PROCESS FOR PRODUCING BUTENE-1 FROM AN AQUEOUS BUTANOL CHARGE

Abstract

The present invention relates to a process for producing 1-butene from an aqueous feed comprising butanol, the process comprising the following steps: a) a butanol separation step comprising treatment of the aqueous feed, and obtaining an effluent comprising essentially butanol; b) a dewatering step comprising treatment of the effluent obtained in step a) in the presence of a dewatering catalyst and obtaining an aqueous dewatering effluent comprising 1-butene and butanol; c) a separation step of the aqueous dewatering effluent obtained in step b) and obtaining a first liquid phase comprising butanol and 1-butene, and a second liquid phase comprising essentially water; d) a recycling step of the second liquid phase comprising essentially water obtained in step c) to step a). Figure 1 to be published

Description

Title of the invention: METHOD FOR PRODUCING BUTENE-1 FROM OF AN AQUEOUS PACK OF BUTANOL technical field

[0001] The present invention relates to the field of butanol dehydration for the production of butene-1 from an aqueous feed comprising said butanol, the feed being able to come from upstream processes such as a fermentation process of type ABE (Acetone / Butanol / Ethanol) or of type IBE (Isopropanol / Butanol / Ethanol) or of type IBEA (Isopropanol / Butanol / Ethanol / Acetone). Previous technique

[0002] In order to meet the challenges of the energy transition, much research is being carried out to develop so-called "green" processes, allowing access to chemical intermediates in an alternative way to oil refining and / or petrochemicals.

[0003] The dehydration of C4 monoalcohols has been studied for many years, primarily as a means of valorizing alcohols produced by fermentation. Catalysts based on mineral acids, FeCl2 salts, metal oxides such as alumina, or zeolite have been used for this application. Document WO2011154621 discloses a process for producing butenes from a butanol feedstock, said process employing an amorphous catalyst and the butanol potentially originating from a biological process such as acetonobutyl fermentation of glucose.

[0004] Fermentation processes such as ABE (Acetone-Butanol-Ethanol) fermentation, carried out by microorganisms belonging to the genus Clostridium, is one of the oldest fermentations to have been industrialized and has since been extensively studied. More recently, IBE (Isopropanol-Butanol-Ethanol) fermentation, which produces a mixture of isopropanol, butanol, and ethanol and is also carried out by microorganisms belonging to the genus Clostridium, has been the subject of fairly recent studies (Dos Santos Vieira et al. Bioresour Technol; 2019 287:121425. doi: 10.1016 / j.biortech.2019.121425 Acetone-free biobutanol production: Past and recent advances in the Isopropanol-Butanol-Ethanol (IBE) fermentation).The different alcohols in the mixture are then extracted by different separation methods such as distillation, for example document WO2022200039 discloses a process for extracting alcohols from a mixture comprising alcohols in aqueous phase obtained from an IBE type fermentation process or . IBEA. Earlier, patent FR2549043B1 proposed an optimized fractionation system by distillation of an aqueous solution of n-butanol and acetone. Membrane processes are also being studied, either on the effluent or coupled with the fermentation step; for example, pervaporation appears promising (J. Serna-Vazquez et al.; Separation and Purification Technology 279 (2021) 119653; https: / / doi.org / 10.1016 / j.seppur.202L119653. Simultaneous production and extraction of bio-chemicals produced from fermentations via pervaporation).

[0005] A process for dehydrating butanol to 1-butene generally comprises a butanol dehydration step in a reaction section to obtain an effluent consisting mainly of 1-butene and water, but also of unreacted butanol and reaction by-products such as dibutyl ether (DBE) and unwanted butene isomers (2-butene CIS and 2-butene TRANS). This dehydration step is then followed by a separation step to obtain a hydrocarbon phase comprising butanol, DBE, 1-butene, 2-butene CIS, and 2-butene TRANS, and an aqueous phase consisting essentially of water and butanol. Due to the physical properties of the effluent, this separation is generally based on the principle of sedimentation, which allows for the straightforward separation of the organic (or hydrocarbon) phase from the aqueous phase.The hydrocarbon phase is then sent to a separation stage to obtain a high-purity butene-1 stream, while the aqueous phase is sent either directly to a wastewater treatment plant before discharge, or advantageously to another separation stage to separate the butanol from the water, the water then being sent to a wastewater treatment plant before discharge. The butanol that did not react during the dehydration process can thus be recycled upstream of the conversion reactor.

[0006] By coupling a butanol dehydration process with a process for separating butanol present in an aqueous feed, said feed preferably coming from an alcoholic extraction step of a mixture of alcohols obtained by a fermentation process, the applicant has surprisingly demonstrated that recycling the aqueous phase comprising butanol and water obtained during the steps of separating the butanol dehydration effluent to the step of separating butanol from the aqueous feed, makes it possible to avoid a separation step which produces in particular waste (wastewater) and makes it possible to obtain an overall energy gain or a gain in butene-1 yield compared to prior art processes. Summary of the invention

[0007] The present invention relates to a process for producing butene-1 from an aqueous feed comprising butanol, the process comprising the following steps:

[0008] a) a butanol separation step comprising the treatment of the aqueous load, and obtaining an effluent comprising essentially butanol;

[0009] b) a dehydration step comprising the treatment of the effluent obtained in step a) in the presence of a dehydration catalyst and the obtaining of an aqueous dehydration effluent comprising butene-1 and butanol;

[0010] c) a step of separating the aqueous dehydration effluent obtained in step b) and obtaining a first liquid phase comprising butanol and butene-1, and a second liquid phase comprising essentially water;

[0011] d) a recycling step of the second liquid phase comprising essentially water obtained in step c) back to step a).

