DE102019213497A1 - Process for the production of aldehydes and / or alcohols - Google Patents

Abstract

The present invention relates to a process for the preparation of aldehydes and / or alcohols by catalytic conversion (12) of synthesis gas (11) to a first mixture containing alkenes and alkanes, alkenes contained in this mixture in at least one subsequent step by hydroformylation (21) are converted to the corresponding alcohols, wherein according to the invention the first mixture obtained after the catalytic conversion (12) contains, in addition to alkenes and alkanes, at least one alcohol with two to four carbon atoms, which is then separated off (24) and / or purified (19) is obtained as an isolated product. In contrast to the prior art, according to the invention, not only alkenes but also alcohols with two to four carbon atoms are produced as early as the catalytic conversion of synthesis gas, that is to say in this first step. This increases the overall yield of these alcohols in the process comprising at least two synthesis steps. The alcohols which are formed by reaction of the synthesis gas in the first step can, depending on the process variant, be separated from the alkenes, for example, before the hydroformylation (21).

Description

The present invention relates to a process for the preparation of aldehydes and / or alcohols by catalytic conversion of synthesis gas to a first mixture containing alkenes and alcohols, alkenes contained in this mixture being converted to the corresponding aldehydes or alcohols in at least one subsequent step by hydroformylation.

State of the art

The hydroformylation of alkenes to the corresponding aldehydes and / or alcohols is a known reaction for the preparation of aldehydes and alcohols and is used industrially, for example for the production of propanal and propanol from ethene and for the production of butyraldehyde and 1-butanol from propene.

The selective hydroformylation of aliphatic alkenes to linear aldehydes is one of the most important homogeneous catalytic reactions in industry. More than 8 million tons of various aldehydes and alcohols are produced in this way every year. The hydroformylation of propene, for example, is important for the production of 1-butanal, which serves as the starting material for 2-ethylhexanol, currently the most important plasticizer alcohol.

The hydroformylation can be carried out both in the gas phase over heterogeneous catalysts and in the liquid phase, preferably with homogeneous catalysts. There are different processes for hydroformylation, which differ, among other things, in the choice of catalyst recycling.

From the EP 3 130 399 A1 a process for the hydroformylation of alkenes and / or alkynes in the gas phase is known, in which a mixture of hydrogen and carbon monoxide in the presence of heterogeneous catalysts at temperatures of preferably 170 ° C to 230 ° C and a pressure of 1.5 to 50 bar , preferably from 20 bar to 50 bar is implemented and catalysts made of rhodium or cobalt phosphide are used.

In the DE 42 42 725 A1 describes a process for the preparation of higher, predominantly unbranched primary alcohols by hydroformylation of alkenes from the Fischer-Tropsch synthesis in the presence of water-soluble rhodium complex compounds as catalysts. In this known process, alkenes with 6 to 20 carbon atoms are first obtained by Fischer-Tropsch synthesis, which are then reacted in the presence of water-soluble salts, the anion of which is an aromatic phosphine. In the first step of the Fischer-Tropsch synthesis, a complex mixture is obtained including alkanes, alkenes of different molecular sizes, alcohols, aldehydes, ketones and carboxylic acids. This mixture can contain a comparatively high proportion of alkene of up to 70%. However, they are higher unbranched alkenes which, after the synthesis, first have to be separated from the reaction mixture by distillation. This is followed by the catalytic conversion of, for example, a nonene mixture in an aqueous solution with a synthesis gas containing CO and H ₂ in a ratio of 1: 1. The crude product is then hydrogenated in a further step with hydrogen in the presence of a nickel catalyst, the crude alcohol obtained is purified in a column and then esterified.

In the US 6,756,411 B2 a process is also described in which an alkene obtained by Fischer-Tropsch synthesis is used as a feedstock for a subsequent hydroformylation in which the alkene is reacted with carbon monoxide and hydrogen in the presence of a hydroformylation catalyst to form aldehydes and alcohols. Here, too, an oily fraction is separated from the complex product mixture obtained in the Fischer-Tropsch synthesis with the iron or cobalt catalysts typical of this process, which contains higher alkenes with 5 to 18 carbon atoms, in particular with 9 or 10 carbon atoms. Contains atoms and this fraction is used as a feedstock for hydroformylation.

The US 6,861,450 B2 describes a similar process in which a Fischer-Tropsch synthesis is first carried out using a cobalt-based catalyst, after this synthesis alkenes containing six or more carbon atoms are separated off from the product mixture and these alkenes then with a hydroformylation catalyst comprising a source of Cobalt and an alkylphosphine can be hydroformylated to alcohols.

In the US 6,982,355 B2 describes an integrated Fischer-Tropsch process for the production of linear and branched alcohols and alkenes, in which alcohols from the product mixture of the Fischer-Tropsch synthesis are completely or partially dehydrated and alkanes are dehydrated, so that a mixture of alkenes and alkanes is produced is followed by a hydroformylation of the alkenes is carried out to obtain alcohols. As a result of the partial dehydrogenation of the alkanes, a higher proportion of linear alpha-alkenes is obtained than is otherwise usual in the Fischer-Tropsch synthesis. In this known process, the liquid light fraction of the Fischer-Tropsch synthesis is first dehydrated and then separated into two fractions, one fraction of which contains alkenes and alkanes with C ₅ to C ₉ and the other fraction contains alkenes and alkanes with C ₁₀ to C ₁₃ . These two fractions are then converted into aldehydes using synthesis gas.

The US 9,073,804 B2 describes a process in which hydrogen and carbon monoxide are initially converted in a Fischer-Tropsch reaction, a fraction of the product mixture containing methane, short-chain and longer-chain alkanes and short-chain alkenes such as ethene and propene, among others. When using an iron-based catalyst, a proportion of 1 to 6% by volume of ethene and 4 to 15% by volume of propene is obtained. In the case of the selectivities given here, however, the by-product CO _{2 is} not taken into account, so that the actual selectivities are lower. This is followed by a hydroformylation in the presence of a catalyst, alcohols being obtained either indirectly via the aldehydes and their hydrogenation with hydrogen or directly, in particular propanol, which is obtained as an intermediate product from ethene via propanal. In this known process, the catalyst of the Fischer-Tropsch reaction mainly contains iron oxide and additionally titanium oxide, potassium carbonate and water. In the first reaction step mainly alkanes and alkenes are obtained, namely a high proportion of 24.2% methane, 12.3% propene, 6.1% ethane, 5.8% butene, 5.0% ethene, 2.6% Propane and, in smaller quantities, butane and pentane. Here, too, the CO ₂ is not taken into account as a by-product. Significant amounts of alcohols with two or more carbon atoms are therefore not formed in this Fischer-Tropsch synthesis. In the subsequent hydroformylation, only the alkenes contained in the product mixture after the Fischer-Tropsch synthesis can thus be converted into alcohols. In addition, in this process, after the Fischer-Tropsch synthesis, there is first a separation step in which propene is separated off and only the ethene is then hydroformylated, whereby propanol is formed. This propanol is then partially separated off and partially dehydrated to propene. This known process thus requires several conversion steps and, in addition to the alkenes, only leads to one defined alcohol, namely propanol. This only occurs in a comparatively low yield, since only 5% ethene is formed in the Fischer-Tropsch synthesis. The synthesis of propene is therefore in the foreground in this process.

The object of the present invention is to provide an improved process for the preparation of aldehydes and / or alcohols, in particular with two to five carbon atoms, by catalytic conversion of synthesis gas, in which the alcohols or aldehydes are formed in higher yield.

Another concern of the present invention is to provide a method in which the complex first product mixture from the catalytic conversion of the synthesis gas, consisting of alcohols, alkenes and alkanes, can be converted into secondary products in a targeted and more effective manner, in order to produce a high-quality product / high-quality products for the fuel market and / or the chemical industry. Another concern of the present invention is to provide a method of the aforementioned type in which the purification of the complex product mixture is facilitated.

