WO2024056652A1

WO2024056652A1 - Heat-integrated method for producing c2-c4 olefins

Info

Publication number: WO2024056652A1
Application number: PCT/EP2023/074996
Authority: WO
Inventors: Andre BADER; Robert Peter Michael FRANZ; Paul-Vinzent STROBEL
Original assignee: Basf Se
Priority date: 2022-09-12
Filing date: 2023-09-12
Publication date: 2024-03-21

Abstract

The invention relates to a method for producing C2-C4 olefins from dimethyl ether and optionally methanol, having the steps of: A) providing a dimethyl ether-containing flow A; B) mixing at least one part of the flow A with at least one hydrocarbon return flow R, which contains C2-C6 hydrocarbons, and with a water vapor flow G2, a feed flow B being obtained; C) heating the feed flow B to a temperature ranging from 430 to 500 °C in one or more heat exchangers and feeding same to an olefin fixed-bed reactor, wherein the heating process can also be carried out before individual sub-flows are mixed in order to form the feed flow B in step B); D) catalytically converting the feed flow B at a temperature ranging from 430 to 520 °C in order to form a product gas flow D, which contains C2-C4 olefins, additional C2-C6 hydrocarbons, methanol, and water vapor; E) cooling the product gas flow D to a temperature ranging from 170 to 220 °C in one or more heat exchangers by exchanging heat with the feed gas flow B; F) further cooling the product gas flow D to a temperature ranging from 35 to 65 °C by bringing the product gas flow into contact with at least one water-containing quenching circuit flow K, wherein water and methanol are condensed out of the product gas flow, and a hydrocarbon product gas flow F which is depleted of water and methanol is obtained; G) separating at least one sub-flow G1 of the at least one water-containing quenching circuit flow K and heating and evaporating the sub-flow G1 in one or more heat exchangers by exchanging heat with medium-pressure water vapor or heating and evaporating the sub-flow G1 by means of an electric heating process, a water vapor flow G2 being obtained, and feeding the water vapor flow G2 to step B); and H) separating one or more C2-C4 olefin-containing product flows P and obtaining at least one hydrocarbon return flow R, which contains C2-C6 hydrocarbons, from the hydrocarbon product gas flow F and returning same to step B).

Description

Heat-integrated process for the production of C2-C4 olefins

Description

The invention relates to a heat-integrated process for producing C2- _C4 olefins from dimethyl ether and optionally methanol.

It is known to produce propylene by reacting a methanol/dimethyl ether mixture in a fixed bed reactor (methanol-to-propylene, MTP reactor). Known fixed bed reactors are operated with zeolite catalysts at temperatures of approximately 480°C. For this it is necessary to heat the methanol/DME-containing educt gas stream to high temperatures before entering the reactor.

L. Jiang et al., Chinese Journal of Chemical Engineering 26 (2018), 2102 - 2111 describe a process for producing propylene from methanol, in which methanol is first converted into dimethyl ether (DME) and then the product mixture is converted into propylene and other products becomes. With reference to Figure 8 of this publication, the process is described as follows: Methanol is preheated, evaporated and further heated by heat exchange with the product gas of the DME reactor in a heat exchanger. The methanol vapor is fed into the DME reactor at a temperature of 270°C. A first partial stream of the product gas from the DME reactor is then cooled to a temperature of 150 ° C by heat exchange with a hydrocarbon recycle stream, cold methanol and circulating cooling water, and the gas/liquid mixture formed is separated in a phase separator. The gas phase is reheated while the liquid phase is further cooled, and the gas and liquid phases are fed into the individual trays of the propylene fixed bed reactor (MTP reactor). Alternatively, only methanol can be fed into the individual trays of the MTP reactor. The second partial stream of the product gas from the DME reactor is mixed with the hydrocarbon recycle stream and water vapor, heated with a burner to a temperature of approximately 460 ° C and fed into the propylene reactor, in which practically all of the methanol and DME are converted into propylene and other hydrocarbons can be implemented.

A disadvantage of the process described is that a large part of the amount of heat required to heat the educt streams fed into the propylene reactor is provided by burning natural gas or other fossil hydrocarbons in a burner. This has a very negative impact on the CO2 balance of the entire process. However, against the background of intensifying anthropogenic climate change, industrial production processes are increasingly being sought that emit little or, better yet, no CO2 of fossil origin into the atmosphere. The object of the invention is to provide a heat-integrated process for the production of C2- _C4 olefins starting from dimethyl ether, in which the provision of process heat by burning non-process fossil hydrocarbons in stationary operation can be dispensed with.

