EP4025549A1

EP4025549A1 - Method for processing a gaseous composition

Info

Publication number: EP4025549A1
Application number: EP20726729.5A
Authority: EP
Inventors: Michael Kleiber; Nils Tenhumberg; Stefan Gehrmann
Original assignee: ThyssenKrupp AG; ThyssenKrupp Industrial Solutions AG
Current assignee: ThyssenKrupp AG; ThyssenKrupp Industrial Solutions AG
Priority date: 2019-09-05
Filing date: 2020-05-08
Publication date: 2022-07-13
Also published as: US20220298088A1; WO2021043452A1; CN114341082A; WO2021043560A1; US20220306948A1; CN114364651A; DE102019213493A1; EP4025550A1

Abstract

The present invention relates to a method for processing a gaseous composition which has been obtained by catalytic reaction of synthesis gas, wherein this composition contains at least alkenes, optionally alcohols and optionally alkanes, and optionally nitrogen as inert gas, and unreacted components of the synthesis gas, comprising hydrogen, carbon monoxide and/or carbon dioxide, wherein, after catalytic reaction of the synthesis gas, at least one step is provided in which the product mixture obtained in this reaction is separated into a gas phase (12) and a liquid phase, in which method, according to the invention, the processing of the gaseous composition comprises at least the subsequent steps of: - separating the product mixture into a gas phase and a liquid phase by at least partial absorption (11) of the alkenes, optionally of the alcohols and optionally of the alkanes, in a high-boiling hydrocarbon or hydrocarbon mixture as the absorption medium; - separating the gases not absorbed in the absorption medium as the gas phase (12); - separating an aqueous phase (28) from the organic phase (14) of the absorption medium, preferably by decanting (13); - and desorption (15) of the alkenes, optionally the alcohols and optionally the alkanes, from the absorption medium.

Description

Process for the preparation of a gaseous mixture of substances

The present invention relates to a method for processing a gaseous mixture of substances obtained by catalytic conversion of synthesis gas, this mixture of substances containing at least alkenes, optionally alcohols and optionally alkanes, and optionally nitrogen as the inert gas and unconverted components of the synthesis gas, including hydrogen, Carbon monoxide and / or carbon dioxide, with at least one step being provided after the catalytic conversion of the synthesis gas in which the product mixture obtained in this reaction is separated into a gas phase and a liquid phase.

Production of synthesis gas from steel mill gases

WO 2015/086154 A1 describes a method for operating a system network for steel production, such a system network including a blast furnace for pig iron production and a converter steelworks for crude steel production. In the blast furnace process, the products of the reduction reactions are CO, C0 ₂ , hydrogen and water vapor, the blast furnace top gas withdrawn from the blast furnace process also having a high content of nitrogen in addition to the aforementioned components. A furnace top gas contains, for example, 35 to 60% by volume of nitrogen, 20 to 30% by volume of carbon monoxide, 20 to 30% by volume of carbon dioxide and 2 to 15% by volume of hydrogen.

Pig iron is converted into crude steel in a converter steelworks downstream of the blast furnace process. By blowing oxygen onto liquid pig iron, disruptive impurities such as carbon, silicon, sulfur and phosphorus are removed. A converter gas which has a high content of carbon monoxide and also contains nitrogen, hydrogen and carbon dioxide is withdrawn from the steel converter. A typical converter gas composition has 50 to 70% by volume of carbon monoxide, 10 to 20% by volume of nitrogen, about 15% by volume of carbon dioxide and about 2% by volume of hydrogen.

In such a network of plants, a coking plant can still be operated, in which coal is converted into coke by a coking process. When coal is coked into coke, a coke oven gas is produced which has a high hydrogen content and considerable amounts of methane. Typically, coke oven gas contains 55 to 70 volume percent hydrogen, 20 to 30 volume percent methane, 5 to 10 volume percent nitrogen and 5 to 10 volume percent carbon monoxide. In WO 2015/086154 A1, the possibility of using blast furnace top gas, converter gas and coke oven gas, which are also referred to as smelting gas in their entirety, for the production of chemical compounds is described, with the raw gases being processed individually or in combination as mixed gas and then as synthesis gas Chemical plant can be fed. Possible chemical compounds that can be produced from such a synthesis gas obtained from steel mill gases are specifically methanol or, in general and unspecifically, “other hydrocarbon compounds”. Furthermore, a biochemical use of the synthesis gas for the production of ethanol or butanol via fermentation is mentioned. However, the production of higher alcohols from the synthesis gas is not dealt with in detail in this publication.

During the preparation of these raw gases, gas cleaning is usually carried out to remove disruptive ingredients, in particular tar, sulfur, sulfur compounds, aromatic hydrocarbons and high-boiling aliphatic hydrocarbons. In addition, gas conditioning usually takes place in which the proportion of the components carbon monoxide, carbon dioxide and hydrogen within the pipe gas is changed. The project of using steel mill gases for the production of chemical products described above is also known as the Carbon2Chem® process.

State of the art relating to the production of alcohols and alkenes by catalytic conversion of synthesis gas

EP 0 021 241 B1 discloses a process for the production of mixtures of acetic acid, acetaldehyde, ethanol and alkenes with two to four carbon atoms by converting synthesis gas containing carbon monoxide and hydrogen in the gas phase over supported catalysts, the catalysts being rhodium and 0.1 contain up to 5.0% by weight of sodium or potassium. The oxygen-containing compounds and the alkenes are formed in a molar ratio of 1: 1 to 2.5: 1. The selectivity of the catalysts used for the alcohols is comparatively poor. During the reaction, at a pressure of 20 bar, a temperature of 275 ° C and a ratio of carbon monoxide to hydrogen in the synthesis gas of 1: 1, more than 20% acetic acid, approx. 12 - 20% acetaldehyde, approx. 5% to 10% Ethene, a comparatively high proportion of propene of sometimes more than 20%, different proportions of methane and only a few percent ethanol, around 2.5 to 7%. In this known process, the aim is to produce mixtures of oxygen-containing C2 compounds and a high proportion of low molecular weight alkenes and to reduce the methane proportion. Processes for separating the classes of compounds from the mixture obtained are not described. US Pat. No. 6,982,355 B2 describes an integrated Fischer-Tropsch synthesis for the production of linear and branched alcohols and alkenes, in which a light fraction and a heavy fraction are first separated from one another and the light fraction is contacted with a dehydration catalyst to obtain a light fraction , which contains alkenes and alkanes, this is then further divided into fractions containing C5 - C9 and C10 - C13 alkenes and alkanes, which are then partially converted with synthesis gas to the aldehydes with the corresponding chain lengths. From the aldehydes contained in the alkane fraction, the corresponding alcohols, which are still contained in the alkane fraction, are then produced by reaction with hydrogen. In a first distillation these alcohols are separated from the alkanes and in a further distillation the individual alcohols are obtained from the C5 - C9 fraction and the C10 - C13 fraction. The alkanes of the appropriate fractions can be dehydrogenated to the alkenes. The catalysts used in the Fischer-Tropsch synthesis are cobalt, iron, ruthenium or other transition metals from group VIIIB, optionally on an oxidic carrier such as silicon dioxide, aluminum oxide or titanium oxide.

CN108067235A describes catalysts for the production of alkenes from synthesis gas which contain cobalt and cobalt carbide as the active component, lithium as an additive and one or more other metals selected from manganese, zinc, chromium and gallium. In addition to the alkenes, higher alcohols are also formed during the conversion. When these catalysts are used, the selectivity for a mixture of alkene should be up to 40% and that for a mixture of alcohols should be 30%. Straight-chain alkenes with 2 to 30 carbon atoms and primary alcohols with corresponding chain lengths are obtained. The product mixture mainly contains alkanes and alkenes and, depending on the catalyst, about 20% to 25% alcohols, with methanol, alcohols with 2 to 5 carbon atoms and higher alcohols with 6 or more carbon atoms being formed, the latter group of alcohols being formed make up the majority and are usually more than 50% formed. The publication does not contain any details on the separation of the various products contained in the mixture.

CN108014816A describes catalysts for the conversion of carbon monoxide with hydrogen to produce mixed primary alcohols and alkenes. Catalysts based on cobalt, in particular dicobalt carbide and manganese on an activated carbon carrier, are used, which can contain additions of cerium, copper, zinc or lanthanum. Primary alcohols and alkenes with 2 to 30 carbon atoms are formed. The catalysts used here are said to have a high selectivity for alkenes, it being mentioned that alkenes formed can be further converted to alcohols by hydroformylation. Depending on the type of catalyst used, the catalytic conversion of the synthesis gas about 23 to 28 wt .-% alkanes, about 36 to 41 wt .-% alkenes and about 20 to 21 wt .-% higher alcohols, with about 8 wt .-% methane and about 2 to 5 % By weight of carbon dioxide and about 1 to 2% by weight of methanol are formed.

No. 8,129,436 B2 describes a method for producing an alcohol mixture from synthesis gas, a mixture of alcohols and oxygen-containing compounds being obtained. It is proposed to strip the product mixture with a methanol-containing stream in order to remove a portion of the carbon dioxide and inert gases contained in the product stream. In addition, dehydration can take place downstream in order to convert some of the ethanol formed and, if appropriate, propanol into the corresponding alkenes. Potassium-modified molybdenum sulfide catalysts are used to convert the synthesis gas. In this known process, very complex product mixtures are obtained which contain no alkenes, smaller amounts of alkanes, in addition to C2-C5 alcohols, sometimes higher proportions of methanol and many other oxygen-containing compounds such as aldehydes, carboxylic acids, ketones, esters, ethers and also mercaptans and Contain alkyl sulfides.

US 2010/0005709 A1 describes alternative fuel compositions which contain ethanol, isopropanol and butanols, with synthesis gas first being converted into a C2-C4 alkene stream by a Fischer-Tropsch synthesis and then these alkenes being hydrated. The alcohols obtained can be mixed with gasoline to obtain fuel compositions. In the conversion of the synthesis gas described in this document, only about 39% hydrocarbons with 2 to 4 carbon atoms are obtained, while about 40% higher hydrocarbons, cycloalkanes and aromatic compounds with C5 to C20 are formed, as they are usually contained in gasoline or diesel. In this hydration of the C2-C4-alkenes, only a maximum of 39% alcohols can be obtained, which, in addition to ethanol, are secondary alcohols and tertiary butanol. Methanol, 1-propanol and 1-butanol are not formed. In this known method, iron-manganese catalysts with proportions of zinc oxide and potassium oxide are used in a variant of the Fischer-Tropsch synthesis. This conversion produces almost exclusively C2-C4-alkenes as well as 9.6% methane and 15.7% C2-C4-alkanes, while primarily no alcohols are formed, so that the alcohols are only obtained in a further step by hydrating the alkenes . Since the product mixture is then mixed with gasoline to form a fuel, it is not absolutely necessary to separate off the alkanes or the compounds with 5 carbon atoms or longer carbon chains. US Pat. No. 5,237,104 A describes a process for the hydroformylation of a hydrocarbon-containing feed stream using a cobalt-containing catalyst. In hydroformylation, the aim is to produce higher alcohols and aldehydes by chain extension, in which case the hydrocarbon-containing feed stream is reacted with a synthesis gas. In this known method, the aim is to separate the cobalt compounds from the mixture in the course of the preparation of the product mixture. For this purpose, the volatile cobalt compounds are brought into contact with an olefinic absorbent which has a higher molecular weight and comprises, for example, a chain with 10 to 14 carbon atoms.

