Conversion of biomass-derived hydrocarbon feedstocks to produce adipic acid

Abstract

Disclosed is a process for the conversion of biomass to adipic acid comprising, in order: a) a step of treating biomass to produce ethanol and CO2; b) a step of converting the ethanol obtained at the end of step a) to obtain 1, 3-butadiene; c) a step of synthesizing adipic acid from the 1, 3-butadiene obtained at the end of step b) and the CO2 obtained at the end of step a).

Description

Prior Art

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

[0004] To date, several methods for producing adipic acid have been known and used industrially. The main methods used industrially include oxidizing cyclohexane with oxygen to obtain the intermediate compounds cyclohexanol and cyclohexanone, usually 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 obtain adipic acid.

[0005] Patent US5487987 describes a route for synthesizing adipic acid from biomass, first forming catechol, which is then converted to cis,cis - muconic acid, and the cis,cis - muconic acid can undergo reduction to form adipic acid.

[0006] Patent application US2011 / 0172475 describes a route for synthesizing adipic acid via the production of isobutanol from biomass. The isobutanol is then converted to 1,3 - butadiene, which is in turn converted to adiponitrile and subsequently finally to adipic acid.

[0007] 1,3 - Butadiene is a product of strategic importance for the synthesis of adipic acid. This compound can be obtained by dehydrating bioethanol. This type of method is particularly disclosed in applications WO21193457 and WO21006252 or application WO21052968. It is known that bioethanol can be produced by the fermentation of sugars derived from various biomass. However, the fermentation used for producing ethanol usually does not have a good "carbon" yield because a part of this carbon is lost in the form of CO2. In addition, ethanol produced from "first - generation" (1G) biomass faces competition from the food processing industry, and the loss of a large proportion of this resource in the form of greenhouse gases is even more problematic.

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

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

[0010] Subject Matter of the Invention In the above context, the first object of the present specification is to overcome the problems of the prior art and upgrade carbon, and in particular biobased carbon in the form of CO2, to high-value-added compounds, and in particular to adipic acid. Specifically, the present invention relates to a method for producing adipic acid according to an arrangement of steps, which enables the conversion of biomass into ethanol and CO2, and subsequently the conversion of these products into adipic acid, the method using one or more of the following steps in combination with or in place of some conventional steps for synthesizing adipic acid.

[0011] According to a first aspect, the present invention relates to a method for converting biomass, preferably lignocellulosic biomass, into adipic acid, which successively comprises: a) a step of treating biomass to produce ethanol and CO2; b) a step of converting the ethanol obtained at the end of step a) to obtain 1,3-butadiene; c) a step of synthesizing adipic acid from the 1,3-butadiene obtained at the end of step b) and the CO2 obtained at the end of step a).

[0012] The present invention is based on upgrading CO2, which is a by-product formed during the step of fermenting biomass to obtain ethanol, and optionally reusing the water generated during the dehydration step in some other steps of the method according to the present invention. The present invention thus has a series of individual operations for maximizing the carbon yield of synthesizing adipic acid from biomass, preferably lignocellulosic biomass, and even more preferably "second-generation" (2G) lignocellulosic biomass.

[0013] According to one or more embodiments, step a) comprises the following sub-steps: a1) a step of pretreating biomass to obtain a pretreated substrate; a2) a step of subjecting the pretreated substrate obtained at the end of step a1) to enzymatic hydrolysis or chemical hydrolysis to obtain an enzymatic hydrolysis or chemical hydrolysis slurry; a3) a step of subjecting the enzymatic hydrolysis or chemical hydrolysis slurry obtained at the end of step a2) to ethanol fermentation to obtain ethanol and CO2.

[0014] According to one or more embodiments, sub-step a1) is carried out by steam explosion under acidic conditions at a temperature between 150 °C and 250 °C for a time of 5 minutes to 30 minutes.

[0015] According to one or more embodiments, sub-step a2) is carried out by enzymatic hydrolysis in the presence of Trichoderma reesei cellulase.

[0016] According to one or more embodiments, step b) comprises the following sub-steps: b1) A step of converting ethanol to acetaldehyde, which at least includes a reaction section that is fed at least with a part of the ethanol-rich effluent obtained from step b5), operates at a pressure between 0.1 MPa and 1.0 MPa and at a temperature between 200 °C and 500 °C in the presence of a catalyst, and a separation section that enables the effluent of the reaction section to be separated at least into a gaseous hydrogen effluent and a liquid ethanol / acetaldehyde effluent; b2) A step of converting to butadiene, which at least includes a reaction section that is fed at least with: a part of the ethanol / acetaldehyde effluent obtained from step b1), the liquid ethanol-rich effluent obtained from step b3), and a part of the acetaldehyde-rich effluent obtained from step b5), operates at a temperature between 300 °C and 400 °C and at a pressure between 0.1 and 1.0 MPa in the presence of a catalyst, adjusts the feed flow rate such that the ethanol / acetaldehyde molar ratio at the inlet of the reaction section is between 1 and 5, and a separation section that enables the effluent of the reaction section to be separated at least into a gaseous effluent and a liquid effluent; b3) A step of treating hydrogen, which at least includes a compression section that compresses the hydrogen effluent obtained from step b1) to a pressure between 0.1 MPa and 1.0 MPa, and a gas / liquid washing section that is fed at a temperature between 15 °C and -30 °C with a part of the ethanol-rich effluent obtained from step b5) and a part of the ethanol / acetaldehyde effluent obtained from step b1) and at a temperature between 25 °C and 60 °C with the compressed hydrogen effluent, and produces at least a liquid ethanol-rich effluent and a purified hydrogen effluent; b4) A step of extracting butadiene, which at least includes a compression section that compresses the gaseous effluent obtained from step b2) to a pressure between 0.1 MPa and 1.0 MPa, a gas / liquid washing section including a washing tower that is fed at the top of the tower at a temperature between 20 °C and -20 °C with an ethanol stream composed of the ethanol raw material of the process and / or a part of the ethanol effluent obtained from step b5), and at the bottom of the tower with the cooled gaseous effluent obtained from step b2), and a distillation section that operates at a pressure between 0.1 MPa and 1 MPa and is fed at least with the liquid effluent obtained from step b2) and the liquid effluent from the gas / liquid washing 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 butadiene purification step, which at least includes a gas / liquid washing section, which is fed at the bottom with the crude butadiene effluent obtained from b4), and at the top with a water stream, which can be a water stream from outside the butadiene production process and / or a part of the water effluent obtained from step b5), the washing section producing a pre-purified butadiene effluent at the top and a wastewater effluent at the bottom; b4”) A subsequent butadiene purification step, which is fed at least with the pre-purified butadiene effluent obtained from the said step b4’), and at least produces a purified butadiene effluent; b5) A step of treating the effluent, which is fed at least with the water / ethanol / acetaldehyde raffinate obtained from step b5’), and at least produces an ethanol-rich effluent, an acetaldehyde-rich effluent and a water-rich effluent; b5') A step of removing impurities and brown oil, which is fed at least with the ethanol / acetaldehyde / water effluent obtained from step b4) and the water-rich effluent obtained from step b5), and at least produces a water / ethanol / acetaldehyde raffinate, a light brown oil effluent and a heavy brown oil effluent; b6) A step of washing with water, which is fed with the gaseous by-product effluent obtained from step b4) and also with a part of the water-rich effluent obtained from the said step b5), and at least produces an alcohol-water effluent.

[0017] According to one or more embodiments, step c) includes the following sub-steps: c1) A step of C-C coupling between two CO2 molecules and one 1,3-butadiene molecule; c2) A step of separating out adipic acid; c3) A step of reducing the adipic acid formed in step c1) to obtain adipic acid.

[0018] 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 diazine ligand; - The reducing agent is a metal selected from zinc or manganese; - The solvent is a polar aprotic solvent.

[0019] According to one or more embodiments, sub-step c1) is carried out at a temperature of 5°C to 70°C.

