Conversion of biomass-derived hydrocarbon feedstocks to produce adipic acid

Abstract

A method for converting biomass to adipic acid is disclosed, which comprises the following steps in sequence: a) treating biomass to produce ethanol and CO2; b) converting the ethanol obtained at the end of step a) to obtain 1,3-butadiene and dihydrogen; and c) synthesizing adipic acid from the 1,3-butadiene and dihydrogen obtained at the end of step b) and the CO2 obtained at the end of step a).

Description

[Technical Field]

[0001] The present invention relates to a method for processing biomass, preferably lignocellulosic biomass, to produce adipic acid from a single bio-based carbon source while maximizing carbon yield. [Background technology]

[0002] The method for fermenting lignocellulosic biomass makes it possible to produce ethanol and carbon dioxide (CO2), which can be advantageously converted into adipic acid compared to the prior art.

[0003] Adipic acid is a chemical compound used as a raw material as an intermediate compound, in particular for the synthesis of polyamides, polyesters or polyurethanes.

[0004] To date, several methods for producing adipic acid are known and used industrially. The main industrial method involves oxidizing cyclohexane with oxygen to give the intermediate compounds cyclohexanol and cyclohexanone, generally a mixture of these two compounds. In a subsequent step, the intermediate compounds cyclohexanol and cyclohexanone are oxidized with nitric acid in the presence of a catalyst to give adipic acid.

[0005] US Patent No. 5,949,999 describes a route for the synthesis of adipic acid from biomass, first forming catechol, which is then converted to cis,cis-muconic acid, which can undergo reduction to form adipic acid.

[0006] Patent application WO 02 / 04999 describes a route for the synthesis of adipic acid from biomass via the production of isobutanol, which is then converted to 1,3-butadiene, which is further converted to adiponitrile and then finally to adipic acid.

[0007] 1,3-Butadiene is a strategically important product for the synthesis of adipic acid. This compound can be obtained by dehydrating bioethanol. This type of process is disclosed, inter alia, in Patent Documents 3 to 5. It is well known that bioethanol can be produced by fermentation of sugars originating from various biomass. However, fermentations that produce ethanol generally do not have a good "carbon" yield, as part of this carbon is lost in the form of CO2. Furthermore, ethanol produced from "first generation" (1G) biomass faces competition from the food processing industry, which loses a large part of this resource in the form of greenhouse gases, which is even more problematic.

[0008] The object of the present invention is to overcome all of the above drawbacks, more specifically to develop a method for processing "second generation" (2G) lignocellulosic biomass to produce adipic acid from fermentation-derived ethanol and CO2.

[0009] The object of the present invention is to overcome all of the above-mentioned drawbacks, more specifically to develop a method for processing biomass, preferably "second generation" (2G) lignocellulosic biomass, to produce adipic acid from fermentation-derived ethanol and CO2. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] U.S. Patent No. 5,487,987 [Patent Document 2] US Patent Application Publication No. 2011 / 0172475 [Patent Document 3] International Publication No. 21193457 [Patent Document 4] International Publication No. 21006252 [Patent Document 5] International Publication No. 21052968 Summary of the Invention [Means for solving the problem]

[0011] (Subject matter of the invention) In the aforementioned context, a first objective of the present description is to overcome the problems of the prior art and upgrade bio-based carbon, in particular in the form of CO2, to high-value added compounds, in particular adipic acid. Specifically, the present invention relates to a method for the production of adipic acid according to a sequence of steps, which makes it possible to convert biomass into ethanol and CO2, and then convert these products into adipic acid, using one or more of the following steps in addition to or instead of some of the conventional steps for the synthesis of adipic acid:

[0012] According to a first aspect, the present invention relates to a method for converting biomass, preferably lignocellulosic biomass, into adipic acid, comprising the following steps in succession: a) processing biomass to produce ethanol and CO2; b) converting the ethanol obtained at the end of step a) to obtain 1,3-butadiene; c) synthesis of adipic acid from 1,3-butadiene obtained at the end of step b) and CO2 obtained at the end of step a).

[0013] The invention is based on upgrading the CO2 by-product formed during the fermentation of biomass to give ethanol, optionally recycling the water generated during the dewatering step in other steps of the method according to the invention. The invention therefore comprises a series of individual operations that serve to maximize the carbon yield of the synthesis of adipic acid from biomass, preferably lignocellulosic biomass, and even more preferentially from "second generation" (2G) lignocellulosic biomass.

[0014] According to one or more embodiments, step a) comprises the following substeps: a1) pretreating biomass to obtain a pretreated substrate; a2) enzymatically or chemically hydrolyzing the pretreated substrate obtained at the end of step a1) to obtain an enzymatically or chemically hydrolyzed must; a3) Alcoholic fermentation of the must of the enzymatic or chemical hydrolysis obtained at the end of step a2) to obtain ethanol and CO2.

[0015] According to one or more embodiments, substep a1) is carried out by steam explosion under acid conditions at a temperature between 150° C. and 250° C. for a period between 5 and 30 minutes.

[0016] According to one or more embodiments, substep a2) is carried out by enzymatic hydrolysis in the presence of Trichoderma reesei cellulase.

[0017] According to one or more embodiments, step b) comprises the following substeps: b1) a step for converting ethanol into acetaldehyde, comprising at least a reaction section and a separation section, the reaction section being fed with at least a portion of the ethanol-rich effluent resulting from step b5) and being operated in the presence of a catalyst at a pressure of 0.1 MPa to 1.0 MPa and at a temperature of 200°C to 500°C, the separation section making it possible to separate the effluent of the reaction section into at least a gaseous hydrogen effluent and a liquid ethanol / acetaldehyde effluent; b2) a step of converting the ethanol to butadiene, comprising at least a reaction section and a separation section; the reaction section is fed with at least a portion of the ethanol / acetaldehyde effluent resulting from step b1), a liquid ethanol-rich effluent resulting from step b3) and a portion of the acetaldehyde-rich effluent resulting from step b5), and is operated in the presence of a catalyst at a temperature of 300°C to 400°C and a pressure of 0.1 MPa to 1.0 MPa, the feed flow rate being adjusted so that the ethanol / acetaldehyde molar ratio at the inlet of the reaction section is 1 to 5, and the separation section makes it possible to separate the effluent of the reaction section into at least a gaseous effluent and a liquid effluent; b3) processing hydrogen, comprising at least a compression section, a gas / liquid scrubbing section, and a distillation section, wherein the compression section compresses the hydrogen effluent from step b1) to a pressure of 0.1 MPa to 1.0 MPa, and the gas / liquid scrubbing section receives a portion of the ethanol-rich effluent from step b5) and a portion of the ethanol / acetaldehyde effluent from step b1) at a temperature of 15°C to -30°C, and receives the compressed hydrogen effluent at a temperature of 25°C to 60°C; producing at least a liquid ethanol-rich effluent and a purified hydrogen effluent; b4) extracting butadiene, comprising at least a compression section and a gas / liquid scrubbing section; the compression section compresses the gaseous effluent resulting from step b2) to a pressure of 0.1 MPa to 1.0 MPa, the gas / liquid scrubbing section comprising a scrubbing column, which feeds an ethanol stream consisting of the ethanol feedstock from the process and / or a portion of the ethanol effluent resulting from step b5) at a temperature of 20°C to -20°C to the top, and the cooled gaseous effluent resulting from step b2) to the bottom, a distillation section operated at a pressure of 0.1 MPa to 1 MPa and fed with at least the liquid effluent resulting from step b2) and the liquid effluent from the gas / liquid scrubbing section, and step b4) produces at least one gaseous by-product effluent, a crude butadiene effluent and an ethanol / acetaldehyde / water effluent; b4') a first purification step for butadiene, comprising at least a gas / liquid scrubbing section, which is fed at the bottom with a crude butadiene effluent from b4) and at the top with a water stream originating outside the process for producing butadiene and / or which may be part of the water effluent from step b5), said scrubbing section producing a pre-purified butadiene effluent at the top and a wastewater effluent at the bottom; b4") a subsequent step of purifying butadiene, to which at least the pre-purified butadiene effluent resulting from step b4') is fed to produce at least a purified butadiene effluent; b5) treating the effluent, receiving at least the water / ethanol / acetaldehyde raffinate resulting from step b5') to produce at least an ethanol-rich effluent, an acetaldehyde-rich effluent, and a water-rich effluent; b5') removing impurities and brown oil; feeding at least the ethanol / acetaldehyde / water effluent resulting from step b4) and the water-rich effluent resulting from step b5) to produce at least a water / ethanol / acetaldehyde rafinate, a light brown oil effluent and a heavy brown oil effluent; b6) a step of washing with water; the gaseous by-product effluent resulting from step b4) and also a portion of the water-rich effluent resulting from said step b5) are fed to produce at least one alcoholic water effluent.

