The present invention relates to renewable marine fuel compositions, in particular to hydrotreated tall oil pitch which is suitable for marine fuel. The invention relates also to methods for producing renewable marine fuel compositions comprising hydrotreated tall oil pitch.

BACKGROUND

According to IMO's strategy the GHG emissions from global shipping should be reduced at least 50% by 2050 compared to 2008 level. This challenging target requires besides enhanced energy efficiency of the vessels also renewable fuel alternatives. Today the total marine fuel pool is ca 300 million metric ton. If up to 40% of the GHG reduction target for new vessels can be achieved through energy efficiency improvements, there will still be a need for alternative solutions.

US20140291200A1 discloses a process for the production of diesel fuel bases suitable for marine fuel comprising a sulfur content that is less than 100 ppm from a feedstock that is obtained from a renewable source. The method comprises bringing the feedstock into contact with a fixed-bed hydrotreatment catalyst for producing an effluent that comprises a gaseous fraction comprising hydrogen and a hydrocarbonbased liquid fraction followed by selective hydroisomerization. Feedstocks suitable for the method must contain sulfur and nitrogen less than 500 ppm, and aromatic compound contents that are less than 5% by weight. Although the method disclosed therein is suitable for producing marine fuels from renewable sources, it is not suitable for renewable feedstocks comprising significant amounts of sulphur.

Accordingly, there is still need for further methods for producing marine fuels.

SUMMARY

The following presents a simplified summary in order to provide a basic understanding of some aspects of various embodiments of the invention. The summary is not an extensive overview of the invention. It is neither intended to identify key nor critical elements of the invention, nor to delineate the scope of the invention. The following summary merely presents some concepts of the invention in a simplified form as a prelude to a more detailed description of exemplifying embodiments of the invention.

It was observed in the present invention that when a feedstock comprising tall oil pitch (TOP) was subjected to certain hydrotreatment reaction conditions, its acidity and oxygen content could be reduced. The hydrotreated TOP was found to be suitable for marine fuel as such. Alternatively, it could me admixed with further renewable or fossil marine fuel components.

In accordance with the invention, there is provided a new method for producing marine fuel component, the method comprising the following steps: a) providing a feedstock comprising tall oil pitch, b) subjecting the feedstock to hydrotreatment reaction conditions to produce a hydrotreated tall oil pitch, wherein the hydrotreatment reaction conditions comprise pressure between 30 barg and 200 barg and temperature between 300 °C and 350 °C, and wherein the subjecting is in the presence of hydrogen stream and one or more hydrotreatment catalysts, and c) fractionating the hydrotreated tall oil pitch to a first fraction and to a second fraction, wherein the second fraction is the marine fuel component.

In accordance with the invention, there is also provided a new use of hydrotreated tall oil pitch obtainable by a method according to any one of claims 1 -16 as a marine fuel component.

In accordance with the invention, there is also provided a new marine fuel obtainable by a method according to any one of claims 1 -16.

A number of exemplifying and non-limiting embodiments of the invention are described in accompanied dependent claims.

Various exemplifying and non-limiting embodiments of the invention and to methods of operation, together with additional objects and advantages thereof, are best understood from the following description of specific exemplifying embodiments when read in connection with the accompanying figures.

The verbs “to comprise” and “to include” are used in this document as open limitations that neither exclude nor require the existence of also unrecited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", i.e. a singular form, throughout this document does not exclude a plurality.

BRIEF DESCRIPTION OF FIGURES

Figure 1 shows an exemplary non-limiting system suitable for processing tall oil pitch according to the method of the present invention, and figure 2 shows the sediment [wt-%] and aged sediment [wt-%] as a function of hydrotreated tall oil pitch boiling above 360 °C at atmospheric pressure [vol-%] in an RMG blend.

DESCRIPTION

Definitions

As defined herein crude tall oil (CTO, CAS Registry Number 8002-26-4) is most frequently obtained as a by-product of either Kraft or Sulphite pulping processes and tall oil pitch (TOP, CAS number of 8016-81-7) is the residual bottom fraction from crude tall oil distillation processes.

Crude tall oil comprises resin acids, fatty acids, and unsaponifiables. Resin acids are a mixture of organic acids derived from oxidation and polymerization reactions of terpenes. The main resin acid in crude tall oil is abietic acid but abietic derivatives and other acids, such as pimaric acid are also found. Fatty acids are long chain monocarboxylic acids and are found in hardwoods and softwoods. The main fatty acids in crude tall oil are oleic, linoleic, and palmitic acids. Unsaponifiables cannot be turned into soaps as they are neutral compounds which do not react with sodium hydroxide to form salts. They include sterols, higher alcohols, and hydrocarbons. Sterols are steroids derivatives which also include a hydroxyl group.