[0020] According to one or more embodiments, sub-step c3) is carried out in the presence of a catalyst and a reducing agent, the catalyst being palladium supported on activated carbon, and the reducing agent being the purified hydrogen derived from sub-step b3).

[0021] According to one or more embodiments, the biomass is lignocellulosic biomass.

[0022] According to a second aspect, the present invention relates to a device adapted to implement the method according to the present invention, said device comprising: - a first reaction section enabling the production of ethanol and CO2 from biomass; - a second reaction section for converting ethanol into 1,3-butadiene and hydrogen; and - a third reaction section enabling the production of adipic acid from 1,3-butadiene, CO2 and hydrogen. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic diagram showing the method and device according to the present invention, said method and device enabling the production of adipic acid from biomass, preferably lignocellulosic biomass.

[0024] DETAILED DESCRIPTION OF EMBODIMENTS Embodiments of the method according to the first aspect of the present invention and the device according to the second aspect of the present invention will now be described in detail. In the following detailed description, many specific details are disclosed in order to provide a deeper understanding of the method and device. However, it will be apparent to those skilled in the art that the method and device can be implemented without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.

[0025] In the present application, the term "comprising" is synonymous with "including" and "containing" (indicating the same), and is inclusive or open and does not exclude other unstated elements. It should be understood that the term "comprising" includes the exclusive and closed term "consisting of". Further, in the present specification, an effluent substantially or only containing compound A corresponds to an effluent containing at least 90% by weight, preferably at least 95% by weight, very preferably at least 99% by weight of compound A.

[0026] In the present application, the groups of chemical elements are by default given according to the CAS classification (CRC Handbook of Chemistry and Physics, published by CRC Press, edited by D.R. Lide, 81st edition, 2000 - 2001). For example, Group VIII (or Group VIIIB) according to the CAS classification corresponds to the metals in columns 8, 9, and 10 according to the new IUPAC classification; Group VIB according to the CAS classification corresponds to the metals in column 6 according to the new IUPAC classification.

[0027] In the present application, biomass refers to any raw material obtained by biological methods, preferably by fermentation of sugars such as those derived from sugar-producing crops such as sugar cane (saccharose, glucose, fructose and sucrose), from sugar beet roots, or from starchy plants (starch) or from lignocellulosic biomass or from hydrolyzed cellulose (mainly glucose, as well as xylose and galactose), which contains variable amounts of water. Biomass is preferably lignocellulosic biomass, and even more preferably "second-generation" (2G) lignocellulosic biomass.

[0028] The present invention can be defined as a method comprising a series of reaction steps that enable the production of adipic acid from biomass, preferably lignocellulosic biomass, and even more preferably "second-generation" (2G) lignocellulosic biomass. More specifically, the present invention relates to a method for converting biomass into adipic acid, which sequentially comprises: a) a step of treating biomass to produce ethanol and CO2; b) a step of converting the ethanol obtained at the end of step a) to obtain 1,3-butadiene; c) a step of synthesizing adipic acid from the 1,3-butadiene obtained at the end of step b) and the CO2 obtained at the end of step a).

[0029] In addition, the present invention can also be defined as a device capable of implementing the method according to the present invention, as Figure 1 shown, the device particularly comprises: - a first reaction section 2 that enables the production of 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 that enables the production of adipic acid 8 from 1,3-butadiene 6, hydrogen 9 and CO2 4.

[0030] First reaction stage (step a) of the method according to the invention) The first reaction section 2 enables the production of ethanol 3 and CO2 4 from biomass 1.

[0031] In one embodiment according to the present invention, the biomass used in the method is lignocellulosic biomass, preferably "second-generation" lignocellulosic biomass. Wood from broad-leaved trees and cereal straw are the most commonly used substrates. They mainly consist of approximately 40% to 50% cellulose, 20% to 25% hemicellulose and 15% to 25% lignin. Other resources, dedicated forestry crops, residues of plants used for the production of alcohols, sugars and grains, residues from the paper industry, and products obtained by converting cellulose and lignocellulosic materials can be used.

[0032] In one embodiment according to the present invention, the method for converting biomass into ethanol more particularly comprises the following sub-steps: a1) A step of pretreating the biomass to obtain a pretreated substrate; a2) A step of subjecting the cellulose residue obtained at the end of step a1) to enzymatic hydrolysis or chemical hydrolysis to obtain an enzymatic hydrolysis or chemical hydrolysis slurry; a3) A step of subjecting the enzymatic hydrolysis or chemical hydrolysis slurry obtained at the end of step a2) to ethanol fermentation to obtain ethanol and CO2.

[0033] Physicochemical pretreatment (step a1)) The pretreatment step a1) enables the production of a pretreated substrate that contains sugars in monomeric form contained in hemicellulose, essentially pentoses such as xylose and arabinose, and hexoses such as galactose, mannose, and glucose, and enables the improvement of the accessibility of cellulose embedded in the lignin and hemicellulose matrix. Many techniques are available, including acid cooking, alkaline cooking, steam explosion, and organic solvent pulping treatments. The efficiency of the pretreatment is measured by the hemicellulose recovery rate and by the sensitivity of the cellulose residue to hydrolysis. Acid pretreatment by steam explosion under mild conditions is most suitable because they enable the complete recovery of pentoses and good accessibility of cellulose to hydrolysis.

[0034] Preferably, the pretreatment step a1) is carried out by steam explosion under acidic conditions at a temperature advantageously between 150 °C and 250 °C and for a time advantageously between 5 and 30 minutes. In this embodiment, step a1) enables the conversion of hemicellulose into monomers while minimizing losses, especially the loss of furfural, and xylose is the main sugar. The released sugars are then extracted by washing in an aqueous phase. The solid residue obtained at the end of the extraction (i.e., the pretreated substrate) then contains only cellulose and lignin.

[0035] Enzymatic or chemical hydrolysis (step a2)) Subsequently, the pretreated substrate obtained at the end of step a1) is hydrolyzed either by an acid method (i.e., a chemical method) or enzymatically using cellulolytic and / or hemicellulolytic enzymes. Microorganisms, such as fungi belonging to the genera Trichoderma, Aspergillus, Penicillium, or Schizophyllum, or anaerobic bacteria belonging to, for example, the genus Clostridium, produce these enzymes, which particularly contain cellulases and xylanases and are suitable for the complete hydrolysis of the polymers that make up plants.

[0036] The acidic route using strong acids, and more particularly sulfuric acid, is effective but requires a large amount of chemical products (acids and subsequent alkalis for neutralization). Enzymatic hydrolysis does not have this drawback; moreover, enzymatic hydrolysis is carried out under mild conditions and is effective.

[0037] In a preferred manner, the pretreated substrate from which the hydrolyzed hemicellulose fraction and optionally lignin have been released or not released is hydrolyzed by cellulolytic and / or hemicellulolytic enzymes produced by specialized strains, and Trichoderma reesei is the most effective and most suitable for producing cellulase when the carbon substrate is derived from cellulose or lignocellulosic biomass. The pretreated substrate to be hydrolyzed is preferably suspended in an aqueous phase at a ratio of 6% to 25%, preferably 10% to 20% dry matter, the pH is adjusted to between 4 and 5.5, preferably between 4.8 and 5.2, and the temperature is adjusted to between 40°C and 60°C, preferably between 45°C and 50°C. The hydrolysis reaction is initiated by adding cellulase; the amount typically used is 10 mg to 30 mg of secreted protein per gram of pretreated substrate. The reaction usually lasts from 15 hours to 48 hours, depending on the efficiency of the pretreatment, the composition of the cellulase mixture, and the amount of enzyme added. The reaction is monitored by measuring the released sugars (especially glucose). The sugar solution (slurry) is then separated from the unhydrolyzed solid fraction consisting essentially of lignin by filtration or centrifugation; this slurry is used for ethanol fermentation. When the hydrolyzed hemicellulose has been released from the cellulose fraction during the treatment step, glucose is the main sugar contained in the slurry.

[0038] Fermentation (step a3)) Ethanol fermentation is a biochemical process in which the sugars (carbohydrates, mainly glucose) contained in the slurry are converted into alcohol, preferably ethanol, in a liquid medium without air (anaerobic). The step of fermenting sugars to obtain ethanol is well known to those skilled in the art.

