Process for hydrogenating a feedstock comprising unsaturated hydrocarbons

Abstract

The invention relates to a process for hydrogenating a feed comprising unsaturated hydrocarbon compounds, in which: - hydrogen containing impurities is sent to a hydrogen treatment section comprising an adsorbent to obtain treated hydrogen and an adsorbent laden with impurities; - the treated hydrogen and said feed are sent to a reaction section in the presence of a catalyst to obtain an effluent comprising hydrogenated hydrocarbon compounds; - the effluent is sent to a separation section to obtain a hydrogen-rich gas phase; - said hydrogen-rich gas phase is compressed and then heated to a desorption temperature of the adsorbent in the treatment section, and then said compressed and heated hydrogen-rich gas phase is contacted with a fixed bed of adsorbent laden with impurities to obtain a regenerated adsorbent and an effluent laden with impurities. Figure 2 to be published

Description

Title of the invention: Process for hydrogenating a feed comprising unsaturated hydrocarbons. Technical field

[0001] The present invention relates to the field of hydrogen storage and transport as an energy source, and in particular to that of organic compounds suitable for storing and transporting hydrogen.

[0002] The present invention relates more particularly to a process for hydrogenating a feed comprising unsaturated hydrocarbons, and more particularly aromatic compounds, such as benzene or toluene, to produce hydrogenated hydrocarbons. State of the art

[0003] The storage and transport of hydrogen using carrier molecules are currently the subject of numerous studies. One known method for storing and transporting hydrogen involves the chemical association of hydrogen with a carrier molecule called LOHC, for "Liquid Organic Hydrogen Carrier." The hydrogenated carrier molecule stores the bound hydrogen and can be stored and / or transported. The bound hydrogen can then be released, most often near the point of consumption, in a dehydrogenation step of the hydrogenated carrier molecule. The toluene / methylcyclohexane chemical pair is a known implementation of this method of transport and / or storage via the LOHC route. Hydrogen is stored by hydrogenating toluene to methylcyclohexane.The reverse dehydrogenation reaction of methylcyclohexane allows for the recovery of hydrogen. The advantage of this method is that it enables the storage of hydrogen under pressure conditions close to atmospheric pressure and at ambient temperature, thus facilitating its implementation compared to hydrogen storage processes under pressure or by liquefaction.

[0004] The hydrogenation of unsaturated compounds, and more particularly of aromatic compounds, is generally carried out in the presence of a catalyst in homogeneous phase.

[0005] US4357478 discloses a process for hydrogenating an unsaturated organic compound in the presence of a soluble catalyst obtained by reaction between an organometallic reducing agent with a mixture of at least one transition metal carboxylate and at least one strong carboxylic acid.

[0006] Document EP0668257 discloses a process for hydrogenating benzene in the presence of a homogeneous catalyst obtained by reduction by a trialkylaluminum of a nickel carboxylate and a sodium carboxylate.

[0007] Patent EP0663238 discloses a process for preparing a homogeneous-phase hydrogenation catalyst in which an oxidizing agent is introduced after the formation of the active catalytic species. Such a catalyst can be used in selective or total hydrogenation reactions of unsaturated mono- or polyolefinic, acetylenic, or aromatic compounds. This document also addresses the problem of the presence of water in the reaction medium (dissolved water), which tends to progressively agglomerate the catalyst, leading to a significant loss of catalytic activity. Consequently, a hydrogen drying step upstream of the hydrogenation step is conceivable.

[0008] Document EP0031209 discloses a method for drying hydrogen implementing a temperature swing adsorption (TSA) process comprising an adsorbent to remove water from wet hydrogen. A portion of the dry hydrogen obtained after adsorption is heated and sent to a regeneration column to regenerate the adsorbent. A drawback of such an adsorbent regeneration method lies in the subsequent need to recycle the gas used to regenerate the adsorbent, which has become "wet" again, upstream of the adsorbents in order to dry it again. This step therefore requires the use of a dedicated compressor, a costly and energy-intensive device. Objects of the invention

[0009] The present invention relates to a process for hydrogenating a feed comprising unsaturated hydrocarbon compounds in the presence of a hydrogenation catalyst comprising at least the following steps:

[0010] a) hydrogen including impurities is sent into a hydrogen treatment section including an adsorbent included in at least one fixed bed of adsorbent by contacting the hydrogen including impurities with said at least one fixed bed of adsorbent to obtain treated hydrogen and at least one fixed bed of adsorbent loaded with impurities;

[0011] b) the treated hydrogen obtained at the end of step a) and the feed comprising unsaturated hydrocarbon compounds are sent to a reaction section in the presence of a hydrogenation catalyst in order to obtain an effluent comprising hydrogenated hydrocarbon compounds;

[0012] c) the effluent obtained at the end of step b) is sent to a separation section to obtain a hydrogen-rich gas phase and a liquid phase rich in hydrogenated hydrocarbon compounds;

[0013] d) at least part of the hydrogen-rich gas phase obtained at the end of step c) is compressed to obtain a hydrogen-rich compressed gas phase;

[0014] e) said hydrogen-rich compressed gas phase obtained at the end of step d) is heated at least partially until a desorption temperature of said at least one adsorbent from the treatment section implemented in step a) is reached, then said hydrogen-rich compressed and heated gas phase is brought into contact with at least one fixed bed of impurity-laden adsorbent from said hydrogen treatment section to obtain a regenerated adsorbent and an impurity-laden effluent.

