DE102020106009A1 - METHOD AND SYSTEM FOR ESTABLISHING A TARGET LINK - Google Patents

Abstract

The invention relates to a method for producing a target compound (6) using an aldehyde, the target compound being an alcohol formed from the aldehyde or a further compound formed from at least part of the alcohol, and the aldehyde in a component mixture (1) is provided which has lower boiling components than the aldehyde. Using an extractive distillation (E), an (alcohol) synthesis feed (2) enriched in the aldehyde and depleted in the components boiling lower than the aldehyde is formed from the component mixture (1) and subjected to a reaction to form the alcohol. The alcohol is at least partially used to form an entrainer (4) for the extractive distillation (E). A corresponding system (100) is also the subject of the invention.

Description

The present invention relates to a method for producing a target compound using an aldehyde and a corresponding plant according to the preambles of the independent claims.

The project that led to the present patent application was funded under grant agreement No. 814557 of the European Union's Horizon 2020 research and innovation program.

State of the art

The production of alcohols from aldehydes and in particular of propanol via propanal is known in principle. For example in Article “Propanols” in Ullmann's Encyclopedia of Industrial Chemistry, 2012 edition , a heterogeneous gas phase process is described, which is carried out at 110 to 150 ° C and a pressure of 0.14 to 1.0 MPa with a ratio of hydrogen to propanal of 20: 1. A reduction takes place in the case of excess hydrogen and the heat of the reaction is removed by circulating the gas phases through external heat exchangers or by cooling the reactor inside. The efficiency based on hydrogen is more than 90%, the conversion of the aldehyde takes place up to 99.9% and alcohol yields of more than 99% result. Commonly used commercial catalysts include combinations of Cu, Zn, Ni and Cr supported on alumina or diatomaceous earth. Dipropyl ether, ethane and propyl propionate are mentioned as the main impurities.

Details for corresponding liquid phase processes are also given in the literature. These are carried out, for example, at a temperature of 95 to 120 ° C. and a pressure of 3.5 MPa. Typically Ni, Cu, Raney Ni or supported Ni catalysts reinforced with Mo, Mn and Na are preferred as catalysts. For example, 1-propanol can be produced in these liquid phase processes with a purity of 99.9%.

An important problem with the purification of propanol is the removal of water from the product mixture of the process. If, as in one embodiment of the present invention, propanol is dehydrated to propylene, i.e. the propanol is only used as an intermediate in the synthesis of an olefin from propanol, water is also one of the reaction products in this dehydration step, so that water does not have to be separated off beforehand . The separation of propylene and water is comparatively easy. The separation of components other than water is often more difficult in this context, especially if these other components have a significantly lower boiling point than the aldehyde and cannot be removed by condensation.

The aldehyde which is used in a corresponding process can be provided, for example, using a hydroformylation. Typical hydroformylation processes on an industrial scale mostly start from a relatively pure feed stream with a high alkene content. Therefore, the mentioned lower-boiling components, for example carbon dioxide, lower-boiling hydrocarbons, in particular methane, but also unconverted carbon monoxide and hydrogen, are usually not present in significant amounts in the product stream either. Novel processes for the hydroformylation of alkenes, which can also process less pure and / or dilute feed streams, are, for example, from the DE 10 2019 119 543 , the DE 10 2019 119 562 and the DE 10 2019 119 540 known.

Carbon monoxide and carbon dioxide can act as inhibitors in the hydrogenation described at the outset or can also lead to undesired by-products.

In principle, there is a multitude of different processes for converting hydrocarbons and related compounds into one another, some of which are to be named below by way of example.

For example, the conversion of alkanes to alkenes of the same chain length by oxidative dehydrogenation (ODH, in the case of ethane also referred to as ODHE) is known. Typically, in the case of ODH, a carboxylic acid of the same chain length, i.e. acetic acid, is formed as a by-product in the case of ODHE. Ethylene can also be produced by the oxidative coupling of methane (OCM).

The production of propylene from propane by dehydrogenation (PDH) is also known and is a commercially available and established process. This also applies to the production of propylene from ethylene by alkene metathesis. This process requires 2-butene as the starting product.

Finally, there are so-called methane-to-olefin or methane-to-propylene processes (MTO, MTP), in which synthesis gas is first produced from methane and the synthesis gas is then converted into alkenes such as ethylene and propylene. Corresponding processes can be operated on the basis of methane, but also on the basis of other hydrocarbons or carbon-containing raw materials such as coal or biomass.

The production of propylene (propene) is also described in detail in the specialist literature, for example in the article "Propylene" in Ullmann's Encyclopedia of Industrial Chemistry, 2012 edition. Propylene is conventionally produced by steam cracking of hydrocarbon feeds and conversion processes in the course of refinery processes . In the latter process, propylene is not necessarily formed in the desired amount and only as one of several components in a mixture with other compounds. Other processes for the production of propylene are also known, but not in all cases, for example in terms of efficiency and yield, are satisfactory.

An increasing demand for propylene is forecast for the future (“propylene gap”), which requires the provision of appropriate selective processes. At the same time, it is important to reduce or even prevent carbon dioxide emissions. On the other hand, large quantities of methane are available as a potential feedstock;

As already mentioned, hydroformylation (also referred to as oxo synthesis) represents a further technology which is used in particular for the production of oxo compounds of the type mentioned at the beginning. Typically, ethylene or propylene are converted in the hydroformylation, but it is also possible to use higher hydrocarbons, in particular hydrocarbons with six to eleven carbon atoms. The conversion of hydrocarbons with four and five carbon atoms is also possible, but of less importance. The hydroformylation, in which aldehydes are initially formed, can be followed by a hydrogenation. This is also the case with embodiments of a method according to the invention. Alcohols formed by such a hydrogenation can then also be dehydrated to the respective alkenes.

at Green et al., Catal. Lett. 1992, 13, 341 describes a process for the production of propanal from methane and air. In the process presented, basically low yields based on methane are recorded. In the process, an oxidative coupling of methane (OCM) and a partial oxidation of methane (POX) to hydrogen and carbon monoxide are carried out, which is then followed by hydroformylation. The target product is the mentioned propanal, which has to be isolated as such. One limitation arises from the oxidative coupling of methane to ethylene, for which only lower conversions and limited selectivities are typically achieved at present.

The hydroformylation reaction in the process just mentioned is carried out over a typical catalyst at 115 ° C. and 1 bar in an organic solvent. The selectivity for the (undesired) by-product ethane is in the range from approx. 1% to 4%, whereas the selectivity for propanal should reach more than 95%, typically more than 98%. Extensive integration of process steps or the use of carbon dioxide, which is formed in large quantities as a by-product in the oxidative coupling of methane in particular, is not further described here, so that there are disadvantages compared to conventional processes. Because partial oxidation is used as a downstream step for oxidative coupling in the process, i.e. there is a sequential interconnection, large amounts of unconverted methane from oxidative coupling have to be dealt with in the partial oxidation or separated in a costly manner.

In the U.S. 6,049,011 A describes a process for the hydroformylation of ethylene in dilute streams. The ethylene can in particular be formed from ethane. In addition to propanal, propane can also be produced as a target product.

Alcohols formed can also be further dehydrated to alkenes. However, this publication also does not disclose any further integration or advantageous solution for the separation of low-boiling compounds.