[0039] Ethanol fermentation is preferably carried out at a temperature between 25°C and 32°C. For a more complete description of traditional fermentation methods, reference can be made to the work “Les Biocarburants, État des lieux, perspectives et enjeux du développement [Biofuels, current situation, perspectives and development challenges]”, Daniel Ballerini, published by Technip, 2006.

[0040] Generally, ethanol is separated from the fermentation slurry by distillation, and the residue consists of stillage. Periodic or continuous distillation of ethanol is necessary because above 14% ethanol, certain yeasts can be “poisoned”, resulting in loss of productivity. Distillation is carried out in order to be able to produce an ethanol feedstock suitable for the dehydration method described subsequently.

[0041] CO2 is recovered in gaseous form at the outlet of the fermenter. According to a basic aspect of the invention, at least part of the CO2 obtained at the end of the fermentation step is sent to the adipic acid synthesis step (step c) of the process according to the invention). The CO2 can be compressed by means of a compressor before storage or before use.

[0042] The ethanol fermentation residues, after separation from ethanol, can be used as an inducing carbon source or as the main carbon source for enzyme production. Preferably, the concentration of the residues is adjusted to obtain a carbon source concentration most suitable for the production process of cellulolytic and / or hemicellulolytic enzymes.

[0043] The enzymatic hydrolysis and fermentation steps can be carried out simultaneously (simultaneous saccharification and fermentation (SSF) process), and are subsequently advantageously followed by a step of distilling and separating the obtained alcohol.

[0044] Second reaction stage (step b) of the method according to the invention) The second reaction section 5 is capable of producing 1,3 - butadiene 6 from the ethanol 3 obtained from the first reaction section 2. There are many methods in the literature for obtaining 1,3 - butadiene from ethanol, in particular the method disclosed in patent application FR3026100, which is described herein as an example.

[0045] Advantageously, the ethanol feedstock used in step b) of the process according to the invention is a feedstock containing at least 80% by weight, preferably at least 90% by weight, and preferably at least 93% by weight of ethanol relative to the total weight of the feedstock. Very preferably, the ethanol feedstock meets the EN 15376 fuel ethanol specification.

[0046] In one embodiment according to the invention, step b) according to the invention comprises the following sub - steps: b1) A step of converting ethanol to acetaldehyde, which at least comprises a reaction section fed with at least a part of the ethanol - rich effluent obtained from step b5), operating at a pressure between 0.1 MPa and 1.0 MPa and at a temperature between 200 °C and 500 °C in the presence of a catalyst, and a separation section enabling the effluent of the reaction section to be separated into at least a gaseous hydrogen effluent and a liquid ethanol / acetaldehyde effluent; b2) A step of converting to butadiene, which at least comprises a reaction section fed with at least a part of the ethanol / acetaldehyde effluent obtained from step b1), a liquid ethanol - rich effluent obtained from step b3), and a part of the acetaldehyde - rich effluent obtained from step b5), operating at a temperature between 300 °C and 400 °C and a pressure between 0.1 and 1.0 MPa in the presence of a catalyst, adjusting the feed flow rate such that the ethanol / acetaldehyde molar ratio at the inlet of the reaction section is between 1 and 5, and a separation section enabling the effluent of the reaction section to be separated into at least a gaseous effluent and a liquid effluent; b3) A step of treating hydrogen, which at least includes a compression section that compresses the hydrogen effluent obtained from step b1) to a pressure between 0.1 MPa and 1.0 MPa, and a gas / liquid washing section that is fed at a temperature between 15°C and -30°C with a part of the ethanol-rich effluent obtained from step b5) and a part of the ethanol / acetaldehyde effluent obtained from step b1), and is fed at a temperature between 25°C and 60°C with the compressed hydrogen effluent, and at least produces a liquid ethanol-rich effluent and a purified hydrogen effluent; b4) A step of extracting butadiene, which at least includes a compression section that compresses the gaseous effluent obtained from step b2) to a pressure between 0.1 MPa and 1.0 MPa, a gas / liquid washing section including a washing tower, the washing tower is fed at the top with an ethanol stream composed of the ethanol raw material of the method and / or a part of the ethanol effluent obtained from step b5) at a temperature between 20°C and -20°C, and is fed at the bottom with the cooled gaseous effluent obtained from step b2), and a distillation section operating at a pressure between 0.1 MPa and 1 MPa, the distillation section is at least fed with the liquid effluent obtained from step b2) and the liquid effluent from the gas / liquid washing 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 butadiene purification step, which at least includes a gas / liquid washing section that is fed at the bottom with the crude butadiene effluent obtained from b4), and is fed at the top with a water stream, the water stream can be a water stream from outside the butadiene production method and / or a part of the water effluent obtained from step b5), the washing section produces a pre-purified butadiene effluent at the top and a waste water effluent at the bottom; b4”) A subsequent butadiene purification step, which is at least fed with the pre-purified butadiene effluent obtained from step b4’), and at least produces a purified butadiene effluent; b5) A step of treating the effluent, which is at least fed with the water / ethanol / acetaldehyde raffinate obtained from step b5’), and at least produces an ethanol-rich effluent, an acetaldehyde-rich effluent, and a water-rich effluent; b5') A step of removing impurities and brown oil, which is at least fed with the ethanol / acetaldehyde / water effluent obtained from step b4) and the water-rich effluent obtained from step b5), and at least produces a water / ethanol / acetaldehyde raffinate, a light brown oil effluent, and a heavy brown oil effluent; b6) A step of washing with water, which is fed with the gaseous by-product effluent obtained from step b4) and also with a part of the water-rich effluent obtained from step b5), and at least produces an alcohol-water effluent.

[0047] Steps b1) to b6) are described in detail below.

[0048] Step b1) of converting ethanol to acetaldehyde According to one embodiment of the present invention, step b1) of converting ethanol to acetaldehyde comprises at least a reaction section that is fed at least in part with a rich ethanol effluent obtained from step b5), said part preferably constituting at least 10% of the flow rate of the rich ethanol effluent obtained from step b5), and optionally advantageously fed with at least a portion of said ethanol feedstock, and a separation section that enables the effluent of the reaction section to be separated into at least a gaseous hydrogen effluent and a liquid ethanol / acetaldehyde effluent.

[0049] The reaction section is capable of converting ethanol to acetaldehyde in the presence of a catalyst preferably composed of a mixture of chromium oxide and copper oxide or any other suitable catalyst. Such catalysts are well known to those skilled in the art.

[0050] The reaction section operates at a pressure between 0.1 MPa and 1.0 MPa, preferably between 0.1 MPa and 0.5 MPa, more preferably between 0.1 MPa and 0.3 MPa, and at a temperature between 200°C and 500°C, preferably between 250°C and 300°C.

[0051] Preferably, the conversion of ethanol is between 30% and 40%, and the selectivity to acetaldehyde is between 85% and 100%, preferably between 90% and 95%. The effluent of the reaction section also contains by-products such as crotonaldehyde, butyraldehyde, diethyl acetal, ethyl acetate, and acetic acid.

[0052] The separation section uses a gas / liquid separation device known to those skilled in the art. Preferably, a gas / liquid separator operating at a pressure between 0.1 MPa and 0.3 MPa and a temperature between 25°C and 60°C is used.

[0053] Step b2) of converting the ethanol / acetaldehyde mixture to butadiene According to one embodiment of the present invention, step b2) of converting to butadiene comprises at least a reaction section that is fed at least in part with a portion of the ethanol / acetaldehyde effluent obtained from step b1), a liquid rich ethanol effluent obtained from step b3), a portion of the rich acetaldehyde effluent obtained from step b5), and optionally advantageously fed with a rich ethanol stream obtained from step b5), and a separation section that enables the effluent of the reaction section to be separated into at least a gaseous effluent and a liquid effluent. The reaction section may also be fed with an external stream of acetaldehyde.

