Field of the invention

The present invention relates to a method and apparatus for converting lignocellulose to chemicals in a multiphase reactor.

Background of the invention

Fossil fuels are the primary source of energy and chemicals in the contemporary world. The adverse impact on the environment caused by relentless usage of already depleting reserves of fossils entails the usage of renewable resources for energy and chemicals. Lignocellulosic biomass is a renewable alternative for producing energy, fuels and chemicals. However, the current production of lignocellulosic biomass is not sufficient to completely replace the applications of fossils. In US alone, it would take at least 50 years for the proposed seven fold increase in lignocellulosic biomass production. The increase of lignocellulosic biomass utilisation in industry would make it a scarce resource that necessitates sagacious conversion of biomass to high-value products. Further, the low prices of crude oil and shale gas make the usage of lignocellulosic biomass for fuel and energy less lucrative. Biomass conversion to high- value chemicals would not only expand product portfolio of bio-refinery but also foster its economically viability and cost competitiveness.

Lignocellulosic biomass conversion to high-value platform chemicals can be achieved through thermochemical and biochemical methods. Biochemical methods are selective but are cost and time intensive. Thermochemical methods, albeit less selective, bear the potential for one step conversion of lignocellulosic biomass to high- value chemicals. The selectivity of thermochemical method can be improved through catalysis. Certain chemicals that can be produced from thermochemical conversion are: 5-hydroxymethyl furfural (5-HMF), furfural, Levoglucosenone (LGO), levulinic acid, aromatics and olefins.

5-HMF is analogous to terephthalic acid and serves as critical nexus between carbohydrate chemistry and mineral-oil based chemistry. It finds application in textile, pharmaceutical, polymer and fuel industry. However, in spite of significant research performed at laboratory scale, there is no commercial scale process for 5-HMF production. 5-HMF is highly polar and hydrophilic, which convolutes its separation from the reaction media. Acid-catalysis produces 5-HMF but also facilitates its breakdown to hum ins. The challenge of producing 5-HMF can be overcome by producing a functionally equivalent 5-Chloromethyl furfural (5-CMF). The current processes for producing 5-CMF from lignocellulose, cellulose or saccharides involve aqueous phase reactions that employ toxic or expensive solvents using continuous flow reactor, microwave reactor or stirred tank reactor (STR).

PCT patent publication WO 2012/170520 discloses a method for producing substituted furans (such as halomethylfurfural, hydroxymethylfurfural, and furfural) by acid-catalysed conversion of biomass using a dry gaseous acid in a multiphase reactor. This document discloses that the method may be conducted in a multiphase reactor over a general pressure range of between 0.001 atm and 350 atm and a temperature of from 50 °C to 500 °C. As such, the method apparently requires a system for providing either medium vacuum conditions or high pressure. This document additionally discloses using a very high throughput of a mineral acid, exemplifying the treatment of 50 kg/min of lignocellulosic biomass in a 2000 L fluidised bed reactor, which fluidising gas consisted of an gaseous HCI feed at 4,000 L/min. Conditions inside the reactor were about 220 °C and 15 atm. Due to the large throughput of HCI, unreacted gaseous HCI is collected at the exit, dried, and recycled into the reactor. The method resulted in the formation of 5-(chloromethyl)furfural, 5-(hydroxymethyl)furfural, and furfural, as well as small quantities of levulinic acid and formic acid (as analysed via liquid chromatography-mass spectrometry). The use of large volumes of unreacted HCI adds significant expense and risk.

Levoglucosenone is gaining attention as promising platform chemical with applications in pharmaceutical, polymer and dairy industry. Dihydrolevoglucosenone is a potential replacement for toxic solvents like DMF and NMP. Most of the current methods focus on the usage of organic solvents, aqueous mineral acid, solid acid catalyst in STR, microwave reactor, fixed bed reactor, pyroprobes or auger reactor.

PCT patent publication WO 2016/039996 discloses a method of producing levoglucosenone in a continuous liquid phase reactor. The method includes contacting, in a continuous manner, a carbohydrate source, a solvent, and an acid catalyst in a continuous liquid phase reactor under reaction conditions sufficient to form a reaction mixture comprising levoglucosenone, wherein the reaction conditions include a liquid residence time in the reactor of between about 0.1 minutes and about 20 minutes; the method is generally disclosed as being conducted at a temperature of 75 °C to 300 °C and under a reactor pressure of 3 kPa to 100 kPa.

PCT patent publication WO 2011/000030 discloses a method for converting lignocellulosic materials into useful chemicals including levoglucosenone in an auger reactor. The method includes forming a mixture of particulate lignocellulosic material with a catalyst composition containing polar organic liquid and an acid, heating the mixture to a temperature in the range of 190 °C to 500 °C to convert a major portion of a solid portion of the mixture to char whilst agitating the mixture, and separating the volatile organic compounds and the catalyst composition as a gaseous phase. The method is conducted in an auger reactor under a vacuum pressure in the range of 0.1 to 900 mbar. Thus, the system is difficult to scale up, and is energy and cost intensive.

