PROCESS FOR PRODUCING BUTENE-1 FROM AN AQUEOUS BUTANOL CHARGE

Abstract

The present invention relates to a process for producing 1-butene, the process comprising the following steps: a) a dehydration step comprising the treatment of an aqueous feed comprising butanol, said dehydration step being carried out in the presence of a dehydration catalyst, and obtaining an aqueous dehydration effluent comprising 1-butene and butanol; b) a separation step of the aqueous dehydration effluent obtained in step a) and obtaining a first liquid phase comprising butanol and 1-butene, and a second liquid phase comprising essentially water and butanol; c) a butanol separation step comprising the treatment of the second liquid phase obtained in step b), and obtaining an effluent comprising essentially butanol; d) a recycling step of the effluent comprising essentially butanol 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 undesired 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, allowing 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] It is also well known that water strongly modifies the dehydration kinetics of alcohols (De Mourgues L et al., Kinetics of the catalytic dehydration of 2-propanol J. Catal. 1967, 7, 117-125 DOI: 10.1016 / 0021-9517(67)90049-8; Larmier K et al., Influence of Coadsorbed Water and Alcohol Molecules on Isopropyl Alcohol Dehydration on γ-Alumina: Multiscale Modeling of Experimental Kinetic Profiles ACS Catalysis 2016 6 (3), 1905-1920 DOI: 10.1021 / acscatal.6b00080). Although dehydration in the presence of water is entirely possible, as this molecule is not a reaction poison, its effect on the catalytic process is considered negative, particularly due to the reduction it causes in the catalyst's activity. The paper by Larmier et al. also demonstrated that the reaction selectivity (total dehydration versus partial dehydration) favors ether formation in the presence of water.Beyond the activity itself, water can also impact the recycling loop described above. Water is present in the feedstock, is produced by the reaction, and is also potentially reintroduced via the loop. recycling. Good water flow management is therefore necessary to optimize process performance.

[0007] By coupling a process for dehydrating a feed comprising water and butanol with a step for separating the butanol from the liquid phase comprising essentially water which has been separated from the dehydration effluent, 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 this coupling 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

[0008] The present invention relates to a process for the production of butene-1, the process comprising the following steps:

[0009] a) a dehydration step comprising the treatment of an aqueous feed comprising butanol, said dehydration step being carried out in the presence of a dehydration catalyst, and the obtaining of an aqueous dehydration effluent comprising butene-1 and butanol;

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

[0011] c) a butanol separation step comprising the treatment of the second liquid phase obtained in step b), and obtaining an effluent comprising essentially butanol;

[0012] d) a step of recycling the effluent comprising essentially butanol obtained in step c) back to step a).

[0013] Optionally, the invention may also include:

[0014] e) a step of separating the first liquid phase obtained in step b) 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;

[0015] 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 a). DETAILED DESCRIPTION OF THE INVENTION

[0016] 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 within the range of values ​​described. If this is not the case and the limit values ​​are not included in the range described, such precision will be provided by the present invention.

[0017] 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.

[0018] In this application, pressure values ​​are given in absolute total pressure.

[0019] In this application, particular embodiments of the invention may be described. They may be implemented separately or in combination with each other, without limitation as to the combinations where technically feasible.

[0020] 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 unstated elements. It is understood that the term “include” includes the exclusive and closed term “consist.”

[0021] 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.

[0022] Step a) of dehydration The process according to the invention includes a step a) of dehydration comprising the treatment of an aqueous feed comprising butanol, said dehydration step being carried out in the presence of a dehydration catalyst, and the obtaining of an aqueous dehydration effluent comprising butene-1 and butanol.

[0023] Advantageously, butanol is n-butanol also called 1-butanol.

[0024] Advantageously, the aqueous charge comprises butanol at a content of between 50 and 85% by weight, preferably between 55 and 80% by weight, preferably between 60 and 75% by weight.