The problem is solved by a process for producing C2-C4 olefins from dimethyl ether and, if appropriate, methanol with the steps:

A) providing a stream A containing dimethyl ether;

B) mixing at least a portion of the stream A with at least one hydrocarbon recycle stream R containing C2-C6 hydrocarbons and a steam stream G2, thereby obtaining a feed stream B;

C) Heating the feed stream B in one or more heat exchangers to a temperature in the range of 430 to 500 ° C and feeding it into an olefin fixed bed reactor, whereby the heating can also take place before mixing individual partial streams to form the feed stream B in step B). ;

D) catalytic conversion of the feed stream B at a temperature in the range from 430 to 520 ° C to give a product gas stream D containing C2- _C4 olefins, further C2-C6 hydrocarbons, methanol and water vapor;

E) cooling the product gas stream D in one or more heat exchangers to a temperature in the range from 170 to 220 ° C by heat exchange with the feed gas stream B;

F) further cooling of the product gas stream D to a temperature in the range from 35 to 65 ° C by bringing it into contact with at least one water-containing quench cycle stream K, whereby water and methanol are condensed out and a hydrocarbon product gas stream F depleted in water and methanol is obtained becomes;

G) Separation of at least one partial stream G1 of the at least one water-containing quench circuit stream K and heating and evaporation of the partial stream G1 in one or more heat exchangers by heat exchange with medium-pressure steam, or heating and evaporation of the partial stream G1 by electrical heating, obtaining a steam stream G2 is, and feeding the steam stream G2 in step B);

H) separation of one or more product streams P containing C2- _C4 olefins and recovery of at least one hydrocarbon recycle stream R containing C2-Ce hydrocarbons from the hydrocarbon product gas stream F and recycling to step B).

In one embodiment of the method according to the invention, in step A), a stream A consisting essentially of DME (>90% by weight of DME) is fed into the process and divided into two partial streams. The first partial stream A-1 comprises a maximum of 80% by weight of stream A and is used as described in step B). The second partial stream is mixed with a partial stream G3 of the water-containing quench circuit stream mentioned in step G) and, as stream A-2, is fed into one or more individual trays of the olefin fixed-bed reactor without further heating of step C). It is also possible to operate the olefin fixed bed reactor isothermally. Isothermal operation can take place, for example, in the manner described in WO2017/102096 A1. Heat transfer surfaces can be installed in the olefin fixed bed reactor, which are operated, for example, with liquid salt or high-pressure steam as a heat transfer medium. As the heat transfer medium flows through the heat transfer surfaces in the reactor, the resulting reaction heat is removed from the reactor and the reactor is therefore operated isothermally.

In a preferred embodiment of the method according to the invention, the step comprises

A) feeding a methanol-containing feed gas stream A1 into a dimethyl ether fixed-bed reactor and the catalytic conversion of methanol to dimethyl ether, whereby a product gas stream containing dimethyl ether, methanol and water vapor is obtained. If stream A1 contains ethanol, product stream A will also contain ethanol and ethylene in addition to dimethyl ether, methanol and steam.

C2- _C4 olefins are ethylene, propylene, 1-butene, 2-butenes and isobutene. Ethylene and/or propylene are preferably produced using the process according to the invention.

In a preferred embodiment, the method according to the invention thus comprises the steps:

A) feeding a methanol-containing feed stream A1 into a dimethyl ether fixed-bed reactor and catalytic conversion of methanol to dimethyl ether, whereby a product stream A containing dimethyl ether, methanol and steam is obtained;

B) mixing at least a portion of the product stream A with at least one hydrocarbon recycle stream R containing C2-C6 hydrocarbons and a steam stream G2, whereby a second feed stream B is obtained;

C) heating the second feed stream B in one or more heat exchangers to a temperature in the range of 430 to 500 ° C and feeding it into an olefin fixed bed reactor, the heating also being able to take place before mixing individual partial streams to form the feed stream B in step B);

D) catalytic conversion of the feed stream B at a temperature in the range from 430 to 520 ° C to a product gas stream D containing ethylene, propylene, further C2-C6 hydrocarbons, methanol and water vapor;