[0015] The Applicant has developed a new process for hydrogenating a feed comprising polyunsaturated compounds in the presence of a catalyst and hydrogen, in which the hydrogen used is pre-treated in a treatment section including an adsorbent to capture the impurities contained in the hydrogen. Unlike existing processes, the adsorbent, which becomes loaded with impurities, is regenerated using a regeneration fluid internal to the hydrogenation process. Indeed, the regeneration fluid, or more precisely the hydrogen-rich compressed gas phase obtained at the end of step d) of the process according to the invention, consists of a gas derived from the reaction effluent of the hydrogenation. One of the advantages of using such a gas is to avoid the need to introduce an external fluid into the process.Furthermore, using a gaseous regeneration fluid minimizes the energy consumption required to reach the desired temperature for desorption of the impurity-laden adsorbent. In addition, using a gaseous stream containing impurity-free hydrogen allows for the use of only the necessary amount of adsorbent to treat the hydrogen; design rules no longer require a larger quantity of adsorbent to treat the regeneration fluid before use. Finally, one of the advantages of the process according to the invention is avoiding the need for a dedicated compressor specifically for recycling the regeneration fluid by sharing the regeneration compressor with the reaction unit. This results in an approximately 5% reduction in energy consumption while significantly lowering capital expenditures by around 10%.

[0016] According to one or more embodiments of the invention, said process includes a step f) in which at least one other part of said hydrogen-rich compressed gas phase obtained at the end of step d) is recycled into the reaction section of step b).

[0017] According to one or more embodiments of the invention, at least part of the impurity-laden effluent obtained at the end of step e) is sent to a separation section to obtain a hydrogen-rich gas stream and a stream rich in impurities, then at least part of said hydrogen-rich gas stream is recycled in the hydrogen treatment section of step a).

[0018] According to one or more embodiments of the invention, said process includes a step g) in which said regenerated adsorbent from said hydrogen treatment section obtained at the end of step e) is cooled to a temperature below its desorption temperature.

[0019] According to one or more embodiments of the invention, step g) is carried out by bringing said fixed bed of regenerated adsorbent into contact with the hydrogen-rich compressed gaseous phase obtained at the end of step d) and / or by bringing said fixed bed of regenerated adsorbent into contact with a portion of said liquid phase rich in hydrogenated hydrocarbon compounds obtained at the end of step c).

[0020] According to one or more embodiments of the invention, between step b) and c) a complementary step of hydrogenation of the effluent comprising hydrogenated hydrocarbon compounds obtained at the end of step b) is carried out in the presence of a hydrogenation catalyst in a second reaction section.

[0021] According to one or more embodiments of the invention, in step b), said feed is sent into the reaction section in liquid form, and in which said hydrogenation catalyst is soluble in said feed in liquid form.

[0022] According to one or more embodiments of the invention, said charge comprises unsaturated hydrocarbon compounds selected from olefinic, linear, branched or cyclic hydrocarbons, or from hydrocarbons comprising at least one aromatic ring.

[0023] According to one or more embodiments of the invention, said unsaturated hydrocarbon compounds are selected from butadiene, cyclododecatriene, vinylacetylene, cyclopentadiene, butene, cyclopentene, benzene, alkylbenzenes, phenol and its derivatives, alkyl diphenyls, alkylnaphthalenes, in particular toluene, dibenzyltoluene, xylenes, methyl naphthalene, N-ethylcarbazole, benzonitrile, unsaturated fatty oils and ethyl linoleate.

[0024] According to one or more embodiments of the invention, said unsaturated hydrocarbon compounds are toluene.

[0025] According to one or more embodiments of the invention, said impurities contained in the hydrogen supplied in step a) are chosen from water, oxygenated organic compounds or dioxygen.

[0026] According to one or more embodiments of the invention, when said impurity contained in the hydrogen is water, the water content is between 1 and 3,000 ppm by volume relative to the total volume of hydrogen to be treated

[0027] According to one or more embodiments of the invention, in step a), said adsorbent is selected from molecular sieves of type 3A, 4A, 5A, and 13X, activated aluminas, silica gels, used alone or in combination.