[0018] According to one or more embodiments, step c) comprises the following substeps: c1) a C-C coupling step between two molecules of CO2 and one molecule of 1,3-butadiene; c2) isolating the hexenedioic acid; c3) reducing the hexenedioic acid formed in step c1) to give adipic acid.

[0019] According to one or more embodiments, sub-step c1) is carried out in a solvent in the presence of a metal precursor, a ligand and a reducing agent and is characterized in that: - the metal precursor is a nickel(II) salt; - the ligand is a bidentate dinitrogen ligand; - the reducing agent is a metal selected from zinc or manganese; The solvent is a polar aprotic solvent.

[0020] According to one or more embodiments, substep c1) is carried out at a temperature between 5°C and 70°C.

[0021] According to one or more embodiments, sub-step c3) is carried out in the presence of a catalyst and a reducing agent, said catalyst being palladium on activated carbon and the reducing agent being purified hydrogen originating from sub-step b3).

[0022] According to one or more embodiments, the biomass is lignocellulosic biomass.

[0023] According to a second aspect, the present invention relates to a plant suitable for carrying out the method according to the invention, said plant comprising: - a first reaction section, which makes it possible to produce ethanol and CO2 from biomass; - a second reaction section, which converts ethanol to 1,3-butadiene and diatomic hydrogen; and - The third reaction section allows adipic acid to be produced from 1,3-butadiene, CO2 and diatomic hydrogen. DETAILED DESCRIPTION OF THE INVENTION

[0024] (List of drawings) FIG. 1 shows a schematic diagram of a method and plant according to the invention, making it possible to produce adipic acid from biomass, preferably lignocellulosic biomass.

[0025] (Description of the embodiment) Embodiments of a method according to a first aspect of the present invention and a plant according to a second aspect of the present invention will now be described in detail. In the following detailed description, numerous specific details are disclosed to provide a deeper understanding of the method and plant. However, it will be apparent to those skilled in the art that the method and plant can be practiced without these specific details. In other cases, well-known features have not been described in detail to avoid unnecessarily complicating the description.

[0026] In this patent application, the term "to comprise" is synonymous with (means the same as) "to include" and "to contain" and is inclusive or open and does not exclude other elements not listed. The term "to comprise" is understood to include the exclusive and closed term "to consist of." Furthermore, in the present description, an effluent comprising essentially or solely compound A corresponds to an effluent comprising at least 90% by weight, preferably at least 95% by weight, and highly preferably at least 99% by weight of compound A.

[0027] In this patent application, groups of chemical elements are given by default according to the CAS classification (CRC Handbook of Chemistry and Physics, published by CRC Press, editor-in-chief DR Lide, 81st edition, 2000-2001). For example, group VIII (or group VIIIB) according to the CAS classification corresponds to metals from columns 8, 9 and 10 according to the new IUPAC classification; group VIB according to the CAS classification corresponds to metals from column 6 according to the new IUPAC classification.

[0028] In this patent application, "biomass" means any biologically produced feedstock, preferably produced by fermentation of sugars (saccharose, glucose, fructose and sucrose) originating, for example, from sugar-producing plant crops such as sugarcane, or from beetroot, or from starch plants (starch), or from lignocellulosic biomass, or from hydrolyzed cellulose (mainly glucose, xylose, galactose), and containing variable amounts of water. The biomass is preferably lignocellulosic biomass, and even more preferentially "second generation" (2G) lignocellulosic biomass.

[0029] The present invention can be defined as a process comprising a series of reaction steps making it possible to produce adipic acid from biomass, preferably lignocellulosic biomass, and even more preferentially from "second generation" (2G) lignocellulosic biomass. More particularly, the present invention relates to a process for converting biomass to adipic acid, comprising the following steps in succession: a) processing biomass to produce ethanol and CO2; b) converting the ethanol obtained at the end of step a) to obtain 1,3-butadiene; c) synthesis of adipic acid from 1,3-butadiene obtained at the end of step b) and CO2 obtained at the end of step a).

[0030] Furthermore, the invention can also be defined as a plant capable of carrying out the method according to the invention, as shown in FIG. 1, said plant comprising in particular: - a first reaction section (2) making it possible to produce ethanol (3) and CO2 (4) from biomass (1), preferably lignocellulosic biomass; - a second reaction section (5) for converting ethanol (3) into 1,3-butadiene (6) and hydrogen (9); and - a third reaction section (7), which makes it possible to produce adipic acid (8) from 1,3-butadiene (6), hydrogen (9) and CO2 (4).

[0031] (First reaction section (step a) of the method according to the invention) The first reaction section (2) makes it possible to produce ethanol (3) and CO2 (4) from biomass (1).

[0032] In an embodiment according to the present invention, the biomass used in the method is lignocellulosic biomass, preferably "second generation" lignocellulosic biomass. Wood from hardwoods and cereal straw are the most commonly used substrates. They consist primarily of approximately 40% to 50% cellulose, 20% to 25% hemicellulose, and 15% to 25% lignin. Other sources can be used, including dedicated forestry crops, residues from plants used to produce alcohol, sugar, and cereals, residues from the paper industry, and products of the conversion of cellulosic and lignocellulosic materials.

[0033] In one embodiment according to the invention, the method for converting biomass to ethanol more particularly comprises the following sub-steps: a1) pretreating biomass to obtain a pretreated substrate; a2) enzymatically or chemically hydrolyzing the cellulose residue obtained at the end of step a1) to obtain an enzymatically or chemically hydrolyzed must; a3) Alcoholic fermentation of the must of the enzymatic or chemical hydrolysis obtained at the end of step a2) to obtain ethanol and CO2.

[0034] (Physicochemical pretreatment (step a1)) The pretreatment step a1) produces a pretreated substrate containing the sugars contained in the hemicellulose in the form of monomers, essentially pentoses such as xylose and arabinose, and hexoses such as galactose, mannose, and glucose, improving the accessibility of the cellulose embedded in the lignin and hemicellulose matrix. A wide range of techniques are available, including acid cooking, alkaline cooking, steam explosion, and organosolv pulping. The effectiveness of the pretreatment is measured by the hemicellulose recovery rate and the susceptibility of the cellulose residue to hydrolysis. Under mild conditions, acid pretreatment with steam explosion is best suited, as it allows complete recovery of pentoses and good accessibility of the cellulose to hydrolysis.

[0035] Preferentially, pretreatment step a1) is carried out by steam explosion under acidic conditions, advantageously at a temperature of 150°C to 250°C, for a period of advantageously 5 to 30 minutes. In this embodiment, step a1) makes it possible to convert hemicellulose into monomers, while at the same time minimizing losses of, in particular, furfural and the main sugar, xylose. The released sugars are then extracted by washing in an aqueous phase. The solid residue (i.e., the pretreated substrate) obtained at the end of the extraction then contains only cellulose and lignin.

[0036] (Enzymatic hydrolysis or chemical hydrolysis (step a2)) The pretreated substrate obtained at the end of step a1) is hydrolyzed either with acids (i.e. chemically) or enzymatically with cellulolytic and / or hemicellulolytic enzymes. Microorganisms, such as fungi belonging to the genera Trichoderma, Aspergillus, Penicillium, or Schizophyllum, or anaerobic bacteria, for example, belonging to the genus Clostridium, produce these enzymes, which are suitable for the total hydrolysis of plant polymers, and contain in particular cellulases and xylanases.

[0037] The acidic route, carried out with strong acids, more particularly sulfuric acid, is effective but requires large amounts of chemical products (acid, then base for neutralization). Enzymatic hydrolysis does not have this drawback; moreover, it can be carried out under mild conditions and is effective.

