EP3148958A1

EP3148958A1 - Method for producing product olefins by catalytic dehydration of suitable reactants

Info

Publication number: EP3148958A1
Application number: EP15725339.4A
Authority: EP
Inventors: Florian Winkler; Petra Rehak
Original assignee: Linde GmbH
Current assignee: Linde GmbH
Priority date: 2014-05-28
Filing date: 2015-05-28
Publication date: 2017-04-05
Also published as: CN106414378A; WO2015181302A1; CA2947220A1; JP2017517510A; AU2015265920A1; PH12016502136A1; EP2949635A1; EA201692116A1; KR20170013283A; US20170190636A1

Abstract

The invention relates to a method for producing product olefins by catalytic dehydration of suitable reactants, comprising the steps of feeding of an educt stream, which comprises an alcohol-water mixture, into a a dehydration unit, wherein the alcohol-water mixture contains at least one alcohol and water, and converting the reactants contained in the educt stream in the dehydration unit by catalytic dehydration to a mixed reaction-product stream, wherein the dehydration conditions in the dehydration unit are selected such that the dehydration of the alcohol shows only a small conversion of the at least one alcohol used to the desired at least one product olefin, so that the non-reacted at least one alcohol in the mixed reaction product stream has an alcohol content in the range of 20 wt% - 80 wt%.

Description

description

Process for the preparation of product olefins by catalytic dehydration of suitable reactants

The invention relates to a process for the preparation of product olefins by catalytic dehydration of suitable reactants, in particular by catalytic dehydration of alcohols and alcohol mixtures.

The dehydration of alcohols to product olefins by elimination of water in the presence of a catalyst is a known reaction. Thus, by dehydration of butanol, for example, 1-butene (also referred to in the literature as 1-butylene) as the main product and 2-butene (or 2-butylene) as a by-product can be prepared. The dehydration is a strongly endothermic reaction. US 201 1/0213104 A1 describes a process for the production of ethylene

Butylene copolymers from renewable raw materials. In this case, the ethylene is produced by means of a dehydration reaction of ethanol, which is provided by a fermentation of sugar. Furthermore, butylene is by means of a

Dehydration reaction prepared, wherein the starting material butanol is provided by a fermentation of sugar or by a chemical reaction of the above-mentioned ethanol. Alternatively, butylene can be prepared by a dimerization reaction of the ethylene provided by the dehydration reaction described above. The reaction conditions are

Dehydration reaction of the butanol selected so that a selectivity of 77.5% 1-butylene and 20% 2-butylene (based on the molar amount of the

Butanols) in the final product is achieved. Furthermore, a separation of the dehydration products obtained from the butanol is described by means of a distillation, wherein unreacted butanol can be separated off and fed to the dehydration reactor.

EP 2 374 781 A1 discloses a process in which isobutanol is simultaneously dehydrated and subjected to skeletal isomerization, in which

Substantially the corresponding olefins having the same carbon number are formed become. These are essentially a mixture of n-butenes and isobutene. The process comprises feeding an isobutanol and optionally water and an inert component-containing stream into a reactor and bringing it under suitable conditions with a catalyst in contact. After any removal of water and inert components, the reactor effluent may be separated into a stream containing n-butenes and a stream containing isobutene. The latter can be returned to the reactor. A comparable method is known from WO 201 1/1 13834 A1.

WO 2013/032543 A1 proposes a method and a device for

Dehydration of biogenic 1-alcohols to 1-alkenene with high selectivity. The 1-alkenes can be used advantageously for the production of diesel oil and kerosene with a high flash point. The 1-alkenes can also be converted into thermally stable lubricants. The invention is based on the object, an economical method for

To provide production of product olefins by catalytic dehydration of suitable reactants. In particular, the invention should provide an energetically advantageous process with a high selectivity. This object is achieved by a method having the features of independent claim 1.

The process according to the invention for the preparation of product olefins by catalytic dehydration of suitable reactants comprises the steps of feeding a feedstock stream comprising essentially an alcohol-water mixture, wherein the alcohol-water mixture comprises at least one alcohol and water, into a dehydration unit, and an implementation of the

Reactant contained in the reactant stream in the dehydration unit by catalytic dehydration to a mixed reaction product stream, wherein the

Dehydration conditions in the dehydration unit are selected such that the unreacted at least one alcohol in the mixed reaction product stream has an alcohol content in the range of 20% by weight to 80% by weight, in particular in the range of 20% by weight to 60% by weight, more preferably in the range of 20% by weight % - 40% by weight. The weight% (weight percentage) refers to the Alcohol content in the mixed reaction product stream in relation to the others in the

Mixed reaction product stream of existing compounds.

The inventive method thus allows by the choice of suitable reaction conditions, a low conversion of the alcohols used to the desired at least one product olefin. By dehydration with a low conversion, a high selectivity in the formation of the desired product olefin is achieved. The by-product isomers of the desired product olefin are produced to a very low extent at low conversions.