[0028] According to one or more embodiments of the invention, the hydrogen treatment section comprises two adsorption columns.

[0029] According to one or more embodiments of the invention, one of the columns is implemented in step a) of the process and the other column is implemented in step e) of the process according to the invention.

[0030] According to one or more embodiments of the invention, step e) is carried out periodically. List of figures

[0031] [Fig-1] Fig. 1 schematically illustrates a hydrogenation process of a charge comprising toluene according to the prior art, wherein the hydrogen used for regeneration of the adsorbent is a part of the treated hydrogen from the hydrogen treatment section.

[0032] [Fig.2] Fig.2 schematically illustrates a hydrogenation process for a feed comprising toluene according to an embodiment of the invention, in which the hydrogen used for the regeneration of the adsorbent is a part of the recycle gas from the hydrogenation process. Detailed description

[0033] In the following detailed description, many specific details are set forth to provide a more thorough understanding of the process. However, it will be apparent to those skilled in the art that the process can be implemented without necessarily including all of these specific details. In other cases, well-known features have not been described in detail to avoid unnecessarily complicating the description.

[0034] In the sense of the present invention, the different parameter ranges / different operating conditions 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.

[0035] In this description, the term "include" is synonymous with (means the same as) "include" and "contain," and is inclusive or open-ended and does not exclude other unstated elements. It is understood that the term "include" includes the exclusive and closed term "consist." Furthermore, in this description, an effluent comprising essentially, substantially, or solely a compound A corresponds to to an effluent comprising at least 95% by weight, preferably at least 98% by weight, very preferably at least 99% by weight, or even 100%, of compound A.

[0036] Finally, in the present description, an effluent or stream rich in a compound A corresponds to an effluent comprising at least 50% by weight or volume, preferably at least 70% by weight or volume, preferably at least 90% by weight or volume, preferably at least 95% by weight or volume, of compound A, such that at least between 50% by weight or volume and 99% by weight or volume of compound A.

[0037] In the following, particular and / or preferred embodiments of the invention may be described. They may be implemented separately or in combination with each other, without limitation of combination where technically feasible. Hydrogenation process

[0038] According to the invention, a hydrogenation process is carried out on a feed comprising unsaturated hydrocarbon compounds in the presence of a hydrogenation catalyst comprising at least the following steps:

[0039] a) hydrogen including impurities is sent into a hydrogen treatment section including an adsorbent included in at least one fixed bed of adsorbent by contacting the hydrogen including impurities with said at least one fixed bed of adsorbent to obtain treated hydrogen and at least one fixed bed of adsorbent loaded with impurities;

[0040] b) the treated hydrogen obtained at the end of step a) and the feed comprising unsaturated hydrocarbon compounds are sent to a reaction section in the presence of a hydrogenation catalyst in order to obtain an effluent comprising hydrogenated hydrocarbon compounds;

[0041] c) the effluent obtained at the end of step b) is sent to a separation section to obtain a hydrogen-rich gas phase and a liquid phase rich in hydrogenated hydrocarbon compounds;

[0042] d) at least part of the hydrogen-rich gas phase obtained at the end of step c) is compressed to obtain a hydrogen-rich compressed gas phase;

[0043] e) said hydrogen-rich compressed gas phase obtained at the end of step d) is heated at least partially until a desorption temperature of said at least one adsorbent from the treatment section implemented in step a) is reached, then said hydrogen-rich compressed and heated gas phase is brought into contact with at least one fixed bed of impurity-laden adsorbent from said hydrogen treatment section to obtain a regenerated adsorbent and an impurity-laden effluent.

[0044] According to the invention, the feedstock used in the hydrogenation process comprises hydrocarbon compounds preferably selected from olefin-type hydrocarbons, linear, branched or cyclic, or from hydrocarbons with at least an aromatic ring, in particular from at least one of the following compounds: butadiene, cyclododecatriene, vinylacetylene, cyclopentadiene, butene, cyclopentene, benzene, alkylbenzenes, phenol and its derivatives, alkyl diphenyls, alkylnaphthalenes, in particular toluene, dibenzyltoluene, xylenes, methylnaphthalene, N-ethylcarbazole, benzonitrile, unsaturated fatty oils and ethyl linoleate. Preferably the filler comprises toluene.

[0045] Preferably, the charge comprises an unsaturated hydrocarbon content of more than 50% by weight, or even more than 70% by weight, and preferably more than 95% by weight relative to the total weight of the charge.

[0046] The hydrogen to be treated sent to step a) of the process according to the invention may include impurities selected from at least one of the following compounds: water, oxygenated organic compounds, dioxygen.

