PROCESS FOR OPTIMIZING THE PRODUCTION OF FURFURAL 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 furfural during a steam cracking process.

Description

Title of the invention: METHOD FOR OPTIMIZING THE PRODUCTION OF FURFURAL 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 furfural 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 granules 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 similar 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 dry, pre-treated, chemical additive-free, stable and economically viable lignocellulosic biomass powder for commodities such as energy, and even more so for higher value-added products.

[0009] It is known to those skilled in the art that treatment processes, such as steam cracking, allow the production of intermediate products with high 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 the co-produced furfural is recovered.

[0011] The known methods of the prior art propose processes 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 fortuitously 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 furfural through autocatalyzed reactions, such as dehydration. Said autocatalyzed reactions are in particular produced and improved through steam cracking in a dry environment.

[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 optimization of the production of furfural.

[0014] The furfural 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 vapo- cracking of lignocellulosic biomass optimized to improve the production of an intermediate product such as furfural 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 furfural from the residual gases and / or from the powder by steam leaching or by extraction with a solvent.

[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 furfural 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 Furfural production. The global furfural market was valued at $551 million in 2019 and is expected to reach $820 million by 2027, at a growth rate of 5.1% during the forecast period. On a basis of $1000-2000 / T, this currently represents 275-550 kTA, reaching 410-820 kTA in 2027. The expansion of this market can be explained in different ways: the volatility of petrochemical prices, the depletion of fossil resources and growing environmental concerns.

[0019] Furfural is an important renewable, non-petro-sourced chemical feedstock. It can be converted by a range of catalytic reductions into a variety of solvents, polymers, fuels and other chemicals. The main share of the furfural market is the furfuryl alcohol application segment which is the predominant application: 88% of the furfural produced is converted to furfuryl alcohol, related to the production of foundry resins. Furfural as a solvent is the second largest application of furfural worldwide, in the refining of lube oils, butadiene extraction and various chemical extraction processes. Furfural is also used to manufacture tetrahydrofuran (THF), a specialty chemical precursor to a wide range of chemical syntheses.The rapid growth in the construction industry is expected to further increase the demand for furfural through its use in various refractory materials such as fiberglass composites, ceramics, and bricks in the near future.

[0020] Regarding raw materials, more than 50% of the market share came from xylose contained in sugarcane bagasse, the largest market share in 2017, followed by xylose from corn cob.

[0021] To date, there is no process on an 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 sheet, without risks. Molecules derived from biotechnology (enzymes, microorganisms) are almost the only chemical valorizations to date on a lignocellulosic basis.

[0022] Although the recovery of furfural 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.

[0023] On the other hand, the process advantageously allows simultaneously the optimized production of furfural, and the production of biofuel pellets, which makes the process economically viable.

[0024] Some pellet preparation processes require the use of synthetic chemical products. However, these chemical products are a source of both atmospheric pollution through their production or end of life, and toxicity. In addition, the absence of synthetic chemical products in the finished product, namely biofuel pellets, prevents the release of toxic products during its use: no contamination of enclosed spaces.

[0025] 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.

[0026] 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

[0027] A first object of the invention relates to a steam cracking process from lignocellulosic biomass optimized for the production and recovery of furfural 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 temperature is between 203 and 208°C and a severity factor between 3.5 and 4.5, and preferably between 4.0 and 4.2 until a powder is obtained - recover furfural from residual gases by condensation, from powder by leaching, by steam or by extraction with a solvent.

[0028] 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 hardwoods and softwoods rich in xylose.

[0029] 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 the 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.

[0030] In a particular 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.

[0031] Furfural is a molecule derived from xylose which is notably produced during steam cracking under specific steam cracking conditions. This molecule is represented by the following formula:

[0032] [Chem.l] 4

[0033] 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 molecules such as furfural. Thanks to the combination of raw materials rich in accessible xylose 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.

