Field

[0001] The invention relates to a pyrolysis method and apparatus for producing a bio-oil containing levogluco senone and/or chloromethylfurfural.

Background

[0002] Levoglucosenone (LGO) is a highly functionalized, non-toxic and biodegradable chemical that is used as a platform chemical in the production of downstream organic chemicals.

[0003] LGO can be produced via pyrolysis of cellulosic and hemicellulosic biomass. The conventional pyrolysis process generally includes pyrolyzing the biomass at temperatures in the range of 300 °C to 400 °C for sufficient time to generate a volatile stream and a waste char stream. The volatile stream is condensed to form a bio-oil.

[0004] The bio-oil typically contains levoglucosan (LGA), a low yield of levoglucosenone (LGO), and 2-furfuraldehyde (furfural). The furfural (2-furfuraldehyde) is formed in significant quantities as an impurity, often at concentrations as high as 5-10 wt%. Many other organic chemical impurities and water are present in the bio-oil. Given the presence of these impurities and the low yield of LGO, complex downstream separation processes are required to obtain the LGO.

[0005] Recently, fast pyrolysis methods have been investigated whereby the biomass is heated at a faster rate and potentially to higher temperatures. Fast pyrolysis processes have been found to increase the yield of bio-oil and reduce the production of char. However, this higher heating rate decreases the concentration of the LGO in the bio-oil since rapid pyrolytic decomposition of the feed biomass favours the production of other organic chemical impurities.

[0006] It is desirable to provide a process for forming a bio-oil with increased concentration of LGO and/or with a reduced concentration of other organic chemical impurities.

[0007] It is an object of the invention to address at least one shortcoming of the prior art and/or provide a useful alternative. Summary of Invention

[0008] In a first aspect of the invention there is provided a process for producing levoglucosenone and/or chloromethylfurfural from biomass comprising cellulosic and/or hemicellulosic material, the process comprising: subjecting the biomass to a first thermal treatment at a temperature of from about 200 °C to about 275 °C to form torrefied biomass and torrefaction gas; and subjecting the torrefied biomass to a second thermal treatment at a temperature of from about 300 °C to about 350 °C in the presence of an inorganic acid to form a pyrolysis gas comprising levoglucosenone and/or chloromethylfurfural.

[0009] In an embodiment, the chloromethylfurfural is 5-chloromethylfurfural.

[0010] In an embodiment, the first thermal treatment is carried out in a first fluidized bed reactor and/or the second thermal treatment is carried out in a second fluidized bed reactor.

[0011] In an embodiment, the inorganic acid is a selected from the group consisting of HC1, HBr, and HI.

[0012] In an embodiment, the torrefaction gas comprises one or more organic acid(s), alcohol(s), ketone(s), aldehyde(s), and combinations thereof.

[0013] In an embodiment, the torrefaction gas is substantially free of levoglucosenone and/or chloromethylfurfural .

[0014] In an embodiment, the residence time of the first thermal treatment is about 2 to about 20 seconds and/or wherein the residence time of the second thermal treatment is about 2 to about 20 seconds.

[0015] In an embodiment, the biomass is selected from the group consisting of delignified biomass, commercial cellulose, waste coffee cups, biodegradable plates, waste paper, and combinations thereof. [0016] In an embodiment, a condensable fraction of the torrefaction gas is condensed to form a first bio-oil and/or a condensable fraction of the pyrolysis gas is condensed to form a second bio-oil comprising the levoglucosenone and/or chloromethylfurfural.

[0017] In an embodiment, the process is a continuous process comprising: continuously feeding biomass to a first reaction vessel to subject the biomass to the first thermal treatment; and continuously feeding torrefied biomass from the first reaction vessel to the second reaction vessel to subject the torrefied biomass to the second thermal treatment.

[0018] In one form of the above embodiment, the first reaction vessel is a first fluidized bed reactor, and wherein the process further comprises fluidizing the biomass in the first fluidized bed reactor with a continuous feed of an inert gas, wherein the torrefaction gas is entrained in the inert gas and continuously withdrawn from the first fluidized bed reactor with the inert gas.

[0019] In one form of the above embodiment, the second reaction vessel is a second fluidized bed reactor, and wherein the process further comprises fluidizing the torrefied biomass in the second fluidized bed reactor with a continuous feed of a fluidization gas, wherein the pyrolysis gas is entrained in the fluidization gas and continuously withdrawn from the second fluidized bed reactor with the fluidization gas. Preferably, the inorganic acid in introduced into the second reaction vessel with the fluidization gas.