[0047] Preferably, the impurity to be treated is water. In an embodiment according to the invention, when the impurity to be treated is water, the hydrogen to be treated sent to step a) comprises between 1 and 3,000 ppm by volume relative to the total volume of the hydrogen to be treated, preferably between 30 and 2,500 ppm. In an embodiment according to the invention, the treated hydrogen obtained at the end of step a) comprises a water content lower than the water content in the hydrogen to be treated, preferably a water content of less than 30 ppm by volume relative to the total volume of the hydrogen treated, or even more preferably a content of less than 1 ppm by volume.

[0048] According to a particular embodiment of step a), the treatment section comprises at least two fixed beds of adsorbent in the form of adsorption columns, preferably between two and four adsorption columns, containing said adsorbent. When the hydrogen treatment section comprises two adsorption columns, one operating mode may be a "swing" mode, in which one of the columns is online, i.e., in operation, while the other column is in reserve. When the adsorbent in the online column is depleted, this column is isolated while the reserve column is brought online, i.e., into operation. The adsorbent laden with impurities can then be regenerated in situ and / or replaced with fresh adsorbent so that the column containing it can be brought online again once the other column has been isolated.

[0049] According to another particular embodiment of step a), the treatment section comprises at least two fixed beds of adsorbent in the form of adsorption columns, wherein the two columns operate in series. When the adsorbent in the upstream column is depleted, this first column is isolated and the spent adsorbent is either regenerated in situ or replaced with new adsorbent. The column is then returned to the last position, and so on. This operation is called a permutable mode, or, in English, "PRS" for Permutable Reactor System, or "lead and lag" in Anglo-Saxon terminology. Using at least two adsorption columns helps limit the potential and rapid poisoning and / or clogging of the adsorbent due to the combined action of impurities, contaminants, and insolubles that may be present in the hydrogen being treated. Having at least two adsorption columns facilitates the replacement and / or regeneration of the adsorbent, ideally without stopping the process, and also helps control costs and limit adsorbent consumption.

[0050] According to one or more embodiments of the invention, the adsorbent included in the treatment section of step a) is selected from type 3A, 4A, 5A, and 13X molecular sieves, activated aluminas, and silica gels, used alone or in combination. Preferably, the adsorbent used comprises an activated alumina and a type 4A molecular sieve.

[0051] According to the invention, the treated hydrogen obtained at the end of step a) and the feed comprising unsaturated hydrocarbon compounds are sent to a reaction section in the presence of a hydrogenation catalyst in order to obtain an effluent comprising hydrogenated hydrocarbon compounds. The hydrogenation reaction is advantageously carried out in the presence of a hydrogenation catalyst, at a temperature between 100 and 300°C, preferably between 130 and 250°C, at a pressure between 0.5 and 10 MPa, preferably between 1 and 5 MPa, and a ppH2 between 0.4 and 2.0 MPa abs.

[0052] Preferably, said feedstock is fed into the reaction section in liquid form, and the hydrogenation catalyst is soluble in said feedstock in liquid form. The hydrogenation catalyst used in the first reaction section can be any catalyst known to those skilled in the art that allows at least partial hydrogenation of polyunsaturated hydrocarbon compounds to hydrogenated hydrocarbon compounds. A heterogeneous catalyst comprising nickel and / or platinum deposited on a solid support such as alumina and / or silica can be used. Preferably, the catalyst is a homogeneous catalyst soluble in said feedstock in liquid form. The homogeneous catalyst is notably synthesized by reacting an organometallic reducing agent with a mixture of at least one transition metal carboxylate and at least one strong carboxylic acid or an alkali metal carboxylate.

[0053] Preferably, the catalyst used is based on a nickel organometallic complex obtained, for example, from reduction by a trialkylaluminum of formula AIR1R2R3, in which Rb, R2, and R3 each independently represent the one of the others a linear or branched alkyl group having from 1 to 12 carbon atoms in solution in a hydrocarbon or mixture of hydrocarbons, of at least one nickel carboxylate of formula R4COONi in which R4 is a hydrocarbon remnant having from 1 to 24 carbon atoms and most often from 6 to 12 carbon atoms and possibly in the presence of at least one sodium carboxylate in solution of formula R5COONa in which R5 is a hydrocarbon remnant having from 1 to 24 carbon atoms.

[0054] In an embodiment according to the invention, a further hydrogenation step of the effluent comprising hydrogenated hydrocarbon compounds obtained at the end of step b) is carried out between steps b) and c) in the presence of a hydrogenation catalyst in a second reaction section. The operating conditions for hydrogenation and the nature of the hydrogenation catalyst may be different from or identical to those used in the first reaction section. Preferably, the operating conditions are identical.