The object of the present invention is to provide an improved process for the preparation of target products such as alcohols or alkenes from aldehydes.

Disclosure of the invention

Against this background, the present invention proposes a method for producing a target compound using an aldehyde and a corresponding plant with the respective features of the independent claims. Preferred embodiments of the present invention are the subject matter of the dependent claims and the following description.

According to the invention, the aldehyde serves as the starting compound for the synthesis of the target compound, optionally via one or more intermediates. The aldehyde can be provided by means of process steps which can also be part of the present invention. The target compound can in particular be an alcohol which can be formed from the aldehyde, in particular by hydrogenation, but also an olefin which in turn can be prepared from such an alcohol, in particular by dehydration. In the latter case, an olefin is produced as the target product, the aldehyde being converted to the olefin via an alcohol as an intermediate product. More generally, within the scope of the present invention, the target product represents an alcohol formed from this aldehyde or a compound formed in turn from the alcohol. Therefore, if “the alcohol” is mentioned below, it is the target product or the intermediate product.

Regardless of the specific embodiments of the invention, i.e. regardless of which target product is provided, the aldehyde is provided in the context of the present invention in a component mixture which has components that boil below the aldehyde, in particular below 0 ° C.

According to the invention, an (alcohol) synthesis feed enriched in the aldehyde and depleted in the components boiling lower than the aldehyde is formed from the component mixture using an extractive distillation and is subjected to a reaction to form the alcohol as the target or intermediate product. According to the invention, at least some of the alcohol is used to form an entrainer used in the extractive distillation. The reaction to form the target product can also be one of several synthetic steps on the way to the target product.

In the context of the present invention, the aldehyde and the alcohol are, in particular, compounds with linear carbon chains of equal chain length with terminal aldehyde or alcohol groups. The chain length can be 2 to 20, in particular 2 to 10, further in particular 2, 3, 4, 5, 6 or 7. In particular, the aldehyde is propanal and the alcohol is 1-propanol. If the target compound is a compound formed from the alcohol and not the alcohol itself, the target compound can in particular be an olefin, in particular propylene in the case just explained. However, the invention is not restricted to this, although the following explanations relate predominantly to these compounds.

If it is also mentioned here that “a” aldehyde is converted to “a” alcohol and possibly further to “a” olefin, it goes without saying that the corresponding process variants can also include the processing of several corresponding compounds. The compounds boiling lower than the aldehyde can in particular be lighter hydrocarbons, for example methane, ethane or ethylene, and non-hydrocarbons boiling lower than the aldehyde, such as carbon dioxide, carbon monoxide and hydrogen. In particular, the compounds mentioned boil lower than water in liquid form.

As mentioned, the invention comprises providing the aldehyde in a component mixture which contains the components mentioned which have a lower boiling point than the aldehyde. In particular, the oxidative dehydrogenation and / or oxidative coupling of methane explained below, in each case followed by a hydroformylation, but also any other suitable process that provides a corresponding mixture of components can be used here. The invention is not limited by this, but the present invention can include corresponding method steps, for example in accordance with those already mentioned DE 10 2019 119 543 , DE 10 2019 119 562 and DE 10 2019 119 540 , as part of the proposed process and is particularly advantageously also suitable for processes in which significant amounts of the mentioned, lower-boiling than the aldehyde components are contained in the component mixture, for example for processes that include a step of the oxidative coupling of methane.

As already mentioned at the beginning, oxidative dehydrogenation is a method known in principle from the prior art. In the context of the present invention, known process concepts can be used for the oxidative dehydrogenation. For example, a method can be used in the oxidative dehydrogenation in the context of the present invention, as in Cavani et al., Catal. Today 2007, 127, 113 , is revealed. In particular, catalysts containing V, Sr, Mo, Ni, Nb, Co, Pt and / or Ce and other metals can be used in conjunction with silicate, aluminum oxide, molecular sieve, membrane and / or monolith supports. For example, combinations and / or oxides of corresponding metals, for example MoVTeNb oxides and mixed oxides of Ni with Nb, Cr and V can also be used in the context of the present invention. Examples are at Melzer et al., Angew. Chem. 2016, 128, 9019, Gärtner et al., ChemCatChem 2013, 5, 3196, and Meiswinkel, “Oxidative Dehydrogenation of Short Chain Paraffines”, DGMK Conference Report 2017-2 , ISBN 978-3-941721-74-6, as well as various patents and patent applications by the applicant.

A typical by-product of the oxidative dehydrogenation is essentially the respective carboxylic acid in all process variants, i.e. in the case of the oxidative dehydrogenation of ethane, acetic acid, which may have to be separated off, but may represent a further product of value and typically in contents of a few percent (up to low double-digit percentage range). Carbon monoxide and carbon dioxide are also formed in the low percentage range. A typical product mixture for the oxidative dehydrogenation of ethane has, for example, the following mixture proportions: Ethylene 25 to 75 mole percent Ethane 25 to 75 mole percent acetic acid 1 to 20 mole percent Carbon monoxide 0.5 to 10 mole percent carbon dioxide 0.5 to 10 mole percent

In comparison, a typical product mixture of the oxidative coupling of methane has, for example, the following mixture proportions: hydrogen 0.1 to 10 mole percent methane 20 to 90 mole percent Ethane 0.5 to 30 mole percent Ethylene 5 to 60 mole percent Carbon monoxide 0.5 to 30 mole percent carbon dioxide 0.5 to 30 mole percent

These details relate in each case to the dry portion of the product mixture which, depending on how the process is carried out, may contain water vapor. Further components can be contained in traces, i.e. typically less than 1%. It should be mentioned here that all proportions and quantitative ratios described in this disclosure relate to the amount of substance (which in the case of gases generally also corresponds to the volume fraction), unless explicitly stated otherwise.

Since the oxidative coupling of methane is used in a preferred embodiment of the present invention, it is first explained in more detail below. The oxidative coupling of methane is described in the literature, for example at JD Idol et al., "Natural Gas", in: JA Kent (Ed.), "Handbook of Industrial Chemistry and Biotechnology", Volume 2, 12th Edition, Springer, New York 2012 . In principle, however, processing of other gas mixtures, ie not provided by the oxidative coupling, is also possible and advantageous within the scope of the present invention if these gas mixtures contain one or more olefins in an appreciable content, for example more than 10, 20, 30, 40 or 50 mole percent and up to 80 mole percent (as individual or sum values) and carbon monoxide in just such quantity ranges. If the present invention is described below with specific reference to the oxidative coupling of methane and ethylene which is formed in the oxidative coupling, this is not intended to imply any restriction.

According to the current state of knowledge, the oxidative coupling of methane comprises a catalyzed gas phase reaction of methane with oxygen, in which two methane molecules each have a hydrogen atom is split off. Oxygen and methane are activated on the surface of the catalyst. The resulting methyl radicals initially react to form an ethane molecule. A water molecule is also formed in the reaction. With suitable molar ratios of methane to oxygen, suitable reaction temperatures and the choice of suitable catalytic conditions, the ethane is then oxydehydrogenated to ethylene, a target compound in the oxidative coupling of methane. Another water molecule is formed here. The oxygen used is typically completely converted in the reactions mentioned.