[0020] In one form of the above embodiment, the torrefied biomass is continuously conveyed from the first reaction vessel to the second reaction vessel via a screw conveyor.

[0021] In an embodiment, the first thermal treatment is conducted at a temperature of from about 200 °C to about 250 °C.

[0022] In a second aspect of the invention, there is provided a bio-oil formed according to the process of the first aspect of the invention and/or embodiment and/or forms thereof.

[0023] In a third aspect of the invention, there is provided an apparatus for producing, or when used to produce, levoglucosenone and/or chloromethylfurfural from biomass comprising cellulosic and/or hemicellulosic material, the apparatus comprising: a first fluidized bed reactor configured to form a fluidized bed of the biomass in a fluidization zone thereof and subject the fluidized bed of biomass to a first thermal treatment at a temperature of from about 200 °C to about 275 °C to form torrefied biomass and torrefaction gas, the first fluidized bed reactor comprising: a biomass inlet for introducing biomass into the first fluidized bed reactor; a biomass outlet through which torrefied biomass can be withdrawn from the first fluidized bed reactor; a fluidizing gas inlet located beneath the fluidization zone to provide a source of an inert fluidizing gas; and a gas outlet located above the fluidization zone through which the torrefaction gas and inert fluidizing gas are removed from the first fluidized bed reactor; a second fluidized bed reactor configured to fluidize the torrefied biomass in a fluidization zone thereof and subject the biomass to a second thermal treatment at a temperature of from about 300 °C to about 350 °C in the presence of an inorganic acid to form a pyrolysis gas comprising levoglucosenone and/or chloromethylfurfural, the second fluidized bed reactor comprising: a biomass inlet for introducing the biomass into the second fluidized bed reactor; a biomass outlet through which residual biomass and char can be withdrawn from the second fluidized bed reactor; a fluidizing gas inlet located beneath the fluidization zone to provide a source of a fluidizing gas; and a gas outlet located above the fluidization zone through which the pyrolysis gas and fluidizing gas are removed from the second fluidized bed reactor; a screw conveyor for transferring biomass from an outlet of the first fluidized bed reactor and through the inlet of the second fluidized bed reactor.

[0024] In an embodiment, the apparatus further comprises a first condenser for condensing a condensable fraction of the torrefaction gas into a first bio-oil and a second condenser for condensing a condensable fraction of the pyrolysis gas into a second bio-oil comprising levoglucosenone and/or chloromethylfurfural.

[0025] In an embodiment, the first fluidized bed reactor is configured to operate with a biomass residence time of from about 2 to about 20 seconds and/or the second fluidized bed reactor is configured to operate with a biomass residence time of from about 2 to about 20 seconds. [0026] In an embodiment, the apparatus is configured to operate in a continuous manner.

[0027] In an embodiment, the first thermal treatment is conducted at a temperature of from about 200 °C to about 250 °C.

[0028] In a fourth aspect of the invention, there is provided a method comprising converting levoglucosenone obtained according to the process of the first aspect of the invention and/or embodiment and/or forms thereof into a compound selected from the group consisting of: dihydrolevoglucosenone, levoglucosanol, tetrahydrofurandimethanol, or 1,6-hexanediol via a hydrogenation process.

[0029] In a fifth aspect of the invention, there is provided a method comprising synthesising a compound selected from the group consisting of: butenolides, dihydropyrans, substituted cyclopropanes, deoxy-sugars, and ribonolactones, wherein levoglucosenone obtained according to the process of the first aspect of the invention and/or embodiment and/or forms thereof is used in the method as a precursor compound.

[0030] In a sixth aspect of the invention, there is provided a method comprising converting chloromethylfurfural obtained according to the process of the first aspect of the invention and/or embodiment and/or forms thereof into a compound selected from the group consisting of: levulinic acid, formic acid, and oxygenate compounds.

[0031] In embodiments of the aspects above the chloromethylfurfural is 5 -chloromethylfurfural.

[0032] Reference to any prior art in the specification is not an acknowledgment or suggestion that this prior art forms part of the common general knowledge in any jurisdiction or that this prior art could reasonably be expected to be understood, regarded as relevant, and/or combined with other pieces of prior art by a skilled person in the art.

[0033] As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude further additives, components, integers or steps. [0034] Further aspects of the present invention and further embodiments of the aspects described in the preceding paragraphs will become apparent from the following description, given by way of example and with reference to the accompanying drawings.

Brief Description of Drawings

[0035] Figure 1 is a schematic of an apparatus for a single stage slow pyrolysis process for production of bio-oil from biomass.

