INTRODUCTION Field of the Invention

The invention relates to processing of biomass, cellulosic material, natural materials containing biopolymers of largely C5 and or C6 sugars, generally referred to in this specification as "lignocellulose".

The production of fuels and other chemicals from cellulosic biomass has received much attention in recent years as a means to reduce the carbon footprint from fossil fuels and world-wide dependency on oil. First generation bio-refining operations use largely grain crops to produce sugars which were converted to bio-ethanol through fermentation but these activities compete with food production and are not sustainable. Second and third generation bio-refineries are intended to use non-food biomass sources namely lignocellulosic renewable energy crops or wastes such as miscanthus, corn stow over and wood waste for saw mills among others to produce sugars and ultimately compounds that can be employed as fuels, fuel additives and or platform starting materials for the production of valuable chemicals. Typical lignocellulosic materials comprise three substantial biopolymer components, cellulose, hemi-cellulose and lignin. In second and third generation bio-refining operation the holo-cellulose, polymers of six and five carbon sugars, are hydrolysed, usually under acidic conditions at elevated temperature or through enzymatic fermentation, sequentially to oligomers and sugars. In chemical refineries these sugars are converted to either Levulinic Acid (LA) or Furfural (FUR) respectively with a number of other intermediates being formed in the sequence such as Hydroxy-Methyl-Furfural (HMF) while in fermentation the sugars are converted to ethanol and other chemicals such as sussinic acid. In the case of chemical hydrolysis all reactants along the sequences ending in LA and FUR are known to undergo less desirable parallel reactions to form condensation products similar in composition to humins under typical acid hydrolysis conditions reducing the yields achievable. The lignin content of biomass is generally less amenable to degradation (particularly under acid conditions) than the polymeric sugars and is considered a less valuable by product of the process. Second and third generation bio-refineries seek to incorporate multiple operations and strive to utilise all components of the biomass including the lignin such as for example through combined heat and power plants to combust it once separated from the sugar content making use of its higher heating value to supply energy or through gasification and pyro lysis operations to produce bio-oils and or bio-char for use as a soil amender and carbon recycling. In addition if fractionated from the biomass several other lignin uses are under investigation including the production of fuels and polymers therefrom.

Chemical acid hydrolysis of lingocellulose materials fall into two major categories, those employing concentrated and dilute acids respectively. The former produce high sugar yields but the economic costs associated with speciality equipment that can withstand the acid concentrations are a major draw back of such processes. Dilute acid hydrolysis circumvents these limitations to some extent but generally achievable yields of sugars are lower as the sugars readily degrade to less useful products under the hydrolysis conditions particularly when exposed to the acid medium for longer periods at higher temperatures. When compared with food substrates the hydrolysis of lingo-cellulose biomasses is complicated by the association between the holo-cellulose components and the lignin in the plant structure rendering these materials recalcitrant (less amenable to degradation). As a consequence practically all processes to hydrolyse lignocellulose whether through a chemical of fermentation process will involve pre-treatment and much of the energy and cost input to bio-refineries is associated with disassociating the holo-cellulosic and lignin content so that the cellulose can be accessed whether by the acid medium or the enzymes respectively. Many pre-treatment processes are employed to achieve this including physical, chemical and enzymatic pre-treatments and while operating on different principles all effect the overall economic efficiency of a biorefining process either directly or through there influence on the number and type of down stream operations.

Physical pretreatments for the conversion of Lignocellulose include ball milling, knife milling and the like, the resulting reduction in the particle size and or the crystallinity of the cellulose content increasing the surface area available for enzymatic or chemical attack in subsequent hydrolysis operations and generally rendering the lignocellulose more amenable to digestion. Studies on various biomasses and indeed pure cellulose compounds have shown that below a particle size of approx 800 micron the rate of cellulose acid hydrolysis is purely kinetic and that mass transfer is not limiting implying that the expenditure of energy in physical processes to reduce the particle size beyond this minimum is wasteful [1]. In addition the cost of physical commutation operations is expensive given the capital and operational costs involved and particularly as this mechanical energy input is not readily recovered for reuse. Enzymatic or biological pretreatments involve exposing the lignocellulose to organisms including actinomycetes and other fungi that secrete extracellular enzymes (lignin peroxidases and lactases) that preferentially degrade the lignin content rendering the remaining cellulosic biomass more amenable to hydrolysis. While Biological pretreatments are low energy intensive processes they require long residence times of the order of tens of days, are highly susceptible to changes in their environment (conditions of temperature and ph, substrate composition, the presence of components that are toxic to the micro-organisms etc) and consume a fraction of the sugar content to sustain their growth reducing achievable yields of sugars and chemicals derived there from down stream. In addition the microbial or fungal biomass in the resulting mixtures must be separated from the sugar or holo-cellulose containing liquor introducing additional process operations with added operational and capital cost implications.

From the point of view of scaled up commercial operations for lignocellulose hydrolysis chemical pretreatments would appear the most attractive. These include solvent fractionation, dilute acid hydrolysis, explosion pretreatments, high temperature liquid water pre-treatment, alkaline extraction, oxidative pretreatments and various elements of these different pretreatments in combination.

Solvent fractionation

Solvent fractionation pretreatments include the Organosolv process (for example HALLBERG et al WO/2008/144878) in which the lignocellulose material is exposed to organic solvents (usually alcohols) under acidic conditions at temperatures in the range 90-220°C for periods varying from minutes to hours depending on the recalcitrance of the starting biomass. The process is intended to produce an insoluble cellulose fraction that is rendered more amenable to digestion by subsequent chemical or enzymatic hydrolysis. The hemi-cellulose, lignin and other extractives are dissolved in the liquid organic phase which can be separated from the cellulosic content for further processing. The process requires the input of heat and the use of expensive solvents which must be recovered and recycled through the construction of additional unit operations. Proportions of the hemicellulose are also converted to furfural analogues as well as oligosaccarides and sugars under the acidic conditions and these compounds are known to be toxic to micro-organisms used in fermentation processes requiring that the furanic components as well as the acid and solvents be removed from the resulting cellulose if intended for subsequent enzymatic hydrolysis to produce ethanol.