[0025] Advantageously, the aqueous charge comprises water at a content of between 15 and 50%, preferably between 20 and 45%, preferably between 25 and 40% by weight.

[0026] 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, ...)

[0027] Advantageously, the aqueous charge is obtained after one or more separation steps from an aqueous mixture comprising butanol. Advantageously, this aqueous mixture also contains 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.

[0028] Advantageously, the solventogenic microorganism strain is a bacterial strain of the genus Clostridium, preferably the bacterial strain is of the genus Clostridium genetically modified.

[0029] 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.

[0030] 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, examples include 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.

[0031] Preferably, the chosen catalyst is capable of producing DBE (di-butyl ether) as a reaction intermediate, and is capable of converting DBE into butene-1.

[0032] 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.

[0033] 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.

[0034] Advantageously, the conversion of butanol is greater than 30%, preferably greater than 60% and preferably greater than 80%.

[0035] 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.

[0036] In one embodiment, when optional steps e) and f) are implemented, the feed processed in dehydration step a) also includes 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.

[0037] Step b) of separating the dewatering effluent The process according to the invention comprises a step b) of separating the dehydration effluent obtained in step a) and obtaining a first liquid phase comprising butanol and butene-1, and a second liquid phase comprising essentially water and comprising butanol.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] Advantageously, this step includes at least one unit for carrying out liquid-liquid decantation.

[0042] Advantageously, this step is carried out in a separator flask also called a flash flask or decanter flask.

[0043] 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.

[0044] 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.

[0045] Advantageously, the first liquid phase comprises butanol at a content of between 5 and 50% by weight, preferably between 10 and 45% by weight, preferably between 15 and 40% by weight.

[0046] In one embodiment, the first liquid phase further comprises DBE. The DBE content may be between 0.5 and 50% by weight, preferably between 1 and 45% by weight, preferably between 1.5 and 40% by weight.

[0047] 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 25% by weight, preferably between 0.1 and 20% by weight, and more preferably between 0.15 and 15% by weight.

[0048] Step c) of butanol separation The process according to the invention includes a step c) of butanol separation comprising the treatment of the second liquid phase obtained in step b), and the obtaining of an effluent comprising essentially butanol.

[0049] In one embodiment, the second liquid phase comprises butanol with 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.

[0050] The recycling rate of the second liquid phase obtained in step b) to step c) is advantageously between 0.4 and 1.5 kg of recycle / kg of butanol present in the aqueous feed.

[0051] This recycle allows the recovery of the n-butanol not converted in step a) recovered in the aqueous phase from step b).

[0052] 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 c).

[0053] Advantageously, the butanol separation step is carried out in a temperature range between 30° and 180°C, preferably between 35°C and 150°C, even more preferably between 40°C and 135°C.

[0054] Advantageously, step c) allows recovery of more than 90% by weight of butanol from the second liquid phase, more preferably of more than 95% by weight, and even more preferably of more than 98% by weight.

[0055] 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.

[0056] Preferably, step c) includes at least one distillation step.

[0057] 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, around 0.15 MPa. The bottom temperature of the column ranges from 93°C to 120°C, depending on the selected head pressure and pressure drop in the column. The top temperature of the column, i.e., that of the first plate, ranges from 90°C to 110°C, depending on the selected operating pressure. The water column has a theoretical number of plates between 5 and 15.

[0058] The second column, known as the butanol column, operates at a head pressure approximately 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, i.e., that of the first plate, 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.

[0059] 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.

[0060] 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 hetero-azeotropic distillation system may further include a reboiler at the bottom of each column to heat the bottom end flow. These reboilers may be selected from vertical thermosiphon reboilers, kettle reboilers, furnace reboilers, and once-through reboilers.

[0061] Step d) of recycling the effluent comprising essentially butanol The process according to the invention includes a step d) of recycling the effluent comprising essentially butanol obtained in step c) to step a).

[0062] The recycling rate of the effluent consisting essentially of butanol obtained in step c) to step a) is advantageously between 0.01 and 5 kg of recycle / kg of butanol present in the aqueous feed.