[0055] According to the invention, the effluent obtained at the end of step b), or optionally from the complementary hydrogenation step in the second reaction section, is sent to a separation section to obtain a hydrogen-rich gas phase and a liquid phase rich in hydrogenated hydrocarbon compounds (step c) of the process according to the invention). At least a portion of the hydrogen-rich gas phase, preferably at least 25% by volume and even more preferably at least 50% by volume relative to the total volume of the hydrogen-rich gas phase, is compressed to obtain a compressed hydrogen-rich gas phase (step d) of the process according to the invention).

[0056] According to the invention, at least a portion of the hydrogen-rich compressed gas phase is heated to the desorption temperature of the adsorbent used in the hydrogen treatment section, and then contacted with at least one impurity-laden adsorbent to obtain a regenerated adsorbent and an impurity-laden effluent (step e) of the process according to the invention). In one embodiment of the invention, the hydrogen-rich compressed gas phase is heated to a temperature of at least 120°C, preferably at least 150°C, and preferably between 150°C and 300°C. Preferably, the adsorbent is maintained at its regeneration temperature for a period of at least 2 hours, and more preferably at least 8 hours. Adsorbent regeneration is typically carried out at a pressure between 0.1 and 10 MPa, preferably between 1 and 4 MPa.When the adsorbent is loaded with impurities, the adsorbent is generally cooled to a temperature below its desorption temperature, i.e., to a temperature below 150°C, preferably below 120°C (optional step g of the process according to the invention). This step can advantageously be carried out by . contacting said fixed bed of impurity-laden adsorbent with the hydrogen-rich compressed gas phase (obtained at the end of step d)) and / or by contacting said fixed bed of impurity-laden adsorbent with at least a portion of said liquid phase rich in hydrogenated hydrocarbon compounds obtained at the end of step c). Advantageously, the impurity-laden effluent obtained at the end of step e) is sent to a separation section to obtain a hydrogen-rich gas stream and an impurity-rich stream, which allows at least a portion of said hydrogen-rich gas stream to be recycled in the hydrogen treatment section of step a).

[0057] In a particular embodiment according to the invention (optional step f of the process according to the invention), and depending on the water content of the hydrogen-rich compressed gas phase obtained at the end of step d) of the process, it is possible to recycle at least a portion of said hydrogen-rich compressed gas phase directly into the reaction section of step b). Detailed description of the figures

[0058] In order to better understand the invention, the following description, by way of application example, relates on the one hand to a hydrogenation process known in the prior art in which at least a portion of the dry hydrogen from the adsorption column is used as a regeneration gas (see [Fig. 1]), and on the other hand to a hydrogenation process according to the invention in which at least a portion of the hydrogen-rich gas phase from the effluent comprising hydrogenated hydrocarbon compounds is used as a regeneration gas (see [Fig. 2]). In this figure, reference numerals identical to those in [Fig. 1] designate similar or identical elements.

[0059] The preferred embodiment of the invention relates to the hydrogenation of toluene to methylcyclohexane, and this embodiment will be described in detail below, although the invention is not limited to it. Furthermore, the impurity to be removed is water, although the invention is not limited to it. The hydrogen to be treated, which is sent to the treatment section, is referred to herein as "wet hydrogen," that is, containing a certain water content, preferably between 30 and 2500 ppm by volume relative to the volume of the hydrogen to be treated. The hydrogen obtained at the end of the treatment section is referred to as "dry hydrogen," that is, containing a water content lower than that of the wet hydrogen, preferably less than 30 ppm by volume relative to the total volume of the dry hydrogen.

[0060] Referring to [Fig. 1], illustrating a prior art process diagram, wet hydrogen is fed via line 101 into a first hydrogen treatment section comprising an adsorption column 3a to obtain dry hydrogen. The wet hydrogen can be supplied from any known facility of a person skilled in the art, such as hydrogen from an electrolyzer. The dry hydrogen is then sent via line 102 to the hydrogenation unit 1 comprising at least one hydrogenation reaction section 2. The hydrogen processing section, also referred to here as the drying reaction section, comprises two adsorption columns 3a and 3b, for example in fixed bed configuration, such as dryers, used alternately in two modes of operation:

[0061] - a so-called normal mode of operation, in which the adsorption of water contained in wet hydrogen used downstream of hydrogenation unit 1,