[0036] Figure 2 are graphs showing Furfural and LGO peak area based on step-wise slow pyrolysis of HW-Raw (a), and HW-Delignified (b) at different temperatures.

[0037] Figure 3 is a schematic of an apparatus for a two-stage biomass conversion unit for production of bio-oil comprising LGO and/or CMF.

[0038] Figure 4 are GC-MS chromatograms of step-pyrolysis (1st step) bio-oil of Hardwood- delignified biomass at 225 °C (a) and 250 °C (b).

[0039] Figure 5 are GC-MS chromatograms of step-pyrolysis (2nd step) bio-oil of Hardwood- delignified biomass at 300 °C (a) and 325 °C (b) (1st step was at 250 °C).

[0040] Figure 6 is a process and mass flow diagram showing peracetic acid pre-treatment and LGO production from hardwood biomass using a one-step thermo-catalytic process (350 °C).

[0041] Figure 7 is a process and mass flow diagram showing peracetic acid pre-treatment and LGO production from hardwood biomass using a two-stage thermo-catalytic process (1st step at 250 °C and 2nd step at 300 °C).

Description of Embodiments

[0042] The invention broadly relates to a two-stage thermal treatment process of biomass to produce a bio-oil comprising levoglucosenone (LGO) and/or chloromethylfurfural (CMF), an apparatus for producing LGO and/or CMF, and methods for converting LGO and/or CMF to downstream chemical products. [0043] While the process described herein is able to produce LGO and/or CMF from any cellulosic and/or hemicellulosic feed stock, for example, commercial cellulose, waste coffee cups, biodegradable plates, and waste papers, a preferred feedstock is delignified biomass or biomass that is otherwise substantially free of lignin.

[0044] The two-stage process broadly comprises subjecting cellulose and/or hemi-cellulose containing biomass to a first thermal low temperature treatment step to produce a first volatile gas containing fraction, and then subjecting the remaining biomass to a second thermal high temperature treatment step to produce a second volatile gas containing fraction that comprises the LGO and CMF. Volatile gases in the second volatile gas fraction can then be condensed to produce a bio-oil containing the LGO and CMF.

[0045] The first and second treatment steps are preferably conducted in first and second fluidized bed reactors respectively since fluidization assists with heat transfer, mixing, and reaction kinetics. The use of fluidized bed reactors also means that the process can advantageously be operated in a continuous manner rather than as a batch process.

[0046] The first thermal treatment step is conducted at a temperature in the range of about 200 °C to about 275 °C, for example about 200 °C to about 250 °C. The first thermal treatment step is preferably carried out in a fluidized bed reactor. The first thermal treatment step is a low temperature pyrolysis step which is also commonly referred to as torrefaction. The inventors have found that low temperature pyrolysis / torrefaction is useful to reduce the water content of the biomass and form a first volatile gas containing fractions (e.g. a torrefaction gas) comprising low molecular weight / high volatility organic compounds from the bio-mass. These low molecular weight / high volatility organic compounds include organic acid(s), alcohol(s), ketone(s), aldehyde(s), low molecular weight cyclic aromatic compounds such as furans, and combinations thereof. The removal of these low molecular weight / high volatility organic compounds from the bio-mass prior to the second higher temperature treatment step is advantageous since they are then not available as reactants (e.g. to react with and thus consume LGO and CMF) during the second higher temperature treatment step nor are they present as impurities in the second volatile gas fraction comprising the LGO and/or CMF and the resultant bio-oil. [0047] The first thermal treatment step has an upper temperature limit of about 275 °C, and preferably 250 °C. This upper temperature limit is useful to avoid or reduce the likelihood that cellulosic or hemicellulosic material in the biomass is torrefied to form larger organic molecules, such as LGO and/or CMF. Given this, the torrefaction gas is substantially free of LGO and/or CMF which increases the overall yield of LGO and/or CMF recovered in the second volatile gas fraction. The torrefaction gas can be recovered and the condensable fraction thereof condensed to form a first bio-oil which substantially comprises these low molecular weight / high volatility organic compounds. In embodiments in which the first thermal treatment step is carried out in a fluidized bed reactor, torrefaction gas can be carried out of the reactor with the fluidization gas (typically an inert and non-condensable gas such as nitrogen) where it is subsequently passed through one or more condensers to recover the volatile fractions. Multiple condensers can be used to recover different condensable fractions at different temperatures if desired.

[0048] Generally, a residence time of about 2 to about 20 seconds is sufficient particularly where torrefaction is carried out in a fluidized bed reactor. The torrefied biomass is then subjected to a second thermal treatment step.

