Method for optimising the production of levoglucosenone during steam cracking of lignocellulosic biomass

Abstract

The present invention relates to the field involved in the valorisation of by-products obtained during the production of black pellet-type fuel having a high calorific value from lignocellulosic biomass. More precisely, the invention relates to a method for optimising and valorising the production of levoglucosenone during a steam cracking process.

Description

PROCESS FOR OPTIMIZING LEVOGLUCOSENONE PRODUCTION DURING STEAM CRACKING OF LIGNOCELLULOSIC BIOMASS

[0001] The present invention relates to the field of the recovery of co-products obtained during the production of high calorific value “black pellet” type fuels from lignocellulosic biomass. More specifically, the invention relates to a method for optimizing steam cracking parameters allowing a higher ratio of levoglusenone to be obtained during a steam cracking process. Field of invention

[0002] The transformation of lignocellulosic biomass (wood, agricultural residues, agricultural and agro-industrial co-products) into an energy-dense, transportable and easily storable compound would make it possible to develop and consolidate an industrial stationary energy sector (biofuel used at a fixed point, the home, unlike biofuels) and to reduce environmental impacts (fossil CO2 emissions, with biomass without fertilizers or phytosanitary products).

[0003] Black pellets are moisture-resistant cylinders 1 to 3 cm long with good mechanical strength, allowing storage and handling similar to coal. Their combustion generates little ash, with a lower heating value (LHV) close to 18 to 20 joules / gram of dry matter.

[0004] Black pellets are produced from lignocellulosic biomass that has undergone steam cracking. This involves a heat treatment followed by sudden depressurization to provide a waterproof material for shaping into pellets or briquettes. The raw material is actually steam-exploded, releasing finer particles, allowing the material to have strong cohesion during the aggregation or molding phase.

[0005] Hydrothermal treatment, also known as aqueous fractionation, solvolysis, or hydrothermolysis, differs from steam cracking in that it uses high-temperature, high-pressure water to promote the disintegration and separation of the lignocellulosic matrix. This technique is not suitable for the production of black pellets since the resulting products are predominantly liquid.

[0006] Pyrolysis is the chemical decomposition of an organic compound by intense heating in the absence of oxygen. The compounds obtained after pyrolysis differ in their characteristics from those obtained by steam cracking. Steam cracking cannot be considered a pyrolysis technique in that it uses a steam explosion and is carried out in the presence of oxygen.

[0007] It is also necessary to differentiate between roasting processes which are characterized by a thermochemical treatment between 100 and 300°C allowing part of the organic matter to be modified to break the fibers while eliminating the water.

[0008] The existing steam cracking process makes it possible to produce a dry, pre-treated lignocellulosic biomass powder, without chemical additives, stable and economically viable for commodities such as energy, and even more so for higher value-added products.

[0009] It is also known to those skilled in the art that treatment processes, such as steam cracking, allow the production of intermediate products with added value. For example, it is known to those skilled in the art that molecules of interest can be formed under the thermal effect of steam cracking and can be extracted by washing.

[0010] Patent application WO2021167511A1 describes a method and system for recovering energy and chemicals from a steam explosion reactor in a biorefinery. In particular, it discloses a process in which co-produced levoglucosenone is recovered.

[0011] Application US2021 / 317130 describes a process for producing levoglucosenone from a particulate cellulosic material comprising the following steps:

[0012] forming a premixture with a particulate cellulosic material, water, an acid and a polar organic solvent having a boiling point higher than that of levoglucosenone,

[0013] introduction of the premix into a pyrolysis reactor, maintained at a temperature between 250°C and 450°C,

[0014] remove gaseous products and carbon from the pyrolysis reactor, and

[0015] condensation of levoglucosenone and polar organic solvent of gaseous products, wherein the pyrolysis reactor comprises a reactor in which the premix is ​​fluidized by a fluidizing gas.

[0016] Other methods for producing levoglucosenone are known from the prior art.

[0017] For example, patent application WO2016 / 039996, which describes a process which consists of bringing a reaction mixture comprising a solvent and an acid catalyst into contact with a carbohydrate source.