A fractionation process employing multiple extraction steps with various solvents including mineral acids and organic solvents to produce an amorphous cellulose for subsequent hydrolysis in a fermentor is disclosed by ZHANG, in WO/2007/111605. The process while requiring moderate temperatures requires multiple unit operations to separate components and recover the process chemicals.

More recently the use of ionic liquids has been proposed for the fractionation of lignocellulose biomass as for example in US patent application no. US20100163018 to Gifford et al. ionic liquids are ionic compounds usually with organic cations that are liquid at room to moderate temperatures. Depending on the temperature, duration of exposure and the nature of the ionic liquid used these solvents can preferentially dissolve hemi-cellulose and lignin from lignocellulosic biomass facilitating fractionation or dissolve the entire biomass including the cellulose. Ionic liquids of use in the solubilisation of lignocellulose biomass include alkylated imadizaloium chlorides, bromides, fluoro-phosphonates and sulphonates among others. The main drawback with the use of ionic liquids is that they are a costly input to the process and require the addition of unit operations for recovery and recycling. The more effective compounds contain anions of halogen compounds that may not be environmentally optimum in the context of an overall biorefining operation where even trace concentrations introduced to pyrolysis or combustion operations is not desirable. Aqueous solutions containing Lewis acids that operate to disrupt the lignocellulose bonding in a similar manner to ionic liquids have also been disclosed (e.g. US20100004437 to Binder et al) as effective pretreatment technologies for fractionation, including the aluminium and chromium salts of chlorine and other halogens. These materials however may be less than environmentally optimal for the same reasons discussed above. Dilute acid hydrolysis

Dilute acid hydrolysis has been employed for the preferential hydrolysis of hemicellulose and partial solubilisation of lignin prior to further treatments typically with temperatures in the range 100- 220°C, and mineral acid concentration up to 10% by mass and solid loadings up to 30%. A severity index, called the combined severity factor (CSF) has been defined, [2] being representative of the acidic concentration, temperature and duration of exposure to a given set of conditions. At lower severity factors hemicellulose is dissolved to oligosaccharides and sugars that can be removed from the cellulose component. With increasing severity factor the hemicellulose components will be hydrolysed to furfural as will the cellulose be sequentially hydrolysed to lower molecular weight oligomers, glucose, HMF and ultimately Levulinic acid. In biorefineries directed toward the production of a cellulosic feedstock for fermentors the lower severity factor will be chosen to remove the hemicellulose and partially solubilise the lignin by converting it to lower molecular weight lignols, the resulting cellulosic material must be washed of acid, and furanic compounds prior to fermentation. Where the biorefinery is directed toward the production of platform chemicals such as FUR and LA, prolonged exposure of the lignocellulosic material to acid medium at high temperatures (high CSF) will also result in the hydrolysis of the hemi-cellulose and cellulose to FUR and LA respectively. Fitzpatrick EP 19890905916 discloses a continuous two stage reactor system employing dilute acid hydrolysis for the complete conversion of lingocellulose to FUR and LA comprising subjecting lignocellulose to acid concentrations between 2% and 7% at high temperature >200°C in a first plug flow reactor for less than a minute. A subsequent pressure drop in a flash vessel removes a large portion of the hydrolysed hemicellulose content as FUR in the gas phase, while the liquid phase containing the now more digestible cellulose and lignin is fed to a second reactor operating at lower temperatures and longer residence times where the cellulose is converted to LA. Based on kinetic studies by Girisuta et al on pure cellulose degradation the reduced temperature of the second reactor is expected to favour the conversion of cellulose to glucose and LA as opposed to the condensation products that are known to form from these substrates via undesirable parallel reactions under acidic conditions [1]. The short residence times at high temperature needed to reduce the recalcitrance of the starting material is achieved through direct steam injection which facilitates very rapid heating. Dilute acid hydrolysis requires physical commutation to reduce mass transfer dependencies on the reaction rates and in the case of the two stage process of Fitzpatrick the provision of high pressure steam at greater than 30 bar. In addition, the combination of high temperature and low pH is severe on process equipment. Importantly, the presence of high concentrations of acid in the digested liquor and the lignin residues must be neutralised to facilitate further processing including optimum LA extraction. U.S. Patent No. 4,515,816 to Anthony is directed to a process in which lignocellulose is treated with dilute acid in an amount of about 1.5 to 2.5% of the dry weight of lignocellulose. The mixture is the stored at ambient conditions for 5 to 21 days in an air-free environment.

Alkaline treatments

Alkaline treatments borrow from the paper industry where alkaline and oxidative media are extensively used to bleach cellulose for paper production. In general cellulose is not hydrolysed to any great extent when exposed to alkaline conditions provided the pH is not too high or the duration of exposure not too long. However lignin is degraded to lower molecular weight lignols soluble in alkaline aqueous solution. WO/1994/003646 to Holtzapple discloses an alkaline pretreatment using calcium hydroxide and oxygen at high pressure in the pH range 8-10.5 resulting in a delignified cellulosic solid phase and a liquid phase containing dissolved lignin and hemicellulose. US4644060 to Chou is directed to the use of super critical ammonia to increase lignocellulose digestibility. US3878304 to Moore is directed to using an amide where urea is reacted with waste carbohydrates in the presence of an acid catalyst.

US3, 944,463 to Samuelson et al. is directed to a process for producing cellulose pulp of high brightness. The cellulose is pretreated with an alkaline compound (sodium carbonate, sodium bicarbonate or mixtures thereof) at a temperature of between about 60°C to about 200°C so as to dissolve between 1 and 30% of the dry weight of the material in the pretreatment liquor. US4,048,341 to Lagerstrom et al. is directed to a process for increasing the feed value of lignocellulosic material by contacting the material with an alkaline liquid, specifically, sodium hydroxide.

US4, 182,780 to Lagerstrom et al. is directed to a process for increasing the feed value of lignocellulosic materials by alkali treatment and subsequent neutralization of the materials with an acid in a closed system under circulation of the treating agents. US4113553 to Samuelson is directed toward a process for pulping hardwood to produce cellulose using sodium sulfide at a pH of about 10.5 to about 13 at temperatures in the range 110° to about 170°C. Hydrogen sulfide is generated in situ by reaction of sodium sulfide with organic acids liberated in the pulping process.