[0049] In embodiments in which the first and second thermal treatment steps are carried out in first and second reaction vessels (e.g. first and second fluidized bed reactors), the torrefied biomass may be transported from the outlet of the first reaction vessel to the inlet of the second reaction vessel by any means known to those skilled in the art. However, the use of a screw conveyor is advantageous since these are adapted to transport bulk particulate material and are designed to minimize fugitive emissions.

[0050] The second thermal treatment step is conducted at a temperature in the range of about 300 °C to about 350 °C. The second thermal treatment step is preferably carried out in a fluidized bed reactor with a residence time of about 2 to about 20 seconds. The higher temperature adopted in the second thermal treatment step is useful for pyrolysis of the torrefied biomass into larger organic molecules including LGO and/or CMF. The upper temperature limit of 350 °C minimises the formation of phenolic derivative products which are generally produced during pyrolysis of lignin at higher temperatures. [0051] To favour the production of LGO and/or CMF, and thus increase the overall yield of LGO and/or CMF, the second thermal treatment step is conducted in the presence of a gas phase inorganic acid catalyst, and generally a hydrogen halide such as HC1, HBr, or HI. The inventors have found that the use of an inorganic acid catalyst significantly increases the yield of LGO and/or CMF. Further, the inventors have found that the relative ratio of LGO:CMF produced in the second thermal treatment step can be tuned by adjusting the temperature and/or concentration of the inorganic acid catalyst. The use of a fluidized bed reactor is particularly advantageous where an inorganic acid catalyst is used since fluidization promotes good mixing and reaction kinetics.

[0052] The second volatile gas (e.g. the pyrolysis gas) comprises mainly sugars and oxygenated compounds of carbohydrates such as levoglucosan (LGA), LGO, and CMF. Condensable components, such as LGO and/or CMF, can be condensed from the pyrolysis gas to form a second bio-oil. In embodiments in which the second thermal treatment step is carried out in a fluidized bed reactor, pyrolysis gas can be carried out of the reactor with the fluidization gas where it is passed through one or more condensers to recover the volatile fractions. Multiple condensers can be used to recover different condensable fractions at different temperatures if desired.

[0053] LGO can be recovered and used as a platform chemical to produce a number of commercially useful chemical compounds. LGO is a suitable precursor for the synthesis of functionally active molecules, such as those with anti-cancer, anti-microbial, or antiinflammatory properties. By way of example, LGO can be converted to dihydrolevoglucosenone (a renewable and non-toxic solvent), levoglucosanol (a potential chiral precursor), tetrahydrofurandimethanol (a potential polymer precursor and renewable solvent), and 1,6- hexanediol (useful in polymers, coatings, and adhesive) through selective hydrogenation process. LGO can also be converted to enantiopure butenolides, dihydropyrans, substituted cyclopropanes, deoxy-sugars, and ribonolactones.

[0054] The use of LGO as a platform chemical and the conversion of LGO to commercially useful chemical compounds is described in at least “Hydrogenation of Levoglucosenone to Renewable Chemicals” (S. Krishna, D. McClelland, Q. Rashke, J. A. Dumesic and G. Huber, Green Chem., 2016, DOI: 10.1039/C6GC03028A.); and “Levoglucosenone: Bio-Based Platform for Drug Discovery” (J. E. Camp and B. W. Greatrex, Frontiers in Chemistry, 2022, DOI: 10.3389/fchem.2O22.90223). The entire contents of each of these publications is hereby incorporated by reference.

[0055] Krishna et al. discloses a process whereby LGO may be hydrogenated to dihydrolevoglucosenone (Cyrene), levoglucosanol (Lgol), and tetrahydrofurandimethanol (THFDM). In particular, LGO can be hydrogenated to cyrene at temperatures of about 40 °C catalyzed with a Pd/AhCh catalyst. Cyrene can subsequently be selectively hydrogenated to Lgol with an excess of the exo-Lgol isomer over the endo-Lgol isomer at a temperature of 100 °C and catalyzed with a Pd/AhCh catalyst. The Lgol can subsequently be hydrogenated to THFDM (including 2M-THFA, cis-THFDM, trans-THFDM, THP2M5one, and THP2M5H by varying hydrogenation conditions) at a temperature of 150°C using a bifunctional Pd/SiO2- AI2O3 catalyst or to 1,6-hexanediol.