[0018] Patent application WO2021 / 171014 describing an installation for carrying out the thermolysis of cellulose is also known from the prior art.

[0019] The known methods of the prior art propose processes for recovering co-produced molecules of interest. It would be interesting to obtain an alternative process for producing levoglucosenone.

[0020] The inventors propose a process for producing steam-cracked granules whose parameters are oriented to optimize the production of levoglucosenone.

[0021] The proposed process has specific parameters in terms of drasticity (residence time, temperature) and composition of raw materials (more xylose in hardwoods than in softwoods, more acidity in oak than in other hardwoods) allowing optimization of the production of levoglucosenone.

[0022] The levoglucosenone produced during the steam cracking step can then be recovered from the residual gases by condensation and / or from the powder by steam leaching or by extraction with a solvent.

[0023] Thus, the invention therefore consists of a process for producing granules by steam cracking of lignocellulosic biomass consisting mainly of a mixture of hardwoods and / or softwoods optimized to improve the production of an intermediate product such as levoglucosenone comprising the steps of:providing a lignocellulosic biomass consisting mainly of a mixture of hardwoods and / or softwoods having a moisture content of between 5 and 27%treating said biomass by steam cracking at a pressure of between 10 and 25 bars, and preferably between 16 and 19 bars, for 3 to 20 minutes a temperature of between 203 and 208°C and a severity factor of between 3.5 and 4.5, and preferably between 4.0 and 4.2 until a powder is obtainedRecovery of levoglucosenone in the residual gases and / or in the powder by steam leaching or solvent extraction.

[0024] Advantages of the invention

[0025] The process according to the invention proposes a completely innovative dual production: the optimized production of levoglucosenone at the same time as that of biofuel pellets. Thanks to this process, it is possible to reduce production costs by reusing molecules produced under the thermal effect of steam cracking and extractable by washing, distillation or other means.

[0026] On the one hand, the process advantageously allows for the optimization of levoglucosenone production. This molecule is particularly interesting in the field of specialty polymers, perfumes, and pharmaceutical active ingredients. Levoglucosenone is a green solvent precursor, such as the commercial product from CIRCA called Cyrene®.

[0027] To date, there is no process of industrial scale and reality for transforming lignocellulosic biomass into high added-value molecules, with large-scale technical reality and economic viability, and a good environmental balance, without risks. Molecules derived from biotechnology (enzymes, microorganisms) are almost the only chemical valorizations to date based on lignocellulosic materials.

[0028] Although the recovery of levoglucosenone during a steam cracking process is known from the prior art, there is no process for specifically optimizing its production and recovery while maintaining the production of good quality pellets.

[0029] On the other hand, the process advantageously proposes to produce, simultaneously with the optimized production of levoglucosenone, biofuel pellets, which makes the process economically viable.

[0030] Some pellet preparation processes require the use of synthetic chemicals. These chemicals are a source of both air pollution through their production or end-of-life, and toxicity. In this case, the absence of synthetic chemicals in the finished product, namely biofuel pellets, prevents the release of toxic products during use: no contamination of enclosed spaces.

[0031] Furthermore, the absence of water or its drastic reduction for steam cracking and pressing during the manufacture of biofuel pellets (densification stage) reduces energy costs (less heating) and gaseous or liquid effluents.

[0032] The use of steam-cracked biomass (wood in particular), which provides natural cohesion capacities for the preparation of black pellets, helps reduce environmental impacts (few or no chemicals, pressing processes without water and with less energy). BRIEF DESCRIPTION OF THE FIGURE

[0033] The curves of the evolution of the concentration of levoglucosenone in mg / kg of treated biomass are presented, depending on the severity of the process, for 3 wood species: eucalyptus, a mixture of hardwoods and bark beetle spruce.

[0034] A first subject of the invention relates to a steam cracking process from biomass consisting mainly of a mixture of hardwoods and / or lignocellulosic softwoods optimized for the production and recovery of levoglucosenone comprising the steps of:providing a lignocellulosic biomass consisting mainly of a mixture of hardwoods and / or softwoods having a moisture content of between 5 and 27%treating said biomass by steam cracking at a pressure of between 10 and 25 bars, and preferably between 16 and 19 bars, for 3 to 20 minutes a temperature of between 203 and 208°C and a severity factor of between 3.5 and 4.5, and preferably between 4.0 and 4.2 until a powder is obtainedrecovering the levoglucosenone in the residual gases by condensation, in the powder by leaching, by steam or by extraction with a solvent.