For the purposes of the invention, the mixed reaction product stream comprises the desired at least one product olefin (olefins are also referred to as alkenes), optionally at least one isomer of the desired product olefin, unreacted alcohol, dialkyl ethers formed during the dehydration, water and further by-products formed during the dehydration, such as, for example Carbon monoxide, carbon dioxide, hydrogen, methane and other alkanes and olefins.

The educt stream according to the invention essentially comprises, as reactants, alcohols or alcohol mixtures, in particular higher-grade alcohols and alcohol mixtures. Furthermore, the reactant stream may comprise dialkyl ethers which are formed during the dehydration and recycled as reactants. Dialkyl ethers include

symmetrical dialkyl ethers (formed from a reaction of two identical alcohols) and unsymmetrical dialkyl ethers (formed from a reaction of two different alcohols). Examples of symmetrical dialkyl ethers are diethyl ether, dipropyl ether, dibutyl ether, dipentyl ether or dihexyl ether. Examples of unsymmetrical dialkyl ethers are butylhexyl ether or butylpentyl ether.

In this case, the reactant stream may comprise synthetically produced alcohols which either contain water or to which water has been added. Alternatively, the

Feedstream can also be provided via a fermentation. By a

Fermentation of biomass, such as sugar, can be various

Alcohols are obtained as alcohol-water mixtures. Preferably, the formed during the fermentation alcohol-water mixture by means of a Enrichment unit in which water is separated, enriched to an alcohol-water mixture with a higher alcohol content.

In one embodiment, the educt stream comprises an alcohol content of 5% by weight to 98% by weight, in particular from 40% by weight to 96% by weight, more preferably of

75% by weight - 95% by weight.

In one embodiment of the invention, alcohols having a carbon content of 3 to 8 carbon atoms (ie alcohols from the group of C ₃ -C ₈ -alcohols), in particular from 4 to 6 carbon atoms (ie alcohols from the group of C ₄ -C ₆ - Alcohols) used. The alcohols used include both linear and branched alcohols. The alcohols used include alcohols having one or more (eg, diols, such as butanediol, pentanediol or hexanediol) functional OH groups. In particular, without the inventive method is limited thereto, n-butanol, iso-butanol, tert-butanol, 1, 4-butanediol, 1, 3-butanediol, 2,3-butanediol n-pentanol, n-hexanol and their Structural isomers (such as, for example, 2-pentanol, 3-pentanol, 2-methyl-2-butanol, 3-methylbutan-1-ol, 3-methyl-2-butan-2-ol, 2,2-dimethyl-propane 1 -ol, 2-hexanol, 3-hexanol, 2-methylpentan-1-ol, 3-methylpentan-1-ol, 3-methylpentan-2-ol, etc.) used singly or in admixture. Particularly preferred is the use of C ₄ -alcohols, in particular n-butanol.

The dehydration unit is designed to provide alkenes from the feed reactants of the educt stream. In this case, the dehydration unit one or more sequentially connected reactors for carrying out the

Dehydration include. The dehydration can be carried out isothermally as well as adiabatically.

In one embodiment of the invention, following the dehydration, the mixed reaction product stream is cooled by means of a cooling unit to form a multi-phase mixed reaction product stream such that the mixed reaction product stream has an aqueous phase and an organic-liquid phase

then an introduction of the mixed reaction product stream into a

Phase separation unit takes place in which a phase separation of the aqueous is made by the at least one organic-liquid phase. Subsequently, the aqueous phase and the at least one organic liquid phase from the multi-phase mixed reaction product stream separated. The separation of the phases can for example be done in the simplest way by means of centrifugal force, for example a separator, or by means of gravity, for example mixer-settler apparatuses. For the purposes of the invention, an "aqueous phase" means the phase which comprises the major portion of the water formed in the dehydrogenation reaction, the aqueous phase likewise comprising unreacted alcohols and dialkyl ethers formed in the reaction, depending on the nature of the educts used. In the context of the invention, an "organic-liquid phase" is to be understood as meaning a liquid phase which, depending on the nature of the educts used and the conditions of the phase separation, does not give off any alcohols formed during the reaction

Dialkyl ethers, product olefins, their isomers and by-products. Also, the organic-liquid phase may contain a small proportion of the water formed in the dehydrogenation reaction.

After phase separation, the organic-liquid phase is passed into at least one separation unit, wherein unreacted alcohols and by the

Dehydration resulting dialkyl ethers are separated so that they form a traceable separation stream, which is supplied to the reactant stream.

Furthermore, in addition to the traceable separation stream and the at least one desired product olefin and optionally formed isomers of

Product olefins) are separated from the further by-products. The aforementioned product olefins form an olefin stream, which is derived from the separation unit. The by-products are separated and discharged from the organic phase in the separation unit. Arisen isomers of

Product olefins / product olefins can also be recycled to the reactant stream or removed from the plant.