Multiphase reactors are a well-established and widely used technology, and have previously been employed for lignocellulosic biomass valorisation to energy and fuels. Further multiphase reactors are an easily scalable technology that offer effective control over residence time, temperature control, and heat transfer. Despite this, there are very few studies that use this technology for converting lignocellulosic biomass to chemicals, and in particular for the conversion of biomass to platform chemicals like levoglucosenone and substituted furans, particularly in a fluidised bed reactor.

An object of the present invention is to provide a method and/or apparatus for the production of levoglucosenone and a substituted furan from lignocellulosic biomass in a multiphase reactor that addresses one or more problems associated with prior art processes.

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. Summary of the invention

In a first aspect of the invention, there is provided a method for producing levoglucosenone and a substituted furan from lignocellulosic biomass, the method including: converting lignocellulosic biomass, in contact with an acid within a multiphase reactor, to a gaseous product including levoglucosenone and a substituted furan in a reaction zone of the multiphase reactor; wherein the acid is in sufficient concentration to catalyse the conversion of a portion of the lignocellulosic biomass to levoglucosenone and to react with another portion of the lignocellulosic biomass to form a substituted furan; and withdrawing a gaseous product from the multiphase reactor, the gaseous product including the levoglucosenone and the substituted furan.

The term‘gaseous product’ as used herein is intended to include gases, which can include volatile compounds and/or compounds otherwise entrained therein.

In an embodiment, the production of levoglucosenone and the substituted furan occurs simultaneously or substantially at the same time.

In an embodiment, the step of converting the lignocellulosic biomass further includes fluidising the lignocellulosic biomass with a fluidising gas. Preferably, the fluidising gas has a residence time in the multiphase reactor of 60 s or less. More preferably, the residence time is 40 s or less. Even more preferably, the residence time is 20 s or less. Still more preferably, the residence time is 10 s or less. Most preferably, the residence time is 5 s or less.

In one or more forms of the above embodiment, the fluidising gas includes an inert carrier gas. The skilled person will appreciate that a range of different inert carrier gases may be used. However, it is preferred that the inert carrier gas is selected from the group consisting of nitrogen and/or argon. Alternatively, or additionally, the fluidising gas includes one or more gaseous constituents selected from the group consisting of: acid in the form of a gaseous acid (which may be the acid or a further additional acid), reductants, and oxidants. In various forms of the invention, the fluidising gas includes, consists of, or consists essentially of the inert gas and the acid. Preferably, the concentration of the acid in the fluidising gas is from about 0.00001 % (v/v) to 99.99999%. In alternative forms of the invention, the fluidising gas includes, consists of, or consists essentially of the acid. Thus, in one or more embodiments, the amount of acid in the fluidising gas is from 0.0001 %(v/v) to 100%(v/v).

In an embodiment the fluidising gas includes the acid as a gaseous acid, and the method further includes: adjusting an amount of the acid in the fluidising gas and/or the residence time of the fluidising gas and/or a temperature of the converting step to alter a yield of levoglucosenone and/or substituted furans in the gaseous product.

In a second aspect of the invention, there is provided a method for producing levoglucosenone and a substituted furan from lignocellulosic biomass in a multiphase reactor, the multiphase reactor including: a first inlet for introducing lignocellulosic biomass into the multiphase reactor, a second inlet for introducing a fluidising gas into the multiphase reactor, a reaction zone within which lignocellulosic biomass is in contact with an acid, the reaction zone being arranged between the first inlet and the second inlet such that the fluidising gas flows from the second inlet and through the reaction zone to fluidise at least the lignocellulosic biomass in the reaction zone, and an outlet for withdrawing a gaseous product including the levoglucosenone and the substituted furan; the method including: introducing lignocellulosic biomass into the multiphase reactor through the first inlet; introducing a flow of fluidising gas through the second inlet; fluidising the lignocellulosic biomass with the flow of fluidising gas; converting lignocellulosic biomass to a gaseous product including levoglucosenone and a substituted furan in the reaction zone, wherein during the step of converting the lignocellulosic biomass, the lignocellulosic biomass is in contact with the acid at sufficient concentration to catalyse the conversion of a portion of the lignocellulosic biomass to levoglucosenone, and to react with another portion of the lignocellulosic biomass to form a substituted furan; and withdrawing the gaseous product through the outlet.

In an embodiment, the fluidising gas has a residence time in the multiphase reactor of 60 s or less. Preferably, the residence time is 40 s or less. More preferably, the residence time is 20 s or less. Even more preferably, the residence time is 10 s or less. Most preferably, the residence time is 5 s or less.