[0054] Adjust the flow rates of the various feeds to the reaction section of step b2) such 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 very preferably between 2.4 and 2.7.

[0055] The reaction section is capable of converting 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 very 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 rate 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%. The conversion rate refers to the molar ratio of the flow rate of ethanol and acetaldehyde in the effluent from the reaction section to the flow rate of ethanol and acetaldehyde in the feed to the reaction section. It is carried out in the presence of a catalyst, which is advantageously a silica-supported catalyst selected from catalysts containing tantalum oxide, zirconium oxide, or niobium oxide, preferably a catalyst containing 2% tantalum oxide (see, for example, Corson, Jones, Welling, Hincbley, Stahly, Ind. Eng Chem. 1950, 42, 2, 359-373). The second reaction zone operates at a temperature between 300 °C and 400 °C, preferably between 320 °C and 370 °C, and at a pressure between 0.1 MPa and 1.0 MPa, preferably between 0.1 MPa and 0.5 MPa, and preferably between 0.1 MPa and 0.3 MPa.

[0056] Preferably, about 65 to 80% of the acetaldehyde is converted in the reaction section. The effluent from the reaction section thus still contains ethanol. Many impurities can be produced together with butadiene, including ethylene, propylene, diethyl ether (DEE), ethyl acetate, butanol, hexanol, butene, pentene, pentadiene, hexene, and hexadiene.

[0057] Since the reaction section is fed with the acetaldehyde effluent obtained from step b5) of treating the effluent, the ratio of ethanol to acetaldehyde at the inlet of this section is adjusted by detecting a portion of the ethanol effluent obtained from step b5) fed to step b1), and thus acetaldehyde is produced. In fact, the remaining portion of the ethanol-rich effluent obtained from step b5) is fed to step b3) of treating hydrogen, and after washing the hydrogen effluent, the liquid ethanol-rich effluent obtained from step b3) is formed, which is fed to step b2). This ethanol-rich liquid effluent obtained from step b3) contains only a very small amount of acetaldehyde.

[0058] The separation section uses a gas / liquid separation device known to those skilled in the art. A gas / liquid separator operating at a pressure between 0.1 MPa and 0.3 MPa and a temperature between 25 °C and 60 °C will preferably be used.

[0059] Step b3) of treating hydrogen According to one embodiment, step b3) of treating hydrogen gas comprises at least a compression section fed with the hydrogen gas effluent obtained from step b1) and a gas / liquid scrubbing section fed with a portion of the ethanol effluent obtained from step b5) and a portion of the ethanol / acetaldehyde effluent obtained from step b1), and produces at least a liquid ethanol-rich effluent and a purified hydrogen gas effluent. Preferably, step b3) is not fed with any other streams.

[0060] Said portion of the ethanol / acetaldehyde effluent obtained from step b1) is between 0 and 100%. Using a portion of the ethanol / acetaldehyde effluent enables reduction of the flow rate of a portion of the ethanol-rich effluent obtained from said step b5).

[0061] Step b3) enables obtaining a purified hydrogen gas effluent with high purity, i.e., containing at least 90 mol% hydrogen gas, preferably 99 mol% hydrogen gas, and preferably 99.8 mol% hydrogen gas. The purified hydrogen gas effluent also contains trace amounts of water and ethanol. This step also enables recovery of the ethanol and acetaldehyde contained in the hydrogen gas effluent obtained from step b1), thereby enabling their recycling and maximizing the overall yield of the process.

[0062] Using a portion of the ethanol-rich effluent obtained from step b5) and a portion of the ethanol / acetaldehyde effluent obtained from step b1) instead of water - as practiced in the prior art - enables reduction of the total flow rate of water recycled in the process. Thereby, the total flow rate of water fed to steps b5) and b5’) for treating the effluents is reduced, thereby reducing the equipment size and the utility consumption of steps b5) and b5’). In addition, as described above, the ethanol-rich effluent obtained from step b3) can be directly fed to step b2) for conversion to butadiene without having to be treated in step b5) for treating the effluents.

[0063] The hydrogen gas effluent obtained from step b1) is compressed in the compression section to a pressure between 0.1 MPa and 1.0 MPa, advantageously between 0.1 MPa and 0.7 MPa, and preferably between 0.4 MPa and 0.68 MPa. The effect of this compression is firstly to reduce the gas volume flow rate and secondly to improve the efficiency of downstream scrubbing.

[0064] Subsequently, the compressed hydrogen effluent is cooled to a temperature between 25°C and 60°C, preferably between 30°C and 40°C, and then fed to the bottom of the wash column of the wash section. In the wash column, it contacts the portion of the ethanol effluent obtained from step b5) and the portion of the ethanol / acetaldehyde effluent obtained from step b1), and these portions are fed at the top and the midpoint of the wash column respectively. Before feeding to the wash column, each of these two portions is cooled to a temperature between 15°C and -30°C, preferably between 0°C and -15°C. Advantageously, the ethanol-rich effluent obtained from step b5) will be fed at a temperature lower than that of the portion of the ethanol / acetaldehyde effluent obtained from step b1), thereby creating a thermal gradient between the top and the bottom of the column and limiting solvent losses in the purified hydrogen effluent. The gas / liquid wash column of the wash section is equipped with trays or random or structured packings.

[0065] Optional step b3') of finally treating the hydrogen effluent Step b3’) of the final hydrogen treatment is advantageously carried out at the end of step b3). The step b3’) includes at least one gas / liquid wash section fed with the purified hydrogen effluent obtained from b3) and a pure water effluent from outside the process or the water-rich effluent obtained from step b5), and produces a purified hydrogen effluent and a wastewater effluent.

[0066] The wash section includes at least one gas / liquid wash section that is fed with the purified hydrogen effluent obtained from b3) at the bottom and fed with a pure water effluent or the water-rich effluent obtained from step b5) at the top, and produces a purified hydrogen effluent at the top and a wastewater effluent at the bottom.

[0067] This step enables the recovery of the final traces of ethanol that may be contained in the purified hydrogen effluent obtained from b3). The step b3’), which is similar to the hydrogen treatment according to the prior art, however uses a much lower water flow rate than those used in the prior art because the hydrogen effluent fed to step b3’) has been pre-treated by step b3) and thus has released all the acetaldehyde entrained in the hydrogen effluent obtained from step b1). Under all other identical conditions, removing trace ethanol by water washing requires a lower flow rate than removing trace acetaldehyde. In addition, since ethanol is less volatile than acetaldehyde, under the same operating conditions, the entrainment of ethanol is much lower than that of acetaldehyde.

[0068] Step b4) of extracting butadiene According to one embodiment of the present invention, step b4) of extracting butadiene, which at least includes a compression section, a gas / liquid scrubbing section, and a distillation section, is fed at least with the gaseous and liquid effluents obtained from said step b2), and with an ethanol stream composed of the ethanol feedstock of the process and / or a part of the ethanol effluent obtained from step b5), and produces at least one gaseous by-product effluent, a crude butadiene effluent, and an ethanol / acetaldehyde / water effluent.

[0069] The ethanol stream fed to step b4) preferably contains at least 80% by weight, preferably at least 90% by weight, and 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 contains less than 10% by weight, preferably less than 5% by weight, and preferably less than 1% by weight of acetaldehyde. Preferably, the ethanol stream fed to step b4) preferably contains less than 20% by weight, preferably less than 5% by weight, preferably less than 1% by weight of water.

[0070] In a preferred arrangement, the ethanol stream fed to step b4) consists of the ethanol feedstock of the process. An advantage of this arrangement is that the feedstock does not contain reaction by-products formed in steps b1) and b2) and which would be concentrated by recycling. In particular, this ethanol feedstock does not contain acetaldehyde, or contains only trace amounts of acetaldehyde.

[0071] In another preferred arrangement, the ethanol stream consists of a part of the ethanol effluent obtained from step b5) of treating the effluent.

[0072] Using an ethanol stream containing very little or no acetaldehyde minimizes the entrainment of acetaldehyde in the gaseous by-product effluent discharged at the top of the gas / liquid scrubbing section, reduces the total yield loss of the process, and the washing water flow rate required in step b6).