By recycling the traceable separation stream, which indeed contains alcohols and diethyl ether, it is possible that unreacted alcohol and dialkyl ethers formed by the dehydration, which are still present in the organic-liquid phase after the phase separation, are not removed from the reaction cycle, but instead rather, a further reaction in the Dehydration unit are available. Thus, the overall conversion of the alcohol to the desired product olefin can be increased. The dialkyl ethers contained in the organic liquid phase are intermediates which are formed on dehydration and which can be converted by additional dehydration to give the desired product olefin. Thus, these dialkyl ethers are also reactants which are capable of being converted to the desired one by means of a dehydration step

Product olefins to be implemented. By introducing the dialkyl ethers into the educt stream, the overall conversion of the desired product olefins is likewise increased. The resulting in a dehydration reaction intermediates (ie the dialkyl ethers) are recycled.

In this case, the reactant stream when starting the system only have an alcohol-water mixture, with other reactants, such as

Dialkyl ethers, only after a first run, as described above, in the

Feed the educt current.

Following the phase separation of the aqueous phase from the organic-liquid phase, in one embodiment the aqueous phase is fed to the educt stream via a concentration in which the at least one alcohol contained in the aqueous phase and dialkyl ethers formed by the dehydration is enriched.

In the known in the prior art method is basically the

Reaction water, which is present after the dehydration of the alcohol-water mixture in the mixed product stream, separated. Thus, a part of the unreacted alcohol dissolved in the reaction water is lost. By recycling the unreacted alcohol contained in the aqueous phase and the dialkyl ether contained in the aqueous phase), these reactants are available for further dehydration and can thus be converted to the desired alkene. As a result of this recycling into the reaction cycle, the overall conversion of the alcohol used is thus increased with respect to the resulting and desired product olefin. Furthermore, thus no dewatering occurs during dehydration, which must be laboriously cleaned or disposed of. Also, the separation of the aqueous phase from the organic-liquid phase (and thus the Separation of the dissolved therein reactants) in a simple manner, such as by means of a decanter, so without a large energy or equipment expense. The enrichment or concentration of the aqueous phase can be carried out, for example, by distillation, pervaporation or extraction in an enrichment unit. Such an enrichment unit may, for example, also be an enrichment unit in which alcohol from a fermentation is enriched or concentrated. Such enrichment units are in processes that the starting material (ie the alcohol to be reacted) from a

Provide fermentation step, normally available. Thus, it is possible to combine the aqueous phase with the alcohol-water mixture from a fermentation and feed it to a single enrichment unit. The enriched there alcohol-water mixture can then be supplied to the reactant stream and then forms the reactant stream and is fed into the dehydration unit. Thus, the expenditure on equipment and energy is moderate.

This is especially true if a fermentation process is used in which a fermenter broth is present, since then the aqueous phase of the fermenter broth can be added. The alcohol concentration in the aqueous phase is on the order of the alcohol concentration in the fermenter broth, and the aqueous phase mass flow is relatively low compared to the fermentation stream. Of the

Flow rate of the aqueous phase depends on the mode of operation of the plant and often reaches only about 1/12 in comparison to the fermentation stream. Also at

continuous fermentation process, for example, apparatus devices are provided which are intended for concentration. Thus, for example, the aqueous phase can be added to the stripper or directly into the fermenter broth. The means for enrichment in the various fermentation processes are known in the art. Alternatively, the alcohol to be reacted or the alcohol mixture to be reacted can also be produced synthetically, for example from synthesis gas by means of suitable catalysts. This usually produces alcohol mixtures, which are fed either directly or after a work-up (eg a distillation) the reactant stream. Again, the aqueous phase at a suitable location, such as in the distillation, are fed. The phase separation of the aqueous from the organic-liquid phase thus enables a recycling of unreacted alcohols and / or resulting dialkyl ethers in the dehydrogenation reaction in a simple manner. The recycling of the alcohol and the dialkyl ethers allows a better use of the alcohol used as starting material for the preparation of a product olefin. In this case, the alcohol used and the dialkyl ethers formed by the above-described recycling of the aqueous phase and / or the recycling of the

Separation stream can be recycled into the dehydration unit. By the

Recycling of the intermediate dialkyl ethers and the unreacted alcohol can be particularly low, easier to achieve

Reactions can be driven in the dehydration unit, without resulting in economic disadvantages. Thus, by recycling the intermediates (dialkyl ethers) and the unreacted alcohol and having a low reaction in the

Dehydration unit increases both the selectivity and the yield of the desired product olefin. In embodiments of the invention, at least partial streams of the aqueous and / or organic-liquid phase can be recycled to the educt stream.

Preferably, the aqueous phase after enrichment and / or a

Separation stream, which was recovered from the organic-liquid phase and the alcohols and / or the dialkyl ethers from the mixed reaction product stream at least partially contains, recycled to the dehydration unit. Thus, the alcohols and / or the dialkyl ethers from the mixed reaction product stream can once again be used

Dehydration be supplied. Which of the possible recycles are realized depends on the composition of the mixed reaction product stream and follows economic considerations.