The solution to the aforementioned object is provided by a method for producing alkenes of the type mentioned at the beginning with the features of claim 1.

According to the invention it is provided that the first mixture obtained after the catalytic conversion contains, besides alkenes and alkanes, at least one alcohol with two to four carbon atoms, which is then obtained as an isolated product by separation and / or purification.

In contrast to the prior art, according to the invention, not only alkenes but also alcohols with two to four carbon atoms are produced as early as the catalytic conversion of synthesis gas, that is to say in this first step. The subsequent conversion of the alkenes in the hydroformylation increases the overall yield of alcohols in the process comprising at least two synthesis steps, or the range of products is expanded to include aldehydes and the overall yield of alcohols and aldehydes is increased. Depending on the process variant, these alcohols can, for example, be separated off from the alkenes even before the hydroformylation.

The aldehydes initially formed in the hydroformylation can be hydrogenated to alcohols in a subsequent step. In the hydroformylation, aldehydes are initially formed. The alcohols can be formed either during the hydroformylation or afterwards.

In the context of the present invention, catalysts and process variants for the catalytic synthesis of higher alcohols from synthesis gases were developed. Here, for example, synthesis gas can be converted, which is provided by cleaning and conditioning steel mill gases. However, the invention described below can expressly also be applied to other synthesis gas sources.

According to the present invention, the synthesis of higher alcohols from synthesis gas initially comprises the provision of the synthesis gas, the catalytic synthesis of the higher alcohols from this synthesis gas (“higher alcohols” are understood here to mean alcohols with at least two carbon atoms) and the purification or separation of the Product mixture. The provision of the synthesis gas may also include the cleaning and conditioning of the synthesis gas in addition to the preparation of the synthesis gas. Both fossil fuels, such as natural gas, coal, but also _{gases rich in CO and CO 2,} for example from steel or cement works, and hydrogen can be used as feed for the provision of the synthesis gas. It is also possible to obtain the synthesis gas used from biomass. The hydrogen is preferably produced by means of renewable energies and / or with a low CO ₂ footprint, for example by means of water electrolysis or methane pyrolysis.

The catalytic synthesis of the higher alcohols from synthesis gas can be carried out according to the invention, 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. The product mixture obtained from unconverted synthesis gas, alcohols, alkenes and alkanes can be heated to lower temperatures of, for example, 150 ° C or less, in particular to below 130 ° C, preferably to below 110 ° C or to even lower temperatures of less than 80 ° C, for example about 40 ° C to 20 ° C, especially cooled to about 30 ° C and separated into a gas and a liquid phase. The gas phase mainly contains the unconverted synthesis gas as well as any inert components (e.g. nitrogen) and the methane formed as a by-product. The gas phase is usually returned to the synthesis of the higher alcohols. If necessary, a purification or conditioning of the gas phase, such as, for example, the conversion of the methane formed as a by-product into synthesis gas, is provided.

The liquid phase mainly contains the alcohols, alkenes and 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. through partial oxidation, steam reforming or autothermal reforming. If appropriate, the alkanes can also be dehydrogenated to the corresponding alkenes and then likewise hydroformylated in order to increase the yield of aldehydes and / or alcohols.

The alcohols remain in the liquid phase and are optionally marketed as a product mixture, for example as a fuel additive, after the water formed as a by-product has been separated off, or are separated into the individual alcohols in a distillation.

Depending on the respective composition and concentration of the products formed after the catalytic conversion of the synthesis gas, the aforementioned process parameters can be varied in a suitable manner or supplemented by further separation steps within the scope of the method according to the invention.

In addition to the downstream hydroformylation of the alkenes to give the alcohols, the value chain according to the invention also includes the direct integration of the consecutive hydroformylation of the alkenes into the process concept of the synthesis of the higher alcohols. There are several options for this and the method according to the invention thus provides several alternative variants.

The industrial processes for the hydroformylation of alkenes use a CO-rich synthesis gas from carbon monoxide and hydrogen with a CO: H ₂ ratio of 1: 1 or 1: 2. Processes for hydroformylation using synthesis gas containing _{CO 2} are also described in the scientific literature. The provision of a suitable synthesis gas must be taken into account in the process concepts for consecutive hydroformylation.

The consecutive hydroformylation of the alkenes formed as by-products in the synthesis of the higher alcohols to alcohols enables the targeted production of alcohols in a higher yield and the preparation of a uniform class of compounds from the complex product mixture of the catalytic synthesis of higher alcohols. The consecutive conversion of the alkenes achieves alcohol yields which cannot be achieved with the catalyst used in the synthesis of the higher alcohols from synthesis gas.

Compared to the hydration of the alkenes, the hydroformylation specifically produces aldehydes and alcohols which contain an additional carbon atom. A product mixture with a higher average chain length is formed. Starting from the synthesis gas provided, which is optionally conditioned accordingly, the value chain leads via the catalytic synthesis of higher alcohols, which leads to a product mixture of alcohols, alkenes and alkanes and the consecutive hydroformylation to alcohols and alkanes or to alcohols, aldehydes and alkanes.

This value chain provides various fundamental advantages over the current state of the art in the synthesis of higher alcohols from synthesis gas and the previous approaches to the extraction of chemical valuable substances from steel mill gas. The two-step synthesis of alcohols proposed here can lead to higher alcohol yields than the known catalytic processes for the synthesis of higher alcohols.

From the complex product mixture after the synthesis gas has been converted in the first step, a more uniform product is generated, which leads to advantages in the purification process and in marketing logistics.

The conversion of the alkenes to aldehydes and / or alcohols also has the advantage that the separation of the alkanes and alkenes, which may be demanding due to the similar physical properties, is dispensed with and the alkanes can be separated more easily from the product mixture.

According to a first preferred variant of the process, 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 then the separated alkenes are hydroformylated, optionally mixed with the alkanes.

In this variant, a mixture of separated alkenes, optionally mixed with the alkanes, can first be separated into two or more fractions with different numbers of carbon atoms and only then the individual fractions are hydroformylated separately from one another in order to convert the alkenes into the respective fractions to obtain the corresponding alcohols.

Furthermore, the mixture of alkenes can preferably be separated into at least a C2 fraction, a C3 fraction and a C4 fraction and then hydroformylated and from these fractions, if appropriate after separation of the respective alkanes, propanol, butanol and pentanol or propanal, butanal and Pentanal can be obtained.

The separation of the hydrocarbons into the individual Cx cuts or alkenes can be advantageous since it enables the individual alkenes to be hydroformylated separately. Alkenes, the respective hydroformylation products of which are particularly suitable for the fuel or chemical market, can be converted to the corresponding aldehydes or 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 hydroformylation of the individual Cx cuts or alkenes can be selected independently of one another. The influence of the alkanes on the hydroformylation of the alkenes must be taken into account.

The disadvantage is that a separate system is required for the hydroformylation for each C-cut or that the individual fractions have to be hydroformylated batchwise. Each of the hydroformylation plants must be supplied with synthesis gas. The synthesis gas can either over a partial stream from the catalytic synthesis of higher alcohols or optionally via the partial oxidation of the alkanes formed as by-products can be provided.

In this possible variant, the consecutive hydroformylation of the alkenes to alcohols is preferably carried out after the alcohols have been separated off, and the respective pure alcohols can be obtained from the separated alcohols by purification or separation of the alcohol mixture. The separation of the alkene mixture into the individual alkenes can also be advantageous since it enables the individual alkenes to be hydroformylated separately. In this case, after this separate hydroformylation of the individual hydrocarbon fractions, a mixture of the alkane and the next higher aldehyde and / or alcohol would be obtained, since the chain length is lengthened by one carbon atom as a result of the hydroformylation. These would be, for example, propanol in a mixture with ethane, butanol in a mixture with propane or pentanol in a mixture with butane or the alkanes mentioned in a mixture with the next higher aldehyde and / or alcohol, for example propanal in a mixture with ethane, butanal in a mixture with Propane or pentanal mixed with butane.