In an embodiment, the fluidising gas includes an inert carrier gas. The skilled person will appreciate that a range of different inert carrier gases may be used. However, it is preferred that the inert carrier gas is selected from the group consisting of nitrogen and/or argon. Alternatively, or additionally, the fluidising gas includes one or more gaseous constituents selected from the group consisting of: acid in the form of a gaseous acid (which may be the acid or a further additional acid), reductants, or oxidants. Notwithstanding the above, in a preferred form of the invention, the fluidising gas includes, consists of, or consists essentially of the inert gas and the acid. Preferably, the concentration of the acid in the fluidising gas is from about 0.00001 % (v/v) to 99.99999%. In alternative forms of the invention, the fluidising gas includes, consists of, or consists essentially of the acid. Thus, in one or more embodiments, the amount of acid in the fluidising gas is from 0.0001 %(v/v) to 100%(v/v).

In an embodiment the fluidising gas includes the acid as a gaseous acid, and the method further includes: adjusting an amount of the acid in the fluidising gas and/or the residence time of the fluidising gas and/or a temperature of the converting step to alter a yield of levoglucosenone and/or substituted furans in the gaseous product.

In an embodiment of the first or second aspects, the acid is consumed in the process such that the gaseous product is substantially free of the acid. In an alternative embodiment, the gaseous product is condensed into a liquid phase and residual acid is neutralized.

In an embodiment of the first or second aspects, the step of converting the lignocellulosic biomass is conducted at a temperature of from about 200 °C up to about 700 °C. Preferably, the temperature is from about 225 °C. More preferably, the temperature is from about 250 °C. Most preferably, the temperature is from about 275 °C. The skilled person will appreciate that the temperature range may be from any one of the preceding temperatures. Alternatively, or additionally, it is preferred that the temperature is up to about 600 °C. More preferably, the temperature is up to about 550 °C. Even more preferably, the temperature is up to 500 °C. Still more preferably, the temperature is up to about 450 °C. Most preferably, the temperature is up to about 400°C. The skilled person will appreciate that the temperature range may be up to any one of the preceding temperatures.

In an embodiment of the first or second aspects, the step of converting the lignocellulosic biomass is conducted at an absolute pressure of from about 0.9 atm up to about 2 atm. Preferably, the absolute pressure is from about 0.9 atm to about 1.5 atm. More preferably, the absolute pressure is about 1 atm.

In an embodiment of the first or second aspects, the step of converting the lignocellulosic biomass is conducted at ambient pressure.

A variety of different acids may be used in accordance with the aspects disclosed herein. By way of example the acid may be a mineral acid, an organic acid, a Lewis acid, or an acid that can donate at least one proton and at least one halide. The acid may be in gaseous phase, liquid phase, or solid phase. Notwithstanding the above, it is preferred that the acid is a mineral acid or an acid that can donate at least one proton and at least one halide. More preferably, the acid is a mineral acid that can donate at least one proton and at least one halide. Examples of preferred acids include: HBr, HCI, or HI.

It will be appreciated that the acid may be introduced into the multiphase reactor via a number of different mechanisms. In one form of the invention, the lignocellulosic biomass is premixed with the acid prior to being fed into the multiphase reactor. In another form, the acid is introduced, such as in liquid or gaseous form, via an acid inlet such that the step of converting the lignocellulosic biomass includes an initial step of contacting the lignocellulosic biomass with the liquid or gaseous acid. In still another form, the acid is introduced as a gaseous acid with the fluidising gas.

In one of more embodiments of the first or second aspects, a molarity of the acid in the fluidising gas is from about 5 x 10 ⁴ up to about 1 x 10 ¹ _. Preferably, the molarity is from about 6 x 10 ⁴ . More preferably, the molarity is from about 8 x 10 ⁴ . Most preferably, the molarity is from about 1 x 10 ³ . The skilled person will appreciate that the molarity range may be from any one of the molarities. Alternatively, or additionally, it is preferred that the molarity is up to about 1 .5 x 10 ² . More preferably, the molarity is up to about 1 x 10 ² . Most preferably, the molarity is up to about 8 x 10 ³ . The skilled person will appreciate that the molarity range may be up to any one of the preceding molarities.

In an embodiment of the first or second aspects, the multiphase reactor is selected from the group consisting of: a fluidised bed reactor, a fixed or packed bed reactor, a bubble column reactor, or an entrained flow reactor. In one form of this embodiment, the reactor zone includes a bed material. Preferably, the bed material is selected from an inert bed material (such as sand, silica, or glass) or a catalytic bed material (such as a metal halide, a metal oxide, a metal sulfate, a metal phosphate, a metal carbonate, a zeolite, a metal-organic framework, one or more of the foregoing, and nanoparticles thereof).

In an embodiment of the first or second aspects, the method further includes condensing the gaseous product to form a condensate including the levoglucosenone and the substituted furan.

In an embodiment of the first or second aspects, the substituted furan is selected from the group consisting of: 5-hydroxymethylfurfural, 5-bromomethylfurfural, 5- chloromethylfurfural, and 5-iodomethylfurfural.

In an embodiment of the first or second aspects, during the step of converting the lignocellulosic biomass, the lignocellulosic biomass is in contact with a solid catalyst. Preferably, the solid catalyst is selected from the group consisting of: a metal halide, a metal oxide, a metal sulfate, a metal phosphate, a metal carbonate, a zeolite, a metal- organic framework one or more of the foregoing, and nanoparticles thereof.

