiO2/WO3, e.g., in the form of titania onto which V2O5 and WO3 have been dispersed. In some embodiments, the vanadia is not truly in the form of a mixed metal oxide; rather, the metal oxide components (e.g., titania and vanadia) may be present as discrete particles. The amount of tungsten in such embodiments can vary and can range, e.g., from about 0.5 percent to about 10 percent by weight, based on the total weight of the mixed oxide. For example, the amount of tungsten can be at least 0.5 percent, at least 1 percent, at least 2 percent, at least 3 percent, at least 4 percent, at least 5 percent, or at least 6 percent, with an upper limit of about 10 percent by weight or no more than 10 percent, no more than 9 percent, no more than 8 percent, no more than 7 percent, no more than 6 percent, no more than 5 percent, or no more than 4 percent, with a lower limit of about 0.5 percent by weight. Examples of vanadia-based SCR compositions can comprise components including, but not limited to, V ₂ O ₅ /TiO ₂ , V ₂ O ₅ /WO ₃ /TiO ₂ , V ₂ O ₅ /WO ₃ /TiO ₂ /SiO ₂ , or combinations thereof. Additional vanadium-containing SCR catalyst compositions are described, for example, in U.S. Patent Nos. 4,782,039 to Lindsey; 8,465,713 to Schermanz et al.; and 8,975,206 to Schermanz et al., which are incorporated herein by reference in their entireties. In some embodiments, vanadia-based SCR compositions can comprise other active components (e.g., other metal oxides). For example, in some embodiments, vanadia-based SCR compositions suitable for use in the disclosed systems comprise vanadia and antimony. Such a vanadia-based SCR composition, in certain embodiments, comprises a composite oxide comprising vanadium and antimony, which can be supported on a refractory metal oxide. Examples of vanadia-based SCR compositions comprising vanadia and antimony are disclosed in U.S. Patent No. 4,221,768 to Inoue et al.; and US Publ. Nos. 2018/0304236 to Zhao et al. and 2019/0344247 to Zhao et al., each of which is incorporated herein by reference in their entireties. Various additional SCR compositions are also disclosed, for example, in U.S. Pat. Nos. 7,998,423 to Boorse et al.; 9,017,626 to Tang et al.; 9,242,238 to Mohanan et al.; and 9,352,307 to Stiebels et al., which are incorporated herein by reference. Diesel Oxidation Catalyst (DOC) Composition In another aspect is provided a DOC catalyst composition comprising a refractory metal oxide comprising a thermally stable sulfate as disclosed herein. In some embodiments, the refractory metal oxide comprises titania. Various DOC compositions can be for use in treating the exhaust of diesel engines in order to convert both hydrocarbon (HC) and carbon monoxide (CO) gaseous pollutants by catalyzing the oxidation of these pollutants to carbon dioxide and water. In some embodiments, oxidation catalysts such as DOCs, comprise one or more platinum group metal (PGM) components supported on a porous material, such as a refractory metal oxide as described herein. As used herein, "PGM" refers to a platinum group metal. Platinum group metals include platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), osmium (Os), iridium (Ir), and mixtures thereof. As used herein "PGM component" refers to a platinum group metal, or a compound or complex thereof, which, upon calcination or use of the catalyst, decomposes or otherwise converts to a catalytically active form, usually the metal or the respective metal oxide. PGM components useful in the disclosed DOC compositions include any component that includes a PGM, such as platinum (Pt), palladium (Pd), ruthenium (Ru), rhodium (Rh), osmium (Os), iridium (Ir), and/or gold (Au). For example, the PGM may be in metallic form, with zero valence, or the PGM may be in an oxide form. The PGM components can include the PGM in any valence state. The terms "platinum (Pt) component," "rhodium (Rh) component," "palladium (Pd) component," "iridium (Ir) component," "ruthenium (Ru) component," and the like refer to the respective platinum group metal compound, complex, or the like which, upon calcination or use of the catalyst, decomposes or otherwise converts to a catalytically active form, e.g., the metal or the metal oxide. For representative PGM-containing catalyst compositions, see, for example, U.S. Pat. No.6,764,665 to Deeba, which is hereby incorporated by reference in its entirety. Lean NOx Trap Catalyst Compositions In another aspect is provided a Lean NOx Trap (LNT) catalyst composition comprising a refractory metal oxide comprising a thermally stable sulfate as disclosed herein. In some embodiments, the refractory metal oxide comprises titania. Lean NO _x trap (LNT) catalysts contain NO _x adsorbent components that trap NO _x under certain exhaust conditions. For example, the NOx adsorbent components can comprise alkaline earth elements, e.g., including alkaline earth metal oxides and carbonates, such as oxides of Mg, Ca, Sr, and/or Ba. Other LNT catalysts can contain rare earth metal oxides as NOx adsorbent components, such as oxides of Ce, La, Pr, and/or Nd. LNT catalysts further contain a platinum group metal component (PGM) such as platinum dispersed on a refractory metal oxide (e.g., titania) support for catalytic NO _x oxidation and reduction. The LNT catalyst operates under cyclic lean (trapping mode) and rich (regeneration mode) exhaust conditions. Under lean conditions, the LNT catalyst traps and stores NOx as an inorganic nitrate (for example, where the NOx adsorbent component is BaO or BaCO ₃ , it is converted to Ba(NO3)2) upon reaction with ("trapping") of NOx. The NOx adsorbent component then releases the trapped NO _x and the PGM component reduces the NO _x to N ₂ under stoichiometric or transient rich engine operating conditions, or under lean engine operation with external fuel injected in the exhaust to induce rich conditions. For representative LNT catalyst compositions, see, for example, United States Patent Application Publication No. 2009/0320457 to Wan, which is hereby incorporated by reference in its entirety. For additional examples of LNT catalyst compositions, see, for example U.S. Patent Nos. 5,750,082 to Hephurn et al.; 8,105,559 to Melville et al.; 8,475,752 to Wan et al.; 8,592,337 to Holgendorff et al.; 9,114,385 to Briskley et al.; 9,486,791 to Swallow et al.; 9,610,564 to Xue et al.; 9,662,611 to Wan et al.; U.S. Patent Application Nos. 2002/0077247 to Bender et al.; 2011/0305615 to Hilgendorff et al.; 2015/0157982 to Rajaram et al.; 2015/0158019 to Rajaram et al.; 2016/0228852 to Biberger et al.; and International Patent Application WO 2016/141142 to Grubert et al., each of which is incorporated by reference in their entireties. Coating Compositions Coating compositions comprising the various catalyst compositions as disclosed herein may be prepared using a binder, for example, a ZrO ₂ binder derived from a suitable precursor such as zirconyl acetate or any other suitable zirconium precursor such as zirconyl nitrate. Zirconia binder provides a coating that remains homogeneous and intact after thermal aging, for example, when the catalyst is exposed to high temperatures of at least about 600 °C, for example, about 800 °C, and higher water vapor environments of about 5% or more. Other potentially suitable binders include, but are not limited to, alumina and silica. Alumina binders include aluminum oxides, aluminum hydroxides and aluminum oxyhydroxides. Aluminum salts and colloidal forms of alumina many also be used. Silica binders include various forms of SiO2, including silicates and colloidal silica. Binder compositions may include any combination of zirconia, alumina and silica. Other exemplary binders include boehemite, gamma-alumina, or delta/theta alumina, as well as silica sol. When present, the binder can be used in an amount ranging from about 1 wt% - 5 wt% of the total washcoat loading. Alternatively, the binder can be zirconia-based or silica-based, for example zirconium acetate, zirconia sol or silica sol. When present, the alumina binder can be used in an amount ranging from about 0.05 g/in ³ to about 1 g/in ³ . Catalytic Articles In another aspect is provided a catalyst article comprising a substrate having an inlet end and an outlet end defining an overall length, and a catalytic coating comprising one or more washcoats disposed on at least a portion thereof, wherein at least one of said washcoats comprises a catalyst composition as disclosed herein (e.g., an SCR, LNT, or DOC catalyst composition). Each of the article components is further described herein below. Substrate In some embodiments, a washcoat comprising a catalyst composition as disclosed herein is disposed on a substrate to form a catalytic article. Catalytic articles comprising the substrates are generally employed as part of an exhaust gas treatment system (e.g., catalyst articles including, but not limited to, articles including the oxidation catalyst compositions disclosed herein). Useful substrates are 3-dimensional, having a length and a diameter and a volume, similar to a cylinder. The shape does not have to conform to a cylinder. The length is an axial length defined by an inlet end and an outlet end. According to one or more embodiments, the substrate for the disclosed composition(s) may be constructed of any material that can be used for preparing automotive catalysts and may comprise a metal or ceramic honeycomb structure. The substrate may provide a plurality of wall surfaces upon which the washcoat composition is applied and adhered, thereby acting as a substrate for the catalyst composition. Ceramic substrates may be made of any suitable refractory material, e.g., cordierite, cordierite-α-alumina, aluminum titanate, silicon titanate, silicon carbide, silicon nitride, zircon mullite, spodumene, alumina-silica-magnesia, zircon silicate, sillimanite, a magnesium silicate, zircon, petalite, α-alumina, an aluminosilicate, and/or the like. Substrates may also be metallic, comprising one or more metals or metal alloys. A metallic substrate may include any metallic substrate, such as those with openings or "punch-outs" in the channel walls. The metallic substrates may be employed in various shapes such as pellets, compressed metallic fibers, corrugated sheet or monolithic foam. Specific examples of metallic substrates include heat-resistant, base-metal alloys, especially those in which iron is a substantial or major component. Such alloys may contain one or more of nickel, chromium, and aluminum, and the total of these metals may comprise at least about 15 wt% (weight percent) of the alloy, for instance, from about 10 wt% to about 25 wt% chromium, from about 1 wt% to about 8 wt.