The reaction conditions in the oxidative coupling of methane typically include a temperature of 500 ° C. to 900 ° C., a pressure of 0.5 MPa to 1 MPa and high space velocities. More recent developments also go in particular towards the use of lower temperatures. The reaction can be carried out homogeneously or heterogeneously in a fixed bed or in a fluidized bed. In the oxidative coupling of methane, higher hydrocarbons with up to six or eight carbon atoms can also be formed, but the focus is on ethane or ethylene and possibly also propane or propylene.

In particular, due to the high binding energy between carbon and hydrogen in the methane molecule, the yields in the oxidative coupling of methane are comparatively low. Typically no more than 10% to 15% of the methane used is converted. In addition, the comparatively harsh reaction conditions and temperatures required to cleave these bonds also favor the further oxidation of the methyl radicals and other intermediates to carbon monoxide and carbon dioxide. The use of oxygen in particular plays a dual role here. The methane conversion depends on the oxygen concentration in the mixture. The formation of by-products is linked to the reaction temperature, since the total oxidation of methane, ethane and ethylene preferably takes place at high temperatures.

Although the low yields and the formation of carbon monoxide and carbon dioxide can partly be counteracted by the choice of optimized catalysts and adapted reaction conditions, a gas mixture formed during the oxidative coupling of methane contains, in addition to the target compounds such as ethylene and possibly propylene, predominantly unconverted methane and carbon dioxide, Carbon monoxide and water. Any non-catalytic cleavage reactions that may take place may also contain considerable amounts of hydrogen. In the parlance used here, such a gas mixture is also referred to as a “product mixture” of the oxidative coupling of methane, although it predominantly does not contain the desired products, but also the unreacted starting material methane and the by-products just explained.

In the oxidative coupling of methane, reactors can be used in which a catalytic zone is followed by a non-catalytic zone. The gas mixture flowing out of the catalytic zone is transferred to the non-catalytic zone, where it is initially still at the comparatively high temperatures that are used in the catalytic zone. In particular, due to the presence of the water formed during the oxidative coupling of methane, the reaction conditions here are similar to those of conventional vapor cracking processes. Therefore ethane and higher paraffins can be converted into olefins here. Further paraffins can also be fed into the non-catalytic zone, so that the residual heat from the oxidative coupling of methane can be used in a particularly advantageous manner.

Such a specific steam cracking in a non-catalytic zone downstream of the catalytic zone is also referred to as “post bed cracking”. The term “post-catalytic vapor splitting” is also used for this in the following. If it is stated below that a starting gas mixture used according to the invention is formed or provided “using” or “using” an oxidative coupling of methane, this information should not be understood to mean that only the oxidative coupling itself is used in the provision got to. Rather, the provision of the starting gas mixture can also include further method steps, in particular post-catalytic steam splitting.

In the context of the present invention, the alkene formed, for example, in the oxidative dehydrogenation and / or oxidative coupling of methane with carbon monoxide and hydrogen can be subjected to hydroformylation to obtain an aldehyde.

Processes for hydroformylation are also known in principle from the prior art. At present, Rh-based catalysts are typically used in corresponding processes, as described in the literature cited below. Older processes also use Co-based catalysts.

For example, homogeneous, Rh (I) -based catalysts with phosphine and / or phosphite ligands can be used. These can be monodentate or bidentate complexes. Reaction temperatures of 80 to 150 ° C. and appropriate catalysts are typically used for the production of propanal. All of the methods known from the prior art can also be used within the scope of the present invention.

The hydroformylation typically works with a ratio of hydrogen to carbon monoxide of 1: 1. However, this ratio can in principle be in the range from 0.5: 1 to 10: 1. The Rh-based catalysts used can have a Rh content of 0.01 to 1.00 percent by weight, it being possible for the ligands to be present in excess. Further details are in the A Article “Propanal” in Ullmann's Encyclopedia of Industrial Chemistry, 2012 edition described. The invention is not restricted by the process conditions mentioned.

In a further process, as described, for example, in the “Hydroformylation” chapter in Moulijn, Makee & van Diepen, Chemical Process Technology, 2012, 235, a pressure of 20 to 50 bar for a Rh-based catalyst and a Co -based catalyst, a pressure of 70 to 200 bar is used. Co also appears to be relevant for hydroformylation in metallic form. Other metals are more or less insignificant, especially Ru, Mn and Fe. The temperature range used in the process mentioned is between 370 K and 440 K.

In the process disclosed in the chapter “Synthesis involving Carbon Monoxide” in Weissermel & Arpe, Industrial Organic Chemistry 2003, 135, mainly Co- and Rh-phosphine complexes are used. With specific ligands, the hydroformylation can be carried out in an aqueous medium and the catalyst can be recovered easily.

According to Navid et al., Appl. Catal. A 2014, 469, 357 In principle, all transition metals that are capable of forming carbonyls can be used as potential hydroformulation catalysts, with activity according to this publication according to Rh>Co> Ir, Ru>Os>Pt>Pd>Fe> Ni being observed .

By-products in hydroformylation arise in particular from the hydrogenation of the alkene to the corresponding alkane, e.g. from ethylene to ethane, or the hydrogenation of the aldehyde to alcohol, i.e. from propanal to propanol. According to the article “Propanols” in Ullmann's Encyclopedia of Industrial Chemistry, 2012 edition, propanal formed by hydroformylation can be used as the main source of 1-propanol in industry. In a second step, propanal is to be hydrogenated to 1-propanol.

In the context of the present invention, the provision of the aldehyde in the component mixture can thus comprise, for example, using an oxidative dehydrogenation and / or oxidative coupling to form an alkene from an alkane, then at least part of the alkene formed in these reactions with carbon monoxide and hydrogen To subject the aldehyde to a hydroformylation, and to use at least part of a product mixture formed in the hydroformylation to form the component mixture. The component mixture thus contains, in addition to products from oxidative dehydrogenation and / or oxidative coupling and hydroformylation, in particular unconverted starting materials and by-products. If, for example, ethane is used as starting material in the oxidative dehydrogenation, the component mixture can contain unconverted ethane. In the case of oxidative coupling, in particular unconverted methane can be contained in the component mixture in considerable amounts. Furthermore, the component mixture can also contain ethylene from the stream subjected to hydroformylation, which was not converted in the hydroformylation, as well as components used in the hydroformylation but not converted, such as hydrogen, carbon dioxide and / or carbon monoxide.

Extractive distillation (extractive rectification) is known to be a method of distillation for separating liquid mixtures using a comparatively high-boiling, in particular selective solvent, which is also referred to here as an entrainer. Extractive distillation is based on the fact that the relative volatility of the components to be separated is influenced by the entrainer. In particular, the relative volatility of one of the components can be increased or the activity coefficients of the components to be separated can be changed significantly in different directions. The result is a positive change in the separation factor in terms of separation technology.

As mentioned, the present invention comprises the conversion of the aldehyde formed, for example, in a hydroformylation, which is contained in the component mixture used, to a corresponding alcohol and optionally a further conversion, in particular to an alkene, if the alcohol is not the final target product. The conversion of the aldehyde to the alcohol takes place in particular in the form of a catalytic hydrogenation and a further conversion of the alcohol to the alkene in the case explained last in the form of a dehydration with the formation of water.