In one or more embodiments of the first and second aspects, the step of converting lignocellulosic biomass is a single step reaction for converting lignocellulosic biomass to the gaseous product including levoglucosenone and the substituted furan in the reaction zone.

It will be appreciated that the method may be performed as a continuous method, a batch method, or a semi-batch method. Similarly, the multiphase reactor may be a continuous multiphase reactor, a batch multiphase reactor, or a semi-batch multiphase reactor.

In a third aspect of the invention, there is provided a multiphase reactor configured to produce levoglucosenone and a substituted furan from lignocellulosic biomass according to the method previously described. Preferably, the multiphase reactor includes: a first inlet configured to introduce lignocellulosic biomass into the reactor, a second inlet configured to introduce a fluidising gas into the reactor, a reaction zone configured to fluidise the lignocellulosic biomass, and within which lignocellulosic biomass is in contact with an acid, wherein the reaction zone is located between the first inlet and the second inlet such that the fluidising gas flows from the second inlet and through the reaction zone to fluidise the lignocellulosic biomass, and an outlet configured to withdraw a gaseous product including the levoglucosenone and the substituted furan.

In a fourth aspect of the invention, there is provided an apparatus configured to produce levoglucosenone and a substituted furan from lignocellulosic biomass, the apparatus including: a multiphase reactor including: a first inlet configured to introduce lignocellulosic biomass into the reactor, a second inlet configured to introduce a fluidising gas into the reactor, a reaction zone configured to fluidise the lignocellulosic biomass, and within which lignocellulosic biomass is in contact with an acid, wherein the reaction zone is located between the first inlet and the second inlet such that the fluidising gas flows from the second inlet and through the reaction zone to fluidise the lignocellulosic biomass, and an outlet configured to withdraw a gaseous product including the levoglucosenone and the substituted furan.

In an embodiment, the multiphase reactor is configured such that the fluidising gas has a residence time in the multiphase reactor of 60 s or less. Preferably, the residence time is 40 s or less. More preferably, the residence time is 20 s or less. Even more preferably, the residence time is 10 s or less. Most preferably, the residence time is 5 s or less.

In an embodiment, the reaction zone is configured to operate at a temperature of from about 200 °C up to about 700 °C. Preferably, the temperature is from about 225 °C. More preferably, the temperature is from about 250 °C. Most preferably, the temperature is from about 275 °C. The skilled person will appreciate that the temperature range may be from any one of the preceding temperatures. Alternatively, or additionally, it is preferred that the temperature is up to about 600 °C. More preferably, the temperature is up to about 550 °C. Even more preferably, the temperature is up to about 500 °C. Still more preferably, the temperature is up to about 450 °C. Most preferably, the temperature is up to about 400°C. The skilled person will appreciate that the temperature range may be up to any one of the preceding temperatures.

In an embodiment, the reaction zone is configured to operate at an absolute pressure of from about 0.9 atm up to about 2 atm. Preferably, the absolute pressure is from about 0.9 atm to about 1.5 atm. More preferably, the absolute pressure is about 1 atm.

In an embodiment, the multiphase reactor is selected from the group consisting of: a fluidised bed reactor, a fixed or packed bed reactor, a bubble column reactor, or an entrained flow reactor. In an embodiment, the apparatus further includes a condenser configured to receive the gaseous product from the outlet of the multiphase reactor, and to condense the gaseous product into a condensate including the levoglucosenone and the substituted furan.

In an embodiment, the multiphase reactor further includes a solid catalyst. Preferably, the solid catalyst is selected from the group consisting of: a metal halide, a metal oxide, a metal sulfate, a metal phosphate, a metal carbonate, a zeolite, and a metal-organic framework.

In a fifth aspect of the invention, there is provided levoglucosenone and/or a substituted furan formed according to methods and/or an apparatus of the invention.

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 the drawings

Figure 1 : Schematic of a multiphase reactor system.

Figure 2: Schematic of the fluidised bed reactor system used in examples.

Figure 3: Schematic for the apparatus used for verifying the liberation of HCI(g) and measuring its flow rate.

Figure 4: Calibration curve for estimating Cl ion concentration.

Figure 5: Chromatogram depicting elution of chloride ion.

Figure 6: Calibration curve for quantifying the concentration of Levoglucosenone.

Figure 7: Calibration curve for quantifying the concentration of 5- Chloromethyl furfural.

Figure 8: Typical standard run depicting elution of Levoglucosenone. Figure 9: m/z peaks of LGO standard also confirmed through the National Institute of Standards and Technology (NIST) library.

Figure 10: Standard run depicting elution of 5-Chloromethyl furfural.

Figure 11 : m/z peaks of 5-CMF standard (144, 109,81 ,53).

Figure 12: Thermal conversion of lignocellulosic biomass: Effect of temperature on selected chemicals.

Figure 13: Thermal conversion of cellulose: Effect of temperature on selected chemicals.

Figure 14: Chromatogram for thermal conversion of lignocellulosic biomass.

Figure 15: Chromatogram for thermal conversion of cellulose.