There is also the option of hydroformylating the alkenes after the alkanes have been separated off from the respective Cx cuts. This provides the advantages of a comparatively pure starting material concentration and the possibility of carrying out the hydroformylation under respectively different, specifically adapted conditions for the respective alkene. However, due to the equipment and energy requirements involved in separating alkanes and alkenes, this option is only economically feasible under certain framework conditions.

The options for integrating the consecutive conversion of the alkenes to alcohols into the process concept for the catalytic synthesis of the higher alcohols, which are possible within the scope of the process according to the invention, may differ in the composition of the reaction mixture and the prevailing process conditions, such as temperature and pressure. By integrating the hydroformylation of the alkenes into the process concept for the catalytic synthesis of the higher alcohols, it is possible to use the temperature and pressure levels already present in the catalytic synthesis of higher alcohols for the hydroformylation.

According to a second preferred variant of the process according to the invention, after the alcohols have been separated off, a mixture comprising the alkenes and alkanes comprising predominantly C2-C4 alkenes is then hydroformylated as a mixture to give the corresponding aldehydes and / or alcohols.

The separation of the alcohols from the alkenes and alkanes after the catalytic synthesis of higher alcohols offers the possibility of carrying out the subsequent hydroformylation of the alkenes with a relatively pure mixture of alkenes and alkanes. It must be taken into account that the industrial processes for the implementation of the individual alkenes are optimized and differ from one another in the choice of the catalyst and the reaction conditions. For the conversion of the alkene mixture, it is therefore advisable to conduct the process in such a way that either the conversion of all alkenes is possible or the conversion of individual preferred alkenes to the respective aldehydes and / or alcohols is promoted. Compared to the first variant of the process described above, the hydroformylation of the alkene mixture has the advantage that only one plant is required for the hydroformylation or that batch hydroformylation can be dispensed with.

In this variant of the process, the alkanes are preferably separated off from the mixture after the hydroformylation and the aldehydes and / or alcohols formed from the alkenes are optionally combined with the alcohols separated off after the first step of the catalytic conversion of synthesis gas and optionally converted into individual aldehydes and / or or alcohols with different numbers of carbon atoms separated. In contrast to the first variant mentioned above, there is no separation of the alkenes into the individual compounds with different numbers of carbon atoms before the hydroformylation.

According to a possible development of the process according to the invention, the alkanes are separated from the alcohols and separated alkanes are converted at least partially into a CO-rich synthesis gas by partial oxidation with oxygen (POX), steam reforming or autothermal reforming, which synthesis gas is then used for the hydroformylation of the alkenes.

If the catalytic synthesis of higher alcohols is also carried out with a CO-rich synthesis gas composed of carbon monoxide and hydrogen (for example CO: H ₂ in a ratio of 1: 1), a substream of the synthesis gas provided can preferably be used for the hydroformylation.

In the event that the catalytic synthesis of higher alcohols is carried out with a CO ₂ -rich or CO and CO ₂ -containing synthesis gas, which can be obtained, for example, from blast furnace gas, the subsequent hydroformylation could be carried out with the same CO-containing synthesis gas or get your own synthesis gas production. The alkanes formed as a by-product in the catalytic synthesis of higher alcohols can, for example, be converted into a CO-rich synthesis gas by partial oxidation. The hydrogen content can be adjusted by removing hydrogen, for example by means of PSA (pressure swing adsorption) or by adding hydrogen. The synthesis gas produced in this way can then be used in the hydroformylation. With this process concept, the alkanes formed as by-products are also used in the process.

The cooling (to approx. 30 ° C.) and relaxation (to approx. 1 bar) for the separation of the hydrocarbons from the alcohols could prove to be energetically disadvantageous in this process variant. In many cases, the hydroformylation requires elevated pressures of more than 5 bar, for example 40 bar to 60 bar, in particular about 50 bar, and elevated temperatures of more than 80 ° C., for example approx. 150-250 ° C., so that the isolated alkane / Alkene mixture must be recompressed and heated.

In all process variants according to the invention, the hydroformylation is preferably carried out at elevated temperature, in particular at temperatures of more than 80 ° C., preferably at temperatures of more than 100 ° C., more preferably at temperatures of more than 120 ° C., for example at temperatures in the range of 160 ° C to 200 ° C, in particular at 170 ° C to 190 ° C and / or is at atmospheric or elevated pressure, in particular at a pressure of more than 5 bar, preferably at a pressure of more than 10 bar, more preferably at a Pressure of more than 15 bar, for example at a pressure of 20 bar to 60 bar, preferably carried out at a pressure of 30 bar to 60 bar.

A third alternative preferred variant of the process according to the invention provides that the hydroformylation of the alkenes is carried out with the first mixture of alkanes, alkenes and alcohols obtained in the catalytic conversion of the synthesis gas without the alcohols having been separated off from this mixture beforehand.

In this process variant, the alkanes are preferably separated from the aldehydes and / or alcohols after the hydroformylation and the remaining mixture of alcohols and / or aldehydes is optionally purified and / or into individual aldehydes and / or alcohols, in particular into propanal, butanal and pentanal and / or methanol, ethanol, propanol and butanol separated.

In this and, if appropriate, also in other process variants, the alkanes are preferably separated off from the alcohols at a lower temperature and lower pressure than the preceding hydroformylation, preferably at a temperature in the range from 20 ° C. to 40 ° C. and a pressure of less than 5 bar, particularly preferably at a pressure of less than 2 bar.

In the process according to the invention, before the hydroformylation of the alkenes to the corresponding aldehydes and / or alcohols and after the catalytic conversion 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 and a liquid phase, the liquid phase being used for the subsequent hydroformylation of the alkenes to the aldehydes and / or alcohols and the separation preferably taking place at a lower temperature and / or at approximately the same pressure as the previous catalytic conversion of the synthesis gas.

The hydroformylation of the alkenes after such a gas-liquid separation and conversion of the reaction mixture of alkenes, alkanes and alcohols formed in the catalytic synthesis of the higher alcohols can, in some optional process variants, offer the advantage that the reaction mixture is already at a high pressure of, for example, 60 bar is present and only needs to be preheated to the reaction temperature.

In these variants of the process, the gas phase obtained in the separation is preferably at least partially returned to the step of catalytic conversion of the synthesis gas. If appropriate, this gas phase can also be fed to the hydroformylation.

According to a fourth possible variant of the process according to the invention, after the catalytic conversion of the synthesis gas and only after the subsequent hydroformylation of the alkenes to the corresponding aldehydes and / or alcohols, at least one step is provided in which the product mixture obtained in this reaction is separated into a Gas phase and a liquid phase takes place, the alkanes then being separated off from the liquid phase.

In this process variant too, the gas phase obtained in the separation is preferably at least partially returned to the step of catalytic conversion of the synthesis gas.

Both in the third and in this fourth possible variant of the process, the hydroformylation is thus carried out in the presence of the alcohols and the alkanes likewise formed. Examples of gas-phase hydroformylation are described in the patent literature, in which the reaction conditions for gas-phase hydroformylation, for example of ethene and propene, are similar to those for the catalytic synthesis of higher alcohols (see for example EP 000003130399 A1 ), so that it may be useful to carry out the hydroformylation of the alkenes directly in a reactor downstream of the catalytic synthesis of higher alcohols and without prior separation of the product mixture. It is advantageous here that the reaction mixture is already present at a similar temperature and pressure level in the catalytic synthesis of higher alcohols as is required for the conversion in the hydroformylation. The first reaction mixture of the catalytic synthesis of higher alcohols is passed, for example, through a second (hydroformylation) reactor in which the alkenes are converted to aldehydes and / or alcohols. The overall yield of oxygenates is thereby increased even before the product mixture is worked up. In certain optional process variants, for example, it can be advantageous if the reaction mixture does not have to be cooled to a lower temperature and a lower pressure (for example 30 ° C., 1 bar) and instead can be reacted further directly. In this way, the energy costs for compressing and heating the alkene / alkane mixture can be reduced compared to some of the process variants mentioned above. It should be avoided that other components of the product mixture (alcohols, alkanes, H ₂ O) influence the hydroformylation under the conditions.