The hydrogenation of unsaturated components is a well-known and established technology for the conversion of components with a double bond into the corresponding saturated compounds. Typically, very high or complete conversions can be achieved with selectivities of well over 90%. Typical catalysts for the hydrogenation of carbonyl compounds are based on Ni, such as, for example, im Article "Hydrogenation and Dehydrogenation" in Ullmann's Encyclopedia of Industrial Chemistry, 2012 edition described. Noble metal catalysts can also be used especially for olefinic components. Hydrogenation is one of the standard reactions in industrial chemistry, as is, for example, with M. Baerns et al., “Example 11.6.1: Hydrogenation of Double Bonds”, Technische Chemie 2006, 439 , shown. In addition to unsaturated compounds, other groups of substances are also hydrogenated, for example aldehydes and ketones. Low-boiling substances such as butyraldehyde from hydroformylation are hydrogenated in the gas phase. The hydrogenation catalysts used here are Ni and certain noble metals such as Pt and Pd, typically in supported form.

The dehydration of alcohols over suitable catalysts to produce the corresponding alkenes is also known. In particular, the production of ethylene (from ethanol) is common and is gaining importance in connection with the increasing production quantities of (bio) ethanol. The commercial application has been realized by different companies. For example, consider the ones already mentioned Article "Propanols" in Ullmann's Encyclopedia of Industrial Chemistry and Intratec Solutions, "Ethylene Production via Ethanol Dehydration", Chemical Engineering 120, 2013 , 29 referenced. The dehydration of 1- or 2-propanol to propylene has no practical value. However, dehydration of 2-propanol is easiest in the presence of mineral acid catalysts at room temperature or above. The reaction itself is endothermic and equilibrium limited. High conversions are favored by low pressures and high temperatures. Typically, heterogeneous catalysts based on Al ₂ O ₃ or SiO ₂ are used. In general, several types of acidic catalysts are suitable, and molecular sieves and zeolites, for example, can also be used. Typical temperatures are in the range from 200 to 250 ° C for the dehydration of ethanol or at 300 to 400 ° C for the dehydration of 2-propanol or butanol. Due to the equilibrium limitation, the product stream is typically separated off (separation of the alkene product and also at least partially of the water by, for example, distillation) and the stream, which contains unconverted alcohol, is returned to the reactor inlet.

The present invention thus proposes, in embodiments, the coupling of an aldehyde supply process, which in particular comprises the production of the aldehyde, and (at least) a downstream hydrogenation, the alcohol product of the hydrogenation or a part thereof being used to form an entrainer for an extraction or extractive distillation of the crude aldehyde and is recycled accordingly in this way. In general, however, the alcohol product can also be used to form an entrainer in the extractive distillation when methods other than those described are used to provide a component mixture to be processed accordingly. The use “for the formation” of an entrainer does not exclude that a corresponding alcohol is previously used, for example as an absorbent as explained below, and therefore the composition of the entrainer differs.

Particular advantages arise within the scope of the present invention in particular from the fact that the extractive distillation can be carried out using the alcohol, which is formed in particular in the hydrogenation as an intermediate or target product, and that the remaining components are made up of a product mixture of the aldehyde production process (“Crude aldehyde”) can be separated in the extractive distillation without complex cryogenic separation steps. In particular, components that do not take part in the reaction, such as alkanes and carbon dioxide, but also not completely converted starting materials such as alkenes, carbon monoxide and hydrogen, can be carried along and separated off more easily. In particular, the unreacted starting materials can be simply recycled in this way, for example, and used again in the reaction feed to produce the aldehyde. Also can hydrogen that in previous Reaction steps formed or not implemented, can be used for later hydrogenation steps. A separation and / or enrichment of hydrogen can also take place, for example, by separation steps known per se, such as pressure swing adsorption.

As mentioned, in the aldehyde production process, in particular in the form of oxidative dehydrogenation with subsequent hydroformylation, in particular a carboxylic acid can be formed as a further by-product, in the case of ethane as use in the oxidative dehydrogenation in particular acetic acid. These and other by-products and / or unreacted feedstocks from a process for providing the feed stream used for the hydroformylation can, together with water of reaction, comparatively easily, for example by condensation and / or water scrubbing, from a corresponding feed or product stream upstream or downstream the step in which the aldehyde is formed, in particular the hydroformylation, are at least partially separated off. Due to its polarity, carbon dioxide can also be removed comparatively easily from a corresponding mixture, it being possible to use known methods for carbon dioxide removal, in particular corresponding washes (for example amine and / or lye washes). Cryogenic separation is not necessary, so that the entire process of the present invention, at least including the aldehyde production process, in particular hydroformylation, and extractive distillation, does not require cryogenic separation steps.

This dispensing with cryogenic separation is also advantageous for the reason that the component mixture containing the aldehyde does not need to be dried upstream of the separation. This advantage applies in the same way to a CO ₂ removal from the component mixture containing the aldehyde upstream of the separation. In certain embodiments, if necessary partial drying and / or CO ₂ removal can be provided, but with regard to the extractive distillation and also the subsequent hydrogenation process, it is not absolutely necessary.

The just mentioned by-products and / or unconverted or incompletely converted educts are advantageously separated off completely non-cryogenically and are therefore extremely simple in terms of apparatus and energy consumption. This represents a significant advantage of the present invention compared to processes according to the prior art, which typically require an expensive separation of undesired components in subsequent process steps. The use of a process-internal stream as an entrainer also prevents foreign substances, which may be difficult to separate from a product mixture, from being introduced into the process. This therefore has an advantageous effect on product purity and process economy.

A “non-cryogenic” separation denotes a separation or a separation step which is carried out at a temperature level above 0 ° C., in particular above ambient temperature. In any case, in the context of this disclosure, “non-cryogenic” also means in particular that no C3 and / or C2 refrigerant has to be used, which means at least temperatures of above -30 ° C, in particular above -20 ° C.

The aldehyde used in the context of the present invention has a relatively high vapor pressure compared to the alkenes and / or alkanes additionally contained in the component mixture, so that a simple distillation results in corresponding losses in the top product or the distillation column requires a large number of theoretical plates . In this way, the outlay on equipment and thus the costs increase significantly. In particular in the case of the lightest aldehyde propanal used in the context of the present invention, this is particularly true. It is precisely here that the high proportions of methane and / or ethane have a particularly negative effect due to the comparatively close proximity of the vapor pressures and / or boiling points. According to the invention, this disadvantage is overcome by designing the separation as an extractive distillation using the alcohol formed in the hydrogenation as extraction or entrainer. According to the invention, only very little aldehyde is lost in the separation step, since most of the aldehyde, which otherwise remains gaseous, is dissolved in the entrainer or passes into the bottom liquid.

Frequently, the components present in a component mixture, as can also be used according to the invention, are not infinitely miscible with one another. In particular, it depends to a large extent on the set conditions whether there may be miscibility gaps with two liquid phases. This means that the choice of suitable process conditions can be severely restricted. In particular, the use of light alcohols, such as propanol, that is, an alcohol that is formed as a product or intermediate in the context of the present invention, has a beneficial effect here again because it can then be mixed with both water and can mix with hydrocarbons. Possible miscibility gaps are thus significantly reduced or even avoided by using the present invention.