[0035] “Lignocellulosic biomass” means a plant material whose major constituents are cellulose, hemicellulose and lignin. The proportions of these components vary depending on the plant species. In the context of the invention, the lignocellulosic biomass of interest is mainly made up of glucose-rich hardwoods and softwoods.

[0036] The hardwood category includes two types of wood. This category includes, on the one hand, softwoods such as eucalyptus or poplar, and on the other hand, hardwoods such as hornbeam or oak. These two types of wood have different intrinsic characteristics. Indeed, softwoods are woods that have been saturated with moisture throughout their rapid growth, while hardwoods, which grow slowly, have lost the moist sap that nourished them over time.

[0037] By "hardwood mix" we mean a mixture of hardwoods and hardwoods such as hornbeam, oak, beech.

[0038] By "softwood" we mean woods rich in resinous materials, such as spruce, wood chips or softwood sawdust.

[0039] By “consisting mainly of a mixture of hardwoods and / or softwoods” is meant a lignocellulosic biomass consisting of more than 50% by weight of hardwoods and / or softwoods.

[0040] By "dry steam cracking" is meant steam cracking carried out with lignocellulosic biomass with a moisture content of between 5 and 27% and in which no water or chemical product is added during steam cracking. For the purposes of the invention, the term "chemical product" designates any substance formed by chemical treatment or by the assembly of several different chemical elements in defined proportions.

[0041] In one embodiment, the powder obtained in the steam cracking stage is capable of being densified in order to obtain dense granules (“black pellets”) intended to be used as biofuel.

[0042] Levoglucosenone is a molecule derived from glucose that is produced in particular during steam cracking under specific steam cracking conditions. This molecule is represented by the following formula:

[0043]

[0044] During steam cracking, sugars such as xylose from hemicelluloses and glucose from cellulose, contained in lignocellulosic biomass, can be released or chemically modified to produce intermediate molecules such as levoglucosenone. By combining raw materials rich in accessible glucose and specific steam cracking conditions (temperature, residence time, humidity to increase the production of these high-value molecules), it is possible to optimize the production and recovery of this molecule.

[0045] The steam cracking process according to the invention makes it possible: on the one hand to optimize the production and recovery of an intermediate product such as levoglucosenone produced under the thermal effect of steam cracking and extractable by condensation of the residual gases or in the powder by washing, distillation or leaching which, by its added value, constitutes a product of high interest. on the other hand to produce a lignocellulosic biomass powder capable of being densified in the form of granules which has in particular the properties of being: dry, pretreated, without chemical additives, stable and economically viable for commodities such as energy, therefore a fortiori viable for products with higher added value.

[0046] In a particular embodiment, the steam cracking process is carried out as follows:

[0047] - obtaining, from wood chips, wood fragments with dimensions between 0.5 and 14 mm and a humidity level between 5 and 27%;

[0048] - continuous introduction of a predetermined volume per minute of said wood fragments into a pressurized reactor, said reactor being supplied with substantially saturated water vapor whose pressure is between 16 and 19 bars and whose temperature is between 203 and 208°C;

[0049] - exposure of the wood fragments introduced into said reactor to said water vapor for a sufficient duration to obtain steam cracking of between 3 and 20 minutes and preferably between 7 and 15 minutes, the value of said exposure duration and the value of the temperature of said substantially saturated vapor being selected so that the severity factor is between 3.5 and 4.5, preferably between 4.05 and 4.15;

[0050] - continuous extraction from said reactor of the same predetermined volume of wood fragments per minute, through a plurality of orifices opening into a conduit substantially at atmospheric pressure, so as to cause explosive decompression of said wood fragments extracted from said reactor in said conduit;

[0051] - separation of said decompressed wood fragments and the residual steam extracted from said reactor, said wood fragments obtained after separation forming a combustible material in powder form.

