WO2021089183A1

WO2021089183A1 - Process and plant for producing monoethylene glycol

Info

Publication number: WO2021089183A1
Application number: PCT/EP2020/025478
Authority: WO
Inventors: Nicole SCHÖDEL; Andreas Peschel; Benjamin HENTSCHEL
Original assignee: Linde Gmbh
Priority date: 2019-11-05
Filing date: 2020-10-28
Publication date: 2021-05-14
Also published as: DE102019007672A1

Abstract

The invention relates to a process (100) and to a plant for producing monoethylene glycol (110), wherein, in a carbonylation step (21), carbon monoxide (102) is reacted with methyl nitrite (104) to form dimethyl oxalate (105) and nitrogen monoxide (106). Subsequently, in an esterification step (22), the nitrogen monoxide (106) is reacted with oxygen (103) and methanol (108) for conversion back to methyl nitrite (104). In a hydrogenation step (23), the dimethyl oxalate (105) is reacted with hydrogen (109) to form the monoethylene glycol (110). The carbon monoxide (102) and oxygen (107) are formed, in separated material flows, from carbon dioxide (101) in a carbon dioxide electrolysis step (10), the carbon monoxide (102) that is formed being fed to the carbonylation step (21). Oxygen (103), separated from the carbon monoxide (102), is fed to the esterification step (22).

Description

description

Process and plant for the production of monoethylene glycol

The invention relates to a method and a plant for the production of monoethylene glycol (MEG) from hydrogen, carbon monoxide and oxygen according to the preambles of the independent claims.

State of the art

Monoethylene glycol (MEG), an important raw material in the chemical industry, can be produced by adding water to ethylene oxide (EO):

H ₂ 0 + C ₂ H ₄ O - »HO-CH ₂ -CH ₂ -OH

Another possibility for the production of MEG is a generic method. In this case, synthesis gas can be used to provide the starting materials hydrogen and carbon monoxide. Oxygen can, for example, be obtained from the air or fed directly into the process in the form of air.

In principle, the following reactions take place in a simplified manner in such a method for producing MEG.

Carbon monoxide is reacted with methyl nitrite to form dimethyl oxalate and nitrogen monoxide. The latter is regenerated to methyl nitrite with oxygen and methanol, while the dimethyl oxalate is converted to MEG with hydrogen. This releases methanol, which in turn can be used in the regeneration of methyl nitrite:

2CO + 2NO2CH3 - H3C-OOC-COO-CH3 + 2NO 4NO + 0 ₂ + 4H ₃ COH-4NO ₂ CH ₃ + 2H ₂ 0 H3C-OOC-COO-CH3 + 4H ₂ -HO-CH2-CH2-OH + 2H ₃ COH The gross reaction equation is thus:

4CO + 0 ₂ + 8H ₂ - »2HO-CH ₂ -CH ₂ -OH + 2H ₂ 0

Synthesis gas is conventionally produced by steam reforming carbon-containing starting materials such as hard coal, crude oil, natural gas or biomass and can be separated into the pure gases carbon monoxide and hydrogen for use in a generic process.

Against this background, the present invention has the task of specifying a more sustainable and improved concept for the production of MEG.

Disclosure of the invention

According to the invention, this object is achieved in each case by a method and a system according to the independent claims.

According to the invention, a method for producing monoethylene glycol (MEG) is proposed, in which, in a carbonylation step, carbon monoxide is reacted with methyl nitrite to form dimethyl oxalate and nitrogen monoxide. In an esterification step, the nitrogen monoxide then reacts with oxygen and methanol again to form methyl nitrite. In a hydrogenation step, the dimethyl oxalate is reacted with hydrogen to form the monoethylene glycol.

According to the invention, carbon monoxide and oxygen are formed as separate material flows in a carbon dioxide electrolysis step from carbon dioxide, the carbon monoxide being fed to the carbonylation step and the oxygen to the esterification step.

By obtaining carbon monoxide and oxygen in the form of already separated material flows, a complex separation of the synthesis gas usually used can be avoided. In addition, carbon dioxide is used as the starting material, so that the process can have an overall negative CO2 footprint and is therefore unlikely to be hindered or regulated by legislation motivated by climate policy. The hydrogen used in the hydrogenation step is advantageously formed using a water electrolysis step, with additional oxygen being produced. As a result, all of the starting materials required in the process can be provided in a simple manner using similar technologies.