In order to separate propanal and propanol from the components boiling lower than the aldehyde, in the case of classic distillation, a reflux must be generated from these components. This requires a correspondingly low, mostly cryogenic head temperature, which in turn provokes miscibility gaps. In addition, as already stated, at such low temperatures, a prior separation of carbon dioxide and / or water is typically necessary in order to prevent the formation of solid deposits (dry ice / ice). This disadvantage is also overcome by using the invention.

In particular, the extractive distillation is carried out in such a way that at least 60%, 70%, 80%, 90%, 95%, 99% or 99.9% of the aldehyde contained in the component mixture, but possibly also contained water, is separated off in a bottom stream is, that is to say can be converted into a liquid fraction formed there, and in particular can be converted into the subsequent hydrogenation.

The extractive distillation is advantageously carried out in such a way that at most 40%, 30%, 20%, 10%, 5%, 1% or 0.1% of the components boiling below the aldehyde are separated off in the bottom stream, i.e. in a liquid fraction formed there be convicted.

The bottom stream thus advantageously consists predominantly of the aldehyde and the alcohol as entrainer and possibly water, while a corresponding overhead stream of the extractive distillation consists in particular of lower-boiling compounds than the aldehyde, which are also less soluble in the aldehyde than the aldehyde Alcohol or the entrainer, as well as any water contained.

In this context, it should be noted that water, when it is present in low concentrations, has a significantly higher vapor pressure than pure water. This is due to the fact that the vapor pressure or the associated boiling temperature of the pure or at least highly concentrated water can be traced back to the strong hydrogen bonds between individual neighboring water molecules. In low concentrations only a few water molecules are adjacent to one another, so that only a few hydrogen bonds can be formed. In such a situation, the vapor pressure or the boiling temperature of the water fraction is dominated by the molecular mass, which results in a comparatively low boiling temperature or a comparatively high vapor pressure. Therefore, depending on the composition of the distillation feed, water present in the distillation feed can either be separated off preferably into the top stream or preferably into the bottom stream of the extractive distillation. The present invention avoids the formation of azeotropes by the extractive distillation designed according to the invention.

The by-products of the oxidative dehydrogenation in the component mixture, if formed in this way, typically include unreacted alkane, carbon dioxide and carbon monoxide. In the case of oxidative coupling, due to typically low conversions, unconverted methane in particular is usually a main constituent of the component mixture (in addition to carbon dioxide and carbon monoxide). These compounds can be converted into the subsequent hydroformylation without problems. Carbon monoxide can be reacted with the alkene together with additionally supplied carbon monoxide, which can come from dry reforming, for example. The alkane is typically not converted in the hydroformylation. Since the aldehydes formed in the hydroformylation are heavier compounds with a higher boiling point or a different polarity, they can, as already mentioned, be separated comparatively easily and also non-cryogenically from the remaining alkane in the extractive distillation according to the invention.

In one embodiment of the invention, the conversion of the aldehyde to the alcohol by the hydrogenation is particularly advantageous because for this excess hydrogen contained in a product mixture of the hydroformylation can be used, which is already present in a feed mixture upstream of the hydroformylation and is passed through the hydroformylation can. A content of hydrogen and carbon monoxide in a starting mixture of the hydroformylation can be set in the context of the present invention, in particular in a water gas shift of a basically known type.

In the process according to the invention and its embodiments, hydrogen can be fed in at any suitable point, in particular upstream of the hydrogenation. In this way, hydrogen is available for this hydrogenation. The feed does not need to be immediately upstream of the Hydrogenation to take place; rather, hydrogen can also be fed in by process or separation steps that are present or carried out upstream of the hydrogenation.

In a particularly preferred embodiment of the method according to the invention, an additional absorption is also provided, with an overhead gas being subjected to extractive distillation using an absorption liquid which is formed using at least part of the alcohol and a liquid fraction is obtained. In this way, a further improved depletion of the undesired components with lower aldehyde losses is achieved at the same time. In this embodiment of the invention, the liquid fraction formed in the absorption is advantageously used at least in part to form the entrainer for the extractive distillation. In other words, the alcohol is used here first as an absorption agent and then, when it is already partially loaded, as an entrainer in the extractive distillation. The absorption phase and the entrainer phase have different compositions due to the loading of the alcohol in the absorption.

In particular, the alcohol formed during the reaction of the aldehyde can be separated off from unconverted alkane in a comparatively simple manner. In this way, a recycle stream of the alkane can also be formed here non-cryogenically and, for example, returned to the oxidative dehydrogenation and / or oxidative coupling.

The present invention also extends to a system for producing a target compound, with respect to which reference is expressly made to the corresponding independent patent claim. A corresponding system, which is preferably set up to carry out a method, as previously explained in different configurations, benefits in the same way from the advantages already mentioned above.

The following examples, which should contribute to a better understanding of the general explanations, represent various advantageous embodiments of an extractive distillation according to the invention (Examples 3 and 7a / b / c each without additional absorber, Examples 4 and 8a / b / c each with an additional absorber). Examples 2 and 6 each serve as a comparison case of a conventional distillation without extraction and absorption. The pressure is set to a pressure level of 2.0 MPa in each case. The theoretical number of plates for the distillation or extractive distillation is indicated by n (stages column), while the number of plates in the absorber n (absorber) is only indicated if an absorber is also provided (Examples 4 and 8a / b / c).

Examples 1 and 5 each serve to define an exemplary feed stream (also referred to as a feed stream) for the other examples that follow.

Only mass flows (in kg / h) or proportions (in mol%) for hydrocarbons, propanal, hydrogen, carbon monoxide and carbon dioxide are listed. Other trace components and in particular proportions of water are not taken into account.

The distillations in the examples are each characterized by the corresponding temperature levels in the sump (T_Bottom), at the top condenser (T_Condenser) and that of the exiting top stream (T_OVHD). The temperature T_Feed indicates the temperature level of the feed stream supplied from example 1 or 5 into the column and the temperature T_propanol the temperature level at which the entrainer propanol is fed into the column. The boil-up ratio describes the ratio of the boiled liquid, which is then sent back to the separation as a gas, and the liquid product stream withdrawn as the bottom product of the distillation (in each case in kg / h).

Furthermore, the corresponding mass flows for the feed stream from Example 1 or 5 in the respective distillation and for the entrainer propanol are given. The tables Flow OVHD [kg / h] and Flow Bottom [kg / h] each specify the proportional composition of the top and bottom flows of the respective separation.

1. 1. Efficieny OVHD [split top:bottom in wt.-%] das Verhältnis Propanal über Kopf zu Propanal über Sumpf
2. 2. Efficiency Bottom [split bottom:top in wt.-%] das Verhältnis Propanal über Sumpf zu Propanal über Kopf

For each of the distillations, the propanal distribution between the top and bottom streams was calculated as a decisive efficiency criterion. Specify accordingly:

1. 1. Efficiency OVHD [split top: bottom in wt .-%] the ratio of propanal overhead to propanal overhead
2. 2. Efficiency bottom [split bottom: top in wt .-%] the ratio of propanal over the bottom to propanal overhead

Ie the value for efficiency bottom [split bottom: top in wt .-%] should be as close as possible to 100 wt .-%, in this case propanal is thus completely transferred into the bottom stream of the column. Correspondingly, the value for efficiency OVHD [split bottom: top in wt .-%] should be as close as possible to 0 wt .-%, ie in this case the top stream contains little or no more propanal.