The composition of the synthesis gas for the hydroformylation is predetermined or partially predetermined by the composition of the synthesis gas for the catalytic synthesis of higher alcohols or that of the residual gas contained in the catalytic synthesis of higher alcohols. In contrast to the process variants mentioned above, in particular in the fourth process variant, the composition of the synthesis gas cannot be freely selected. Another option here is, for example, adding synthesis gas to the gas mixture that is already present.

In the WO 2015/086151 A1 describes a process by means of which synthesis gas can be provided by cleaning and conditioning various gas flows that arise in a steelworks. For the first process stage described herein for the catalytic synthesis of alcohols having at least two carbon atoms from synthesis gas (also referred to herein as higher alcohols), synthesis gas from such sources is suitable, for example. In principle, however, any other suitable synthesis gas sources can also be used for the process according to the invention.

In the context of the present invention, an overall process was developed which enables alcohols and / or aldehydes (with two or more carbon atoms) to be produced with good yield starting from synthesis gas. In the present application, processes are described which, based on the product mixture obtained in the conversion of synthesis gas, comprising carbon monoxide and hydrogen or carbon dioxide and hydrogen or carbon monoxide and carbon dioxide and hydrogen, offer advantages in economic, technological and / or ecological terms compared to known processes , especially compared to a simple 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. Hence it is here in particular interesting to look at basic chemicals that can be used, for example, in the plastics or fuel sector.

According to the above description, the four method variants mentioned below are particularly preferred within the scope of the present invention.

• - Herstellung von höheren Alkoholen (mit wenigstens zwei C-Atomen) und Alkenen durch katalytische Umsetzung von Synthesegas;
• - Trennung des erhaltenen Produktgemisches in eine Gasphase und eine Flüssigphase;
• - gegebenenfalls Rückführung der abgetrennten Gasphase zur katalytischen Umsetzung des Synthesegases;
• - Abtrennung der Alkene und Alkane von den erhaltenen Alkoholen;
• - gegebenenfalls Auftrennung des von den Alkenen und Alkanen abgetrennten Alkoholgemisches in einzelne Verbindungen oder Verbindungsgruppen, insbesondere Ethanol, Propanole, Butanole und gegebenenfalls Methanol;
• - Auftrennung des Gemisches aus Alkenen und Alkanen in einzelne Fraktionen mit jeweils unterschiedlicher Anzahl von C-Atomen, insbesondere einen C2-Schnitt, einen C3-Schnitt und einen C4-Schnitt;
• - jeweils getrennte Hydroformylierung der zuvor erhaltenen einzelnen Gemische aus Alkenen und Alkanen mit jeweils gleicher Anzahl von C-Atomen, gegebenenfalls anschließende Abtrennung der Alkane jeweils von den erhaltenen Aldehyden und/oder Alkoholen der einzelnen Fraktionen;
• - gegebenenfalls Umsetzung der abgetrennten Alkane zur Erzeugung von CO-reichem Synthesegas für die Hydroformylierung und/oder die Synthese höherer Alkohole, beispielsweise mittels partieller Oxidation, Autothermal Reformer (ATR) oder Steamreforming;
• - gegebenenfalls Vereinigung der nach der Abtrennung der Alkane erhaltenen Alkohole mit den zuvor bei der katalytischen Umsetzung des Synthesegases bereits erhaltenen und abgetrennten Alkoholen.

In variant 1, the method preferably comprises the steps:

• - Production of higher alcohols (with at least two carbon atoms) and alkenes by catalytic conversion of synthesis gas;
• - Separation of the product mixture obtained into a gas phase and a liquid phase;
• - if necessary, recycling of the separated gas phase for the catalytic conversion of the synthesis gas;
• - Separation of the alkenes and alkanes from the alcohols obtained;
• if appropriate, separation 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 individual fractions each with a different number of carbon atoms, in particular a C2 cut, a C3 cut and a C4 cut;
• - In each case separate hydroformylation of the previously obtained individual mixtures of alkenes and alkanes each having the same number of carbon atoms, optionally subsequent separation of the alkanes in each case from the aldehydes and / or alcohols obtained of the individual fractions;
• - If necessary, conversion of the alkanes separated off to generate CO-rich synthesis gas for hydroformylation and / or the synthesis of higher alcohols, for example by means of partial oxidation, autothermal reformer (ATR) or steam reforming;
• optionally combining the alcohols obtained after the alkanes have been separated off with the alcohols already obtained and separated off beforehand in the catalytic conversion of the synthesis gas.

• - Herstellung von höheren Alkoholen (mit wenigstens zwei C-Atomen) und Alkenen durch katalytische Umsetzung von Synthesegas;
• - Trennung des erhaltenen Produktgemisches in eine Gasphase und eine Flüssigphase;
• - gegebenenfalls Rückführung der abgetrennten Gasphase zur katalytischen Umsetzung des Synthesegases;
• - Abtrennung der Alkene und Alkane von den erhaltenen Alkoholen;
• - Hydroformylierung des Gemisches der zuvor von den Alkoholen abgetrennten Alkene im Gemisch mit den Alkanen, wobei ein Gemisch aus Aldehyden und/oder Alkoholen und Alkanen erhalten wird;
• - Abtrennung der Alkane von den Aldehyden und/oder Alkoholen
• - gegebenenfalls Umsetzung der abgetrennten Alkane zur Erzeugung von CO-reichem Synthesegas für die Hydroformylierung, beispielsweise mittels partieller Oxidation, Autothermal Reformer (ATR) oder Steamreforming;
• - gegebenenfalls Vereinigung der nach der Abtrennung der Alkane erhaltenen Alkohole mit den zuvor bei der katalytischen Umsetzung des Synthesegases bereits erhaltenen und abgetrennten Alkoholen;
• - gegebenenfalls Aufreinigung und Auftrennung des erhaltenen Alkoholgemisches in einzelne Verbindungen oder Verbindungsgruppen, insbesondere Ethanol, Propanol, Butanol sowie Methanol und gegebenenfalls höhere Alkohole.

In variant 2, the method preferably comprises the steps:

• - Production of higher alcohols (with at least two carbon atoms) and alkenes by catalytic conversion of synthesis gas;
• - Separation of the product mixture obtained into a gas phase and a liquid phase;
• - if necessary, recycling of the separated gas phase for the catalytic conversion of the synthesis gas;
• - Separation of the alkenes and alkanes from the alcohols obtained;
• Hydroformylation of the mixture of the alkenes previously separated from the alcohols in a mixture with the alkanes, a mixture of aldehydes and / or alcohols and alkanes being obtained;
• - Separation of the alkanes from the aldehydes and / or alcohols
• - if necessary, conversion of the alkanes separated off to generate CO-rich synthesis gas for hydroformylation, for example by means of partial oxidation, autothermal reformer (ATR) or steam reforming;
• optionally combining the alcohols obtained after the alkanes have been separated off with the alcohols already obtained and separated off beforehand in the catalytic conversion of the synthesis gas;
• optionally purification and separation of the alcohol mixture obtained into individual compounds or groups of compounds, in particular ethanol, propanol, butanol and methanol and optionally higher alcohols.

