DE102016224063A1 - Process for the preparation of butadiene - Google Patents

Abstract

The invention relates to a process for the preparation of butadiene from compositions which contain butane, preferably n-butane and optionally additionally also significant amounts of butene. After non-oxidative catalytic dehydrogenation (2) and oxidative dehydrogenation (4), butadiene, butene, and butane are separated. Butene is attributed to oxidative dehydrogenation (4) and butane to non-oxidative catalytic dehydrogenation (2).

Description

The invention relates to a process for the preparation of butadiene from compositions comprising butane, preferably n-butane, and optionally additionally also significant amounts of butene, preferably n-butene (1-butene and / or 2-butene, cis and / or trans ) contain. After non-oxidative catalytic dehydrogenation and oxidative non-catalytic and / or catalytic dehydrogenation, the desired product butadiene as well as not or not fully reacted butene, butane and low-boiling by-products are separated from each other. Butene is attributed to oxidative dehydrogenation and butane to non-oxidative catalytic dehydrogenation.

Conventional industrial processes for the production of butadiene include the non-oxidative catalytic dehydrogenation of n-butane. However, in addition to hydrogen and butadiene, considerable amounts of incompletely reacted butene, in particular 2-butene, and considerable amounts of unreacted n-butane are produced in the product stream. To improve the yield of butadiene, these product streams are therefore often subjected to subsequent oxidative dehydrogenation, whereby butene and previously unreacted butane are oxydehydrated to butadiene. Nevertheless, this procedure is not complete, so that in the final product, where appropriate, in addition to hydrogen, carbon oxides, volatile by-products and water vapor always not inconsiderable amounts of not further dehydrogenated butene and unreacted butane are included, each representing a valuable raw material.

Processes for the preparation of butadiene by non-oxidative catalytic dehydrogenation of n-butane and subsequent oxydehydrogenation are known in which unconverted n-butane is separated off from butadiene and subsequently recycled to non-oxidative catalytic dehydrogenation (cf., for example, US Pat WO 2004/007408 A1 . WO 2005/063656 A1 . WO 2005/063657 A1 . WO 2005/063658 A1 . WO 2006/050969 A1 . WO 2006/061202 A1 . WO 2006/066848 A1 and WO 2006/075025 A1 ).

In the WO 2004/007408 A1 For example, the procedure is initially such that a non-oxidative catalytic dehydrogenation takes place and the first product gas stream obtained is then subjected to oxidative dehydrogenation in a second dehydrogenation zone to obtain a second product gas stream which, in addition to butadiene, also contains n-butane and 1-butene and 2-butene. Butadiene is then recovered from this second product gas stream. The n-butane and the butenes are thereby separated from a butadiene-containing stream and a stream containing both the n-butane and the butenes is then optionally recycled to the non-oxidative catalytic dehydrogenation.

The known processes have the disadvantage that the non-oxidative catalytic dehydrogenation stage is already subjected to considerable volumetric flows of incompletely butadiene-reacted C ₄ hydrocarbons. This is especially true when the educt added to the process already contains significant amounts of n-butene in addition to n-butane.

There is a need for processes for producing butadiene which overcome the disadvantages of the prior art. An object of the invention is therefore to provide an improved process for the production of butadiene.

This object is solved by the subject matter of the claims.

1. (a) nicht-oxidatives katalytisches Dehydrieren einer Zusammensetzung enthaltend Butan unter Erzeugung einer Zusammensetzung A enthaltend Butadien, Buten und Butan;
2. (b) oxidatives nicht katalytisches und/oder katalytisches Dehydrieren von in Zusammensetzung A enthaltenem Buten und Butan, unter Erzeugung einer Zusammensetzung B enthaltend Butadien, Buten und Butan;
3. (c) Trennen der Zusammensetzung B in eine an Butadien angereicherte Zusammensetzung C1 und eine an Butadien abgereicherte Zusammensetzung C2;
4. (d) Trennen der Zusammensetzung C2 in eine an Buten angereicherte Zusammensetzung D1 und eine an Butan angereicherte Zusammensetzung D2 und
5. (e) Rückführen der Zusammensetzung D1 zu Schritt (b) sowie Rückführen der Zusammensetzung D2 zu Schritt (a).

A first aspect of the invention relates to a process for the preparation of butadiene (ie of 1,3-butadiene) from butane, preferably from n-butane, comprising the steps:

1. (a) non-oxidative catalytic dehydrogenation of a composition containing butane to produce a composition A containing butadiene, butene and butane;
2. (b) oxidatively non-catalytic and / or catalytic dehydrogenation of butene and butane contained in composition A to produce a composition B containing butadiene, butene and butane;
3. (c) separating the composition B into a butadiene-enriched composition C1 and a butadiene-depleted composition C2;
4. (d) separating the composition C2 into a butene-enriched composition D1 and a butane-enriched composition D2 and
5. (e) recycling the composition D1 to step (b) and recycling the composition D2 to step (a).

The process according to the invention has the advantage that it is also possible to use hydrocarbon mixtures which contain significant amounts of n-butene in addition to n-butane without unnecessarily loading the non-oxidative catalytic dehydrogenation stage. For the non-oxidative dehydrogenation (a), this results in advantages in terms of the required size, the amount of catalyst and the need for steam and heating energy. In addition, due to the lower proportion of n-butene in the starting material to step (a) according to the principle of Le Chatelier a higher conversion of n-butane to n-butene expected. By the separation of n-butane and n-butene, the latter can instead be fed directly to the oxidative dehydrogenation step.

A preferred development of the process according to the invention provides that (b ') butane and butene still contained in composition B are oxidatively dehydrogenated, and butene optionally present in composition D1 is oxidatively dehydrogenated to produce a composition B' comprising butadiene, butene and butane and separating the composition B 'into a butadiene-enriched composition C1 and a butadiene-depleted composition C2.

A further preferred development of the method according to the invention provides that
(c ') combining the composition C2 with a composition C' containing fresh butane and fresh butene to form a composition C2 ', and
the composition C2 'is separated into a butene-enriched composition D1 and a butane-enriched composition D2 and
the composition D1 is recycled to step (b ') and the composition D2 is recycled to step (a).