US Pat. No. 4,510,267 A describes a process for the production of alkenes from synthesis gas, in which ruthenium catalysts on a cerium oxide support are used. The catalyst is reported to be selective for the production of alkenes with a low methane content. In order to keep the methane yield low, a low molar ratio of hydrogen to carbon monoxide in the synthesis gas is recommended. In addition to methane, C2-C6 alkenes and, in smaller quantities, C2-C6 alkanes are formed. Separation processes for the separation of the product mixture are not described in this document. Alcohols (methanol and ethanol) are only formed in very small quantities.

US 2014/0142206 A1 describes a method for producing a catalyst comprising cobalt and molybdenum on a carbon support. The catalyst is used for the production of alcohols from synthesis gas, an increased yield of C2 and C3 alcohols being described. The conversion takes place under the conditions of a Fischer-Tropsch synthesis. Separation processes for obtaining individual product groups or individual compounds from the product mixture obtained after the reaction are not described in this document.

General Description of the Present Invention

In the above-mentioned Carbon2Chem® process, steel mill gases are used and processed in such a way that a synthesis gas is produced, which is basically suitable for the production of chemical compounds. This synthesis gas can be converted into higher alcohols in a catalytic synthesis. Due to the different composition of the synthesis gas and the differences in the conditions of the subsequent conversion of the synthesis gas, the product mixture obtained in the process described in the present application differs from that of a classic Fischer-Tropsch synthesis in which natural gas is used. After the catalytic synthesis of higher alcohols by converting a synthesis gas obtained from steel mill gases, a gaseous mixture is obtained which contains hydrogen, carbon monoxide, nitrogen, carbon dioxide, methane and water as well as various alkanes, in particular ethane, propane, butane, pentane, the corresponding alkenes, in particular Ethylene, propylene, 1-butylene, 1-pentylene and alcohols, in particular methanol, ethanol, 1-propanol, 1-butanol, and possible isomers of these alcohols, in particular 2-propanol, isobutanol, tert-butanol, 2-butanol, where the latter are not explicitly considered here, since their behavior essentially corresponds to that of 1-propanol or 1-butanol. Only a few percent of the gaseous product stream are valuable materials, especially the alcohols and the alkenes. For example, up to 90% or more are light gases that noticeably hinder the condensation of the product mixture.

The object of the present invention is to provide an improved method for processing a gaseous mixture of substances obtained by the catalytic conversion of synthesis gas, in which the light gases are largely separated and then the product mixture is further processed in such a way that the Valuables contained in this, in particular the alcohols and alkenes, can be recovered as completely as possible.

The solution to the aforementioned object is provided by a method for processing a gaseous substance mixture of the type mentioned at the beginning with the features of claim 1.

According to the invention, the preparation of the gaseous substance mixture comprises at least the following steps:

Separation of the product mixture into a gas phase and a liquid phase by at least partial absorption of the alkenes, optionally the alcohols and optionally the alkanes in a high-boiling hydrocarbon or hydrocarbon mixture as the absorption medium;

Separation of the gases not absorbed in the absorption medium as a gas phase; Separation of an aqueous phase from the organic phase of the

Absorption medium, preferably by decanting;

Desorption of the alkenes, optionally the alcohols and optionally the alkanes, from the absorption medium.

If one would like to use a synthesis gas obtained from steel mill gases within the scope of the present invention, one can proceed as follows, for example. If necessary, blast furnace top gas and converter gas are cleaned, for example in these gases to remove contained solids and / or catalyst poisons. If coke oven gas is also used, cleaning it using pressure swing adsorption (PSA), for example, is advantageous, so that primarily hydrogen is obtained from the coke oven gas. If necessary, the hydrogen content of the synthesis gas can be increased by adding hydrogen generated by electrolysis using electricity from renewable energies. The carbon dioxide content of the synthesis gas can optionally be reduced by a reverse water gas shift reaction, in which the carbon dioxide is converted into carbon monoxide. The processed synthesis gas obtained from steel mill gases in this way comprises carbon monoxide, hydrogen and nitrogen as its main components.

This synthesis gas is then used to carry out a catalytic conversion into higher alcohols, which is also referred to in the specialist literature as “mixed alcohol synthesis” (see, for example, WO 2008/048364 A2). According to the invention, this catalytic synthesis of the higher alcohols from synthesis gas can be carried out, for example, at reaction temperatures from 200 ° C to 360 ° C, preferably at temperatures from 220 ° C to 340 ° C, more preferably at 240 ° C to 320 ° C, in particular at 260 ° C to 300 ° C, for example at about 280 ° C. In addition, this reaction can be carried out, for example, at a reaction pressure of 10 bar to 110 bar, in particular at 30 bar to 90 bar, preferably at 50 bar to 70 bar, for example at about 60 bar.

In this synthesis, a product stream is obtained which is present at a temperature, for example, in the aforementioned range and at a high pressure in the order of magnitude mentioned, so that this product stream is preferably first converted into a manageable form, for example by expansion in a turbine. With this pressure reduction to a pressure of, for example, 5 bar to 15 bar, in particular to about 10 bar, electrical energy is obtained that can be used to cover a major part of the electricity requirement of the process.

The composition of the product mixture obtained in this catalytic synthesis of higher alcohols can vary widely. The product mixture contains in particular alcohols, alkenes, alkanes, carbon monoxide and hydrogen from unconverted synthesis gas, carbon dioxide, nitrogen and methane. The composition of the product phase depends on the composition of the synthesis gas used, in particular its inert gas content (nitrogen content) and the degree of conversion in the catalytic reaction, which results in the remaining carbon monoxide and hydrogen and possibly carbon dioxide and the ratio of the products to the residual gas. Furthermore, the selectivity of the catalyst used determines the distribution of the desired products, the means the alcohols, alkenes, the proportion of alkanes as well as the proportion of gaseous by-products that arise during the reaction, in particular methane and carbon dioxide.

The synthesis gas not converted in the reaction is preferably returned to the step before the conversion, so that proportions of hydrogen and carbon monoxide contained in this gas can be used in a renewed conversion. If the synthesis gas used contains, for example, a proportion of 30% by volume of nitrogen, which is inert in relation to the desired conversion, less recirculation of unconverted synthesis gas is necessary than if the synthesis gas used, for example, has a proportion of 50% by volume. % contains nitrogen. If the nitrogen content in the synthesis gas is lower and is only 10% by volume, for example, nitrogen can be separated using an additional membrane before the actual separation process.

The amount of absorption medium that is used in the first separation step depends on the degree of conversion and thus the resulting product composition. If a larger amount of absorption medium is used, more alkenes and alkanes are separated from the product mixture, although it should also be taken into account that more undesirable gases, in particular nitrogen, carbon dioxide, carbon monoxide and hydrogen, are also absorbed at the same time.

Through the first separation step, which can also be referred to as a gas-liquid separation, a separation of the predominant part of the gases, in particular nitrogen, carbon monoxide, carbon dioxide, hydrogen and methane, is achieved in the process according to the invention, since these gases hardly ever are absorbed in the absorption medium, the high-boiling hydrocarbon or hydrocarbon mixture. The separated gases can be returned to the previous process step of the catalytic conversion of synthesis gas. Two liquid phases are formed, namely an aqueous phase and an organic phase comprising the absorption medium. Organic compounds which are regarded as valuable substances in the process according to the invention, in particular alcohols and alkenes and also alkanes, go predominantly into the organic phase, and to a lesser extent also into the aqueous phase. Short-chain alcohols, in particular methanol and ethanol, mainly go into the aqueous phase. In a second separation step, the aqueous phase is separated from the organic phase of the absorption medium, preferably by decanting. Then alcohols, alkenes and optionally alkanes are desorbed from the absorption medium.

According to a preferred development of the process according to the invention, the mixture obtained after the desorption comprises alkenes, optionally alkanes and optionally alcohols are then separated by a first distillation into a fraction predominantly containing the hydrocarbons and a fraction predominantly containing the alcohols.

This distillation is preferably carried out at an elevated pressure, which is preferably in a pressure range from about 10 bar to about 40 bar.

According to a preferred development of the process according to the invention, the hydrocarbons separated off in the first distillation are then separated from the alcohol and water residues contained in the hydrocarbons in an extractive distillation with water. This extractive distillation is also referred to as a second distillation in the present application for the purpose of differentiation. This second distillation serves to further purify the previously separated hydrocarbons. In this extractive distillation in a column, the hydrocarbons are obtained at the top of the column, while some of the water is also obtained in the bottom of the column, alcohols generally still being dissolved in this water. The product mixture from the bottom of the column is preferably recycled in order to recover the alcohols contained in the water.

According to a preferred development of the process according to the invention, alcohols which are contained in the aqueous phase after the separation of the aqueous phase from the organic phase, preferably after decanting, are removed by distillation, the alcohols being obtained as an azeotrope with water at the top Water separated. This distillation, which is used to obtain further alcohols from the aqueous phase, is also referred to as the third distillation in the present application for better differentiation from the other separation steps.

The alcohols separated off from the water in this third distillation are preferably fed to the mixture obtained after the desorption and separated from the hydrocarbons with this mixture by the first distillation. In this way, a higher alcohol content can be obtained in the first distillation, which is used to separate the alcohols from the hydrocarbons, since those alcohols are also obtained that have gone into the aqueous phase during decanting without the need for a separate distillation device .

According to a preferred development of the invention, the alcohol fraction obtained in the first distillation, in which the alcohols are separated from the hydrocarbons, is then preferably dehydrated by means of a molecular sieve. The alcohol fraction can for example, have a water content of the order of about 10% or less after the first distillation. In order to dewater the alcohol fraction, alternative possibilities to the dehydration mentioned here by means of a molecular sieve will be mentioned later. After dehydration, an alcohol mixture is obtained which contains in particular methanol, ethanol, propanols and butanols.

According to a preferred development of the method according to the invention, this alcohol mixture obtained after the first distillation can then be separated into alcohol fractions, each with a different number of carbon atoms, for example by one or more further distillation steps, in particular into a C1 fraction, a C2 fraction, a C3 Fraction and a C4 fraction.

A possible variant of the process according to the invention provides that alkenes contained in the hydrocarbon mixture obtained after the first distillation are converted to alcohols, if appropriate after further work-up by hydration. This measure allows the overall yield of alcohols obtained in the process to be increased. There is also the advantage that alcohols can be separated more easily from alkanes, while alkanes and alkenes are difficult to separate because of their chemical similarity.

The hydration of alkenes to the corresponding alcohols is a known reaction for the preparation of alcohols and is used industrially, for example for the production of isopropanol from propene. With the exception of ethene, the hydration of the linear alkenes predominantly leads to the formation of secondary alcohols. Isobutene is hydrated to tertiary butanol, a tertiary alcohol.