[0056] Camp et al. provides an overview of various addition reactions that can be used to convert LGO to a range of different bioactive molecules, such as butenolides, dihydropyrans, substituted cyclopropanes, deoxy-sugars and ribonolactones through various reactions. By way of example, cyclopropanes can be prepared from LGO via cyclopropanation of the alkene of either LGO or one of its derivatives (e.g. Cyrene). Conjugate addition of the enone functionality of LGO can be used to synthesize biologically active derivatives of known compounds such as thromboxanes. 1,2-addition to the carbonyl of LGO can be used for the preparation of S- glycosylated thiosemicarbazone derivates. 1,4-addition of thiols to the LGO has been used to prepare biologically active anti-cancer LGO derivatives. The skilled person will appreciate that a variety of addition reactions are possible and that various different compounds may be added to the LGO structure (or derivatives thereof) to produce bio-active molecules.

[0057] CMF can also be recovered and used as a platform chemical to produce a number of commercially useful chemical compounds. CMF is important to efficient approaches to specialty goods, such as in the pharmaceutical and agricultural industries. CMF can be converted to two important acids: levulinic and formic acid. Through a subsequent chemical process, CMF can be used to generate simple fuel oxygenates, which are present in energy- dense petroleum-based fuels.

[0058] The use of CMF as a platform chemical and the conversion of CMF to commercially useful chemical compounds is described in at least “5-(Chloromethyl)furfural (CMF): A Platform for Transforming Cellulose into Commercial Products” (M. Mascal, ACS Sustainable Chem. Eng., 2019, DOI: 10.1021/acssuschemeng.8b06553). The entire contents of this publication is hereby incorporated by reference.

[0059] Mascal discloses that CMF can be converted to products such as levulinic acid and formic acid through a rehydration reaction. The levulinic acid and formic acid can then be used to produce a wide range of commercially useful molecules through reactions generally known to those skilled in the art.

Example 1

[0060] This example reports the slow pyrolysis of raw hard wood biomass (HW-Raw) and delignified hard wood biomass (HW-delignified) using a single stage pyrolysis step at temperatures of 250 °C, 275 °C, 300 °C, 325 °C, 350 °C, and 375 °C respectively.

[0061] Slow pyrolysis of the biomass was conducted using 40 g of oven-dried (105 °C for 24 hours) HW-Raw and HW-Delignified biomass. The general procedure is illustrated in Figure 1 which provides a schematic illustration of the process.

[0062] Biomass was heated in a reaction vessel 100 via heating mantle 102. The pyrolysis temperature was controlled via temperature controller 104 and thermocouple 105, which in Figure 1 is illustrated as having a set point temperature of 300 °C. High purity nitrogen gas 106 was initially used to purge the system. The heating rate was set at 5 °C/min to heat the biomass from room temperature to the final pyrolysis temperature (e.g. 250 °C, 275 °C, 300 °C, 325 °C, 350 °C, and 375 °C respectively). The biomass was then held at the final pyrolysis temperature for five minutes. The high purity nitrogen gas 106 was used to carry the pyrolysis gases from reaction vessel 100 through the first and second cold traps 108 and 110, which in this case were dry ice baths, were used to condense condensable fractions of the pyrolysis gas to form a bio-oil. Non-condensable gases were filtered through gas bag 112.

[0063] Table 1 below reports the pH of bio-oils formed according to the above-mentioned process at final pyrolysis temperatures of 250 °C, 275 °C, 300 °C, 325 °C, 350 °C, and 375 °C. Table 1: pH of bio-oil formed from slow pyrolysis of HW-Raw and HW-Delignified at different temperatures

[0064] pH is an important parameter since it provides an indication of the corrosiveness of the bio-oil. The lower the pH, the more acidic the bio-oil, and consequently the more corrosive the bio-oil. From the results it can be seen that the pH of bio-oils from the slow pyrolysis of HW- Raw biomass is lower at every temperature as compared with the HW-Delignified biomass. This suggests that the pyrolysis of HW-raw biomass tends to favour the production of organic acids as compared with the HW-delignified biomass. Without wishing to be bound by theory, the inventors are of the view that this is because hemicellulose, present in the HW-raw biomass, readily degrades into organic acids during pyrolysis.

[0065] Furthermore, the results show that with increasing temperature the pH of the resulting bio-oil increases toward neutral for both the HW-raw and HW-delignified biomasses. This signifies a shift in the types of organic compounds formed from pyrolysis at different temperatures. That is, the pyrolysis temperature has a significant effect on the types of organic compounds produced and their distribution.