[0038] Preferentially, the pretreated substrate, with or without liberation from the hydrolyzed hemicellulose fraction, and, where appropriate, lignin, are hydrolyzed with cellulolytic and / or hemicellulolytic enzymes produced by specialized strains. When the carbon-based substrate is derived from cellulosic or lignocellulosic biomass, Trichoderma reesei cellulases are most effective and suitable. The pretreated substrate to be hydrolyzed is suitably suspended in an aqueous phase at a dry matter ratio of preferably 6% to 25%, preferably 10% to 20%, and the pH is adjusted to 4 to 5.5, preferably 4.8 to 5.2, and the temperature is adjusted to 40 to 60°C, preferably 45 to 50°C. The hydrolysis reaction is initiated by adding cellulase; the amount typically used is 10 to 30 mg of secreted protein per gram of pretreated substrate weight. The reaction generally lasts for 15 to 48 hours, depending on the effectiveness of the pretreatment, the composition of the cellulase mixture, and the amount of enzyme added. The reaction is monitored by assaying the released sugars, especially glucose. The sugar solution (mast) is then separated by filtration or centrifugation from the non-hydrolyzed solid fraction, which consists essentially of lignin; this must is used for ethanol fermentation. When the cellulose fraction is liberated from the hydrolyzed hemicellulose during the processing step, glucose is the major sugar contained in the must.

[0039] (Fermentation (step a3)) Alcoholic fermentation is a biochemical process in which the sugars (carbohydrates, mainly glucose) contained in the must are converted to alcohol, preferentially ethanol, in an air-free liquid medium (anaerobic). The process of fermenting sugars to obtain ethanol is well known to those skilled in the art.

[0040] Alcoholic fermentation is preferentially carried out at temperatures between 25° C. and 32° C. For a more complete description of traditional fermentation methods, reference may be made to the textbook "Biofuels: Current Status, Prospects and Development Challenges" by Daniel Ballerini, published in 2006 by Technip.

[0041] Typically, ethanol is separated from the fermentation must by distillation, and the residue consists of stillage. Periodic or continuous distillation of ethanol is necessary because ethanol above 14% can "poison" certain yeasts, resulting in productivity losses. Distillation is carried out to produce an ethanol feedstock suitable for the dehydration methods described below.

[0042] The CO2 is recovered in gas form at the outlet of the fermenter. According to an essential aspect of the invention, the CO2 obtained at the end of the fermentation step is at least partially sent to the adipic acid synthesis step (step c)) of the method according to the invention. The CO2 may be compressed by a compressor before storage or use.

[0043] The ethanol fermentation residue, after separation from the ethanol, may be used as an inducing carbon source or as the main carbon source for enzyme production, the concentration of which is preferably adjusted to obtain the carbon source concentration best suited to the method for producing cellulolytic and / or hemicellulolytic enzymes.

[0044] The steps of enzymatic hydrolysis and fermentation may be carried out simultaneously (simultaneous saccharification and fermentation (SSF) process), in which case they are advantageously followed by steps of distillation and separation of the alcohol obtained.

[0045] (Second reaction section (step b) of the process according to the invention) The second reaction section (5) makes it possible to produce 1,3-butadiene (6) from the ethanol (3) produced in the first reaction section (2). Numerous processes exist in the literature that make it possible to obtain 1,3-butadiene from ethanol, in particular the process disclosed in patent application FR3026100, which is described here by way of example.

[0046] Advantageously, the ethanol feedstock used in step b) of the process according to the invention is a feedstock containing at least 80% by weight, preferentially at least 90% by weight, preferably at least 93% by weight of ethanol relative to the total weight of the feedstock. Highly preferably, said ethanol feedstock meets the EN 15376 fuel ethanol specification.

[0047] In one embodiment according to the invention, step b) of the method according to the invention comprises the following substeps: b1) a step for converting ethanol to acetaldehyde, comprising at least a reaction section and a separation section, the reaction section being fed with at least a portion of the ethanol-rich effluent resulting from step b5) and being operated in the presence of a catalyst at a pressure of 0.1 MPa to 1.0 MPa and at a temperature of 200°C to 500°C, the separation section making it possible to separate the effluent of the reaction section into at least a gaseous hydrogen effluent and a liquid ethanol / acetaldehyde effluent; b2) step of converting to butadiene; comprising at least a reaction section and a separation section; the reaction section is fed with at least a portion of the ethanol / acetaldehyde effluent resulting from step b1), a liquid ethanol-rich effluent resulting from step b3) and a portion of the acetaldehyde-rich effluent resulting from step b5), and is operated in the presence of a catalyst at a temperature of 300°C to 400°C and a pressure of 0.1 MPa to 1.0 MPa, the feed flow rate being adjusted so that the ethanol / acetaldehyde molar ratio at the inlet of the reaction section is between 1 and 5, and the separation section makes it possible to separate the effluent of the reaction section into at least a gaseous effluent and a liquid effluent: b3) processing hydrogen; comprising at least a compression section and a gas / liquid scrubbing section; the compression section compresses the hydrogen effluent from step b1) to a pressure of 0.1 MPa to 1.0 MPa, and the gas / liquid scrubbing section receives a portion of the ethanol-rich effluent from step b5) and a portion of the ethanol / acetaldehyde effluent from step b1) at a temperature of 15°C to -30°C, and receives the compressed hydrogen effluent at a temperature of 25°C to 60°C; producing at least a liquid ethanol-rich effluent and a purified hydrogen effluent; b4) extracting butadiene, comprising at least a compression section, a gas / liquid scrubbing section, and a distillation section; the compression section compresses the gaseous effluent resulting from step b2) to a pressure of 0.1 MPa to 1.0 MPa; the gas / liquid scrubbing section comprises a scrubbing column, and is fed at its top with an ethanol stream consisting of the ethanol feedstock from the process and / or a portion of the ethanol effluent resulting from step b5) at a temperature of 20°C to -20°C, and at its bottom with the cooled gaseous effluent resulting from step b2); the distillation section is operated at a pressure of 0.1 MPa to 1 MPa and is fed with at least the liquid effluent resulting from step b2) and the liquid effluent from the gas / liquid scrubbing section, and step b4) produces at least one gaseous by-product effluent, a crude butadiene effluent, and an ethanol / acetaldehyde / water effluent; b4') a first purification step for butadiene, comprising at least a gas / liquid scrubbing section, which is fed at its bottom with a crude butadiene effluent from b4) and at its top with a water stream, which may be a water stream originating outside the process for producing butadiene and / or part of the water effluent from step b5), said scrubbing section producing a pre-purified butadiene effluent at its top and a wastewater effluent at its bottom; b4″) a subsequent step of purifying butadiene, to which at least the pre-purified butadiene effluent resulting from step b4′) is fed to produce at least a purified butadiene effluent; b5) treating the effluent, receiving at least the water / ethanol / acetaldehyde rafinate resulting from step b5') to produce at least an ethanol-rich effluent, an acetaldehyde-rich effluent and a water-rich effluent; b5') removing impurities and brown oil; feeding at least the ethanol / acetaldehyde / water effluent resulting from step b4) and the water-rich effluent resulting from step b5) to produce at least a water / ethanol / acetaldehyde rafinate, a light brown oil effluent and a heavy brown oil effluent; b6) a step of washing with water, to which the gaseous by-product effluent resulting from step b4) and also a portion of the water-rich effluent resulting from step b5) are fed, to produce at least one alcoholic-water effluent.

[0048] Steps b1) to b6) are described in detail below.

[0049] (Step b1) Step of converting ethanol into acetaldehyde) According to one embodiment according to the invention, step b1) of converting ethanol to acetaldehyde comprises at least a reaction section and a separation section, the reaction section being fed with at least a portion of the ethanol-rich effluent resulting from step b5), said portion preferably constituting at least 10% of the stream of said ethanol-rich effluent resulting from step b5), and possibly advantageously being fed with at least a portion of said ethanol feedstock, and a separation section making it possible to separate the effluent of said reaction section into at least a gaseous hydrogen effluent and a liquid ethanol / acetaldehyde effluent.

[0050] Said reaction section makes it possible to convert ethanol to acetaldehyde in the presence of a catalyst, preferably a catalyst consisting of a mixture of chromium oxide and copper oxide, or any other suitable catalyst, which are well known to those skilled in the art.

[0051] The reaction section is operated at a pressure of 0.1 MPa to 1.0 MPa, preferably 0.1 MPa to 0.5 MPa, preferably 0.1 MPa to 0.3 MPa, and at a temperature of 200°C to 500°C, preferentially 250°C to 300°C.

[0052] Preferably, the conversion of ethanol is 30-40% and the selectivity is 85-100% towards acetaldehyde, preferably 90-95% towards acetaldehyde. The effluent of the reaction section also contains by-products such as crotonaldehyde, butyraldehyde, diethyl acetal, ethyl acetate and acetic acid.

[0053] In the separation section, gas / liquid separation means known to those skilled in the art are used, preferably gas / liquid separators operated at a pressure of 0.1 MPa to 0.3 MPa and at a temperature of 25°C to 60°C.