Example 1 - Provision of a feed stream from a hydroformylation

It is an example of a feed stream A. fed to a hydroformylation. 90% conversion of ethylene takes place there, carbon monoxide and hydrogen are converted accordingly stoichiometrically. Further side reactions (for example hydrogenation of ethylene to ethane and / or propanal to propanol) do not take place in this example or in a negligibly small amount. The product flow is created B. of hydroformylation. Table 1: Composition of the feed and product streams according to Example 1. Feed stream A for hydroformylation Product stream B of the hydroformylation Composition [mol%] Mass flow [kg / h] Composition [mol%] Mass flow [kg / h] propane 1,500 2.951 1,829 2.951 Propylene 1,500 2.816 1,829 2.816 Ethylene 10,000 12,516 1.220 1.252 Ethane 2,000 2,683 2,439 2,683 CO 10,000 12.497 1.220 1,250 CO ₂ 1,000 1.964 1.220 1.964 Propanal 0.000 0.000 10.976 23,322 H ₂ 12,000 1.079 3,659 0.270 methane 62,000 44.378 75.610 44.378 total 100 80.884 100 80.886

Example 2 - Distillation without extraction and absorption (comparative case not according to the invention for Examples 3 and 4)

The product stream B. from example 1 becomes in this comparative example 2 fed to a distillation column. The exact data can be found in Table 2.

Example 3 - extractive distillation without absorber

The product stream B. Example 1 becomes one of the in 1 shown and described in more detail below embodiment of the invention corresponding extractive distillation supplied without absorber. The exact data and results can be found in Table 2.

Example 4 - extractive distillation with absorber

The product stream B. from example 1 according to the in 2 The embodiment of the invention shown and explained in more detail below is fed to an extractive distillation with absorber.

It is clear that under the conditions chosen, the extractive distillation with propanol recirculation (Example 3) reduces the propanal loss via the overhead stream compared to a standard distillation (Comparative Example 2 ) already significantly reduced. The additional absorption (Example 4) then leads to an almost quantitative propanal yield in the bottom stream. Table 2: Comparison of the separation processes according to Examples 2, 3 and 4. Example 2 Example 3 Example 4 T_Bottom [° C] 170 189 181 T_OVHD [° C] 20th 20th 39 Propanol [kg / h] 0 20th 15th T_Propanol [° C] - 20th 20th T_Feed [° C] 70 70 70 T_Condenser [° C] 20th 20th 30th p [MPa] 2.0 2.0 2.0 Feed [kg / h] 80.88 80.88 80.88 n (stages column) 20th 20th 20th n (absorber) - - 12th Boil-up ratio 1.5 1.5 1.3 Efficiency OVHD [split top: bottom in wt .-%] Propanal 18.57 14.13 0.157 Flow OVHD [kg / h] propane 2.951 2.951 2.951 Propene 2.816 2.816 2.816 Propanal 4,330 3,296 <0.1 Ethylene 1.252 1.252 1.252 Ethane 2,683 2,683 2,683 CO 1,250 1,250 1,250 CO ₂ 1.964 1.964 1.964 H ₂ 0.270 0.270 0.270 methane 44.378 44.378 44.378 total 61.893 60.859 57,599 Efficiency bottom [split bottom: top in wt .-%] Propanal 81.43 85.87 99.84 Flow bottom [kg / h] propane <0.01 <0.01 <0.01 Propylene <0.01 <0.01 <0.01 Propanal 18,992 20.026 23.285 Ethylene <0.01 <0.01 <0.01 Ethane <0.01 <0.01 <0.01 CO <0.01 <0.01 <0.01 CO ₂ <0.01 <0.01 <0.01 H ₂ <0.01 <0.01 <0.01 methane <0.01 <0.01 <0.01 total 18,992 20.026 23.285 Total flows Ovhd + Bottom [kg / h] total 80.88 80.88 80.88

Example 5

In this example, a stream C is provided as the feed stream, which can be processed further in one embodiment of the method according to the invention. This corresponds to the remaining gas phase fraction from the material flow B. after condensation and separation of a liquid phase at 40 ° C. Table 3: Composition of a material flow according to BeisDiel 5. Material flow C composition Mass flow [mol%] [kg / h] propane 1.91 2,868 Propylene 1.86 2.656 Ethylene 1.30 1,237 Ethane 2.59 2,650 CO 1.31 1.247 CO2 1.28 1.916 Propanal 4.64 9.156 H ₂ 3.94 0.270 methane 81.17 44.235 total 100.00 66.235

Example 6 - Distillation without extraction and absorption (comparative case not according to the invention for Examples 7 and 8)

The stream C from Example 5 is fed to a distillation column. The exact data can be found in Table 4.

Examples 7a and 7b - Extractive distillation without absorber

The stream C from Example 5 becomes one of the in 1 The embodiment of the invention shown and described in detail below is supplied to corresponding extractive distillation without absorber.

The temperature at the top condenser is varied (example 7a: 30 ° C.; example 7b: 20 ° C.). The exact data and results are shown in Table 4.

Examples 8a, 8b and 8c - extractive distillation with absorber

The stream C from Example 5 is an extractive distillation with absorber, according to the embodiment of the invention, which in 2 is shown fed. The reflux of propanol (example 8a and 8c: 20 kg / h; example 8b: 15 kg / h) and the number of plates in the absorber (example 8a: 12; example 8b: 10; example 8c: 20) are varied. The temperature levels of the top and bottom fractions result from the other parameters. The exact data and results are shown in Table 4.

In these examples, the extractive distillation (Examples 7a and 7b) already leads to an improvement in the Efficiency OVHD value by more than the factor 4th compared to the reference case (example 6). The additional absorption (Examples 8a, 8b and 8c) in turn lead to an almost quantitative propanal yield in the bottom stream. Table 4: Comparison of the separation processes according to Examples 6, 7a, 7b and 8a to 8c. example 6th 7a 7b 8a 8b 8c T_Bottom [° C] 197 197 197 194 191 194 T_OVHD [° C] 20th 30th 20th 37 33 36 Propanol [kg / h] 0 20th 20th 20th 15th 20th T_Propanol [° C] - 20th 20th 20th 20th 20th T_Feed [° C] 40 40 40 40 40 40 T_Condenser [° C] 20th 30th 20th 30th 30th 30th p [bar] 20th 20th 20th 20th 20th 20th Feed [kg / h] 66.55 66.55 66.55 66.24 66.24 66.24 n (stages column) 20th 20th 20th 20th 20th 20th n (absorber) - - - 12th 10 20th Boil-up ratio 1.5 1.5 1.5 1.5 1.3 2.3 Efficiency OVHD [split top: bottom in wt .-%] Propanal 45.62 10.91 10.30 0.004 0.096 <0.001 Flow OVHD [kg / h] propane 2.872 2.872 2.872 2.867 2.867 2,868 Propylene 2.665 2.665 2.665 2.656 2.656 2.656 Propanal 4.309 1.030 0.973 <0.01 <0.01 <0.01 Ethylene 1.238 1.238 1.238 1,237 1,237 1,237 Ethane 2.652 2.652 2.652 2,650 2,650 2,650 CO 1.248 1.248 1.248 1.247 1.247 1.247 CO ₂ 1.919 1.919 1.919 1.916 1.916 1.916 H ₂ 0.270 0.270 0.270 0.270 0.270 0.270 methane 44.244 44.244 44.244 44.235 44.235 44.235 total 61,416 58.137 58.079 57.079 57.087 57.079 Efficiency bottom [split bottom: top in wt .-%] Propanal 54.38 89.09 89.70 100 99.90 100 Flow bottom [kg / h] propane <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 Propylene <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 Propanal 5.137 8.416 8.475 9.156 9.148 9.156 Ethylene <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 Ethane <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 CO <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 CO ₂ <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 H ₂ <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 methane <0.01 <0.01 <0.01 <0.01 <0.01 <0.01 total 5.137 8.416 8,474 9.156 9.148 9.156 Total flows Ovhd + Bottom [kg / h] total 66.55 66.55 66.55 66.24 66.24 66.24

The invention is explained in more detail below with reference to the accompanying drawings, which illustrate preferred embodiments of the present invention.