There are essentially two known industrial processes for hydrating the alkenes to give the corresponding alcohols, on the one hand direct hydration and, alternatively, indirect hydration.

In direct hydration, the alkene is reacted with water over an acidic catalyst to form the respective alcohol. The hydration of the alkenes to alcohols is an equilibrium reaction. High pressures and low temperatures shift the equilibrium of the exothermic reaction on the product side in favor of the alcohols. The indirect hydration of the alkene takes place in a two-stage reaction. The alkene is first reacted with sulfuric acid to form mono- and dialkyl sulfates and then hydrolyzed to form alcohol.

Industrially, ethanol is mainly produced by fermenting carbohydrates, for example sugars from corn, sugar beet, grain or wheat. Synthetic ethanol can be produced from ethene via direct hydration. The direct hydration of ethene takes place in the gas phase on “solid” phosphoric acid (SPA catalysts), for example at 250-300 ° C and 50-80 bar. The hydration of ethene is an equilibrium reaction, with high pressures and low temperatures favoring the exothermic formation of the ethanol. Indirect hydration of ethene is no longer carried out industrially.

Various known methods are available for the direct hydration of propene. Low-temperature high-pressure processes (130-180 ° C, 80-100 bar) with, for example, sulfonated polystyrene ion exchange catalysts, high-temperature high-pressure processes (270-300 ° C, 200 bar) with, for example, reduced tungsten oxide catalysts and processes in the gas phase (250 ° C, 250 bar, W0 ₃ -Si0 ₂ catalyst, ICI process / 170-260 ° C, 25-65 bar, phosphoric acid catalyst on Si0 ₂ , Hüls process). Direct hydration of propene with steam under high pressure is carried out in Canada, Mexico and Western Europe. In the indirect hydration of propene, in addition to propene, the C3 stream from the refinery off-gas with a propene concentration of 40 - 60% can be used.

2-Butanol (secondary butyl alcohol) can be produced from butene or the MTBE raffinate by means of direct hydration or indirect hydration. 2-Butanol is used to manufacture methyl ethyl ketone (MEK).

According to a first variant of the invention, the use of a catalyst with a high selectivity for alcohols and alkenes is preferred, since the focus is on obtaining these product classes as valuable materials, while the formation of alkanes and oxygenated compounds such as aldehydes, esters, ethers, carboxylic acids, etc. , which are often obtained in higher proportions when using Fischer-Tropsch catalysts, is not desired in the process according to the invention. In addition, the subsequent separation processes in the preparation of the product mixture after the synthesis gas has been converted, the more complex the product mixture is. When converting synthesis gas using Fischer-Tropsch catalysts, this is less of a problem, since the product mixtures are often not separated into individual compound classes, but rather the mixture as such is used as an additive in fuels.

The synthesis of the higher alcohols usually gives a mixture of primary alcohols. By including hydration in the process, secondary alcohols can be formed selectively and thus the product range can be expanded. A more uniform product is created from the complex product mixture, which leads to advantages in the purification process and in marketing logistics. In principle, not only steel mill gases but also any other suitable synthesis gas sources come into consideration for the process according to the invention. When using steel mill gases, the method according to the invention has the advantage that a high proportion of nitrogen often contained in the steel mill gases can be easily separated off by the separation step of absorption in a higher-boiling hydrocarbon or hydrocarbon mixture. Nitrogen, which is the inert gas in the present process, must be separated off, since a high proportion of nitrogen would make the subsequent processing of the product mixture more difficult.

In the context of the present invention, an overall process was developed which enables higher alcohols (with two or more carbon atoms) to be produced with good yield starting from synthesis gas. In the present application, methods are described which, starting from the product mixture obtained in the conversion of synthesis gas, comprising carbon monoxide and / or carbon dioxide and hydrogen, offer advantages in economic, technological and / or ecological terms compared to known processes, in particular compared to just separation with subsequent individual marketing of the products / groups of substances. Particular attention was paid to optimizing the product separation in accordance with the synthesis steps. This concerns, among other things, the respective physical process conditions (pressure, temperature) as well as the setting of preferred or technologically tolerable educt ratios for the synthesis steps, taking into account, in particular, economic framework conditions.

Due to the large plant capacities, which are necessary, for example, for the utilization of significant quantities of steel mill gas, but also for other synthesis gas sources, processes are preferred that lead to products with sufficiently large (potential) markets. It is therefore particularly interesting to consider basic chemicals that can be used in the plastics or fuel sector, for example.

According to a possible preferred variant of the process according to the invention, the alkanes and alkenes are first separated from the alcohols from the first mixture of alkanes, alkenes and alcohols obtained after the catalytic conversion of synthesis gas and preferably after separation of the unconverted synthesis gas and only then are the alkenes in hydrated this second mixture.

The alcohols can be separated from the alkenes and alkanes with little effort. In contrast, the alkenes can only be separated from the alkanes with considerable effort. The Consecutive hydration of the alkenes to alcohols thus facilitates the separation process of alkenes and alkanes.

The separation of the alkene / alkane mixture into the individual Cx cuts or alkenes may also be advantageous, since this enables the individual alkenes to be hydrated separately. Alkenes, the respective hydration products of which are particularly suitable for the fuel market, or alkenes which can be hydrated under mild reaction conditions or inexpensively, can be converted selectively to the respective alcohols. Alkenes for which there is a corresponding alkene market can be separated from the respective C-cut and marketed. Furthermore, the reaction conditions for the hydration of the individual Cx cuts or alkenes can be selected independently of one another. For example, hydration of the C2 cut or of the ethene could be dispensed with and the ethene could instead be used for other applications in the chemical industry. Furthermore, a relatively pure alkane stream can be obtained in this way, which can be used for the generation of synthesis gas or energy. However, with this procedure, a separate system for hydrating the alkenes is required for each C cut, or the various fractions must be hydrated in batches.

According to an alternative preferred variant of the process according to the invention, the second mixture comprising the alkanes and alkenes contains a mixture of C2-C4 or a mixture of C2-C5 alkenes, which is then hydrated as a mixture to give the corresponding alcohols. In this variant, the hydration of an alkane / alkene mixture thus takes place without a previous separation of this mixture into different fractions with different numbers of carbon atoms being provided.

With regard to the reaction conditions for the hydration of such an alkene / alkane mixture, it must be taken into account that the conventional industrial processes are optimized for the conversion of the individual alkenes and differ from one another in the choice of the catalyst and the reaction conditions. For this step of hydrating the alkene / alkane mixture, in this variant of the invention it is therefore preferable to use process conditions which enable the conversion of all alkenes or promote the conversion of the preferred alkenes to the respective alcohols. Compared to the aforementioned process variant, the hydration of the alkene mixture offers the advantage that only one system is required for hydration or intermittent hydration of the various fractions can be dispensed with. After hydration, the alkanes are separated from the alcohols formed. The alkane stream remaining after the alcohols have been separated off can then be used, for example, to generate synthesis gas or energy.

According to a preferred further development of the process according to the invention, the conditions for the hydration of the alkane / alkene mixture with regard to the selection of the catalyst and the reaction conditions, in particular the temperature and the pressure at which the hydration reaction takes place, are chosen so that the hydration of propene and / or 1-butene is favored over that of ethene. It was found that with the catalysts which were used in the context of the present invention in the production of higher alcohols by catalytic conversion of synthesis gas, propene is predominantly formed as alkene. The CO selectivity of the conversion of the synthesis gas to the alkenes generally decreases in the order 1-propene> 1-butene> ethene. The industrial processes for hydrating 1-propene and 1-butene take place under milder reaction conditions than those of ethene, so that in this process variant it might be advantageous to concentrate on the hydration of propene and to neglect or neglect the hydration of ethene to dispense with the hydration of the ethene if necessary.

According to a preferred further development of the process according to the invention, the direct hydration is carried out at elevated temperatures and at elevated pressure. In principle, wide temperature ranges and wide pressure ranges are possible here, depending on which other conditions are selected. As a rule, the hydration takes place in the presence of an acid which acts as a catalyst.

For example, the alkenes can be hydrated at temperatures above 80.degree. C., in particular above 100.degree. C., for example at temperatures in the range from 100.degree. C. to 180.degree. C., preferably at 120 to 150.degree. C. and / or at a Pressure from 5 bar to 150 bar, in particular at a pressure from 10 bar to 100 bar, preferably at a pressure from 50 bar to 100 bar, for example at a pressure from 70 bar to 80 bar. The hydration of propene and 1-butene proceed under similar reaction conditions, for example at the aforementioned temperatures and pressures. In the industrial direct hydration of propene, conversions of, for example, up to about 75% per pass are achieved. For the direct hydration of the alkene / alkane mixture, the invention therefore proposes that the hydration reaction conditions for propene and 1-butene be based. In principle, it is also conceivable to hydrate the alkene / alkane mixture in several successive reactors with different Carry out catalysts and / or different reaction conditions and intermediate separation of the alcohols formed.

A third possible preferred variant of the process according to the invention provides that the alkenes are hydrated with the mixture of alkanes, alkenes and alcohols without the alcohols having to be separated off from this mixture beforehand. The hydration of the alkenes in the mixture of alcohols, alkenes and alkanes obtained in the reaction of the synthesis gas, without prior separation of the alcohols contained in this mixture, can, for example, offer the advantage that the reaction mixture is already at a comparatively high pressure of, for example, about 60 bar is present and therefore only needs to be preheated to the reaction temperature.

At a reaction temperature of, for example, about 150 ° C., hydration of the alkenes to give the alcohols is thermodynamically preferred. Tests in the context of the synthesis of the higher alcohols with specific catalysts and subsequent hydration and calculations for an equilibrium reactor clearly show that when the hydration is carried out at an elevated temperature (for example up to 150 ° C.) and an elevated pressure of, for example, 2 bar to 100 bar a conversion of the alkenes and the primary C ₃₊ alcohols to the secondary alcohols takes place. In particular, propene and 1-butanol are mainly converted to isopropanol and 2-butanol. Ethene is hydrated to ethanol.

According to a preferred further development of the process according to the invention, the alkanes are separated off from the product mixture obtained after hydration and the remaining mixture of alcohols is optionally purified and / or separated into individual fractions of alcohols or individual alcohols. This again has the advantage that after hydration, in principle, only alcohols and alkanes are still present, even in the variant described above, in which the alcohols already obtained in the reaction of the synthesis gas in the first step are not separated off before the second hydration step. This means that there are only two substance classes in the mixture that can be easily separated from one another, while the separation of alkenes and alkanes would be much more difficult.

According to the process according to the invention, before the hydration of the alkenes to the corresponding alcohols and after the catalytic conversion of the synthesis gas, the step is preferably provided in which the product mixture obtained in this reaction is separated into a gas phase and a liquid phase, the liquid phase for the subsequent hydration of the alkenes to the alcohols is used. The gas phase separated off at this point can contain, for example, unconverted CO and H ₂ and also contain _{C0 2} , CH ₄ and N _2. According to a preferred variant of the process according to the invention, the gas phase obtained in this separation process, which generally contains the unconverted gases mentioned, can be at least partially returned to the step of catalytic conversion of the synthesis gas, in order in this way to reactivate the recycled reactant gases to higher alcohols to increase the yield of the entire process.