E) cooling the product gas stream D in one or more heat exchangers to a temperature in the range from 170 to 220 ° C by heat exchange with the feed stream B;

F) further cooling of the product gas stream D to a temperature in the range from 35 to 65 ° C by bringing it into contact with at least one water-containing quench cycle stream K, whereby water and methanol are condensed out and a hydrocarbon product gas stream F depleted in water and methanol is obtained ;

G) Separation of at least one partial stream G1 of the at least one water-containing quench cycle stream K and heating and evaporation of the partial stream G1 in one or several heat exchangers by heat exchange with medium-pressure steam, or heating and evaporating the partial stream G1 by electrical heating, whereby a steam stream G2 is obtained, and feeding the steam stream G2 in step B);

H) separation of one or more product streams P containing ethylene and/or propylene and recovery of at least one hydrocarbon recycle stream R containing C2-Ce hydrocarbons from the hydrocarbon product gas stream F and recycling to step B).

In step A), a methanol-containing feed stream A1 is preferably fed into a dimethyl ether fixed-bed reactor and methanol is catalytically converted to dimethyl ether, giving a product stream A containing dimethyl ether, methanol and steam.

A methanol-containing feed stream A1, which preferably comes from an upstream methanol synthesis plant, is evaporated and heated to a temperature of generally 250 to 300 ° C, for example 275 ° C, and fed into the dimethyl ether fixed bed reactor. Gamma aluminum oxide is generally used as the catalyst. The reaction temperature is generally 250 to 400 ° C, the pressure is generally 1 to 25 bar, for example 4 bar. The first product gas stream leaving the dimethyl ether fixed bed reactor has a temperature of generally 350 to 400 ° C, for example 370 ° C. The methanol conversion is generally 50 to 90%, preferably 65 to 85%, for example 75%. The product gas stream A is cooled by heat exchange with the methanol-containing feed stream A1. After the heat exchange, the first product gas stream has a temperature of generally 180 to 250 ° C.

In a step B), at least a portion of this stream A is mixed with a hydrocarbon recycle stream containing C2-C6 hydrocarbons and a water vapor stream G2, whereby a feed gas stream B is obtained. In general, this portion of stream A is at least 50% by weight and preferably up to 80% by weight. A further part A-2 of stream A, preferably at least 20% by weight, can be fed directly to one or more trays of the olefin fixed bed reactor. If this part of stream A comes from an upstream dimethyl ether reactor, it is generally cooled before being fed into the trays of the olefin fixed bed reactor, preferably to a temperature in the range from 30 to 60 ° C. This partial stream A-2 is preferably fed into the reactor in liquid form.

Cooling by partial stream A-2 can also be omitted if the olefin fixed bed reactor is operated and cooled isothermally. Isothermal operation can take place, for example, in the manner described in WO2017/102096 A1. Heat transfer surfaces can be installed in the olefin fixed bed reactor, which are operated, for example, with liquid salt or high-pressure steam as a heat transfer medium. As the heat transfer medium flows through the heat transfer surfaces in the reactor, the resulting reaction heat is removed from the reactor and the reactor is therefore operated isothermally. To set the To achieve the desired product distribution in the product gas stream D, a partial stream A-2 can also be fed to an intermediate stage of the olefin fixed bed reactor.

In a further embodiment, a stream containing methanol is fed directly to one or more trays of the olefin fixed bed reactor. Preferably, a portion of the methanol-containing first feed stream A1, which comes, for example, from an upstream methanol synthesis plant, is fed directly into the olefin fixed-bed reactor. This portion of the methanol-containing feed stream A1 can amount to up to 60% by weight of the total feed stream A1.

The hydrocarbon recycle stream R, which comes from the separation of the C2-C4 olefins, generally contains C4-C6 hydrocarbons. Depending on whether ethylene, propylene or butenes are obtained as a product of value in step H), the hydrocarbon recycle stream can R also contain ethylene, propylene and/or butenes. If the amount of C2-C4 olefin obtained as a product in step H) contains, for example, at least 85% by weight of propylene, stream R consists of at least 50% by weight of _C4 -C6 hydrocarbons. Before mixing, the hydrocarbon recycle stream R generally has a temperature in the range from 100 to 175 ° C, preferably in the range from 130 to 160 ° C. The hydrocarbon recycle stream R is preferably heated by heat exchange with medium-pressure steam and has a temperature of generally 30 to 100 ° C, preferably 50 to 80 ° C, before heating.