[0066] Figure 2a and Figure 2b show furfural and LGO formation based on GC-MS peak area from bio-oil formed from the slow pyrolysis of HW-raw and HW-delignified biomass at temperatures of 250 °C, 275 °C, 300 °C, 325 °C, 350 °C, and 375 °C.

[0067] From Figure 2a, the results show an initial increase in the furfural peak area over a temperature of 250 °C to 300 °C, followed by a decrease with further increase in temperature. Without wishing to be bound by theory, the inventors are of the view that this change in furfural peak area occurs due to the structure of the biomass and the components thereof subject to degradation during pyrolysis. In particular, the thermal stability of major biomass components is cellulose > lignin > hemicellulose. However, due to the structure of biomass, the hemicellulose and cellulose are more difficult to degrade in the presence of lignin.

[0068] The above discussed results are consistent with the results obtained from the HW- delignified biomass which shows a maximum peak area of furfural at a lower temperature of 275 °C. Surprisingly, and in contrast with the results obtained from the HW-raw biomass, Figure 2b shows pyrolysis of the HW-delignified biomass resulted in a bio-oil with a high concentration of LGO which peaked at a temperature of 300 °C and exhibited decreasing concentration above 300 °C.

[0069] These results generally show that low temperature pyrolysis is effective for pyrolyzing organic biomass, and that the nature of the biomass (whether raw or delignified) and the pyrolysis temperature has a significant impact on the organic compounds recovered in bio-oil from the pyrolysis process. In particular, low temperature pyrolysis tends to favour the production of organic acids impurities while providing a low yield of desirable LGO. Higher temperature favours the production of LGO. However, significant impurities remain in the biooil.

Example 2

[0070] This example reports the slow pyrolysis of delignified hard wood biomass (HW- delignified) using a two-stage pyrolysis process in accordance with an embodiment of the invention.

[0071] Figure 3 is a schematic of two-stage biomass conversion apparatus 300 in accordance with an embodiment of the invention. The apparatus 300 includes a first fluidised bed reactor 302 configured to carry out a first thermal treatment step, and a second fluidised bed reactor 304 configured to carry out the second thermal treatment step. The first thermal treatment step can be considered a low temperature thermal treatment step, and the second thermal treatment step a high temperature thermal treatment step. In each case, the reactors are configured to form a fluidised bed of biomass via a source of fluidising gas 306, which in the illustrated embodiment is nitrogen gas. The flow of fluidising gas to the first and second fluidised bed reactors 302, 304 is controlled via valves 308, 310 respectively. Also illustrated is a gas line 312 to provide an additional supply of a gas to second fluidised bed reactor 302 with fluidising gas 306. The additional gas is an inorganic acid gas, such as a hydrogen halide which promotes formation of LGO and/or CMF as is discussed in more detail below. Biomass is continuously fed into first fluidised bed reactor 302 from hopper 314 via screw conveyor 316 which is powered by servo motor 318. In first fluidised bed reactor, the biomass is then fluidised and subjected to the first thermal treatment step. Gases evolved from the biomass during the first thermal treatment step are entrained within the flow of fluidising gas and continuously removed as a gas stream from an upper outlet 318 of first fluidised bed reactor 302. A condensable fraction of the gas stream is condensed in a condenser 320 and recovered in the form of a first bio-oil. Biomass, after being subjected to the first thermal treatment step, is continuously transported from an outlet of first fluidised bed reactor 302 to an inlet of second fluidised bed reactor 304 via screw conveyor 322. Screw conveyor 322 is driven by servo motor 324. However, it will be apparent to the skilled person that both screw conveyors 316 and 322 could be driven by a single servo motor, e.g. with appropriate gearing. The biomass is then fluidised with fluidisation has 306 the inorganic acid gas and subjected to a second thermal treatment process is second fluidised bed reactor 304. Gases evolved from the biomass during the second thermal treatment step are entrained within the flow of fluidising gas and continuously removed as a gas stream from an upper outlet 324 of second fluidised bed reactor 304. A condensable fraction of the gas stream is condensed in a condenser 326 and recovered in the form of a second bio-oil. Biomass, after being subjected to the second thermal treatment step, is continuously discharged from an outlet of second fluidised bed reactor 304 and collected as char 328. Flapper valves 330 and 332 can control the flow of biomass through the system.

[0072] The first thermal treatment step is a low-temperature thermal treatment step, also known as torrefaction. This stage may be carried out at a temperature of from 200 °C to 275 °C. In this particular example, two trial runs were conducted at temperatures of 225 °C and 250 °C.