% of aluminum, and from 0 wt% to about 20 wt% of nickel, in each case based on the weight of the substrate. Examples of metallic substrates include those having straight channels; those having protruding blades along the axial channels to disrupt gas flow and to open communication of gas flow between channels; and those having blades and holes to enhance gas transport between channels allowing for radial gas transport throughout the monolith. Any suitable substrate for the catalytic articles disclosed herein may be employed, such as a monolithic substrate of the type having fine, parallel gas flow passages extending there through from an inlet or an outlet face of the substrate such that passages are open to fluid flow there through ("flow-through substrate"). Another suitable substrate is of the type have a plurality of fine, substantially parallel gas flow passages extending along the longitudinal axis of the substrate where each passage is blocked at one end of the substrate body, with alternate passages blocked at opposite end-faces ("wall-flow filter"). Flow- through and wall-flow substrates are also taught, for example, in International Application Publication No. WO 2016/070090, which is incorporated herein by reference in its entirety. In some embodiments, the catalyst substrate comprises a honeycomb substrate in the form of a wall-flow filter or a flow-through substrate. In some embodiments, the substrate is a wall-flow filter. In some embodiments, the substrate is a flow-through substrate. Flow-Through Substrates In some embodiments, the substrate is a flow-through substrate (e.g., monolithic substrate, including a flow-through honeycomb monolithic substrate). Flow-through substrates have fine, parallel gas flow passages extending from an inlet end to an outlet end of the substrate such that passages are open to fluid flow. The passages, which are straight paths from their fluid inlet to their fluid outlet, are defined by walls on or in which a catalytic coating is disposed so that gases flowing through the passages contact the catalytic material. The flow passages of the flow-through substrate are thin-walled channels, which can be of any suitable cross-sectional shape and size such as trapezoidal, rectangular, square, sinusoidal, hexagonal, oval, circular, etc. The flow- through substrate can be ceramic or metallic as described above. Flow-through substrates can, for example, have a volume ranging from about 50 in ³ to about 1200 in ³ , a cell density (inlet openings) ranging from about 60 cells per square inch (cpsi) to about 500 cpsi or up to about 900 cpsi, for example from about 200 cpsi to about 400 cpsi and a wall thickness of from about 50 microns to about 200 microns or about 400 microns. Wall-Flow Filter Substrates In some embodiments, the substrate is a wall-flow filter, which generally has a plurality of fine, substantially parallel gas flow passages extending along the longitudinal axis of the substrate. In some embodiments, each passage is blocked at one end of the substrate body, with alternate passages blocked at opposite end-faces. Such monolithic wall- flow filter substrates may contain up to about 900 or more flow passages (or "cells") per square inch of cross-section, although far fewer may be used. For example, the substrate may have from about 7 cpsi to 600 cpsi, e.g., from about 100 cpsi to 400 cpsi, cells per square inch ("cpsi"). The cells can have cross-sections that are rectangular, square, circular, oval, triangular, hexagonal, or are of other polygonal shapes. The wall-flow filter substrate can be ceramic or metallic as described above. Referring to FIG. 1, the exemplary wall-flow filter substrate has a cylindrical shape and a cylindrical outer surface having a diameter D and an axial length L. A cross-section view of a monolithic wall-flow filter substrate section is illustrated in FIG. 2, showing alternating plugged and open passages (cells). Blocked or plugged ends 100 alternate with open passages 101, with each opposing end open and blocked, respectively. The filter has an inlet end 102 and outlet end 103. The arrows crossing porous cell walls 104 represent exhaust gas flow entering the open cell ends, diffusion through the porous cell walls 104 and exiting the open outlet cell ends. Plugged ends 100 prevent gas flow and encourage diffusion through the cell walls. Each cell wall will have an inlet side 104a and outlet side 104b. The passages are enclosed by the cell walls. The wall-flow filter article substrate may have a volume ranging, for instance, from about 50 cm ³ , about 100 in ³ , about 200 in ³ , about 300 in ³ , about 400 in ³ , about 500 in ³ , about 600 in ³ , about 700 in ³ , about 800 in ³ , about 900 in ³ or about 1000 in ³ to about 1500 in ³ , about 2000 in ³ , about 2500 in ³ , about 3000 in ³ , about 3500 in ³ , about 4000 in ³ , about 4500 in ³ or about 5000 in ³ . Wall-flow filter substrates may have a wall thickness from about 50 microns to about 2000 microns, for example from about 50 microns to about 450 microns or from about 150 microns to about 400 microns. The walls of the wall-flow filter are porous and may have a wall porosity of at least about 40% or at least about 50% with an average pore diameter of at least about 10 microns prior to disposition of the functional coating. For instance, the wall-flow filter article substrate, in some embodiments, have a porosity of ≥ 40%, ≥ 50%, ≥ 60%, ≥ 65%, or ≥ 70%. For instance, the wall-flow filter article substrate will have a wall porosity ranging from about 50%, about 60%, about 65% or about 70%, to about 75%, and an average pore diameter of from about 10 microns, or about 20 microns, to about 30 microns, or about 40 microns prior to disposition of a catalytic coating. The terms "wall porosity" and "substrate porosity" mean the same thing and are interchangeable. Porosity is the ratio of void volume (or pore volume) divided by the total volume of a substrate material. Pore size and pore size distribution may be determined by Hg porosimetry measurement. Substrate Coating Process To produce catalyst articles of the present disclosure, a substrate as described herein is coated with a catalyst composition as disclosed herein. The coatings are "catalytic coating compositions" or "catalytic coatings." A "catalyst composition" and a "catalytic coating composition" are synonymous. In some embodiments, the catalyst composition is prepared and coated on a substrate as described herein. This method can comprise mixing the catalyst composition (or one or more components of the catalyst composition) as generally disclosed herein with a solvent (e.g., water) to form a slurry for purposes of coating a catalyst substrate. In addition to the catalyst composition, the slurry may optionally contain various additional components In some embodiments additional components include but are not limited to, binders as described herein above, additives to control, e.g., pH and viscosity of the slurry. Additional components can include hydrocarbon (HC) storage components (e.g., zeolites), associative thickeners, and/or surfactants (including anionic, cationic, non-ionic or amphoteric surfactants). A pH range for the slurry may be from about 3 to about 6. Addition of acidic or basic species to the slurry can be carried out to adjust the pH accordingly. For example, in some embodiments, the pH of the slurry is adjusted by the addition of aqueous acetic acid. The slurry can be milled to reduced particle size and to enhance mixing of the particles and formation of a homogenous material. The milling can be accomplished in a ball mill, continuous mill, or other similar equipment, and the solids content of the slurry may be, e.g., from about 20 wt% to 60 wt%, such as from about 20 wt% to 40 wt%. In one embodiment, the post-milling slurry is characterized by a D90 particle size ranging from about 1 micron to about 40 microns, such as from about 2 microns to about 20 microns, further for example, from about 4 microns to about 15 microns. Washcoats The present catalyst compositions may be applied in the form of one or more washcoats containing the catalyst composition as disclosed herein. A washcoat is formed by preparing a slurry containing a certain solids content (e.g., from about 10% to about 60% by weight) of catalyst composition (or one or more components of the catalyst composition) in a liquid vehicle, which is then applied to a substrate using any suitable washcoat technique and dried and calcined to provide a coating layer. If multiple coatings are applied, the substrate is dried and /or calcined after each washcoat is applied and/or after the number of desired multiple washcoats are applied. In one or more embodiments, the catalytic material(s) are applied to the substrate as a washcoat. A washcoat can be formed by preparing a slurry containing a certain solids content (e.g., from 30% to 90% by weight) of catalyst material in a liquid vehicle, which is then coated onto the substrate (or substrates) and dried to provide a washcoat layer. To coat the wall flow substrates with the catalyst material of one or more embodiments, the substrates can be immersed vertically in a portion of the catalyst slurry such that the top of the substrate is located just above the surface of the slurry. In this manner, slurry contacts the inlet face of each honeycomb wall, but is prevented from contacting the outlet face of each wall The sample is left in the slurry for about 30 seconds The substrate is removed from the slurry, and excess slurry is removed from the wall flow substrate first by allowing it to drain from the channels, then by blowing with compressed air (against the direction of slurry penetration), and then by pulling a vacuum from the direction of slurry penetration. By using this technique, the catalyst slurry permeates the walls of the substrate, yet the pores are not occluded to the extent that undue back pressure will build up in the finished substrate. As used herein, the term "permeate" when used to describe the dispersion of the catalyst slurry on the substrate, means that the catalyst composition is dispersed throughout the wall of the substrate. Thereafter, the coated substrate is dried at an elevated temperature (e.g., ranging from about 100 °C to about 150 °C) for a period of time (e.g., from about 1 hour to about 3 hours) and then calcined by heating, e.g., ranging from about 400 °C to about 600 °C, for about 10 minutes to about 3 hours. Following drying and calcining, the final washcoat coating layer can be viewed as essentially solvent-free. After calcining, the catalyst loading can be determined through calculation of the difference in coated and uncoated weights of the substrate. In some embodiments, the catalyst loading can be modified by altering the slurry rheology. In addition, the coating/drying/calcining process can be repeated as needed to build the coating to the desired loading level or thickness. After calcining, the catalyst loading obtained by the above described washcoat technique can be determined through calculation of the difference in coated and uncoated weights of the substrate. In some embodiments, the catalyst loading can be modified by altering the slurry rheology. In addition, the coating/drying/calcining process to generate a washcoat layer (coating layer) can be repeated as needed to build the coating to the desired loading level or thickness, meaning more than one washcoat may be applied. Catalyst Layers and Zones In some embodiments, the present catalyst article may include the use of one or more washcoat layers and combinations of one or more washcoat layers, where at least one washcoat layer comprises a catalyst composition as disclosed herein. The catalyst article may comprise one or more thin, adherent coating layers (e.g., washcoats) disposed on and in adherence to least a portion of a substrate. The entire coating comprises