In addition to the organic-liquid phase and the aqueous phase may be in the

Dehydration in addition also an organic-gaseous phase arise. Whether an organic-gaseous phase is formed depends on the alcohols used as starting materials, the extent of the reaction of the alcohols and the reaction conditions of the dehydration and the conditions in the phase separation unit (in particular Pressure and temperature). The proportion of the compounds present in the aqueous or the at least one organic phase (such as unreacted alcohol or dialkyl ethers) is thus dependent on the reaction conditions and the nature of the alcohols used. For an explanation of the phase separation conditions, reference is made to the lower passages. The nature of the separation and the further use of the separated phases are thereby determined. This is one of the standard tasks of a skilled person in the field of olefin production and olefin separation and can be easily carried out by him. If, for example, higher alcohols (for example butanols, pentanols or hexanols) or mixtures thereof are used as starting material, it is possible for the

Mixed reaction product stream in addition to the aqueous phase has an organic-liquid phase. The organic-liquid phase comprises unreacted alcohol, dialkyl ethers formed by dehydration, at least one product olefin and optionally the corresponding isomers thereof. The aqueous phase essentially comprises unreacted alcohol.

In this embodiment, a gaseous phase is also present, which, however, comprises only by-products. The organic-gaseous phase, apart from impurities, may consist entirely of by-products, such as carbon monoxide, hydrogen, carbon dioxide, methane and alkanes. However, in addition to the by-products, the organic-gaseous phase may also contain the product olefin / product olefins as well as isomers of the product olefin / product olefins. It is also possible that still unreacted alcohols and

Dialkyl ethers are contained in the organic-gaseous phase.

By-products can be separated and derived in the phase separation and / or in the separation unit and / or in an isomer separation unit. Alternatively or additionally, by-products such as C0 ₂ can be separated by means of a C0 ₂ scrubbing prior to introduction into the separation unit.

After the phase separation of the aqueous, the organic-liquid and the organic gas phase, the organic-gaseous phase is then in a

Separation unit directed to the separation of individual components. This can be done for example by means of a compressor. In the separation unit, the product olefin (s) (and any resulting isomers its / their) separated, wherein an olefin stream is formed, which is derived from the separation unit. The aqueous phase and the organic liquid phase are processed as described above. If, for example, an alcohol mixture of lower alcohols (for example n- or isopropanol) and higher alcohols (for example butanols, such as n-, iso- and / or tert-butanol and / or, for example, pentanols, such as 1-pentanol and isomers thereof) used as starting material, the mixed reaction product stream - in addition to the aqueous phase - an organic liquid phase and an organic-gaseous phase. The aqueous phase has unreacted alcohols (eg butanols or propanols) and a proportion of dialkyl ethers. The organic-liquid phase comprises a proportion of unreacted alcohols, a proportion of dialkyl ethers and at least one product olefin, such as 1-butene, and optionally corresponding isomers of at least one

Produktolefins. The organic-gaseous phase comprises at least one product olefin (e.g., propene) as well as starting materials (alcohols) and dialkyl ethers.

In particular, in the use of higher alcohols, by cooling the mixed reaction product stream and the associated formation of a two-phase liquid mixed reaction product stream advantageously, the biphasic

Mixed reaction product stream in a simple manner by means of

Phase separation unit in that aqueous phase and those organic-liquid phase are separated. The separation of the aqueous phase from the organic-liquid phase can be carried out, for example, by means of a decanter. The inventive method allows by choosing appropriate

Reaction conditions, a low conversion of the alcohols used, which leads to an increased selectivity of the desired product olefins. Almost no or hardly any isomers of the product olefins are formed. Furthermore, the

Phase separation a recycling of unreacted alcohols or dialkyl ethers formed in the dehydrogenation reaction. By recycling or "recycling" of the incurred as intermediates dialkyl ethers and the unreacted alcohol especially low, easier to achieve reactions in the

Dehydration be driven without this incurs economic disadvantages. The resulting isomers of product olefins, the quantitative extent, as already said, usually very low, are either separated or one

Isomerization unit supplied. Furthermore, it is also conceivable to leave the isomers of the product olefins in the product olefins. Preferably, the isomers of the product olefin in the isomerization unit are at least partially into the isomerization unit

Converted product olefin. Also, the unwanted isomers of the

Product olefins are at least partially recycled to the dehydration unit where they are at least partially reacted. When recycling, however, care must be taken to ensure that the isomers of the product olefins do not accumulate in the circulation.