[0073] The first stage can be considered a purification step to treat the biomass to selectively remove and condense volatile components such as aldehydes, alcohols, and carboxylic acids which are generally formed during low temperature slow pyrolysis as discussed above in relation to Example 1. This reduces or otherwise minimises the likelihood of these components forming in the second higher temperature pyrolysis stage. The low temperature thermal treatment also opens the chemical structure of the cellulose and hemicellulose to form LGA and/or anhydrosugars which are subsequently reacted to form LGO and CMF in the second stage.

[0074] Bio-oil recovered from the first stage experiments conducted at 225 °C and 250 °C were analysed using Gas Chromatography Mass Spectrometry (GC-MS). The results are shown in Figure 4a and Figure 4b respectively. The major chemicals in the bio-oils were furfural (RT 5.92), 9.04 (Trimethylene Oxide), 10.94 (LGO), 12.54 (2,3 Anhydrogalactosan), 13.86 (Isorbide), 16.91 (P-D-Glucopyranose, 1,6-anhydro), 17.33 (D-Allose) and 18.15 (1,6-Anhydro- a-D-galactofuranose. The pH of the bio-oils was 3.99 and 4.06 respectively.

[0075] The second stage is a higher temperature pyrolysis process which is operated at a temperature of from 300 °C to 350 °C in the presence of an inorganic acid gas. In this particular example, torrefied biomass taken from the first stage experiment conducted at 250 °C was thermally treated in a second stage at 300 °C and 325 °C in the presence of a gas phase HC1 catalyst.

[0076] Bio-oil recovered from the second stage experiments conducted at 300 °C and 325 °C were analysed using GC-MS. The results are shown in Figure 5a and Figure 5b. As can be seen, the biomass conversion at second stage 300 °C (1st stage temperature 250 °C) provided a high concentration of LGO with furfural being undetectable. In contrast, biomass conversion at second stage 325 °C (1st stage temperature 250 °C) provided LGO and CMF with furfural being undetectable.

[0077] Based on the total area percentage of all detected compounds in the bio-oil, the GC-MS results indicated that the LGO selectivity was 77.47% at 300 °C and 64.30% at 325 °C, the selectivity of CMF was 1.09% at 300 °C and 19.95% at 325 °C. The percentage of components present in the bio-oil, as measured by the GC-MS analysis, is referred to as selectivity.

[0078] Water was also present in the bio-oil, owing to the moisture content of the biomass and the interaction of bound water with the component cell wall polymer. According to the GC-TCD analysis, the water content was 11.63% at 300 °C and 10.77% at 325 °C. The overall concentration of LGO was 43.81 mg/mL of bio-oil at 300 °C and 32.53 mg/mL of bio-oil at 325 [0079] The HC1 gas increased the selectivity of the desired chemicals in the second stage as compared with the slow pyrolysis of HW-delignified biomass at comparable temperatures reported in Example 1. Furthermore, both second stage reactions produced a lower quantity of undesirable products than the single stage process. Increasing the temperature from 300 °C to 325 °C also influenced the production of CMF. Overall, the two-stage process increases the selectivity and yield of EGO and facilitates production of LGO.

Example 3

[0080] This example reports the results of pyrolysis of HW-delignified biomass in a one stage pyrolysis process conducted at 350 °C and a two-stage pyrolysis process with a first stage conducted at 250 °C and a second stage conducted at 300 °C catalysed with HC1 gas. In each case, the pyrolysis was carried out in a fluidised bed reactor.

[0081] The results are summarized in Figures 6 and 7. Figure 6 is a process flow diagram showing the thermochemical conversion of the HW-delignified biomass with compositional data obtained from GC-MS showing the sugar content and LGO production for a single stage process. Figure 7 is a process flow diagram showing the thermochemical conversion of the HW-delignified biomass with compositional data obtained from GC-MS showing the sugar content and LGO production for a two-stage process in accordance with one or more embodiments of the invention.