[0073] The gaseous effluent obtained from step b2) is compressed in the compression section to a pressure between 0.1 MPa and 1.0 MPa, preferably between 0.1 MPa and 0.7 MPa, and preferably between 0.2 MPa and 0.5 MPa. The effect of this compression is firstly to reduce the volumetric flow rate of the gas, and secondly to improve the efficiency of downstream scrubbing. Preferably, the compressed gaseous effluent is subsequently cooled to a temperature between 25°C and 60°C, preferably between 30°C and 40°C.

[0074] Preferably, the gas / liquid scrubbing section of step b4) includes a scrubbing tower, which is fed at the top with the ethanol stream fed to step b4), and at the bottom with the cooled compressed gaseous effluent, and produces a gaseous by-product effluent at the top, and a liquid effluent for feeding the distillation section of step b4) at the bottom.

[0075] Before feeding to the top of the gas / liquid scrubbing column of the scrubbing section, the ethanol stream fed for step b4) is cooled to a temperature between 20 °C and -20 °C, preferably between 15 °C and 5 °C. The advantage of cooling the ethanol stream is to improve the performance of the scrubbing operation by minimizing the entrainment of ethanol and acetaldehyde in the gaseous by-product stream. Thereby, all butadiene present in the compressed and cooled gaseous effluent obtained from step b2) is removed, and the vapor by-product effluent discharged at the top of the gas / liquid scrubbing section is free of butadiene.

[0076] Incidentally, minimizing the entrainment of acetaldehyde in the gaseous by-product effluent enables a significant reduction in the flow rate of water required in step b6) of washing the gaseous by-products with water, the purpose of step b6) being to recover ethanol and any trace acetaldehyde entrained in the gaseous by-product effluent discharged at the top of the ethanol scrubbing section of step b4).

[0077] Preferably, the butadiene-rich ethanol stream discharged 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), so as to separate at the top a vapor effluent containing most of the butadiene, called the crude butadiene effluent, and at the bottom an ethanol / acetaldehyde / water residue. The term "most" means more than 80%, preferably more than 90%, preferably more than 95%, even more preferably more than 98%, very preferably more than 99% and very advantageously all of the butadiene contained in the feed to the distillation section. This ethanol / acetaldehyde / water residue contains ethanol and acetaldehyde and also contains the water produced in step b2) and the 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') of treating the effluent. The distillation section operates at a pressure between 0.1 MPa and 1 MPa and preferably between 0.2 MPa and 0.5 MPa.

[0078] First butadiene purification step b4')[[]] The first butadiene purification step b4') comprises at least a gas / liquid scrubbing section which is fed at the bottom with the crude butadiene effluent obtained from b4) and at the top with a water stream which may be a water stream external to the process for producing butadiene and / or a portion of the water effluent obtained from step b5), the scrubbing section producing at the top a pre-purified butadiene effluent and at the bottom a waste water effluent. Preferably, the water stream is a water stream external to the process.

[0079] The waste water effluent contains acetaldehyde and a small amount of butadiene and can be sent to step b5) of treating the effluent, the acetaldehyde distillation section or step b5').

[0080] The purpose of step b4’) is to remove polar impurities, especially acetaldehyde, the presence of which in the final butadiene must not exceed a certain number of ppm. The crude butadiene effluent obtained from b4) contains most of the butadiene but still contains many impurities, including a large amount of acetaldehyde, which forms an azeotrope with butadiene and thus cannot be completely removed by distillation during step b4). Thus, the flow rate of the water stream is adjusted to obtain the desired acetaldehyde specification in the pre-purified butadiene effluent.

[0081] Before feeding the water stream to the gas / liquid scrubbing section, the water stream is cooled to a temperature below 25 °C, preferably below 20 °C, in order to carry out the scrubbing with a reduced 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 obtained from step b4). The pressure of the scrubbing column is determined 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 and even more preferably between 0.2 MPa and 0.3 MPa.

[0082] Subsequent butadiene purification step b4'')[[]] According to one embodiment of the invention, the subsequent butadiene purification step b4”) is fed at least with the pre-purified butadiene effluent obtained from said step b4’) and produces at least a purified butadiene effluent.

[0083] This step b4”) enables the butadiene produced in the reaction step to be purified to a very high purity level (more than 99.5 wt%, preferably more than 99.8 wt%, and very preferably more than 99.9 wt%), while limiting product losses by separating out the impurities that were not discharged or only partially discharged during steps b4), b4’).

[0084] In a first embodiment of the invention, said step b4”) comprises at least one drying section, a cryogenic distillation section and a section for separating butadiene / butene by liquid-liquid extraction.

[0085] The pre-purified butadiene effluent obtained from step b4’) is fed to the drying section. The purpose of this section is to achieve the desired water specification in the final product (purified butadiene effluent) and to enable cryogenic separation without the risk of hydrate formation. A dried butadiene effluent is obtained at the outlet of the drying section. Dried butadiene means less than 10 ppm, preferably less than 5 ppm, preferably less than 1 ppm of water.

[0086] The drying section preferably comprises a dryer consisting of one or more volumes containing one or more adsorbents having a strong affinity for water. By way of non-limiting example, the adsorbent may consist of silica and / or alumina. By way of non-limiting example, the adsorbent may be a zeolite such as zeolite 3A or 4A. When one or more of the adsorbents are saturated with water, the pre-purified butadiene effluent is fed to another volume containing one or more fresh or regenerated adsorbents.

[0087] The adsorbent can be regenerated by changing the water partial pressure in the volume, by changing the temperature in the volume, or by changing both the water partial pressure and the temperature in the volume. In the latter embodiment, one or more water-saturated adsorbents are regenerated by heating the volume and simultaneously feeding a stream containing no water or very little water to the volume. "Containing no water or very little water" means less than 500 ppm, preferably less than 350 ppm, preferably less than 10 ppm, preferably less than 5 ppm, very preferably less than 1 ppm. By way of non-limiting example, such a stream containing no water or very little water can be a nitrogen stream, an air stream, a hydrocarbon stream or a hydrogen stream. In a preferred embodiment of the invention, a portion of the purified hydrogen effluent obtained from step b3) is used.

[0088] Before being fed to a volume containing one or more adsorbents to be regenerated, the stream containing no water or very little water is heated to a temperature sufficient to regenerate one or more adsorbents, preferably to approximately 250 °C.

[0089] According to a first embodiment, the dried butadiene effluent is subsequently fed to a low-temperature distillation section using a distillation column. The light product leaves at the top of the low-temperature distillation column at -25 °C to -35 °C. The bottom is at a temperature between 20 °C and 50 °C, preferably between 25 °C and 45 °C, very preferably between 30 °C and 40 °C, and the pressure at the top of the column is between 0.3 MPa and 0.4 MPa, preferably 0.35 MPa. The advantage of this column is that it has a very high efficiency in separating the last non-condensable substances without loss of butadiene (less than 0.05%). This thus avoids a large recycle to step b4) and loss of butadiene.

[0090] Still according to this first embodiment, the bottom product of the low-temperature distillation section (referred to as the topped butadiene effluent) contains butene as the main impurity. The topped butadiene effluent is fed to a section for separating butadiene / butene by liquid-liquid extraction as described in patent FR 2,036,057.

[0091] The section for separating butadiene / butene is a liquid-liquid extraction section, where the overhead butadiene effluent is fed into the middle section of the first liquid-liquid extraction column, and a stream of polar solvent (preferably DMSO) is fed at the top. A saturated hydrocarbon solvent, preferably pentane or cyclohexane, is fed at the bottom. The flow rate and flow rate ratio of the polar solvent to the hydrocarbon solvent are adjusted such that most of the butene will be entrained by the hydrocarbon solvent and most of the butadiene will be entrained by the polar solvent.

[0092] Subsequently, the butene / hydrocarbon mixture obtained at the top of the first extraction column is processed in a first distillation column to obtain a butene effluent at the top and a recyclable hydrocarbon solvent at the bottom.