Figure list

• 1 shows an advantageous embodiment of a system according to the invention in a greatly simplified schematic representation.
• 2 shows a further advantageous embodiment of a system according to the invention.

Refinements of the invention

The following statements, which relate to the systems shown in the figures, apply in an analogous manner to the corresponding methods. For the sake of clarity, process steps that are carried out in a system component are denoted by the same reference symbols as the respectively corresponding system component. If, for example, the description says that a material flow is fed to a system component, this is to be understood on the one hand to mean that this material flow is subjected to the corresponding process step in one embodiment of the process in this system component. On the other hand, with regard to the design of the system, this is to be understood in such a way that a corresponding line, for example in the form of a pipeline, is provided in which the material flow can be guided into the system component. The same applies to the case of a material flow formed in a process step, which is accordingly led out of the relevant system component.

In the 1 illustrated system 100 to establish a target connection 6th includes an extractive distillation column E. , a hydrogenation reactor H and a return device R.

A mixture of components 1 is in the extractive distillation column E. out and there at least partially separated, so that an (alcohol) synthesis feed 2 as a bottom product and a top product 5 are formed. The component mixture 1 contains, inter alia, an aldehyde, for example propanal.

The extractive distillation column E. becomes an entrainer 4th fed that an alcohol with the same chain length as the aldehyde in the component mixture 1 contains, in particular 1-propanol, or consists essentially of it. For example, the entrainer 4th , which is in a head area of the extractive distillation column E. is fed, have a proportion of 1-propanol of more than 75%, 80%, 90%, 95% or 99%, for example a proportion of approx. 95% 1-propanol.

In the one from the extractive distillation column E. outward synthesis insert 2 is the aldehyde compared to the component mixture 1 enriched while others in the component mixture 1 contained components of the type explained above, for example an alkene, in particular ethylene, carbon monoxide, hydrogen and / or an alkane, in particular ethane, in the synthesis insert leaving the extractive distillation column 2 compared to the component mixture 1 are depleted. The use of synthesis 2 also contains a relatively large proportion of the entrainer 4th .

The component mixture 1 can, depending on the design of a provision B. of the component mixture 1 , have a very high methane content (for example when using an oxidative coupling of methane) of for example 30% to 90%, but can also be essentially free of methane in other configurations (for example when using oxidative dehydrogenation). This example can also contain 0.1% to 10% hydrogen, for example, and 5% to 50% propanal. Furthermore, other highly volatile components such as carbon dioxide, carbon monoxide, propane, propylene, ethane and / or ethylene can be contained in variable amounts, but limited in their proportion to a total of less than 50%, in particular less than 30%. As already mentioned several times, these values relate to the dry (i.e. anhydrous) portion of the component mixture 1 . The component mixture 1 however, it can also contain water, in particular be water-saturated. In the case of oxidative dehydrogenation, the proportion for the further highly volatile components mentioned is typically up to 65% in total, in particular up to 40%.

The extractive distillation column E. can for example be operated in such a way that the entrainer 4th is fed in with a mass flow which is between 10% and 50%, in particular between 15% and 30%, for example approx. 25%, of the mass flow of the extractive distillation column E. supplied component mixture 1 is equivalent to.

A bottom evaporator of the extractive distillation column E. is operated in a temperature range between 50 ° C and 300 ° C, in particular between 100 ° C and 280 ° C, in particular between 150 ° C and 250 ° C, for example about 170 ° C to 190 ° C, while a corresponding top condenser is on a temperature of -30 ° C to 50 ° C, in particular between normal temperature (according to DIN 1945-1) and 45 ° C, but in any case in a non-cryogenic temperature range, for example at about 20 ° C.

The extractive distillation column is advantageously used E. operated in a pressure range between 0.5 MPa and 10 MPa, in particular between 1 MPa and 5 MPa, for example at about 1.5 MPa to 3.5 MPa.

The extractive distillation column E. is designed in particular as a column with internals, a (theoretical or actual) number of plates in the range between 5 and 100, in particular between 10 and 50, for example 20, being advantageous.

After going through the extractive distillation E. contains the bottom stream or (alcohol) synthesis feed 2 in this example more than 85% of that in the distillation feed 1 contained propanals, while via the corresponding overhead stream 5 less than 15% of the propanal used from the extractive distillation column E. escape. The ones mentioned above, in the sump stream 2 Any other volatile components contained therein represent, at most, traces of impurities in the bottom stream 2 Their cumulative proportion is limited to the low two-digit ppm range, for example below 20 ppm. The extractant 4th goes essentially completely, in particular to a proportion of more than 85%, 90%, 95% or 99%, into the bottom stream, so that its proportion in the bottom stream 2 between 20% and 90%, in particular between 30% and 70%, for example about 45% to 55%.

In the head stream 5 is therefore only a little entrainer 4th contain the volatile components of the distillation insert 1 however, in each case to their vast majority, in particular over 99% or over 99.9%.

The swamp stream 2 is downstream of the extractive distillation column E. as an insert 2 into the hydrogenation reactor H fed in. In addition to the use 2 hydrogen (not shown in the figures) is also fed into the hydrogenation reactor. The hydrogen can, for example, from the overhead stream 5 the extractive distillation column E. be separated, for example using an adsorption and / or membrane process. The one in action 2 contained aldehyde (propanal) is in the hydrogenation reactor H reacted with the hydrogen to form the corresponding alcohol (1-propanol). Typically, a high to almost complete conversion of more than 85%, 90%, 95%, 99% or 99.9% is achieved with a high product selectivity of well over 90%.

A product stream leaving the hydrogenation reactor 3 can therefore essentially consist of the alcohol formed and may still contain small amounts of unreacted aldehyde and hydrogen. Part of the product flow 3 can be used as a dilution stream 7th in (alcohol) synthesis use 2 upstream of the hydrogenation reactor H be recycled in order to better control the process conditions in the hydrogenation reactor H to enable. In this way, the concentration of aldehyde to be converted can be set and, moreover, it can also influence that in the reactor H prevailing temperatures.

Another part of the product stream 3 is fed to the return device R, in which a division of the product flow 3 he follows. At least some of the alcohol contained in the product stream is used as the entrainer 4th to the extractive distillation column E. recycled while another part of the product stream 3 , optionally using further reactors and / or purification stages, as the target compound 6th from the plant 100 is discharged.