Furthermore, by the choice of dehydration conditions which are suitable for providing a low conversion, the further isomerization step customary in the prior art can be dispensed with. At a low conversion, undesired by-products such as isomers of the desired product olefin (s) fall

Product olefins and other alkanes or alkenes only to a very reduced extent. At a low conversion arise -neben the desired product olefin and a not inconsiderable number of dialkyl ether compounds as

Intermediates. The latter can be returned as described. They are thus available for another dehydration step as reactants. Furthermore, due to the low conversion rate, the desired product olefin is produced in a high product purity. The olefin stream can in many cases be supplied to a consumer without further workup. Alternatively, the olefin stream may also be fed to an isomer separation unit in which the olefin stream undergoes further purification and separation. This can be done for example by means of a rectification. In the

Isomer separation unit remaining by-products can be separated from the olefin stream. Furthermore, in the isomer separation unit, a separation of the desired product olefin from the possibly resulting isomers of the product olefin. For example, 1-butene may be of

incurred 2-butene be separated from the olefin stream. That in the

Isomeric separation unit separated desired product olefin, such as

for example 1-butene, can be supplied to a consumer. In some processes, the undesired isomer is then in a

Isomerization unit implemented. In the isomerization unit, a partial reaction of the separated isomer then takes place to the desired product olefin. For example, 2-butene is partially isomerized to 1-butene. That in the

Isomerization unit resulting isomer mixture can then - after cooling - the isomer separation unit for the separation of the desired product olefin from the isomer mixture are supplied. Thereby, the yield and selectivity of the desired product olefin can be increased. For an isomerization, an additional energy is required for the necessary isolation of the desired product olefin from the isomer mixture of the isomerization unit, since the isomer mixture of the isomer separation unit must be supplied to isolate the desired product olefin. In addition requires the

Energy isomerization, as it is about 400Ό. Since, in principle, the separations in the isomer separation unit take place in a temperature range from 30 ° to 100 °, an additional unit and energy would have to be provided which heats the isomer mixture to about 400 ^° C. starting from this temperature range. When carrying out the process according to the invention, the proportion to be isomerized is extremely low or hardly present. If the workup of the isomers is omitted, the apparatus and energy expenditure described above can be completely eliminated. Even if the isomers were worked up, a significantly lower energy expenditure would be necessary in the process according to the invention, since the isomeric fraction is markedly lower due to the high selectivities and yields. The energy required to bring the "recycle products", for example, unreacted butanol and the resulting dibutyl ether, to the dehydration temperature, falls below the additional energy required for an otherwise necessary workup of the isomers.

Another advantage of the application of the method according to the invention is that the expenditure on equipment with regard to the dehydration unit can be additionally reduced. In general, the dehydration unit consists of a

Series connection of at least one fixed bed reactor, wherein in principle two to three reactors are necessary in order to full conversion to reach. However, since full conversion is not necessary in the process according to the invention and the reaction conditions in the dehydration unit are chosen such that a low conversion takes place, it is advantageously possible to dispense with a reactor in the dehydration unit.

As catalysts for the dehydration step, preference is given to using inorganic ceramic catalysts, in particular ZrO ₂ , zeolites, Al ₂ O ₃ or aluminosilicates. However, other suitable catalysts can also be used.

In one embodiment of the invention, the isomers separated in the isomer separation unit are recycled to the educt stream. In this case, the thus separated isomers are preferably then fed to the reactant stream when the dehydration is carried out by means of an Al ₂ O ₃ or aluminosilicate catalyst. When using such a catalyst, an isomerization of the isomer of the desired product olefin to the product olefin is also carried out in the dehydration step. In particular, 2-butene separated off in the isomer separation unit is preferably returned to the dehydration, where it is isomerized to 1-butene by means of a catalyst, in particular an Al ₂ O ₃ catalyst.

In a further embodiment of the invention, the isomers of the

desired product olefins can also be recycled to dehydration to act as a heat carrier or to affect the balance between the desired product olefin and the corresponding isomer of the desired product olefin. In particular, there is an effect on the equilibrium between 1-butene and 2-butene in favor of 1-butene.

The dehydration is designed so that low conversions of the alcohol take place. This is achieved by choosing the parameters discussed below.

Advantageously, the dehydration at a temperature between 200Ό and 500Ό, in particular between 280Ό and 400 ^< C, FITS preferably between 300 and 360 ^< C performed. In one embodiment, the dehydration at a liquid hourly space velocity (LHSV) of 1 h is ^"1 to 15 h ^{" 1} , in particular 2 h ^"1 to 10 h ^{" 1} , particularly preferably 3 h ^"1 to 9 h ^"1 performed. For the purposes of the invention, LHSV (liquid hourly space velocity) is to be understood as meaning the quotient of the feed for dehydration (measured in m ³ / h) and the catalyst volume (measured in m ³ ).

In one embodiment, the dehydration is carried out at a pressure in a range from 3 bar to 30 bar, in particular from 5 bar to 17 bar, particularly preferably from 6 bar to 10 bar.

In a further embodiment of the invention, the phase separation takes place in a range from 3 bar to 30 bar, in particular from 5 bar to 17 bar, more preferably from 6 bar to 10 bar.

In one embodiment of the invention, the separation takes place in a range from 3 bar to 30 bar, in particular from 5 bar to 17 bar, more preferably from 6 bar to 10 bar.