[0012] Optionally, the invention may also include:

[0013] e) a step of separating the first liquid phase obtained in step c) and obtaining an effluent comprising a butene-1 content greater than 80% by weight, preferably greater than 85% by weight, preferably greater than 90% by weight, and an effluent comprising butanol at a content greater than 30%, preferably greater than 35%, preferably greater than 40% by weight;

[0014] f) a step of recycling the effluent comprising butanol at a content greater than 30%, preferably greater than 35%, preferably greater than 40% by weight, obtained in step e) to step b). DETAILED DESCRIPTION OF THE INVENTION

[0015] According to the present invention, the expressions "between ... and ..." and "between ... and ..." are equivalent and mean that the limit values ​​of the interval are included in the range of values ​​described. If this is not the case and the limit values ​​are not included in the range described, such clarification will be provided by the present invention.

[0016] In the sense of the present invention, the different parameter ranges for a given step, such as pressure ranges and temperature ranges, can be used alone or in combination. For example, in the sense of the present invention, a preferred range of pressure values ​​can be combined with a more preferred range of temperature values.

[0017] In this application, pressure values ​​are given in absolute total pressure.

[0018] In this application, particular embodiments of the invention may be described. They may be implemented separately or in combination with each other, without limitation of combinations where technically feasible.

[0019] In this application, the term "include" is synonymous with (means the same as) "include" and "contain", and is inclusive or open and does not exclude other elements not listed. It is understood that the term "include" includes the exclusive and closed term "consist".

[0020] The term "essentially comprising" means a content of at least 90% by weight, preferably at least 92% by weight, preferably at least 93% by weight of the desired compound. Charge

[0021] The present invention relates to a process for producing butene-1 from an aqueous feed comprising butanol.

[0022] Advantageously, butanol is n-butanol also called 1-butanol.

[0023] Advantageously, the aqueous charge comprises butanol at a content of between 30 and 85% by weight, preferably between 35 and 80% by weight, preferably between 40 and 75% by weight.

[0024] The aqueous charge may further comprise other compounds, in particular alcohols and acids such as isopropanol, ethanol, acetone and carboxylic acids such as acetic and butanoic acid, possibly traces of volatile organic compounds (such as, for example, furfural, ethyl formate, ethyl acetate, 2-Methyl-l-propanol, 2,5-Dimethylfuran, ethyl propionate, 3-Methyl-1-butanol, 2-Methyl-l-butanol, isobutyl acetate, 2-Furanmethanol, 3-methyl-l-butanol acetate, acetonitrile, furan, methyl acetate, ...)

[0025] Advantageously, the aqueous feedstock is obtained after one or more separation steps from an aqueous mixture comprising butanol. Advantageously, this aqueous mixture further comprises ethanol and / or isopropanol and / or acetone. The aqueous mixture is advantageously obtained from a sugar fermentation process carried out by a solvent-producing strain of microorganisms, preferably selected from bacteria, particularly of the genus Clostridium (such as C. tyrobutyricum or C. cellulovorans, C. acetobutylicum, C. beijerinckii), Escherichia coli, yeasts, particularly of the Saccharomyces cerevisiae type, alone or in mixtures.

[0026] Advantageously, the solventogenic microorganism strain is a bacterial strain of the genus Clostridium, preferably the bacterial strain is of the genus Clostridium genetically modified.

[0027] Step a) of separating butanol from the aqueous charge The process according to the invention comprises a) a butanol separation step including the treatment of the aqueous feedstock, and obtaining an effluent comprising essentially butanol.

[0028] This step can be carried out by any separation method known to those skilled in the art, for example by distillation, membrane separation, decantation, solvent extraction. These separation methods can be combined to optimize, in particular, the energy expenditure associated with step a).

[0029] Advantageously, the butanol separation step is carried out in a temperature range between 70° and 180°C, preferably between 80°C and 150°C, even more preferably between 85°C and 135°C.

[0030] Advantageously, step a) allows recovery of more than 90% by weight of butanol from the aqueous feed, more preferably of more than 95% by weight, and even more preferably of more than 98% by weight.

[0031] Advantageously, the energy consumption associated with the separation step is between 1 and 5 MJ / kg of recovered butanol, more preferably less than 4 MJ / kg of recovered butanol. The energy is supplied to the separation system, for example, in the form of heat, from the latent heat of a vapor stream, and / or by the consumption of electricity.

[0032] Preferably, step a) includes at least one distillation step.

[0033] Advantageously, the separation is carried out by a heteroazeotropic distillation system. Heteroazeotropic distillation can be conducted, for example, in a system comprising a first column, called the water column, which recovers the water, a second column, called the butanol column, which recovers the butanol, and a decanter. Advantageously, the first column, called the water column, operates at a head pressure substantially equal to atmospheric pressure or slightly lower, on the order of 0.08 MPa, or slightly higher, on the order of 0.15 MPa. The bottom temperature of the column is between 93 °C and 120 °C, depending on the chosen head pressure and the pressure losses in the column. The top temperature of the column is between 90 °C and 110 °C, depending on the chosen operating pressure. The water column has a theoretical number of plates between 5 and 15.

[0034] The second column, known as the butanol column, operates at a head pressure substantially equal to atmospheric pressure or slightly lower, on the order of 0.08 MPa, or slightly higher, on the order of 0.15 MPa. The bottom temperature of the column is between 115 °C and 140 °C, depending on the chosen head pressure and the pressure losses in the column. The top temperature of the column is between 90 °C and 110 °C, depending on the chosen operating pressure. The butanol column has a theoretical number of plates between 5 and 15.