Steps (b ') and (c') of the method according to the invention are optional, i. may independently or independently of the method comprise or not be included. The dehydrogenation of butene contained in a composition D1 in steps (b) and (b ') of the process according to the invention is also optionally independent, wherein the composition D1 is separated in step (d) and in step (e) to step (b) or (b ') is returned.

Steps (a), (b), optionally (b '), (c), optionally (c'), (d) and (e) of the process according to the invention are preferably carried out in alphabetical order, the steps not being directly adjacent to one another must follow, ie if necessary, further steps can be carried out between the individual steps.

Unless expressly stated, the term "butane" according to the invention relates in particular to n-butane, to the implementation of which the process according to the invention is directed. The isomeric iso-butane, however, is to be regarded as an undesirable impurity.

Unless expressly stated, the term "butene" according to the invention relates in particular to n-butene, in particular 1-butene and 2-butene (cis / trans), to the (further) implementation of the inventive method is directed. The isomeric isobutene, however, is to be regarded as an undesired impurity.

Unless expressly stated, the term "butadiene" according to the invention relates in particular to 1,3-butadiene, to the preparation of which the process according to the invention is directed. The isomeric 1,2-butadiene, however, is to be regarded as an undesirable by-product.

In step (a) of the process of the invention, a composition containing butane is non-oxidatively catalytically dehydrogenated to produce a composition A which contains butadiene, not (fully) reacted butene and unreacted butane. The composition containing butane preferably contains butane substantially as n-butane.

According to the invention, the source of the composition containing butane is preferably a hydrocarbon mixture rich in n-butane, for example liquefied petroleum gas (LPG). In addition to methane and traces of C ₆ + hydrocarbons, LPG contains substantially saturated C ₂ -C ₅ hydrocarbons. The composition of LPG can vary widely. The hydrocarbon mixture used according to the invention preferably contains at least 10% by weight of butanes (n-butane, isobutane). Alternatively, a C ₄ stream of crackers or refineries can be used as a source.

• (a-1) Bereitstellen einer Kohlenwasserstoffzusammensetzung, vorzugsweise einer Liquefied Petroleum Gas (LPG)-Zusammensetzung; und/oder
• (a-2) Abtrennen von Propan und ggf. Methan, Ethan und C₅₊-Kohlenwasserstoffen (insbesondere Pentane, Hexane, Heptane, Benzol, Toluol) von der Kohlenwasserstoffzusammensetzung, wobei die Zusammensetzung enthaltend Butan erhalten wird (n-Butan und iso-Butan); und/oder
• (a-3) ggf. Abtrennen von iso-Butan aus der Zusammensetzung enthaltend Butan, wobei eine Zusammensetzung enthaltend im Wesentlichen n-Butan erhalten wird; und/oder
• (a-4) ggf. Isomerisieren des abgetrennten iso-Butans zu einem n-Butan/iso-Butan-Gemisch und Rückführung des n-Butan/Isobutan-Gemischs in Schritt (a-3); und/oder
• (a-5) ggf. Umsetzung von iso-Buten aus der Zusammensetzung enthaltend Butan zu Methyl-tert.-butylether durch chemische Reaktion mit zuzugebendem Methanol, und Abtrennen des gebildeten Methyl-tert.-butylether von Kohlenwasserstoffen durch Rektifikation.

In a preferred embodiment of the process according to the invention, step (a) initially comprises the preparation of the composition which comprises butane, preferably n-butane, preferably the following substeps being carried out:

• (a-1) providing a hydrocarbon composition, preferably a liquefied petroleum gas (LPG) composition; and or
• (a-2) separating propane and optionally methane, ethane and C ₅₊ -hydrocarbons (in particular pentanes, hexanes, heptanes, benzene, toluene) from the hydrocarbon composition, the composition comprising butane being obtained (n-butane and isobutane). Butane); and or
• (a-3) optionally separating iso-butane from the composition containing butane to obtain a composition containing substantially n-butane; and or
• (a-4) optionally isomerizing the separated iso-butane to an n-butane / iso-butane mixture and recycling the n-butane / isobutane mixture in step (a-3); and or
• (a-5) if appropriate reaction of isobutene from the composition comprising butane to methyl tert-butyl ether by chemical reaction with methanol to be added, and separating the formed methyl tert-butyl ether of hydrocarbons by rectification.

Suitable measures for separating propane and possibly methane, ethane and C ₅ + hydrocarbons in step (a-2) are known to a person skilled in the art, for example rectification in conventional rectification columns. For example, in a first rectification column low boilers (methane, ethane, propane) can be separated overhead and in a second rectification column high boilers (C ₅ + hydrocarbons) at the bottom of the column. In this way, a composition containing butane is obtained, the butane usually comprising both n-butane and iso-butane. Suitable measures for separating iso-butane in step (a-3) are also known to a person skilled in the art, for example rectification in a conventional rectification column. The remaining composition containing substantially n-butane is then preferably used as starting material of the subsequent non-oxidative catalytic dehydrogenation in step (a). The iso-butane separated in the step (a-3) is preferably subjected to isomerization in the step (a-4). For this purpose, the isobutane is fed into a conventional isomerization reactor and the resulting n-butane / isobutane mixture is recycled to step (a-3). Alternatively, the separated iso-butane can be put to another use, for example, the production of methacrylic acid, polyisobutene or methyl tert-butyl ether. Suitable measures for the conversion of isobutene in step (a-5) to methyl tert-butyl ether are known to a person skilled in the art, for example chemical reaction with methanol and subsequent separation of methyl tert-butyl ether from hydrocarbons in a rectification column.

In another preferred embodiment of the process according to the invention, in step (a) the composition comprising butane is not freshly prepared from the outside as starting material, but comes from the composition D2 recycled in step (e) to step (a).

The composition containing butane is then non-oxidatively catalytically dehydrogenated to produce a composition A containing butadiene, not (fully) reacted butene, especially n-butene, and unreacted butane, especially n-butane. The butene usually comprises 1-butene and 2-butene. Furthermore, the composition contains H ₂ , which is released by the dehydrogenation, and low-boiling secondary constituents, in particular methane, ethane, ethene, propane and propene. Depending on the reaction procedure, composition A may also contain carbon oxides (CO, CO ₂ ) and water vapor.