The oxygen required in the process according to the invention is advantageously taken from the oxygen streams formed in both electrolysis steps. These typically have different purities depending on the specific design of the respective electrolysis step, so that the purity of the oxygen required for the esterification step can be set.

The esterification step is preferably designed in two stages, so that in a first partial step the nitrogen monoxide is oxidized with the oxygen to form nitrous oxide, while in a second partial step the nitrous oxide is reacted with methanol with elimination of water to form methyl nitrite. This makes it possible to control the esterification step particularly precisely.

In particular, the methyl nitrite formed in the process can be returned to the carbonylation step and / or the water formed in the process to the water electrolysis step in order to achieve as closed material cycles as possible and small amounts used. This has a positive effect on the process economy.

It is also advantageous to return the methanol formed in the hydrogenation step to the esterification step, which in turn largely closes a material cycle.

The carbon monoxide is advantageously provided at a carbon monoxide pressure level between 0.1 MPa and 5 MPa, in particular between 0.5 MPa and 2 MPa. The oxygen is preferably provided at an oxygen pressure level between 0.1 MPa and 5 MPa, in particular between 0.5 MPa and 2 MPa. Furthermore, the hydrogen is advantageously provided at a hydrogen pressure level between 0.2 MPa and 10 MPa, in particular between 1 MPa and 5 MPa. This makes it particularly easy to design a system for carrying out the method according to the invention, since there are no pressures occur that are significantly below the natural atmospheric pressure, or particularly high pressures that would make a high-pressure-compatible design of a corresponding system necessary.

A pressure level is to be understood as a pressure within a pressure range, the limits of which differ by at most 1%, 2%, 5% or 10% from a mean value of the respective pressure range. A pressure level of, for example, 1 MPa is accordingly in a range from at least 900 kPa to a maximum of 1.1 MPa.

The water electrolysis step is preferably performed using one or more of a proton exchange membrane (PEM), an anion exchange membrane (AEM), alkaline electrolysis (AEL), high temperature alkaline electrolysis (HT AEL), and solid oxide electrolytic cell (SOEC). This means that the most economical alternative can be flexibly selected.

The carbon dioxide electrolysis step is advantageously carried out using a low temperature electrolysis in a temperature range from 20 ° C to 100 ° C, in particular 40 ° C to 80 ° C, and / or a high temperature electrolysis in a temperature range from 300 ° C to 1200 ° C, in particular 600 ° C to 1000 ° C, which in turn ensures the necessary flexibility to adapt to the existing requirements in terms of process parameters and product quality.

Another aspect of the invention relates to a system which is set up to carry out a method in accordance with the above explanations. According to the invention, this plant comprises a carbonylation unit, an esterification unit, a hydrogenation unit and a carbon dioxide electrolysis unit. The plant is also set up to feed carbon monoxide generated by the carbon dioxide electrolysis unit to the carbonylation unit, to feed dimethyl oxalate and hydrogen formable in the latter to the hydrogenation unit and to feed oxygen and nitrogen monoxide available in the carbonylation unit to the esterification unit. In order to explain the steps for the implementation of which the system with its subunits is preferably designed, express reference is made to the above statements with regard to the advantages and features of the embodiments of the manufacturing method. For the sake of clarity, these are not repeated in detail here, but apply mutatis mutandis to embodiments of the system in a corresponding manner.

The system is also advantageously set up to build up an inert gas component in the carbonylation unit and the esterification unit, it being possible for the inert gas component to be formed in particular using the carbon dioxide. The proportion of inert gas is advantageously used to regulate the temperature in the carbonylation reactor and to avoid an explosive atmosphere due to an excessively high methyl nitrite concentration. So that the proportion of inert gas does not build up indefinitely, a certain amount can advantageously be continuously withdrawn (purged). This can be done via a carbon dioxide-selective membrane or pressure swing adsorption.

Refinements of the invention

In the following, further advantages, aspects and embodiments of the invention are explained in more detail with reference to the attached FIG. 1, which schematically illustrates a preferred embodiment of the method according to the invention in the form of a block diagram.

The method 100 shown in FIG. 1 is divided into five important steps: a carbon dioxide electrolysis step 10, a water electrolysis step 30, a carbonylation step 21, an esterification step 22 and a hydrogenation step 23.