[0035] The decanter is preferably operated between 40°C and 110°C, it is advantageously placed on the flow or flows from the column heads to take advantage of the thermodynamic properties of the water-butanol mixture well known to those skilled in the art.

[0036] The hetero-azeotropic distillation system may further include a common upstream condenser for both columns, optionally with a reflux flask downstream of the condenser. The temperature of this condenser is between 40 °C and 110 °C, depending on the operating pressure selected. The distillation system hetero-azeotropic may further include a reboiler at the bottom of each column to heat the bottom-of-column flow; these reboilers may be chosen from vertical thermosiphon reboilers, kettle reboilers, furnace reboilers, and once-through reboilers.

[0037] Step b) of dehydration The process according to the invention includes a dehydration step comprising the treatment of the effluent obtained in step a) in the presence of a dehydration catalyst and the obtaining of an aqueous dehydration effluent comprising butene-1 and butanol.

[0038] The dehydration catalyst can be chosen from all catalysts known to those skilled in the art that are suitable for catalyzing the dehydration reaction of butanol to butene-1.

[0039] Advantageously, the dehydration catalyst is chosen from formulations that have or have not undergone various treatments so as to preferentially generate Lewis or Brønsted acidic sites. Among these suitable formulations are catalysts based on amorphous or crystalline oxides such as alumina, silica-alumina or zeolite, or systems doped with a chemical element, for example phosphorus or tungsten, generating a suitable acidity.

[0040] Preferably, the chosen dehydration catalyst is capable of producing DBE (di-butyl ether) as a reaction intermediate, and is capable of converting DBE into butene-1.

[0041] Advantageously, the dehydration step is carried out at a temperature between 200 and 500 °C, preferably between 250°C and 500°C, preferably between 250°C and 400°C.

[0042] Advantageously, the dehydration step is carried out at a pressure between 0.1 and 4 MPa, preferably between 0.1 and 2 MPa, preferably between 0.2 and 2 MPa.

[0043] Advantageously, the conversion of butanol is greater than 30%, preferably greater than 60% and preferably greater than 80%.

[0044] Advantageously, the aqueous dehydration effluent comprises among the carbonaceous species butene-1 at a content of at least 10% by weight, preferably at least 25% by weight, preferably at least 50% by weight.

[0045] In one embodiment, when optional steps e) and f) are implemented, the feed processed in dehydration step b) further comprises DBE, a partial dehydration product of butanol. The butanol / DBE mass ratio can be between 0.2 and 20, preferably between 0.5 and 20, and more preferably between 0.5 and 10. In this embodiment, a maximum butene-1 yield is achieved. is specifically targeted. In this embodiment, the per-pass conversion of butanol is greater than 20%, preferably greater than 35%, and preferably greater than 50%. In this embodiment, the aqueous dewatering effluent further comprises butene-2CIS and / or butene-2TRANS. The content of butene-2CIS and / or butene-2TRANS among the butenes is less than 30% by weight, preferably 20% by weight, and preferably 10% by weight.

[0046] Step c) of separating the dewatering effluent The process according to the invention includes a step c) of separating the dehydration effluent obtained in step b) and obtaining a first liquid phase comprising butanol and butene-1, and a second liquid phase comprising essentially water.

[0047] Advantageously, the dewatering effluent separation step is carried out at a temperature below 100°C, preferably at a temperature between 30 and 60 °C, preferably between 33 and 55, even more preferably between 35 and 50 °C.

[0048] Advantageously, the dewatering effluent separation step is carried out at a pressure less than 1 MPa, preferably between 0.2 and 0.6 MPa, preferably between 0.25 and 0.55 MPa, preferably between 0.3 and 0.5 MPa.

[0049] This step can be carried out by all means of separation known to a person skilled in the art, for example, by way of non-limiting example, decantation, membrane separation or solvent extraction may be mentioned.

[0050] Advantageously, this step includes at least one unit for carrying out liquid-liquid decantation.

[0051] Advantageously, this step is carried out in a separator flask also called a flash flask or decanter flask.

[0052] Advantageously, this separation step allows recovery in the first liquid phase of more than 80% by weight of the butene-1 present in the dehydration effluent obtained in step b), more preferably more than 90% by weight, even more preferably more than 98% by weight.

[0053] Advantageously, the first liquid phase comprises butene-1 at a content of between 20 and 80% by weight, preferably between 25 and 75% by weight, preferably between 30 and 70% by weight.

[0054] Advantageously, the first liquid phase comprises butanol at a content of between 5 and 45% by weight, preferably between 10 and 40% by weight, preferably between 15 and 35% by weight.

[0055] In one embodiment, the first liquid phase further comprises DBE. The DBE content may be between 1 and 50% by weight, preferably between 3 and 45% by weight, preferably between 4 and 40% by weight.

[0056] In one embodiment, the first liquid phase further comprises butene-2CIS and / or butene-2TRANS. The content of butene-2CIS and / or butene-2TRANS may be between 0.05 and 2 wt%, preferably between 0.07 and 1.5 wt%, preferably between 0.1 and 1 wt%.

[0057] In one embodiment, the second liquid phase further comprises butanol at a content less than or equal to 10% by weight, preferably less than or equal to 8% by weight, preferably less than or equal to 7% by weight.

[0058] Step d) of recycling the second liquid phase from step c) to step a) The process according to the invention includes a step d) of recycling the second liquid phase comprising essentially water obtained in step c) to step a).

[0059] The recycling rate of the second liquid phase consisting essentially of water obtained in step c) to step a) is advantageously between 0.1 and 0.5 kg of recycle / kg of butanol present in the effluent obtained in step a).