Figure 16: Comparison of thermal (left chromatogram) and thermo-catalytic conversion (right chromatogram) of lignocellulosic biomass. The catalytic effect of acid boosts the amount of furfural and levoglucosenone in the liquid. The acid plays a role of co-reactant in the formation of 5-Chloromethyl furfural.

Figure 17: Thermo-catalytic conversion of lignocellulosic biomass: Effect of temperature on the concentration of Levoglucosenone and 5-Chloromethyl furfural.

Figure 18: Chromatogram obtained during the thermocatalytic conversion of lignocellulosic biomass 350°C.

Figure 19: m/z peaks for 5-Chloromethyl furfural obtained after thermo- catalytic conversion of lignocellulosic biomass.

Figure 20: m/z peaks for Levoglucosenone obtained after thermo-catalytic conversion of biomass.

Figure 21 : General reaction scheme for the formation of Levoglucosenone and 5-Chloromethyl furfural during thermo-catalytic conversion of lignocellulose.

Figure 22: Effect of concentration of acid on yield of Levoglucosenone and 5- Chloromethyl furfural. Figure 23: Effect of acid concentration on thermo-catalytic conversion of cellulose.

Figure 24: A chromatogram obtained during the thermo-catalytic conversion of cellulose at 450 °C in a fluidised bed reactor.

Figure 25: A graph showing the effect of temperature on the concentration of chemicals in condensate liquid obtain after thermo-catalytic conversion of cellulose in fluidised bed reactor.

Detailed description of the embodiments

The invention relates to methods and apparatus for producing levoglucosenone and a substituted furan from lignocellulosic biomass in a multiphase reactor. The method includes converting lignocellulosic biomass, in contact with an acid within the multiphase reactor, to a gaseous product including levoglucosenone and a substituted furan in a reaction zone of the multiphase reactor.

The inventors are not aware of any current large scale manufacturing process for levoglucosenone and substituted furans. Levoglucosenone is an attractive molecule for the production of pharmaceuticals and commodity chemicals like 1 ,6 hexane diol. Its reduction yields dihydrolevoglucosenone that can be used as green solvent in pharmaceutical industry. 5-Chloromethyl furfural is an analogue of 5-Hydroxymethyl furfural (5-HMF) and finds application in polymer, pharmaceutical and commodity chemicals industry.

The method of the invention advantageously provides, in one or more embodiments, a thermo-catalytic process for the production of these chemicals of commercial interest from lignocellulosic biomass in one step. Furthermore, the method of the invention provides the ability to alter the yield of levoglucosenone and the substituted furan by changing the acid concentration and reaction residence time.

The term“levoglucosenone” is intended to refer to 1 ,6-anhydro-3,4-dideoxy-p-D- pyranosen-2-one. The chemical structure of levoglucosenone is represented by Formula I:

Formula I

The term“substituted furan” is intended to refer to any furan that includes one or more substituents. However, preferred substituted furans include furfurals such as those represented by Formula II:

Formula

Particularly preferred substituted furans include halomethylfurfurals, hydroxymethylfurfurals, and furfural. More preferably, the substituted furans are 5- halomethylfurfurals (such as 5-chloromethylfurfural, 5-bromomethylfurfural, 5- iodomethylfurfural), 5- hydroxymethylfurfurals, and fufural.

The term“lignocellulosic biomass” is intended to refer to biomass material that includes both lignin and cellulose. Lignocellulosic biomass may also include cellobiose, hemicellulose, polysaccharides and monosaccharides like glucose, fructose, xylose and other C6 sugars like maltose, lactose, sucrose, galactose and their isomers. Examples of biomass include, but are not limited to, softwood, hardwood, bark, municipal solid waste, agricultural waste, greens, bagasse, corn grain, corn cobs, crop residues such as corn husks, corn stover, grasses, wheat, wheat straw, barley, barley straw, hay, rice straw, switchgrass, paper (including cardboard, kraft paper, pulp, containerboard, linerboard, corrugated container board), sorghum, soy, components obtained from milling of grains, trees, branches, roots, leaves, wood chips, sawdust, shrubs and bushes, vegetables, fruits, and flowers, or a combination thereof. The lignocellulosic biomass may be derived from a single source, or biomass can comprise a mixture derived from more than one source. Figure 1 provides a general schematic of a multiphase reactor system according to the present invention, or for use in the methods of the invention. The system 100 includes a multiphase reactor 102. During operation, a lignocellulosic biomass 104 is fed into the reactor 102 through an inlet in an upper portion of the reactor 102 and a fluidisation gas including an inert gas 106 and an acid gas 108 is fed into the reactor 102 via an inlet in a lower portion of the reactor 102. The fluidisation gas fluidises the lignocellulosic biomass in a reaction zone 1 10 of the reactor under reaction conditions (temperature, pressure, a fluidisation residence time). During this fluidisation step, acid gas in the fluidisation gas contacts the lignocellulosic biomass and catalyses the conversion of a portion of the lignocellulosic biomass to levoglucosenone and reacts with another portion of the lignocellulosic biomass to produce a substituted furan. A gaseous product, including volatile compounds (which volatile compounds include at least levoglucosenone and the substituted furan) is withdrawn from the reactor 102. The volatile compounds (including the levoglucosenone and the substituted furan) are condensed in a condenser 112 and are withdrawn for separation/purification as required. The non-condensable fraction of the fluidisation gas may be recycled or may be neutralised 114 and then vented 116. The amount of acid, residence time of the fluidisation gas, and/or reaction temperature may be controlled to adjust the amount of levoglucosenone and/or substituted furan in the gaseous product.