[0063] 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 b) 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% by weight, preferably greater than 35% by weight, preferably greater than 40% by weight.

[0064] 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.

[0065] 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, more 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.

[0066] 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 0.9 MPa, and preferably between 0.45 and 0.8 MPa. The bottom temperature of this column is between 150 and 200 °C, preferably between 160 °C and 190 °C, and preferably between 165 °C and 180 °C. The number of theoretical plates is less than 70 plates, preferably 65 plates, and preferably 60 theoretical plates.

[0067] 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 at a content less than or equal to 25% by weight, preferably less than or equal to 20% by weight, preferably less than or equal to 15% by weight.

[0068] In one embodiment, the effluent comprising butanol at a content greater than 30% by weight, preferably greater than 35% by weight, preferably greater than 40% 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 60% by weight.

[0069] Optional step f) of recycling the effluent comprising butanol obtained in step e) back to step a) 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 40% by weight, obtained in step e) to step a).

[0070] The recycling rate is advantageously between 0.4 and 1.5 kg of recycle / kg of butanol present in the aqueous feed.

[0071] This recycle then makes it possible to recover DBE (di-butyl ether), an intermediate product of the dehydration reaction of butanol into butene-1, as well as n-butanol not converted in step a). DESCRIPTION OF THE FIGURES

[0072] [Fig. 1]: Process for producing butene-1 from an aqueous feed comprising butanol according to the invention:

[0073] An aqueous feed comprising butanol 1 is sent to a dewatering step a) to obtain an aqueous dewatering effluent 2 comprising butene-1 and butanol. The aqueous dewatering effluent 2 is sent to a separation step b) to obtain a first liquid phase 3 comprising butanol and butene-1, and a second liquid phase 4 comprising essentially water and butanol. The second liquid phase 4 is sent to a butanol separation step c) to obtain an effluent comprising essentially butanol 5. The effluent 5 is recycled d) to step a).

[0074] [Fig.2]: Process for producing butene-1 from an aqueous feed comprising butanol according to an embodiment of the invention:

[0075] An aqueous feed comprising butanol 1 is sent to a dewatering step a) to obtain an aqueous dewatering effluent 2 comprising butene-1 and butanol. The aqueous dewatering effluent 2 is sent to a separation step b) to obtain a first liquid phase 3 comprising butanol and butene-1, and a second liquid phase 4 comprising essentially water and butanol. The second liquid phase 4 is sent to a butanol separation step c) to obtain an effluent comprising essentially butanol 5. The effluent 5 is recycled d) to step a). The first liquid phase 3 is sent to a separation step e) to obtain an effluent comprising a butene-1 content greater than 20 wt% 6 and an effluent comprising butanol at a content greater than 30 wt% 7. The effluent 7 is recycled f) to step a). EXAMPLES

[0076] Example 1: A process for dehydrating n-butanol to 1-butene from an aqueous n-butanol feedstock according to the prior art, not in accordance with the invention

[0077] 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 64% n-butanol by weight and 36% water by weight. The process treats 5156.3 kg / h of feedstock (for an n-butanol flow rate of 3300 kg / h).

[0078] Step 1) Dehydration

[0079] The charge 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 input into the conversion reactor (in kg / h) / mass of catalyst in the conversion reactor (in kg) is 3.5 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% 79% 16% 4% 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 0.65.

[0085] The output composition of the dehydration reactor is:

[0086] [Tables2] 1-Butene 1621.0 kg / h n-butanol 594.0 kg / h Water 2326.9 kg / h 2-Butenes 326.7 kg / h DBE 82.17 kg / h others 205.26 kg / h

[0087] Step 2) of separation of the dewatering effluent

[0088] The aqueous effluent exiting the reactor is sent to a flash balloon operating at 40 °C and 0.382 MPa. A phase separation between two liquids is performed in this flask: First, a hydrocarbon phase is recovered, with a yield of 0.83 kg / kg of incoming n-butanol and the following composition: butene-1: 58.9 wt%, n-butanol: 18.6 wt%, DBE: 3.0 wt%, butenes-2: 19.0 wt%, and other carbon compounds: 0.5 wt% • Secondly, an aqueous phase is recovered, it has a flow rate of 0.73 kg / kg of n-butanol entering the conversion reactor and has the following composition: H2O: 96.5% by weight, n-butanol: 3.5% by weight.