The type and respective content of the ingredients contained in Composition A can vary widely depending on the type of dehydration. Thus, in preferred autothermal dehydrogenation with the introduction of oxygen, the gas mixture produced has a comparatively high content of water vapor and carbon oxides. In reactions without feed of oxygen, composition A has a comparatively high content of hydrogen.

Composition A typically contains 0.1 to 15% by volume of butadiene, 1 to 20% by volume of 1-butene, 1 to 35% by volume of 2-butene (cis / trans-2-butene), 20 to 80% by volume % n-butane, 0 to 70% by volume of steam, 0 to 10% by volume of low-boiling hydrocarbons (methane, ethane, ethene, propane and propene), 0 to 40% by volume of hydrogen, 0 to 70 vol % Nitrogen and 0 to 15% by volume carbon oxides.

The non-oxidative catalytic dehydrogenation according to the invention can in principle be carried out in all reactor types known from the prior art and in accordance with all known reaction methods. The non-oxidative catalytic dehydrogenation can be carried out according to the invention with or without oxygen-containing gas. Suitable reactors include fixed bed tube or tube bundle reactors. The dehydrogenation catalyst used is preferably platinum containing promoters on zinc (magnesium) spinel as carrier. The butane to be dehydrated is preferably diluted with steam (STAR process). Typical is a molar ratio of steam to butane in the range of 0 to 6. The reactor outlet pressure is often 2 to 10 bar and the reaction temperature is preferably 480 to 620 ° C.

In a preferred embodiment of the process according to the invention, the non-oxidative catalytic dehydrogenation in step (a) is carried out autothermally. For this purpose, the composition containing butane is additionally mixed with oxygen in at least one reaction zone. The hydrogen and / or hydrocarbon contained in the reaction gas mixture is at least partially combusted, whereby at least part of the required reaction energy in the at least one reaction zone is generated directly in the reaction gas mixture. Preferably, the total amount of oxygen supplied, based on the total amount of butane, 0.001 to 0.5 mol / mol, preferably 0.005 to 0.2 mol / mol, particularly preferably 0.05 to 0.2 mol / mol. Oxygen can be used either as pure oxygen or as an oxygen-containing gas mixed with inert gases, for example in the form of air. The heat generation Burned hydrogen is the hydrogen formed in the non-oxidative catalytic dehydrogenation and possibly additionally added hydrogen. The hydrogen combustion takes place catalytically, wherein the dehydrogenation catalyst used generally also catalyzes the combustion of the hydrocarbons and of hydrogen with oxygen, so that in principle no special oxidation catalyst different from this one is required. In a preferred embodiment, the reaction is carried out in the presence of one or more oxidation catalysts which selectively catalyze the combustion of hydrogen to oxygen in the presence of hydrocarbons. The combustion of these hydrocarbons with oxygen to CO, CO ₂ and water is therefore only to a minor extent. Preferably, the dehydrogenation catalyst and the oxidation catalyst are present in different reaction zones.

According to the invention, it is possible to add further non-oxidative catalytic dehydrogenations as steps (a '), (a "), (a' ''), etc., before the product of the last step of the non-oxidative catalytic dehydrogenation reaches the subsequent step ( b) is supplied.

In step (b) of the process according to the invention, butene and, to a lesser extent, butane, which are contained in composition A, are oxidatively dehydrated (oxydehydrogenated) to produce a composition B which contains butadiene, not fully reacted butene and not contains reacted butane, optionally in addition to low-boiling secondary constituents, carbon oxides and water vapor, wherein the content of butadiene in composition B is preferably higher than in composition A. The oxidative dehydrogenation is preferably carried out both non-catalytically and catalytically, ie both processes run in parallel.

Preferably, step (b) is carried out autothermally with the introduction of an oxygen-containing gas, wherein the oxygen-containing gas is preferably air. Depending on the amount of oxygen supplied, step (b) will be exothermic, dissipating heat.

Composition A can preferably be separated into two substreams, wherein only one of the two substreams is subjected to the further steps (b) to (e) of the process according to the invention and the other of the two substreams is recycled for nonoxidative catalytic dehydrogenation in step (a) , However, it is also possible to completely supply composition A to the oxidative dehydrogenation according to step (b).

The oxidative dehydrogenation (oxydehydrogenation) can in principle be carried out in all reactor types, catalysts and reaction methods known from the prior art. To carry out the oxidative dehydrogenation, a gas mixture is required which has a molar oxygen: n-butene ratio of at least 0.5. In order to set this value, the product gas mixture originating from the non-oxidative catalytic dehydrogenation is generally mixed with oxygen or an oxygen-containing gas, for example air. The resulting oxygen-containing gas mixture is then fed to the oxydehydrogenation. The oxydehydrogenation is generally carried out at a temperature of 220 to 490 ° C.

In addition to butadiene and unreacted n-butane, composition B, which is produced in step (b), usually does not yet contain (fully) reacted 2-butene and water vapor. The content of 1-butene in composition B is often only small. As minor constituents, composition B usually contains CO, CO ₂ , O ₂ , N ₂ , methane, ethane, ethene, propane and propene, optionally hydrogen and oxygen-containing hydrocarbons (oxygenates), for example aldehydes.

Composition B typically contains from 1 to 50% by volume of butadiene (but preferably more than Composition A), from 20 to 80% by volume of n-butane, from 0.5 to 40% by volume of 2-butene, from 0 to 20% by volume. % 1-butene, 0 to 70% by volume of steam, 0 to 10% by volume of low-boiling hydrocarbons (methane, ethane, ethene, propane and propene), 0 to 40% by volume of hydrogen, 0 to 70 vol. % Nitrogen, 0 to 10% by volume of carbon oxides and 0 to 10% by volume of oxygenates.

In optional step (b ') of the process of the invention, preferably butene and butane contained in composition B are oxidatively dehydrated to produce a composition B' containing butadiene, not (fully) reacted butene and unreacted butane the content of butadiene in composition B 'is preferably higher than in composition B. In this variant of the process according to the invention, two oxidative dehydrogenations are thus carried out in succession, whereby the overall yield of butadiene can be increased overall.

Preferably, step (b ') is also carried out autothermally with the introduction of an oxygen-containing gas, wherein the oxygen-containing gas is preferably air.

According to the invention it is possible to add further oxidative dehydrogenations as steps (b "), (b '' '), etc., before the product of the last step of the oxydehydrogenation is fed to the subsequent step (c).