the individual "coating layers". Catalytic materials may be present on the inlet side of the substrate wall alone, the outlet side alone, both the inlet and outlet sides, or the wall itself may consist all, or in part, of the catalytic material. The catalytic materials, in the form of one or more washcoat layers may be on the substrate wall surfaces and/or in the pores of the substrate walls, that is "in" and/or "on" the substrate walls. Thus, the phrase "a washcoat disposed on the substrate" means on any surface, for example on a wall surface and/or on a pore surface. The washcoat(s) can be applied such that different coating layers may be in direct contact with the substrate. Alternatively, one or more "undercoats" may be present, so that at least a portion of a catalytic coating layer or coating layers are not in direct contact with the substrate (e.g., but rather, are in contact with the undercoat). One or more "overcoats" may also be present, so that at least a portion of the coating layer or layers are not directly exposed to a gaseous stream or atmosphere (e.g., but rather, are in contact with the overcoat). Washcoats may be present in many layered arrangements, for example, in a top coating layer over a bottom coating layer, or in a bottom layer (e.g., in direct contact with the substrate). Any one layer may extend the entire axial length of the substrate, for instance a bottom layer may extend the entire axial length of the substrate and a top layer may also extend the entire axial length of the substrate over the bottom layer. Each of the top and bottom layers may extend from either the inlet or outlet end. For example, both bottom and top coating layers may extend from the same substrate end where the top layer partially or completely overlays the bottom layer and where the bottom layer extends a partial or full length of the substrate and where the top layer extends a partial or full length of the substrate. Alternatively, a top layer may overlay a portion of a bottom layer. For example, a bottom layer may extend the entire length of the substrate and the top layer may extend about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80% or about 90% of the substrate length, from either the inlet or outlet end. Alternatively, a bottom layer may extend about 10%, about 15%, about 25%, about 30%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, about 80%, about 85% or about 95% of the substrate length from either the inlet end or outlet end and a top layer may extend about 10%, about 15%, about 25%, about 30%, about 40%, about 45%, about 50%, about 55%, about 60%, about 65%, about 70%, about 75%, about 80%, about 85% or about 95% of the substrate length from either the inlet end of outlet end, wherein at least a portion of the top layer overlays the bottom layer. This "overlay" zone may for example extend from about 5% to about 80% of the substrate length, for example about 5%, about 10%, about 20%, about 30%, about 40%, about 50%, about 60% or about 70% of the substrate length The catalytic coating may be "zoned," comprising zoned catalytic layers, that is, where the catalytic coating contains varying compositions across the axial length of the substrate. This may also be described as "laterally zoned". For example, a layer may extend from the inlet end towards the outlet end extending about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, or about 90% of the substrate length. Another layer may extend from the outlet end towards the inlet end extending about 10%, about 20%, about 30%, about 40%, about 50%, about 60%, about 70%, about 80%, or about 90% of the substrate length. Different coating layers may be adjacent to each other and not overlay each other. Alternatively, different layers may overlay a portion of each other, providing a third "middle" zone. The middle zone may, for example, extend from about 5% to about 80% of the substrate length, for example about 5%, about 10%, about 20%, about 30%, about 40%, about 50%, about 60% or about 70% of the substrate length. Zones of the present disclosure are defined by the relationship of coating layers. With respect to different coating layers, there are a number of possible zoning configurations. For example, there may be an upstream zone and a downstream zone, there may be an upstream zone, a middle zone and a downstream zone, or there may be four different zones, etc. Where two layers are adjacent and do not overlap, there are upstream and downstream zones. Where two layers overlap to a certain degree, there are upstream, downstream, and middle zones. Where for example, a coating layer extends the entire length of the substrate and a different coating layer extends from the outlet end for a certain length, and overlays a portion of the first coating layer, there are upstream and downstream zones. FIGs. 3A, 3B, and 3C show some possible non-limiting coating layer configurations with two coating layers. In some embodiments, substrate walls 200 onto which coating layers 201 and 202 are disposed are shown. This is a simplified illustration, and in the case of a porous wall-flow substrate, the pores and coatings in adherence to pore walls are not shown, and plugged ends are not shown. In FIG. 3A, coating layers 201 and 202 each extends the entire length of the substrate, with top layer 201 overlaying bottom layer 202. The substrate of FIG.3A does not contain a zoned coating configuration. FIG.3B illsutrates a zoned configuration having a coating layer 202 which extends from the outlet end 103 about 50% of the substrate length to form a downstream zone 204, and a coating layer 201 which extends from the inlet