As an alternative to this, the alkenes can in principle also be hydrated before the product mixture obtained after the reaction of the synthesis gas is separated into a gas phase and a liquid phase. Here, the hydration takes place, for example, directly in a reactor downstream of the synthesis of higher alcohols and without prior separation of the product mixture. Propene and butene can be hydrated, for example, at about 150 ° C., while higher temperatures of, for example, about 230 ° C. to 260 ° C. are advantageous for the hydration of ethene. The hydration can take place at a lower temperature than the previous reaction of the synthesis gas, it being possible to choose temperatures of, for example, 120 ° C. to 150 ° C. for the hydration. It can therefore be advantageous to cool the product mixture for the hydration to temperatures of this order of magnitude.

Experiments, calculations and the simulation of the synthesis of higher alcohols with subsequent hydration show that under the reaction conditions of the synthesis of higher alcohols, the dehydration of the alcohols to the alkenes is thermodynamically preferred. If the reaction conditions for the synthesis of higher alcohols are, for example, about 280 ° C. and about 60 bar, almost complete conversion of the alcohols into the corresponding alkenes is possible.

At a reaction temperature of the order of magnitude of about 50 ° C., for example, hydration of the alkenes to give the alcohols is thermodynamically preferred. Tests in the context of the synthesis of the higher alcohols with specific catalysts and calculations or simulations of the subsequent hydration for an equilibrium reactor clearly show that when the hydration is carried out at, for example, about 50 ° C and a pressure of about 60 bar, a conversion of the alkenes and the primary Alcohols to the secondary alcohols takes place. In particular, propene and 1-butanol are predominantly converted to isopropanol and 2-butanol. Ethene is hydrated to ethanol.

With this purely thermodynamic consideration, however, it should be noted that the industrial processes for hydration usually take place at reaction temperatures of 130 - 260 ° C. It can therefore be assumed that the reaction at 50 ° C with a clearly slower reaction speed. This process variant is therefore less suitable for the hydration of the alkenes (or can only be carried out under certain framework conditions.)

Instead, one of the above-mentioned variants is to be preferred, in which the separation into a gas phase and a liquid phase initially takes place after the synthesis of higher alcohols, the product mixture being cooled after the synthesis of higher alcohols from the synthesis gas.

In the method according to the invention, there are in particular the following three preferred method variants:

In variant 1, the method preferably comprises the steps:

Production of higher alcohols (with at least two carbon atoms) and of alkenes by catalytic conversion of synthesis gas;

Separation of the product mixture obtained into a gas phase and a liquid phase;

Separation of the liquid phase into an aqueous and an organic phase;

Desorption of the alkenes, optionally the alcohols and optionally the alkanes, from the absorption medium;

Separating off the alkenes and, if appropriate, the alkanes formed as by-products from the alcohols obtained; optionally purification of the alcohol mixture separated from the alkenes and alkanes into individual compounds or groups of compounds, in particular ethanol, propanols, butanols and, if appropriate, methanol;

Separation of the mixture of alkenes and alkanes into several fractions each with a different number of carbon atoms, in particular C2, C3 and C4 fractions; in each case separate hydration of the previously obtained fractions, preferably by reaction with water, mixtures of alcohols and alkanes having the same number of carbon atoms being obtained in each case; optionally purification of the respective mixtures of alcohols and alkanes with the same number of carbon atoms into individual alcohols and alkanes.

In variant 2, the method preferably comprises the steps: Production of higher alcohols (with at least two carbon atoms) and of alkenes by catalytic conversion of synthesis gas;

Separation of the product mixture obtained into a gas phase and a liquid phase;

Separation of the liquid phase into an aqueous and an organic phase;

Hydration of the mixture of the alkenes and alkanes previously separated from the alcohols, preferably by reacting the alkenes with water, a mixture of alcohols and alkanes being obtained;

Separating off the alkanes from the mixture after hydration and, if appropriate, combining the alcohols obtained with the alcohols obtained previously in the synthesis; optionally purification of the alcohol mixture obtained into individual compounds or groups of compounds, in particular ethanol, propanols, butanols and, optionally, methanol.

In variant 3, the method preferably comprises the steps:

Separation of the product mixture obtained into a gas phase and a liquid phase;

Separation of the liquid phase into an aqueous and an organic phase;

Hydration of the previously obtained product mixture of the organic liquid phase comprising alcohols, alkenes and alkanes, preferably by reaction with water, the alkenes being hydrated as a mixture to the corresponding alcohols; Separation of the alkanes from the alcohols obtained; optionally purification of the alcohol mixture separated from the alkanes into individual compounds or groups of compounds, in particular ethanol, propanols, butanols and, if appropriate, methanol.

As an alternative to this, a fourth variant of the process is possible in which the alkenes are hydrated after the synthesis gas has been converted and before the product mixture obtained is separated into a gas phase and a liquid phase.

In variant 4, the method preferably comprises the steps:

Hydration of the product mixture obtained comprising alcohols, alkenes and alkanes, the alkenes being hydrated as a mixture to the corresponding alcohols;

Separation of the product mixture obtained into a gas phase and a liquid phase; optionally separation of the liquid phase into an aqueous and an organic phase; optionally desorption of the alcohols, optionally the alkenes and optionally the alkanes from the absorption medium;

Separating off the alkanes and, if appropriate, the alkenes present from the alcohols obtained; optionally purification of the alcohol mixture separated from the alkanes into individual compounds or groups of compounds, in particular ethanol, propanols, butanols and, if appropriate, methanol.

In all four of the aforementioned process variants, at least partial recycling of the gas phase for the synthesis of the higher alcohols after the gas-liquid separation is advantageous.

In addition to the aforementioned process variants, it is also possible to carry out the hydration of the alkenes by a combination of two or more of the aforementioned process variants. For example, the composition of the product mixture initially obtained by catalytic conversion of synthesis gas of higher alcohols (with at least two carbon atoms) and alkenes can be shifted by process variant 4 and, after separation of the product mixture then obtained, into a Gas phase and a liquid phase, the alkenes contained in the liquid phase are hydrated to the corresponding alcohols, for example by means of one of the process variants 1, 2 or 3. The combination of the two process variants can, for example, promote the isomerization of the primary alcohols to secondary alcohols. The isomerization of the primary alcohols to the secondary alcohols proceeds via the dehydration of the primary alcohols to the corresponding alkenes as intermediates. The dehydration proceeds preferably at higher temperatures than the hydration.

The provision of the synthesis gas for the inventive catalytic conversion to alcohols can include not only the preparation of the synthesis gas but also the purification and conditioning of the synthesis gas. Both fossil fuels, such as natural gas, coal, but also CO and C0 ₂ -rich gases, for example from steel and cement works and hydrogen, can be used as feed. It is also possible to obtain the synthesis gas used from biomass. The hydrogen is preferably produced in a sustainable manner by means of renewable energies and / or low C0 ₂ emissions, for example by means of water electrolysis or methane pyrolysis. The electricity for the operation of the hydrogen generation is preferably generated by means of renewable energies.

The liquid phase contains predominantly the alcohols, alkenes and optionally alkanes formed. By lowering the pressure to less than 50 bar, in particular to less than 30 bar, preferably to less than 20 bar, more preferably to less than 10 bar, for example 3 to 1 bar, preferably to about 1 bar, the alkenes and Alkanes are evaporated and separated from the product mixture. Other methods known to the person skilled in the art for separating the alkenes and alkanes from the alcohols are, however, likewise suitable here. In order to optimize the process economically and / or ecologically, it may be advantageous to convert the alkanes into synthesis gas, e.g. via partial oxidation, steam reforming or autothermal reforming and to return them to the process. If appropriate, the alkanes can also be dehydrated to the corresponding alkenes and then likewise hydrated in order to increase the yield of alcohols. The alcohols remain in the liquid phase and, after the water formed as a by-product has been separated off, are marketed as a product mixture, e.g. as a fuel additive, or separated into the individual alcohols in a distillation.

There is also the option of hydrating the alkenes after the alkanes have been separated off from the respective Cx cuts. This provides the advantage of a comparatively pure starting material concentration and the possibility of carrying out the hydration under industrially known conditions for the respective alkene. Due to the apparatus and However, this option is only feasible under certain framework conditions due to the energetic expenditure of separating alkanes and alkenes.

The various options for integrating the consecutive conversion of the alkenes to alcohols in the process concept for the synthesis of the higher alcohols differ in the composition of the reaction mixture and the prevailing process conditions, such as temperature and pressure, as well as in the type and time of the separation of the alcohols, alkenes and alkanes from the synthesis gas. By integrating the hydration of the alkenes into the process concept for the synthesis of the higher alcohols, it is possible to use the already existing temperature and pressure levels of the catalytic synthesis of higher alcohols for the hydration.

Primary alcohols are preferably formed in the catalytic synthesis of the higher alcohols from synthesis gas. The formation of the secondary alcohols is hardly observed. The hydration of the linear alkenes, on the other hand, preferentially leads to the formation of secondary alcohols such as isopropanol and 2-butanol (with the exception of ethanol). The synthesis of higher alcohols and the consecutive hydration of the alkenes thus differ in their product range.

If, on the other hand, the isomerization of the primary alcohols to the secondary alcohols is desired, a suitable process concept must be selected which ensures the isomerization of the primary alcohols to the secondary alcohols.

Due to the possible isomerization of the primary alcohols to secondary alcohols, the alcohols can be separated off from the hydrocarbon mixture (alkenes, alkanes), that is to say process variants 1 and 2 mentioned above are preferred for the hydration. The alcohols can be separated from the alkenes and alkanes with little effort. In contrast, the alkenes can only be separated from the alkanes with considerable effort. The consecutive hydration of the alkenes to alcohols thus facilitates the separation process of alkenes and alkanes.

According to a preferred development of the method according to the invention, the hydrocarbon mixture obtained after the first distillation is separated into fractions each having the same number of carbon atoms, in particular into a C3 fraction, a C4 fraction and a C5 fraction.

According to a possible variant of the process according to the invention, the alcohol fraction can be dehydrated by separating the lower alcohols methanol and ethanol from the alcohol fraction obtained in the first distillation in a column with a little water and the remaining alcohol mixture with a higher one Hydrocarbon is added and separated into an organic phase and an aqueous phase in a decanter. In this process variant, it can be advantageous to use a comparatively large amount of the higher hydrocarbon as the absorption medium so that most of the alcohols go into the organic phase. The aqueous phase can be sent back to the aforementioned decanter for work-up.

The alcohols are preferably stripped out of the organic phase in a further column and the remaining water contained in the alcohols is then removed by means of a molecular sieve.

According to an alternative variant of the process according to the invention, the lower alcohols, methanol and ethanol, are separated from the higher alcohols from the alcohol fraction obtained in the first distillation in an extractive distillation with a hydrophilic substance, in particular with ethylene glycol, and the higher alcohols are then separated from the higher alcohols in a further distillation column the hydrophilic substance is separated and water contained in the higher alcohols is then optionally removed as an azeotrope.