In step (c) of the process according to the invention, composition B or, if the process according to the invention comprises optional step (b '), composition B', preferably after removal of non-C ₄ components, into a butadiene-enriched composition C 1 and a butadiene depleted composition C2 separated. In this case, the butadiene contained in composition C1 is preferably the main constituent of all C ₄ constituents in the composition C1.

• (c-1) Abkühlen; und/oder
• (c-2) Verdichten; und/oder
• (c-3) Abtrennen leichtflüchtiger Nebenprodukte; und/oder
• (c-4) Umsetzung von iso-Buten aus der Zusammensetzung C zu Methyl-tert.-butylether durch chemische Reaktion mit zuzugebendem Methanol, und Abtrennen des gebildeten Methyl-tert.-butylether von Kohlenwasserstoffen durch Rektifikation.

Preferably, step (c) of the method according to the invention comprises, before separating Compositions C1 and C2, one or more of the following preceding substeps

• (c-1) cooling; and or
• (c-2) compacting; and or
• (c-3) separation of volatile by-products; and or
• (c-4) reaction of isobutene from the composition C to methyl tert-butyl ether by chemical reaction with methanol to be added, and separation of the formed methyl tert-butyl ether of hydrocarbons by rectification.

In step (c3), the low-boiling minor constituents other than the C ₄ hydrocarbons (n-butane, isobutane, 1-butene, cis / trans-2-butene, isobutene, butadiene) become at least partly, but preferably essentially completely separated from composition B to obtain a composition C containing C ₄ hydrocarbons, which is then subsequently separated into composition C1 and composition C2.

Preferably, first of all water is separated off from composition B, for example by condensation after cooling in step (c-1) and / or compression in step (c-2). The separation of the low-boiling by-products in step (c-3) can be carried out by conventional separation methods such as distillation, rectification, membrane process, absorption or adsorption. To separate the hydrogen contained in composition B, composition B, if appropriate after cooling, for example in an indirect heat exchanger, can be passed over a membrane which is permeable only to molecular hydrogen. If necessary, the molecular hydrogen thus separated can be used at least partially in the dehydrogenation or else sent for other recycling. The carbon dioxide contained in Composition B can be separated by CO ₂ scrubbing. The CO ₂ scrubbing can be preceded by a separate combustion stage in which CO is selectively oxidized to CO ₂ .

In a preferred embodiment of the process according to the invention, composition B is compressed in at least one first compression stage and then cooled, condensing at least one water-containing condensate and a gaseous composition containing n-butane, n-butene, butadiene, hydrogen, water vapor, optionally carbon oxides and if necessary, inert gases remain. Steps (c-1) and (c-2) can therefore be carried out in reverse order. The compression can be done in one or more stages. Overall, it is preferred to compress from a pressure in the range from 1.0 to 4.0 bar to a pressure in the range from 3.5 to 20 bar. After each compression stage, preferably followed by a cooling step, in which the gaseous composition is cooled to a temperature in the range of preferably 15 to 60 ° C. The gaseous composition essentially comprises C ₄ hydrocarbons (n-butane, n-butene and butadiene), H ₂ , CO ₂ and water vapor. In addition, the gaseous composition may still contain low boilers, inert gases (N ₂ ) and CO as further secondary components. The aqueous condensate preferably contains at least 80% by weight of water and, in addition, minor amounts of low boilers, C ₄ hydrocarbons, oxygenates and CO ₂ .

In a preferred embodiment of the method according to the invention are the non-condensable or low-boiling gas components such as H ₂ , O ₂ , CO, CO ₂ , the low-boiling hydrocarbons (methane, ethane, ethene, propane, propene) and optionally N ₂ in an absorption / Desorptions-Cyclus separated by means of an absorbent, wherein composition C is obtained, the content of C ₄ hydrocarbons preferably at least 80 vol .-%, more preferably at least 90 vol .-%, particularly preferably at least 95 vol .-%. For this purpose, composition B is brought into contact after prior removal of water with an inert absorbent in which the C ₄ hydrocarbons are absorbed, wherein C ₄ hydrocarbons laden absorbent and an exhaust gas containing the remaining constituents are obtained. In a desorption step, the C ₄ hydrocarbons are released from the absorbent again. For desorption, the loaded absorbent is heated and / or released to a lower pressure. Alternatively, the desorption may also be by stripping or in a combination of relaxation, heating and stripping in one or more process steps. The absorbent regenerated in the desorption stage is returned to the absorption stage. Suitable absorbents are high-boiling solvents in which the C ₄ - Hydrocarbon mixture has a significantly higher solubility than the other gas components.

Composition C preferably contains 20 to 80% by volume of butadiene, 20 to 80% by volume of n-butane, 0 to 50% by volume of 2-butene and 0 to 20% by volume of 1-butene.

Composition C may still contain small amounts of oxygen. If composition C contains more than just traces of oxygen, it is preferred to carry out a process stage for removing residual oxygen. Preferably, the oxygen removal is performed immediately after the oxidative dehydrogenation. For this purpose, a catalytic combustion stage is preferably carried out in which oxygen is reacted with the hydrogen contained in the composition in the presence of a catalyst. Suitable catalysts are known to a person skilled in the art. As a result, a reduction in the oxygen content is achieved down to a few traces. If the residual oxygen removal is carried out after the absorption / desorption stage, hydrogen or hydrogen-containing gas must be added to the composition.

The separation of composition B, B 'or C into the butadiene-enriched composition C1 and the butadiene-depleted composition C2 can be carried out in a conventional manner. Suitable measures are known to the person skilled in the art.

Preferably, step (c) of the method according to the invention comprises an extraction for this purpose. For this purpose, the mixture of composition C to be separated is mixed with a suitable solvent, which is as little as possible with butane and butene, with butadiene miscible. The heterogeneous liquid mixture of the butane / butene rich raffinate phase and the extract phase containing the solvent and butadiene is mechanically separated. Suitable devices for the mechanical separation of two liquid phases are known to a person skilled in the art. The extract phase can be separated, for example, by rectification in a rectification column in butadiene and solvent. The separated solvent can be returned to the extraction process.