In the product stream 3 Any hydrogen present can be returned to the extractive distillation column together with the extractant, where, as described, it is largely via the overhead stream formed there 5 is expelled. Any unreacted aldehyde present in the product stream can also be used together with the entrainer 4th into the extractive distillation column E. returned and so in use 2 upstream of the hydrogenation reactor H be recycled.

In the 2 illustrated system 200 to establish a target connection 6th essentially corresponds to the system in terms of its components 100 related to 1 have already been described in detail. Corresponding components of the system 200 are therefore given the same reference numerals as those of the system 100 and not described repeatedly for the sake of clarity.

In the 2 illustrated system 200 points compared to the plant 100 an additional absorber A. on, in the sump area of the overhead stream 5 the extractive distillation column E. and an absorbent in its head area 8th be fed in. The principle is how the absorber works A. with that of the extractive distillation column E. identical, but the operating parameters of the two differ from each other. In this example, the absorber is operated with a sump temperature in the range from 20 ° C. to 60 ° C., in particular from 30 ° C. to 50 ° C., for example from approx. 40 ° C.

The (theoretical or actual) number of plates of the absorber can be between 5 and 30, in particular between 10 and 15, for example 12.

The absorbent 8th can, for example, also take the alcohol from the product stream 3 contain. However, it is also provided in certain configurations that another absorbent 8th used to avoid product loss via an overhead stream 9 of the absorber. The liquid bottom stream of the absorber can be used together with the extractant 4th and / or one in the top condenser of the extractive distillation column E. formed condensate stream in the head of the extractive distillation column E. to be led back.

As a result of the resulting additional separation stage, the in the distillation insert 1 Aldehyde contained separated much more efficiently in the bottom stream of the extractive distillation column, so that the top stream 9 of the absorber contains practically no more aldehyde, or the aldehyde leaving the absorber makes up a proportion of the amount used in the distillation 1 contained aldehyde is less than 1%, 1%, 100 ppm or 10 ppm. The overall yield of a method according to the invention using the plant 200 is therefore particularly high without sacrificing selectivity.

It should be expressly pointed out here that the absorber A. not necessarily directly to the top of the extractive distillation column E. must be set up, as shown in 2 is shown, although this is the preferred embodiment from a process-economical point of view. However, space filling requirements, for example, can also make a different arrangement necessary, which can nevertheless benefit from the advantages of this variant.

It can also be provided that upstream of the extractive distillation column E. the plant 100 or 200 a condenser is arranged, which serves to the majority of the in the distillation insert 1 to liquefy existing aldehyde and transfer it separately to the hydrogenation reactor, so that the extractive distillation column E. can be dimensioned smaller, since then an overall smaller volume flow of the distillation insert 1 is to be edited.

In each case there is a provision unit B. provided for the hydrogenation H required aldehyde supplies. The delivery unit B. can for example, as mentioned at the beginning, comprise one or more reactors for dry reforming of carbon dioxide, for oxidative coupling of methane, for oxidative dehydrogenation of ethane and / or for hydroformylation of ethylene as well as corresponding separation devices for purifying corresponding material flows. Optionally, part of the extractive distillation column can be used E. and / or the absorber A. leaving overhead stream 5 , 9 to one or more of the reactors of the supply unit B. which in turn increases the overall efficiency of the plant 100 , 200 can be increased.

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

• DE 102019119543 [0006, 0026]
• DE 102019119562 [0006, 0026]
• DE 102019119540 [0006, 0026]
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Claims (14)

Process for the preparation of a target compound (6) using an aldehyde, wherein the target compound is an alcohol formed from the aldehyde or a further compound formed from at least part of the alcohol, and wherein the aldehyde is provided in a component mixture (1) which having components boiling lower than the aldehyde, characterized in that an (alcohol) synthesis feed (2) enriched in the aldehyde and depleted in the components boiling lower than the aldehyde is formed from the component mixture (1) using an extractive distillation (E) and is subjected to a reaction to form the alcohol, the alcohol being at least partially used to form an entrainer (4) for the extractive distillation (E). Procedure according to Claim 1 , wherein the aldehyde and the alcohol are compounds with linear carbon chains of the same length and with a terminal aldehyde or alcohol group. Procedure according to Claim 2 , wherein a chain length of the carbon chains of the aldehyde and the alcohol is 2 to 20. Procedure according to Claim 3 where the aldehyde is propanal, the alcohol is propanol and the target compound is propanol or propylene formed from the propanol. The method according to any one of the preceding claims, wherein the compounds which boil lower than the aldehyde contain at least one from the group comprising carbon dioxide, carbon monoxide, water, hydrogen, one or more alkanes and one or more alkenes. Method according to one of the preceding claims, in which the provision (B) of the aldehyde in the component mixture (1) comprises forming an alkene from an alkane by means of an oxidative dehydrogenation and / or an oxidative coupling, at least part of the alkene thus formed subjecting to hydroformylation to obtain the aldehyde, and to use at least part of a product mixture formed in the hydroformylation to form the component mixture (1). Process according to one of the preceding claims, in which the aldehyde is converted at least in part to the alcohol by hydrogenation and at least in part of the alcohol is converted to an olefin by dehydration if the alcohol is not the target product. Method according to one of the preceding claims, wherein at most 40%, 30%, 20%, 10%, 5%, 1% or 0.1% of the components contained in the component mixture (1) and boiling lower than the aldehyde in one in the Extractive distillation (E) formed liquid fraction are transferred. Process according to one of the preceding claims, wherein in the extractive distillation at least 60%, 70%, 70%, 80%, 90%, 95%, 99% or 99.9% of the aldehyde contained in the component mixture (1) from the component mixture ( 1) be converted into a liquid fraction formed in the extractive distillation (E). The method according to any one of the preceding claims, which further comprises an absorption (A), wherein an overhead gas of the extractive distillation (E) using an absorption liquid which is formed using at least part of the alcohol, and obtaining a liquid fraction of the absorption (A) is subjected. Procedure according to Claim 10 , the liquid fraction formed in the absorption being used at least in part to form the entrainer for the extractive distillation (4). The method according to any one of the preceding claims, wherein the extractive distillation (E) with a bottom temperature in the range from 50 ° C to 300 ° C, preferably from 100 ° C to 280 ° C, in particular from 150 ° C to 250 ° C, a top temperature in Range from -30 ° C to 50 ° C, preferably from 0 ° C to 40 ° C, in particular from 15 ° C to 35 ° C and at a pressure in the range from 0.5 MPa to 10 MPa, preferably from 1.5 MPa to 5 MPa, in particular from 1.5 MPa to 3.5 MPa. Plant (100) for producing a target compound (6) using an aldehyde, the target compound being an alcohol formed from the aldehyde or a further compound formed from at least part of the alcohol, the plant (100) having means which is set up to convert the aldehyde into to provide a component mixture (1) which has components boiling lower than the aldehyde, characterized by an extractive distillation column (E) which is set up to convert from the component mixture (1) a component that is enriched in the aldehyde and depleted in the components boiling lower than the aldehyde Forming (alcohol) synthesis feed (2) and subjecting it to a reaction to form the alcohol, a recirculation device (R) being provided which is set up to remove the alcohol from the at least partially supplied to the extractive distillation column (E) to form an entrainer (4) to use. Appendix (100) according to Claim 13 , which is also set up to implement a method according to one of the Claims 1 until 12th perform.

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