Example 1

Experimental method

Feedstock

Softwood (Pinus radiata) and cellulose (Cat#11365- Avicel- PH 101 ) were used as feedstock in this example. The proximate analysis and composition of lignocellulosic biomass are shown in Table 1 and Table 2 respectively. Table 1 : Proximate analysis of softwood sample used in this study

* ¹ : ad is air dried

Table 2: Compositional analysis of Pinus radiata

Fluidised bed reactor

The schematic of the quartz fluidised bed reactor used in this example is shown in Figure 2. The reactor has an outer diameter of 40 mm, thickness of 2mm and length of 560 mm. The reactor is mounted on a connector attached to a flask. The flask is used for generating HCI (g) and channelling the inert gas for fluidisation into the reactor. The top port of the reactor is for feeding lignocellulosic biomass (<800 pm) and cellulose. Sand (< 180 pm) was used as the fluidising medium. The minimum fluidisation velocity was calculated using Wen and Yu model and was verified by cold flow experiments. Cold flow experiments were conducted to determine the actual velocity (and inlet volumetric flow rate) of the inert gas required for achieving bubbling bed fluidisation.

Generation of HCI(g) Hydrogen chloride gas was generated using anhydrous granular calcium chloride (Cat# C1016, Sigma-Aldrich) and aqueous (25wt%) hydrochloric acid. The 25 wt% aq. HCI was prepared by diluting 36wt% aq. HCI (Cat# RP1106, RCI Labscan) in deionised water. The volumetric flow rate of the HCI(g) produced from this reaction was determined using bubble meter. Figure 3 shows the schematic of the apparatus used for confirming the generation of HCI(g) and later estimating its volumetric flow rate using bubble meter. Total yield of HCI(g) obtained from this reaction was determined using ion-chromatography. The calibration curve (Figure 4) for chloride ion concentration was established using different dilutions of chloride ion standard (Cat# 39883, Sigma-Aldrich; TraceCERT®, 1000 mg/L chloride in water). The dilution scheme used to prepare the standards is shown in Table 3. Ultrapure water was used as the diluent for standards and samples. Figure 5 shows the typical chromatogram obtained for chloride ion.). The amount of chloride ion was determined using Metrohm 881 Compact IC Pro- Anion equipped with Metosep A Supp 5-150.4.0 column (inner diameter: 4 mm; length: 150 mm; particle size: 5pm). The eluent composition was 1 mM NaHC0 ₃ /3.3mM Na ₂ C0 ₃ and flow rate was 0.7 mL/min.

Table 3: Dilution scheme used for generating calibration curve for chloride ion

Gas-Chromatography Mass Spectrometry

Perkin Elmer Gas Chromatograph Mass Spectrometer (Clarus 600) equipped with Elite 5MS column (30 m x 0.25 mm IDx0.25 pm film) was used for the analysis of the liquid sample obtained after conversion. Ultra-high purity helium gas (99.999%) was used at 1.0 mL/min as a carrier gas. The injector was maintained at 300°C and the temperature of source and transfer line was set at 280°C. A split ratio of 50:1 and injection volume of 2.5pL was used. The GC oven was programmed as follows: Initial temperature of 40°C for 3 mins, followed by a ramp of 10°C/min until 280°C and final hold for 5 mins at 280°C. The ionization energy of 70 eV was used for scanning the electron range (m/z) of 20-350 amu.

NIST library was used for identifying compounds. Additionally, standards of 5- CMF (Cat#C369220) and Levoglucosenone (Cat#L375000) were purchased from Toronto Research Chemicals. A calibration curve was generated for these two compounds based on the peak area values obtained from GCMS analysis. This calibration curve was used for quantifying the concentration of these two chemicals in the liquid produced from thermal and thermo-catalytic conversion of lignocellulosic biomass. Figure 6 and Figure 7 show the calibration curves used for quantifying the concentration of Levoglucosenone and 5-CMF respectively. Figure 8 and Figure 9 show the chromatogram and m/z peaks respectively obtained from LGO standard. The chromatogram and m/z peaks for 5-CMF are shown in Figure 10 and Figure 11 respectively.