Alternatively, step (c) of the process according to the invention comprises an extractive rectification. For this purpose, the mixture to be separated Composition C with a suitable low volatility additive which increases the boiling point of butadiene in admixture with the excipient, the boiling points of butane and butene on the other hand as little as possible, added. Suitable devices for the separation of butane / butene from the less volatile mixture of butadiene and the auxiliary, for example in an extractive rectification column, as well as the separation of butadiene from the less volatile auxiliary in a rectification column, are known in the art. The separated excipient can be returned to the extractive rectification process.

In optional step (c ') of the process according to the invention, composition C2 is preferably combined with a composition C' which contains fresh butane and fresh butene, producing a composition C2 '.

Preferably, in step (c ') the fresh butane is essentially n-butane and / or the fresh butene is essentially linear butene (n-butene).

In a preferred embodiment of the process according to the invention, step (c ') is not included and in step (a) the composition comprising butane as starting material, preferably from liquefied petroleum gas (LPG), is provided. Thus, in this preferred embodiment, fresh hydrocarbons as a composition containing butane are introduced into the process from the outside in step (a). The composition D2 recycled in step (e) to step (a) then contains essentially unreacted butane (educt), which has already passed through steps (a) to (c). Analogously, the composition D1 recycled in step (e) to step (b) or (b ') then contains substantially incompletely reacted butene, which has already passed through steps (a) to (c).

In another preferred embodiment of the process according to the invention, the composition C 'containing fresh butane and fresh butene as starting material, preferably from liquefied petroleum gas (LPG), is provided in step (c') and in step (a) the composition containing butane is added in Form of composition D2 provided by step (e). Thus, in this preferred embodiment, fresh hydrocarbons are introduced into the process as composition C 'in step (c'). The composition D2 recycled in step (e) to step (a) contains, on the one hand, fresh butane, which has not yet passed through steps (a) to (c), and, on the other hand, unreacted butane, which comprises the steps (a) to ( c) has already passed through before. Analogously, the composition D1 recycled in step (e) to step (b) or (b ') then contains, on the one hand, fresh butene, which has not yet undergone steps (a) to (c), and, on the other hand, unreacted butene, which has already passed through the steps (a) to (c).

A person skilled in the art will recognize that preferably both embodiments can be combined with each other, so that two different Educts are fed from the outside in two different steps of the process according to the invention, fresh n-butane in step (a) and fresh n-butane / n-butene in step (c ').

In step (d) of the process according to the invention, composition C2 or, if the process according to the invention comprises optional step (c '), composition C2' is separated into a butene-enriched composition D1 and a butane-enriched composition D2.

Preferably, in step (d), the butene contained in composition D1 is the major constituent of all C ₄ constituents in the composition D1; and / or the butane contained in composition D2 is the main constituent of all C ₄ constituents in composition D2.

Preferably, step (d) of the process according to the invention comprises an extractive rectification. For this purpose, the mixture to be separated composition C2 or C2 'with a suitable low-volatility additive which increases the boiling point of the butene in a mixture with this excipient, the boiling point of butane on the other hand, as little as possible, added. Suitable methods for the separation of butane from the less volatile mixture of butene and the excipient, for example in an extractive rectification column, and the separation of butene from the less volatile adjuvant in a rectification column are known in the art. As an excipient N-formylmorpholine or a mixture with other substances, in particular morpholine or other morpholine derivatives can be used.

Preferably, the butene-enriched composition D1 contains from 50 to 100% by volume of n-butene and from 0 to 10% by volume of other ingredients such as e.g. 1,2-butadiene, isobutene, propane, and propene.

Preferably, the butane-enriched composition D2 contains from 50 to 100% by volume of n-butane and from 0 to 10% by volume of further ingredients such as e.g. Isobutene, propane, and propene.

In step (e) of the process according to the invention, composition D1 is recycled to step (b) or, if the process according to the invention comprises optional step (b '), alternatively to step (b) or (b'), i. for oxydehydrogenation, and composition D2 is recycled to step (a), i. for non-oxidative catalytic dehydrogenation.

In this way, the non-oxidative catalytic dehydrogenation stage is relieved, since the (recovered) recovered, separated butene is fed directly to the Oxydehydrierungsstufe.

1. (a) eine Dehydriervorrichtung (2) zum nicht-oxidativen katalytischen Dehydrieren einer Zusammensetzung enthaltend Butan unter Erzeugung einer Zusammensetzung A enthaltend Butadien, Buten und Butan;
2. (b) eine Oxydehydriervorrichtung (4) zum oxidativen nicht katalytischen und/oder katalytischen Dehydrieren von in Zusammensetzung A enthaltenem Buten und Butan, sowie in Zusammensetzung D1 enthaltenem Buten unter Erzeugung einer Zusammensetzung B enthaltend Butadien, Buten und Butan;
3. (c) eine Trennvorrichtung (11) zum Trennen der Zusammensetzung B in eine an Butadien angereicherte Zusammensetzung C1 und eine an Butadien abgereicherte Zusammensetzung C2;
4. (d) eine weitere Trennvorrichtung (15) zum Trennen der Zusammensetzung C2 in eine an Buten angereicherte Zusammensetzung D1 und eine an Butan angereicherte Zusammensetzung D2; und
5. (e) Mittel (16) zum Rückführen der Zusammensetzung D1 zur Oxydehydriervorrichtung (4) oder Mittel (16') zum Rückführen der Zusammensetzung D1 zur weiteren Oxydehydriervorrichtung (4'); sowie Mittel (17) zum Rückführen der Zusammensetzung D2 zur Dehydriervorrichtung (2).

A further aspect of the invention relates to an apparatus for producing butadiene from butane comprising the elements which are in operative connection with one another:

1. (a) a dehydrogenating device (2) for non-oxidative catalytic dehydrogenation of a composition containing butane to produce a composition A containing butadiene, butene and butane;
2. (b) an oxydehydrogenator (4) for the oxidative non-catalytic and / or catalytic dehydrogenation of butene and butane contained in composition A, and butene contained in composition D1 to produce a composition B containing butadiene, butene and butane;
3. (c) a separation device (11) for separating the composition B into a butadiene-enriched composition C1 and a butadiene-depleted composition C2;
4. (d) another separation device (15) for separating the composition C2 into a butene-enriched composition D1 and a butane-enriched composition D2; and
5. (e) means (16) for returning the composition D1 to the oxydehydrogenating device (4) or means (16 ') for returning the composition D1 to the further oxydehydrogenating device (4'); and means (17) for returning the composition D2 to the dehydrating device (2).