• - Herstellung von höheren Alkoholen (mit wenigstens zwei C-Atomen) und Alkenen durch katalytische Umsetzung von Synthesegas;
• - Trennung des erhaltenen Produktgemisches in eine Gasphase und eine Flüssigphase;
• - gegebenenfalls Rückführung der abgetrennten Gasphase zur katalytischen Umsetzung des Synthesegases;
• - Hydroformylierung des zuvor erhaltenen Produktgemisches der Flüssigphase umfassend Alkohole, Alkene und Alkane, wobei die Alkene im Gemisch zu den entsprechenden Aldehyden und/oder Alkoholen mit einer um ein C-Atom längeren Kohlenstoffkette hydroformyliert werden;
• - Abtrennung der Alkane von den erhaltenen Aldehyden und/oder Alkoholen, vorzugsweise bei einem niedrigeren Druck verglichen mit der zuvor durchgeführten Hydroformylierung;
• - gegebenenfalls Aufreinigung und Auftrennung des erhaltenen Aldehydgemisches und/oder Alkoholgemisches in einzelne Verbindungen oder Verbindungsgruppen, insbesondere Ethanol, Propanol, Butanol sowie Methanol und gegebenenfalls höhere Alkohole bzw. Propanal, Butanal und Pentanal;
• - gegebenenfalls Umsetzung der abgetrennten Alkane zur Erzeugung von CO-reichem Synthesegas für die Hydroformylierung, beispielsweise mittels partieller Oxidation, Autothermal Reformer (ATR) oder Steamreforming.

In variant 3, the method preferably comprises the steps:

• - Production of higher alcohols (with at least two carbon atoms) and alkenes by catalytic conversion of synthesis gas;
• - Separation of the product mixture obtained into a gas phase and a liquid phase;
• - if necessary, recycling of the separated gas phase for the catalytic conversion of the synthesis gas;
• - Hydroformylation of the previously obtained product mixture of the liquid phase comprising alcohols, alkenes and alkanes, the alkenes being hydroformylated as a mixture to the corresponding aldehydes and / or alcohols with a carbon chain longer by one carbon atom;
• - Separation of the alkanes from the aldehydes and / or alcohols obtained, preferably at a lower pressure compared to the previously carried out hydroformylation;
• optionally purification and separation of the aldehyde mixture and / or alcohol mixture obtained into individual compounds or groups of compounds, in particular ethanol, propanol, butanol and methanol and optionally higher alcohols or propanal, butanal and pentanal;
• - If necessary, conversion of the alkanes separated off to generate CO-rich synthesis gas for the hydroformylation, for example by means of partial oxidation, autothermal reformer (ATR) or steam reforming.

In this third variant, the consecutive hydroformylation of the alkenes to alcohols takes place after the gas-liquid separation and thus after the separation of the unconverted synthesis gas, but in the presence of the alcohols already formed.

• - Herstellung von höheren Alkoholen (mit wenigstens zwei C-Atomen) und Alkenen durch katalytische Umsetzung von Synthesegas;
• - Hydroformylierung des erhaltenen Produktgemisches umfassend Alkohole, Alkene und Alkane, wobei die Alkene im Gemisch zu den entsprechenden Aldehyden und/oder Alkoholen mit einer um ein C-Atom längeren Kohlenstoffkette hydroformyliert werden;
• - Trennung des erhaltenen Produktgemisches in eine Gasphase und eine Flüssigphase;
• - gegebenenfalls Rückführung der abgetrennten Gasphase zur katalytischen Umsetzung des Synthesegases;
• - Abtrennung der Alkane aus dem Produktgemisch der flüssigen Phase;
• - gegebenenfalls Aufreinigung und Auftrennung des erhaltenen Alkoholgemisches in einzelne Verbindungen oder Verbindungsgruppen, insbesondere Ethanol, Propanol, Butanol sowie Methanol und gegebenenfalls höhere Alkohole;
• - gegebenenfalls Umsetzung der abgetrennten Alkane zur Erzeugung von CO-reichem Synthesegas für die Hydroformylierung, beispielsweise mittels partieller Oxidation, Autothermal Reformer (ATR) oder Steamreforming.

In variant 4, the method preferably comprises the steps:

• - Production of higher alcohols (with at least two carbon atoms) and alkenes by catalytic conversion of synthesis gas;
• - Hydroformylation of the product mixture obtained comprising alcohols, alkenes and alkanes, the alkenes being hydroformylated as a mixture to the corresponding aldehydes and / or alcohols with a carbon chain longer by one carbon atom;
• - Separation of the product mixture obtained into a gas phase and a liquid phase;
• - if necessary, recycling of the separated gas phase for the catalytic conversion of the synthesis gas;
• - Separation of the alkanes from the product mixture of the liquid phase;
• optionally purification and separation of the alcohol mixture obtained into individual compounds or groups of compounds, in particular ethanol, propanol, butanol and methanol and optionally higher alcohols;
• - If necessary, conversion of the alkanes separated off to generate CO-rich synthesis gas for the hydroformylation, for example by means of partial oxidation, autothermal reformer (ATR) or steam reforming.

In this fourth variant, the consecutive hydroformylation of the alkenes to alcohols takes place before the gas-liquid separation and thus in the presence of the unconverted synthesis gas and in the presence of the alcohols already formed.

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.

Depending on the product range or if aldehydes are formed in addition to the alcohols in the hydroformylation and the alcohols are the target product of the hydroformylation, a downstream hydrogenation of the aldehydes must be taken into account for all process options. With regard to the choice of the process concept for the catalytic synthesis of higher alcohols with consecutive hydroformylation, the provision of the synthesis gas for the hydroformylation of the alkenes must be taken into account.

In addition to the aforementioned process variants, it is also possible to carry out the hydroformylation of the alkenes by a combination of two or more of the aforementioned process variants. For example, the product mixture of higher alcohols (with at least two carbon atoms) and alkenes, initially obtained by catalytic conversion of synthesis gas, can be hydroformylated by means of process variant 4, mainly to aldehydes and / or alcohols. If the alkenes are not completely converted, the after separation of the product mixture obtained into a gas phase and a liquid phase, in alkenes contained in the liquid phase can be hydroformylated to the corresponding aldehydes and / or alcohols, for example by means of one of process variants 1, 2 or 3.

If necessary, a combination of process variants 1-4 can also lead to advantages in the separation of the product mixture. It can thus be advantageous to separate individual fractions of alcohols and alkenes with the same number of carbon atoms, preferably as aldehydes and / or alcohols instead of as alkenes, from the product mixture of the conversion of synthesis gas to higher alcohols. For example, the separation of the ethene from the product mixture of the higher alcohol synthesis during the separation of the product mixture obtained into a gas phase and a liquid phase is more complex than that of the long-chain alkenes, so that it can be advantageous to choose the reaction conditions of the hydroformylation according to process variant 4 in this way that predominantly the ethene is hydroformylated to propanal or converted to propanol and these compounds are to be separated off in the gas-liquid separation. The hydroformylation of unreacted alkenes can, if appropriate, be carried out according to one of process variants 1, 2 or 3 after separation into a gas and a liquid phase.

From an economic point of view, hydroformylation has the advantage that the hydroformylation of the alkenes leads to aldehydes or alcohols with a longer carbon chain. As a rule, higher prices are achieved for long-chain hydrocarbons and alcohols than for short-chain compounds. Longer alcohols also have a higher energy density. If the products according to the invention are used, for example, as a fuel additive, the higher energy density has a positive effect on the range of the fuel used.

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 _{gases rich in CO and CO 2,} 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 by means of renewable energies and / or in a sustainable manner with low CO ₂ footprints, for example by means of water electrolysis or methane pyrolysis. The alkanes formed in the catalytic conversion of the synthesis gas can, according to an advantageous optional variant of the invention, also be used as a feed stream for generating the synthesis gas which is used in the catalytic conversion.

As part of a further development of the present invention, specific cobalt-containing catalysts were developed which combine the properties of a methanol synthesis catalyst and a Fischer-Tropsch catalyst. In this way, the catalytic conversion of synthesis gas creates a product mixture which, in addition to the higher alcohols (mainly ethanol, propanol and butanol), also has high concentrations of hydrocarbons (mainly C2 - C4 alkenes and C1 - C4 alkanes), water and CO ₂ .