In the carbon dioxide electrolysis step 10, carbon dioxide 101 is electrolyzed into carbon monoxide 102 and oxygen 107. As mentioned, this can be done using a high-temperature electrolysis, such as a solid oxide electrolysis cell (SOEC), which is operated, for example, in a temperature range from 600.degree. C. to 800.degree. C., for example at 750.degree. A low-temperature electrolysis can also be used in the carbon dioxide electrolysis step 10, in particular using an electrolysis unit with a gas diffusion electrode (GDE), as described in more detail elsewhere.

Regardless of the electrolysis concept used, the oxygen 107 is formed on an anode side and the carbon monoxide 102 is formed on a cathode side according to the following generalized reaction equation:

C0 ₂ - CO + ^_1/2 0 ₂

The carbon monoxide 102 can optionally also have a proportion of carbon dioxide which is fed to the carbonylation step 21 together with the carbon monoxide 102.

In the carbonylation step 21, the carbon monoxide 102 that was formed in the carbon dioxide electrolysis step 10 is converted together with methyl nitrite 104 to form dimethyl oxalate 105 and nitrogen monoxide 106.

The dimethyl oxalate 105 formed in the carbonylation step 21 is then subjected to the hydrogenation step 23 in which it is reacted with hydrogen 109 to form monoethylene glycol 110. In the exemplary embodiment shown, the hydrogen 109 used here is generated from water 111 in the water electrolysis step 30, with oxygen 112 also being formed.

In the hydrogenation step 23, methanol 108 is also released, which, together with the nitrogen monoxide 106 and oxygen 103 formed in the carbonylation step 21, is converted in the esterification step 22 to methyl nitrite 104, which in turn is returned to the carbonylation step 21. As a result, both the methyl nitrite 104 and the methanol 108 are effectively circulated, as a result of which only very small amounts have to be fed freshly into the method 100 in order to compensate for any losses that may occur due to secondary reactions, aging processes and leakages. In the example shown, the oxygen 103 used in the esterification step 22 is formed using the oxygen 107 formed in the carbon dioxide electrolysis step 10 and / or the oxygen 112 generated in the water electrolysis step 30. These two oxygen streams 112, 107 are generally obtained in a purity which is sufficient for the esterification step 22. Thus, the process economy is particularly positively influenced by such a use of by-products that occur anyway.

Overall, in the method 100 shown, the monoethylene glycol 110 is thus effectively formed from the carbon dioxide 101 and the water 111, while all other substances used are conducted in closed cycles. In this way, the objectives of the invention mentioned at the beginning can be achieved in a particularly advantageous manner, since no fossil raw materials are used and net carbon dioxide is consumed. Too much oxygen 107, 112 generated in the method 100 can either be marketed as an additional product of value or transferred to further processes or released into the natural atmosphere.

As a rule, in none of the steps does a complete conversion of the respective educts into the respective product take place in a single run. For this reason, residual fractions of the starting material and any by-products that may be present are typically at least partially separated off from a crude product formed in each case and, if appropriate, returned to the step preceding the separation in each case. This separation is not shown in FIG. 1 for the sake of clarity. This separation can also be omitted at certain points if the components contained in the respective crude product do not interfere with the subsequent step. In such a case, the corresponding components are advantageously removed from the crude product during a separation which takes place further downstream, so that at the end of the process 100 a monoethylene glycol product 110 corresponding to the respective requirements is obtained. The separation steps can preferably take place at points in the process at which such a separation can be carried out particularly easily due to the differences in the physical and / or chemical properties of the respective mixture components. Suitable separation processes can include, for example, membrane separation processes, adsorption processes such as pressure swing adsorption, in particular vacuum pressure swing adsorption, temperature swing adsorption or absorption processes, for example chemical or physical washing or precipitation formation.

It goes without saying that to control material flows, pressures, temperatures and, if necessary, further process parameters, further system components may be necessary which are not mentioned and explained in detail in the above description. These can include, for example, valves, compressors, pumps, heat exchangers, heating devices, coolers and / or pipe insulations.

The examples described above, with their respective combinations of features, merely represent illustrations and exemplary embodiments and are not to be understood as an exhaustive list of combinations of features possible within the scope of the invention. Rather, many of the features can also be advantageous in other combinations or on their own. The selection of a specific embodiment is based, for example, on the respective requirements for the purity of the monoethylene glycol 110 produced as well as economic considerations, which include in particular the energy and investment costs for operating a method according to the invention or for producing and commissioning a system set up for this purpose. Possible combinations of features encompassed by the invention in its entirety can be found in the patent claims belonging to this disclosure.