Tall oil pitch (TOP) can be considered to be a UVCB substance (Substances of Unknown or Variable composition, Complex reaction product or Biological materials) under the REACH definition. Composition of TOP according to Holmbom (1978) is presented in Table 1 . Tall oil pitch typically comprises from 34 to 51 wt% free acids, from 23 to 37 wt% esterified acids, and from 25 to 34 wt% unsaponifiable neutral compounds of the total weight of the tall oil pitch. The free acids are typically selected from a group consisting of dehydroabietic acid, abietic and other resin acids. The esterified acids are typically selected from a group consisting of oleic and linoleic acids. The unsaponifiables neutral compounds are typically selected from a group consisting of diterpene sterols, fatty alcohols, sterols, and dehydrated sterols.

Table 1 . Component Group Composition of Tall Oil Pitch (wt % of pitch) ³ chemistry society, 55, pp. 342-344.

As defined herein marine fuels, also called bunker fuels, are products that fulfill the ISO 8217:2017 specification of marine fuels. Depending on whether the fuel was produced through distillation or comes from the oil refinery residue, it is classified as a distillate (or “distillate fuel” according to the standard) or a residual fuel. In accordance with ISO 8217, residue fuels are divided into different fuel types depending on their viscosity (kinematic viscosity) - RMA, RMB, RMD, RME, RMG and RMK.

A defined herein RMB is a residual based marine fuel oil with the viscosity of max 30 mm ² /s.

As definer herein RMG is a residual based marine fuel oil with the viscosity of max 700mm ² /s.

The method comprises the following steps : a) providing feedstock comprising tall oil pitch, b) subjecting the feedstock to hydrotreatment reaction conditions to produce a hydrotreated tall oil pitch, wherein the hydrotreatment reaction conditions comprise pressure between 30 barg and 200 barg, and temperature between 300 °C and 350 °C, wherein the subjecting is in the presence of hydrogen stream and one or more hydrotreatment catalysts, and c) fractionating the hydrotreated tall oil pitch to a first fraction and to a second fraction, wherein the second fraction is the marine fuel component.

The hydrotreatment reaction conditions comprise pressure between 30 barg and 200 barg and temperature between 300 °C and 350 °C. The reaction temperature is limited to 350 °C to avoid excess hydrocracking reactions. The subjecting is in the presence of a hydrogen stream and one or more hydrotreatment catalysts. For receiving optimal results hydrotreatment catalyst is sulphated NiMo. Other hydrotreatment catalyst such as sulphated CoMo or NiW can be used as well. H2/feed ratio is typically 300-1000 N-L/L. An exemplary Fk/feed ratio is 950 N-L/L

An exemplary system suitable for the method of the present invention is shown in figure 1 . Accordingly, the feedstock comprising TOP is fed from a feed tank 10 to a reactor 20 wherein the hydrotreatment is performed. The reactor is preferably a fixed-bed reactor comprising a sulphated NiMo-catalyst. The hydrotreated feed is fed through a gas-liquid separator 30 to distillation unit 40, wherein water is separated from the feed, and the hydrotreated product is transferred to a tank 50. Finally, the hydrotreated product is fed to the distillation unit 60 and fractionated to a first fraction (diesel; bp 180 - 360 °C at atmospheric pressure) and to a second fraction (heavy fraction; bp > 360°C at atmospheric pressure).

In one embodiment first fraction contains more than 90 wt.-% of components having a boiling point between 180°C and 290°C (at normal pressure, i.e., about 1 bar absolute) and a second fraction contains more than 90 wt.-% of components having a boiling point above 290°C (at normal pressure, i.e., about 1 bar absolute).

In another embodiment first fraction contains more than 90 wt.-% of components having a boiling point between 180°C and 300°C (at normal pressure, i.e., about 1 bar absolute) and a second fraction contains more than 90 wt.-% of components having a boiling point above 300°C (at normal pressure, i.e., about 1 bar absolute). In another embodiment first fraction contains more than 90 wt.-% of components having a boiling point between 180°C and 310°C (at normal pressure, i.e., about 1 bar absolute) and a second fraction contains more than 90 wt.-% of components having a boiling point above 310°C (at normal pressure, i.e., about 1 bar absolute).

In another embodiment first fraction contains more than 90 wt.-% of components having a boiling point between 180°C and 320°C (at normal pressure, i.e., about 1 bar absolute) and a second fraction contains more than 90 wt.-% of components having a boiling point above 320°C (at normal pressure, i.e., about 1 bar absolute).

In another embodiment first fraction contains more than 90 wt.-% of components having a boiling point between 180°C and 330°C (at normal pressure, i.e., about 1 bar absolute) and a second fraction contains more than 90 wt.-% of components having a boiling point above 330°C (at normal pressure, i.e., about 1 bar absolute).

In another embodiment first fraction contains more than 90 wt.-% of components having a boiling point between 180°C and 340°C (at normal pressure, i.e., about 1 bar absolute) and a second fraction contains more than 90 wt.-% of components having a boiling point above 340°C (at normal pressure, i.e., about 1 bar absolute).

In another embodiment first fraction contains more than 90 wt.-% of components having a boiling point between 180°C and 350°C (at normal pressure, i.e., about 1 bar absolute) and a second fraction contains more than 90 wt.-% of components having a boiling point above 350°C (at normal pressure, i.e., about 1 bar absolute).