According to an alternative variant of the process, the water can also be selectively removed from the alcohol fraction obtained in the first distillation, for example by pervaporation through a membrane, and drawn off in vapor form as permeate.

Finally, according to a further alternative variant of the process, the water can also be removed from the alcohol fraction obtained in the first distillation, for example by azeotropic distillation with a selective additive, in particular with a higher hydrocarbon, preferably with butane or pentane.

It has already been mentioned above that one of the main concerns of the present invention is to obtain the valuable substances contained in the product mixture obtained after the catalytic conversion of the synthesis gas, the alcohols and alkenes in particular to be obtained here. Thus, according to the invention, the aim is preferably that at least the alcohols methanol, ethanol, propanol and butanol as well as the C4 olefins and C5 olefins and optionally C3 olefins and C2 olefins are obtained from the mixture of substances obtained after the catalytic conversion of synthesis gas.

Various substances come into consideration for the absorption medium which is used in the separation step to separate the inert gases from the product stream. The high-boiling hydrocarbon or the hydrocarbon mixture used as the absorption medium preferably comprises a diesel oil or an alkane, in particular a dodecane with a viscosity of less than 10 mPas at room temperature and / or a boiling point of more than 200 ° C.

The subsequent desorption of the alkenes, optionally alcohols and optionally alkanes, from the absorption medium is preferably carried out in a distillation column, preferably at a pressure of 1 bar to 5 bar.

According to an advantageous development, after the desorption, the absorption medium is returned to the absorption separation step after heat exchange.

The gas phase of the gases not absorbed in the absorption medium, which is separated from the product mixture after the catalytic conversion of the synthesis gas, preferably comprises at least the gases nitrogen, hydrogen, carbon monoxide, carbon dioxide and methane.

It has already been mentioned above that alkenes contained in the hydrocarbon mixture obtained after the first distillation can be converted to alcohols by hydration according to an optional variant of the process according to the invention, optionally after further work-up, in order to increase the proportion of alcohols in the product mixture increase and simplify the separation of the product classes. For example, such a hydration of the reaction mixture consisting of alcohols, alkenes and alkanes can be carried out at a temperature of about 150.degree. As can be shown on the basis of simulations and calculations of the thermodynamic equilibrium, the mixture of alkenes and primary alcohols is almost completely converted into secondary alcohols under these reaction conditions. The isomerization of the primary alcohols into the secondary alcohols presumably takes place via the formation of the alkenes as intermediates. The hydration of the product mixture in the synthesis of higher alcohols from alcohols and alkenes thus offers the possibility of shifting the product spectrum in the direction of secondary alcohols. The industrial hydration of propene and 1-butene takes place at reaction temperatures of 120 to 150 ° C., for example.

The consecutive hydration of the alkenes formed as by-products in the catalytic synthesis of higher alcohols enables the alcohol yield to be increased if the reaction is carried out appropriately. Furthermore, this equilibrium reaction basically offers the possibility of converting the complex reaction mixture of primary alcohols and alkenes into secondary alcohols by means of dehydration and hydration steps (with the exception of ethanol). The reduction in products leads to a low number of products Purification steps of the individual products and facilitates the marketing of the products of the higher alcohol synthesis.

The present invention is described in more detail below on the basis of exemplary embodiments with reference to the accompanying drawings. It shows:

FIG. 1 shows a schematically simplified representation of an exemplary separation process for processing and separating a gaseous mixture of substances which was obtained by catalytic conversion of synthesis gas.

A possible method for separating a product mixture obtained in the catalytic conversion of synthesis gas is described below by way of example with reference to the simplified reaction scheme according to FIG. 1. The exemplary method for separation described below describes the separation of the mixture of alcohols, alkenes and alkanes obtained by the reaction of the synthesis gas from the gas phase and its subsequent separation into a mixture of alcohols and a mixture of hydrocarbons. When using the different process variants and converting the product mixture obtained, the individual steps of this process for separating the product mixture can be varied and adapted to the product mixture obtained after the conversion.

Inert gas removal and gas-liquid separation

After the catalytic conversion of a synthesis gas stream under the conditions of the process according to the invention, a product stream is present at a temperature of 280 ° C. and a pressure of 60 bar. This is first expanded in a turbine (not shown in FIG. 1) to a pressure of 5 to 20 bar, preferably to about 10 bar, whereby electrical energy is obtained that can be used for the power requirement of the process.

The subsequent gas-liquid separation serves in particular to separate the inert gases (nitrogen) and unconverted components of the synthesis gas (hydrogen, carbon monoxide and optionally carbon dioxide and the by-products carbon dioxide and methane) and is carried out by introducing the raw product gas stream 10 into an absorption device 11, in which the product stream is absorbed in a diesel oil (reference component dodecane) or alternatively in an alkane or a hydrocarbon mixture with a comparatively low viscosity of, for example, less than 10 mPas at room temperature and preferably with a comparatively high boiling point of in particular more than 200 ° C. The water will not do this absorbed, but largely condensed as a second liquid phase. The above-mentioned gaseous components which have been separated off can be returned to the catalytic conversion of the synthesis gas (not shown here) via line 12 and converted there again.

The two liquid phases (organic phase and aqueous phase) occurring during this absorption process, which can take place at a pressure of, for example, about 10-20 bar, can then be separated in a decanter 13 go aqueous phase. The separation of the two liquid phases in the decanter 13 can, for example, also take place at the aforementioned pressure of approximately 10-20 bar. The organic phase which is separated off contains the hydrocarbons, at least some of the alcohols, the absorption medium, possibly some of the water and any remaining proportions of inert and unconverted gases, in particular nitrogen and carbon monoxide, and is fed via a line 14 to a desorption device 15 in which the alcohols and hydrocarbons are desorbed from the absorption medium, for example at a lower pressure, for example at a pressure of about 1 bar and a bottom temperature of 216 ° C. A column, for example, can be used as the desorption device 15. In the case of smaller proportions of inert gas in the product stream of the catalytic conversion of synthesis gas, a condensation of the low-boiling components can alternatively also come into consideration. The absorption medium (dodecane, diesel oil) can be returned to the absorption device 11 via the line 16.

Separation of alcohols / hydrocarbons

The organic phase desorbed from the absorption medium in the desorption device 15, which contains the alcohols, hydrocarbons, small amounts of water and, if appropriate, proportions of unreacted and inert gases, is then fed via a line 18 to a first distillation column 17. The separation of alcohols and hydrocarbons is carried out by distillation in this first column, preferably at a high pressure of, for example, 10 bar to 40 bar, for example at about 36 bar and a bottom temperature of, for example, 221 ° C., so that the C3 components are also present any residues of inert gas that may be present still remain condensable. This separation is preferably carried out in such a way that the hydrocarbons are practically completely removed from the alcohol fraction at the bottom, while lower alcohol contents (in particular methanol) in the hydrocarbons can be tolerated. If necessary, this process can be supported by a solubility-driven membrane become. The alcohols obtained in this first distillation, which still contain a proportion of water, can be removed from the first distillation column 17 via line 19 from the bottom and dried, as will be explained in more detail below.

Representation of the hydrocarbons

The hydrocarbons obtained at the top in the first distillation column 17 can be fed via a line 20 to a second distillation column 21, in which they are at an elevated pressure of preferably 5 bar to 20 bar, for example at a pressure of about 10 bar and a bottom temperature of 102 ° C can be obtained at the top of the distillation column 21 and can be removed via the product line 22 for further purification and, if necessary, separation into individual C fractions (not shown in FIG. 1). The alkanes optionally contained in the product stream 22 of hydrocarbons can be separated from the alkenes by preferably hydrating the alkenes so that they are converted to alcohols which can then be separated from the alkanes comparatively easily, for example by distillation.

The remaining water and the alcohols dissolved therein are obtained in the bottom of this second distillation column 21. This stream is separated off and can be returned to a third distillation column 24 via line 23 for recovery of the alcohols. The condenser of the column can, for example, be a partial condenser. The outputs of the column are a gas phase made of hydrocarbons and inerts, a liquid phase made of hydrocarbons and an aqueous phase that can return to the column as reflux.

The third distillation column 24 is fed via line 28 with the aqueous phase separated from the organic phase in the decanter 13, which may contain fractions of the alcohols, since these are at least partially soluble in water, in particular the lower alcohols such as methanol and ethanol. The distillation in this third distillation column 24 can take place, for example, at a pressure of about 2 bar and at a temperature in the bottom of, for example, about 120.degree. The alcohols contained in this aqueous fraction are obtained at the top of the third column and fed via line 29 to the first distillation column 17 and there combined with the mixture of alcohols and hydrocarbons from the organic phase, so that these alcohols recovered from the aqueous phase in the The first distillation column 17 with the remaining alcohols is separated off and then dried over the molecular sieve 25, for example can be. The water separated off in this third distillation column can, for example, be discharged from the plant as waste water via line 30.

In this way, by means of the separation scheme shown in an exemplary and simplified manner in FIG. 1, the valuable substances alkenes and alcohols can be obtained as separate product groups from the raw gas product mixture 10 by absorption in a high-boiling hydrocarbon or hydrocarbon mixture, subsequent decanting for phase separation and subsequent multiple distillation.

Dehydration of the alcohol fraction

The alcohol fraction from the first distillation column 17 can have a water content of, for example, about 10%. This water can be removed by means of a molecular sieve 25, for example. In this process variant, the alcohols are fed via line 19 to molecular sieve 25, by means of which they are dewatered, the water being able to be discharged from the system via line 26. The alcohols dried in this way can be discharged via the product line 27 and optionally further separated, for example into individual C fractions (isomeric alcohols each with the same number of carbon atoms) or into individual specific alcohols.

An alternative method for removing the water from the alcohol fraction is extractive distillation, for example with ethylene glycol, which, however, requires a further separation step, since the water is drawn into the sump from the ethylene glycol, while the alcohols methanol and ethanol are practically anhydrous overhead. About half of the propanol remains and the butanol remains entirely in the bottom and these C3-C4 alcohols must also be removed from the ethylene glycol via the top in a subsequent column.

The third alternative is pervaporation. Water passes selectively through a membrane and is withdrawn in vapor form as permeate. The energy consumption is even lower than with a molecular sieve.

Another alternative method would be an azeotropic distillation, e.g. with butane or pentane as a selective additive.

Examples of the composition of the product mixture obtained after the catalytic conversion of the synthesis gas

In the context of the present invention, it was investigated how the variation of various parameters affects the composition of the after the catalytic conversion of the Effect of synthesis gas obtained gaseous mixture of substances. The results are given in the following examples.

example 1

In Example 1 below, an exemplary product composition is given which was obtained in the catalytic conversion of synthesis gas by the process according to the invention. The catalyst used had a high C2-C4 selectivity, with alcohols, alkenes and alkanes being formed. A catalyst was used which comprises grains of non-graphitic carbon with cobalt nanoparticles dispersed therein. The CO selectivity for the conversion to alcohols is about 28%, the CO selectivity for the conversion to alkenes is about 32%. The exact CO selectivities of the catalytic conversion of the synthesis gas result from the following table 1. The selectivities given in table 1 were based on the products detected in the catalytic tests (C1-C5-alcohols, C1-C5-alkenes and C1-C5- Alkanes, C0 ₂ ) standardized. The analysis of the CO conversion suggests that long-chain C ₆₊ alcohols, C ₆₊ alkenes and C ₆₊ alkanes and possibly aldehydes are formed in addition to the detected products mentioned.