[0062] - a method of regeneration by desorption of water captured under the effect of heat supplied by a regeneration fluid. This fluid carries the desorbed water away from the adsorption column. In the case of [Fig. 1], dryer 3a is in normal mode, and dryer 3b is in regeneration mode. The hydrogenation reaction section 2 comprises a reactor 4 fed on one side by dry hydrogen via line 102 and on the other side by a feed containing toluene, via line 103, in liquid form. The hydrogenation process carried out in reactor 4 is implemented in the presence of a soluble catalyst. Since the hydrogenation reaction of toluene is exothermic, a recirculation loop with cooling is integrated on reactor 4. Thus, a fraction of the reaction medium is taken from reactor 4 via line 123 by means of a circulation pump 5 and is directed to a heat exchanger 6 via line 121 to be cooled and then reinjected into the reactor via line 122.The effluent 104, containing methylcyclohexane, is drawn from the hydrogenation reactor 4 and cooled by a cooling device 10, for example a condenser, and then sent to a separation vessel 11. A gas stream 130 is recovered, consisting essentially of unreacted hydrogen, an organic liquid phase 112 consisting essentially of methylcyclohexane and possibly some unreacted toluene. If the gas stream 130 has acceptable moisture content, for example a water content of less than 1 ppm by volume relative to the total volume of the gas stream, it can advantageously be recycled directly into the reactor 4 via the compressor 14 and lines 131, 132 and 133, for example mixed with dry hydrogen from line 102.

[0063] In order to regenerate the water-laden adsorbent in dryer 3b, a portion of the dry hydrogen from dryer 3a is sent as a regeneration fluid, via compressor 22, lines 107 and 109, and after heating via a heating device 105 (such as a heat exchanger), to the bottom of dryer 3b to desorb the captured water. The impurity-rich effluent 110 is drawn off at the top of dryer 3b for recycling into dryer 3a.

[0064] With reference to [Fig. 2], illustrating a process diagram according to the invention, wet hydrogen is brought via line 101 into a first section of Hydrogen processing includes an adsorption column 3a to obtain dry hydrogen. The wet hydrogen can come from any installation known to those skilled in the art, such as hydrogen from an electrolyzer. The dry hydrogen is then sent via line 102 to the hydrogenation unit 1, which includes at least one hydrogenation reaction section 2. The hydrogen processing section, also referred to here as the drying reaction section, includes two adsorption columns 3a and 3b, for example, fixed-bed columns such as dryers, used alternately in two operating modes:

[0065] - a so-called normal mode of operation, in which the adsorption of water contained in wet hydrogen used downstream of hydrogenation unit 1,

[0066] - a method of regeneration by desorption of water captured under the effect of heat supplied by a regeneration fluid. This fluid carries the desorbed water away from the adsorption column. In the case of [Fig. 2], dryer 3a is in normal mode, and dryer 3b is in regeneration mode. The hydrogenation reaction section 2 comprises a reactor 4 fed on one side by dry hydrogen via line 102 and on the other side by a feed containing toluene, via line 103, in liquid form. The hydrogenation process carried out in reactor 4 is implemented in the presence of a soluble catalyst. Since the hydrogenation reaction of toluene is exothermic, a recirculation loop with cooling is integrated on reactor 4. Thus, a fraction of the reaction medium is taken from reactor 4 via line 123 by means of a circulation pump 5 and is directed to a heat exchanger 6 via line 121 to be cooled and then reinjected into the reactor via line 122.The effluent 104, containing methylcyclohexane, is withdrawn from the hydrogenation reactor 4 and cooled by a cooling device 10, for example, a condenser, and then sent to a separation vessel 11. A gas stream 130, consisting essentially of unreacted hydrogen, and an organic liquid phase 112, consisting essentially of methylcyclohexane and possibly some unreacted toluene, are recovered. According to the embodiment illustrated in [Fig. 2], in order to regenerate the dryer 3b, at least a portion 131 of the gas stream 130, consisting essentially of hydrogen, is compressed by means of the compressor 14 and then sent via lines 132 and 134 to at least one heating device 9. Any heating device 9 known to those skilled in the art, such as a heat exchanger or furnace (electric or otherwise), can be used.The other part 133 of the compressed gaseous fluid is returned to the hydrogenation reaction section 2 which includes at least one hydrogenation reactor 4.

[0067] The compressed and heated hydrogen-rich gas phase 109 produced by the heating device 9 is then directed to the dryer 3b, thus heating the adsorbent and thereby desorbing the water molecules. The flow Hydrogen charged with desorbed water is carried out of the dryer 3b via line 110 to a cooling device 150. During cooling, the condensing water is recovered by decantation in a separator tank 154 and discharged via line 152. Advantageously, before passing through the cooling device 150, the water-charged hydrogen stream 110 is sent to a feed / effluent type heat exchanger 8 in order to transfer some of its heat to the compressed hydrogen stream 133.

[0068] The cooled gas stream 153 obtained via the separator flask 154 can then be mixed with the hydrogen 100 upstream of the dryer 3a.

[0069] Once regenerated, the adsorbent material contained in the dryer 3b is advantageously cooled for use in another adsorption cycle. Advantageously, the process includes a step in which the regenerated adsorbent is cooled to a temperature below its desorption temperature by contacting the regenerated adsorbent with the compressed hydrogen stream 132. Alternatively, the cooling can be achieved by contacting said regenerated adsorbent material with a portion of the methylcyclohexane-rich liquid phase 112 obtained in the separation step. Examples

[0070] The following example in accordance with the invention illustrates the invention without limiting its scope.