Steam Explosion Many treatments have been investigated which involve preheating crude lignocellulose at elevated temperature for enzymatic hydrolysis to sugar that fall under the general heading "steam explosion". Generally the biomass is heated with water to elevated temperature in a batch reactor or by direct steam injection and the resulting pressure is rapidly released resulting in an explosive escape of the biomass which breaks the cellulose into a fiberous form that is more readily hydrolysed either by enzymes or acid. Mason describes steam cooking processes for wood in U.S. Patent numbers 1824221, 2645633, 2294545, 2379899, 2379890 and 2759856. These patents disclose an initial slow cooking at low temperatures to glassify the lignin, followed by a very rapid pressure rise and quick release resulting in a "fluffy", fibrous material commonly used in the manufacture of fibre boards and insulation.

The advantage of pure steam explosion is that the resulting liquors and cellulose do not require extensive neutralisation for use either as is or in subsequent fermentors. One variant of steam explosion for the treatment of lingo cellulose particularly intended for fermentation is liquid hot water. For example US4670613 to Ruyter et al involves a process in which the biomass is heated to high temperatures in the presence of water >300°C but the system is maintained at a pressure greater than 50 bar. The high pressures maximises the amount of water in the liquid phase to extract the hemicelluloses but the extent of lignin removal is less than ideal in the absence of acid or base. The high pressures involved in the process also reduce the conversion of the hemicelluloses to furanic compounds which can inhibit subsequent enzymatic hydrolysis.

Many variants on the steam explosion process exist including the use of acidified steam as well as alkaline steam. The former may be characterized as a variant of the weak acid hydrolysis process in which partial hydrolysis of holo-cellulose occurs during pre-treatment and the added explosive effect physically commutes the cellulose increasing available surface area and rendering it less recalcitrant. Such processes are proposed in U.S. Pat. Nos. 5125977, 5424417, 5503996, 5705369, and 6022419, to Torget, et al. and the two stage process of Fitzpatrick EP 19890905916, may also be considered in this category given the pressure drop between the first and second stage reactors.

Combining alkaline pre-treatments with explosion provides the added benefit of physically commuting the cellulose in addition to the alkaline degradation of the lignin content making it more accessible to degradation in subsequent steps. Wingerson et al. describe a multi zone reactor system in WO/2002/014598 involving the exposure of lignocellulose to an alkaline wash liquid having a pH between 8 and 13 at pressure and elevated temperature to remove lignin and hemicellulose with a subsequent flash (explosive pressure drop) to produce substantially pure cellulose with low lignin content.

The AFEX (Ammonia Fibre Expansion) pretreatment process soaks lignocellulose in liquid ammonia at high pressure and then explosively releases the pressure to increase accessible surface area and reduce cellulose crystallinity. Pre- treatment conditions (30°C - 100°C) are less severe than steam explosion. U.S. Patents 4356196 4600590, 5037663, 5171592, 6416621 and 6176176 among others disclose variations on the AFEX process. Ammonia does not produce by products that are toxic to ethanol producing microbes and is particularly suited to pre-treating biomass intended for fermentation but it is a costly chemical and hazardous to handle. Oxidative pre-treatments

Oxidising agents can be used to remove lignin and hemi-cellulose form lignocellulose biomass to produce cellulose that is more amenable to digestion. In the first instance and depending on the pH these oxidants may react selectively with the hemicellulose and or the alkyl and aryl linkages within the lignin breaking the polymer into lignols and dissociating it for the carbohydrate polymers. However prolonged exposure of the biomass to the oxidising environment particularly at elevated temperature can result in hemicellulose and cellulose degradation resulting in reduced sugar yields. Oxidants that have been used in the pre-treatment of lignocellulose biomass include air, oxygen, ozone, permanganate, sulphite and hydrogen peroxide. Many of the oxidising pretreatments are employed in the paper industry where the oxidation is carried out under alkaline conditions to prevent the degradation of the cellulose. An example of a process that utilises sulphites is the patent of Ingruber et al (US3630832) and an example of a patent utilizing ozone is US4451567 to Ishibasbi.

US3939286 to Jelks is directed to oxidizing biomass with high-pressure oxygen under elevated temperature and pressure in the presence of an acid catalyst, and a metal catalyst, to break lignin bonds and to increase digestibility. The catalysts are described as essential to the process and calcium hydroxide is utilized as a neutralizing agent to adjust the resulting pH of the hydrolyzed biomass for use as an animal feed.

US4,842,877 to Tyson is directed to a process for the delignification of non-woody biomass (<20% lignin). In this process, non- woody biomass is treated with a chelating agent, to prevent unnecessary oxidation, and maintained at alkaline, high pH and high temperature in the presence of hydrogen peroxide and pressurized oxygen. Hydrogen peroxide is stated to cause a reaction on the cell walls to allow the hemicellulose and lignin to solubilize and be removed through a subsequent hydrolysis process. Oxygen is added to initiate and accelerate the activation of hydrogen peroxide.

Most oxidation treatments incorporating hydrogen peroxide are carried out under alkaline conditions using relatively small amounts of peroxide (<5% by mass) as its oxidising strength is high under alkaline conditions. The oxidative power of Hydrogen peroxide is reduced in acid medium as mineral acids in particular are known to stabilise its decomposition. A few disclosures claim the use of peroxide under acid conditions for bleaching purposes for example US4372812 to Philips claims a process for bleaching paper pulp involving sequential treatments with oxygen at high pressure under alkaline conditions followed by exposure to a solution having 0.2-2% peroxide by mass of pulp at a pH of 3-5 and a temperature of 20-90°C. This is followed by an ozone treatment under acidic conditions with a neutralisation and washing step between the oxygen and peroxide stages. US6183597 to Siegle describes a bleaching process employing up to 3% hydrogen peroxide wherein the pulp is boiled in formic acid and once boiling the peroxide is added while the mixture is maintained at the boiling temperature.