Results and Discussion

Safe generation of HCI (g) for laboratory scale fluidised bed reactor

This experiment was performed to verify the liberation of HCI(g) when 25 wt% aq. HCI is added to anhydrous calcium chloride granules. A total of 35 ml_ of 25 wt% aq. HCI was added to 30 g of anhydrous calcium chloride. The gas generated as per the reaction described in experimental section, was directly dissolved in 150 ml_ of 1 N sodium hydroxide solution. The reaction was conducted for 15 minutes. This solution was diluted to estimate the chloride ion concentration. All the dilutions and solutions were prepared using ultrapure water. The calibration curve chloride ion is shown in Figure 3 . The yield of HCI(g) was calculated as follows:

Amount of HCI in 35 ml_ of 25 wt% aq. HCI (Density: 1.12 g/ml_): 9.63 g

Concentration of Cl ion determined using ion chromatography: 30000 mg/L

Yield of HCI: (Volume of solution x Cone of Cl ion in the solution)/(Amount of HCI in aqueous HCI): 46.72%.

This experiment verified the evolution of HCI(g) through dehydration effect of anhydrous calcium chloride granules. The next step was to determine the flow rate of the HCI(g) evolved from this reaction. The average flow rate of the gas was determined to be 2.5 litres per minute (Ipm) using bubble meter when the internal flask temperature was 70°C and the 1 Ipm when the flask was maintained at ambient temperature.

Operation of laboratory scale fluidised bed reactor

The reactor and the bed were heated to the desired temperature using a heating tape in this example. The temperature of the bed was also measured using an additional thermocouple before performing the reaction. Prior to feeding, the entire reactor system along with auxiliary units (flask, feeder and quencher) was purged with nitrogen gas for 10 minutes. Immediately after batch feeding (a total of 5 g), the inert gas and hydrogen chloride were supplied to the reactor for achieving bubbling bed fluidisation. A total volumetric flow rate of 10 Ipm (2.5 Ipm of HCI and 7.5 Ipm of nitrogen) was used for lignocellulosic biomass. The volumetric flow rate of nitrogen was varied to investigate the effect of acid concentration on the concentration of the chemicals in the liquid. Only nitrogen gas was used for achieving bubbling bed fluidisation during thermal conversion of lignocellulosic biomass and cellulose. The volatiles generated from the reaction were quenched in the condenser maintained at sub-zero temperature using dry ice. Short connecting tubes were used between the reactor and the condenser to facilitate quick quenching of volatiles. The residual HCI(g) used for thermo-catalytic conversion was passed through 1 N NaOH solution and the light gases were vented into the atmosphere. The reactor was operated for primarily analysing effect of HCI, its concentration and temperature on the composition of the liquid (regardless of its yield; the typical liquid recovery was between 0.5-2.5 ml_). The residence time (Reactor length from frit to outlet/ velocity) of the volatiles in the reactor was between (0.5-1 ) s.

Thermal conversion of lignocellulosic biomass and cellulose in bubbling fluidised bed reactor

The effect of temperature on the composition of the liquid obtained after thermal conversion was investigated between 300-500°C as majority of the chemical changes occur in that range. Figure 12 and Figure 13 show the relative amounts of Levoglucosenone, Furfural and 5-Hydroxymethyl furfural produced from lignocellulosic biomass and cellulose respectively at different temperature. The peak area corresponds to the concentration of the chemical in the liquid. Direct thermal conversion of lignocellulosic biomass and cellulose in bubbling fluidised bed reactor produces plethora of chemicals. In case of cellulose, Levoglucosenone is produced at all the temperatures from 300 to 500°C. The concentration of Levoglucosenone decreases at higher temperature. No clear trend is observed for 5-HMF but higher amount of furfural is formed at 400°C and 450°C. In case of lignocellulosic biomass, Levoglucosenone is produced at 300 and 350°C. Furfural formation is observed at 300°C whereas 5-HMF is produced across temperatures from 300-500°C. The higher concentration of 5-HMF in the liquid obtained from thermal conversion of lignocellulosic biomass can be attributed to the hemicellulose. 5-HMF is produced from cellulose and hemicellulose during thermal conversion of lignocellulosic biomass. Formation of Levoglucosenone and Furfural from lignocellulosic biomass is inhibited at higher temperature due to radical scavenging activity of lignin that prevents dehydration reaction. The typical chromatogram obtained from thermal conversion of lignocellulosic biomass and cellulose are shown in Figure 14 and Figure 15 respectively. This suggests that thermal conversion of lignocellulosic biomass and cellulose to chemicals in bubbling fluidised bed reactor is a function of temperature.

Thermo-catalytic conversion of lignocellulosic biomass

Flydrogen chloride gas was used as catalyst cum co-reactant in thermo-catalytic conversion of lignocellulosic biomass in bubbling fluidised bed reactor. There were two major objectives of this part of the study: a) feasibility of formation of 5-CMF from lignocellulosic biomass in bubbling fluidised bed reactor using hydrogen chloride gas as a co-reactant; b) catalytic effect of hydrogen chloride gas on concentration of other chemicals such as levoglucosenone.