[0054] (Step b2) Step of converting the ethanol / acetaldehyde mixture into butadiene) According to one embodiment of the invention, step b2) of the conversion to butadiene comprises at least a reaction section to which is fed at least a portion of the ethanol / acetaldehyde effluent resulting from step b1), a liquid ethanol-rich effluent resulting from step b3), an acetaldehyde-rich fraction of the effluent resulting from step b5), and possibly advantageously an ethanol-rich stream resulting from step b5), and a separation section making it possible to separate the effluent of the reaction section into at least a gaseous effluent and a liquid effluent. The reaction section can also be fed with an external stream of acetaldehyde.

[0055] The flow rates of the various feeds to the reaction section of step b2) are adjusted so that the ethanol / acetaldehyde molar ratio at the inlet of the reaction section is between 1 and 5, preferably between 1 and 3.5, even more preferably between 2 and 3, and highly preferably between 2.4 and 2.7.

[0056] The reaction section makes it possible to convert at least a portion of the ethanol / acetaldehyde mixture into butadiene. The conversion selectivity of the ethanol / acetaldehyde mixture is preferably greater than 60%, preferably greater than 70%, and highly preferably greater than 80%. Selectivity refers to the molar ratio of the flow rate of butadiene in the effluent from the reaction section to the flow rates of ethanol and acetaldehyde consumed in the reaction section. The conversion rate of the ethanol / acetaldehyde mixture is preferably greater than 30%, preferably greater than 40%, and preferably greater than 47%. Conversion rate refers to the molar ratio of the flow rates of ethanol and acetaldehyde in the effluent from the reaction section to the flow rates of ethanol and acetaldehyde in the feed of the reaction section. It is operated in the presence of a catalyst, advantageously a silica-supported catalyst selected from the group consisting of catalysts containing tantalum oxide, zirconium oxide or niobium oxide, preferentially containing 2% tantalum oxide (see, for example, Corson, Jones, Welling, Hincbley, Stahly, Ind. Eng. Chem. 1950, 42, 2, 359-373). The second reaction zone is operated at a temperature of 300°C to 400°C, preferably 320°C to 370°C, and at a pressure of 0.1 MPa to 1.0 MPa, preferably 0.1 MPa to 0.5 MPa, preferably 0.1 MPa to 0.3 MPa.

[0057] Preferably, about 65-80% of the acetaldehyde is converted in the reaction section. The effluent from the reaction section therefore still contains ethanol. Along with butadiene, a number of impurities may be produced, including ethylene, propylene, diethyl ether (DEE), ethyl acetate, butanol, hexanol, butene, pentene, pentadiene, hexene, and hexadiene.

[0058] The reaction section is fed with the acetaldehyde effluent resulting from step b5) of treating the effluent, and the ethanol to acetaldehyde ratio at the inlet to this section is regulated by monitoring the fraction of the ethanol effluent resulting from step b5) that is fed to step b1) and thus produces acetaldehyde. In fact, the remaining fraction of the ethanol-rich effluent resulting from step b5) is fed to step b3) of treating hydrogen, and after scrubbing the hydrogen effluent, forms the liquid ethanol-rich effluent resulting from step b3), which is fed to step b2). This ethanol-rich liquid effluent resulting from step b3) contains only a small amount of acetaldehyde.

[0059] The separation section uses gas / liquid separation means known to those skilled in the art, preferably a gas / liquid separator operated at a pressure of 0.1 MPa to 0.3 MPa and a temperature of 25°C to 60°C.

[0060] (Step b3) Hydrogen processing step) According to one embodiment, step b3) of treating hydrogen comprises at least a compression section and a gas / liquid scrubbing section, the compression section being fed with the hydrogen effluent from step b1), and the gas / liquid scrubbing section being fed with a portion of the ethanol effluent from step b5) and a portion of the ethanol / acetaldehyde effluent from step b1), to produce at least a liquid ethanol-rich effluent and a purified hydrogen effluent. Preferably, step b3) is not fed with any other streams.

[0061] The proportion of the portion of the ethanol / acetaldehyde effluent resulting from step b1) is between 0 and 100%. The use of the portion of the ethanol / acetaldehyde effluent makes it possible to reduce the flow rate of the portion of the ethanol-rich effluent resulting from step b5).

[0062] Step b3) makes it possible to obtain a purified hydrogen effluent of high purity, i.e. containing at least 90 mol% hydrogen, preferably at least 99 mol% hydrogen, preferably at least 99.8 mol% hydrogen. The purified hydrogen effluent also contains traces of water and ethanol. This step also makes it possible to recover the ethanol and acetaldehyde contained in the hydrogen effluent resulting from said step b1), thereby recycling them and maximizing the overall yield of the process.

[0063] The use of the fraction of the ethanol-rich effluent resulting from step b5) and the fraction of the ethanol / acetaldehyde effluent resulting from step b1) instead of water (as in the prior art practice) makes it possible to reduce the total flow rate of water circulating through the process. Therefore, the total flow rate of water fed to steps b5) and b5') for treating the effluent is reduced, thereby reducing the size of the equipment and the utility consumption in steps b5) and b5'). Furthermore, as mentioned above, the ethanol-rich effluent resulting from step b3) can be fed directly to step b2) for conversion to butadiene without having to be treated by step b5) for treating the effluent.

[0064] The hydrogen effluent resulting from step b1) is compressed in a compression section to a pressure of 0.1 MPa to 1.0 MPa, advantageously 0.1 MPa to 0.7 MPa, preferably 0.4 MPa to 0.68 MPa, the effect of which is firstly to reduce the gas volume flow rate and secondly to improve the effectiveness of downstream scrubbing.

[0065] The compressed hydrogen effluent is then cooled to a temperature of 25°C to 60°C, preferentially 30°C to 40°C, and then fed to the bottom of a scrub wash column in the scrub wash section, where it is contacted with a fraction of the ethanol effluent resulting from step b5) and a fraction of the ethanol / acetaldehyde effluent resulting from step b1), which are fed to the top and middle points of the scrub wash column, respectively. These two fractions are cooled to a temperature of 15°C to -30°C, preferentially 0°C to -15°C, before being fed to the scrub wash column. Advantageously, the ethanol-rich effluent resulting from step b5) is fed at a lower temperature than the fraction of the ethanol / acetaldehyde effluent resulting from step b1), thereby creating a temperature gradient between the top and bottom and limiting solvent losses in the purified hydrogen effluent. The gas / liquid scrub wash column in the scrub wash section is equipped with trays or random or structured packing.

[0066] (Optional step b3') Final treatment of the hydrogen effluent A step b3') of final treatment of the hydrogen is advantageously carried out at the end of step b3), comprising at least one gas / liquid scrubbing section, which is fed with the purified hydrogen effluent from b3) and a pure water effluent from outside the process or a water-rich effluent from step b5), and which produces a purified hydrogen effluent and a wastewater effluent.

[0067] The scrubbing section comprises at least one gas / liquid scrubbing section, which is fed at the bottom with the purified hydrogen effluent from step b3) and at the top with the pure water effluent or the water-rich effluent from step b5), producing a purified hydrogen effluent at the top and a wastewater effluent at the bottom.

[0068] This step makes it possible to recover final traces of ethanol that may be contained in the purified hydrogen effluent resulting from b3). Step b3') is similar to prior art hydroprocessing, but nevertheless uses a much lower water flow rate than that used in prior art, since the hydrogen effluent fed to step b3') has been previously treated by step b3) and therefore all acetaldehyde entrained in the hydrogen effluent resulting from step b1) has been removed. All other things being equal, the removal of traces of ethanol by washing with water requires a lower flow rate than the removal of traces of acetaldehyde. Furthermore, ethanol is less volatile than acetaldehyde and is therefore entrained to a much lesser extent than acetaldehyde under the same operating conditions.

[0069] (Step b4) Step of extracting butadiene) According to one embodiment of the invention, step b4) of extracting butadiene comprises at least a compression section, a gas / liquid scrubbing section and a distillation section, and is fed with at least an ethanol stream consisting of the gaseous and liquid effluents resulting from step b2), the ethanol feedstock of the process and / or a portion of the ethanol effluent resulting from step b5), producing at least one gaseous by-product effluent, a crude butadiene effluent and an ethanol / acetaldehyde / water effluent.