A catalyst is used here; which comprises grains of non-graphitic carbon with cobalt nanoparticles dispersed therein, the cobalt nanoparticles having a mean diameter d _p in the range from 1 nm to 20 nm and the mean distance D between individual cobalt nanoparticles in the grains of non- graphitic carbon is in the range of 2 nm and 150 nm and ω, the combined total mass fraction of the metal in the grains of non-graphitic carbon, in the range of 30% by weight to 70% by weight of the total mass of the grains of non- graphitic carbon, where d _p , D and ω satisfy the following relationship: 4.5 dp / ω> D ≧ 0.25 dp / ω.

In the process according to the invention, it is particularly preferred to use a catalyst material which is doped with a metal selected from Mn, Cu or a mixture of these, the grains of non-graphitic carbon having a molar ratio of cobalt to doped metal in the range from 2 to 15 exhibit.

In experiments within the scope of the present invention it was found that the aforementioned grains of non-graphitic carbon with cobalt nanoparticles dispersed therein can be obtained from aqueous solutions of metallic precursors and organic carbon sources by combined spray-drying or freeze-drying of the aqueous solution and thermal treatment of the intermediate product obtained in this way at moderate temperatures.

Non-graphitic carbon can be identified by a person skilled in the art by TEM analysis (PW Albers, Neutron scattering study of the terminating protons in the basic structural units of non-graphitizing and graphitizing carbons, Carbon 109 (2016), 239 - 245, page 241 , figure 1c).

In comparison to the previous knowledge and also to the descriptions known from the literature, the abovementioned catalysts surprisingly have a significantly higher selectivity for alkenes than for alkanes (for example in the order of about 3: 1). As a result, in addition to the alcohols with the alkenes, the product mixture also contains other valuable products which, from an economic and ecological point of view, can advantageously be used materially and not energetically.

An important aspect in connection with an advantageous development of the invention is the separation of the products of value from the relatively complex product mixture at the reactor outlet. In addition to the products of value alcohols and alkenes, residual gases (depending on the feed gas: H ₂ , CO, CO ₂ , N ₂ ) and by-products (especially alkanes, CO ₂ and H ₂ O).

• 1 ein beispielhaftes Prozessschema betreffend eine erste beispielhafte Ausführungsvariante des erfindungsgemäßen Verfahrens;
• 2 ein beispielhaftes Prozessschema betreffend eine zweite beispielhafte Ausführungsvariante des erfindungsgemäßen Verfahrens;
• 3 ein beispielhaftes Prozessschema betreffend eine dritte beispielhafte Ausführungsvariante des erfindungsgemäßen Verfahrens;
• 4 ein beispielhaftes Prozessschema betreffend eine vierte beispielhafte Ausführungsvariante des erfindungsgemäßen Verfahrens;

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

• 1 an exemplary process scheme relating to a first exemplary embodiment variant of the method according to the invention;
• 2 an exemplary process scheme relating to a second exemplary embodiment variant of the method according to the invention;
• 3 an exemplary process scheme relating to a third exemplary embodiment variant of the method according to the invention;
• 4th an exemplary process scheme relating to a fourth exemplary embodiment variant of the method according to the invention;

First of all, the 1 Reference is made and an exemplary variant of the method according to the invention is explained in more detail on the basis of this schematic representation. From a feed stream 10 , for example from steel mill gas, becomes a synthesis gas 11 a in a device for generating synthesis gas 11 generated comprising CO and H ₂ , optionally CO ₂ , and N ₂ as an inert gas, which a reactor 12th is supplied, in which the synthesis of higher alcohols is carried out at a temperature of, for example, 280 ° C and a pressure of 60 bar on a specific catalyst which comprises grains of non-graphitic carbon with cobalt nanoparticles dispersed therein, the cobalt nanoparticles have a mean diameter d _p in the range of 1 nm to 20 nm and the mean distance D between individual cobalt nanoparticles in the grains of non-graphitic carbon in the range of 2 nm and 150 nm and ω, the combined total mass fraction of the metal in the grains of non-graphitic carbon, ranges from 30% by weight to 70% by weight of the total mass of the grains of non-graphitic carbon, where d _p , D and ω satisfy the following relationship: 4.5 dp / ω> D ≥ 0.25 dp / ω.

That in the reactor 12th The product mixture produced is via the line 13th a facility 14th supplied, in which, for example, at a pressure of 60 bar, which is thus about the same order of magnitude as in the previous synthesis, and at a temperature of, for example, about 30 ° C, a separation into a gas phase and a liquid phase takes place. The separation into a gas phase and a liquid phase can also take place by any other suitable separation processes known to the person skilled in the art. The gas phase is preferably via the line shown in dashed lines 15th in the synthesis of higher alcohols 12th returned.

This recirculated gas phase can contain, for example, N ₂ and CH _{4 in addition to CO, H 2} and CO ₂ . The one in the facility 14th The separated liquid phase contains alcohols, alkenes and alkanes, predominantly with two to four carbon atoms each, with methanol also being contained in the liquid phase. This product mixture of alcohols, alkenes and alkanes is over the line 16 a separator 17th fed, in which the alcohols are separated off from the alkenes and alkanes. The alcohols are over the pipe 18th a facility 19th fed for purification, in which separation into the individual alcohols, for example by distillation, can take place. For example, in addition to methanol, the higher alcohols ethanol, propanol and butanol are obtained via the lines 20 a , 20 b , 20 c and 20 d be led out of the system.

The one in the separator 17th For example, alkenes and alkanes separated off at 30 ° C. and 1 bar pressure are then passed through the line 23 another separator 30th fed, in which a separation the alkanes and alkenes take place, for example, in a C2 cut, a C3 cut and a C4 cut, so that three mixtures of one alkene and one alkane with the same number of carbon atoms are obtained via the three lines 31 a , 31 b and 31 c each reactors 21 a , 21 b and 21 c are fed, in which the hydroformylation is carried out. The synthesis gas 11a for the hydroformylation can be obtained from synthesis gas production 11 come. This hydroformylation is carried out, for example, in each case at a temperature of 180 ° C. and a pressure of 30 bar over a suitable catalyst. There are three separate reactors 21 a , 21 b , 21 c are used, it would also be possible at this point to work with different reaction conditions in each case in the individual reactors in order to adapt the conditions to the hydroformylation of the respective alkene. In this hydroformylation, either aldehydes or aldehydes and alcohols or alcohols directly are produced, with an alkane and an aldehyde and / or alcohol having a carbon chain longer by one carbon atom being present in each of the three product mixtures after the hydroformylation Alkane can be separated from the alcohol and / or aldehyde. The separation of these connections is comparatively easy to accomplish, since these connections can be separated easily due to their different properties. The respective mixtures of alcohol and alkane are supplied via the lines 33 a , 33 b and 33 c discharged from the plant.

In the following, the 2 Reference is made and a second exemplary variant of the method according to the invention is explained in more detail with the aid of this schematic representation. Many elements of the in the embodiment of 2 shown system are similar to that according to 1 and are therefore not explained again in detail here. To that extent, refer to the above explanations 1 Referenced.

The one in the separator 17th For example, alkenes and alkanes separated off at 30 ° C. and 1 bar pressure are not separated into individual Cx cuts here, but rather as a mixture via the line 20th a common reactor 21 fed for the hydroformylation, which is carried out, for example, at a temperature of 180 ° C and a pressure of 30 bar over a suitable catalyst. In this hydroformylation, either aldehydes or aldehydes and alcohols or alcohols are produced directly, which via the line 22nd the separator 24 are supplied, in which the alcohols and / or aldehydes are separated off from the alkanes. The separated alkanes can over the line 25th a facility 26th be fed in by means of the line 27 supplied oxygen a partial oxidation of the alkanes takes place, whereby a synthesis gas comprising CO and H _{2 is} generated, which in turn via the line 28 of hydroformylation 21 can be fed. Alternatively, the synthesis gas can also be used for the hydroformylation 11a from unity 11 be used. The unit 26th is only available as an option.