Figure 16 shows that hydrogen chloride gas has three main effects: it produces 5-CMF; boosts the concentration of levoglucosenone; makes the process more selective. The qualitative definition of selectivity in this context is defined as ratio of the amount of desired chemical in the liquid (5-CMF and levoglucosenone) when HCI(g) is used to the amount when HCI(g) is not used in the process. The peak area for Levoglucosenone obtained from thermal conversion of lignocellulosic biomass at 350 °C corresponds to a concentration of ~0.8 g/L of liquid. It is not seen in the liquid obtained from thermal conversion of lignocellulosic biomass at higher temperature. The usage of HCI(g) boosted the concentration of Levoglucosenone at 350°C to ~19g/L. It is also formed at higher temperature in the presence of HCI(g) (see Figure 17). Usage of HCI(g) in the process results in production of fewer chemicals in high concentration as opposed to conventional thermal conversion wherein plethora of chemicals are produced in low concentration. Formation of few chemicals in high concentration through this process advantageously simplifies the purification of these compounds at commercial scale.

Figure 17 shows the effect of temperature on the concentration of selected chemicals during thermo-catalytic conversion. Figure 18 shows the typical chromatogram obtained during thermo-catalytic conversion of lignocellulosic biomass.. The m/z peaks confirm the identity of 5-CMF (Figure 19) and LGO (Figure 20).

The concentration of Levoglucosenone and 5-CMF is higher at 350 °C and 400 °C respectively. Majority of the breakdown of cellulose and hemicellulose is known to occur between 300-400 °C. Presence of gaseous acid promotes the dehydration reaction and increases the concentration of Levoglucosenone. 5-CMF is produced through the reaction between HCI(g) and cellulose and C6 sugars in hemicellulose undergoing isomerisation followed by dehydration. HCI(g) in this case acts as both catalyst for dehydration and co-reactant for the formation of 5-CMF. The catalytic effect and reaction of hydrogen chloride gas with cellulose and hemicellulose that forms 5- CMF and also increases the amount of furfural in the liquid obtained after conversion. A general scheme for the formation of levoglucosenone and 5-HMF from cellulose is shown in Figure 21.

Effect of acid concentration on the concentration of levoglucosenone and 5-CMF

This section describes the effect of concentration of acid on the concentration of Levoglucosenone and 5-CMF. Figure 22 shows the influence of acid concentration (v/v %) on the concentration of 5-CMF and Levoglucosenone in the liquid. The low concentration of acid (12.5 (v/v)%) produces low amount of Levoglucosenone and 5- CMF. As the concentration of acid increases (25% (v/v)) the concentration of LGO and 5-CMF increases further and saturates. A further increase in concertation of acid increases the yield of both 5-CMF and Levoglucosenone. Increasing the concentration beyond 62.5 (v/v) % is more favourable for 5-CMF than LGO. The corresponding molarity of the gaseous HCI is also represented in the graph. The molarity of HCI (no of moles(n)/Total volume of gas(V)) was calculated using ideal gas law. The phenomenon of increasing concentration of acid on the yield of Levoglucosenone is in agreement with previous studies done using aqueous mineral acids. However, the higher diffusivity of gaseous acid results in stronger penetration of low molarity gas into the lignocellulosic biomass for both catalytic dehydration and reaction. The increasing amount of acid increases the yield of 5-CMF further as there is more HCI (g) available to react and convert cellulose component of wood and C6 sugars of hemicellulose to 5-CMF. The bubbling bed fluidisation of lignocellulosic biomass was satisfactorily achieved in the reactor. Cellulose, being lighter and smaller, was observed to elutriate at high volumetric flow rates of gas (>6.5 Ipm). Thus, the effect of concentration of acid on thermo-catalytic conversion of cellulose was studied for lower volumetric flow rates. Figure 23 shows similar trend for cellulose as it is observed for lignocellulosic biomass.

Summary

The inventors have demonstrated the thermo-catalytic conversion of lignocellulose to levoglucosenone and 5-CMF in fluidised bed reactor using HCI(g) as catalyst cum co-reactant. The results show that usage of gaseous HCI produces 5-CMF from lignocellulose. It catalyses the dehydration reaction and increases the yield and selectivity of levoglucosenone. Its catalytic activity also promotes the formation of furfural. In this study, the highest concentration of levoglucosenone (~19 g/L) was obtained at 350 °C and that of 5-CMF was obtained at 400°C. Flowever, the yield of 5- CMF was observed to be proportional to the amount of acid used in the process. The results suggest that it is possible to obtain higher concentrations of 5-CMF (~ 15g/L) using higher concentrations of acid. The yield of levoglucosenone and 5-CMF was found to be a function of temperature and acid concentration. Higher concentration of gaseous HCI was favourable for 5-CMF formation. The overall concentration of acid (molarity) used in this process was very low.

Example 2

This example reports results for the thermo-catalytic conversion of cellulose in a fluidised bed reactor to levoglucosenone and 5-chloromethylfurfural.

Figure 24 shows the chromatogram for thermo-catalytic conversion of cellulose at 450 °C in a fluidised bed reactor.

Figure 25 shows the effect of temperature on the concentration of chemicals in condensate liquid obtain after thermo-catalytic conversion of cellulose in fluidised bed reactor

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.