[0093] Subsequently, the butadiene / polar solvent mixture is fed to the top of a second liquid-liquid extraction column, where 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 the hydrocarbon solvent is introduced at the bottom of the second liquid-liquid extraction column.

[0094] Subsequently, the butadiene / hydrocarbon mixture obtained at the top of the second liquid-liquid extraction column is processed in a distillation column to obtain a purified butadiene effluent at the top and a recyclable hydrocarbon solvent at the bottom.

[0095] Preferably, the liquid-liquid extraction column in the section for separating butadiene / butene operates at a pressure between 0.1 MPa and 1 MPa and a temperature between 20 °C and 60 °C.

[0096] In another embodiment of the present invention, the step b4”) includes at least distillation and extractive distillation. The distillation step can be carried out upstream or downstream of the extractive distillation step. By way of non-limiting example, the extractive distillation can be carried out with solvents such as N-methylpyrrolidone, dimethylformamide or acetonitrile.

[0097] Step b5) of treating the effluent According to one embodiment of the present invention, the step b5) of treating the effluent is fed at least with the raffinate of water / ethanol / acetaldehyde obtained from the step b5’), and at least a rich-ethanol effluent, a rich-acetaldehyde effluent and a rich-water effluent are produced. If the wastewater effluent obtained from the step b4’), or the alcohol-water effluent obtained from the step b6), or the wastewater effluent obtained from the step b3’) has not undergone the step b5’) of removing impurities and brown oil, they can be directly fed to the step b5) of treating the effluent. The section b5) is also advantageously fed with a part of the ethanol raw material.

[0098] Preferably and different from the prior art, no discharge of ethanol or acetaldehyde loss is carried out.

[0099] Preferably, the step b5) includes at least two distillation sections: a “water and ethanol” distillation section and an “acetaldehyde” distillation section.

[0100] The water / ethanol / acetaldehyde effluent obtained from step b5') and optionally the wastewater effluent obtained from step b4') are fed to the acetaldehyde distillation section, where acetaldehyde is separated to form an acetaldehyde-rich effluent, and the residue from the acetaldehyde distillation section is fed to the water and ethanol distillation section, enabling the separation of an ethanol-rich effluent at the top and a water-rich effluent at the bottom. Since the alcohol-water effluent obtained from step b6) and the wastewater effluent obtained from step b3') do not contain acetaldehyde, they can be directly fed to the water and ethanol distillation section.

[0101] The ethanol-rich effluent obtained from step b5) consists mainly of ethanol. "Mainly" means more than 80% by weight, preferably more than 84% by weight. By way of non-limiting example, the ethanol-rich effluent obtained from step b5) may contain impurities such as water, ethyl acetate, butanol, and hexanol.

[0102] Impurities other than water account for less than 10% by weight of the stream, advantageously less than 5% by weight, and more preferably less than 2% by weight.

[0103] The acetaldehyde-rich effluent obtained from step b5) consists mainly of acetaldehyde and ethanol. "Mainly" means more than 80% by weight, preferably more than 85% by weight. By way of non-limiting example, the acetaldehyde-rich effluent obtained from step b5) may contain impurities such as water, ethyl acetate, or acetone.

[0104] Impurities other than water account for less than 10% by weight of the stream, and preferably less than 5% by weight.

[0105] Subsequently, the acetaldehyde-rich effluent, ethanol-rich effluent, and water-rich effluent are recycled to the remainder of the process according to the invention. A portion of the ethanol-rich effluent fed to step b1) is preferably at least 0.7, preferably at least 0.75, more preferably at least 0.8. A portion 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 portion of the water-rich effluent fed to step b5') for removing impurities and brown oil is advantageously between 0 and 1, preferably between 0.3 and 0.6, and advantageously between 0.4 and 0.5.

[0106] In another embodiment of the present invention, the acetaldehyde-rich effluent, ethanol-rich effluent, and water-rich effluent undergo a purification step before being recycled to the remainder of the process. "Purification" means contacting the effluent with an adsorbent such as activated carbon, silica, alumina, or a functionalized polymer resin. For example, activated carbon enables the removal of trace amounts of butanol and hexanol contained in the ethanol-rich stream. For example, a basic resin enables the removal of acetic acid present in the water-rich effluent. When the adsorbent becomes saturated and cannot ensure the purity of the acetaldehyde-rich effluent, ethanol-rich effluent, and water-rich effluent, they are removed or regenerated for reuse.

[0107] Step b5') of removing impurities and brown oil According to one embodiment of the present invention, the step b5') of removing impurities and brown oil is fed at least with the ethanol / acetaldehyde / water effluent obtained from step b4) and a portion of the water effluent obtained from step b5), and at least produces an ethanol / acetaldehyde / water raffinate, a light brown oil effluent, and a heavy brown oil effluent.

[0108] Preferably, the step b5') includes at least a washing / backwashing section, a light brown oil distillation section, and a heavy brown oil distillation section.

[0109] The preferred washing / backwashing section is fed at an intermediate point with the ethanol / acetaldehyde / water effluent obtained from step b4), which is advantageously mixed with the wastewater effluent obtained from step b4'), the alcohol-water effluent obtained from step b6), and the wastewater effluent obtained from step b3') (if the latter step is carried out), and preferably with a portion of the wastewater effluent obtained from step b4'). Since these effluents are richer in water than the ethanol / acetaldehyde / water effluent obtained from step b4), introducing them as a mixture enables the limitation of hydrocarbon losses in the raffinate.

[0110] The preferred washing / backwashing section is fed at the bottom with a hydrocarbon effluent and at the top with a portion of the water effluent obtained from step b5) (which does not contain ethanol and acetaldehyde). The hydrocarbon effluent and a portion of the water effluent obtained from step b5) are fed at a temperature preferably between 10 °C and 70 °C, more preferably between 45 °C and 55 °C. The washing / backwashing section produces at the top a washing hydrocarbon extract carrying a portion of the impurities and brown oil, and at the bottom the ethanol / acetaldehyde / water raffinate.

[0111] The washing / backwashing section is preferably operated at a pressure between 0.1 MPa and 0.5 MPa, more preferably between 0.2 MPa and 0.4 MPa. Preferably, water is added for backwashing such that the water content in the water / ethanol / acetaldehyde raffinate is greater than 30 wt%, more preferably greater than 40 wt%.

[0112] In one embodiment, the contact between the two liquid phases in the washing / backwashing section is carried out in a liquid-liquid extractor. Various forms of contact can be envisaged. In a non-limiting manner, mention may be made of a packed column, a pulsed column or an agitated compartmented column (une colonne compartimentée agitée). In another embodiment, the contact between the two liquid phases in the washing / backwashing section is carried out in a membrane contactor or in a cascade of membrane contactors. This mode of contact is particularly suitable for the system used. Specifically, it is known that water-ethanol-hydrocarbon mixtures form stable emulsions, which can be problematic in liquid-liquid extractors. Membrane contactors are able to generate a large contact area, promoting the transfer of impurities and oil to the hydrocarbon phase without forming emulsions.

[0113] The washed hydrocarbon extract feeds the light brown oil distillation section, which produces the light brown oil effluent as a distillate and a hydrocarbon residue containing the heavy fraction of the brown oil.

[0114] The light brown oil effluent consists of impurities (mainly diethyl ether, ethyl acetate and crotonaldehyde) produced in reaction step b2) and the light fraction of the brown oil, which consists of a smaller amount of impurities including pentene, isoprene, butyraldehyde and vinyl ethyl ether. This effluent can be burned to provide part of the heat required for the hot oil circuit or steam boiler of the process, or distilled to recover the diethyl ether effluent and / or the ethyl acetate / crotonaldehyde effluent, which can be upgraded or recycled to the reaction section of step b2) for re-conversion.