The objective of peroxide bleaching in the paper industry is to oxidise the lignin under facile conditions so avoiding aggressive oxidation conditions that would excessively degrade the cellulose structure and content of the pulp. US2006/0124124 to Bhupendra discloses the use of peroxide under acid concentrations for the pre- treatment of lignocellulose biomass in conjunction with ferric and other salts. A lignocellulosic material is contacted with a mixture of dilute acid, a metal salt catalyst and at least one of hydrogen peroxide or hydrogen peroxide-producing chemicals, to produce a lignocellulosic material impregnated with hydroxyl radical. This mixture is then heated with an external heating source to a temperature of between 100°C and 250°C to partially hydrolyse the lignocellulose material. Impregnation of the biomass with peroxide and ferric salts in solutions at concentrations up to lOOmmol and 20mmol peroxide and metal salt respectively are claimed to effect a significant improvements in the yields of glucose achievable in a subsequent hydrolysis step.

Established chemical technologies to refine and hydrolyse lignocellulose biomass are still high energy-intensive processes requiring significant capital investment. To increase the commercial profitability of bio-refining lingocellulose particularly when compared to food substrates significant improvements still need to made, directed toward:

Reducing the mechanical energy inputs to the process particularly those associated with physical commutation, stirring and pumping operations.

Reducing the heat inputs to the process, usually supplied as steam in an industrial setting. Reducing the capital and operating costs by negating the exposure of reactors and ancillary equipment to severe conditions particularly the combination of moderate to high acid concentration and high temperature.

Reducing capital and operating costs by minimising the number and or the cost of unit operations particularly washing and neutralisation operations between the main chemical and physical operations involved particularly between pre-treatment and hydrolysis operations.

Improving the separation between the main biopolymer components particularly cellulose and lignin as the biomass proceeds through the reactor configuration to reduce recalcitrance. Improving the reaction kinetics particularly of cellulose hydrolysis by fractioning it form the rest of the biomass and providing it in a physical form that is of a sufficiently small particle size and homogeneity to effect efficient conversion at optimum hydrolysis conditions that do not favour its reaction to undesirable condensation products. Once the cellulose has been disassociated for the lignin component particularly its conversion to favourable products, namely glucose, HMF and LA is greater at substantially lower temperatures and acid concentrations than those required to reduce the recalcitrance.

Reducing the use of environmentally hazardous chemicals such as those containing halogens and toxic heavy metals such as chromium. The present invention is directed toward such improvements.

Non-Patent References

1. Girisuta, B., L.P.B.M. Janssen, and H.J. Heeres, Kinetic Study on the Acid-Catalyzed Hydrolysis of Cellulose to Levulinic Acid. Industrial & Engineering Chemistry Research, 2007. 46(6): p. 1696-1708.

2. Schell, D., et al., Dilute-sulfuric acid pretreatment of corn stover in pilot-scale reactor.

Applied Biochemistry and Biotechnology, 2003. 105(1): p. 69-85.

3. Eary, L., Catalytic decomposition of hydrogen peroxide by ferric ion in dilute sulfuric acid solutions. Metallurgical and Materials Transactions B, 1985. 16(2): p. 181-186

SUMMARY OF THE INVENTION

According to the invention, there is provided a method of transforming a lignocellulose material the method comprising the steps of:

a. combining a lignocellulose material with a solution containing hydrogen peroxide and a hydrogen peroxide stabiliser to produce a mixture that is at least 3% by mass hydrogen peroxide,

b. feeding said mixture to the entrance of a continuous reactor concomitant with providing an agent that facilitates the rapid decomposition of the hydrogen peroxide in the solution proximal to the entrance of the reactor so as to cause exothermic, explosive decomposition of the hydrogen peroxide to oxygen and water thus forming a mixture of gas, liquid, and solids and increasing the pressure and temperature in the reactor to at least 15 bar and 70°C respectively without addition of heat from an external source,

c. exiting the mixture of gas, water and solids formed in the reactor through an outlet with a pressure change, into a flash vessel wherein the mixture is separated into a liquid phase containing dissolved or suspended solids and a gas phase substantially rich in oxygen, and

d. continuously removing from the flash vessel a gas stream substantially rich in oxygen and a separate heated liquid stream having suspended or dissolved therein chemically and physically altered components of the lignocellulose including a substantially cellulosic material with reduced recalcitrance relative to the starting lignocellulose material. In one embodiment, the hydrogen peroxide concentration is at least 5% by mass. In one embodiment, the pressure in the reactor for. step b is at least 35 bar. In one embodiment, the pressure change outlet used in step c is a Venturi.

In one embodiment, the reactor is a plug flow or tubular reactor.

In one embodiment, the stabiliser includes an acid, a pyrophosphate compound or combinations thereof, and wherein the agent is an enzyme, transition metal salt, an alkaline compound dissolved or suspended in solution, or combinations thereof.

Preferably, the stabiliser includes an acid in combination with a transition metal salt, and wherein the agent includes an alkaline compound dissolved or suspended in solution. In one embodiment, the residence time in the reactor is up to 15 min.

In one embodiment, the compressed oxygen exiting the flash vessel is used to drive motors, for example on pumps, stirrers, conveyors, shakers, vibrators, chippers, grinders, centrifuges and combinations thereof. Preferably, the oxygen is used for combustion or gasification operations.

In one embodiment, the lignocellulose biomass is a plant material, a municipal waste, or combinations thereof.

In one embodiment, physically altered components of the lignocellulose exiting the flash vessel in the liquid stream have a smaller particle size than the starting lignocellulose material. In one embodiment, the physically altered components of the lignocellulose are amenable to acid hydrolysis.

In one embodiment, the liquid stream containing the physically altered components of the lignocellulose is fed to a second flash vessel or series of flash vessels and subjected to a pressure drop or series of pressure drops.

In one embodiment, volatile furanic compounds, acids and alcohols contained in the liquid stream are separated into the gas phase in the second flash vessel or series of flash vessels.

In one embodiment, the liquid stream exiting the second flash vessel or series of flash vessels is fed to a tank reactor, and wherein the cellulosic components, six carbon sugars and hydroxymethylfurfural contained therein is converted to Levulinic acid and formic acid. Preferably, the temperature in the tank reactor is up to 150°C. hrone embodiment, cellulose is recovered from the liquid stream exiting the second flash vessel or series of flash vessels through pH adjustment, separation, and washing operations, or combinations thereof. In one embodiment^ the separation operations include centrifugal separation, filtration, settling and combinations thereof.