[0089] The process according to the state of the art therefore made it possible to produce 1620.0 kg / h of butene-1 from 3300 kg / h of n-butanol.

[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 5156.3 kg / h of load (for an n-butanol flow of 3300 kg / h) of an aqueous mixture composed of 64% by weight of n-butanol and 36% by weight of water.

[0092] In this example, the aqueous charge of n-butanol is supplemented by the recycling stream, which is the stream of n-butanol with a purity of 99.5% from step 3).

[0093] Step 1) Dehydration

[0094] The aqueous butanol charge and the recycling stream consisting essentially of butanol are 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.

[0095] The dehydration catalyst used is the same alumina as that used for example 1.

[0096] After equilibration, the hourly weight rate, 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 set at 4 h'. The reduction in water content allows the catalyst to operate more efficiently.

[0097] The results of the catalytic tests are expressed in the table below:

[0098] [Tables3] Pass conversion Selectivity of carbon compounds Butanol 1-Butene 2-Butenes dibutyl ether other 82% 81% 15% 3% 1%

[0099] 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 0.66, which is a slight improvement compared to example 1.

[0100] The output composition of the dehydration reactor is as follows:

[0101] [Tables4] 1-Butene 1695.6 kg / h n-butanol 612.0 kg / h Water 2590.5 kg / h 2-Butenes 314.0 kg / h DBE 62.8 kg / h others 20.9 kg / h

[0102] Step 2) Separation of the dewatering effluent

[0103] The aqueous effluent from the reactor is sent to a flash tank operating at 40 °C and 0.389 MPa. Phase separation between two liquids is carried out in this tank:

[0104] • First, a so-called hydrocarbon phase is recovered; it has a flow rate of 0.79 kg / kg of incoming n-butanol and has the following composition: butene-1: 65.0 wt%, n-butanol: 19.6 wt%, DBE: 2.4 wt%, butenes-2: 12.0 wt% and other carbon compounds: 1.0 wt%

[0105] • Secondly, an aqueous phase is recovered; it has a flow rate of 0.81 kg / kg of n-butanol entering the conversion reactor and has the following composition: H2O: 96.3 wt%, n-butanol: 3.7 wt%.

[0106] Step 3) of butanol separation

[0107] The aqueous phase obtained in step 2) 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. The aqueous phase 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% is obtained. Both columns operate at a pressure of 0.116 MPa at the column head. The two columns have 8 and 8 theoretical plates, respectively.

[0108] The process according to a first embodiment of the invention made it possible to produce ((1695.9-1621.0) / 1621.0): 4.6% more Butene-1 than Example 1.

[0109] 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

[0110] 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 72% by weight n-butanol and 28% by weight water. The process treats 4583.3 kg / h of feedstock (for an n-butanol flow rate of 3300 kg / h).

[0111] In this example, in addition to the charge there is a recycling stream which is the residue from step 2)a) comprising unconverted butanol and DBE.

[0112] Step 1) Dehydration

[0113] The feed and recycling stream including unconverted butanol and dibutyl ether from step 2) are sent to a conversion reactor operating isothermally at 275°C, and at a pressure of 0.15 MPa, the reaction being endothermic, a heat input is made.

[0114] The dehydration catalyst used is the same alumina as that used for example 1 or 2.

[0115] 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 3 h 1 and the mass ratio butanol / DBE at reactor inlet is under these conditions 2.5.