[0071] The hydrogenation unit 1 is sized to react 3750 kg / h of hydrogen for the hydrogenation of toluene. The effluent 104 from the toluene hydrogenation consists mainly of methylcyclohexane (content >98% by weight relative to the total weight of the effluent). The methylcyclohexane produced can be easily stored or transported. The hydrogen thus stored / transported can be recovered by dehydrogenating the methylcyclohexane to toluene. Two dryers 3a and 3b (absorption columns) are implemented upstream of the hydrogenation unit 1. These two dryers 3a and 3b are operated alternately under the following conditions: - adsorption in order to dry hydrogen; - regeneration so as to desorb the water under the action of the heat supplied by a regeneration fluid.

[0072] The adsorbents used in both dryers are: - activated alumina, known in particular under the trade name AxSorb® 510, and - a type 4A molecular sieve (known in particular under the trade name Axsorb® 543.

[0073] The dimensions of the adsorbent bed in each column are 2.5 m in diameter and 7.4 m in height. During the adsorption phase, adsorption column 3a is fed with 3750 kg / h of water-saturated hydrogen with a purity >99.9%, which also includes wet hydrogen produced by the regeneration of the adsorbent sent via line 153. The column is operated at 2.3 MPa and at ambient temperature. Assuming a water-free sieve at the beginning of the adsorption phase, adsorption column 3a dries the water-saturated hydrogen to obtain hydrogen with a water content of less than 1 ppm by volume relative to the total volume of hydrogen. During this adsorption, the sieve gradually becomes saturated with water, requiring switching to a second column after 18 hours. The dry hydrogen from column 3a is then directed via line 102 to the hydrogenation reaction section 2.This reaction section includes a continuous stirred-tank reactor (CSTR). Stirring and cooling of the reactor are achieved by a recirculation loop (lines 120, 121, 122), comprising a pump 5 and a heat exchanger 6 for removing the heat of reaction.

[0074] Reactor 4 is fed with a charge comprising toluene via line 103 having the following composition (in % weight relative to the total weight of the charge): toluene 99.5% Other aromatics (benzene, xylene): 0.1% Non-aromatic compounds (methylcyclohexane, etc.): 0.4%

[0075] The feed rate in reactor 4 via line 103 is 57.0 tonnes / h. The catalyst used is a nickel-in-solvent organometallic complex (sold by Axens under the trade name "HC 1025"). The reactor is operated at a temperature of 200°C and a pressure of 1.5 MPa. The reactor effluent is withdrawn as steam via line 104.

[0076] The composition of the effluent is as follows (% by weight relative to the total weight of the effluent): hydrogen: 1.3% cyclohexane: 0% toluene: 0% methylcyclohexane: 98.2% other compounds: 0.5%

[0077] The effluent 104 is directed to a condenser 10 and a separator flask 11 from which a vapor phase 130 comprising the majority of the unreacted hydrogen and a liquid phase 112 comprising the majority of the methylcyclohexane produced are recovered.

[0078] A portion 131 of the unreacted hydrogen is compressed with a compressor 14 to a pressure of approximately 2.3 MPa and recycled to the section reaction (flow 133). This flow contains mainly hydrogen (98.4 mol%). Another part 134 of the compressed hydrogen, about 50% by volume, is gradually heated in an electric furnace 9. The outlet temperature of the furnace 9 is gradually increased from 85°C (temperature of flow 132 at the discharge of the compressor 14) to 170°C in 1 hour.

[0079] The compressed and heated stream 109 obtained is then directed to the adsorption column 3b, thereby increasing the temperature of the adsorbent from ambient temperature to approximately 150°C in 12 hours. Under the effect of the temperature, the water adsorbed by the sieve is desorbed and carried away by the hot regeneration fluid through line 110. This stream is then cooled to ambient temperature in the heat exchanger 150 and directed to the separator vessel 154 where the water is recovered after separation (line 152). The hydrogen-rich stream 153 from the balloon 154, and the hydrogen stream 101 are mixed and constitute the makeup hydrogen for the hydrogenation unit 1. At the end of the temperature rise period, the sieve of the adsorption column 3b is cooled by maintaining the circulation of the regeneration fluid described above but by removing its heating by the furnace 9.

[0080] Compared to an implementation of the installation according to [Fig.1], the advantage of this solution is to avoid the addition of a dedicated compressor to circulate the regeneration fluid thanks to the sharing of the recycle compressor 14 of the reaction unit 1, making it possible to obtain a reduction of about 5% in energy consumption while significantly reducing, on the order of 10%, the investment costs.