• (a) eine Dehydriervorrichtung zum nicht-oxidativen katalytischen Dehydrieren einer Zusammensetzung enthaltend Butan unter Erzeugung einer Zusammensetzung A enthaltend Butadien, Buten und Butan; wobei die Dehydriervorrichtung (2) vorzugsweise eine oder mehrere der vorgeschalteten Komponenten (a-1) bis (a-5) umfasst:
  • (a-1) eine Vorrichtung zur Bereitstellung einer Kohlenwasserstoffzusammensetzung; und/oder
  • (a-2) eine Vorrichtung zur Abtrennung von Propan und ggf. Methan, Ethan und C5+-Kohlenwasserstoffen (insbesondere Pentane, Hexane, Heptane, Benzol, Toluol) von der Kohlenwasserstoffzusammensetzung; und/oder
  • (a-3) eine Vorrichtung zur Abtrennung von iso-Butan aus der Zusammensetzung enthaltend Butan; und/oder
  • (a-4) eine Vorrichtung zur Isomerisierung des abgetrennten iso-Butans zu einem n-Butan/iso-Butan-Gemisch und Rückführung des n-Butan/Isobutan-Gemischs in Schritt (a-3); und/oder
  • (a-5) eine Vorrichtung zur chemischen Umsetzung von iso-Buten zu Methyl-tert.-butylether mit zuzugebendem Methanol, und Vorrichtung zur Abtrennung des gebildeten Methyl-tert.-butylether von Kohlenwasserstoffen;
• (b) eine Oxydehydriervorrichtung zum oxidativen, vorzugsweise nicht katalytischen und/oder katalytischen Dehydrieren von in Zusammensetzung A enthaltenem Buten und Butan unter Erzeugung einer Zusammensetzung B enthaltend Butadien, Buten und Butan;
• (b') ggf. eine weitere Oxydehydriervorrichtung zum oxidativen Dehydrieren von in Zusammensetzung B enthaltenem Butan und Buten unter Erzeugung einer Zusammensetzung B' enthaltend Butadien, Buten und Butan;
• (c) eine Trennvorrichtung zum Trennen der Zusammensetzung B bzw. B' in eine an Butadien angereicherte Zusammensetzung C1 und eine an Butadien abgereicherte Zusammensetzung C2; wobei die Trennvorrichtung (11) vorzugsweise eine oder mehrere der vorgeschalteten Komponenten (c-1) bis (c-4) umfasst:
  • (c-1) eine Vorrichtung zur Abkühlung der Zusammensetzung B bzw. B' und/oder C1 und/oder C2; und/oder
  • (c-2) eine Vorrichtung zur Verdichtung der Zusammensetzung B bzw. B' und/oder C1 und/oder C2; und/oder
  • (c-3) eine Vorrichtung zur Abtrennung leichtflüchtiger Nebenprodukte; und/oder
  • (c-4) eine Vorrichtung zur chemischen Umsetzung von iso-Buten zu Methyl-tert.-butylether mit zuzugebendem Methanol, und Vorrichtung zur Abtrennung des gebildeten Methyl-tert.-butylethers von Kohlenwasserstoffen;
• (d) eine weitere Trennvorrichtung zum Trennen der Zusammensetzung C2 in eine an Buten angereicherte Zusammensetzung D1 und eine an Butan angereicherte Zusammensetzung D2; und
• (e) Mittel zum Rückführen der Zusammensetzung D1 zur Oxydehydriervorrichtung oder Mittel zum Rückführen der Zusammensetzung D1 zur weiteren Oxydehydriervorrichtung; sowie Mittel zum Rückführen der Zusammensetzung D2 zur Dehydriervorrichtung.

According to a preferred development of the invention, the device comprises the following elements which are in operative connection with one another:

• (a) a dehydrogenating apparatus for non-oxidative catalytic dehydrogenation of a composition containing butane to produce a composition A containing butadiene, butene and butane; wherein the dehydrogenating device (2) preferably comprises one or more of the upstream components (a-1) to (a-5):
  • (a-1) an apparatus for providing a hydrocarbon composition; and or
  • (a-2) an apparatus for separating propane and optionally methane, ethane and C5 + hydrocarbons (especially pentanes, hexanes, heptanes, benzene, toluene) from the hydrocarbon composition; and or
  • (a-3) an apparatus for separating iso-butane from the composition containing butane; and or
  • (a-4) an apparatus for isomerizing the separated isobutane to an n-butane / iso-butane mixture and recycling the n-butane / isobutane mixture in step (a-3); and or
  • (a-5) an apparatus for chemically reacting isobutene to methyl tert-butyl ether with methanol to be added, and apparatus for separating the formed methyl tert-butyl ether from hydrocarbons;
• (b) an oxydehydrogenation apparatus for the oxidative, preferably non-catalytic and / or catalytic dehydrogenation of butene and butane contained in composition A to produce a composition B containing butadiene, butene and butane;
• (b ') optionally, another oxydehydrogenating apparatus for oxidatively dehydrating butane and butene contained in Composition B to produce a composition B' containing butadiene, butene and butane;
• (c) a separation device for separating the composition B or B 'into a butadiene-enriched composition C1 and a butadiene-depleted composition C2; wherein the separation device (11) preferably comprises one or more of the upstream components (c-1) to (c-4):
  • (c-1) a device for cooling the composition B or B 'and / or C1 and / or C2; and or
  • (c-2) a device for compressing the composition B or B 'and / or C1 and / or C2; and or
  • (c-3) an apparatus for separating volatile by-products; and or
  • (c-4) an apparatus for chemically reacting isobutene to methyl tert-butyl ether with methanol to be added, and apparatus for separating the formed methyl tert-butyl ether from hydrocarbons;
• (d) another separation device for separating the composition C2 into a butene-enriched composition D1 and a butane-enriched composition D2; and
• (e) means for recycling the composition D1 to the oxydehydrogenating device or means for returning the composition D1 to the further oxydehydrogenating device; and means for recycling the composition D2 to the dehydrogenating device.