[0070] The ethanol stream fed to step b4) preferably comprises at least 80% by weight, preferably at least 90% by weight, preferably at least 93% by weight of ethanol. The ethanol stream fed to step b4) may contain methanol, water, ethyl acetate, butanol and hexanol. Preferably, the ethanol stream fed to step b4) preferably comprises less than 10% by weight, preferably less than 5% by weight, preferably less than 1% by weight of acetaldehyde. Preferably, the ethanol stream fed to step b4) preferably comprises less than 20% by weight, preferably less than 5% by weight, preferably less than 1% by weight of water.

[0071] In a preferred configuration, the ethanol stream fed to step b4) consists of the ethanol feedstock of the present process. One advantage of this configuration is that the feedstock is free of reaction by-products formed in steps b1) and b2) and can be concentrated by recycling. In particular, the ethanol feedstock contains no or only trace amounts of acetaldehyde.

[0072] In another preferred configuration, the ethanol stream consists of a fraction of the ethanol effluent resulting from step b5) of treating the effluent.

[0073] The use of an ethanol stream containing little or no acetaldehyde minimizes the entrainment of acetaldehyde in the gaseous by-product effluent removed at the top of the gas / liquid scrubbing section, reducing the overall yield loss of the process and the wash water flow rate required in step b6).

[0074] The gaseous effluent resulting from step b2) is compressed in a compression section to a pressure of 0.1 MPa to 1.0 MPa, preferentially 0.1 MPa to 0.7 MPa, preferably 0.2 MPa to 0.5 MPa. The effect of this compression is firstly to reduce the gas volume flow rate and secondly to improve the effectiveness of downstream scrubbing. Preferably, the compressed gaseous effluent is then cooled to a temperature of 25°C to 60°C, preferably 30°C to 40°C.

[0075] Preferably, the gas / liquid scrubbing section of step b4) comprises a scrubbing column, which receives at its top the ethanol stream fed to step b4) and at its bottom a cooled compressed gaseous effluent, producing at its top a gaseous by-product effluent and at its bottom a liquid effluent, which is fed to the distillation section of step b4).

[0076] The ethanol stream fed to step b4) is cooled to a temperature of 20°C to -20°C, preferably 15°C to 5°C, before being fed to the top of the gas / liquid scrubbing column of the scrubbing section. The advantage of cooling the ethanol stream is improved performance of the scrubbing operation by minimizing entrainment of ethanol and acetaldehyde in the gaseous by-product stream. Thus, any butadiene present in the compressed and cooled gaseous effluent resulting from step b2) is removed, and the vapor by-product effluent withdrawn at the top of the gas / liquid scrubbing section is devoid of butadiene.

[0077] It should be noted that minimizing the entrainment of acetaldehyde in the gaseous by-product effluent allows for a significant reduction in the water flow rate required in step b6) of washing the gaseous by-product with water, the purpose of which is to recover the ethanol and traces of acetaldehyde entrained in the gaseous by-product effluent withdrawn at the top of the ethanol scrubbing section of step b4).

[0078] Preferably, the butadiene-rich ethanol stream withdrawn at the bottom of the gas / liquid scrubbing section of step b4) and the liquid effluent of step b2) are fed to the distillation section of step b4) to separate a vapor effluent (called crude butadiene effluent) containing the majority of butadiene at the top and an ethanol / acetaldehyde / water residue at the bottom. The term "majority" means more than 80%, preferentially more than 90%, preferably more than 95%, even more preferably more than 98%, highly preferably more than 99%, and highly advantageously all of the butadiene contained in the feed to the distillation section. This ethanol / acetaldehyde / water residue comprises ethanol and acetaldehyde, as well as the water produced in step b2), and by-products formed in steps b1) and b2), such as diethyl ether, ethyl acetate, and brown oil. The ethanol / acetaldehyde / water residue is then fed to step b5'), where the effluent is treated. The distillation section is operated at a pressure of 0.1 MPa to 1 MPa, preferably 0.2 MPa to 0.5 MPa.

[0079] (Step b4') First purification of butadiene) Step b4') of the initial purification of butadiene comprises at least a gas / liquid scrubbing section, which is fed at the bottom with the crude butadiene effluent from b4) and at the top with a water stream, which may be a water stream originating from outside the process for producing butadiene and / or a fraction of the water effluent from step b5), said scrubbing section producing a pre-purified butadiene effluent at the top and a wastewater effluent at the bottom. Preferably, the water stream is a water stream originating from outside the process.

[0080] The wastewater effluent contains acetaldehyde and small amounts of butadiene and can be sent to step b5), an acetaldehyde distillation section, or step b5'), which treats the effluent.

[0081] The purpose of step b4') is to remove polar impurities, especially acetaldehyde, which should not be present in the final butadiene at more than a few ppm. The crude butadiene effluent resulting from b4) contains most of the butadiene but still contains many impurities, including large amounts of acetaldehyde, which form azeotropes with butadiene and therefore cannot be completely removed by distillation in step b4). The flow rate of the water stream is therefore adjusted to obtain the desired specification of acetaldehyde in the pre-purified butadiene effluent.

[0082] The water stream is cooled to a temperature below 25°C, preferably below 20°C, before being fed to the gas / liquid scrubbing section so as to perform washing with a small amount of water. The feed temperature of the water stream is selected so as not to form hydrates with the butadiene and light hydrocarbons still present in the butadiene stream resulting from step b4). The pressure in the scrubbing column is determined so as to ensure that there is no condensation of butadiene and that it remains in gaseous form. The pressure in this step is between 0.1 MPa and 1 MPa, even more preferably between 0.2 MPa and 0.3 MPa.

[0083] (Step b4'') Subsequent step of purifying butadiene) According to one embodiment of the invention, the subsequent step b4″) of purifying butadiene is fed with at least the pre-purified butadiene effluent resulting from step b4′) and produces at least a purified butadiene effluent.

[0084] This step b4″) makes it possible to purify the butadiene produced in the reaction step to very high purity levels (more than 99.5% by weight, preferentially more than 99.8% by weight, very preferentially more than 99.9% by weight), while limiting product losses by separating out the impurities that were not or only partially removed during steps b4), b4′).

[0085] In a first embodiment of the invention, step b4″) comprises at least one drying section, a cryogenic distillation section and a section for separating butadiene / butenes by liquid-liquid extraction.

[0086] The pre-purified butadiene effluent resulting from step b4') is fed to a drying section. The purpose of this section is to achieve the required specification of water in the final product (purified butadiene effluent) and to make it possible to carry out the cryogenic separation without the risk of hydrate formation. A dry butadiene effluent is obtained at the outlet of the drying section. Dry butadiene means that the water content is less than 10 ppm, preferably less than 5 ppm, preferably less than 1 ppm.

[0087] The drying section preferentially comprises one or more volumes containing one or more adsorbents having a strong affinity for water. The adsorbents may be, but are not limited to, silica and / or alumina. The adsorbents may be, but are not limited to, zeolites such as zeolite 3A or 4A. Once the adsorbents are saturated with water, the pre-purified butadiene effluent is fed to another volume containing fresh or regenerated adsorbent.

[0088] The adsorbent can be regenerated by changing the partial pressure of water in the volume, by changing the temperature in the volume, or by changing the partial pressure and temperature of water in the volume. In the latter embodiment, one or more water-saturated adsorbents are regenerated by heating the volume while feeding a water-free or almost water-free stream. "Water-free or almost water-free" means less than 500 ppm, preferentially less than 350 ppm, preferably less than 10 ppm, preferably less than 5 ppm, and highly preferably less than 1 ppm. This water-free or almost water-free stream can be, but is not limited to, a nitrogen stream, an air stream, a hydrocarbon stream, or a hydrogen stream. In a preferred embodiment of the present invention, a fraction of the purified hydrogen effluent resulting from step b3) is used.

[0089] The water-free or nearly water-free stream is heated to a temperature sufficient to regenerate the adsorbent, preferentially to about 250°C, before being fed to the volume containing the adsorbent to be regenerated.

[0090] According to this first embodiment, the dried butadiene effluent is then fed to a cryogenic distillation section using a distillation column. The light products leave the top of the cryogenic distillation column at -25°C to -35°C. The column bottoms are at a temperature of 20°C to 50°C, preferably 25°C to 45°C, and highly preferably 30°C to 40°C, and the pressure at the top is 0.3 MPa to 0.4 MPa, preferably 0.35 MPa. The advantage of this column is that it is very effective in separating the last non-condensables without losing butadiene (less than 0.05%). This avoids significant recycle to step b4) and butadiene loss.