In one embodiment, the pressure is at the dehydration, the

Phase separation and / or separation in a range of 3 bar to 30 bar, in particular from 5 bar to 17 bar, more preferably from 6 bar to 10 bar. In one embodiment, the pressure is at the dehydration, the

Phase separation and the separation in a range of 5 bar to 17 bar, in particular from 6 bar to 10 bar, being used as starting materials butanols or higher alcohols. The above dehydration, phase separation and separation pressures can be independently selected from the respective ranges, so that dehydration, phase separation and separation occur at different pressures. Alternatively, the pressures selected from the upper ranges can also be the same values for the

Dehydration, and / or phase separation and / or separation. In one embodiment of the invention, the phase separation occurs at a

Temperature between -10Ό and 90Ό, in particular zwi 20'C and ΘΟΌ, more preferably between 30Ό and 50Ό.

Preferably, the process according to the invention essentially produces a 1-alkene, in particular 1-butene. Furthermore, with the

According to the invention, other corresponding alkenes are also prepared.

In the following, the invention will be described with reference to figures of particularly advantageous embodiments. Show it:

Fig. 1 shows an embodiment of the inventive method for

Preparation of 1-butene; Fig. 2 shows the purity of the product olefin 1 -butene formed in relation to a certain conversion rate;

FIG. 3 shows the inventive method of FIG. 1 taking into account the most energy-intensive steps;

, 4 shows an embodiment of the method according to the invention

Use of an alcohol mixture comprising lower and higher alcohols (3-phase separation). Fig. 1 shows a particularly advantageous embodiment of the invention

Process. A butanol-water mixture from a fermentation process (not shown here for reasons of clarity) is passed into an enrichment unit 7. There, an enrichment of the alcohol content of the butanol-water mixture by means of a distillation, wherein excess water from the

Separation unit 7 is derived. The so enriched butanol-water mixture forms a reactant stream E, which from the enrichment unit 7 in a

Compression unit 5 is passed.

The reactant stream E is compressed in the compression unit 5, such as a pump, to a pressure of 5 bar to 17 bar and then into a Heating unit 6 passed where the reactant stream is heated to a temperature of 300Ό to 360 ^< C heated.

This is followed by feeding the compressed and superheated reactant stream into the dehydration unit 1. The dehydration can be one or more

Reactors (not shown here for reasons of clarity) have. In the dehydration unit 1, the dehydration of the butanol. The reaction conditions in the dehydration unit are chosen such that only a low conversion rate of the butanol used to the desired

Product olefin 1 is present. At the given reaction conditions, the corresponding dibutyl ether is preferably generated in addition to the desired 1-butene. The isomer (2-butene) to the product olefin 1 butene is only to a very small extent. Other by-products, such as other C ₄ hydrocarbons, can only be observed in traces.

After dehydration, the reaction products are passed to a cooling unit 2. In this case, the pressure of the dehydration has been selected such that after cooling to about 40 ° C., essentially a two-phase

Mixed reaction product stream M forms. It forms an organic-liquid phase FOP, which essentially comprises unreacted butanol, dibutyl ether, the desired product olefin 1 -butene and its corresponding isomer 2-butene (the latter in small amounts). The second phase formed is an aqueous phase which is liquid and which essentially comprises - due to limited solubility - butanol in small amounts and a minor amount of the dibutyl ether formed.

The formed biphasic mixed reaction product stream M is passed from the cooling unit 2 into a phase separation unit 3. In the phase separation unit 3 takes place at a temperature of 40Ό and a pressure of 3 bar to 16 bar, a separation of the two liquid phases. This can be done for example by means of a decanter. The aqueous phase is passed into the enrichment unit 7. Thus, a portion of the unreacted butanol (and small amounts of dibutyl ether formed) in the enrichment unit 7 with the butanol-water mixture from the fermentation (fermentation stream F) combined, there enriched by water separation and then fed to the reactant stream E. Alternatively, the aqueous phase after Passage of the enrichment unit 7 are combined with a reactant stream E, in which the alcohol (or the alcohols) are provided from synthesis gas (not shown here). There is thus no polluted waste water flow in the

Dehydration step, but the accumulating water is the

Enrichment step supplied. As a result, the water obtained during the dehydration, which contains reactants, can be recycled to the reaction cycle. Only separated from the enrichment unit 7 and substantially pure water accumulates. The separated in the phase separation unit 3 organic-liquid phase FOP can be promoted via a pump in a downstream separation unit 4. In an alternative, not shown here, an organic-gaseous phase may additionally be present. This can be transferred via a compressor in the separation unit. The further steps essentially apply analogously.

Advantageously, the pressure of the dehydration step can be chosen such that it is already sufficiently high for carrying out the separation steps in the separation unit 4, thus eliminating the compression unit. In the separation unit 4, the resulting alkenes (1-butene and 2-butene) from the unreacted and still contained in the organic-liquid phase FOP butanol (in higher alcohols, such as butanol, the majority of not

reacted alcohol usually contained in the organic-liquid phase) and the intermediate dibutyl ether and the other

Separated by-products. The unreacted butanol and the resulting dibutyl ether form a separation stream S, which is passed into the compression unit 5, where it is mixed with the enriched from the enrichment unit 7 enriched reactant mixture, compressed and then passed into the feed stream E. Furthermore, the by-products contained in the organic liquid phase FOP, such as, for example, carbon monoxide, hydrogen, carbon dioxide, methane or alkanes, are additionally separated off and discharged in the separation unit 4.