[0052] - Recovery of levoglucosenone in residual gases by condensation

[0053] The Treatment Severity Factor is defined by the formula:

[0054] FS=Log10(time(min)*exp((T°C-100) / 14.75)).

[0055] The higher the temperature and the longer the treatment time, the greater the severity, the more transformation is observed in the product, the more carbonaceous matter is lost in the evaporates.

[0056] In a first particular embodiment of the invention, the raw material of the steam cracking process is a glucose-rich lignocellulosic biomass. In one embodiment of the invention, the raw material is mainly a mixture of hardwood and glucose-rich softwood. In a preferred embodiment, the raw material is a mixture of hardwood, eucalyptus and unbarked oak. This raw material is particularly interesting since it allows the recovery of levoglucosenone (a high added-value molecule), at a concentration of between 3 and 9 mg / kg of treated lignocellulosic biomass. In a particular embodiment, the steam cracking process makes it possible to obtain a quantity of levoglucosenone of between 1 and 10 mg / kg of treated lignocellulosic biomass and more particularly between 5 and 10 mg / kg of treated lignocellulosic biomass.

[0057] In an even more advantageous embodiment, the raw material is chosen from: a mixture of hardwoods, unbarked oak, softwood sawmill related chips or a mixture of these.

[0058] In a particular embodiment, the levoglucosenone is recovered from the powder by leaching or by extraction with a solvent. In an advantageous embodiment, said solvent is a polar solvent. In another embodiment, the solvent in the recovery step is ethanol.

[0059] In a particular embodiment, at least a portion of the powder obtained in the steam cracking step is used in the levoglucosenone recovery step.

[0060] In a preferred embodiment, the biomass consists of more than 50% by weight of a glucose-rich biomass. The resulting powder can be used for the recovery of levoglucosenone by leaching and / or by extraction with a solvent such as ethanol.

[0061] In another embodiment, the biomass consists of more than 50% by weight of a mixture of hardwoods and softwoods rich in glucose.

[0062] In another particular embodiment of the invention, the residence time of said biomass in the steam cracking enclosure is between 5 and 10 minutes. In an even more advantageous embodiment, the residence time is 7.5 minutes.

[0063] In another particular embodiment of the invention, the temperature at the steam cracking stage is between 206°C and 208°C, in an even more advantageous embodiment, the temperature at the steam cracking stage is 208°C.

[0064] In another particular embodiment of the invention, the severity factor at the steam cracking stage is between 4.05 and 4.30 and preferably between 4.05 and 4.15.

[0065] A second object of the invention is the use of the steam-cracked powder or the leaching residue obtained by the process of the invention for the production of steam-cracked granules in order to be used as biofuel.

[0066] A third object of the invention is the use of levoglucosenone obtained by the process of the invention, as a precursor for the production of green solvent or antiviral molecules.

[0067] Indeed, levoglucosenone is used as a precursor for the production of cyrene, a green solvent used in the chemical industry. In addition, levoglucosenone is a precursor to highly sought-after antiviral molecules in the pharmaceutical industry. EXAMPLES

[0068] EXAMPLE 1: Study of the quantity of levoglucosenone in condensates of different biomasses after steam cracking.

[0069] 1 - Materials and methods

[0070] A) Condensate samples

[0071] 21 condensate samples were studied. The codification, species, operating conditions and production batch are given for each sample in Table 1.