The possibly existing further oxydehydrogenation device of the device according to the invention is preferred, but does not necessarily have to be present. The elements of the device according to the invention are in operative connection with each other, i. the device according to the invention comprises suitable means for transferring the compositions from one element to the next, for example suitable pipelines.

Preferably, the Oxydehydriervorrichtung and / or the further Oxydehydriervorrichtung are designed for autothermal oxidative dehydrogenation.

The separation device preferably comprises an extraction device or an extractive rectification device.

Preferably, the further separation device comprises an extractive rectification.

• - einen der Trennvorrichtung vorgeschalteten Wärmetauscher zum Abkühlen der Zusammensetzung B bzw. B'; und/oder
• - einen der Trennvorrichtung vorgeschalteten Kompressor zum Verdichten der ggf. zuvor im Wärmetauscher abgekühlten Zusammensetzung B bzw. B'.

The device according to the invention preferably comprises

• - One of the separator upstream heat exchanger for cooling the composition B or B '; and or
• - A separator upstream of the compressor for compressing the possibly previously cooled in the heat exchanger composition B or B '.

The heat exchanger may be upstream of the compressor or vice versa.

All preferred embodiments, which were described above in connection with the method according to the invention, apply analogously also with regard to the design and construction of the device according to the invention and are therefore not repeated in this respect.

The device according to the invention is particularly suitable for carrying out the method according to the invention. A further aspect of the invention therefore relates to the use of the device according to the invention for carrying out the method according to the invention.

The invention will be illustrated by way of example with reference to the figures. A person skilled in the art will recognize that, in the case of a device according to the invention, it is not absolutely necessary for all the imaged features to be realized simultaneously.

1 illustrates a device according to the invention, with the aid of which the inventive method can be performed. It is via line ( 1 ) a composition comprising butane of a dehydrogenating device ( 2 ) for non-oxidative catalytic dehydrogenation, in which a composition A containing butadiene, butene and butane is produced. Management ( 1 ) is partially shown in dashed lines, which is to express that either (i) via line ( 1 ) Fresh butane is supplied as educt from the outside, which is connected via line ( 17 ), or that (ii) via line ( 1 ) no fresh butane is supplied from the outside as starting material, but instead a mixture comprising butane and butene via line ( 14 ) (also shown in dashed lines) is supplied from the outside as a starting material, which with recycled butane / butene in line ( 13 ) and in separation device ( 15 ), with a butane-enriched composition via line ( 17 ) to the dehydrogenating device ( 2 ) to be led. Composition A leaves the dehydrating device ( 2 ) and is transmitted via line ( 3 ) an oxydehydrogenation device ( 4 ) for oxidative dehydrogenation in which a composition B containing butadiene, butene and butane is produced. For this purpose, air or another, oxygen-containing gas via line ( 5 ) of the oxydehydrogenation device ( 4 ). Composition B leaves the oxydehydrogenation device ( 4 ) via line ( 6 ) and is preferably used in a heat exchanger ( 7 ) and then via line ( 8th ) a compressor ( 9 ), in which the composition is compressed. Heat exchanger ( 7 ) and compressor ( 9 ) can also be arranged according to the invention in reverse order. The thus possibly cooled and compressed composition B is then passed via line ( 10 ) a separating device ( 11 ) for separation into a butadiene-enriched composition C1 and a butadiene-depleted composition C2. Preferably, separation device ( 11 ) an extraction device or an extractive rectification device. The butadiene-enriched composition C1 is added via line ( 12 ) discharged from the process as a desired product. The remaining, butadiene-depleted composition C2 is separated from separation device ( 11 ) via line ( 13 ) a further separating device ( 15 ) for separation into a butene-enriched composition D1 and a butane-enriched composition D2. Preferably, the further separation device ( 15 ) an extractive rectification device. It can be done first via line ( 14 ) a composition comprising fresh butane and fresh butene as starting material fed from the outside and in line ( 13 ) are mixed with the butadiene depleted composition C2. The butene-enriched composition D1 leaves the further separation device ( 15 ) and is transmitted via line ( 16 ) to the oxydehydrogenation device ( 4 ) returned. The butane enriched composition D2 also leaves the further separation device ( 15 ) and is transmitted via line ( 17 ) to the dehydrogenating device ( 2 ) returned.

2 illustrates a preferred alternative embodiment of the inventive device according to 1 , with the aid of which the method according to the invention can be carried out. In this case, a further Oxydehydriervorrichtung ( 4 ') serially the Oxydehydriervorrichtung ( 4 ) downstream. The butene-enriched composition D1, which in the further separation device ( 15 ) is preferably obtained by extractive distillation, can alternatively via line ( 16 ) to the oxydehydrogenation device ( 4 ) and / or via line ( 16 ') (indicated by dashed lines) to the Oxydehydriervorrichtung ( 4 ') to be led back.

LIST OF REFERENCE NUMBERS

management (1) dehydrating (2) management (3) Oxydehydriervorrichtung (4) Oxydehydriervorrichtung (4 ') management (5) management (5 ') management (6) heat exchangers (7) management (8th) compressor (9) management (10) separating device (11) management (12) management (13) management (14) (indicated by dashed lines) separating device (15) management (16) management (16 ') (indicated by dashed lines) management (17)

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2004/007408 A1 [0003, 0004]
• WO 2005/063656 A1 [0003]
• WO 2005/063657 A1 [0003]
• WO 2005/063658 A1 [0003]
• WO 2006/050969 A1 [0003]
• WO 2006/061202 A1 [0003]
• WO 2006/066848 A1 [0003]
• WO 2006/075025 A1 [0003]

Claims (21)