[0082] In the single stage process, 100 g of hardwood biomass comprising 40.51 g glucan, 22.12 g xylan, 2.68 g arabinan, and 33.53 g of lignin is sent to a delignification step for pretreatment with peracetic acid (hydrogen peroxide 300 mL, + 300 mL acetic acid + 6.96 g of 98 wt% H2SO4 and water) to form a cellulose rich delignified biomass and a residue. The cellulose rich biomass has a total mass of 48.58 g and comprises 36.46 g glucan, 6.54 g xylan, 3.90 g lignin, 1.39 g arabinan, and 0.29 g ash with a loss of 1.47 g. The resulting residue has a total mass of 49.95 g and comprises 29.53 g lignin, 3.85 g glucan, 15.38 g xylan, 1.19 g of arabinan. The cellulose rich delignified biomass is then sent for pyrolytic treatment at 350 °C with aqueous HC1 and CaCh solution for thermo-catalytic conversion. The result is 7.16 g noncondensable gases, 21.54 g solid char, and 17.28 g of bio-oil comprising 0.436 g LGO and 0.201 g CMF. [0083] In the two-stage process, 100 g of hardwood biomass comprising 40.51 g glucan, 22.12 g xylan, 2.68 g arabinan, and 33.53 g of lignin is sent to a delignification step for pre-treatment with peracetic acid (hydrogen peroxide 300 mL, + 300 mL acetic acid + 6.96 g of 98 wt% H2SO4 and water) to form a cellulose rich delignified biomass and a residue. The cellulose rich biomass has a total mass of 48.58 g and comprises 36.46 g glucan, 6.54 g xylan, 3.90 g lignin, 1.39 g arabinan, and 0.29 g ash, with a loss of 1.47 g. The resulting residue has a total mass of 49.95 g and comprises 29.53 g lignin, 3.85 g glucan, 15.38 g xylan, 1.19 g of arabinan. The cellulose rich delignified biomass is then sent for a first pyrolytic treatment at 250 °C. The result is 3.402 g non-condensable gases, 35.21 g solid biomass, and 7.23 g of bio-oil comprising levoglucosan, levoglucosenone, furfural, anhydrous sugar and furan. The 35.21 g of biomass is then sent to a second pyrolytic treatment at 300 °C. The result is 6.374 g non-condensable gases, 19.08 g solid char, and 9.73 g of bio-oil comprising 0.511 g LGO.

[0084] The overall amount of bio-oil produced from a single-step thermochemical conversion of biomass was 17.28 g with 0.436 g of LGO and 0.201 g CMF in it. Thus, the concentration of LGO in the bio-oil was 2.5 wt%. The total amount of bio-oil produced from a two-stage biomass conversion procedure was 16.96 g of which 7.23 g was obtained from the first stage, and 9.73 g was obtained from the second stage. The bio-oil obtained in the second stage included 0.511 g of LGO. Thus, the yield of LGO in the second stage bio-oil was 5.3 wt% which is significantly higher than that obtained from the single-step process.

Example 4

[0085] This example reports results for the production of LGO and CMF from the pyrolysis of HW-delignified biomass using a two-stage pyrolysis process over a range of different first and second stage temperatures in accordance with the process generally described in Figure 7.

[0086] The results for the production of LGO and CMF are summarised in Tables 2 and 3 below respectively. Table 2: LGO concentration as a function of 1 ^st and 2 ^nd stage temperatures

[0087] The results confirm that a two-stage pyrolysis of delignified biomass facilitates a higher yield of LGO than in comparison with a single stage process (see Example 3 and Figure 7).

Table 3: CMF concentration as a function of 1 ^st and 2 ^nd stage temperatures

*ND is not detected [0088] The results further confirm the delignification of biomass, leaving mostly cellulose, facilitates higher yield of the target chemicals (LGO and CMF). Further, it can be inferred from the results that, as a co-reactant, HC1 acts as a catalyst that boosts the concentration of LGO and that the catalytic performance of HC1 assists selectivity of the target chemicals in the two-step pyrolysis of delignified biomass.

[0089] Tables 4 and 5 report the results of gas analysis of HW-deliginified biomass (on a nitrogen free basis) during the first and second pyrolysis stages respectively for different first and second stage temperatures.

Table 4: Gas Analysis of HW-Delignified biomass (nitrogen-free basis) during 1 ^st stage of pyrolysis

*ND is not detected

Table 5: Gas Analysis of HW-Delignified biomass (nitrogen-free basis) during 2 ^nd stage of pyrolysis [0090] The results suggest that the non-condensable pyrolysis gases are produced from the primary decomposition of biomass and secondary cracking of vapors. As the temperature increases, secondary reactions such as decarboxylation, deoxygenation, dehydrogenation, and cracking take place.

[0091] The non-condensable gas mixture contains CO2, CO, and light-hydrocarbons such as methane, ethane, propane. The decomposition and reforming of carbonyl and carboxyl groups are the primary sources of CO2 and CO. The lighter hydrocarbons are formed due to the restructuring and breaking of heavier hydrocarbons. This explains why methane, ethane and propane were not detected at the output of the 1 ^st stage pyrolysis.

[0092] It will be understood that the invention disclosed and defined in this specification extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention.