description

Process and plant for the production of a target compound

The present invention relates to a method for producing a target compound, in particular propylene, and a corresponding plant according to the preambles of the independent patent 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 programme.

State of the art

The preparation of propylene (propene) is described 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 (Steam

cracking) of hydrocarbon feeds and conversion processes in the course of refinery processes. In the latter process, propylene will not

necessarily in the desired quantity and only as one of several

Components formed in a mixture with other compounds. Other

Processes for the production of propylene are also known, but they are not always satisfactory, for example in terms of efficiency and yield.

An increasing demand for propylene ("propylene gap") is forecast for the future, which requires the provision of corresponding selective processes. At the same time, it is important to reduce or even prevent carbon dioxide emissions. As a potential

On the other hand, large quantities of methane are available as feedstocks, which are currently only recycled to a very limited extent and are mostly burned.

The object of the present invention is to provide a process for the production of propylene which is improved in particular in view of these aspects, but also for the production of other organic target compounds, in particular of

Oxo compounds such as aldehydes and alcohols with a corresponding

Carbon backbone to provide.

Disclosure of Invention

Against this background, the present invention proposes a method

Preparation of a target compound, in particular propylene, and a corresponding system with the respective features of the independent claims.

Preferred configurations of the present invention are the subject matter of the dependent patent claims and the following description.

Basically, in addition to the above-mentioned steam cracking processes, there are a large number of different processes for converting hydrocarbons and related compounds into one another, some of which will be mentioned below as examples.

For example, the conversion of paraffins to olefins of the same chain length by oxidative dehydrogenation (ODH, also referred to as ODHE in the case of ethane) is known. The production of propylene from propane by dehydrogenation (PDH) is also known and is a commercially available and established process. The same applies to the production of propylene from ethylene by olefin metathesis. This process requires 2-butene as an additional starting material.

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 olefins such as ethylene and propylene. Corresponding methods can be based on methane, but also based on other hydrocarbons or carbonaceous

Starting materials such as coal or biomass are operated.

However, ethylene can also be produced by oxidative coupling of methane (OCM), as is the case in one embodiment of the invention and explained below.

In principle, the present invention is suitable for use with all of them

Methods in which a product mixture is formed which, in addition to an olefin, for example ethylene, also contains carbon dioxide and/or carbon monoxide (which can optionally be converted into one another by a water gas shift) in appreciable amounts,

for example a content of 1 to 30 mole percent, in particular from 1 to 20, from 1 to 15 or from 5 to 10 mole percent. A corresponding gas mixture can also contain, in particular, methane and/or a paraffin, in particular a paraffin with the same chain length as the olefin. Since it forms the basis of the method described here, it is referred to here as the “starting gas mixture”. In the following, the oxidative coupling of methane is predominantly used as an example of such a method; however, the invention is not limited to this.

According to a particularly preferred embodiment of the present invention, the oxidative coupling of methane is used to provide the starting mixture, so that this should first be explained in more detail. The oxidative coupling of methane is described in the literature, for example by J.D. Idol et al., "Natural Gas", in: J.A. Kent (ed.), "Handbook of Indus trial chemistry and biotechnology",

Volume 2, 12th edition, Springer, New York 2012.

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

One hydrogen atom is split off from each methane molecule. Oxygen and methane are activated on the catalyst surface. The resulting methyl radicals initially react to form an ethane molecule. A water molecule is also formed in the reaction. With suitable ratios of methane to oxygen, suitable reaction temperatures and the choice of suitable ones

Under catalytic conditions, ethane is then oxydehydrogenated to ethylene, a target compound in the oxidative coupling of methane. Another water molecule is formed. The oxygen used is typically completely converted in the reactions mentioned.

The reaction conditions in the oxidative coupling of methane classically involve a temperature of 500 to 900 °C, a pressure of 5 to 10 bar and high space velocities. More recent developments are also moving in the direction of using lower temperatures. The reaction can take place with homogeneous or heterogeneous catalysis in a fixed bed or in a fluidized bed. During 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

With 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 favor the cleavage of these

Bonds are required, as well as further oxidation of the methyl radicals and other intermediates to carbon monoxide and carbon dioxide. In particular, the use of oxygen plays a dual role here. So is the methane conversion from the

oxygen concentration in the mixture. The formation of by-products is coupled with the reaction temperature, since the total oxidation of methane, ethane, and ethylene occurs preferentially at high temperatures.

Although the low yields and the formation of carbon monoxide and

Carbon dioxide can be partially counteracted by the choice of optimized catalysts and adapted reaction conditions, a gas mixture formed in the oxidative coupling of methane contains, in addition to the target compounds such as ethylene and possibly propylene, predominantly unreacted methane as well as carbon dioxide, carbon monoxide and water. Considerable amounts of hydrogen can also be present as a result of non-catalytic cleavage reactions that may take place. In the language 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 case of 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 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 steam cracking processes. Therefore, ethane and higher paraffins can be converted to 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 utilized in a particularly advantageous manner.