[0116] The results of the catalytic test are expressed in the table below:

[0117] [Tables5] Pass conversion Selectivity of carbon compounds Butanol dibutyl ether Charge 1-Butene 2-Butenes other 67% 0% 48% 92% 7% 1%

[0118] 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 (0.8) is much higher.

[0119] The output composition of the dehydration reactor is as follows:

[0120] [Tableauxô] 1-Butene 2006.0 kg / h n-butanol 1600.0 kg / h Water 2396.0 kg / h 2-Butenes 152.8 kg / h DBE 1905.0 kg / h others 21.8 kg / h

[0121] Step 2) of separation of the dewatering effluent:

[0122] The aqueous effluent exiting the reactor is sent to a flash balloon operating at 40 °C and 0.289 MPa. A phase separation between two liquids is performed in this flask:

[0123] • First, a so-called hydrocarbon phase is recovered; it has a flow rate of 1.7 kg / kg of incoming n-butanol and has the following composition: butene-1: 35.6 wt%, n-butanol: 26.5 wt%, DBE: 34.0 wt%, butenes-2: 2.7 wt% and other carbon compounds: 0.3 wt%

[0124] • Secondly, an aqueous phase is recovered; it has a flow rate of 0.74 kg / kg of n-butanol entering the conversion reactor and has the following composition: H2O: 95.7 wt%, n-butanol: 4.3 wt%.

[0125] a) The recovered hydrocarbon phase is sent to a distillation column (here referred to as the hydrocarbon column or HC column) comprising 46 theoretical plates, as well as 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 0.65 kg / kg of n-butanol entering step 1), and its composition is as follows: butene-1: 92.8 wt%, H2O: 0.6 wt%, butenes-2: 6.6 wt%.On the other hand, 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 1.05 kg / kg of n-butanol entering step 1) and its composition is as follows: n-butanol: 43.0 wt%, DBE: 55.2 wt%, H2O: 0.9 wt%, butenes-2: 0.9 wt%. This column consumes 2.58 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.

[0126] b) 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 146.5 °C. The column recovers some of the unreacted n-butanol from the conversion reactor in the distillate. The flow rate of this effluent is 0.054 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 0.69 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 1.05 MJ / kg of n-butanol of heat in the form of reboiling steam; this heat is required at a thermal level of approximately 173.2 °C at the considered operating pressure.

[0127] The HC column has an energy demand in terms of reboiling steam of 2.4 MW. The water column has an energy demand in terms of reboiling steam of 0.96 MW, resulting in a total energy expenditure of 3.36 MW, or 6.03 MJ / kg of butene-1 produced.

[0128] Example 4: Process for dehydrating n-butanol to 1-butene from an aqueous n-butanol feedstock according to a second embodiment of the invention

[0129] The process exemplified according to the invention treats the same load as that of example 3.

[0130] To this charge are added the recycles which are the residue from step 2)a) comprising unreacted n-butanol and the intermediate product DBE, and the n-butanol stream with a purity of 99.5% wt from step 3).

[0131] Step 1) Dehydration

[0132] The charge and the 2 recycles are sent to a conversion reactor operating isothermally at 275°C, and at a pressure of 0.15 MPa, the reaction being endothermic, a heat input is made.

[0133] The dehydration catalyst used is the same alumina as that used for the previous examples.

[0134] 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 3.8 h 1 and the mass ratio butanol / DBE at reactor inlet is under these conditions 2.4.

[0135] The results of the catalytic tests are expressed in the table below:

[0136] [Tables7] Pass conversion Selectivity of carbon compounds Butanol dibutyl ether Charge 1-Butene 2-Butenes other 68% 0% 48% 93% 6% 1%

[0137] 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 (0.8) is much higher.