[0115] The hydrocarbon residue contains substantially the hydrocarbon used for washing, but also the heaviest fraction of the brown oil. To avoid the accumulation of brown oil by recycling the hydrocarbon effluent to the liquid-liquid extractor, a part of the hydrocarbon residue is treated in the heavy oil distillation section consisting of a distillation column, which produces a hydrocarbon distillate consisting mainly of hydrocarbons with a small amount of residual trace brown oil, and as a residue, the heavy brown oil effluent contains more than 80%, preferably more than 85% hydrocarbons and the heaviest brown oil. The part of the hydrocarbon effluent sent to the oil distillation section is between 5% and 30%, and preferably between 10% and 20% of the total flow rate of the hydrocarbon residue. The hydrocarbon distillate is mixed with the part of the hydrocarbon residue not treated in the heavy oil distillation section to form a hydrocarbon effluent that feeds the washing / backwashing section.

[0116] This effluent, which preferably accounts for 0.1 to 20%, preferably 0.3 to 5% of the feedstock of the heavy oil distillation section, can be burned to provide part of the heat required for the hot oil circuit or steam boiler of the process. A hydrocarbon make-up equal to the losses at the bottom of the heavy oil distillation section is required to keep the washing flow rate constant. The column is adjusted to keep the concentration of brown oil in the hydrocarbon recycle loop (hydrocarbon effluent / washing hydrocarbon effluent loop) constant.

[0117] Remove light and heavy brown oil effluents from the process.

[0118] The ethanol / acetaldehyde / water effluent obtained from step b4) mainly contains ethanol, acetaldehyde and water, as well as impurities such as diethyl ether, ethyl acetate and brown oil as defined above. If these impurities are sent back to reaction steps b1) and b2) in the acetaldehyde-rich distillation fraction and / or ethanol-rich distillation fraction, and if they are only partially converted in the reaction sections of stages b1) and b2), these impurities may accumulate. Step b5’) enables the recovery of a portion of these impurities prior to step b5) of treating the effluent, enabling the avoidance of brown oil stratification in the distillation column, simplifying the distillation scheme, and obtaining ethanol effluent, acetaldehyde effluent and water effluent with higher purity than the prior art at the end of step b5).

[0119] Washing the ethanol / acetaldehyde / water effluent obtained from step b4) with a hydrocarbon effluent entrains certain impurities, while backwashing the hydrocarbon stream entrains a portion of the impurities and brown oil as well as a portion of the water effluent obtained from step b5), thereby limiting any losses of acetaldehyde and ethanol.

[0120] Surprisingly, the applicant has found that by adding certain hydrocarbons to the ethanol / acetaldehyde residue obtained from step b4), liquid-liquid phase separation can be achieved. This result is surprising because the ethanol / acetaldehyde residue obtained from the step is highly enriched in ethanol and acetaldehyde, which can be miscible with hydrocarbons in any proportion. By the proper selection of the hydrocarbons, the applicant has found that liquid-liquid phase separation can be achieved and thereby liquid-liquid extraction can be carried out to remove some of the impurities contained in the ethanol / acetaldehyde / water effluent obtained from step b4). The hydrocarbon effluent may contain saturated and / or unsaturated and / or aromatic hydrocarbons, preferably saturated hydrocarbons. Advantageously, the hydrocarbon effluent consists of a mixture of hydrocarbons having 6 to 40 carbon atoms, preferably 10 to 20 carbon atoms. By way of non-limiting example, the hydrocarbon effluent may be a desulfurized gas oil or kerosene fraction or a hydrocarbon fraction produced by a Fischer-Tropsch type unit.

[0121] Adding water to the washing / backwashing section enables better implementation of the method according to the invention for removing impurities and brown oil.

[0122] Step b6) of washing the gaseous by-products with water According to one embodiment of the invention, step b6) of washing with water is fed with the gaseous by-product effluent obtained from step b4) and a portion of the water-rich effluent obtained from said step b5), and produces at least one alcohol-water effluent.

[0123] The purpose of step b6) is to recover a small amount of the ethanol fraction entrained in the gaseous by-product effluent obtained from step b4) to improve the overall yield of the process.

[0124] The amount of water obtained from step b5) required in step b6) according to the present invention is very low, different from the amount required in the prior art, because the vapor effluent obtained from step b2) is washed in step b4) with an ethanol stream containing very little or no acetaldehyde. Compared with the amount of water that would be required in the case of trace amounts of acetaldehyde being present in the gaseous by-product effluent obtained from step b4), only a small fraction of ethanol is retained in this stream, which can be easily recovered with a small amount of water.

[0125] The water carrying ethanol after washing is taken out from step b6) and forms an alcohol-water effluent. It is preferably fed directly to step b5) in a water-ethanol distillation section without hindering the acetaldehyde distillation section. In another embodiment of the present invention, it is preferably fed to step b5') for removing impurities and brown oil.

[0126] Step b) of the method according to the present invention can minimize the flow rate of the effluent to be treated in the steps of treating the effluent and reduce the loss of butadiene as much as possible, so that more than 98%, preferably more than 99% of the butadiene produced at the end of the reaction step can be recovered in the purified butadiene effluent.

[0127] Third reaction stage (step c) of the method according to the invention) The third reaction section 7 includes at least one reactor, into which 1,3-butadiene 6 obtained from the second reaction section 5, CO2 4 obtained from the first reaction section 2, and hydrogen 9 from reaction section 5 are introduced.

[0128] According to a preferred embodiment, step c) of the method according to the present invention includes the following sub-steps: c1) A C-C coupling step between two CO2 molecules and one 1,3-butadiene molecule; c2) A step of separating out adipic acid; c3) A step of reducing the adipic acid formed in step c1) to obtain adipic acid.

[0129] Step c1) Advantageously, step c1) is carried out in at least one reactor, in which the reagents are brought into contact with a metal precursor, a ligand, and a reducing agent in a solvent. The reagents are 1,3-butadiene obtained from the second reaction section and CO2 produced in the first reaction section.

[0130] The metal precursor is preferably a nickel (II) salt. More preferably, the nickel salt is selected from nickel tetrabromide (NiBr4(DBA)2) of tetrabutylammonium, NiCl2(DME), NiBr2(DME).

[0131] The ligand is preferably a bidentate diazine (N,N) ligand, such as a derivative of bipyridine or phenanthroline. More preferably, the ligand is selected from ligand 2-methyl-4,7-diphenyl-1,10-phenanthroline, 4,7-diphenyl-1,10-phenanthroline, and 6-methyl-2,2'-bipyridine.

[0132] The reducing agent is preferably a metal selected from zinc or manganese. The reducing agent is preferably manganese. A metal-photochemical or electrochemical pair can also be used for the reduction step.

[0133] The solvent is preferably a polar aprotic solvent. The solvent advantageously has a dielectric constant at 20 °C greater than 25.0 and / or a dipole moment greater than 2.5 D. The solvent is preferably selected from N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMA), acetonitrile, dimethyl sulfoxide (DMSO), HMPT, hexamethylphosphoric triamide (HMPA), nitrobenzene, formamide, nitromethane, and propylene carbonate. Even more preferably, the solvent is N,N-dimethylacetamide (DMA).

[0134] Step c1) is advantageously carried out at a temperature between 5 °C and 70 °C, preferably between 40 °C and 70 °C.

[0135] Before the separation step c2), the reaction medium is preferably gradually neutralized with an acid such as HCl and water.

[0136] Step c2) During the separation step c2), adipic acid is advantageously extracted from the aqueous medium with ethyl acetate by means of liquid-liquid extraction. Preferably, the ethyl acetate effluent rich in adipic acid is dried and then distilled. One of the effluents is mainly ethyl acetate, which can be recycled. The other effluent is rich in adipic acid, which can be further purified by, for example, crystallization and then diluted in a solvent such as methanol for feeding to the final step.

[0137] Step c3) Step c3) includes reducing adipic acid to obtain adipic acid. Step c3) can be carried out in at least one reactor, where adipic acid diluted in methanol is introduced in the presence of a catalyst and a reducing agent.

[0138] The catalyst used in step c3) is preferably a metal precursor or metal alloy on a support, such as palladium on activated carbon or Raney nickel. More preferably, the catalyst is based on palladium supported on activated carbon.