Such targeted steam cracking in one of the catalytic zones

downstream non-catalytic zone is also referred to as "post bed cracking". The term “post-catalytic steam cracking” is also used for this below. If it is subsequently stated that a starting gas mixture used according to the invention is formed or provided "using" or "using" an oxidative coupling of methane, this statement should not be understood in such a way that only the oxidative coupling itself is used in the provision got to. Rather, from the provision of the starting gas mixture, further process steps, in particular

post-catalytic steam cracking.

According to particularly preferred embodiments of the present invention, paraffins, in particular ethane, which are separated from any streams at a suitable point or enth in corresponding streams can be old, be recycled alone or together with other components for post-catalytic steam cracking. The separation, if made, takes place at

technically suitable location, i.e. at a position at which the separation is particularly inexpensive and, in particular, non-cryogenically possible. If in the following it is mentioned that ethane or another paraffin besides methane is "returned to the process", this can in particular mean a return to the post-catalytic steam cracking. In contrast, methane that is “returned to the process” is used in particular for the oxidative coupling of methane.

However, recycling can also take place together and in particular together with carbon monoxide in the overall oxidative coupling.

Steam reforming and dry reforming as well as modifications thereof including a downstream water gas shift are available as individual technologies

Adjustment of the ratio of hydrogen to carbon monoxide is also known.

Hydroformylation represents a further technology which is used in particular for the production of oxo compounds of the type mentioned at the outset.

Propylene is typically reacted in the hydroformylation, but higher hydrocarbons, in particular hydrocarbons having six to eleven carbon atoms, can also be used. In principle, the reaction of hydrocarbons with four and five carbon atoms is also possible, but of less practical importance. Hydroformylation, in which aldehydes can initially be formed, can be followed by hydrogenation. Alcohols formed by such a hydrogenation can then be dehydrated to the respective olefins.

In Green et al., Catal. Latvia 1992, 13, 341 describes a process for the production of propanal from methane and air. In principle, low yields based on methane are recorded in the process presented. The process involves oxidative coupling of methane (OCM) and partial oxidation of methane (POX) to hydrogen and carbon monoxide, followed by hydroformylation. The target product is the propanal mentioned, which has to be isolated as such. A limitation results from the oxidative coupling of methane to ethylene, for which currently only lower conversions and limited selectivities are typically achieved. Differences in Green et al. described methods of the present invention are explained below with reference to the advantages attainable according to the present invention.

The hydroformylation reaction in the process just mentioned is carried out on a typical catalyst at 1-15°C and 1 bar in an organic solvent. The selectivity to the (undesirable) by-product ethane is in the range of about 1% to 4%, whereas the selectivity to propanal should reach more than 95%, typically more than 98%. Extensive integration of

Process steps or the use of the carbon dioxide formed in large quantities as a by-product, in particular in the oxidative coupling of methane, is not described further here, so that there are disadvantages compared to conventional processes. Because the partial oxidation is used as a downstream step for the oxidative coupling in the process, i.e. there is a sequential connection, large amounts of unreacted methane from the oxidative coupling have to be dealt with in the partial oxidation or separated at great expense.

In US Pat. No. 6,049,011 A is a process for the hydroformylation of ethylene

described. The ethylene can be formed in particular from ethane. as

In addition to propanal, the target product can also be produced with propionic acid. Dehydration is also possible. However, this publication also does not disclose any further integration and does not disclose any meaningful use of the carbon dioxide formed.

Advantages of the Invention

Against this background, the present invention proposes a method

Production of a target compound, in particular propylene, in which a starting gas mixture is provided which contains an olefin, in particular ethylene, carbon monoxide and carbon dioxide. The provision of

Starting gas mixture can include, in particular, that a paraffin, in particular methane, is subjected to a process in which the components mentioned are formed in the starting gas mixture from precursors or starting compounds. In a particularly preferred embodiment, the process can include subjecting methane to an oxidative coupling with oxygen to obtain an olefin, in particular ethylene and the other components mentioned as secondary compounds. The starting gas mixture can, in particular, also contain methane and a paraffin, in particular ethane, which has the same chain length as the olefin. The starting mix can be old, be recycled alone or together with other components for post-catalytic steam cracking. The separation, if made, takes place at

technically suitable location, i.e. at a position at which the separation is particularly inexpensive and, in particular, non-cryogenically possible. If in the following it is mentioned that ethane or another paraffin besides methane is "returned to the process", this can in particular mean a return to the post-catalytic steam cracking. In contrast, methane that is “returned to the process” is used in particular for the oxidative coupling of methane.