The one in the separator 24 The separated alcohols and any water present in the product mixture are passed through the line 29 the facility 19th fed for the purification and separation of the alcohols, combined there with the other alcohols and, as already described above, preferably separated into the individual alcohols.

In the following, the 3 Reference is made and a third exemplary variant of the method according to the invention is explained in more detail on the basis of this schematic representation. In contrast to the two variants explained above, here the separation into a gas phase and a liquid phase takes place in the device 14th no separation of the alcohols from the product mixture, but via the line 16 the liquid phase arrives directly in a reactor 21 , in which the hydroformylation takes place, under the above-mentioned reaction conditions. The synthesis gas can come from a device for generating synthesis gas 11 over line 11a are fed to the hydroformylation. The alcohols already generated previously thus remain in the mixture, so that in the hydroformylation a reaction mixture is obtained which essentially consists of alcohols and alkanes or aldehydes, alcohols and alkanes and via the line 32 a separator 24 is supplied, in which the alkanes are separated off from the alcohols (and / or optionally aldehydes). The alcohols are optionally mixed with water via line X of the device 19th fed for purification, in which the separation into the individual alcohols can take place. The separated alkanes can optionally be taken over the line 25th a facility 26th be fed in by means of the line 27 supplied oxygen a partial oxidation of the alkanes takes place, whereby a synthesis gas comprising CO and H _{2 is} generated, which in turn via the line 28 of hydroformylation 21 can be fed.

In the following, the 4th Reference is made and a fourth exemplary variant of the method according to the invention is explained in more detail using this schematic representation. Many elements of the in the embodiment of 4th illustrated system are similar to those according to the variants described above and are therefore not explained again in detail here. To that extent will refer to the explanations above for the 1 to 3 Referenced. With the variant according to 4th however, the hydroformylation takes place in the reactor 21 immediately following the catalytic synthesis of higher alcohols in the reactor 12th . The gas mixture of CO and H ₂ for the hydroformylation can either by partial oxidation of previously separated alkanes in the device 26th and / or it will be generated by the one in the facility 11 generated synthesis gas 11 a via another line 33 Syngas to the reactor 21 fed for hydroformylation.

At the in 4th The variant shown is also separated in the facility 14th into a gas phase and a liquid phase only downstream of the hydroformylation 21 so that unconverted synthesis gas can be present in the hydroformylation. The gas phase from 14 can via line 15th back into the synthesis of higher alcohols ( 12th ) to be led back. The liquid phase from the separator 14th contains, in addition to the alcohols (and / or optionally aldehydes), essentially the alkanes, the alcohols in the separating device 24 separated and then in the facility 19th be purified. The alkanes can optionally be used in the establishment 26th are fed for partial oxidation.

This in 4th The process concept shown refers exclusively to the gas phase hydroformylation with a heterogeneous catalyst. In contrast, for the variants according to 1 to 3 both gas-phase and, optionally, liquid-phase hydroformylation are possible.

The gas-phase hydroformylation is preferably carried out with a large excess of CO (the CO: H ₂ ratio is preferably about 6: 1, but can also be higher, for example about 10: 1) (see also EP000003130399A1 ) in order to increase the selectivity of the hydroformylation and to minimize the hydrogenation of the alkenes to alkanes. Because of this required excess of CO, the direct hydroformylation of the entire product mixture is initially viewed as a less suitable process variant for the consecutive hydroformylation. The catalytic synthesis of the higher alcohols (see reactor 12th ) is preferably carried out with a synthesis gas comprising a ratio of CO: H ₂ of preferably about 1: 1 or CO: H ₂ of about 1: 2.

When using a synthesis gas composition for the catalytic synthesis of higher alcohols from CO: H ₂ of about 1: 1 (100 mol CO, 100 mol H ₂ ) and a CO conversion of, for example, about 40% (assuming H ₂ conversion 80%) a CO-rich synthesis gas mixture with a composition of CO: H ₂ in the ratio of about 3: 1 (60 mol CO, 20 mol H ₂ ), which can be used for the hydroformylation.

Furthermore, the catalytic synthesis of higher alcohols proceeds with a CO excess and a CO: H ₂ ratio of 2: 1 (200 mol CO, 100 mol H ₂ ) with a slightly higher selectivity than with a CO: H ₂ ratio of 1 :1. When using a synthesis gas composition for the catalytic synthesis of higher alcohols of CO: H ₂ equal to 2: 1 and a CO conversion of, for example, 40% (assuming H ₂ conversion 80%), a CO-rich synthesis gas mixture with a composition of CO: H ₂ equal to 8: 1 (160 mol CO, 20 mol H ₂ ) obtained, which can be used for the hydroformylation. These considerations thus show that the catalytic synthesis of higher alcohols and the gas-phase hydroformylation can also be combined well with one another with regard to the synthesis gas mixture used.

example 1

In the following example 1, an exemplary product composition is given, which was obtained in the catalytic conversion of synthesis gas by the method according to the invention using a catalyst which comprises grains of non-graphitic carbon with cobalt nanoparticles dispersed therein, the cobalt nanoparticles a mean diameter d _p in the range of 1 nm to 20 nm and the mean distance D between individual cobalt nanoparticles in the grains of non-graphitic carbon in the range of 2 nm and 150 nm and ω, the combined total mass fraction of the metal in the grains of non-graphitic carbon, in the range of 30% by weight to 70% by weight of the total mass of the grains of non-graphitic carbon, where d _p , D and ω satisfy the following relationship: 4.5 dp / ω> D ≥ 0.25 dp / ω. The catalyst used had a high C2-C4 selectivity, with alcohols, alkenes and alkanes being formed. 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. Table 1 CO selectivity [%] CO ₂ 8th methane 17.9 Ethane 4.6 propane 4.3 butane 3.0 Pentane 0.3 Ethene 6.0 1-propene 15.1 1-butene 7.2 Pents 4.2 Methanol 3.7 Ethanol 4.6 1-propanol 1.1 2-propanol 0.00 1-butanol 18.3 Alkanes (C2 - C5) 12.2 Alkenes (C2 - C5) 32.5 higher alcohols 24.0

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 CO selectivity of the alcohols and alkenes is obtained. In comparison, the selectivity to alkanes is lower. The alkenes can also be converted to alcohols in the subsequent hydroformylation step, so that the conversion of the synthesis gas can be carried out with a CO selectivity of almost 60% to form aldehydes and / or alcohols, a mixture of primary alcohols (methanol, ethanol, 1- Propanol and 1-butanol) from the alcohol synthesis and aldehydes (propanal, butanal, pentanal) and / or alcohols (propanol, butanol, pentanol) from the hydroformylation step and the methanol content being comparatively low. Such an alcohol mixture is suitable, for example, as a fuel additive for admixture with gasoline. Alternatively, separation into the individual alcohols and / or aldehydes is possible.

Example 2

A possible method for separating the product mixture obtained in the catalytic conversion of synthesis gas is described below by way of example. 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 various 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

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 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, which is used in particular to separate the inert gases (nitrogen) and unconverted components of the synthesis gas (hydrogen, carbon monoxide, carbon dioxide and methane), takes place by absorbing the product flow 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 a comparatively high boiling point of in particular more than 200 ° C. The water is not absorbed, but largely condenses as a second liquid phase.

The two liquid phases (organic phase and aqueous phase) can then be separated in a decanter, whereby the hydrocarbons hardly go into the aqueous phase, but some of the alcohols. For example, the alcohols can be distilled out of the water again as azeotropes by means of a first column. Alcohols, hydrocarbons and possibly aldehydes are then desorbed from the diesel oil, which can be done in a column. After desorption, the diesel oil can be returned to the absorption process. 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.

Separation of alcohols / hydrocarbons

The separation of alcohols and hydrocarbons and optionally aldehydes is carried out by distillation in a second column, preferably at a high pressure of, for example, 10 bar to 40 bar, so that the C3 components still remain condensable in the presence of any residues of inert gas. 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.