end 102 about 50% of the substrate length, providing an upstream zone 203. In FIG. 3C, bottom coating layer 202 extends from the outlet about 50% of the substrate length and top coating layer 201 extends from the inlet greater than 50% of the length and overlays a portion of layer 202, providing an upstream zone 203, a middle overlay zone 205 and a downstream zone 204. In any of the zoned arrangements described above, it is noted that the washcoat zones, where adjacent, may be in contact (e.g., abutting), or may be separated by a gap (not shown). FIGs. 3A, 3B, and 3C may be useful to illustrate catalyst composition coatings on a wall-through substrate or a flow-through substrate. Catalyst Loading Loading of the present catalytic coatings on a substrate will depend on substrate properties such as porosity and wall thickness. In some embodiments, wall-flow filter catalyst loading will be lower than catalyst loadings on a flow-through substrate. Catalyzed wall-flow filters are disclosed, for instance, in U.S. Pat. No. 7,229,597, which is incorporated herein by reference in its entirety. In describing the quantity of washcoat or catalytic metal components or other components of the composition, it is convenient to use units of weight of component per unit volume of catalyst substrate. Therefore, the units, grams per cubic inch ("g/in ³ ") and grams per cubic foot ("g/ft ³ "), are used herein to mean the weight of a component per volume of the substrate, including the volume of void spaces of the substrate. Other units of weight per volume such as g/L are also sometimes used. Concentration of a catalyst composition, or any other component, on a substrate refers to concentration per any one three-dimensional section or zone, for instance any cross-section of a substrate or of the entire substrate. Exhaust Gas Treatment Systems In a further aspect is provided an exhaust gas treatment system comprising a catalyst article as disclosed herein, wherein the catalyst article is downstream of and in fluid communication with an internal combustion engine. The engine can be, e.g., a diesel engine which operates at combustion conditions with air in excess of that required for stoichiometric combustion, e.g., lean conditions. In other embodiments, the engine can be a gasoline engine (e.g., a lean burn gasoline engine) or an engine associated with a stationary source (e.g., electricity generators or pumping stations). Exhaust gas treatment systems generally contain more than one catalytic article positioned downstream from the engine in fluid communication with the exhaust gas stream. A system may contain, for instance, a catalyst article as disclosed herein (e.g., an SCR, LNT, or DOC), and one or more articles including a reductant injector, a soot filter, or an ammonia oxidation catalyst (AMOx). An article containing a reductant injector is a reduction article. A reduction system includes a reductant injector and/or a pump and/or a reservoir, etc. The present treatment system may further comprise a soot filter and/or an ammonia oxidation catalyst. A soot filter may be uncatalyzed or may be catalyzed (CSF). For instance, the present treatment system may comprise, from upstream to downstream – an article containing a DOC, a CSF, a urea _injector, a SCR article and an article containing an AMOx. A lean NOx trap (LNT) may also be included. The relative placement of the various catalytic components present within the emission treatment system can vary. In the present exhaust gas treatment systems and methods, the exhaust gas stream is received into the article(s) or treatment system by entering the upstream end and exiting the downstream end. The inlet end of a substrate or article is synonymous with the "upstream" end or "front" end. The outlet end is synonymous with the "downstream" end or "rear" end. The treatment system is, e.g., downstream of and in fluid communication with an internal combustion engine. One example emission treatment system is illustrated in FIG. 4, which depicts a schematic representation of an emission treatment system 20. As shown, the emission treatment system can include a plurality of catalyst components in series downstream of an engine 22, such as a lean burn engine. At least one of the catalyst components will comprise a catalyst composition of the disclosure as set forth herein (e.g., a DOC, an SCR, an LNT, or a combination thereof). The catalyst compositions of the disclosure could be combined with numerous additional catalyst materials and could be placed at various positions in comparison to the additional catalyst materials. FIG. 4 illustrates five catalyst components, 24, 26, 28, 30, 32 in series; however, the total number of catalyst components can vary and five components is merely one non-limiting example. Without limitation, Table 1 presents various exhaust gas treatment system configurations of one or more embodiments. It is noted that each catalyst is connected to the next catalyst via exhaust conduits such that the engine is upstream of catalyst A, which is upstream of catalyst B, which is upstream of catalyst C, which is upstream of catalyst D, which is upstream of catalyst E (when present). The reference to Components A- E in the table can be cross-referenced with the same designations in FIG.4. The LNT catalyst noted in Table 1 can be any catalyst conventionally used as a NO trap, and may comprise NO _x -adsorber compositions that include base metal oxides (BaO, MgO, CeO2, and the like) and a platinum group metal for catalytic NO oxidation and ^{reduction (e.g., Pt} and Rh). The LNT catalyst may comprise a refractory metal oxide comprising a thermally