PROCESS FOR OPTIMIZING THE PRODUCTION OF LEVOGLUCOSENONE DURING STEAM CRACKING OF LIGNOCELLULOSIC BIOMASS

Abstract

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 and recovering the production of levoglucosenone during a steam cracking process.

Description

Title of the invention: METHOD FOR OPTIMIZING THE PRODUCTION OF LEVOGLUCOSENONE 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 fuels of the “black pellet” type with high calorific value from lignocellulosic biomass. More specifically, the invention relates to a method for optimizing steam cracking parameters allowing a higher ratio of levoglucosenone to be obtained during a steam cracking process. Field of invention

[0002] The transformation of lignocellulosic biomass (wood, agricultural residues, co-products of agriculture and agro-industry) 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 hearth, unlike biofuels) and to reduce environmental impacts (fossil CO2 emissions, with biomass without fertilizers or phytosanitary products).

[0003] Black pellets are cylinders resistant to moisture degradation, 1 to 3 cm long, with good mechanical strength allowing storage and handling similar to that of coal. Their combustion generates little ash, with a lower calorific value (LCV) 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 a sudden depressurization to provide a waterproof material when formed 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 called aqueous fractionation, solvolysis, hydrothermolysis, differs from steam cracking, or, in that it consists of using water at high temperature and high pressure in order to promote the disintegration and separation of the lignocellulosic matrix. This technique is not suitable for the production of black pellets since the products obtained are mainly 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 assimilated to 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 lignocellulosic biomass powder, dry, pretreated, without chemical additives, stable and economically viable for commodities such as energy, and even more so for products with higher added value.

[0009] It is 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] The methods known from the prior art propose methods for recovering co-produced molecules of interest. However, there is a need to obtain a process that not only allows the recovery of molecules produced incidentally during the steam cracking process but, on the contrary, specifically optimizes the production of said molecules of interest while maintaining parameters suitable for obtaining black granules. Statement of the invention

[0012] The inventors propose a process for producing steam-cracked granules whose parameters are oriented to optimize the production of levoglucosenone through autocatalyzed reactions, such as dehydration. Said autocatalyzed reactions are in particular produced and improved through steam cracking in a dry medium.

[0013] The proposed process has specific parameters in terms of drasticity (residence time, temperature), access to the substrate (granulometry, humidity) or composition of the raw materials (more xylose in hardwoods than in softwoods, more acidity in oak than in other hardwoods) allowing an optimization of the production of levoglucosenone.

[0014] 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.

[0015] Thus, the invention therefore consists of a process for producing granules by steam cracking of lignocellulosic biomass optimized to improve the production of an intermediate product such as levoglucosenone comprising the steps of: - having a lignocellulosic biomass having a humidity level 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 at 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 obtained - Recovery of levoglucosenone from residual gases and / or powder by steam leaching or solvent extraction.

[0016] Advantages of the invention

[0017] The process according to the invention proposes in a completely innovative way a double production: the optimized production of levoglucosenone at the same time as that of biofuel granules. 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.

[0018] On the one hand, the process advantageously presents the optimization of the production of levoglucosenone. This molecule is particularly interesting in the field of special polymers, perfumes and pharmaceutical active ingredients. Levoglucosenone is a green solvent precursor like the commercial product of the company CIRCA named Cyrene®.

[0019] To date, there is no process on an industrial scale and reality for transforming lignocellulosic biomass into high added value molecules, with a large-scale technical reality and economic viability, and a good environmental balance sheet, without risks. Molecules derived from biotechnology (enzymes, microorganisms) are almost the only chemical valorizations to date on a lignocellulosic basis.

[0020] 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 granules.

[0021] On the other hand, the process advantageously presents the possibility of producing, simultaneously with the optimized production of levoglucosenone, biofuel pellets, which makes the process economically viable.

[0022] Some pellet preparation processes require the use of synthetic chemical products. However, these chemical products are a source of pollution atmospheric by their production or their end of life, but also of toxicity. In addition, the absence of synthetic chemical products in the finished product, namely biofuel pellets, avoids the release of toxic products during its use: no contamination of enclosed spaces.

[0023] 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.

[0024] The use of steam-cracked biomass (wood in particular), which provides natural cohesion capacities for the preparation of black pellets, makes it possible to reduce environmental impacts (few or no chemicals, pressing processes without water and with less energy). Description of the embodiments

[0025] A first object of the invention relates to a steam cracking process from lignocellulosic biomass optimized for the production and recovery of levoglucosenone comprising the steps of: - have lignocellulosic biomass with a humidity level 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 at 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 obtained - recover levoglucosenone in the residual gases by condensation, in the powder by leaching, by steam or by extraction with a solvent.