Representation of the hydrocarbons

In a third distillation column, the hydrocarbons are obtained at the top at an elevated pressure of, for example, 5 bar to 20 bar, while the remaining water and the alcohols dissolved therein and optionally aldehydes are obtained and separated off in the bottom. This stream can be returned to the first distillation column to recover the alcohols and, if appropriate, aldehydes. 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.

Dehydration of the alcohol fraction

The alcohol fraction can have a water content of, for example, about 10%. This water can be removed, for example, by means of a molecular sieve.

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.

List of reference symbols

10

Feed stream

11

Synthesis gas generation / conditioning synthesis gas

11a

Synthesis gas

12th

reactor

13th

management

14th

Separation facility

15th

management

16

management

17th

Separator

18th

management

19th

Purification facility

20th

management

21

Hydroformylation reactor

21 a

Hydroformylation reactor

21 b

Reactor for hydroformylation

21 c

Hydroformylation reactor

22nd

management

23

management

24

Separator

25th

management

26th

Partial oxidation device

27

management

28

management

29

management

30th

Separating device in several Cx cuts

31 a

management

31 b

management

31 c

management

32

management

33

management

QUOTES INCLUDED IN THE DESCRIPTION

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

Patent literature cited

• EP 3130399 A1 [0005]
• DE 4242725 A1 [0006]
• US 6756411 B2 [0007]
• US 6861450 B2 [0008]
• US 6982355 B2 [0009]
• US 9073804 B2 [0010]
• EP 000003130399 A1 [0054, 0091]
• WO 2015/086151 A1 [0056]

Claims (19)

Process for the production of alcohols and / or aldehydes by catalytic conversion of synthesis gas to a first mixture containing alkenes and alkanes, wherein alkenes contained in this mixture are converted into the corresponding aldehydes and / or alcohols in at least one subsequent step by hydroformylation, characterized in that that the first mixture obtained after the catalytic reaction contains, in addition to alkenes and alkanes, at least one alcohol with two to four carbon atoms, which is then obtained as an isolated product by separation and / or purification. Procedure according to Claim 1 , characterized in that from the first mixture of alkanes, alkenes and alcohols obtained after the catalytic conversion of synthesis gas, the alkanes and alkenes are first separated from the alcohols and then the separated alkenes are hydroformylated, optionally mixed with the alkanes. Procedure according to Claim 2 , characterized in that a mixture of separated alkenes, optionally mixed with the alkanes, is first separated into two or more fractions with different numbers of carbon atoms and only then the individual fractions are hydroformylated separately from one another in order to convert the alkenes into the respective fractions to obtain the corresponding aldehydes and / or alcohols. Procedure according to Claim 3 , characterized in that the mixture of alkenes is separated into at least a C2 fraction, a C3 fraction and a C4 fraction and then hydroformylated, and from these fractions, optionally after separation of the respective alkanes, the aldehydes propanal, butanal, pentanal and / or the alcohols propanol, butanol and pentanol are obtained. Procedure according to Claim 2 , characterized in that after the alcohols have been separated off, a mixture containing the alkenes and alkanes, comprising predominantly C2-C4 alkenes, is then hydroformylated as a mixture to give the corresponding aldehydes and / or alcohols. Procedure according to Claim 5 , characterized in that the alkanes are separated from the mixture after the hydroformylation and, if appropriate, the alcohols formed from the alkenes are combined with the alcohols separated off after the first step of the catalytic conversion of synthesis gas and, if appropriate, separated into individual alcohols with different numbers of carbon atoms . Method according to one of the Claims 2 to 5 , characterized in that the alkanes are separated from the alcohols and / or aldehydes and separated alkanes are at least partially converted, in particular by partial oxidation with oxygen, into a CO-rich synthesis gas which is then used for the hydroformylation of the alkenes. Method according to one of the Claims 1 to 7th , characterized in that the hydroformylation is carried out at temperatures in the range from 80 ° C to 200 ° C and / or at a pressure of 10 bar to 300 bar, preferably at a pressure of 15 bar to 100 bar. Procedure according to Claim 1 , characterized in that the hydroformylation of the alkenes with the first mixture of alkanes, alkenes and alcohols obtained in the catalytic conversion of the synthesis gas takes place without the alcohols having been separated off from this mixture beforehand. Method according to one of the Claims 7 or 9 , characterized in that after the hydroformylation, the alkanes are separated from the aldehydes and / or alcohols and the remaining mixture of aldehydes and / or alcohols is optionally purified and / or separated into individual alcohols, in particular methanol, ethanol, propanol and butanol and optionally is separated into individual aldehydes, in particular propanal, butanal and pentanal. Method according to one of the Claims 4 to 10 , characterized in that the alkanes are separated from the aldehydes and / or alcohols at a lower temperature and pressure than the preceding hydroformylation, preferably at a temperature in the range from 20 ° C to 40 ° C and a pressure of less than 5 bar, particularly preferably at a pressure of less than 2 bar. Method according to one of the Claims 1 to 11 , characterized in that before the hydroformylation of the alkenes to the corresponding alcohols and / or aldehydes and after the catalytic conversion 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 and a liquid phase, the liquid phase being used for the subsequent hydroformylation of the alkenes to the alcohols and / or aldehydes and the separation preferably taking place at a lower temperature and / or at approximately the same pressure as the previous catalytic conversion of the synthesis gas. Procedure according to Claim 12 , characterized in that the gas phase obtained in the separation is at least partially returned to the step of catalytic conversion of the synthesis gas. Method according to one of the Claims 1 to 11 , characterized in that after the catalytic conversion of the synthesis gas and after this subsequent hydroformylation of the alkenes to the corresponding alcohols and / or aldehydes, at least one step is provided in which a separation of the product mixture obtained in this reaction into a gas phase and a liquid Phase takes place, after which the alkanes are separated from the liquid phase. Procedure according to Claim 14 , characterized in that the gas phase obtained in the separation is at least partially returned to the step of catalytic conversion of the synthesis gas. Method according to one of the Claims 12 to 15th , characterized in that after the catalytic conversion of the synthesis gas, the product mixture is processed which comprises at least the following steps: At least partial absorption of the alkenes and alcohols and optionally the alkanes or at least partial absorption of the alkenes, alcohols and aldehydes 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; - if necessary, distilling out the alcohols from the aqueous phase; - Desorption of the alkenes, alkanes and alcohols or desorption of the alkenes, alkanes, alcohols and aldehydes from the absorption medium. Procedure according to Claim 16 , characterized in that before or after the hydroformylation, the separation of the alcohols from the alkenes and alkanes or the separation of the alcohols from the alkanes or the separation of the alcohols and aldehydes from the alkanes comprises at least the following steps: separation of the alcohols and / or Aldehydes in at least one distillation column at an elevated pressure of preferably at least 10 bar; - Removal of the water from the alcohol fraction, preferably by means of a molecular sieve, by extractive distillation, by pervaporation or by azeotropic distillation. Method according to one of the Claims 1 to 17th , characterized in that a catalyst is used in the catalytic conversion of the synthesis gas which comprises grains of non-graphitic carbon with cobalt nanoparticles dispersed therein, the cobalt nanoparticles having an average diameter d _p in the range from 1 nm to 20 nm and the mean distance D between individual cobalt nanoparticles in the grains of non-graphitic carbon is in the range of 2 nm and 150 nm and ω, the combined total mass fraction of the metal in the grains of non-graphitic carbon, in the range of 30 wt % to 70% by weight of the total mass of the grains of non-graphitic carbon, where d _p , D and ω satisfy the following relationship: $$4.5\text{dp /}\mathrm{\omega }\text{> D}\ge \text{0}\text{.25 dp /}\mathrm{\omega }.$$

Procedure according to Claim 18 , characterized in that the catalyst material is doped with a metal selected from Mn, Cu or a mixture of these, the grains of non-graphitic carbon having a molar ratio of cobalt to doped metal in the range from 2 to 15.

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