[0072] Sample nameSpeciesSeverity conditionsProduction batch10 / 01 / 20 Balance C6Oak3.91 = 203 °C; 7.5 min110 / 01 / 20 Balance C8Oak3.96 = 208 °C; 6 min114 / 01 / 20 Balance CNE6Unbarked oak3.91 = 203 °C; 7.5 min116 / 01 / 20 Balance ES6Spicy bark beetle3.91 = 203 °C; 7.5 min116 / 01 / 20 Balance BE6Wood B energy3.91 = 203 °C; 7.5 min117 / 01 / 20 Balance CHA6Hornbeam3.91 = 203 °C; 7.5 min115 / 02 / 20 Balance BBP6Wood B panels3.91 = 203 °C; 7.5 min114 / 04 / 20 Balance EUC6Eucalyptus3.91 = 203 °C; 7.5 min114 / 04 / 20 Balance EUC9Eucalyptus4.05 = 208°C; 7.5min114 / 04 / 20 Balance EUC3Eucalyptus3.67 = 195°C; 7.5min115 / 04 / 20 Balance EUC8Eucalyptus3.96 = 208°C; 6min115 / 04 / 20 BAP6Bois Pallet assessment3.91 = 203 °C; 7.5 min117 / 04 / 20 Balance SHS6 pH 3.11Schilliger softwood sawdust3.91 = 203 °C; 7.5 min117 / 04 / 20 Balance SHP6 pH 3.15Schilliger softwood chips3.91 = 203 °C; 7.5 min113 / 05 / 20 Balance PF6Forest chips3.91 = 203 °C; 7.5 min101 / 07 / 20 Balance M2F5Hardwood mix3.81 = 203 °C;6min101 / 07 / 20 Assessment M2F6Mixture of hardwoods3.91 = 203 °C; 7.5 min101 / 07 / 20 Balance M2F8Hardwood mixture3.96 = 208°C; 6min102 / 07 / 20 Assessment ES5Burdy spruce3.81 = 203°C; 6min202 / 07 / 20 Assessment ES6Spicy bark beetle3.91 = 203 °C; 7.5 min202 / 07 / 20 Assessment ES8Burdy spruce3.96 = 208°C; 6min2;

[0073] Table 1: List of condensate samples studied

[0074] B) Methods used

[0075] B.1 Analysis of sugars and carboxylic acids

[0076] Analysis is performed on an Ultimate 3000 HPLC (Thermo), using an Aminex HPX-87H column (7.8 x 300 mm, 9 μm) heated to 50 °C. Samples are filtered through an RC filter. 3 of 0.2 μm, 20 μL are injected per analysis. The mobile phase consists of 4 mM sulfuric acid, pumped with a flow rate of 0.5 mL / min for 90 minutes. Detection is done in UV at 210 and 280 nm, as well as with an RI detector 4 set in positive mode.

[0077] The analysis time has been increased to 90 min compared to 60 min initially in phase I. This optimization follows the observation of a disturbance of the baseline on the chromatograms of certain samples. This is due to the matrix of the previously injected sample which is very retained on the column used. In order to no longer encounter this type of problem which could affect the quality of the chromatographic peaks, the analysis time has therefore been increased.

[0078] The analysis of sugars and carboxylic acids was carried out in 4 replicates.

[0079] B.2. Analysis of phenolic compounds

[0080] Analysis is performed on an Ultimate 3000 HPLC (Thermo), using an Accucore C18 AQ column (3 x 100 mm, 2.6 μm) heated to 48 °C. Samples are filtered through a 0.2 μm RC filter, 1 μL is injected per analysis. The mobile phase consists of a gradient of 0.1% formic acid and acetonitrile.

[0081] The proportion of acetonitrile varies from 2 to 30% in 10 minutes with a flow rate of 0.8 mL / min. Detection is done by UV at 320, 210, 280 and 254 nm.

[0082] The quantification of levoglucosenone was disturbed at 210 nm by the presence of a co-eluting compound. Following a study carried out on the absorbance of LGO, its maximum absorbance wavelength was determined to be 320 nm. This new wavelength was specifically monitored to improve the detection limit of LGO and to overcome the co-elution which is no longer visible at 320 nm. The analysis of phenolic compounds was carried out in 3 replicates.

[0083] B.3. Use of the metered addition method

[0084] The standard addition method is a quantitative analysis method that replaces the calibration method when a sample matrix effect is observed. The retention time and / or signal intensity can be modified. This method consists of creating a calibration range, but from the sample and not in a solvent. The principle is to add a standard of known and increasing concentration of the molecule to be measured to the sample. Here, this method was used to confirm the presence of certain compounds by doping the samples with the standard. For quantification, external ranges were used.