[0138] The output composition of the dehydration reactor is as follows:

[0139] [Tables8] 1-Butene 2002.0 kg / h n-butanol 1532.5 kg / h Water 2396.0 kg / h 2-Butenes 129.0 kg / h DBE 1950.0 kg / h others 21.5 kg / h

[0140]

[0141]

[0142]

[0143]

[0144]

[0145] The gain at the catalytic section level compared to example 3 lies in the reduction of catalyst requirements and therefore of reactor size, implying a gain in both CAPEX and OPEX on the process. Step 2) Separation of the dewatering effluent The aqueous effluent from the reactor is sent to a flash tank operating at 40 °C and 0.285 MPa. Phase separation between two liquids is performed in this tank: • Firstly, a so-called hydrocarbon phase is recovered; it has a flow rate of 1.7 kg / kg of incoming n-butanol and has the following composition: butene-1: 35.6% by weight, n-butanol: 25.4% by weight, DBE: 35.5% by weight, butenes-2: 2.3% by weight and other carbon compounds: 0.4% by weight, water: 0.8% by weight. • Secondly, an aqueous phase is recovered, it has a flow rate of 0.75 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. a) The recovered hydrocarbon phase is sent to a distillation column (referred to here 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 45.5°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: 5.1 wt%. On the other hand, at the bottom of the column is obtained a residue which is an effluent comprising unreacted n-butanol at the reactor level and the intermediate product DBE, the flow rate of this effluent is 1.06 kg / kg of n-butanol entering in step 1) and its composition is as follows: n-butanol: 41.0 wt%, DBE: 57.0 wt%, H2O: 0.9 wt%, butenes-2: 1.1 wt%.This column consumes 2.55 MW (2.78 MJ / kg n-butanol) of heat in the form of reboiling steam; this heat is required at a thermal level of approximately 177.6°C at the considered operating pressure. Step 3) of butanol separation The aqueous phase obtained in step 2) 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. The aqueous phase is injected at the common condenser. At the bottom of the first column, called the water column, a stream of water is obtained, and at the bottom of the The second column, known as the butanol column, yields a stream of n-butanol with a purity of 99.5% by weight. Both columns operate at a pressure of 0.116 MPa at the column head. Each column has 8 theoretical trays, respectively. The water column has an energy requirement of 0.26 MW (0.29 MJ / kg of feed n-butanol), required at a temperature of 104.8 °C. The n-butanol column has an energy requirement of 0.05 MW (0.058 MJ / kg of feed n-butanol), required at a temperature of 122.5 °C.

[0146] In the end, the HC column has a reboiling steam energy demand of 2.55 MW, the water column has a reboiling steam energy demand of 0.26 MW, and finally the n-butanol column has a demand of 0.05 MW. This gives a total energy expenditure of 2.86 MW, or 5.14 MJ / kg of butene-1, which represents an energy saving of 14.8% compared to Example 3.

Claims

Demands

1. A process for the production of butene-1, the process comprising the following steps: a) a dehydration step comprising the treatment of an aqueous feed comprising butanol, said dehydration step being carried out in the presence of a dehydration catalyst, and obtaining an aqueous dehydration effluent comprising butene-1 and butanol; b) a step of separating the aqueous dehydration effluent obtained in step a) and obtaining a first liquid phase comprising butanol and butene-1, and a second liquid phase comprising essentially water and comprising butanol; c) a butanol separation step comprising the treatment of the second liquid phase obtained in step b), and obtaining an effluent comprising essentially butanol; d) a step of recycling the effluent comprising essentially butanol 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 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.

7. A process according to claim 6, wherein in step b) the first liquid phase further comprises DBE at a content of between 0.5 and 50% by weight.

8. A process according to any one of the preceding claims, wherein the recycling rate of the second liquid phase obtained in step b) to step c) is between 0.4 and 1.5 kg of recycle / kg of butanol present in the aqueous feed.

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

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 b) 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) back to step a)

13. A process according to claim 12, wherein the recycling rate is between 0.4 and 1.5 kg of recycle / kg of butanol present in the aqueous feed.

14. A process according to any one of claims 12 or 13, wherein the feed processed in the dehydration step a) 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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