Process for the preparation of butadiene from butane comprising the steps (a) non-oxidative catalytic dehydrogenation of a composition containing butane to produce a composition A containing butadiene, butene and butane; (b) oxidatively non-catalytic and / or catalytic dehydrogenation of butene and butane contained in composition A to produce a composition B containing butadiene, butene and butane; (c) separating the composition B into a butadiene-enriched composition C1 and a butadiene-depleted composition C2; (d) separating the composition C2 into a butene-enriched composition D1 and a butane-enriched composition D2 and (e) recycling the composition D1 to step (b) and recycling the composition D2 to step (a). The procedure according to Claim 1 in which (b ') butane and butene contained in composition B are oxidatively dehydrated, and butene optionally contained in composition D1 is oxidatively dehydrogenated to produce a composition B' containing butadiene, butene and butane and the composition B 'in a butadiene-enriched one Composition C1 and a butadiene depleted composition C2 is separated. The procedure according to Claim 2 wherein (c ') the composition C2 is combined with a composition C' containing fresh butane and fresh butene to produce a composition C2 'and the composition C2' is separated into a butene-enriched composition D1 and a butane-enriched composition D2, and the composition D1 is recycled to step (b ') and the composition D2 is recycled to step (a). The procedure according to Claim 3 wherein - in step (a) the butane is substantially n-butane; and / or - in step (c ') the fresh butane is substantially n-butane and / or the fresh butene is substantially linear butene. The procedure according to Claim 3 or 4 wherein step (c ') is not included and in step (a) the composition comprising butane is provided as starting material; or - in step (c ') the composition C' containing fresh butane and fresh butene is provided as starting material and in step (a) the composition comprising butane is provided in the form of composition D2 from step (e). The process according to any one of the preceding claims, wherein - in step (c) the butadiene contained in composition C1 is the main constituent of all C ₄ constituents in the composition C1; and / or - in step (d) the butene contained in composition D1 is the main constituent of all C ₄ constituents in the composition D1; and / or the butane contained in composition D2 is the major constituent of all C ₄ constituents in the composition D2. The method of any one of the preceding claims, wherein step (c) comprises extraction or extractive rectification. The method of any one of the preceding claims, wherein step (d) comprises an extractive rectification. The procedure according to Claim 8 , wherein in the extractive distillation, an extractant is used, which comprises N-formylmorpholine or a mixture of N-formylmorpholine and morpholine or other morpholine derivatives. The process of any one of the preceding claims, wherein step (a) comprises one or more of the preceding substeps (a-1) providing a hydrocarbon composition; (a-2) separating propane and optionally methane, ethane and C ₅₊ -hydrocarbons (in particular pentanes, hexanes, heptanes, benzene, toluene) from the hydrocarbon composition, the composition comprising butane being obtained (n-butane and isobutane). Butane); and / or (a-3) separating iso-butane from the composition containing butane to obtain a composition containing substantially n-butane; and / or (a-4) isomerizing the separated iso-butane to an n-butane / iso-butane mixture and recycling the n-butane / isobutane mixture in step (a-3); and / or (a-5) reaction of isobutene from the composition comprising butane to methyl tert-butyl ether by chemical reaction with methanol to be added, and separation of the resulting methyl tert-butyl ether from hydrocarbons by rectification. The method of any one of the preceding claims, wherein step (c) comprises one or more of the preceding substeps (c-1) cooling; and / or (c-2) compacting; and or (c-3) separation of volatile by-products; and / or (c-4) optionally chemical reaction of isobutene to methyl tert-butyl ether and separation of the methyl tert-butyl ether formed by hydrocarbons by rectification. The process according to any of the preceding claims, wherein step (b) and optionally step (b ') are carried out autothermally with the introduction of an oxygen-containing gas. The procedure according to Claim 12 wherein the oxygen-containing gas is air. An apparatus for producing butadiene from butane comprising the elements operatively connected to each other (a) a dehydrogenating device (2) for non-oxidative catalytic dehydrogenation of a composition containing butane to produce a composition A containing butadiene, butene and butane; (b) an oxydehydrogenator (4) for the oxidative non-catalytic and / or catalytic dehydrogenation of butene and butane contained in composition A, and butene contained in composition D1 to produce a composition B containing butadiene, butene and butane; (c) a separation device (11) for separating the composition B into a butadiene-enriched composition C1 and a butadiene-depleted composition C2; (d) another separation device (15) for separating the composition C2 into a butene-enriched composition D1 and a butane-enriched composition D2; and (e) means (16) for returning the composition D1 to the oxydehydrogenating device (4) or means (16 ') for returning the composition D1 to the further oxydehydrogenating device (4'); and means (17) for returning the composition D2 to the dehydrating device (2). The device after Claim 14 which further comprises: a further oxydehydrogenating device (4 ') for the oxidative dehydrogenation of butene and butane contained in composition B, and optionally in composition D1, to produce a composition B' containing butadiene, butene and butane; another separation device (11) for separating the composition B 'into a butadiene-enriched composition C1' and a butadiene-depleted composition C2 '. The device after Claim 14 or 15 wherein the dehydrogenating device (2) comprises one or more of the upstream components (a-1) to (a-5): (a-1) a device for providing a hydrocarbon composition; and / or (a-2) an apparatus for separating propane and optionally methane, ethane and C5 + hydrocarbons (especially pentanes, hexanes, heptanes, benzene, toluene) from the hydrocarbon composition; and / or (a-3) an apparatus for separating iso-butane from the composition containing butane; and / or (a-4) means for isomerizing the separated iso-butane to a n-butane / iso-butane mixture and recycling the n-butane / isobutane mixture in step (a-3); and / or (a-5) an apparatus for the chemical reaction of isobutene to methyl tert-butyl ether with methanol to be added, and apparatus for separating the resulting methyl tert-butyl ether from hydrocarbons. The device according to one of Claims 14 to 16 wherein the separating device (11) preferably comprises one or more of the upstream components (c-1) to (c-4): (c-1) a device for cooling the composition B or B 'and / or C1 and / or C2; and / or (c-2) a device for compressing the composition B or B 'and / or C1 and / or C2; and / or (c-3) an apparatus for separating volatile by-products; and / or (c-4) an apparatus for the chemical reaction of isobutene to methyl tert-butyl ether with methanol to be added, and apparatus for separating the resulting methyl tert-butyl ether from hydrocarbons; The device according to one of Claims 14 to 17 wherein the Oxydehydriervorrichtung (4) and / or the further Oxydehydriervorrichtung (4 ') is designed for autothermal oxidative dehydrogenation. The device according to one of Claims 14 to 18 wherein the separation device (11) comprises an extraction device or an extractive rectification device. The device according to one of Claims 14 to 19 wherein the further separating device (15) comprises an extractive rectification device. The device according to one of Claims 14 to 20 comprising - a heat exchanger (7) upstream of the separating device (11) for cooling the composition B or B '; and / or - one of the separating device (11) upstream compressor (9) for compressing the possibly previously in Heat exchanger (7) cooled composition B or B '.

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