However, recycling can also take place together and in particular together with carbon monoxide in the overall oxidative coupling.

Steam reforming and dry reforming as well as modifications thereof including a downstream water gas shift are available as individual technologies

Adjustment of the ratio of hydrogen to carbon monoxide is also known.

Hydroformylation represents a further technology which is used in particular for the production of oxo compounds of the type mentioned at the outset.

Propylene is typically reacted in the hydroformylation, but higher hydrocarbons, in particular hydrocarbons having six to eleven carbon atoms, can also be used. In principle, the reaction of hydrocarbons with four and five carbon atoms is also possible, but of less practical importance. Hydroformylation, in which aldehydes can initially be formed, can be followed by hydrogenation. Alcohols formed by such a hydrogenation can then be dehydrated to the respective olefins.

In Green et al., Catal. Latvia 1992, 13, 341 describes a process for the production of propanal from methane and air. In principle, low yields based on methane are recorded in the process presented. The process involves oxidative coupling of methane (OCM) and partial oxidation of methane (POX) to hydrogen and carbon monoxide, followed by hydroformylation. The target product is the propanal mentioned, which has to be isolated as such. A limitation results from the oxidative coupling of methane to ethylene, for which currently only lower conversions and limited selectivities are typically achieved. Differences in Green et al. described methods of the present invention are explained below with reference to the advantages attainable according to the present invention.

The hydroformylation reaction in the process just mentioned is carried out on a typical catalyst at 1-15°C and 1 bar in an organic solvent. The selectivity to the (undesirable) by-product ethane is in the range of about 1% to 4%, whereas the selectivity to propanal should reach more than 95%, typically more than 98%. Extensive integration of

Process steps or the use of the carbon dioxide formed in large quantities as a by-product, in particular in the oxidative coupling of methane, is not described further here, so that there are disadvantages compared to conventional processes. Because the partial oxidation is used as a downstream step for the oxidative coupling in the process, i.e. there is a sequential connection, large amounts of unreacted methane from the oxidative coupling have to be dealt with in the partial oxidation or separated at great expense.

In US Pat. No. 6,049,011 A is a process for the hydroformylation of ethylene

described. The ethylene can be formed in particular from ethane. as

In addition to propanal, the target product can also be produced with propionic acid. Dehydration is also possible. However, this publication also does not disclose any further integration and does not disclose any meaningful use of the carbon dioxide formed.

Advantages of the Invention

Against this background, the present invention proposes a method

Production of a target compound, in particular propylene, in which a starting gas mixture is provided which contains an olefin, in particular ethylene, carbon monoxide and carbon dioxide. The provision of

Starting gas mixture can include, in particular, that a paraffin, in particular methane, is subjected to a process in which the components mentioned are formed in the starting gas mixture from precursors or starting compounds. In a particularly preferred embodiment, the process can include subjecting methane to an oxidative coupling with oxygen to obtain an olefin, in particular ethylene and the other components mentioned as secondary compounds. The starting gas mixture can, in particular, also contain methane and a paraffin, in particular ethane, which has the same chain length as the olefin. The starting mix ch typically also contains water. Hydrogen can also be contained in the starting mixture. However, the presence of hydrogen is not a requirement, even if a

corresponding starting mixture should be described as containing hydrogen.

The oxidative coupling can also be carried out, for example, without the presence or formation of hydrogen.

As already mentioned at the outset, the oxidative coupling of methane is a process which is fundamentally known from the prior art. In the context of the present invention, known for the oxidative coupling of methane

Process concepts are used.

In embodiments of the present invention, (substantially) pure methane or natural gas or

Associated gas fractions of different purification stages up to the corresponding raw gas can be used. For example, natural gas can also be fractionated,

where, when an oxidative coupling is employed, methane in the oxidative

Coupling itself and higher hydrocarbons can preferably be performed in a post-catalytic steam cracking. Oxygen is particularly preferred as the oxidizing agent in a corresponding process. In principle, air or oxygen-enriched air can also be used, but lead to an

Nitrogen entry into the system. Separation at a suitable point in the process would in turn be comparatively expensive and would have to be carried out cryogenically.

In the embodiments of the present invention in which it is used, a dilution medium, preferably steam, but also, for example, carbon dioxide, can be used in the oxidative coupling, in particular to moderate the reaction temperatures. Carbon dioxide can also (partially) serve as an oxidizing agent. Compounds such as nitrogen, argon and helium, which are in principle also suitable as diluents, in turn require complex separation. With the current state of the technology, however, recirculated methane in particular serves as a diluent, of which only a comparatively small proportion is converted.

In configurations of the present invention, the oxidative coupling can be carried out in particular at an overpressure of 0 to 30 bar, preferably 0.5 to 5 bar, and a temperature of 500 to 1100° C., preferably 550 to 950° C. In principle, catalysts known from the technical literature can be used, see for example Keller and Bhasin, J. Catal. 1982, 73, 9, Hinsen and Baerns, Chem. Ztg. 1983, 107, 223, Kondratenko et al., Catal. May be. technol. 2017, 7, 366-381. Farrell et al., ACS Catalysis 6, 2016, 7, 4340, Labinger, Catal. Latvia 1 , 1988, 371, and Wang et al., Catalysis Today 2017, 285, 147.

In the context of the present invention, the conversion of methane in the oxidative coupling can in particular be more than 10%, preferably more than 20%, particularly preferably more than 30% and in particular up to 60% or 80%. The particular advantage of an embodiment of the present invention, in which an oxidative coupling is used, lies not primarily in the increased yield, but in the fact that, in addition to, in particular, a relatively high relative proportion of carbon monoxide in relation to ethylene in the product mixture of the oxidative coupling, ie the starting gas mixture used in this configuration, can be utilized.

patent claims

A method (100) for preparing a target compound, wherein a

Starting gas mixture is provided, the at least one olefin,

Contains carbon monoxide and carbon dioxide, and in which the olefin in at least a part of the starting gas mixture to obtain an aldehyde

is subjected to hydroformylation (2), wherein the olefin has a carbon chain having a first carbon number and the aldehyde has a carbon chain having a second carbon number one greater than the first

Carbon number, and wherein the carbon dioxide contained in the starting mixture is at least partly separated upstream and/or downstream of the hydroformylation, characterized in that at least the separated carbon dioxide is at least partly treated with methane to obtain carbon monoxide

Dry reforming (3) is subjected, and that in the

Carbon monoxide obtained by dry reforming is used at least in part in the hydroformylation (2).

2. The method as claimed in claim 1, in which the provision of the starting gas mixture comprises the oxidative coupling of a paraffin, in particular of methane.

3. The method (100) according to claim 1 or 2, wherein the aldehyde from the

hydroformulation is the target compound, or wherein the aldehyde is further converted to the target compound.

4. The method (100) of claim 3, wherein the aldehyde is hydrogenated to an alcohol having a carbon chain with the second carbon number.

5. The method (100) of claim 4, wherein the alcohol to an olefin

is dehydrated, which has a carbon chain with the second carbon number.

6. The method (100) according to any one of the preceding claims, wherein the first

carbon number is two and the second carbon number is three.

7. The method (100) according to claim 2, wherein the methane of the oxidative

is subjected to coupling, is at least partially separated from natural gas and in which at least one paraffin from the natural gas is transferred to a post-catalytic steam cracking step downstream of the oxidative coupling.

8. The method (100) according to any one of the preceding claims, in which the

Carbon monoxide obtained in dry reforming (3) in one

Product mixture is obtained, which also contains at least hydrogen.

9. The method (100) according to claim 8, wherein the product mixture from the

Dry reforming (3) is subjected to a water gas shift (4).

10. Process (100) according to claim 8 or 9, in which the product mixture from the dry reforming (3) and/or the product mixture from the water-gas shift (4) are at least partly fed unseparated to the hydroformylation (2).

1 1. Method (100) according to one of the preceding claims, in which the

Carbon monoxide and the olefin from the starting gas mixture are at least partially subjected to the hydroformylation (2) without prior separation.

12. The method (100) according to any one of the preceding claims, in which the

Starting gas mixture contains a paraffin, at least part of the paraffin passing through the hydroformylation (2) unreacted, being separated off downstream of the hydroformylation (2) and being used again in the preparation of the starting gas mixture.

13. The method (100) according to any one of the preceding claims, in which the

Starting mixture is compressed to a pressure level at which the carbon dioxide is separated off and the hydroformylation (2) is carried out, and at which the dry reforming (3) is carried out at a lower pressure level.

14. The method (100) according to any one of the preceding claims, downstream of the

Provision of the starting gas mixture and the dry reforming (3) is carried out completely non-cryogenically.

15. Facility for establishing a target connection that is set up for it

Provide starting gas mixture containing at least one olefin, carbon monoxide and carbon dioxide, and the olefin in at least a portion of the

To subject the starting gas mixture to obtain an aldehyde hydroformylation (2), wherein the olefin has a carbon chain with a first

carbon number and the aldehyde one carbon chain with a second

Has a carbon number that is one greater than the first carbon number, the plant also being set up to separate off at least some of the carbon dioxide contained in the starting mixture upstream and/or downstream of the hydroformylation, characterized by means set up to at least subjecting separated carbon dioxide at least in part to a dry reforming (3) with methane to obtain carbon monoxide, and using at least part of the carbon monoxide obtained in the dry reforming in the hydroformylation (2).