[0034] The steam cracking process according to the invention allows: - on the one hand to optimize the production and recovery of a product such as furfural 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, due to 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 the following properties: dry, pre-treated, without chemical additives, stable and economically viable for commodities such as energy, and therefore a fortiori viable for products with higher added value.

[0035] In a particular embodiment, the steam cracking process is carried out as follows:

[0036] - 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%;

[0037] - 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 whose temperature is between 203 and 208°C;

[0038] - exposure of the wood fragments introduced into said reactor to said water vapor 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;

[0039] - 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;

[0040] - separation of said decompressed wood fragments and residual steam extracted from said reactor, said fragments of wood obtained after separation forming a combustible material in powder form;

[0041] - recovery of furfural in residual gases by condensation.

[0042] The Treatment Severity Factor is defined by the formula:

[0043] FS=Logl0(time(min)*exp((T°C-100) / 14.75)).

[0044] 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.

[0045] In a first particular embodiment of the invention, the raw material of the steam cracking process is a lignocellulosic biomass rich in xylose. In one embodiment of the invention, the raw material is mainly hardwoods and softwoods rich in xylose and poor in galactose and mannose. 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 furfural (a high added value molecule), at a yield greater than 1% of furfural weight per weight of lignocellulosic dry matter. In a particular embodiment, the steam cracking process makes it possible to obtain a Furfural yield of between 1% and 5% and more particularly between 2% and 4%.

[0046] In a particular embodiment, the furfural 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.

[0047] In a particular embodiment, at least a portion of the powder obtained in the steam cracking step is used in the furfural recovery step.

[0048] In a preferred embodiment, the biomass consists of more than 50% xylose-rich biomass. The powder obtained can be used for the recovery of furfural by leaching and / or by extraction with a solvent such as ethanol.

[0049] In another embodiment, the biomass consists of more than 50% of a mixture of hardwoods and softwoods rich in xylose and poor in galactose and mannose.

[0050] 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.

[0051] 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.

[0052] In another particular embodiment of the invention, the severity factor at the steam cracking stage is between 4.05 and 4.15.

[0053] 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.

[0054] A third object of the invention is the use of furfural obtained by the process of the invention, as a precursor for the production of at least one of the following products: solvents, polymers, fuels or anti-UV molecules.

[0055] Indeed, furfural can be functionalized into bio-sourced anti-UV molecules that are highly sought after by the cosmetics industry. EXAMPLES

[0056] EXAMPLE 1: Study of the quantity of Furfural 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 CNE6 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 Assessment BBP6 Wood B panels 3.91 =203 °C; 7.5 min 1 04 / 14 / 20 Balance EUC6 Eucalyptus 3.91 =203 °C; 7.5 min 1 04 / 14 / 20 EUC9 balance Eucalyptus 4.05 = 208°C; 7.5min 1 04 / 14 / 20 EUC3 balance Eucalyptus 3.67 = 195°C; 7.5min 1 04 / 15 / 20 EUC8 balance Eucalyptus 3.96 = 208°C; 6min 1 04 / 15 / 20 BAP6 assessment Wood Pallets 3.91 =203 °C; 7.5 mins 1 04 / 17 / 2020 SHS6 pH3.11 Schilliger softwood sawdust 3.91 = 203 °C; 7.5 min 1 04 / 17 / 2020 SHP6 pH3.15 Schilliger softwood chip 3.91 = 203 °C; 7.5 min 1 05 / 13 / 2020 PF6 Forest chip 3.91 = 203 °C; 7.5 min 1 07 / 01 / 2020 M2F5 Hardwood mix 3.81 = 203°C; 6 min 1 07 / 01 / 2020 M2F6 Hardwood mix 3.91 = 203 °C; 7.5 min 1 07 / 01 / 2020 M2F8 Hardwood mix 3.96 = 208°C; 6min 1 02 / 07 / 20 Assessment ES5 Bark spruce 3.81 = 203°C; 6min 2 02 / 07 / 20 Assessment ES6 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 line of based 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 can affect the quality of the chromatographic peaks, the analysis time has therefore been 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] B .3. Use of the metered addition method

[0071] 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.