Table 1 A powdery catalyst was used in this example. Alternatively, the catalyst can also be pressed into tablets, for example.

Table 1 above shows that in the catalytic conversion of synthesis gas according to the invention, a comparatively high proportion of alcohols in addition to the alkenes can be obtained when a suitable catalyst is used. The proportion of alkanes in the product mixture is lower in comparison. The alkenes can also be converted to alcohols in the subsequent hydration step, so that, including the subsequent hydration step, the synthesis gas can be converted to alcohols with a CO selectivity of almost 60%, with primary alcohols (methanol, ethanol, 1-propanol and 1 -Butanol) from the alcohol synthesis and ethanol and secondary alcohols (2-propanol, 2-butanol and optionally 2-pentanol) can be obtained from the hydration step and the methanol content is comparatively low. Such an alcohol mixture is suitable, for example, as a fuel additive for admixture with gasoline. Alternatively, separation into the individual alcohols is possible.

For comparison, a CO _{0, i} 26Mo was used _0.2 55C-catalyst, as described in US publication US 2014/0142206 A1 in Example 2. Fig. The ratio of H ₂ to CO in the synthesis gas was 1: 1. After the synthesis gas had reacted, a composition according to Table 1a below was obtained.

Table 1a

Table 1a above shows that when this catalyst is used, predominantly alcohols are formed, the proportion of methanol being comparatively high, while only a little 1-butanol is formed. C2-C6 hydrocarbons are only formed in small quantities. For further comparison, a catalyst with high selectivity to olefins, as described in Example 2 of US Pat. No. 4,510,267 A, was used. After the synthesis gas had reacted, a composition according to Table 1b below was obtained. The composition of the synthesis gas in this case was H ₂ : CO = 1: 1. The selectivities (% by weight) stated in US Pat. No. 4,510,267 A and in Table 1b were converted into CO selectivities for comparison with the results in Table 1 and to simulate the separation process. The selectivity to C0 ₂ was determined based on the difference of 100% and the sum of all products. For the simulation of the separation process, the Cn ₊ alkanes and the Cii ₊ alkenes were assumed to be undecane and undecene, respectively.

Table 1b

Table 1b above shows that predominantly alkenes are formed here, but also a comparatively high proportion of methane. However, only a small amount of alcohol, namely ethanol, is formed.

For further comparison, the implementation was simulated with a Fischer-Tropsch reactor and a catalyst, as described in the literature by Syed Naqvi, SRI Consulting, Menlo Park California 94025 in PEP Review 2007-2, December 2007 on page 5 in the right-hand column of Table 1 is described. The composition of the product mixture is shown in Table 1c below.

Table 1c Table 1c above shows that a large number of compounds are formed here, namely higher alkanes with up to 20 carbon atoms, higher alkenes, aromatic hydrocarbons, alcohols with up to 19 carbon atoms. The proportion of methane was 8%. A total of 30% compounds with C2-C4 were formed, 36% compounds with C5-C11, 12% compounds with C12-C19, 5% compounds with more than 19 carbon atoms and 5% oxygenates. The selectivity of the formation of CO ₂ is not shown.

Example 2

In this example, the distribution of the compounds of the product mixture formed after the synthesis of higher alcohols is illustrated in the three phases that form after the separation step with the absorbent (in this example dodecane) Catalyst according to Example 1, Table 1 has arisen. The catalyst comprised grains of non-graphitic carbon with cobalt nanoparticles dispersed therein. In the example according to Table 2a the assumed CO conversion was 50%, while in the example according to Table 2b it was 75%. The different CO conversions in the individual examples are achieved by the catalytic conversion of the synthesis gas in one or more reactors connected in series with the intermittent addition of hydrogen to set the H ₂ : CO ratio of H ₂ : CO = 1: 1.

Example no.2a: Variation of CO conversion catalyst: (see above)

Composition synthesis gas absorbent

Molar flow molar fraction molar flow

[kmol / h] [%] [kmol / h]

H ₂ 5,000 35%

CO 5,000 35%

N ₂ 4,280 30% n-dodecane 3,528 Table 2a

Sales CO: 50%

Raw gas Gas phase Liquid Aqueous Org. Total mol absorbed 10 12 phase 28 phase / mol dodecane

14 mol / h

H ₂ 175 100% 0% 0% 0% 100% 5.0E-02

CO 2,501 99% 1% 0% 1% 100% 7.1E-01 co ₂ 245 93% 7% 0% 7% 100% 6.9E-02

CH ₄ 447 97% 3% 0% 3% 100% 1,3E-01

N ₂ 4,280 99% 1% 0% 1% 100% l, 2E + 00

MeOH 93 1% 99% 82% 18% 100% 2,6E-02

EtOH 57 0% 100% 68% 32% 100% 1,6E-02

1-PrOH 9 0% 100% 43% 57% 100% 2,6E-03

1-BuOH 114 0% 100% 18% 82% 100% 3.2E-02

H ₂ 0 1,737 1% 99% 98% 1% 100% 4.9E-01

Ethane 57 82% 18% 0% 18% 100% 1,6E-02

Propane 36 43% 57% 0% 57% 100% 1.0E-02 n-butane 19 0% 100% 0% 100% 100% 5.3E-03 n-pentane 1 0% 100% 0% 100% 100% 3.4E-04

Ethene 76 89% 11% 0% 11% 100% 2, lE-02

Propene 126 53% 47% 0% 46% 100% 3,6E-02

1-butene 45 0% 100% 0% 100% 100% l, 3E-02

1-penten 21 0% 100% 0% 100% 100% 6.0E-03 n-Dodecanese 3,528 0% 100% 0% 100% 100% l, 0E + 00

Example No. 2b: Variation of CO conversion catalyst: as in Examples 2 and 2a

Composition synthesis gas absorbent molar flow mole fraction molar flow

[kmol / h] [%] [kmol / h]

H ₂ 5,000 35%

CO 5,000 35%

N ₂ 4,280 30% n-dodecane 3,528

Table 2b

CO turnover: 75%

Raw gas gas phase liquid aqueous org. Total mol absorbed 10 12 phase phase / mol dodecane

28 14 mol / h

H ₂ 88 99% 1% 0% 1% 100% 1.3E-04

CO 1,251 99% 1% 0% 1% 100% 3.8E-03

C0 ₂ 367 92% 8% 0% 8% 100% 8.7E-03

CH ₄ 671 96% 4% 0% 4% 100% 7.3E-03

N ₂ 4,280 99% 1% 0% 1% 100% 7.9E-03

MeOH Ϊ39 ^~~ 0% 100% 86% 14% 100% 3.9E-02

EtOH 86 0% 100% 73% 27% 100% 2.4E-02

1-PrOH 14 0% 100% 50% 50% 100% 4.0E-03

1-BuOH 171 0% 100% 24% 76% 100% 4.9E-02

H ₂ 0 2.606 1% 99% 99% 0% 100% 7.3E-01

Ethane 86 80% 20% 0% 20% 100% 5.0E-03

Propane 54 36% 64% 0% 64% 100% 9.7E-03 n-butane 28 0% 100% 0% 100% 100% 8.0E-03 n-pentane 2 0% 100% 0% 100% 100% 5.1E -04

Ethene 113 87% 13% 0% 13% 100% 4.1E-03

Propene 189 48% 52% 0% 52% 100% 2.8E-02

1-butene 67 0% 100% 0% 100% 100% 1.9E-02

1-Penten 32 0% 100% 0% 100% 100% 9.0E-03 n-Dodecanese 3,528 0% 100% 0% 100% 100% 1.0E + 00 Example 3

In the following example, the proportion of inert gas in the feed gas stream of the synthesis gas which was catalytically converted to higher alcohols, i.e. the nitrogen content, varied by 10%, 20% and 30% (Examples 3a, 3b and 3c). It was found that the proportion of the lower alkenes and alkanes absorbed by the liquid organic phase in the step of absorption of the product mixture in the high-boiling hydrocarbon in each case decreases as the proportion of inert gas increases. This applies to ethane, propane, ethene and propene, while the higher alkanes and alkenes from C4 in each case transfer 100% into the liquid organic phase.

Example no. 3a: Variation of the proportion of inert gas catalyst: as in Examples 2, 2a and 2b

Composition synthesis gas absorbent

Molar flow molar fraction molar flow

[kmol / h] [%] [kmol / h]

H ₂ 5,000 45% -

CO 5,000 45%

N ₂ 1,110 10% n-dodecane 3,528

Table 3a

Sales CO: 50%

Raw gas gas phase liquid water org. Total mol absorbed 10 12 phase phase / mol dodecane mol / h phase 14 28

H ₂ 175 99% 1% Ö% 1% 100% 3.6E-04

CO 2,501 98% 2% 0% 2% 100% 1.1E-02

C0 ₂ 245 88% 12% 0% 12% 100% 8.5E-03

CH ₄ 447 94% 6% 0% 6% 100% 7.1E-03

N ₂ 1.110 99% 1% 0% 1% 100% 3.0E-03

MeOH 93 0% 100% 82% 18% 100% 2.6E-02

EtOH 57 0% 100% 66% 34% 100% 1,6E-02

1-PrOH 9 0% 100% 42% 58% 100% 2.6E-03

1-BuOH 114 0% 100% 18% 82% 100% 3.2E-02

H ₂ 0 1,737 1% 99% 99% 1% 100% 4.9E-01

Ethane 57 70% 30% Ö% ^~ 30% 100% 4.9E-03

Propane 36 8% 92% 0% 92% 100% 9.4E-03 n- butane 19 0% 100% 0% 100% 100% 5.3E-03 n- pentane 1 0% 100% 0% 100% 100% 3.4E -04

Ethene 76 81% 19% 0% 19% 100% 4.0E-03

Propene 126 19% 81% 0% 81% 100% 2.9E-02

1-Butene 45 0% 100% 0% 100% 100% 1, 3E-02

1-penten 21 0% 100% 0% 100% 100% 6.0E-03 n-Dodecanese 3,528 0% 100% 0% 100% 100% 1.0E + 00

Example no. 3b: Variation of the proportion of inert gas

Catalyst: _ as in example 3a _

Composition synthesis gas absorbent

Molar flow molar fraction molar flow

[kmol / h] [%] [kmol / h]