[0091] Further according to this first embodiment, the bottom product of the cryogenic distillation section, called the top butadiene effluent, contains butenes as the main impurity, and is fed to a section for butadiene / butene separation by liquid-liquid extraction, as described in patent FR 2,036,057.

[0092] The section for butadiene / butene separation is a liquid-liquid extraction section, in which the top butadiene effluent is fed to the middle zone of a first liquid-liquid extraction column, and a polar solvent, preferentially DMSO, is fed to the top. A saturated hydrocarbon solvent, preferentially pentane or cyclohexane, is fed to the bottom. The flow rates and the flow ratio of the polar solvent to the hydrocarbon solvent are also adjusted so that most of the butene is entrained by the hydrocarbon solvent and most of the butadiene is entrained by the polar solvent.

[0093] The butene / hydrocarbon mixture obtained at the top of the first extraction column is then treated in a first distillation column to obtain a butene effluent at the top and a hydrocarbon solvent (which can be recycled) at the bottom.

[0094] The butadiene / polar solvent mixture is then fed to the top of a second liquid-liquid extraction column, where the butadiene is extracted from the polar solvent by direct contact with a larger amount of hydrocarbon solvent than in the first liquid-liquid extraction column, and introduced into the bottom of the second liquid-liquid extraction column.

[0095] The butadiene / hydrocarbon mixture obtained at the top of the second liquid-liquid extraction column is then processed in a distillation column to obtain a purified butadiene effluent at the top and a recyclable hydrocarbon solvent at the bottom.

[0096] Preferably, the liquid-liquid extraction column in the section for butadiene / butene separation is operated at a pressure of 0.1 MPa to 1 MPa and a temperature of 20°C to 60°C.

[0097] In another embodiment of the present invention, step b4'') comprises at least distillation and extractive distillation. The distillation step can be carried out upstream or downstream of the extractive distillation step. The extractive distillation can be carried out using solvents such as, but not limited to, N-methylpyrrolidone, dimethylformamide or acetonitrile.

[0098] (Step b5) Step of treating effluent) According to one embodiment of the present invention, the water / ethanol / acetaldehyde rafinate resulting from step b5') is fed to step b5) for treating the effluent, producing at least an ethanol-rich effluent, an acetaldehyde-rich effluent, and a water-rich effluent. If the wastewater effluent resulting from step b4') or the alcoholic water effluent resulting from step b6) or the wastewater effluent resulting from step b3') has not been subjected to step b5') for removing impurities and brown oil, it can be fed directly to step b5) for treating the effluent. Advantageously, a fraction of the ethanol feedstock is also fed to section b5).

[0099] Preferably, unlike the prior art, removal occurs without loss of ethanol or acetaldehyde.

[0100] Preferably, step b5) comprises at least two distillation sections, namely one "water and ethanol" distillation section and one "acetaldehyde" distillation section.

[0101] The water / ethanol / acetaldehyde effluent resulting from step b5') and optionally the wastewater effluent resulting from step b4') are fed to an acetaldehyde distillation section, where the acetaldehyde is separated to form an acetaldehyde-rich effluent, and the residue from the acetaldehyde distillation section is fed to a water and ethanol distillation section, allowing for the separation of an overhead ethanol-rich effluent and a bottom water-rich effluent.Since the alcoholic water effluent resulting from step b6) and the wastewater effluent resulting from step b3') do not contain acetaldehyde, they can be fed directly to the water and ethanol distillation section.

[0102] The ethanol-rich effluent resulting from step b5) consists mainly of ethanol. "Mainly" means more than 80% by weight, preferably more than 84% by weight. Without limitation, the ethanol-rich effluent resulting from step b5) may contain impurities such as water, ethyl acetate, butanol and hexanol.

[0103] Impurities other than water make up less than 10%, preferably less than 5%, more preferentially less than 2% by weight of the stream.

[0104] The acetaldehyde-rich effluent resulting from step b5) consists mainly of acetaldehyde and ethanol. "Mainly" means more than 80% by weight, preferably more than 85% by weight. Without limitation, the acetaldehyde-rich effluent resulting from step b5) may contain impurities such as water, ethyl acetate, or acetone.

[0105] Impurities other than water make up less than 10% by weight of the stream, preferentially less than 5%.

[0106] The acetaldehyde-rich, ethanol-rich and water-rich effluents are then recycled to the remainder of the process according to the invention. The fraction of said ethanol-rich effluent fed to step b1) is preferably at least 0.7, preferably at least 0.75, more preferably at least 0.8. The fraction of the water-rich effluent fed to step b6) is advantageously between 0 and 0.3, very advantageously between 0 and 0.1 and more advantageously between 0 and 0.01. The fraction of the water-rich effluent fed to step b5') for removal of impurities and brown oil is advantageously between 0 and 1, preferentially between 0.3 and 0.6 and advantageously between 0.4 and 0.5.

[0107] In another embodiment of the present invention, the acetaldehyde-rich, ethanol-rich, and water-rich effluents undergo a purification step before being recycled to the remainder of the process. "Purification" means that the effluents are contacted with an adsorbent, such as activated carbon, silica, alumina, or a functionalized polymer resin. For example, activated carbon makes it possible to remove traces of butanol and hexanol contained in the ethanol-rich stream. For example, a basic resin makes it possible to remove acetic acid present in the water-rich effluent. If the adsorbent is saturated and the purity of the acetaldehyde-rich, ethanol-rich, and water-rich effluents cannot be guaranteed, they are removed or regenerated for reuse.

[0108] (Step b5') Step of removing liquid impurities and brown oil) According to one embodiment of the present invention, step b5') of removing impurities and brown oil is fed with at least a fraction of the ethanol / acetaldehyde / water effluent resulting from step b4) and the water effluent resulting from step b5), resulting in an ethanol / acetaldehyde / water raffinate, a light brown oil effluent and a heavy brown oil effluent.

[0109] Preferably, step b5') comprises at least a washing / backwashing section, a light brown oil distillation section and a heavy brown oil distillation section.

[0110] At an intermediate point, the preferential washing / backwashing section is fed with the ethanol / acetaldehyde / water effluent resulting from step b4), which is advantageously mixed with the wastewater effluent resulting from step b4'), the alcoholic-water effluent resulting from step b6) and the wastewater effluent resulting from step b3'), preferably with a fraction of the wastewater effluent resulting from step b4') if the latter step is implemented. Since these effluents are richer in water than the ethanol / acetaldehyde / water effluent resulting from step b4), introducing them as a mixture makes it possible to limit hydrocarbon losses in the raffinate.

[0111] The preferential washing / backwashing section receives the hydrocarbon effluent at the bottom and the fraction of the water effluent resulting from step b5) that does not contain ethanol or acetaldehyde at the top. The hydrocarbon effluent and the fraction of the water effluent resulting from step b5) are preferably fed at a temperature of 10 to 70° C., preferentially 45 to 55° C. The washing / backwashing section produces a washed hydrocarbon extract at the top, which is loaded with the impurity fraction and the brown oil fraction, and an ethanol / acetaldehyde / water raffinate at the bottom.

[0112] The washing / backwashing section is preferably operated at a pressure of 0.1 MPa to 0.5 MPa, preferentially 0.2 MPa to 0.4 MPa. Preferably, the addition of water to perform the backwashing is such that the water content in the water / ethanol / acetaldehyde rafinate is more than 30% by weight, preferably more than 40% by weight.

[0113] In one embodiment, the contact between the two liquid phases in the wash / backwash section is carried out in a liquid-liquid extractor. Various contact configurations are possible, including, but not limited to, a packed column, a pulse column, or an agitated distribution column. In another embodiment, the contact between the two liquid phases in the wash / backwash section is carried out in a membrane contactor or a cascade of membrane contactors. This contact method is particularly well suited to the system used. In particular, water-ethanol-hydrocarbon mixtures are known to form stable emulsions, which may be problematic in liquid-liquid extractors. The membrane contactor allows for a substantial contact area to be created, facilitating the transfer of impurities and oil to the hydrocarbon phase without forming emulsions.

[0114] The washed hydrocarbon extract is fed to a light brown oil distillation section to produce a light brown oil effluent as a distillate and a hydrocarbon residue containing a heavy fraction of the brown oil.

[0115] The light brown oil effluent is composed of impurities produced by reaction step b2), primarily diethyl ether, ethyl acetate and crotonaldehyde, and also of lighter fractions of brown oil, composed of lesser amounts of impurities including pentenes, isoprene, butanal and vinyl ethyl ether. This effluent may be combusted to provide part of the heat required for the hot oil circuit or steam boiler of the process, or may be distilled to recover diethyl ether and / or ethyl acetate / crotonaldehyde effluents, which may be upgraded or recycled to the reaction section of step b2) where they are reconverted.