In another aspect the invention provides a system for transforming a lignocellulose material, the system comprising:

a. means for combining a lignocellulose material with a solution containing hydrogen peroxide and a hydrogen peroxide stabiliser to produce a mixture that is at least 3% by mass hydrogen peroxide,

b. a continuous reactor and means for feeding said mixture to the entrance of the continuous reactor concomitant with providing an agent that facilitates the rapid decomposition of the hydrogen peroxide in the solution proximal to the entrance of the reactor so as to cause exothermic, explosive decomposition of the hydrogen peroxide to oxygen and water thus forming a mixture of gas, liquid, and solids and increasing the pressure and temperature in the reactor to at least 15 bar, and 70°C respectively without addition of heat from an external source,

a reactor outlet providing a pressure change and a flash vessel, and means for exiting the mixture of gas, water and solids formed in the reactor through said outlet, into said flash vessel wherein the mixture is separated into a liquid phase containing dissolved or suspended solids and a gas phase substantially rich in oxygen, and

means for continusously removing from the flash vessel a gas stream substantially rich in oxygen and a separate heated liquid stream having suspended or dissolved therein chemically and physically altered components of the lignocellulose including a substantially cellulosic material with reduced recalcitrance relative to the starting lignocellulose material.

DETAILED DESCRIPTION OF THE INVENTION

Brief Description of the Drawings

The invention will be more clearly understood from the following description of some embodiments thereof, given by way of example only with reference to the accompanying drawings in which: -

Fig. 1 is a diagram of a reactor of the invention;

Figs. 2(a) to 2(d) are plots indicating temperature profiles and liquor compositions of pre- treated biomass, as set out in Example 1;

Fig. 3 is a set of SEM images for Example 1;

Fig. 4 is a plot illustrating glucose release in Example 2; and

Fig. 5 is a plot illustrating glucose release during cellulose hydrolysis in Example 3. It is well known that hydrogen peroxide undergoes the following exemplary decomposition reactions:

1) H ₂ 0 ₂ :0 + H ₂ 0 0.5 O ₂ + H ₂ O 2) H,0 ₂ 2.0 ^' OH 0.5 O ₂ + H ₂ O and that analogous peroxide compounds undergo similar type reactions. These reactions are exothermic and spontaneous with an enthalpy of -98.2 kJ mol ^"1 . Under atmospheric conditions a large portion of this heat is absorbed in converting the water resulting from the decomposition reaction to steam. The rate of reaction is highly dependent on the concentration of peroxide, the temperature, pH and the presence of stabilisers or catalysts. Several transition and lower metal salts are known to catalyse the reactions including ferric and ferrous salts as are several enzymes such as those of the catalyse and peroxidase families. The activity of these catalysts are also ph dependent, for example Eary [3] determined that the rate of peroxide decomposition has the following rate law in the presence of aqueous solutions of ferric ions, [H ⁺ ] being representative of the acid concentration:

Where ko is 4.28xl0 ¹² sec ^"1 and the activation energy, E _a is 85.6 kJ/mol. It is well established that the nascent oxygen and radical species associated with 1) and 2) above respectively are strong oxidising agents and in small quantities under controlled conditions are effective at partially degrading the polymeric components found in lignocellulose and breaking them into their constituent monomers, rendering it less recalcitrant. However prolonged exposure either to high concentrations of peroxide at elevated temperature or for significant periods of time are known to extensively decompose the biopolymer components excessively either to lower alcohols and acids or completely to C0 ₂ and water. Previous disclosures employing peroxide for the purposes of treating lignocellulose have utilised relatively low concentrations usually under alkaline conditions to prevent excessive degradation of the biomass and avoid the operational hazard that the explosive decomposition of a mixture containing a high concentration of peroxide presents.

Particularly if the process is to be continuous, the introduction of the biomass to the reactor configuration necessitates an open vessel that is safe and operating at atmospheric pressure, mixing significant quantities of peroxide with biomass in alkaline conditions in such an open vessel would present a hazard. On the other hand exposing lignocellulose to peroxide in strongly acidic conditions reduces significantly the rate of reactions 1) and 2) above as mineral acids stabilise concentrated peroxide solutions, up to 60% w/w at room to moderate temperatures. Given the exothermic nature of the peroxide decomposition reactions above, at concentrations of 10% or greater it may potentially be used as a source of heat to supply sufficient thermal energy to raise the temperature of a reaction mixture through a significant temperature rise. In the context of utilising this heat to raise the temperature of a lignocellulose mixture a number of practical issues must be addressed. Firstly, to create sufficient heat to effect hydrolysis a significantly higher concentration of peroxide than has been used in previous disclosures would be required. At high concentrations and with the evolution of large amounts of nascent oxygen and radical species that would result the biomass would be exposed to excessive oxidation. This may be circumvented by keeping the exposure time of the biomass to a highly oxygenating environment to a minimum such as in a plug-flow or tubular reactor with a short residence time but this would require a mechanism to trigger the rapid decomposition of the peroxide in a short time period with a facility to remove the partially oxidised biomass from the oxygenating environment quickly thereafter before excessive oxidation could occur.