Claims

Demands

1. A process for hydrogenating a feed comprising unsaturated hydrocarbon compounds (103) in the presence of a hydrogenation catalyst comprising at least the following steps: a) hydrogen (101) comprising impurities is sent to a hydrogen treatment section (3a, 3b) comprising an adsorbent included in at least one fixed bed of adsorbent by contacting the hydrogen comprising impurities with the at least one fixed bed of adsorbent (3a) to obtain treated hydrogen (102); b) the treated hydrogen (102) obtained at the end of step a) and the feed comprising unsaturated hydrocarbon compounds (103) are sent to a reaction section (2) in the presence of a hydrogenation catalyst in order to obtain an effluent (104) comprising hydrogenated hydrocarbon compounds;c) the effluent (104) obtained at the end of step b) is sent to a separation section to obtain a hydrogen-rich gas phase (130) and a liquid phase rich in hydrogenated hydrocarbon compounds (112); d) at least a part (131) of the hydrogen-rich gas phase (130) obtained at the end of step c) is compressed to obtain a hydrogen-rich compressed gas phase (132); e) at least partially (134) the hydrogen-rich compressed gas phase (132) obtained at the end of step d) is heated until a desorption temperature of said adsorbent from the treatment section implemented in step a is reached, then said hydrogen-rich compressed and heated gas phase (109) is brought into contact with at least one fixed bed of impurity-laden adsorbent (3b) from said hydrogen treatment section to obtain a regenerated adsorbent and an impurity-laden effluent (110).

2. A process according to claim 1, comprising a step f) in which at least one other part (133) of said hydrogen-rich compressed gas phase obtained at the end of step d) is recycled into the reaction section (2) of step b).

3. A process according to claim 1 or 2, wherein at least part of the impurity-laden effluent (110) obtained at the end of step e) is sent to a separation section (154) to obtain a hydrogen-rich gas stream (153) and a stream rich in impurities (152), then at least part of said hydrogen-rich gas stream is recycled in the hydrogen treatment section (3a, 3b) of step a).

4. A process according to any one of the preceding claims, comprising a step g) in which said regenerated adsorbent from said hydrogen treatment section (3a, 3b) obtained at the end of step e) is cooled to a temperature below its desorption temperature.

5. A process according to claim 4, wherein step g) is carried out by bringing said fixed bed of regenerated adsorbent (3b) into contact with the hydrogen-rich compressed gas phase (132) obtained at the end of step d) and / or by bringing said fixed bed of regenerated adsorbent (3b) into contact with a portion of said liquid phase rich in hydrogenated hydrocarbon compounds (112) obtained at the end of step c).

6. A process according to any one of the preceding claims, wherein between steps b) and c) a further step of hydrogenation of the effluent comprising hydrogenated hydrocarbon compounds obtained at the end of step b) is carried out in the presence of a hydrogenation catalyst in a second reaction section.

7. A method according to any one of the preceding claims, wherein in step b) said feed (103) is sent into the reaction section (2) in liquid form, and wherein said hydrogenation catalyst is soluble in said feed in liquid form.

8. A process according to any one of the preceding claims, characterized in that said feed (103) comprises unsaturated hydrocarbon compounds selected from olefinic, linear, branched or cyclic hydrocarbons, or from hydrocarbons comprising at least one aromatic ring.

9. A process according to claim 8, wherein said unsaturated hydrocarbon compounds are selected from butadiene, cyclododecatriene, vinylacetylene, cyclopentadiene, butene, cyclopentene, benzene, alkylbenzenes, phenol and its derivatives, alkyl diphenyls, alkylnaphthalenes, in particular toluene, dibenzyltoluene, xylenes, methyl naphthalene, N-ethylcarbazole, benzonitrile, unsaturated fatty oils and ethyl linoleate.

10. A process according to any one of claims 8 or 9, wherein said unsaturated hydrocarbon compounds are toluene.

11. A method according to any one of the preceding claims, wherein said impurities contained in the hydrogen (101) supplied in step a) are selected from water, oxygenated organic compounds or dioxygen.

12. A process according to the preceding claim, wherein when said impurity contained in the hydrogen (101) is water, the water content is between 1 and 3,000 ppm by volume relative to the total volume of hydrogen to be treated

13. A method according to any one of the preceding claims, wherein in step a) said adsorbent is selected from molecular sieves of type 3A, 4A, 5A, and 13X, activated aluminas, silica gels, used alone or in combination.

14. A method according to any one of the preceding claims, wherein the hydrogen treatment section (3a, 3b) comprises two adsorption columns.

15. A method according to the preceding claim, wherein one of the columns is implemented in step a) of the method and the other column is implemented in step e) of the method according to the invention.

16. A method according to any one of the preceding claims, wherein step e) is carried out periodically.

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