[0116] The hydrocarbon residue essentially contains hydrocarbons useful for washing, but also contains the heaviest fraction of brown oil. To avoid the accumulation of brown oil due to the recycling of the hydrocarbon effluent to the liquid-liquid extractor, a fraction of the hydrocarbon residue is processed in a heavy oil distillation section consisting of a distillation column to produce a hydrocarbon distillate essentially composed of hydrocarbons with only traces of brown oil remaining, resulting in a heavy brown oil effluent containing more than 80%, preferentially more than 85%, of hydrocarbons and the heaviest brown oil as the residue. The fraction of the hydrocarbon effluent sent to the oil distillation section is 5-30%, preferentially 10-20% of the total flow rate of the hydrocarbon residue. The hydrocarbon distillate is mixed with the fraction of the hydrocarbon residue not processed in the heavy oil distillation section to form the hydrocarbon effluent sent to the washing / backwashing section.

[0117] This effluent preferably accounts for 0.1-20%, preferably 0.3-5%, of the feedstock for the heavy oil distillation section and may be combusted to provide part of the heat required for the hot oil circuit or steam boiler of the process. To maintain a constant wash flow rate, a hydrocarbon feed equivalent to the losses at the bottom of the heavy oil distillation section is required. This column is adjusted to maintain a constant brown oil concentration in the hydrocarbon recycle loop (hydrocarbon effluent / wash hydrocarbon effluent loop).

[0118] Light and heavy brown oil effluents are removed from the process.

[0119] The ethanol / acetaldehyde / water effluent resulting from step b4) contains primarily ethanol, acetaldehyde, and water, but also contains impurities such as diethyl ether, ethyl acetate, and brown oil, as defined above. These impurities may accumulate in the acetaldehyde-rich distillate fraction and / or the ethanol-rich distillate fraction if they are returned to the reaction steps b1) and b2) and if they are only partially converted in the reaction sections of steps b1) and b2). Step b5') makes it possible to recover some of these impurities before step b5), which treats the effluent, thereby preventing demixing of the brown oil in the distillation column, simplifying the distillation scheme, and making it possible to obtain ethanol, acetaldehyde, and water effluents at the end of step b5) with higher purity than in the prior art.

[0120] Washing the ethanol / acetaldehyde / water effluent resulting from step b4) with a hydrocarbon effluent will entrain certain impurities, whereas back-washing the hydrocarbon stream will entrain the impurities and part of the brown oil together with a fraction of the water effluent resulting from step b5), limiting any loss of acetaldehyde and ethanol.

[0121] The applicant has surprisingly found that adding certain hydrocarbons to the ethanol / acetaldehyde residue resulting from step b4) can result in liquid-liquid phase separation. This result is surprising because the ethanol / acetaldehyde residue resulting from the process is highly enriched in ethanol and acetaldehyde, which are miscible with the hydrocarbons in any proportion. The applicant has found that by appropriately selecting the hydrocarbons, liquid-liquid phase separation can be obtained, and thus liquid-liquid extraction can be performed to remove some of the impurities contained in the ethanol / acetaldehyde / water effluent resulting from step b4). The hydrocarbon effluent may contain saturated and / or unsaturated and / or aromatic hydrocarbons, preferably saturated hydrocarbons. The hydrocarbon effluent advantageously consists of a mixture of hydrocarbons having 6 to 40 carbon atoms, preferably 10 to 20 carbon atoms. The hydrocarbon effluent may be, but is not limited to, a desulfurized gas oil or kerosene fraction, or a hydrocarbon fraction produced by a Fischer-Tropsch-type unit.

[0122] The addition of water to the washing / backwashing section allows for better functioning of the method for removing impurities and brown oil according to the present invention.

[0123] (Step b6) Washing the gaseous by-products with water) According to one embodiment of the invention, the water washing step b6) is fed with the gaseous by-product effluent resulting from step b4) and a fraction of the water-rich effluent resulting from step b5), resulting in at least one alcoholic water effluent.

[0124] The purpose of step b6) is to recover the small ethanol fraction entrained in the gaseous by-product effluent resulting from step b4) in order to improve the overall yield of the process.

[0125] The amount of water resulting from step b5) required in step b6) according to the present invention is very small compared to that required in the prior art, because the vapor effluent resulting from step b2) was scrubbed in step b4) with an ethanol stream containing little or no acetaldehyde, so that only a small amount of ethanol remains in this stream, which can be easily recovered with a small amount of water compared to the amount that would be required if traces of acetaldehyde were present in the gaseous by-product effluent resulting from step b4).

[0126] The water loaded with ethanol after washing is removed from step b6) and constitutes the alcoholic water effluent, which is preferably fed directly to the water-ethanol distillation section of step b5) without the burden of the acetaldehyde distillation section. In another embodiment of the invention, it is preferably fed to step b5') for removing impurities and brown oil.

[0127] Step b) of the process according to the invention makes it possible to minimize the flow rate of the effluent treated in the step of treating the effluent and to reduce butadiene losses as much as possible, and to recover more than 98%, preferably more than 99%, of the butadiene formed at the end of the reaction step in the purified butadiene effluent.

[0128] (Third reaction section (step c of the process according to the invention)) The third reaction section (7) comprises at least one reactor into which 1,3-butadiene (6) from the second reaction section (5), CO2 (4) from the first reaction section (2), and hydrogen (9) from reaction section 5 are introduced.

[0129] According to a preferred embodiment, step c) of the method according to the invention comprises the following substeps: c1) The process of C-C coupling between two molecules of CO2 and one molecule of 1,3-butadiene; c2) separating out the hexenedioic acid; c3) reducing the hexenedioic acid formed in step c1) to obtain adipic acid.

[0130] (Step c1)) Advantageously, step c1) is carried out in at least one reactor in which the reactants are 1,3-butadiene from the second reaction section and CO2 from the first reaction section, contacted in a solvent with a metal precursor, a ligand and a reducing agent.

[0131] The metal precursor is preferably a nickel(II) salt. More preferentially, the nickel salt is selected from tetrabutylammonium tetrabromonickelate (NiBr4(DBA)2), NiCl2(DME), NiBr2(DME).

[0132] The ligands are preferably bidentate dinitrogen (N,N) ligands such as bipyridine or phenanthroline derivatives. More preferentially, the ligands are selected from the ligands 2-methyl-4,7-diphenyl-1,10-phenanthroline, 4,7-diphenyl-1,10-phenanthroline and 6-methyl-2,2'-bipyridine.

[0133] The reducing agent is preferably a metal selected from zinc or manganese. The reducing agent is preferably manganese. It is also possible to carry out the reduction step using a metal-photochemical or metal-electrochemical couple.

[0134] The solvent is preferably a polar aprotic solvent. The solvent advantageously has a dielectric constant of greater than 25.0 and / or a dipole moment of greater than 2.5D at 20°C. The solvent is preferably selected from N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), acetonitrile, dimethyl sulfoxide (DMSO), HMPT, hexamethylphosphoramide (HMPA), nitrobenzene, formamide, nitromethane and propylene carbonate. Even more preferably, the solvent is N,N-dimethylacetamide (DMA).

[0135] Step c1) is advantageously carried out at a temperature between 5°C and 70°C, preferably between 40°C and 70°C.

[0136] Before the separation step c2), the reaction medium is preferably neutralized slowly with an acid such as HCl and water.

[0137] (Step c2)) During the separation step c2), the hexenedioic acid is advantageously extracted from the aqueous medium with ethyl acetate by liquid-liquid extraction. Preferably, the ethyl acetate effluent enriched in hexenedioic acid is dried and then distilled. One of the effluents is mainly ethyl acetate, which can be recycled. Another effluent, enriched in hexenedioic acid, can be further purified, for example by crystallization, and then diluted with a solvent such as methanol to feed the final step.

[0138] (Step c3)) Step c3) consists of reducing hexenedioic acid to give adipic acid. Step c3) can be carried out in at least one reactor into which hexenedioic acid diluted in methanol is introduced in the presence of a catalyst and a reducing agent.

[0139] The catalyst used in step c3) is preferably a metal precursor or a metal alloy on a support, such as palladium on activated carbon or Raney nickel. More preferentially, the catalyst is based on palladium supported on activated carbon.

[0140] Preferentially, purified hydrogen originating from step b3) of the second reaction section can be used as reducing agent in step c3). Reduction step c3) is preferably carried out at a temperature between 10°C and 50°C, more preferentially between 15°C and 25°C.