The present invention provides such a system. Lignocellulosic biomass is mixed with hydrogen peroxide and optionally a hydrogen peroxide stabiliser at room temperature. The stabiliser can be a stabiliser in conjunction with a hydrogen peroxide decomposition catalyst present in concentrations or at a pH that favours the overall stabilisation of the mixture at room to moderate temperatures such as for example the presence of a mineral acid (stabiliser) in sufficient concentration to maintain the pH below 3 in combination with ferric ions (decomposition catalyst). Preferred stabilisers include sulphuric acid, nitric acid, phosphoric acid, formic acid and combinations thereof and preferred decomposition catalysts include ferric or ferrous salts and oxides, aluminium salts and oxides, salts and oxides of the alkali metals, alkaline earth and transition metals, supported metal catalysts such as those on siliceous, zirconium or alumna supports, enzymes and combinations thereof. In exemplary applications of the present invention a mixture of up to 60% hydrogen peroxide (Aq) and up to 50% w/w dry lignocellulose biomass with a minimum sulphuric acid concentration of 0.0001 % w/w is relatively stable for sustained periods at room temperature in the presence of ferric sulphate up to concentrations of ferric ion that correspond to a molar ratio of up to 0.5; [Fe ³⁺ ]/[H ⁺ ], preventing excessive rapid decomposition of the peroxide. However such a mixture is not entirely facile and will have both the hydrolysing activity of the acid and a moderate oxidising activity associated with the peroxide facilitating the partial solubilisation of particularly, the hemi-cellulose and lignin components in the biomass. With a sufficient period of exposure this moderate activity may facilitate the swelling and softening of the recalcitrant biomass particles to the extent that it can be formed into a suspension that can be pumped more easily than a suspension of the raw biomass in water alone without effecting any significant change in temperature or the significant loss of peroxide or biomass. This process may be carried out at atmospheric pressure. The liquid phase and the sugars and lignols therein dissolved may be separated and recovered separately and fresh solution added on a continuous basis. Exposure times of up to 50 hours may be applied and, depending on the desired throughput a continuously stirred tank reactor ("CSTR") or semi batch reactor, may be sized accordingly to yield the appropriate residence time. The resulting suspension may then be pumped, preferably via a pump that can operate with a high pressure differential across it, to a continuous plug flow or tubular reactor wherein an agent is added to effect the complete, rapid exothermic decomposition of the peroxide. If the solution contains acid and ferric or ferrous ions the preferred agent is a base that effects a reduction in the [H ⁺ ] concentration proximal to the entrance to the continuous tubular reactor. The base may be a hydroxide or any suitable alkaline solution or suspension, added in sufficient quantity to change the pH of the reacting mixture to between 3 and 10. The exothermic decomposition of the peroxide and large volume change resulting from the consequential evolution of significant quantities of oxygen gas may:

- Effect the rapid progression of the mixture through the tubular reactor

- Heat the reaction mixture

- Facilitate the further physical break up of the lignocellulose material as entrained peroxide is explosively decomposed

- Substantially increase the pressure in the reactor

- Facilitate partial hydrolysis and oxidation of the holo-cellulose and lignin content respectively In exemplary applications the residence time in the PFR is up to 15 minutes and the temperature of the reaction mixture may be increased by up to 300°C in the reactor while the pressure may be increased by up to 300 bar. The reaction mixture may then be exited into a first flash vessel preferentially through a Venturi that may be a valve or other suitable cross section having an accompanying pressure drop. Preferably this flash vessel may operate at up to 290 bar, but in any event at a pressure lower than that in the PFR. The explosive effect of the pressure drop may facilitate the further break up of the lignocellulose feed stock. The flash vessel may have an operating temperature of up to 300°C and will have at least two exit streams a first liquid stream containing dissolved or suspended components of the lignocellulose biomass and a second gas stream containing substantially pure oxygen. Those skilled in the art will appreciate how the flash vessel and the exit piping carrying the gas and liquid exiting there from may be sized and controlled through the use of valves that may optionally be actuated. In preferred exemplary operations the liquid stream has little or no entrained oxygen and the total pressure in the flash vessel is maintained at a value sufficient to ensure that the vapour pressure of steam and furanic compounds in the gas phase is low.

The oxygen gas taken from the first flash vessel, being a compressed gas may be utilised to provide the mechanical energy to drive pumps and stirrers such as through the use of air driven motors and optionally in addition captured for use as an oxygen source in combustion and or gasification operations associated with the overall bio-refinery operation. In exemplary operations the thermal energy associated with this gas stream will be recovered for reuse through the use of heat exchangers.

The liquid phase exiting the first flash vessel may contain soluble components of the biomass including oligosaccharides of 5 and 6 carbon sugars, sugars, furanic compounds, acids including levulinic acid and formic acid in conjunction with lignols and the un-hydrolysed remaining solid components of the biomass. These solids may be present in the form of physically commuted fibres having a smaller particle size and more homogenous size distribution with a higher cellulose fraction than the starting raw lignocellulose material. The liquid stream may additionally contain inorganic salts derived from the partial neutralisation reactions that occurred in the PFR. In exemplary configurations of the present invention the liquid exit stream from the first flash vessel may be fed to a second flash vessel wherein a further pressure drop is applied to the reaction mixture separating it into two further streams, one gas, one substantially liquid, that exit the second flash vessel. Those skilled in the art will appreciate how such a vessel may be sized so as to operate at a pressure that facilitates the separation of furanic and analogous compounds contained in the incoming liquid stream into the gas phase. This gas phase containing substantially the hydrolysis products of 5 carbon sugars (furanic compounds) in conjunction with steam and lower molecular weight alcohols and acids may be exited from the second flash vessel for product recovery and heat transfer operations. Those skilled in the art will appreciate that a series of second flash vessels may be required to effect the removal of substantially all the 5 carbon sugar hydrolysis products form the reaction mixture depending on the nature of the starting biomass and the operating conditions of the reactor configuration.

The liquid phase exiting the second flash vessel or series of second flash vessels may contain substantially soluble, saccharides, sugars, lignols, acids, alcohols and heavier furanic compounds such as HMF in combination with un-hydrolysed biomass solids comprised largely of insoluble lignin and cellulose. Where the desired products of the biorefining operation are glucose, LA and FA this liquid stream may be fed to a continuous stirred tank reactor CSTR wherein the temperature is maintained in the range of between 70 and 190°C with a residence time of up to 8 hrs, such conditions favouring the conversion of the cellulose to glucose and LA as opposed to the condensation products known to form at higher temperatures. Such streams may be added as required to adjust pH and the solids to liquid ratio as required. The resulting mixture may be subjected to settling or filtration operations such as through the use of settling tanks, centrifugal separators or mechanical filters to separate a largely aqueous solution containing glucose, LA and formic acid from a largely solid fraction containing lignin and potentially inorganic solids.

Where the desired product of the bio-refining operation is cellulose for further industrial use such as in a fermentor for example, the liquid stream exiting the second flash vessel or series of second flash vessels may be cooled and subjected to ph adjustments, washing, drying and mechanical operations to separate cellulose from the lignin. Exemplary combinations of stabilisers and agents that may be used in the present invention are presented in Table 1 and include the stabilisers often present in commercial hydrogen peroxide solutions such as pyrophosphates. Additionally where stabilised peroxide is used enzymes such as catalyse could be used to decompose the mixture on entry to the PFR provided that the pH is simultaneously adjusted to between 3.5 and 9.5. In the case of catalyse the enzyme may be provided from a natural source such as an animal or plant waste stream.