The product olefins P (1-butene and 2-butene) separated from the organic-liquid phase FOP in the separation unit 4 can be converted into an isomer separation unit 8 be directed. There is a further separation of any remaining by-products (as already described). In particular, in the

Isomer Separation Unit 8 is a separation of the desired product olefin 1-butene from the corresponding isomer 2-butene. The isolated 1-butene can be supplied to a consumer.

The amount of 2-butene produced in accordance with the process according to the invention is so low in its amount that energy-intensive isomerization of the 2-butene to the desired 1-butene is usually unnecessary. Alternatively, it is possible (as shown in Figure 4), that the separated 2-butene is passed into an isomerization unit 1 1, where it is isomerized to a reaction mixture consisting of 1-butene and 2-butene, which then to a further separation back in the

Isomer Separation Unit 8 (after cooling to the desired

Isomerenabtrennungstemperatur from 30Ό to 100Ό) g is led. There is again a separation of the 1-butene and 2-butene, wherein the separated 2-butene is in turn passed into the isomerization unit 1 1.

Alternatively, if the dehydration is carried out by means of a catalyst selected from the group of Al ₂ 0 ₃ or aluminosilicates, the separated isomers I are fed to the reactant stream E. These catalysts are suitable for converting the separated isomers into the product olefins during dehydration (this alternative is shown by a dashed line in the figure). In a further alternative, if the alcohols were prepared synthetically, the isomers can be fed to a reformer (not shown here).

The inventive method has no separate disposal

Wastewater flow on. Instead, the unreacted butanol portion and the intermediate products formed (dibutyl ether) are fed back via the phase separation unit 3 and the separation unit 4 to the educt stream E for further reaction in the dehydration unit 1. By this reuse and the low conversion in the dehydration unit 1, a high selectivity and yield of 1-butene is achieved. By the targeted choice of suitable

Reaction conditions, it is by means of the method thus it is possible to increase both the selectivity and the yield of 1-butene without the need for an isomerization step. With the method according to the invention it is possible, for example, to increase the 1-butene yield by about 20%, the dehydration being carried out up to a conversion of about 50%. The methods known in the prior art follow in the

Dehydration step basically a ca. 90% conversion. If the isolated butene mixtures (1-butene and 2-butene) are considered, the process according to the invention makes possible a 1-butene content of more than 95%. In the prior art, for example (US Pat. No. 201 1/0213104 A1), a 1-butene content of 77.5% and a 2-butene content of 20% are achieved.

Alternatively, other alcohols or alcohol mixtures can be used.

Fig. 2 shows the purity of the resulting butene mixture (1-butene and 2-butene) after separation from a separation unit 4 with respect to that in the

Dehydration unit present implementation. As can be seen from FIG. 3, with a conversion of less than 50%, a purity of more than 95% of 1-butene can be achieved. Even with a conversion of more than 70%, a purity of about 90% can still be achieved with respect to the obtained desired 1-butene.

FIG. 3 shows the method according to the invention when using a

Isomerization unit 1 1, wherein the necessary energy expenditure was taken into account. For elements which are provided with the same reference numeral, reference is made to the explanations of Figure 1. Due to an isomerization falls in the

Isomerization unit 1 1 an increased energy expenditure, since the

Isomerization unit 1 1 must be operated at about 400 ° C in order to achieve a suitable isomerization. The isomerization mixture must then be cooled to a range of 30Ό to 100Ό before it is returned to the isomer separation unit 8. Also the additional separation step of the in

Isomerisierungsgemischs provided isomer separation unit 8 requires further energy to a separation, for example by means of distillation, the

desired product olefin 1 -butene from the corresponding isomer 2-butene. By using the method according to the invention, the proportion to be isomerized becomes considerably lower. This allows a high energy saving. The extra energy required to do this after dehydration over the

Separate phase separation or separation separated unreacted butanol and the resulting dibutyl ether, the energy required, which would be necessary for a complete isomerization.

Furthermore, the apparatus required can also be reduced by the method according to the invention. In principle, dehydration takes place in a series connection of the fixed bed reactors, in particular of at least two to three reactors, in order to achieve full conversion. Since according to the invention no full conversion is necessary, but a low conversion rate is desired, can in the

Dehydration unit are usually dispensed with a reactor. FIG. 4 shows the method according to the invention when using a

Alcohol mixture of lower and higher alcohols (3-phase separation). In essence, the method is analogous to that described in Figure 1

Method. In the present case, only the differences are discussed. For elements which are provided with the same reference numeral, reference is made to the explanations of Figure 1 and Figure 3.