[0085] B. 4. Mass spectrometry analysis

[0086] Mass analysis is performed on a Q-ToF5 LC (Agilent Infinity 1290 / 6545), using a Zorbax C18 column (2.1 x 50 mm, 1.8 μm) heated to 40 °C. Samples are filtered through a 0.2 μm RC filter, 1 μL is injected per analysis. The mobile phase consists of a gradient of 0.1% formic acid and acetonitrile. The proportion of acetonitrile varies from 5 to 100% in 18 minutes with a flow rate of 0.45 mL / min. A first detection is done in UV at 220, 250 and 320 nm. A second mass detection is performed in positive mode, with a scan ranging from 50 to 1000 m / z. The reference masses used to calibrate the analysis are 121.0509 and 922.0098 Da.

[0087] B.5. Calculation of relative concentrations

[0088] The relative concentrations shown were calculated according to Equation 1.

[0089]

[0090] For each sample, and for each compound, the ratio of the concentration (of the compound) to the sum of the concentrations was calculated and converted into a percentage.

[0091] B.6. Statistics

[0092] The values ​​presented correspond to averages calculated on the different replicates with their associated standard deviations. Since the orders of magnitude of the averages are very different, in certain cases, the coefficient of variation was calculated. This is a measure of relative dispersion, calculated by taking the ratio of the standard deviation to the average. It allows us to judge the dispersion of values ​​around the average, whatever its order of magnitude. It is often expressed as a percentage.

[0093] C) Results

[0094] C.1. Average composition obtained with a severity of 203°C and 7.5 min of residence time on different species (in mg / kg of treated biomass)

[0095] The variability study was carried out on 13 types of wood extracted under the severity conditions of 3.91, i.e. at 203°C for 7.5 min. The average concentrations obtained are presented in Table 2.

[0096] SpeciesLevoglucosenone(mg / kg)Mixed hardwoods8.75Eucalyptus3.09Unbarked oak5.05Forest chips3.73Spruce bark 12.85Spruce bark 23.31Hornbeam2.63Oak1.94Softwood sawmill chips4.58Pallet wood2.11Panel wood0.94Softwood sawmill sawdust4.24Energy wood0.72

[0097] Table 2: Average concentrations obtained with a severity of 3.91 on different species

[0098] It is observed that the 3 woods which produce the highest concentrations of levoglusenone are: mixture of hardwoods, unbarked oak and sawmill softwood chips; the three lowest are: energy wood, panel wood and oak.

[0099] C.2. Analysis of the influence of process severity conditions

[0100] The influence of process severity conditions was studied on 3 different woods: eucalyptus, mixed hardwoods and bark beetle spruce. Table 3 shows the average concentration of the 3 woods used for the study of the impact of severity conditions.

[0101] CompoundSeverityLevoglucosenoneEucalyptus3.67 (7.5 min; 195°C)1.63.91 (7.5 min; 203°C)3.13.96 (6 min; 208°C)6.84.05 (7.5 min; 208°C)3.9Hardwood mixture3.81 (6 min; 208°C) 203°C)6.33.91 (7.5 min; 203°C)8.73.96 (6 min; 208°C)10.1Spruce Scolytea3.81 (6min; 203°C)2.63.91 (7.5 min; 203°C)3.33.96 (6min; 208°C)4.9

[0102] Table 3: Average concentrations of levoglucosenone (in mg / kg of treated biomass) analyzed by LC-UV on 3 wood species

[0103] It seems that the concentration of levoglucosenone in Eucalyptus increases up to the condition of severity 3.96, and that the condition of severity 4.05 is too severe and begins to degrade this compound.

[0104] Conversely, we observe that the rate of Levoglucosenone increases proportionally to the intensity of the severity factor for the mixture of hardwoods and the Spruce Bark Beetle.

[0105] Thus, according to this study, severity conditions of 3.91 or 3.96 are optimal for increasing levoglucosenone concentration when using eucalyptus. On the other hand, higher severity conditions of 3.91 or 3.96 seem appropriate for mixed hardwood and Spruce Bark beetle type woods.