[0026] By "lignocellulosic biomass" is meant a plant material whose major constituents are cellulose, hemicellulose and lignin. The proportions of these components vary according to the plant species. In the context of the invention, the lignocellulosic biomass of interest is mainly made up of glucose-rich hardwoods and softwoods.

[0027] By "dry steam cracking" is meant steam cracking carried out with lignocellulosic biomass whose moisture content is 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.

[0028] In one embodiment, the powder obtained in the steam cracking step is capable of being densified in order to obtain dense granules (“black pellets”) intended to be used as biofuel.

[0029] Levoglucosenone is a molecule derived from glucose which is notably produced during steam cracking under specific steam cracking conditions. This molecule is represented by the following formula:

[0030] [Chem.l]

[0031] 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. Thanks to the combination of raw materials rich in accessible glucose and specific steam cracking conditions (temperature, residence time, humidity, particle size to increase the production of these high value-added molecules), it is possible to optimize the production and recovery of this molecule.

[0032] The steam cracking process according to the invention allows: - 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 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 notably has the properties of being: dry, pre-treated, without chemical additives, stable and economically viable for commodities such as energy, therefore a fortiori viable for products with higher added value.

[0033] In a particular embodiment, the steam cracking process is carried out as follows:

[0034] - obtaining, from wood chips, fragments of wood whose dimension is between 0.5 and 14 mm and with a humidity level between 5 and 27%;

[0035] - continuous introduction of a predetermined volume per minute of said fragments of wood in a pressurized reactor, said reactor being supplied with substantially saturated water vapor whose pressure is between 16 and 19 bars and the temperature is between 203 and 208°C;

[0036] - exposure of the wood fragments introduced into said reactor to said steam of water for a sufficient time to obtain steam cracking of between 3 and 20 minutes and preferably between 7 and 15 minutes, the value of said exposure time and the value of the temperature of said substantially saturated steam being selected so that the severity factor is between 3.5 and 4.5, preferably between 4.05 and 4.15;

[0037] - continuous extraction from said reactor of the same predetermined volume of fragments of wood per minute, through a plurality of orifices opening into a conduit substantially at atmospheric pressure, so as to cause explosive decompression of said fragments of wood extracted from said reactor in said conduit;

[0038] - separation of said decompressed wood fragments and residual steam extracted from said reactor, said wood fragments obtained after separation forming a combustible material in powder form.

[0039] - Recovery of levoglucosenone in residual gases by condensation

[0040] The Treatment Severity Factor is defined by the formula:

[0041] FS=Logl0(time(min)*exp((T°C-100) / 14.75)).

[0042] 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.

[0043] In a first particular embodiment of the invention, the raw material of the steam cracking process is a lignocellulosic biomass rich in glucose. In one embodiment of the invention, the raw material is mainly hardwoods and softwoods rich in glucose. In a preferred embodiment, the raw material is a mixture of hardwoods, eucalyptus and unbarked oak. This raw material is particularly interesting since it allows the recovery of levoglucosenone (a molecule with high added value), at a concentration of between 3 and 9 mg / L. In a particular embodiment, the steam cracking process makes it possible to obtain a quantity of levoglucosenone of between 1 and 10 mg / L and more particularly between 5 and 10 mg / L.

[0044] 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.

[0045] In a particular embodiment, the levoglucosenone is recovered from the powder by leaching or by extraction with a solvent. In one embodiment advantageously, said solvent is a polar solvent. In another embodiment, the solvent in the recovery step is ethanol.

[0046] In a particular embodiment, at least a portion of the powder obtained in the steam cracking step is used in the levoglucosenone recovery step.

[0047] In a preferred embodiment, the biomass consists of more than 50% 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.

[0048] In another embodiment, the biomass consists of more than 50% of a mixture of glucose-rich hardwoods and softwoods.

[0049] 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.

[0050] 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.

[0051] In another particular embodiment of the invention, the severity factor at the steam cracking stage is between 4.05 and 4.15.

[0052] 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.

[0053] 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.

[0054] Indeed, levoglucosenone is used as a precursor for the production of Cyrene, a green solvent used in the chemical industry.