Advantages and features of the present invention may be summarised as follows:

The use of the peroxide composition to swell the initial biomass may reduce the mechanical energy inputs to the process associated with pre-process physical commutation operations. The peroxide decomposition provides the heat for the process without the requirement for additional heat from an external source

The explosive effect of the entrained peroxide in the PFR and the pressure drops thereafter may break the lignocellulose into a physical form more amenable to hydrolysis

The oxidative action of the peroxide reduces the recalcitrance of the biomass through partial hydrolysis and oxidation of the halo-cellulose and lignin components respectively.

The severity of high acid concentration in combination with high temperature may be avoided due to the partial neutralisation occurring in the PFR increasing the life of the reactor and reducing capital costs as well as the requirement for neutralisation in subsequent steps.

The rapid throughput in the reactor and flash vessels may require that only a small part of the overall process configuration needs to be capable of withstanding high pressure/temperature conditions, thus reducing capital costs The potential energy of the compressed gas may be used to drive flow through the process reducing operational costs

Yields may be increased through the hydrolysis of a more homogenous material with reduced particle size and recalcitrance

The advantages of a chemical process are maintained (high throughput) using a chemical that does not give rise to environmentally hazardous by products.

Example 1.

A batch reactor with a large head volume was used to illustrate the efficacy of the invention on a lab scale using the combination of peroxide with Formic Acid and a mixture of Ferric sulphate and sodium hydroxide as the decomposing agent. Miscanthus (300 g) was mixed with liquor (2700 g) and sealed in an 8L Parr reactor, with a maximum operating pressure of 130 bar, and modified with additional ports. The liquor was made up such that the total mass (liquor and biomass) was 2.5, 5 and 7.5 w/w % with respect to peroxide, using the requisite amount of 30% aqueous peroxide in each case (stabilised with ppm levels of Sodium Pyrophosphate), and adjusting the formic acid weight fraction accordingly. The reactor was equipped with a stirrer which operated at 1500 rpm. NaOH solution (125 ml, 4 M, containing 100 mg/L Fe ₂ (S0 ₄ )3) in a charging vessel fixed to the reactor was injected to the liquor at time zero by means of nitrogen back pressure. The temperature and pressure of the contents were monitored and logged to a PC. The reactor was fitted with a liquid sampling port through which aliquots (20 mL) were removed at regular intervals to determine the temporal composition of the liquor. The solids content at the end of each run was filtered and washed with Formic Acid and water and subjected to further analysis. The results of the example can be summarised as follows:

- The enthalpy derived from the catalytic decomposition of the peroxide is sufficient to heat the reaction system above 70°C while at low concentrations of peroxide (2.5%) it is not. The hydrogen peroxide concentration is at least 3% by mass, and preferably at least 5%.

- Rapid and effective delignification is achieved while at low concentrations some delignification is achieved it is slow and inefficient because of the prolonged exposure of dissolved lignin to peroxy radicals

- Rapid hemicellulose depolymerisation and subsequent hydrolysis to C5 sugars is achieved while at low peroxide concentrations little hemi-cellulose removal is achieved even at extended periods - The resulting pulp is largely cellulosic with a physically altered morphology and reduced particle size comprising fibres 10 micron in diameter as compared with the 2cm chips comprising the starting material The temperature profiles of the FA and 2.5, 5.0 and 7.5% peroxide mixtures are shown in Figs. 2(a), (b) and (c), respectively. Table 2 shows pulp compositions for these concentrations. Insufficient peroxide was available for the decomposition reaction to become autocatalytic at the 2.5% loading. Consequently the maximum temperature reached was only 44°C after 4 hours of reaction. However, at higher peroxide concentrations the decomposition reaction became autocatalytic and significant heat was released rapidly, the more so the higher the initial peroxide concentration In the case of the 5.0% and 7.5% peroxide concentration, the temperature curve is characterised by a rapid increase in temperature followed by a plateau at or about the boiling point of the FA/water azeotrope (107°C). The reactor system was not insulated, but the duration of the plateau at 7.5% Η ₂ 0 ₂ as compared with 5.0 % is consistent, with more heat being released for the 7.5% concentration. Furthermore, the pressure profiles for both concentrations are consistent with the calculated pressures arising from the expected amount of oxygen released from the decomposition of hydrogen peroxide. The large amount of head room in the reactor facilitated rapid segregation of the evolved oxygen from the liquor. A temperature fluctuation is observed following the rapid heat-up phase of the 5.0% and 7.5% peroxide treatments (this behaviour is not observed at 2.5% loading). This fluctuation is coincident in both cases with the observation of both lignin and hemi-cellulose sugars in the liquor. In view of the morphology of the pulps recovered from both pretreatments this point is reflective of an almost instantaneous collapse in the secondary structure of the Miscanthus at this point. This time is ascribed TB for the purposes of comparing behaviour at both 5.0% and 7.5% peroxide concentrations and in addition to being indicative of the commencement of both lignin and sugar release, at TB the peroxy decomposition reactions have reached completion as no further increase in pressure or temperature was observed beyond this point. Fig. 2 also shows the temporal evolution of the lignin and sugar concentrations in the liquor. Approximately 20% of the initial lignin present in the biomass was solubilised in 25 hrs in the 2.5% peroxide medium, because the system did not become peroxide, and by extension oxidising peroxy radical species, were present for extended periods in the liquor, and consequently solubilised lignin is oxidised further to lignols and lower molecular weight fragments. This is confirmed by the observation of a low concentration of lignin in the 2.5% pulp removed after 48 hours despite the fact that only moderate amounts could be detected in the liquor. The dark liquor aliquots removed during the 2.5% experiment became lighter in colour with prolonged storage at ambient conditions and only relatively small amounts of lignin could be precipitated from the liquor at the end of the experiment.

Based on the compositional analysis of the pulp removed, only 13% of the starting hemicellulose was solubilised after 48 hrs in the case of the 2.5% H ₂ 0 ₂ treatment. The low concentration of sugars in the liquor would indicate that the hemicellulose was not readily hydrolysed to monomelic sugars.