H ₂ 5,000 40% -

CO 5,000 40%

N ₂ 2,500 20% n-dodecane 3,528

Table 3b

Sales CO: 50% _

Raw gas gas phase liquid water org. Total mol absorbed

10 12 phase phase / mol dodecane mol / h phase 14

28

H ₂ 175 99% 1% 0% 1% 100% 2.7E-04

CO 2,501 99% 1% 0% 1% 100% 8.2E-03 co ₂ 245 91% 9% 0% 9% 100% 6.3E-03

CH ₄ 447 96% 4% 0% 4% 100% 5.3E-03

N ₂ 2,500 99% 1% 0% 1% 100% 5.3E-03

MeOH 93 0% 100% 82% 18% 100% 2,6E-02

EtOH 57 0% 100% 67% 33% 100% 1,6E-02

1-PrOH 9 0% 100% 43% 57% 100% 2,6E-03

1-BuOH 114 0% 100% 18% 82% 100% 3.2E-02

H ₂ 0 1,737 1% 99% 99% 1% 100% 4.9E-01

Ethane 57 77% 23% 0% 23% 100% 3.8E-03

Propane 36 25% 75% 0% 75% 100% 7.7E-03 n-butane 19 0% 100% 0% 100% 100% 5.3E-03 n-pentane 1 0% 100% 0% 100% 100% 3.4E-04

Ethene 76 86% 14% 0% 14% 100% 3.0E-03

Propene 126 38% 62% 0% 62% 100% 2.2E-02

1-butene 45 0% 100% 0% 100% 100% l, 3E-02

1-penten 21 0% 100% 0% 100% 100% 6.0E-03 n-Dodecanese 3,528 0% 100% 0% 100% 100% l, 0E + 00 Example no.3c: Variation of the proportion of inert gas catalyst: as in Examples 3a

_ and 3b _

Composition synthesis gas absorbent

Molar flow molar fraction molar flow

[kmol / h] [%] [kmol / h]

H ₂ 5,000 35% -

CO 5,000 35%

N ₂ 4,280 30% n-dodecane 3,528

Table 3c

Sales CO: 50% _

Raw gas gas phase liquid water org. Total mol absorbed

10 12 phase phase / mol dodecane mol / h phase 14 28

H ₂ 175 100% 0% 0% 0% 100% 5.0E-02

CO 2,501 99% 1% 0% 1% 100% 7.1E-01

C0 ₂ 245 93% 7% 0% 7% 100% 6.9E-02

CH ₄ 447 97% 3% 0% 3% 100% 1,3E-01

N ₂ 4,280 99% 1% 0% 1% 100% l, 2E + 00

MeOH 93 1% 99% 82% 18% 100% 2,6E-02

EtOH 57 0% 100% 68% 32% 100% 1,6E-02

1-PrOH 9 0% 100% 43% 57% 100% 2,6E-03

1-BuOH 114 0% 100% 18% 82% 100% 3.2E-02

H ₂ 0 1,737 1% 99% 98% 1% 100% 4.9E-01

Ethane 57 82% 18% 0% 18% 100% 1,6E-02

Ethene 76 89% 11% 0% 11% 100% 2, lE-02

Propene 126 53% 47% 0% 46% 100% 3,6E-02

1-butene 45 0% 100% 0% 100% 100% l, 3E-02

1-penten 21 0% 100% 0% 100% 100% 6.0E-03 n-Dodecan 3,528 0% 100% 0% 100% 100% l, 0E + 00

Example 4

In the following exemplary embodiment, the amount of substance of the absorbent used (here dodecane) was varied. A product gas mixture was subjected to the separation step which was obtained in the catalytic conversion of a synthesis gas mixture with the composition given in Example 1 according to Table 1. 25%, 50%, 100% and 150% of the absorbent were used in four different simulations. The results are given in the tables below for Examples 4a to 4d.

Example No. 4a: Variation of the amount of absorbent catalyst: as in Example 3

Composition synthesis gas absorbent

Molar flow molar fraction molar flow

[kmol / h] [%] [kmol / h]

H ₂ 5,000 35% -

CO 5,000 35%

N ₂ 4,280 30% n-Dodecane 886 (25%)

Table 4a

Sales CO: 50%

Raw gas gas phase liquid phase aqueous org. Total mol 10 12 phase 28 phase absorbed / 14 mol mol / h dodecane

H ₂ 175 100% 0% 0% 0% 100% 2.5E-04 co 2.501 100% 0% 0% 0% 100% 7.5E-03 co ₂ 245 98% 2% 0% 2% 100% 5, LE-03

CH ₄ 447 99% 1% 0% 1% 100% 4,4E-03

N ₂ 4,280 100% 0% 0% 0% 100% 7.4E-03

MeOH 93 14% 86% 79% 7% 100% 8.9E-02

EtOH 57 11% 89% 74% 15% 100% 5.7E-02 1-PrOH 9 1% 99% 64% 36% 100% 1.0E-02

1-BuOH 114 0% 100% 40% 60% 100% 1,3E-01

H ₂ 0 1,737 2% 98% 98% 0% 100% l, 9E + 00

Ethane 57 96% 4% 0% 4% 100% 2.9E-03

Propane 36 88% 12% 0% 12% 100% 5.0E-03 n-butane 19 63% 37% 0% 37% 100% 7.9E-03 n-pentane 1 3% 97% 0% 97% 100% l, 3E-03

Ethene 76 97% 3% 0% 3% 100% 2,4E-03

Propene 126 90% 10% 0% 10% 100% l, 4E-02

1-butene 45 68% 32% 0% 32% 100% l, 6E-02

1-penten 21 9% 91% 0% 91% 100% 2,2E-02 n-Dodecanese 886 0% 100% 0% 100% 100% 1.0E + 00

Example 4b: Variation of the amount of absorbent catalyst: _ as in example 4a _

Composition synthesis gas absorbent

Molar flow molar fraction molar flow

[kmol / h] [%] [kmol / h]

H ₂ 5,000 35%

CO 5,000 35%

N ₂ 4,280 30% n-Dodecanese 1,767 (50%)

Table 4b

Sales CO: 50%

Raw gas gas phase liquid phase aqueous org. Total mol 10 12 phase 28 phase absorbed / mol / h 14 mol dodecane

H ₂ 175 100% 0% 0% 0% 100% 2,3E-04

CO 2,501 100% 0% 0% 0% 100% 6.8E-03

C0 ₂ 245 97% 3% 0% 3% 100% 4.8E-03

CH ₄ 447 98% 2% 0% 2% 100% 4, IE-03

N ₂ 4,280 100% 0% 0% 0% 100% 7, lE-03

MeOH 93 7% 93% 82% 11% 100% 4.9E-02

EtOH 57 1% 99% 76% 23% 100% 3.2E-02

1-PrOH 9 0% 100% 54% 46% 100% 5.3E-03

1-BuOH 114 0% 100% 28% 72% 100% 6,5E-02

H _z O 1,737 1% 99% 98% 0% 100% 9.7E-01 ethane 57 91% 9% ^~ Ö% 9% 100% 2.8E-03

Propane 36 74% 26% 0% 26% 100% 5.3E-03 n-butane 19 11% 89% 0% 89% 100% 9.5E-03 n-pentane 1 0% 100% 0% 100% 100% 6.8E-04

Ethene 76 95% 5% 0% 5% 100% 2,3E-03

Propene 126 79% 21% 0% 21% 100% l, 5E-02

1-Butene 45 22% 78% 0% 78% 100% 2.0E-02

1-penten 21 0% 100% 0% 100% 100% l, 2E-02 n- Dodecanese 1.767 0% 100% 0% 100% 100% l, 0E + 00

Example No. 4c: Variation of the amount of absorbent catalyst: as in Examples 4 a

_ and 4b _

Composition synthesis gas absorbent

Molar flow molar fraction molar flow

[kmol / h] [%] [kmol / h]

H ₂ 5,000 35%

CO 5,000 35%

N ₂ 4,280 30% n-Dodecanese 3,528 (100%)

Table 4c

Sales CO: 50%

Raw gas gas phase liquid phase aqueous org. Total mol 12 12 phase 28 phase absorbed /

14 mol mol / h

Dodecanese

H ₂ 175 100% 0% 0% 0% 100% 5.0E-02

CO 2,501 99% 1% 0% 1% 100% 7.1E-01

C0 ₂ 245 93% 7% 0% 7% 100% 6.9E-02

CH ₄ 447 97% 3% 0% 3% 100% 1,3E-01

N ₂ 4,280 99% 1% 0% 1% 100% l, 2E + 00

MeOH 93 1% 99% 82% 18% 100% 2,6E-02

EtOH 57 0% 100% 68% 32% 100% 1,6E-02

1-PrOH 9 0% 100% 43% 57% 100% 2,6E-03

1-BuOH 114 0% 100% 18% 82% 100% 3.2E-02

H20 1,737 1% 99% 98% 1% 100% 4.9E-01

Ethane 57 82% 18% 0% 18% 100% 1,6E-02

Ethene 76 89% 11% 0% 11% 100% 2, lE-02

Propene 126 53% 47% 0% 46% 100% 3,6E-02

1-butene 45 0% 100% 0% 100% 100% l, 3E-02 1-penten 21 0% 100% 0% 100% 100% 6.0E-03 n-Dodecanese 3,528 0% 100% 0% 100% 100% l, 0E + 00

Example 4d: Variation of the amount of absorbent catalyst: _ as in Examples 4a to 4c _

Composition synthesis gas absorbent

Molar flow molar fraction molar flow

[kmol / h] [%] [kmol / h]

H ₂ 5,000 35%

CO 5,000 35%

N ₂ 4,280 30% n-Dodecane 5,289 (150%)

Table 4d

Sales CO: 50%

Raw gas gas phase liquid phase aqueous org. Total mol 10 12 phase 28 phase absorbed

14 / mol mol / h dodecane

H ₂ 175 99% 1% 0% 1% 100% 2.0E-04

CO 2,501 99% 1% 0% 1% 100% 6.0E-03

C0 ₂ 245 90% 10% 0% 10% 100% 4.7E-03

CH ₄ 447 95% 5% 0% 5% 100% 3.9E-03

N ₂ 4,280 99% 1% 0% 1% 100% 7, lE-03

MeOH 93 0% 100% 77% 23% 100% 1,7E-02

EtOH 57 0% 100% 60% 40% 100% l, lE-02

1-PrOH 9 0% 100% 35% 65% 100% l, 8E-03

1-BuOH 114 0% 100% 13% 87% 100% 2,2E-02

H ₂ 0 1,737 1% 99% 98% 1% 100% 3,3E-01

Ethane 57 73% 27% 0% 27% 100% 2.9E-03

Propane 36 15% 85% 0% 85% 100% 5.8E-03 n-butane 19 0% 100% 0% 100% 100% 3.5E-03 n-pentane 1 0% 100% 0% 100% 100% 2,3E-04

Ethene 76 84% 16% 0% 16% 100% 2,3E-03

Propene 126 28% 72% 0% 72% 100% l, 7E-02

1-butene 45 0% 100% 0% 100% 100% 8,5E-03 l-penten 21 0% 100% 0% 100% 100% 4.0E-03 n-Dodecanese 5,289 0% 100% 0% 100% 100% l, 0E + 00

The amount of absorbent used (dodecane was used in the examples) was varied in the above examples 4a to 4d at 886 kmol / h, 1767 kmol / h, 3528 kmol / h and 5289 kmol / h, respectively, it being possible to show that the amount of alkenes and alkanes absorbed in the absorbent increases approximately linearly with increasing molar current, the higher alkenes and alkanes (for example propene, propane) being absorbed to a greater extent than the lower alkenes and alkanes (ethene, ethane), as expected.