stable sulfate as disclosed herein. The LT-NA catalyst noted in Table 1 can be any catalyst that can adsorb NOx (e.g., NO or NO2) at low temperatures (<250°C) and release it to the gas stream at high temperatures (>250°C). The released NOx is generally converted to N2 and H2O over a ^{down-stream SCR or SCRoF} catalyst. In some embodiments, a LT-NA catalyst comprises Pd-promoted zeolites or Pd-promoted refractory metal oxides. The LT-NA catalyst may comprise a refractory metal oxide comprising a thermally stable sulfate as disclosed herein. Reference to SCR in the table refers to an SCR catalyst. Reference to SCRoF (or SCR on filter) refers to a particulate or soot filter (e.g., a wall-flow filter), which can include an SCR catalyst composition. The SCR catalyst may comprise a refractory metal oxide comprising a thermally stable sulfate as disclosed herein. Reference to AMOx in the table refers to an ammonia oxidation catalyst, which can be provided downstream of the catalyst of one or more embodiments of the disclosure to remove any slipped ammonia from the exhaust gas treatment system. In some embodiments, the AMOx catalyst may comprise a PGM component. In one or more embodiments, the AMOx catalyst may comprise a bottom coat with PGM and a top coat with SCR functionality. The AMOx catalyst may comprise a refractory metal oxide comprising a thermally stable sulfate as disclosed herein. As recognized by one skilled in the art, in the configurations listed in Table 1, any one or more of components A, B, C, D, or E can be disposed on a particulate filter, such as a wall flow filter, or on a flow-through honeycomb substrate. In one or more embodiments, an engine exhaust system comprises one or more catalyst compositions mounted in a position near the engine (in a close-coupled position, CC), with additional catalyst compositions in a position underneath the vehicle body (in an underfloor position, UF). In one or more embodiments, the exhaust gas treatment system may further comprise a urea injection component. Table 1. Possible exhaust gas treatment system configurations

Method for Reducing the Emission of Sulfur Oxides In another aspect is provided a method of reducing the emission of sulfur oxides during the calcination of a residual sulfate-containing refractory metal oxide support by sequestering the residual sulfate in the form of a thermally stable sulfate, the method comprising: contacting the residual sulfate-containing refractory metal oxide with a water soluble, sulfur-free, metal salt to form a mixture, drying the mixture to form a dried material; and calcining the dried material to form a catalyst composition comprising the refractory metal oxide and a thermally stable metal sulfate comprising the metal of the metal salt. Each of the components and steps of the process are as described herein above. As used herein, the term "sequestering the residual sulfate" means that any residual sulfate present in the refractory metal oxide undergoes reaction with the metal ions from the water soluble sulfate-forming component to form a new thermally stable sulfate as disclosed herein above. As used herein, the term "contacting" means that the residual sulfate-containing refractory metal oxide and the water soluble metal salt are brought together in a manner that allows chemical reaction between the residual sulfate and the metal ions provided by the metal salt. Contacting may comprise any known means of allowing such reaction, for example, in a slurry, and/or by impregnation, adsorption, incipient wetness, or the like, as disclosed herein above. As used herein, the term "reducing the emission of sulfur oxides" means that emission of sulfur oxides during calcination is lower relative to the emission of sulfur oxides from a residual sulfate-containing refractory metal oxide which has not been contacted with the water soluble, sulfate-forming component according to the disclosed method. In some embodiments, the emission of sulfur oxides is reduced by at least about 75% relative to the emission of sulfur oxides from a residual sulfate-containing refractory metal oxide which has not been contacted with the water soluble, sulfate-forming component. In some embodiments, the emission is reduced by at least about 75%, at least about 80%, at least about 85%, at least about 90%, at least about 95%, at least about 99%, or even 100%. The sulfur oxide emission may be quantified according to methods known in the art, such as thermogravimetric analysis (TGA) and mass spectrometry, either alone or in combination. EXAMPLES The present disclosure is more fully illustrated by the following examples, which are set forth to illustrate the present disclosure and is not to be construed as limiting thereof. Unless otherwise noted, all parts and percentages are by weight, and all weight percentages are expressed on a dry basis, meaning excluding water content, unless otherwise indicated. Example 1. TiO ₂ -10% WO ₃ (Comparative). A commercially available sample of 10% tungsten (VI) oxide-doped titania (TiO2- 10% WO ₃ ) containing about 1% residual sulfate (SO ₄ ^2- ) was dried at 100 °C. The dried sample was heated in air over a range of temperature from ambient to 800 °C in a thermogravimetric analyzer (TGA) equipped with a mass spectrometer configured to measure evolved gases. The results are provided in Figures 5 to 7, which demonstrated that SOx was released from this support material at temperatures above about 650 °C (e.g., as shown in percent of original sample weight vs. temperature in Fig. 5; ion abundance vs. temperature in Figs 6 and 7 for m/z=64 and 46 respectively) Example 2. TiO ₂ -10% WO ₃ plus Barium (Present disclosure). A commercially available sample of titania-WO3 containing about 1% residual sulfate was impregnated with barium acetate. Specifically, titania containing 10% WO ₃ by weight (DT-52; Millenium; 13.95 g) was impregnated by incipient wetness with a solution of Ba(OAc)2 (2.91 g, 11 mmol) in 6 g of water. The impregnated material was dried at 100 °C for 2 hours. The elemental analysis is provided in Table 2. Table 2. Elemental analysis of Example 2 The dried sample was heated in a TGA as in Example 1. The results are provided in Figures 5 to 7, which demonstrated that no SO _x was released from this support material up to the temperature limit of 800 °C (e.g., as shown in percent of original sample weight vs. temperature in Fig. 5; ion abundance vs. temperature in Figs. 6 and 7 for m/z=64 and 46, respectively). Example 3. TiO2-10% WO3 plus Cerium (Present disclosure). A commercially available sample of titania-WO ₃ containing about 1% residual sulfate was impregnated with cerium nitrate via an incipient wetness technique and dried at 100 °C. Specifically, titania containing 10% WO3 by weight (DT-52; Millenium; 13.95 g) was impregnated by incipient wetness with a solution of Ce(NO ₃ ) ₃ hexahydrate (6.15 g, 14 mmol) in 6 g of water. The impregnated material was dried at 100 °C for 2 hours. The elemental analysis is provided in Table 3. Table 3. Elemental analysis of Example 3 The dried sample was heated in a TGA as in Example 1. The results are provided in Figures 5 to 7, which demonstrated that SO _x was only released from this support material above about 750 °C (e.g., as shown in percent of original sample weight vs. temperature in Fig.5; ion abundance vs. temperature in Figs.6 and 7 for m/z=64 and 46, respectively). Example 4A. Vanadium-impregnated TiO ₂ -10% WO ₃ without Barium (reference) A sample of reference Example 1 was re-slurried and 2.5% V2O5 was added as a vanadium oxalate solution. The vanadium oxalate solution was free of any sulfate. The resulting slurry was dried at 100 °C for 2 hours, and then calcined in air at 450 °C for 1 hour to provide reference Example 4A (V/TiO ₂ /WO ₃ ). Example 4B. Vanadium-impregnated TiO2-10% WO3 with Barium (Present disclosure) A sample of inventive Example 2 was re-slurried and 2.5% V2O5 was added as a vanadium oxalate solution. The vanadium oxalate solution was free of any sulfate. The resulting slurry was dried at 100 °C for 2 hours, and then calcined in air at 450 °C for 1 hour _{to provide inventive} ^{Example 4B (V/TiO} ₂ ^/WO _3/ ^Ba). Example 5. IR Characterization of Vanadium-impregnated Examples 4A and 4B. Sulfur species (e.g., sulfate) were identified by monitoring the S-O bond vibrations by diffuse reflectance Fourier transform infrared (DRIFT) spectroscopy. The IR characterization was performed on a Varian 7000 FTIR spectrometer equipped with an MCT detector and a Pike Technology high-temperature environmental chamber with a KBr window. Spectrum collection was performed under diffuse reflection mode. The samples were ground into fine powders with a mortar and pestle, and then filled into the sample cup. The sample powder was kept in the Pike reactor under 20% O2/Ar (70 ml/min) all the time. The first IR spectrum was collected at 30 ^o C after flowing 20% O2/Ar for 15 minutes to remove gas phase water vapor. Then the sample was dehydrated in 20% O ₂ /Ar at 400 ^o C for 1 hour with a ramp rate of 20 ^o C/min. IR spectra were collected after dehydration and cooling step to 30 ^o C. All spectra were converted to absorbance by using a background spectrum collected on a KBr reference sample in Argon. Results are provided in Figure 8, which demonstrated that the di-sulfate peaks were associated with the Ba-SO4 species and some residual sulfate in the TiO2, while the mono- sulfate species were almost entirely associated with the residual sulfate in the TiO ₂ . ^{Accordingly, the} DRIFTS spectroscopy confirmed that the Ba in the catalyst prepared _{using Ba acetate (Example} 4B) was present as BaSO ⁴ . Specifically, the data demonstrated ^{that extra di-sulfate surface species} _{were trapped by Ba in Example 4B, compared to only} mono-sulfate species in the reference (Example 4A). These peaks were integrated to provide a relative measure of the two species. Table 4 below summarizes the total residual sulfate on the catalyst, along with the ratio of di- to mono- sulfate species. Table 4. Bulk sulfate content and ratio of bi to mono sulfate species While the total amount of sulfate in both samples was similar (1.16 vs 1.25%), Example 4B showed a significantly higher ratio of di-sulfate to mono-sulfate, indicative of bonding between the Ba and the residual surface sulfate. Example 6. SCR Catalyst Activity Example 4A and 4B powders were evaluated for selective catalytic reduction (SCR) activity using a powder reactor with a feed gas of 500 ppm NO and NH3, 5% H2O and 10% O ₂ . The first run target temperatures were 175 °C, 200 °C, 250 °C, 300 °C, and 450 °C. Only data from the 250 °C point was reported here. After the 1st run the samples were heat treated at 550 °C for 1 hour, and the cycle repeated with additional test temperatures of 500 °C and 550 °C. The third test cycle repeated the 2nd cycle, but without the 550 °C heat treatment. The results from each run for the 250 °C target temperature are provided in Figure 9, which demonstrated very similar performance for NO _x reduction for the reference and inventive embodiment for the first run. After the calcination at 550 °C, the Ba- containing sample showed significantly improved performance (runs 2 and 3) relative to the reference example 4A.