In another embodiment first fraction contains more than 90 wt.-% of components having a boiling point between 180°C and 360°C (at normal pressure, i.e., about 1 bar absolute) and a second fraction contains more than 90 wt.-% of components having a boiling point above 360°C (at normal pressure, i.e., about 1 bar absolute).

According to a preferable embodiment part of the hydrotreated feed is recirculated from the tank 50 to the hydrotreatment reactor 20 applying an internal product recycle. The ratio is typically between 1 :2 (v/v) and 1 :12 (v/v) for feeding to the distillation unit 60 and recycling to the hydrotreatment 20 unit, respectively. Accordingly, a major portion of the hydrotreated feed is recirculated back to the hydrotreatment unit. The aim of the recycling is to control the acidity and heat release inside the reactor. According to one embodiment the marine fuel composition obtained is blended with residual based marine fuel oil (RMG). Blending ratio is typically from 10:90 (v/v) to 90:10 (v/v). Exemplary blending ratios are 20:80 (v/v), 50:50 (v/v).

According to another embodiment the marine fuel composition is blended with distilled based marine fuel oil (RMB). Blending ratio is typically from 10:90 (v/v) to 90:10 (v/v). Exemplary blending ratios are 20:80 (v/v), 50:50 (v/v).

According to still another embodiment the marine fuel composition is blended with one or more further renewable marine fuel compositions. Exemplary feedstocks for producing the further renewable marine fuel compositions are vegetable oils and animal fats preferably containing triglycerides and fatty acids and esters.

According to one embodiment the feedstock consists entirely of TOP. Processed TPO did not have compatibility problems with the fossil based marine fuel product.

EXPERIMENTAL

Tall oil pitch was hydrotreated in a fixed-bed reactor using sulphated NiMo-catalyst. Pressure range was 30-200 barg under continuous hydrogen flow at temperature of 300-350 °C. After the hydrotreatment the product was distilled to a diesel fraction (bp. 180 -360 °C) and a heavy fraction (bp. above 360 °C). The fraction boiling above 360 °C is the marine fuel composition.

Properties of the second fraction boiling above 360 °C at atmospheric temperature are presented in Table 2.

Table 2. Properties of hydrotreated Tall Oil Pitch (bp > 360°C at atmospheric pressure).

NM380: Elemental contents of oil products are determined with X-ray fluorescence. Measurement is based on wavelength dispersive X-ray fluorescence. NM463: Sample is diluted in solvent and measured with spectrophotometer. The polycyclic index is calculated based on the absorbance measured with spectrophotometer.

Blending tests

The distilled hydrotreated TOP fraction (bp > 360 °C) was studied with residual based marine fuel oil RMG and distilled based marine fuel oil which is classified as RMB because of the viscosity of the product. RMG and RMB products fulfill the ISO 8217:2017 specification of marine fuels. Based on the ISO 8217 standard the stability of the R classified products are evaluated and measured with aged sediment method (EN ISO 10307-2A). The specification limit for aged sediment is < 0.1 wt-%. Target of this blending study was to clarify the impact of hydrotreated TOP prepared according to the method of the present invention on marine fuel oil product stability. Marine fuel oil samples were RMG and RMB. RMG contains the heaviest bottom oil fraction and distillates. RMB contains the heaviest distillate fraction and distillates. Both products have sulphur content <0.1 wt-%. Blending test results are presented in following Table 3 and 4 and Figure 2.

Table 3. Hydrotreated Tall Oil Pitch (bp > 360°C) + RMG blend results ³ a. the sediment and aged sediment have been analyzed according to the methods of EN ISO 10307-1 and EN ISO 10307-2A. Sulphur has been analyzed according to the method of EN ISO 8754.

Table 4. Hydrotreated Tall Oil Pitch (bp > 360°C at atmospheric pressure) + RMB blend results ³ a. the sediment and aged sediment have been analyzed according to the methods of EN ISO 10307-1 and EN ISO 10307-2A. Sulphur has been analyzed according to the method of EN ISO 8754.

The results can be summarized as follows: o The hydrotreated TOP fraction (bp > 360°C) has very low sulphur content (16.4 mg/kg) which is good when using it in marine fuel oil product. o The hydrotreated TOP fraction (bp > 360°C) does not contain any sediment or aged sediment. o When blending distilled the hydrotreated TOP fraction (bp > 360°C) with RMG, the amount of aged sediment decreases as the hydrotreated TOP fraction (bp > 360°C) content in the blend increases. Accordingly, the hydrotreated TOP fraction (bp > 360°C) assists the stability of the blend and is suitable with this type of residual marine fuel oil product (table 3, figure 2). o When blending distilled the hydrotreated TOP fraction (bp > 360°C) with RMB the stability of the blend was at the good level in all blending ratios (table 4).

The specific examples provided in the description given above should not be construed as limiting the scope and/or the applicability of the appended claims.