During the absorption process, the alcohols methanol, ethanol, propanol and butanol go partly into the aqueous and partly into the dodecane phase, with methanol and ethanol, as expected, mainly going into the aqueous phase, while butanol already mainly goes into the organic phase, even with a low molar flow . The gases H ₂ , CO, C0 ₂ , CH ₄ and N ₂ remain in the gas phase during this separation step. With a low molar flow of the absorbent, however, the lower alkenes and alkanes and in some cases also proportions of the higher alkenes (propene, 1-butene) and alkanes (propane, butane) go into the gas phase. However, this changes as the molar current of the absorbent increases. For example, at a molar flow of 3528 kmol / h, about half of propene and 100% of 1-butene goes into the liquid organic phase. At an even higher molar flow of 5289 kmol / h, the proportion of propene absorbed in the organic phase also increases further. However, with a higher molar flow of the absorbent, higher proportions of methanol and ethanol and small proportions of C0 ₂ and CH _{4 also go} into the organic phase.

Example 5

In the following exemplary embodiment, the catalyst was varied. A product gas mixture was subjected to the separation step which was obtained in the catalytic conversion of a synthesis gas mixture with the composition given in Example 1 according to Table 1b. For the simulation, the selectivity to CO _{2 was} determined on the basis of the difference between 100% by weight and the sum of all products. For the simulation of the separation process, the Cn ₊ alkanes and the Cn ₊ alkenes were assumed to be undecane and undecene, respectively. Example No. 5: Variation of the catalyst

Catalyst: Ru ₃ (C0) ₁₂ / Ce0 ₂ (US 4,510,267 A)

Composition synthesis gas absorbent

Molar flow molar fraction molar flow

[kmol / h] [%] [kmol / h]

H ₂ 5,000 35% -

CO 5,000 35%

N ₂ 4,280 30% n-dodecane 3,528

Table 5

Sales CO: 75%

Raw gas gas phase liquid phase aqueous org. Total mol

10 phase 28 phase absorbed

12 14 / mol mol / h dodecane

H ₂ <1 100% 0% 0% 0% 100% 2,3E-02 co 1,284 99% 1% 0% 1% 100% 7,9E + 02 co ₂ 141 92% 8% 0% 8% 100% 8 , 7E + 01

CH ₄ 444 97% 3% 0% 3% 100% 2.7E + 02

N ₂ 4,280 99% 1% 0% 1% 100% 2.6E + 03

MeOH 0 0% 0% 0% 0% 0% 0.0E + 00

EtOH 30 0% 100% 75% 25% 100% 1.9E + 01

H ₂ 0 3,404 0% 100% 99% 0% 100% 2, lE + 03

Ethane 17 80% 20% 0% 19% 100% 1.1E + 01

Propane 18 34% 66% 0% 66% 100% 1.1E + 01 n-butane 15 0% 100% 0% 100% 100% 9.2E + 00 n-pentane 9 0% 100% 0% 100% 100% 5.4E + 00 n-hexane 0 0% 0% 0% 0% 0% 0.0E + 00 n-heptane 5 0% 100% 0% 100% 100% 2.8E + 00 n-octane 3 0% 100 % 0% 100% 100% l, 9E + 00 n-nonane 1 0% 100% 0% 100% 100% 8,3E-01 n-decane 2 0% 100% 0% 100% 100% l, 0E + 00 n-undecane 9 0% 100% 0% 100% 100% 5.5E + 00

Ethene 159 88% 12% 0% 12% 100% 9.8E + 01

Propene 209 46% 54% 0% 54% 100% l, 3E + 02

1-butene 123 0% 100% 0% 100% 100% 7.6E + 01

1-penten 64 0% 100% 0% 100% 100% 4.0E + 01

1-Hexen 46 0% 100% 0% 100% 100% 2.8E + 01

1-heptene 24 0% 100% 0% 100% 100% 1,5E + 01

1-octene 12 0% 100% 0% 100% 100% 7.6E + 00

1-non 8 0% 100% 0% 100% 100% 4,8E + 00

1-Decen 5 0% 100% 0% 100% 100% 3,3E + 00

1-Undecene 24 0% 100% 0% 100% 100% 1.5E + 01 n-Dodecane 3,528 0% 100% 0% 100% 100% 2.2E + 03

The results of this exemplary embodiment show that an olefin-rich product gas mixture which contains a small proportion of alcohols can also be subjected to the separation step. With the exception of the short-chain alkanes and alkenes (ethane, ethene, propane, propene), the alkanes and alkenes are almost completely absorbed in the liquid phase and are almost completely in the organic liquid phase after the phase separation.

List of reference symbols

10 Feeding in of the raw product gas stream

11 absorption device

12 line for discharging separated gaseous components

13 decanters

14 Line for organic phase to desorption device

15 Desorption device

16 Line for return of the absorption medium

17 first distillation column

18 Line for feeding the organic phase to the distillation column

19 Line for the alcohols separated off during the distillation for drying

20 Line for hydrocarbons to the second distillation

21 second distillation column

22 Line for discharging the hydrocarbons

23 Return line for returning the alcohols

24 third distillation column

25 molecular sieve

26 Line for drained water

27 Product line for discharged alcohols

28 Line for aqueous phase

29 Line for alcohols

30 pipe for sewage

Claims

1. A method for processing a gaseous mixture of substances obtained by catalytic conversion of synthesis gas, this mixture of substances containing at least alkenes, optionally alcohols and optionally alkanes, and optionally nitrogen as an inert gas and unreacted components of the synthesis gas, comprising hydrogen, carbon monoxide and / or carbon dioxide, with at least one step being provided after the catalytic conversion of the synthesis gas in which the product mixture obtained in this reaction is separated into a gas phase (12) and a liquid phase, characterized in that the preparation of the gaseous mixture of substances takes place at least as follows Steps includes:

Separation of the product mixture into a gas phase (12) and a liquid phase by at least partial absorption (11) of the alkenes, optionally the alcohols and optionally the alkanes in a high-boiling hydrocarbon or hydrocarbon mixture as the absorption medium;

Separation of the gases not absorbed in the absorption medium as a gas phase (12); Separating an aqueous phase (28) from the organic phase (14) of the absorption medium, preferably by decanting (13);

Desorption (15) of the alkenes, optionally alcohols and optionally alkanes, from the absorption medium.

2. The method according to claim 1, characterized in that the mixture obtained after the desorption (15) comprising alkenes, optionally alkanes and optionally alcohols then by a first distillation (17) into one predominantly containing the hydrocarbons (20) and one predominantly containing the alcohols (19) containing fraction is separated.

3. The method according to claim 2, characterized in that the first distillation (17) takes place at an elevated pressure, preferably in a pressure range from 10 bar to 40 bar.

4. The method according to claim 2 or 3, characterized in that the hydrocarbons (20) separated off in the first distillation (17) are then separated in an extractive distillation (21) with water from residues of alcohol and water contained in the hydrocarbons.

5. The method according to any one of claims 1 to 4, characterized in that alcohols which are contained in the aqueous phase (28) after the separation of the aqueous phase from the organic phase, preferably after decanting (13), through a third Distillation (24), in particular by azeotropic distillation, are separated from the water.

6. The method according to claim 5, characterized in that in the third distillation (24) separated from the water alcohols (29) fed to the mixture obtained after the desorption (15) and with this mixture through the first distillation (17) of the hydrocarbons be separated.

7. The method according to any one of claims 2 to 6, characterized in that the alcohol fraction (19) obtained in the first distillation (17) is then preferably dehydrated by means of a molecular sieve (25).

8. The method according to any one of claims 2 to 7, characterized in that an alcohol mixture (27) obtained after the first distillation (17) is then separated by one or more distillation steps into alcohol fractions each having a different number of carbon atoms, in particular into one C1 fraction, a C2 fraction, a C3 fraction and a C4 fraction.

9. The method according to any one of claims 2 to 8, characterized in that alkenes contained in the hydrocarbon mixture (18) obtained after the desorption (15) or in the hydrocarbon mixture (20) obtained after the first distillation (17) or in the alkenes contained in the hydrocarbon mixture (22) obtained after the second distillation (21), optionally after a further work-up, are converted to alcohols by hydration.

10. The method according to any one of claims 4 to 8, characterized in that the hydrocarbon mixture (22) obtained after the second distillation (21) is separated into fractions each having the same number of carbon atoms, in particular into a C3 fraction, a C4 Fraction and a C5 fraction.

11. The method according to any one of claims 2 to 10, characterized in that the lower alcohols methanol and ethanol and small amounts of water are separated from the alcohol fraction (19) obtained in the first distillation (17) in a column and the remaining alcohol mixture with a higher hydrocarbons are added and separated into an organic phase and an aqueous phase in a decanter.

12. The method according to claim 11, characterized in that the alcohols are stripped out of the organic phase in a further column and residual water contained in the alcohols is then removed by means of a molecular sieve.

13. The method according to any one of claims 2 to 10, characterized in that from the alcohol fraction obtained in the first distillation (17) in an extractive distillation with a hydrophilic substance, in particular with ethylene glycol, the lower alcohols methanol and ethanol are separated from the higher alcohols, the higher alcohols are then separated from the hydrophilic substance in a further distillation column and water contained in the higher alcohols is then optionally removed as an azeotrope.

14. The method according to any one of claims 2 to 10, characterized in that the water is selectively removed from the alcohol fraction obtained in the first distillation (17) by pervaporation through a membrane and is withdrawn in vapor form as permeate.

15. The method according to any one of claims 2 to 10, characterized in that the water is removed from the alcohol fraction obtained in the first distillation (17) by azeotropic distillation with a selective additive, in particular with a higher hydrocarbon, preferably with butane or pentane.

16. The method according to any one of claims 1 to 8 or according to any one of claims 10 to 15, characterized in that from the mixture of substances obtained after the catalytic conversion of synthesis gas at least the C4-alkenes and C5-alkenes and optionally C3-alkenes and optionally the Alcohols methanol, ethanol, propanol and butanol can be obtained.

17. The method according to any one of claims 1 to 16, characterized in that the high-boiling hydrocarbon or the hydrocarbon mixture used as the absorption medium is a diesel oil or an alkane, in particular dodecane with a viscosity of less than 10 mPas at room temperature and / or a boiling point of more than 200 ° C.

18. The method according to any one of claims 1 to 17, characterized in that the desorption (15) of the alkenes, alcohols and optionally alkanes from the absorption medium takes place in a distillation column, preferably at a pressure of 1 bar to 5 bar.

19. The method according to any one of claims 1 to 18, characterized in that after the desorption (15), the absorption medium (16) is returned to the separation step of absorption (11).

20. The method according to any one of claims 1 to 19, characterized in that the separated gas phase (12) of the gases not absorbed in the absorption medium comprises at least the gases nitrogen, hydrogen, carbon monoxide and / or carbon dioxide.

21. The method according to any one of the preceding claims, wherein the gaseous substance mixture (12) contains nitrogen from blast furnace gas, which is at least partially removed from the stream by means of a gas permeation membrane.