[0055] In addition, levoglucosenone constitutes a precursor of antiviral molecules highly sought after in the pharmaceutical industry. EXAMPLES

[0056] EXAMPLE 1: Study of the quantity of levoglu cosenone in condensates of different biomasses after steam cracking.

[0057] 1 - Materials and methods

[0058] A) Condensate samples.

[0059] 21 samples of condensates were studied. The codification, the species, the Operating conditions and production batch are given for each sample in Table 1.

[0060] [Tables 1] Sample name Species Severity conditions Production batch 10 / 01 / 20 Balance C6 Oak 3.91 = 203 °C; 7.5 min 1 10 / 01 / 20 Balance C8 Oak 3.96 = 208°C; 6 min 1 14 / 01 / 20 Balance CNE 6 Oak without bark 3.91 = 203 °C; 7.5 min 1 16 / 01 / 20 Balance ES6 Spruce bark beetle 3.91 = 203 °C; 7.5 min 1 16 / 01 / 20 Balance BE6 Wood B energy 3.91 = 203 °C; 7.5 min 1 17 / 01 / 20 Balance CHA6 Hornbeam 3.91 = 203 °C; 7.5 min 1 02 / 15 / 20 BBP balance 6 Wood B panels 3.91 = 203 °C; 7.5 min 1 04 / 14 / 20 EUC Balance 6 Eucalyptus 3.91 = 203 °C; 7.5 min 1 04 / 14 / 20 EUC balance 9 Eucalyptus 4.05 = 208°C; 7.5m in 1 04 / 14 / 20 EUC balance 3 Eucalyptus 3.67 = 195°C; 7.5m in 1 04 / 15 / 20 EUC Balance 8 Eucalyptus 3.96 = 208°C; 6min 1 04 / 15 / 20 Balance B AP 6 Wood A pallets 3.91 = 203 °C; 7.5 min 1 04 / 17 / 20 SHS balance 6pH3.11 Softwood sawdust Sc hilliger 3.91 = 203 °C; 7.5 min 1 04 / 17 / 20 SHP balance 6pH3.15 Softwood chip Schilliger 3.91 = 203 °C; 7.5 min 1 05 / 13 / 20 PF6 balance Forest chip 3.91 = 203 °C; 7.5 min 1 01 / 07 / 20 M2F assessment 5 Mixture of hardwoods 3.81 = 203°C; 6min 1 01 / 07 / 20 M2F balance 6 Mixture of hardwoods 3.91 = 203 °C; 7.5 min 1 07 / 01 / 20 M2F balance 8 Hardwood mixture 3.96 = 208°C; 6min 1 02 / 07 / 20 Assessment ES5 Bark spruce 3.81 = 203°C; 6min 2 02 / 07 / 20 ES6 assessment Spicy bark beetle 3.91 = 203 °C; 7.5 min 2 02 / 07 / 20 Assessment ES8 Bark spruce 3.96 = 208°C; 6min 2

[0061] Table 1: List of condensate samples studied

[0062] B) Methods used

[0063] Bl Analysis of sugars and carboxylic acids

[0064] The analysis is carried out on an Ultimate 3000 HPLC (Thermo), using an Aminex HPX-87H column (7.8 x 300 mm, 9 pm) heated to 50 °C. The samples are filtered through a 0.2 pm RC3 filter, 20 pL 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 carried out in UV at 210 and 280 nm, as well as with an RI4 detector set in positive mode.

[0065] The analysis time was 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 was therefore increased.

[0066] The analysis of sugars and carboxylic acids was carried out in 4 replicates.

[0067] B.2. Analysis of phenolic compounds

[0068] The analysis is carried out on an Ultimate 3000 HPLC (Thermo), using an Accucore C18 AQ column (3 x 100 mm, 2.6 pm) heated to 48 °C. The samples are filtered on a 0.2 pm RC filter, 1 pL is injected per analysis. The mobile phase consists of a gradient of 0.1% formic acid and acetonitrile.

[0069] The proportion of acetonitrile varies from 2 to 30% in 10 minutes with a flow rate of 0.8 mL / min. Detection is carried out in UV at 320, 210, 280 and 254 nm.

[0070] The quantification of levoglucosenone was disturbed at 210 nm by the presence of a co-eluted 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 in order to improve the detection limit of LGO and to overcome the co-elution which is no longer visible at 320 nm. The analysis of the phenolic compounds was carried out in 3 replicates.