[0106] Conclusion :

[0107] The results of the study show that there is variability between the different wood species studied. The three wood species have generally higher concentrations than the other woods. These are hardwood mixtures, eucalyptus and unbarked oak. They have a levoglucosenone concentration between 3 and 9 mg / kg of treated biomass. These woods are therefore of interest for the recovery of condensates in the recovery of levoglucosenone.

[0108] EXAMPLE 2: Evolution of levoglusenone concentration as a function of process severity factor A - Materials and methods

[0109] The same protocol as in Example 1 was applied.

[0110] B - Results

[0111] Table 4 shows the evolution of the concentration of levoglucosenone released by 3 wood species as a function of the severity of the process, in conditions of severity greater than those presented in Table 3.

[0112] Wood SpeciesDuration (mins)Temperature (degrees C°)Log Severity FactorLevoglucosenone Concentration (mg / Kg)Eucalyptus7.51953.671.67.52033.913.162083.966.87.52084.053.9Broadleaf Mixture62033.816.37.52033.918.762083.9610.1202014.2712.1Spruce Bark Beetle62033.812.67.52033.913.362083.964.9202014.2715.3

[0113] Table 4: Evolution of the average concentration of levoglucosenone (in mg / kg of treated biomass) as a function of the severity factor with 3 wood species.

[0114] The, represents curves of evolution of the concentration of levoglucosenone as a function of the severity of the process for 3 species of wood: eucalyptus, a mixture of hardwoods and bark beetle spruce.

[0115] The concentrations in Table 4 and the curves in the show that the concentration of levoglucosenone obtained from a biomass of hardwoods and bark beetled Spruce is correlated with the severity of the process.

[0116] Conversely, the concentration in Table 4 and the evolution curve of the, show that the concentration of levoglucosenone obtained from eucalyptus biomass decreases drastically when the severity factor exceeds 3.96. However, it is observed that the concentration of levoglucosenone at 3.96 is significantly higher than the initial concentration. This suggests that the process does not completely degrade the molecule but that too high a severity tends to slow down the production of levoglucosenone in Eucalyptus.

[0117] In conclusion, there is variability between the different wood species studied. The method according to the invention can be applied to a plurality of wood species with different levoglucosenone concentrations depending on the wood considered and the severity applied. The results show that a severity factor between 3.5 and equal to or greater than 4.27 seems optimal for mixed hardwood or Spruce Bark beetle type woods.

[0118] Conversely, eucalyptus appears to be a raw material that is not very suitable for use in the process, because this wood does not withstand high severity factors, namely those above 3.96. However, conditions above 3.96 are required to promote the production of steam-cracked biomass intended for pelleting.

Claims

Steam cracking process from lignocellulosic biomass consisting mainly of a mixture of hardwoods and / or softwoods optimized for the production and recovery of levoglucosenone comprising the steps of: having a lignocellulosic biomass consisting mainly of a mixture of hardwoods and / or softwoods having a moisture content between 5 and 27% treating said biomass by steam cracking at a pressure between 10 and 25 bar, a temperature between 203 and 208°C and a severity factor between 3.5 and 4.5 until a powder is obtained. Recovery of levoglucosenone in the residual gases by condensation, in the powder by steam leaching or by extraction with a solvent. Steam cracking process according to claim 1, wherein the raw material is predominantly hardwood and softwood rich in glucose. Steam cracking process according to claim 1 or 2, wherein the residence time of said biomass in the steam cracking chamber is between 7 and 15 minutes Steam cracking process according to any one of claims 1 to 3, wherein the temperature at the steam cracking stage is between 206 and 208°C. Steam cracking process according to any one of claims 1 to 4 wherein the severity factor is between 4.05 and 4.

15. Steam cracking process according to any one of the preceding claims wherein at least a portion of the powder obtained in the steam cracking step is used for levoglucosenone recovery. Steam cracking process according to any one of the preceding claims in which a quantity of levoglusenone of between 1 and 10 mg / kg is obtained. Use of a steam cracked powder obtained by the process according to any one of claims 1 to 6, for the production of steam cracked granules suitable for use as biofuel. Use of levoglusenone obtained by the process according to any one of claims 1 to 7, as a precursor for the production of green solvent or antiviral molecules.

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