[0060] Optional step e) of separating the first liquid phase The process according to the invention may further comprise a step e) of separating the first liquid phase obtained in step c) and obtaining an effluent comprising a butene-1 content greater than 80% by weight, preferably greater than 85% by weight, preferably greater than 90% by weight, and an effluent comprising butanol at a content greater than 30%, preferably greater than 35%, preferably greater than 37% by weight.

[0061] This step can be carried out by all means of separation known to those skilled in the art, for example by distillation, membrane separation, solvent extraction.

[0062] Advantageously, this separation step allows recovery in the effluent comprising a butene-1 content greater than 80% by weight, preferably greater than 85% by weight, preferably greater than 90% by weight, of more than 80% by weight of the butene-1 present in the first liquid phase obtained in step c), more preferably more than 90% by weight, even more preferably more than 97% by weight.

[0063] Advantageously, this step comprises at least one distillation step carried out in a distillation column. This column advantageously operates with a head pressure between 0.3 and 1 MPa, preferably between 0.4 and 0.8 MPa, and more preferably between 0.45 and 0.75 MPa. The bottom temperature of this column is between 150 and 190 °C, preferably between 155 °C and 180 °C, and more preferably between 160 °C and 175 °C. The number of theoretical plates is less than 70 plates, preferably 65 plates, and more preferably 60 theoretical plates.

[0064] In one embodiment, the effluent comprising a butene-1 content greater than 80% by weight, preferably greater than 85% by weight, preferably greater than 90% by weight, may further comprise water and / or butene-2CIS and / or butene-2TRANS with a content less than or equal to 11% by weight, preferably less than or equal to 10% by weight, preferably less than or equal to 9% by weight.

[0065] In one embodiment, the effluent comprising butanol at a content greater than 30%, preferably greater than 35%, preferably greater than 37% by weight, may further comprise DBE and / or water and / or butene-1 and / or butene-2CIS and / or butene-2TRANS at a content of less than 70% by weight, preferably at a content of less than 65% by weight, preferably at a content of less than 63% by weight.

[0066] Optional step f) of recycling the effluent obtained in step e) back to step b) The process according to the invention may further include a step f) of recycling the effluent comprising butanol at a content greater than 30%, preferably greater than 35%, preferably greater than 37% by weight, obtained in step e) to step b).

[0067] The recycling rate is advantageously between 0.5 and 1.5 kg of recycle / kg of butanol present in the effluent obtained in step a).

[0068] This recycle then makes it possible to valorize DBE (di-butyl-ether), an intermediate product of the dehydration reaction of butanol into butene-1. DESCRIPTION OF THE FIGURES

[0069] [Fig. 1]: Process for producing butene-1 from an aqueous feed comprising butanol according to the invention:

[0070] An aqueous feed comprising butanol 1 is sent to a separation step a) to obtain an effluent 2 comprising essentially butanol. The effluent 2 is sent to a dewatering step b) to obtain an aqueous dewatering effluent 3 comprising butene-1 and butanol. The effluent 3 is sent to a separation step c) to obtain a first liquid phase 5 comprising butanol and butene-1 and a second liquid phase 4 comprising essentially water. The second liquid phase 4 is recycled d) to step a).

[0071] [Fig.2]: Process for producing butene-1 from an aqueous feed comprising butanol according to an embodiment of the invention:

[0072] An aqueous feed comprising butanol 1 is sent to a separation step a) to obtain an effluent 2 comprising essentially butanol. The effluent 2 is sent to a dewatering step b) to obtain an aqueous dewatering effluent 3 comprising butene-1 and butanol. The effluent 3 is sent to a separation step c) to obtain a first liquid phase 5 comprising butanol and butene-1 and a second liquid phase 4 comprising essentially water. The second liquid phase 4 is recycled d) to step a), and the first liquid phase 5 is sent to a separation step e) to obtain an effluent 6 comprising a butene-1 content greater than 80% by weight, preferably greater than 85% by weight, preferably greater than 90% by weight, and an effluent 7 comprising butanol at a content greater than 30%, preferably greater than 35%, preferably greater than 40% by weight. Effluent 7 is recycled f) to step b). EXAMPLES

[0073] Example 1: Process for dehydrating n-butanol to 1-butene from a aqueous charge of n-butanol according to the prior art, not in accordance with the invention

[0074] The process uses an aqueous n-butanol feedstock obtained after several separation steps from an aqueous mixture comprising butanol, ethanol, and acetone, resulting from a sugar fermentation process carried out by a strain of Clostridium bacteria. The feedstock composition is 44% by weight n-butanol and 56% by weight water. The process processes 7500 kg / h of feedstock.

[0075] 1) Separation of n-butanol from the charge

[0076] This feedstock is sent to a heteroazeotropic distillation system comprising two columns, a common condenser at the top of both columns, a reflux flask downstream of the condenser, and a reboiler at the bottom of each column. At the bottom of the first column, referred to as the water column, a stream of water is obtained, and at the bottom of the second column, referred to as the butanol column, a stream of n-butanol with a purity of 99.5% wt. Both columns operate at a pressure of 0.14 MPa at the column head. The two columns have 8 and 8 theoretical plates, respectively.

[0077] In terms of energy consumption, the water column consumes 0.53 MJ / kg of n-butanol of heat in the form of reboiling steam; this heat is required at a thermal level of approximately 109.3°C at the operating pressure considered. The butanol column consumes 1.94 MJ / kg of n-butanol of heat in the form of reboiling steam; this heat is required at a thermal level of approximately 127.1°C at the operating pressure considered.

[0078] 2) Dehydration of n-butanol

[0079] The n-butanol stream obtained in step 1) is sent to a conversion reactor operating isothermally at 325°C, and at a pressure of 0.15 MPa, the reaction being endothermic, a heat input is made.