[0141] (Example) (1 / Example of synthesizing adipic acid from glucose without upgrading CO2 in the fermentation process) The glucose fermentation reaction equation is CH 12 O6 → 2C2H5OH + 2CO2 As a result, 66.7% of the carbon in the glucose molecule is converted to ethanol, and 33.3% is converted to CO2.

[0142] If the feedstock is 170 Kta glucose, the fermentation theoretically allows the production of 86.8 Kta ethanol and 83 Kta CO2.

[0143] Assuming a 40% weight yield for the conversion of ethanol to butadiene, 34.7 Kta of butadiene can be produced, i.e., up to 93.9 Kta of adipic acid. If CO2 is not upgraded to adipic acid, up to 45.4% of the carbon from glucose can be upgraded to adipic acid (see Table 1).

[0144] (2 / Example of synthesizing adipic acid from glucose by upgrading CO2 in the fermentation process) The equation for glucose fermentation is CH 12 O6 → 2C2H5OH + 2CO2 As a result, 66.7% of the carbon in the glucose molecule is converted to ethanol, and 33.3% is converted to CO2.

[0145] If the feedstock is 170 Kta glucose, the fermentation theoretically allows the production of 86.8 Kta ethanol and 83 Kta CO2.

[0146] Assuming a 40% weight yield for the conversion of ethanol to butadiene, 34.7 kcal of butadiene can be produced, i.e., a maximum of 93.9 kcal of adipic acid. To produce 93.9 kcal of adipic acid, 56.6 kcal of CO2 is required. Therefore, fermentation produces enough CO2 to be self-sufficient in the CO2 stream. If the CO2 is upgraded to adipic acid, up to 68.1% of the carbon from glucose can be upgraded to adipic acid (see Table 1).

[0147] [Table 1]

[0148] [Brief explanation of the drawings]

[0149] [Figure 1] 1 shows a schematic diagram of a method and plant according to the invention, making it possible to produce adipic acid from biomass, preferably lignocellulosic biomass.

Claims

1. 1. A method for converting biomass to adipic acid, comprising the steps of: a) Processing biomass to produce ethanol and CO ２ generating b) converting the ethanol obtained at the end of step a) to obtain 1,3-butadiene and diatomic hydrogen; c) Reacting adipic acid with 1,3-butadiene and diatomic hydrogen obtained at the end of step b) and CO obtained at the end of step a). ２ The process of synthesizing from

2. 10. The method of claim 1, wherein step a) comprises the following substeps: a1) pretreating biomass to obtain a pretreated substrate; a2) enzymatically or chemically hydrolyzing the pretreated substrate obtained at the end of step a1) to obtain an enzymatically or chemically hydrolyzed must; a3) The must of the enzymatic or chemical hydrolysis obtained at the end of step a2) is subjected to alcoholic fermentation to produce ethanol and CO ２ The process of obtaining the above.

3. 3. The process according to claim 2, wherein sub-step a1) is carried out by steam explosion under acid conditions at a temperature between 150° C. and 250° C. for a period of between 5 and 30 minutes.

4. 4. The method according to claim 2 or 3, wherein substep a2) is carried out by enzymatic hydrolysis in the presence of Trichoderma reesei cellulase.

5. The method according to any one of claims 1 to 4, wherein step b) comprises the following substeps: b1) a process for converting ethanol into acetaldehyde, comprising at least a reaction section and a separation section, to which at least a portion of the ethanol-rich effluent resulting from step b5) is fed and which operates in the presence of a catalyst at a pressure of 0.1 MPa to 1.0 MPa and at a temperature of 200°C to 500°C; the separation section makes it possible to separate the effluent of the reaction section into at least a gaseous hydrogen effluent and a liquid ethanol / acetaldehyde effluent; b2) a process for converting ethanol to butadiene, comprising at least a reaction section and a separation section, to which at least a portion of the ethanol / acetaldehyde effluent resulting from step b1), a liquid ethanol-rich effluent resulting from step b3) and a portion of the acetaldehyde-rich effluent resulting from step b5) are fed and which is operated in the presence of a catalyst at a temperature of 300°C to 400°C and a pressure of 0.1 MPa to 1.0 MPa, the feed flow rate being adjusted so that the ethanol / acetaldehyde molar ratio at the inlet of the reaction section is 1 to 5; the separation section makes it possible to separate the effluent of the reaction section into at least a gaseous effluent and a liquid effluent; b3) processing hydrogen; comprising at least a compression section and a gas / liquid scrubbing section; the compression section compresses the hydrogen effluent from step b1) to a pressure of 0.1 MPa to 1.0 MPa; feeding a portion of the ethanol-rich effluent from step b5) and a portion of the ethanol / acetaldehyde effluent from step b1) at a temperature of 15°C to -30°C to the gas / liquid scrubbing section, and feeding the compressed hydrogen effluent at a temperature of 25°C to 60°C; producing at least a liquid ethanol-rich effluent and a purified hydrogen effluent; b4) a step of extracting butadiene, comprising at least a compression section, a gas / liquid scrubbing section, and a distillation section; the compression section compresses the gaseous effluent resulting from step b2) to a pressure of 0.1 MPa to 1.0 MPa; the gas / liquid scrubbing section comprises a scrubbing column, to which an ethanol stream consisting of the ethanol feedstock from the process and / or a portion of the ethanol effluent resulting from step b5) at a temperature of 20°C to -20°C is fed at the top and the gaseous effluent resulting from step b2) is cooled at the bottom; the distillation section is operated at a pressure of 0.1 MPa to 1 MPa and is fed with at least the liquid effluent resulting from step b2) and the liquid effluent from the gas / liquid scrubbing section; step b4) produces at least one gaseous by-product effluent, a crude butadiene effluent, and an ethanol / acetaldehyde / water effluent; b4') a step for the first purification of butadiene, comprising at least a gas / liquid scrubbing section, into which the crude butadiene effluent from b4) is fed at the bottom and a water stream at the top, which may be a water stream originating outside the process for producing butadiene and / or part of the water effluent from step b5), said scrubbing section producing a pre-purified butadiene effluent at the top and a wastewater effluent at the bottom; b4'') a subsequent step of purifying butadiene; feeding at least the pre-purified butadiene effluent resulting from step b4') to produce at least a purified butadiene effluent; b5) treating the effluent; feeding at least the water / ethanol / acetaldehyde raffinate resulting from step b5') to produce at least an ethanol-rich effluent, an acetaldehyde-rich effluent, and a water-rich effluent; b5') removing impurities and brown oil; feeding at least the ethanol / acetaldehyde / water effluent resulting from step b4) and the water-rich effluent resulting from step b5) to produce at least a water / ethanol / acetaldehyde rafinate, a light brown oil effluent and a heavy brown oil effluent; b6) a water washing step, feeding the gaseous by-product effluent resulting from step b4) and also a portion of the water-rich effluent resulting from said step b5), to produce at least one alcoholic-water effluent.

6. The method according to any one of claims 1 to 5, wherein step c) comprises the following substeps: c1) CO ２ a C-C coupling step between two molecules of and one molecule of 1,3-butadiene; c2) separating the hexenedioic acid; c3) reducing the hexenedioic acid formed in step c1) to give adipic acid.

7. 7. The method according to claim 6, wherein substep c1) is carried out in a solvent in the presence of a metal precursor, a ligand and a reducing agent, characterized in that: the metal precursor is a nickel(II) salt; the ligand is a bidentate dinitrogen ligand; the reducing agent is a metal chosen from zinc or manganese; The solvent is a polar aprotic solvent.

8. 8. The process according to claim 6 or 7, wherein sub-step c1) is carried out at a temperature between 5°C and 70°C.

9. 7. The process according to claim 6, wherein sub-step c3) is carried out in the presence of a catalyst and a reducing agent, said catalyst being palladium on activated carbon and the reducing agent being purified hydrogen originating from sub-step b3).

10. 13. The method according to any one of claims 1 to 12, wherein the biomass is lignocellulosic biomass.

11. A plant suitable for carrying out the method according to any one of claims 1 to 10, comprising: - first reaction section (2); ethanol (3) and CO ２ (4) from biomass (1); a second reaction section (5), which converts ethanol (3) into 1,3-butadiene (6) and diatomic hydrogen (9); and - A third reaction section (7) converts adipic acid (8) into 1,3-butadiene (6), CO ２ (4) and diatomic hydrogen (9).

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