By the use of such an alcohol mixture are after the

Dehydration and cooling in the phase separation unit 3, an aqueous phase W, an organic liquid phase FOP and an organic-gaseous phase GOP before. In the phase separation unit 3, the three phases are separated from each other.

The aqueous phase W is fed to the enrichment unit 7 for concentration and then transferred into the educt stream E. The organic-liquid phase FOP is conducted into a first separation unit 4 by means of a compression unit 5, in the present case a pump, and the organic-gaseous phase GOP by means of a further compression unit 5, in the present case a compressor.

In the first separation unit 4, the product olefins P of the

By-products are separated and derived. If necessary, the product olefins P can one further separation, which separates the different product olefins from each other, are supplied.

The remaining organic-liquid phase FOP is passed into a second separation unit 4 ', in which the product olefins P' formed and still contained in the organic-liquid phase FOP of the unreacted higher alcohols and optionally formed dialkyl ethers (and possibly still further existing

By-products) are separated. The unreacted alcohols and the resulting dialkyl ethers form a separation stream S, which is passed into the compression unit 5 where it is mixed with the enriched reactant mixture originating from the enrichment unit 7, compressed and subsequently passed into the educt stream E.

The product olefins P 'separated off from the organic-liquid phase FOP in the separation unit 4' are passed into an isomer separation unit 8. There is a further separation of any remaining by-products (as already described). In particular, in the isomer separation unit 8, a separation of the desired product olefin P from the corresponding isomers takes place. For reasons of clarity, the specification of the exhaust gas flow A and the discharge systems 10 has been dispensed with. Reference is made to FIGS. 1 and 3.

By choosing a suitable pressure of dehydration at least one compressor can be saved after the phase separation.

LIST OF REFERENCE NUMBERS

1 dehydration unit

2 cooling unit

3 phase separation unit

4 separation unit

5 compression unit

6 heating unit

7 enrichment unit

8 isomer separation unit

9 Introduction unit

10 discharge system

11 isomerization unit

A exhaust gas flow

E educt current

I isomer of the product olefin

F fermentation stream

M mixed reaction product stream

0 olefin stream

FOP organic-liquid phase

GOP organic-gaseous phase

P product olefin

S separation stream

W aqueous phase

Claims

claims

1 . Process for the preparation of product olefins by catalytic

Dehydration, comprising the steps:

Feeding a feedstock stream (E) comprising an alcohol-water mixture into a dehydration unit (1), wherein the alcohol-water mixture comprises at least one alcohol and water,

Reaction of the reactants contained in the reactant stream (E) in the

Dehydration unit (1) by catalytic dehydration to a mixed reaction product stream (M),

characterized in that the dehydration conditions in the dehydration unit (1) are chosen such that the unreacted at least one alcohol in the mixed reaction product stream (M) has a

Alcohol content in the range of 20% by weight - 80% by weight.

2. The method according to claim 1, characterized in that the

Mixed reaction product stream (M) is cooled, leaving a

multi-phase mixed reaction product stream (M), comprising an aqueous phase (W) and an organic-liquid phase, wherein a phase separation (3) of the aqueous phase (W) of the organic-liquid phase is carried out.

3. The method according to claim 2, characterized in that at least

Partial streams of the aqueous and / or organic-liquid phase are recycled to the educt stream.

4. The method according to claim 2 or 3, characterized in that further produces an organic-gaseous phase.

5. The method according to any one of claims 2 to 4, characterized in that following the phase separation (3) of the aqueous phase of the organic liquid the aqueous phase (W) is fed to the educt stream (E) via a concentration (7) and / or

the organic-liquid phase is passed into at least one separation unit (4), unreacted alcohol and dialkyl ethers formed by the dehydration being separated in such a way that they form a separation stream (S) which is fed to the educt stream (E).

Method according to one of claims 1 to 5, characterized in that in the separation unit (4) the product olefins (P) and optionally their isomers (I) of the by-products and the compounds containing the

Separation stream (S) form, are separated, wherein the product olefins (P) and optionally their isomers (I) then form an olefin stream (O), which is derived from the separation unit (4).

Process according to Claim 4, characterized in that the olefin stream (O) is introduced into an isomer separation unit (8) for the separation of the isomers (I) of the product olefins from the product olefins (P), and

separated isomers (I)

- An isomerization unit (1 1), or

- the dehydration unit (1), or

- a reformer

be supplied.

Method according to one of claims 1 to 7, characterized in that the dehydration is carried out at a temperature between 200'C and 500Ό.

9. The method according to any one of claims 1 to 8, characterized in that the dehydration at a space velocity (LHSV) of 1 h ^"1 to 15 h ^{" 1 is} performed.

10. The method according to any one of the preceding claims, characterized

in that the at least one alcohol is selected from the group of C ₃ -C ₈ -alcohols.

1 1. Method according to one of the preceding claims, characterized

in that the educt stream (E) has an alcohol content of 5% by weight to 98% by weight.

12. The method according to any one of the preceding claims, characterized in that the pressure in the dehydration in a range of 3 bar to 30 bar.