[0080] The dehydration catalyst used is gamma alumina.

[0081] The hourly weight velocity expressed as the mass flow rate of n-butanol entering the conversion reactor (in kg / h) / mass of catalyst in the conversion reactor (in kg) is 7 h1.

[0082] The reaction progresses under these operating conditions are expressed in the table below:

[0083] [Tables 1] Conversion Selectivity of Carbon Compounds Butanol 1-Butene 2-Butenes (CIS and TRANS) dibutyl ether other 82% 83% 9% 7% 1%

[0084] The yield per pass corresponding to the number of moles of butene-1 in the aqueous dehydration effluent / number of moles of n-butanol of the feed at the reactor inlet is equal to 0.68.

[0085] The output composition of the dehydration reactor in step 2) is:

[0086] [Tables2] 1-Butene 1698.44 kg / h n-butanol 594.00 kg / h Water 659.70 kg / h 2-Butenes 184.17 kg / h DBE 143.24 kg / h others 20.46 kg / h

[0087] 3) Steps for separating the dewatering effluent

[0088] The aqueous effluent from the reactor obtained in step 2) is sent to a flash balloon operating at 40 °C and 0.372 MPa. A phase separation between two liquids is carried out in this balloon: • First, a hydrocarbon phase is recovered, with a yield of 0.79 kg / kg of incoming n-butanol and the following composition: butene-1: 65.0 wt%, n-butanol: 21.7 wt%, DBE: 5.5 wt%, butenes-2: 7.0 wt%, and other carbon compounds: 0.8 wt% • Secondly, an aqueous phase is recovered, it has a flow rate of 0.21 kg / kg of n-butanol entering the conversion reactor and has the following composition: H2O: 95.8% by weight, n-butanol: 4.2% by weight.

[0089] The prior art process thus made it possible to produce 1698.44 kg / h of butene-1 from 3300 kg / h of n-butanol. The energy consumption of step a) is 2.47 MJ / kg of n-butanol, which corresponds to 4.79 MJ / kg of butene-1 produced.

[0090] Example 2: Process for dehydrating n-butanol to 1-butene from an aqueous n-butanol feedstock according to a first embodiment of the invention

[0091] The process described in this example treats the same load as Example 1, namely 7500 kg / h of an aqueous mixture composed of 44% wt. n-butanol and 56% wt. water.

[0092] According to this embodiment of the invention, the feed treated by step a) of separating n-butanol from the aqueous feed also treats the effluent from the separation step subsequent to the dehydration step of n-butanol into butene-1.

[0093] 1) Separation of n-butanol from the charge

[0094] The overall flow processed by this step is 3328.9 kg / h of n-butanol and 4662.6 kg / h of water. Indeed, the total load of this step includes the primary flow of butanol + water from the upstream process (namely 7500 kg / h with 44 / 56 butanol / water) + the recycled aqueous phase from step 3).

[0095] The results below are expressed in relation to the n-butanol entering step 1) excluding recycle from step 3) (i.e. 3300 kg / h of n-butanol).

[0096] The feedstock is sent to a heteroazeotropic distillation system similar to that of Example 1, i.e., comprising two columns, a common condenser at the top of both columns, a reflux flask downstream of the condenser, and a reboiler at the bottom of each column. The recycle from step d) is injected at the common condenser. At the bottom of the first column, referred to as the water column, a stream of water is obtained, and at the bottom of the second column, referred to as the butanol column, a stream of n-butanol with a purity of 99.5 wt% is obtained. Both columns operate at a pressure of 0.136 MPa at the column top. The two columns have 8 and 8 theoretical plates, respectively.

[0097] In terms of energy consumption, the water column consumes 0.60 MJ / kg of n-butanol of heat in the form of reboiling steam; this heat is required at a thermal level of approximately 109.3 °C at the operating pressure considered. The butanol column consumes 1.90 MJ / kg of n-butanol of heat in the form of reboiling steam; this heat is required at a thermal level of approximately 127.1 °C at the operating pressure considered. The total energy consumption is therefore 2.72 MJ / kg n-butanol.

[0098] Step 2) of n-butanol dehydration

[0099] The n-butanol stream obtained in step 1) is sent to a conversion reactor operating under the same conditions as that of Example 1, i.e. isothermally at 325°C, and at a pressure of 0.15 MPa, the reaction being endothermic, a heat input is made.

[0100] The dehydration catalyst used is gamma alumina.

[0101] The hourly weight velocity expressed as the mass flow rate of n-butanol entering the conversion reactor (in kg / h) / mass of catalyst in the conversion reactor (in kg) is 7 h1.

[0102] The reaction progresses under these operating conditions are expressed in the table below:

[0103] [Tables3] Conversion Selectivity of carbon compounds Butanol 1-Butene 2-Butenes dibutyl ether other 82% 83% 9% 7% 1%

[0104] The yield per pass corresponding to the number of moles of butene-1 in the aqueous dehydration effluent / number of moles of n-butanol of the feed at the reactor inlet is equal to 0.68.

[0105] The output composition of the dehydration reactor in step 2) is:

[0106] [Tables4] 1-Butene 1712.65 kg / h n-butanol 599.0 kg / h Water 668.7 kg / h 2-Butenes 185.7 kg / h DBE 144.44 kg / h others 20.63 kg / h

[0107] 3) Dewatering effluent separation step

[0108] The aqueous effluent from the reactor obtained in step 2) is sent to a flash balloon operating at 40 °C and 0.372 MPa. A phase separation between two liquids is carried out in this balloon: • First, a hydrocarbon phase is recovered, with a flow rate of 0.80 kg / kg of n-butanol entering step 1 excluding recycling (i.e., 3300 kg / h of n-butanol), and the following composition: butene-1: 64.9% wt., n-butanol: 21.6% wt., DBE: 5.5% wt., butenes-2: 7.0% wt., other: 1.0% wt. • Secondly, an aqueous phase is recovered, it has a flow rate of 0.21 kg / kg of n-butanol entering step 1 outside of recycle (i.e. 3300 kg / h of n-butanol), with the following composition: H2O: 95.8% by weight, n-butanol: 4.2% by weight.

[0109] 4) Recycling step of the aqueous phase from step 3) back to step 1)

[0110] As explained, the aqueous phase from step 3) is recycled to step 1), which leads to treating in step 1) a flow of 8192.0 kg / h of an n-butanol-water mixture composed of 40.1% wt of n-butanol and 59.9% wt of water.

[0111] The process according to the invention thus made it possible to produce 1712.65 kg / h of butene-1 from 3300 kg / h of n-butanol as input. The energy consumption of step 1) corresponds to 4.81 MJ / kg of butene-1 produced.

[0112] The process according to the invention in this first embodiment has therefore made it possible to increase the yield of butene-1 produced from 51.4% by weight to 51.9% by weight, i.e. 0.4 points of yield, with a substantially equivalent specific energy consumption.

[0113] Example 3: Process for dehydrating n-butanol to 1-butene from an aqueous feed of n-butanol with recycling according to the prior art not in accordance with the invention

[0114] The process uses an aqueous n-butanol feed obtained after several separation steps from an aqueous mixture comprising butanol, ethanol, isopropanol and acetone from a sugar fermentation process carried out by a strain of bacteria of the genus Clostridium.

[0115] The composition of the charge is as follows: 63% by weight of n-butanol, 36% by weight of water, and 1% by weight of other carbon compounds.

[0116] 1) Separation of n-butanol from the charge

[0117] This feedstock is sent to a heteroazeotropic distillation system comprising two columns, a common condenser at the top of both columns, a reflux flask downstream of the condenser, and a reboiler at the bottom of each column. At the bottom of the first column, referred to as the water column, a stream of water is obtained, and at the bottom of the second column, referred to as the butanol column, a stream of n-butanol with a purity of 99.2 wt% is obtained. Both columns operate at a pressure of 0.116 MPa. The two columns have 8 and 8 theoretical plates, respectively.

[0118] In terms of energy consumption, the water column consumes 0.22 MJ / kg of n-butanol of heat in the form of reboiling steam; this heat is required at a thermal level of approximately 104.8 °C at the considered operating pressure. The butanol column consumes 1.70 MJ / kg of n-butanol of heat in the form of reboiling steam; this heat is required at a thermal level of approximately 123.1 °C at the considered operating pressure.

[0119] 2) Dehydration of n-butanol

[0120] Operation with recycling

[0121] In this example, the n-butanol stream obtained in step 1) is supplemented by the recycling stream including unconverted butanol and dibutyl ether from the residue of the HC column in step 3b). The whole is sent to a conversion reactor operating isothermally at 283°C, and at a pressure of 0.15 MPa, the reaction being endothermic, a heat input is made.

[0122] The dehydration catalyst used is the same alumina as that used for Example 1.

[0123] After equilibration, the hourly weight rate expressed as the mass flow rate of n-butanol and dibutyl ether entering the conversion reactor (in kg / h) / mass of catalyst in the conversion reactor (in kg) is fixed at 5 h 1 and the mass ratio butanol / DBE at reactor inlet is under these conditions 2.3.

[0124] The results of the catalytic tests are expressed in the table below:

[0125] [Tables5] Pass conversion Selectivity of carbon compounds Butanol dibutyl ether Charge 1-Butene 2-Butenes other 69% 0% 48% 93% 6% 1%

[0126] The yield per pass corresponding to the number of moles of butene-1 in the aqueous dehydration effluent / number of moles of n-butanol and dibutyl ether of the feed at the reactor inlet is 0.45. It is lower than in the case without recycle due to a lower conversion per pass but the final yield with recycle (0.93) is much higher.

[0127] 3) Steps for separating the dewatering effluent

[0128] a) The aqueous effluent from the reactor obtained in step 2) is sent to a flash balloon operating at 40 °C and 0.293 MPa. Phase separation between two liquids is carried out in this balloon: • Firstly, a so-called hydrocarbon phase is recovered; it has a flow rate of 1.72 kg / kg of n-butanol entering step 1 and has the following composition: butene-1: 35.2% by weight, n-butanol: 24.9% by weight, DBE: 36.4% by weight, butenes-2: 2.3% by weight, other carbon compounds: 0.9% by weight. • Secondly, an aqueous phase is recovered, it has a flow rate of 0.35 kg / kg of n-butanol entering step 1 and has the following composition: H2O: 95.8% wt, n-butanol: 4.2% wt.

[0129] b) The recovered hydrocarbon phase is sent to a distillation column (here referred to as column HC) comprising 46 theoretical plates, a condenser, and a reboiler. It operates at a head pressure of 0.66 MPa and has an overall pressure drop of 0.04 MPa. The condenser temperature is 45.7°C. The column yields, on the one hand, the desired product, butene-1, in the distillate. The flow rate of this effluent is 0.64 kg / kg of n-butanol entering step 1), and its composition is as follows: butene-1: 94.4 wt%, H2O: 0.6 wt%, butenes-2: 4.1 wt%. On the other hand, a residue, which is an effluent, is obtained at the bottom of the column. comprising unreacted n-butanol from the reactor and the intermediate product DBE, the flow rate of this effluent is 1.08 kg / kg of n-butanol entering step 1) and its composition is as follows: n-butanol: 39.9 wt%, DBE: 58.1 wt%, H₂O: 0.9 wt%, butenes-2: 1.1 wt%. This column consumes 2.78 MJ / kg of n-butanol of heat in the form of reboiling steam; this heat is required at a thermal level of approximately 178°C at the operating pressure considered.