[0139] Preferably, the purified hydrogen from step b3) of the second reaction section can be used as a reducing agent in step c3). The reduction step c3) is preferably carried out at a temperature between 10 °C and 50 °C, and more preferably between 15 °C and 25 °C.

[0140] Embodiment 1 / Case of synthesizing adipic acid from glucose without upgrading the CO2 in the fermentation step The equation for the glucose fermentation reaction is C6H 12 O6 → 2 C2H5OH + 2 CO2. Thus, 66.7% of the carbon in the glucose molecule is converted to ethanol and 33.3% is converted to CO2.

[0141] For a 170 Kta glucose feedstock, fermentation would theoretically be able to produce 86.8 Kta of ethanol and 83 Kta of CO2.

[0142] Assuming a weight yield of 40% 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 the CO2 is not upgraded to adipic acid, at most 45.4% of the carbon in the glucose can be upgraded to adipic acid (see Table 1).

[0143] 2 / Case of synthesizing adipic acid from glucose with upgraded CO2 in the fermentation step The equation for the glucose fermentation reaction is C6H 12 O6 → 2 C2H5OH + 2 CO2. Thus, 66.7% of the carbon in the glucose molecule is converted to ethanol and 33.3% is converted to CO2.

[0144] For a 170 Kta glucose feedstock, fermentation would theoretically be able to produce 86.8 Kta of ethanol and 83 Kta of CO2.

[0145] Assuming a weight yield of 40% 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. 56.6 Kta of CO2 is required to produce 93.9 Kta of adipic acid. Fermentation thus produces enough CO2 such that the process is self-sufficient in terms of CO2. If the CO2 is upgraded to adipic acid, at most 68.1% of the carbon from glucose can be upgraded to adipic acid (see Table 1).

[0146] Table 1 Biomass upgrading product Yield in Kt / a <![CDATA[C's % (not in compliance) that can be upgraded to adipic acid without upgrading CO2 in the first step]]> <![CDATA[The % (compliance) of C that can be upgraded to adipic acid in the case of upgrading CO2 in the first step]]> Ethanol 86.8 45.4% 45.4% <![CDATA[CO2]]> 83.0 22.7% Total 45.4% 68.1%

Claims

1. A method for converting biomass into adipic acid, which sequentially includes: a) A step of treating biomass to produce ethanol and CO2; b) A step of converting the ethanol obtained at the end of step a) to obtain 1,3-butadiene and hydrogen; c) A step of synthesizing adipic acid from the 1,3-butadiene and hydrogen obtained at the end of step b) and the CO2 obtained at the end of step a).

2. The method according to claim 1, wherein step a) includes the following sub-steps: a1) A step of pretreating biomass to obtain a pretreated substrate; a2) A step of subjecting the pretreated substrate obtained at the end of step a1) to enzymatic hydrolysis or chemical hydrolysis to obtain an enzymatic hydrolysis or chemical hydrolysis slurry; a3) A step of subjecting the enzymatic hydrolysis or chemical hydrolysis slurry obtained at the end of step a2) to alcohol fermentation to obtain ethanol and CO2.

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

4. The method according to any one of claims 2 and 3, wherein sub-step a2) is carried out by enzymatic hydrolysis in the presence of cellulase produced by Trichoderma reesei.

5. The method according to any one of claims 1 to 4, wherein step b) includes the following sub-steps: b1) A step of converting ethanol into acetaldehyde, which at least includes a reaction section that is fed at least in part with a rich ethanol effluent obtained from step b5), operates at a pressure between 0.1 MPa and 1.0 MPa and a temperature between 200°C and 500°C in the presence of a catalyst, and a separation section that enables the effluent of the reaction section to be separated at least into a gaseous hydrogen effluent and a liquid ethanol / acetaldehyde effluent; b2) A step of converting into butadiene, which at least includes a reaction section that is fed at least in part with a portion of the ethanol / acetaldehyde effluent obtained from step b1), a liquid rich ethanol effluent obtained from step b3), and a portion of the rich acetaldehyde effluent obtained from step b5), operates at a temperature between 300°C and 400°C and a pressure between 0.1 and 1.0 MPa in the presence of a catalyst, and adjusts the feed flow rate such that the ethanol / acetaldehyde molar ratio at the inlet of the reaction section is between 1 and 5, and a separation section that enables the effluent of the reaction section to be separated at least into a gaseous effluent and a liquid effluent; b3) A step of treating hydrogen, which at least includes a compression section that compresses the hydrogen effluent obtained from step b1) to a pressure between 0.1 MPa and 1.0 MPa, and a gas / liquid washing section that is fed at a temperature between 15°C and -30°C with a portion of the rich ethanol effluent obtained from step b5) and a portion of the ethanol / acetaldehyde effluent obtained from step b1) and at a temperature between 25°C and 60°C with the compressed hydrogen effluent, and at least produces a liquid rich ethanol effluent and a purified hydrogen effluent; b4) A step of extracting butadiene, which at least includes a compression section for compressing the gaseous effluent obtained from step b2) to a pressure between 0.1 MPa and 1.0 MPa, a gas / liquid washing section including a washing tower, the washing tower being fed at the top with an ethanol stream composed of the ethanol raw material from the process and / or a part of the ethanol effluent obtained from step b5) at a temperature between 20°C and -20°C, and being fed at the bottom with the cooled gaseous effluent obtained from step b2), and a distillation section operating at a pressure between 0.1 MPa and 1 MPa, the distillation section being fed at least with the liquid effluent obtained from step b2) and the liquid effluent from the gas / liquid washing 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 butadiene purification step, which at least includes a gas / liquid washing section, which is fed at the bottom with the crude butadiene effluent obtained from b4) and at the top with a water stream, the water stream can be a water stream external to the butadiene production process and / or a part of the water effluent obtained from step b5), and the washing section produces a pre-purified butadiene effluent at the top and a wastewater effluent at the bottom; b4”) A subsequent butadiene purification step, which is fed at least with the pre-purified butadiene effluent obtained from step b4’) and produces at least a purified butadiene effluent; b5) A step of treating the effluent, which is fed at least with the water / ethanol / acetaldehyde raffinate obtained from step b5’) and produces at least a rich ethanol effluent, a rich acetaldehyde effluent, and a rich water effluent; b5') A step of removing impurities and brown oil, which is fed at least with the ethanol / acetaldehyde / water effluent obtained from step b4) and the rich water effluent obtained from step b5) and produces at least a water / ethanol / acetaldehyde raffinate, a light brown oil effluent, and a heavy brown oil effluent; b6) A step of washing with water, which is fed with the gaseous by-product effluent obtained from step b4) and also with a part of the rich water effluent obtained from step b5) and produces at least one alcohol-water effluent.

6. The method according to any one of claims 1 to 5, wherein step c) includes the following sub-steps: c1) A step of C-C coupling between two CO2 molecules and one 1,3-butadiene molecule; c2) A step of separating out adipic acid; c3) A step of reducing the adipic acid formed in step c1) to obtain adipic acid.

7. The method according to claim 6, wherein 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 diazine ligand; - The reducing agent is a metal selected from zinc or manganese; - The solvent is a polar aprotic solvent.

8. The method according to any one of claims 6 and 7, wherein sub-step c1) is carried out at a temperature between 5°C and 70°C.

9. The method as claimed in claim 6, wherein sub-step c3) is carried out in the presence of a catalyst and a reducing agent, the catalyst being palladium supported on activated carbon, and the reducing agent being the purified hydrogen derived from sub-step b3).

10. The method according to any one of the preceding claims, characterized in that The biomass is lignocellulosic biomass.

11. An apparatus suitable for carrying out the method as claimed in any one of claims 1 to 10, the apparatus comprising: - a first reaction section (2) enabling the production of ethanol (3) and CO2 (4) from biomass (1); - a second reaction section (5) for converting ethanol (3) into 1,3-butadiene (6) and hydrogen (9); and - a third reaction section (7) enabling the production of adipic acid (8) from 1,3-butadiene (6), CO2 (4) and hydrogen (9).

Images