Water that is formed in the esterification step 22 can at least partially be returned as the water 111 to the water electrolysis step 30, although this is not illustrated separately here for the sake of clarity.

Claims

1. Process (100) for the production of monoethylene glycol (110),

- in which in a carbonylation step (21) carbon monoxide (102) is reacted with methyl nitrite (104) to form dimethyl oxalate (105) and nitrogen monoxide (106),

- in which, in an esterification step (22), the nitrogen monoxide (106) is reacted with oxygen (103) and methanol (108) to form methyl nitrite (104), and

- in which, in a hydrogenation step (23), the dimethyl oxalate (105) is reacted with hydrogen (109) to form the monoethylene glycol (110), characterized in that

- that the carbon monoxide (102) and oxygen (107) are formed in separate material flows in a carbon dioxide electrolysis step (10) from carbon dioxide (101),

- wherein the carbon monoxide (102) formed in the carbon dioxide electrolysis step (10) is fed to the carbonylation step (21) and oxygen (103) is fed to the esterification step (22) separately from the carbon monoxide (102) formed in the carbon dioxide electrolysis step (10).

2. The method (100) according to claim 1, wherein the hydrogen (109) and oxygen (112) are formed from water (111) in a water electrolysis step (30), the hydrogen (109) being fed to the hydrogenation step (23).

3. The method (100) according to claim 1 or 2, wherein the oxygen (103) which is fed to the esterification step (22) using the oxygen (112) formed in the water electrolysis step (30) and / or in the Carbon dioxide electrolysis step oxygen formed (107) is formed.

4. The method (100) according to any one of the preceding claims, wherein in the esterification step (22) the nitrogen monoxide is oxidized with oxygen to dinitrogen trioxide, which is then reacted with methanol with elimination of water to methyl nitrite.

5. The method (100) according to any one of the preceding claims, wherein the methanol formed in the hydrogenation step (23) is at least partially recycled as the methanol (108) to the esterification step (22).

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

- The carbon monoxide (102) at a carbon monoxide pressure level selected from a pressure range of 0.1 MPa to 5 MPa, in particular 0.5 MPa to 2 MPa;

- The oxygen (103) at an oxygen pressure level selected from a pressure range of 0.1 MPa to 5 MPa, in particular 0.5 MPa to 2 MPa; and or

the hydrogen at a hydrogen pressure level selected from a pressure range of 0.2 MPa to 10 MPa, in particular 1 MPa to 5 MPa; provided.

7. The method (100) according to any one of the preceding claims, wherein water that is formed in the esterification step (22) is at least partially returned as the water (111) to the water electrolysis step (30).

8. The method (100) according to any one of the preceding claims, wherein the water electrolysis step (30) using one or more of a proton exchange membrane (PEM), an anion exchange membrane (AEM), an alkaline electrolysis (AEL), an alkaline high-temperature electrolysis (HT AEL) and / or a solid oxide electrolyte cell (SOEC) is carried out.

9. The method (100) according to any one of the preceding claims, wherein the carbon dioxide electrolysis step (10) using a low temperature electrolysis in a temperature range of 10 ° C to 100 ° C, in particular 40 ° C to 80 ° C, and / or a high temperature electrolysis in one Temperature range from 300 ° C to 1200 ° C, in particular from 600 ° C to 1000 ° C, is carried out.

10. Plant for the production of monoethylene glycol (110), with

- a carbonylation unit, which is set up to convert carbon monoxide (102) with methyl nitrite (104) to dimethyl oxalate (105) and nitrogen monoxide (106), - an esterification unit which is used to convert the nitrogen monoxide (106) with

Oxygen (103) and methanol (108) is set up to methyl nitrite (104), and

- A hydrogenation device which is set up to convert the dimethyl oxalate (105) with hydrogen (109) to form the monoethylene glycol (110), characterized by a carbon dioxide electrolysis unit which is set up for this purpose

Carbon dioxide (101) to form the carbon monoxide (102) and oxygen (107) in separate material flows; and

- Means which are set up to supply the carbon monoxide (102) to the carbonylation unit; and supplying oxygen (103) separately from the carbon monoxide (102) to the esterification unit.

11. Plant according to claim 10, further set up to carry out all the steps of a method according to one of claims 1 to 9.

12. Plant according to claim 10 or 11 further comprising means which are set up to build up an inert gas component in the carbonylation unit and the esterification unit, the inert gas component being formed in particular using the carbon dioxide (101).