[0130] c) The recovered aqueous phase is sent to a distillation column (here referred to as the water column) comprising four theoretical stages, a condenser, and a reboiler. It operates at a head pressure of 0.85 MPa and has a pressure drop of 0.03 MPa per theoretical stage. The condenser temperature is 145.4 °C. The column allows the unreacted n-butanol from the conversion reactor to be recovered in the distillate. The flow rate of this effluent is 0.025 kg / kg of n-butanol entering step 1, and its composition is as follows: n-butanol: 55.5 wt., H₂O: 43.5 wt., other carbon compounds: 1 wt. A residue, which is water formed during the reaction in the conversion reactor, is obtained at the bottom of the column.This water stream is sent to the wastewater treatment plant before discharge; its flow rate is 0.33 kg / kg of n-butanol entering the dehydration process (in step 1), and its composition is as follows: H2O: 99.8% wt., and n-butanol: 0.2% wt. This column consumes 0.50 MJ / kg of n-butanol of heat in the form of reboiling steam; this heat is required at a thermal level of approximately 178.2 °C at the considered operating pressure.

[0131] 4) Recycling steps

[0132] The unreacted n-butanol from the dehydration process, contained in the residue from the HC column obtained in step 3b) and in the distillate from the water column in step 3c), is recycled upstream of the conversion reactor. To do this, the two streams are mixed and sent upstream of this reactor. The flow rate of this recycle is 1.069 kg / kg of n-butanol exiting the bottom of the butanol column in step a), and its composition is as follows: n-butanol: 40.2 wt%, H2O: 1.9 wt%, DBE: 56.8 wt%, 2-butenes: 1.1 wt%

[0133] Overall energy balance of the distillation steps:

[0134] [Tableauxô] Stage Energy expenditure for heating (MJ / kg of den-butanol entering stage 1 = 3300 kg / h) 1) Water column 0.22 1) Butanol column 1.70 3) HC column 2.78 3) Water column 0.50 Total 5.20

[0135] In this example we obtain 1993.8 kg / h of butene-1.

[0136] The specific energy consumption is 8.6 MJ / kg of butene-1.

[0137] Example 4: Process for dehydrating n-butanol to 1-butene from an aqueous n-butanol feedstock according to a second embodiment of the invention

[0138] The process exemplified according to the invention treats the same feed as that of Example 3, i.e., a feed composed of 63 wt% n-butanol, 36 wt% water, and 1 wt% other carbon compounds. The process is similar to that of Example 3, except that the aqueous phase recovered in step 3a) is not sent to a distillation column but is recycled to the azeotropic water / butanol dehydration system of step 1). In this way, this scheme offers the same performance in terms of yield and selectivity for 1-butene using one less distillation column (the water column of step 3c)).

[0139] According to this embodiment of the invention, the feed treated by step 1) of separating n-butanol from the aqueous feed also treats the effluent from the separation step following the dehydration step of n-butanol into butene-1. Unless otherwise stated, the data expressed in kg of n-butanol refers to the kg of n-butanol of the feed entering step a), namely 3300 kg / h of n-butanol (before recycling).

[0140] 1) Separation of n-butanol from the charge

[0141] The overall flow treated by this step is 1.92 kg of flow / kg of n-butanol, from a flow having an overall composition of 53.0 wt% n-butanol and 47.0 wt%. The results are expressed relative to the n-butanol of the infeed feed to the process (step a)), namely 3300 kg / h of n-butanol (before recycling).

[0142] The feedstock is sent to a heteroazeotropic distillation system similar to that of Example 3, i.e., comprising two columns, a common condenser at the top of both columns, a reflux flask downstream of the condenser, and a reboiler at the bottom of each column. The recycle from step 3a) is injected at the common condenser. At the bottom of the first column, referred to as the water column, a stream of water is obtained, and at the bottom of the second column, referred to as the butanol column, a stream of n-butanol with a purity of 99.5 wt% is obtained. Both columns operate at a pressure of 0.116 MPa at the column top. The two columns have 8 and 8 theoretical plates, respectively.

[0143] In terms of energy consumption, the water column consumes 0.36 MJ / kg of n-butanol of heat in the form of reboiling steam; this heat is required at a thermal level of approximately 104.8°C at the considered operating pressure. butanol column consumes 1.73 MJ / kg of n-butanol of heat in the form of reboiling steam, this heat is required at a thermal level of approximately 123.1 °C at the considered operating pressure.

[0144] 2) Dehydration of n-butanol

[0145] The dehydration of n-butanol is carried out under the same operating conditions as in Example 3. Note that the stream treated by this step differs slightly from Example 3, since only the unreacted n-butanol and the DBE formed during the dehydration process, contained in the residue of the HC column (step 3b) of that example, is recycled upstream of the conversion reactor. The flow rate of this recycle is 1.04 kg / kg of n-butanol entering step 1), i.e., 3300 kg / h of n-butanol, and its composition is as follows: n-butanol: 39.9 wt., H2O: 0.9 wt., DBE: 58.1 wt., butenes-2: 1.1 wt.