[0072] B. 4. Analysis by mass spectrometry

[0073] 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.

[0074] B.5. Calculation of relative concentrations

[0075] The relative concentrations indicated were calculated according to equation 1. Compound concentration (mg / L) x 100 Relative concentration (in %) — ——-----------------------------------(1) S Concentration of compounds (mg / L)

[0076] Per sample, and for each compound, the ratio of the concentration (of the compound) on the sum of the concentrations was calculated and reduced to a percentage.

[0077] B.6. Statistics

[0078] 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 the values around the average, whatever its order of magnitude. It is often expressed as a percentage.

[0079] C) Results

[0080] Cl Average yield obtained with a severity of 203°C and 7.5 min of residence time on different species (in g of furfural per 100 g of dry matter introduced or %)

[0081] 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 yields obtained are presented in Table 2.

[0082] [Tables2] Species Furfural (%) Mixed hardwoods 4.2 Eucalyptus 2.1 Unbarked oak 1.5 Forest chips 0.8 Bark-eaten spruce 1 0.2 Bark-eaten spruce 2 0.4 Hornbeam 0.5 Oak 0.5 Sawmill softwood chips 0.3 Wood A pallets 0.2 Wood B panels 0.2 Sawmill softwood sawdust 0.2 Energy wood B 0.5

[0083] Table 2: Average yields obtained with a severity of 3.91 on different species

[0084] It is observed that the 3 woods which produce the highest yields of Furfural are: mixture of hardwoods, unbarked oak and sawmill softwood chips; the three lowest are: energy wood, panel wood and Scolyte Spruce.

[0085] C.2. Analysis of the influence of process severity conditions

[0086] The influence of process severity conditions was studied on 3 different woods: eucalyptus, mixed hardwoods and bark beetle spruce. Table 3 shows the average yield of the 3 woods used to study the impact of severity conditions.

[0087] [Tables3] Compound Severity Furfural (yield %) Eucalyptus 3.67 (7.5 min; 195°C) 0.484 3.91 (7.5 min; 203°C) 2.123 3.96 (6 min; 208°C) 3.396 4.05 (7.5 min; 208°C) 3.036 Hardwood Mixture 3.81 (6 min; 203°C) 3.300 3.91 (7.5 min; 203°C) 4.212 3.96 (6 min; 208°C) 4.592 Spruce Bark Beetle 3.81 (6 min; 203°C) 0.169 3.91 (7.5 min; 203°C) 0.357 3.96 (6 min; 208°C) 0.736

[0088] Table 3: Average yield of Furfural (in %) analyzed in LC-UV of 3 species of wood

[0089] It would appear that the concentration of furfural increases up to the 3.96 severity condition, and the 4.05 severity condition is too severe and begins to degrade this compound.

[0090] Thus, according to this study, severity conditions of 3.91 or 3.96 are optimal for increasing furfural concentration.

[0091] Conclusion:

[0092] The results of the study show that there is variability between the different wood species studied for furfural production. Three wood species provide after steam cracking generally higher concentrations of furfural than other woods, these are hardwood mixtures, eucalyptus and unbarked oak. The yields obtained in furfural are greater than 1%. These woods are therefore of interest for the valorization of condensates in the recovery of furfural.

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 Furfural 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, a temperature of between 203 and 208°C and a severity factor of between 3.5 and 4.5 until a powder is obtained - recovering the furfural in the residual gases by condensation, in the powder by leaching, by steam or by extraction with a solvent.

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

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 furfural.

7. Steam cracking process according to one of the preceding claims in which a furfural yield greater than 1% of weight of furfural per weight of lignocellulosic dry matter is obtained.