[0071] B .3. Use of the metered addition method

[0072] The standard addition method is a quantitative analysis method, which replaces the calibration method when an effect of the sample matrix is observed. The retention time and / or the signal intensity can be modified. This method consists of carrying out a calibration range but from the sample and not in a solvent. The principle is to add to the sample a standard of known and increasing concentration of the molecule that one wishes to measure. 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.

[0073] B. 4. Analysis by mass spectrometry

[0074] Mass analysis is carried out on a Q-ToF5 LC (Agilent Infinity 1290 / 6545), using a Zorbax C18 column (2.1 x 50 mm, 1.8 pm) heated to 40 °C. The samples are filtered through a 0.2 pm RC filter, 1 pL 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 carried out 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.

[0075] B.5. Calculation of relative concentrations

[0076] The relative concentrations indicated were calculated according to equation 1. r0077] ... , Concentration of compound (ma / L}x 100 (At Luu / G Relative concentration in % = H \ / 2; Concentration of the components^ing / L) \ /

[0078] Per 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.

[0079] B.6. Statistics

[0080] The values presented correspond to averages calculated on the different replicates with their associated standard deviations. The orders of magnitude of the averages being 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 on 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.

[0081] C) Results

[0082] Cl Average composition obtained with a severity of 203°C and 7.5 min of residence time on different species (in mg / L)

[0083] The study of variability 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.

[0084] [Tables2] Species Levoglucosenone (mg / L) Mixed hardwoods 8.75 Eucalyptus 3.09 Unbarked oak 5.05 Forest chips 3.73 Bark-eaten spruce 1 2.85 Bark-eaten spruce 2 3.31 Hornbeam 2.63 Oak 1.94 Softwood sawmill chips 4.58 Wood A pallets 2.11 Wood B panels 0.94 Softwood sawmill sawdust 4.24 Wood B energy 0.72

[0085] Table 2: Average concentrations obtained with a severity of 3.91 on different species

[0086] It is observed that the 3 woods which produce the highest concentrations of levoglucosenone are: mixture of hardwoods, unbarked oak and sawmill softwood chips; the three lowest are: energy wood B, panel wood B and oak.

[0087] C.2. Analysis of the influence of process severity conditions

[0088] 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.

[0089] [Tables3] Compound Severity Levoglucosenone Eucalyptus 3.67 (7.5 min; 195°C) 1.6 3.91 (7.5 min; 203°C) 3.1 3.96 (6 min; 208°C) 6.8 4.05 (7.5 min; 208°C) 3.9 Hardwood Mix 3.81 (6 min; 203°C) 6.3 3.91 (7.5 min; 203°C) 8.7 3.96 (6 min; 208°C) 10.1 Spruce Bark Beetle 3.81 (6 min; 203°C) 2.6 3.91 (7.5 min; 203°C) 3.3 3.96 (6 min; 208°C) 4.9

[0090] Table 3: Average concentration of levoglucosenone (in mg / L) analyzed by LC-UV of 3 wood species

[0091] It would appear that the concentration of levoglucosenone 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.

[0092] Thus, according to this study, the severity conditions of 3.91 or 3.96 are optimal for increasing the concentration of levoglucosenone.

[0093] Conclusion:

[0094] 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 the hardwood mixtures, eucalyptus and unbarked oak. They have a levoglucosenone concentration between 3 and 9 mg / L. These woods are therefore of interest for the recovery of condensates in the recovery of levoglucosenone.

Claims

Claims

1. Process for the production of biofuel pellets comprising a steam cracking step from lignocellulosic biomass, characterized in that said process is optimized for the production and recovery of levoglucosenone comprising the steps of: - providing a lignocellulosic biomass having a moisture content of between 5 and 27% - treating said biomass by steam cracking at a pressure of between 10 and 25 bars, a temperature of between 203 and 208°C and a severity factor of 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.

2. A steam cracking process according to claim 1, wherein the raw material is predominantly glucose-rich hardwoods and softwoods.

3. Steam cracking process according to claim 1 or 2, wherein the residence time of said biomass in the steam cracking enclosure is between 7 and 15 minutes.

4. Steam cracking process according to one of claims 1 to 3, wherein the temperature in the steam cracking step is between 206 and 208°C.

5. Steam cracking process according to one of claims 1 to 4 in which the severity factor is between 4.05 and 4.

15.

6. Steam cracking process according to one of the preceding claims in which at least part of the powder obtained in the steam cracking step is used for the recovery of levoglucosenone.

7. Steam cracking process according to one of the preceding claims in which a quantity of levoglucosenone of between 1 and 10 mg / L is obtained.