[0146] 3) separation step

[0147] The aqueous effluent from the reactor obtained in step 2) is sent to a flash balloon operating at 40 °C and 0.292 MPa. Phase separation between two liquids is carried out in this balloon, leading to the production of a hydrocarbon phase and an aqueous phase • Firstly, a so-called hydrocarbon phase is recovered; it has a flow rate of 1.72 kg / kg of n-butanol entering step 1 and has the following composition: butene-1: 35.2% by weight, n-butanol: 24.9% by weight, DBE: 36.4% by weight, butenes-2: 2.3% by weight, other carbon compounds: 0.9% by weight. • Secondly, an aqueous phase is recovered, with a flow rate of 0.35 kg / kg of n-butanol entering step 1 and the following composition: H2O: 95.8% wt., n-butanol: 4.2% wt.

[0148] a) aqueous phase recycling step

[0149] As explained, the aqueous phase is recycled to step 1), which leads to treating in step 1) a flux of 1.92 kg of flux / kg of n-butanol, of a flux having the overall composition 52.9% by weight of n-butanol and 47.0% by weight of water and 0.1% by weight of other carbon compounds.

[0150] b) hydrocarbon phase separation step

[0151] The hydrocarbon phase is sent from the separation process, which is carried out similarly to step 3b) of Example 3. This stream is then sent to a distillation column (here referred to as column HC) comprising 46 theoretical plates, a condenser, and a reboiler. It operates at a head pressure of 0.66 MPa and has an overall pressure drop of 0.04 MPa. The condenser temperature is 45.7 °C. The column allows the desired product, butene-1, to be obtained in the distillate. The flow rate of this effluent is 0.64 kg / kg of n-butanol entering step 1), and its composition is as follows: butene-1: 94.3 wt., H2O: 0.6 wt., butenes-2: 4.1 wt%. Furthermore, a residue is obtained at the bottom of the column, which is an effluent comprising unreacted n-butanol from the reactor and the intermediate product DBE. The flow rate of this effluent is 1.08 kg / kg of n-butanol entering the reactor, and its composition is as follows: n-butanol: 39.8 wt%, DBE: 58.1 wt%, H₂O: 0.9 wt%, butenes: 2-1.2 wt%. This column consumes 2.78 MJ / kg of n-butanol of heat in the form of reboiling steam. This heat is required at a thermal level of approximately 178°C at the operating pressure considered.

[0152] 4) Recycling steps

[0153] Part of the unreacted n-butanol during the dehydration process is contained in the residue from the HC column obtained in step 3b). The entire bottom of the column is recycled to step 2) of dehydration.

[0154] Overall energy balance of the distillation steps:

[0155] [Tables7] Stage Energy Expenditure (MJ / kg) 1) Water column 0.36 1) Butanol column 1.73 3) HC column 2.78 Total 4.87

[0156] In this example we obtain 1992.5 kg / h of butene-1, which is approximately the same quantity as in example 3.

[0157] The specific energy consumption is 8.0 MJ / kg of butene-1.

[0158] Thus, the process according to the invention in this embodiment makes it possible to eliminate a distillation column, reducing the overall process investment, while presenting an energy demand of (5.2-4.9) / 5.2= 5.8% lower compared to a prior art process.

Claims

Demands

1. A process for producing 1-butene from an aqueous feed comprising butanol, the process comprising the following steps: a) a butanol separation step comprising treatment of the aqueous feed, and obtaining an effluent comprising essentially butanol; b) a dewatering step comprising treatment of the effluent obtained in step a) in the presence of a dewatering catalyst and obtaining an aqueous dewatering effluent comprising 1-butene and butanol; c) a separation step of the aqueous dewatering effluent obtained in step b) and obtaining a first liquid phase comprising butanol and 1-butene, and a second liquid phase comprising essentially water; d) a recycling step of the second liquid phase comprising essentially water obtained in step c) to step a).

2. A method according to claim 1, wherein the aqueous feed is obtained after one or more separation steps from an aqueous mixture comprising butanol.

3. A process according to claim 2, wherein the aqueous mixture further comprises ethanol and / or isopropanol and / or acetone.

4. A process according to any one of claims 2 or 3, wherein the aqueous mixture is advantageously obtained from a sugar fermentation process carried out by a solventogenic strain of microorganisms.

5. A method according to claim 4, wherein the solvent-producing microorganism strain is a bacterial strain of the genus Clostridium.

6. A method according to any one of the preceding claims, wherein step a) of butanol separation is carried out by a hetero-azeotropic distillation system.

7. A process according to any one of the preceding claims, wherein the dehydration catalyst is capable of producing DBE and is capable of converting DBE into butene-1.

8. A process according to claim 7, wherein in step c) the first liquid phase further comprises DBE at a content of between 1 and 50% by weight.

9. A process according to any one of the preceding claims, wherein the recycling rate of the second liquid phase consisting essentially of water obtained in step c) to step a) is between 0.1 and 0.5 kg of recycle / kg of butanol present in the effluent obtained in step a).

10. A process according to any one of the preceding claims, further comprising a step e) of separating the first liquid phase obtained in step c) and obtaining an effluent comprising a butene-1 content greater than 80% by weight, and an effluent comprising butanol at a content greater than 30% by weight.

11. A process according to claim 10, wherein the effluent comprising butanol at a content above 30% by weight further comprises DBE and / or water and / or butene-1 and / or butene-2CIS and / or butene-2TRANS at a content below 70% by weight.

12. A process according to any one of claims 10 or 11, further comprising a step f) of recycling the effluent comprising butanol at a content greater than 30% by weight obtained in step e) to step b).

13. A process according to claim 12, wherein the recycling rate is between 0.5 and 1.5 kg of recycle / kg of butanol present in the effluent obtained in step a).

14. A process according to any one of claims 12 or 13, wherein the feed treated in the dehydration step b) further comprises DBE.

15. A method according to claim 14, wherein the butanol / DBE mass ratio is between 0.2 and 20.

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