The behaviour of the system is markedly different when sufficient peroxide is present to force autocatalytic conditions (5% and 7.5%). Initial peroxide concentration has a significant influence on the extent and the rate of both lignin and hemicellulose removal. The same overall temporal pattern is observed for the 5% and 7.5% peroxide concentrations. Dissolution of lignin and of carbohydrate into the liquor commences at TB and the liquor concentrations of both increase rapidly before levelling off at relatively constant values. The time to reach maximum C5 sugar concentration and maximum lignin concentration in the liquor, ascribed Tmax, is coincident in both cases. Approximately 65% of the lignin initially contained in the Miscanthus is dissolved into the liquor in 30 and 140 min in the 7.5% and 5% peroxide liquors, respectively. This increase in the rate of dissolution with increasing peroxide concentration is due to an increase in both the initial oxidising potential and the temperature of the liquor at the higher initial peroxide concentrations. Importantly, and in contrast to the 2.5% peroxide liquor the aliquots removed following r _B in both the 5.0% and 7.5% peroxide liquors did not oxidise further on storage in ambient conditions indicating that oxidising radicals were absent in the liquor following the initial aggressive decomposition of the peroxy species which is essentially complete by r _B , and their lignin contents were readily recovered from the liquor by precipitation.

The determination of τ _Β and T^X for the 7.5% liquor is shown in Fig. 2d. While the present example relates to a batch reactor with the consequence that the decomposition commenced from a standing cold start, it should be noted that once the temperature reaches 40°C the decomposition reaction rate becomes essentially exponential. In a continuous high pressure reactor (plug flow reactor) operating at steady state the required residence time in a high pressure environment could be reduced to as little as 5 min (Figure 2d).

Hemicellulose removal from the pulp increases from 13 to 68 to 89 % respectively for the 2.5, 5.0, and 7.5 % initial peroxide concentrations. This is attributed to the increased oxidising potential of the liquor and to the greater amount of heat released by the higher initial concentrations of peroxide. In this way the reaction mixture is maintained at the elevated temperature for longer periods. In general the mass distribution of the hemicellulose sugars at the end of each experiment across the liquor and pulp indicates that the amount of hemicellulose recoverable from the liquor as sugars increases significantly with increasing initial peroxide concentration.

Cellulose recovery is excellent at high peroxide conditions (Table 3) and importantly the form of the remaining cellulose derived under autocatalytic conditions (5.0% and 7.5%) is uniform relative to the starting material and the 2.5% pulp. Fig. 3 shows SEM and laser con-focal microscopy images of the raw material and pulps recovered after treatment with the different initial peroxide concentrations. At the higher concentrations sufficient oxidising potential and heat is released to de- lignify the biomass and break down the secondary structure of the plant. This is evidenced by the morphologies of the cellulose recovered from the 5.0 arid 7.5 % treatments. In these, the remaining cellulose is in the form of fibres some hundreds of microns in length and, crucially, all with an approximate diameter of 10 microns.

Table 2: Pulp composition

Peroxide concentration w/w %

Component Raw material 2.50 5.00 7.50

Glucose 40.31 52.4 72.12 79.16

Galactose 0.64 0.53 0.14 0.04

Mannose 0.25 0.17 0.13 0.07

Rahmnose 0.21 0.13 0.08 0.06

Total C6 41.41 53.23 72.47 79.33

Xylose 19.38 22.72 11.95 4.92

Arabinose 2.15 2.11 0.43 0.12 Total C5 21.53 24.83 12.38 5.04

K-Lignin 21.79 5.95 4.47 6.02

Extractives 1.81 2.00 3.29 5.58

Table 3: Pulp Characteristics

Peroxide concentration

2.5 5.0 7.5

*

Time (min) 2880 250.00 150.00

Pulp yield 76.70 55.70 48.70

Cellulose recovery 99.70 99.65 95.63

Hemicellulose removal 13.03 68.66 88.79

Lignin removal 79.06 88.57 86.54

Dissolution behaviour

7 B (min) 31.2 17.1

7 _M ax (min) 140.0 30.0

Time at which pulp was removed from the liquor

* ^* Gravimetric determination

Example 2: Enhanced enzymatic digestibility of the pre-treated material in subsequent enzymatic hydrolysis

To demonstrate the benefit of the pre-treatment on the digestibility of the resulting cellulose the pre- treated materials were subjected to enzymatic hydrolysis using the starting raw material and Avicel (commercial micron size crystalline cellulose) as a control. In each case the same cellulase cocktail was used. Fig. 4 shows the rate of glucose release from the pre-treated materials demonstrating a 20- fold increase in the digestibility of the pre-treated material as compared with the starting raw material.

Example 3: Enhanced Glucose release from the pretreated materials in subsequent acid hydrolysis To demonstrate the benefit of the pre-treatment in negating mass transfer effects in subsequent mineral acid hydrolysis of cellulose the pre-treated material and the raw Miscanthus were hydrolysed at 150 C in 1% Aq H ₂ S0 ₄ at the same initial mass loading (10%w/w). The rates of glucose release (cellulose hydrolysis) are shown in both cases in Fig. 5. Maximum glucose concentration (lOOmmol) in the pre-treated material is achieved in approximately 125 min under the mild hydrolysis conditions used as compared with the untreated material wherein maximum glucose concentration has still not been achieved after 400 min.

It will be appreciated that whilst certain exemplary configurations of the present invention have been provided that the invention may be varied in construction and design depending on the particular lignocellulose materials being processed. Accordingly, the invention is not limited to the embodiments described but may be varied in construction and detail but directed to a process that utilises Hydrogen peroxide as a means to chemically and physically alter lignocellulose materials while simultaneously supplying the thermal energy (derived from the enthalpy of its decomposition) necessary to effect its hydrolysis. Where the term "lignocellulose" is used this could be replaced with the term biomass, cellulosic material, natural materials containing biopolymers of largely C5 and or C6 sugars. Where a Venturi is described any other inlet which allows flow through an orifice with an accompanying pressure drop could be used. The peroxide concentration could be different from that described, such as at least 2%, and the pressure in the PFR could be at least 15 bar.

The invention is not limited to the embodiments described but may be varied in construction and detail.