The product stream A from the dimethyl ether fixed bed reactor is further mixed with a steam stream G2. The steam stream G2 generally has a temperature in the range from 100 to 200 ° C, preferably in the range from 100 to 150 ° C. According to the invention, this steam stream is heated by heat exchange with medium-pressure steam.

The feed stream B thus obtained generally contains 15 to 50% by weight, preferably 20 to 40% by weight, of water vapor. It generally also contains 5 to 10% by weight of methanol, 10 to 20% by weight of dimethyl ether and 25 to 50% by weight of C2-C6 hydrocarbons.

In a step C), the feed stream B is heated in one or more heat exchangers to a temperature in the range of 430 to 500 ° C and fed into an olefin fixed-bed reactor. The heating can also take place before mixing individual partial streams in step B).

In general, the feed stream B has a temperature in the range from 430 to 500 ° C, for example 470 ° C, when fed into the olefin fixed bed reactor. The feed stream B is heated to this temperature by heat exchange with the (second) product gas stream D of the olefin fixed bed reactor. By heating the water vapor stream G1 according to the invention by heat exchange with medium-pressure steam, the feed stream B can be heated by heat exchange with the (second) product gas stream D Temperatures of 430 to 500°C can be achieved without the need for additional heating with a burner in stationary operation. The small temperature differences between the two gas streams B and D increase the required heat transfer area. In systems with high production capacity, this can lead to disproportionately large heat exchangers. In such cases, the final part of the heating of the feed stream B can also be carried out with an electrical heat exchanger, which increases the temperature difference in the heat exchangers between streams B and D. This reduces the required heat transfer area to an implementable level. As long as the electrical power is generated without burning fossil fuels, the heating of electricity B continues to occur without CO2 emissions.

In one embodiment of the method according to the invention, the second feed gas stream B is heated in step C) in part by means of an electrical heat exchanger.

This is followed in step D) by the catalytic conversion in the olefin fixed bed reactor to give a product gas stream D containing ethylene, propylene, further C2-C6 hydrocarbons, methanol and water vapor. The reaction generally takes place on a zeolite catalyst, preferably on a catalyst based on a ZSM-5 zeolite. The reaction temperature is generally 430 to 500°C, preferably 460 to 480°C. The pressure is generally 1.3 to 4 bar. The second product gas stream D obtained is preferably composed as follows: 1 to 15% by weight of ethylene, 1 to 15% by weight of propylene, 35 to 70% by weight of water, 20 to 65% by weight of C2-C6 hydrocarbons , as well as C6 ⁺ hydrocarbons and 0.1 to 1.5% by weight of methanol and DME.

The olefin fixed bed reactor is generally designed as a tray reactor. The number of trays is preferably 4 to 6. In one embodiment, a total of up to 50% by weight of the gas stream A is fed directly to one or more trays of the olefin fixed bed reactor, preferably to all trays of the olefin fixed bed reactor. In a further embodiment, a methanol-containing stream is fed directly to one or more trays of the olefin fixed-bed reactor, preferably to all trays of the olefin fixed-bed reactor.

The (second) product gas stream D has a temperature of generally 430 to 520 ° C, preferably 460 to 480 ° C, when it leaves the reactor.

In a step E), the product gas stream D is cooled in one or more heat exchangers to a temperature in the range from 160 to 220 ° C by heat exchange with the feed gas stream B. After this cooling step, the temperature of the (second) product gas stream D is generally 160 to 220 ° C, preferably 170 to 210 ° C, for example 190 ° C.

In a step F), the product gas stream D is further cooled to a temperature in the range from 35 to 60 ° C by bringing it into contact with one or more water-containing quench cycle streams, whereby water and methanol are condensed out and added Water and methanol-depleted hydrocarbon product gas stream F is obtained. The hydrocarbon product gas stream F thus obtained essentially contains ethylene, propylene and other C2-C6 hydrocarbons.

In a step G), part of the water of the at least one quench circuit stream K is separated off and, according to the invention, this partial stream G1 is heated and evaporated in one or more heat exchangers by heat exchange with medium-pressure steam, or this partial stream G1 is heated and evaporated by electrical heating, whereby a heated water vapor stream G2 is obtained. This heated water vapor stream G2 is mixed in step B) with the first product stream A (or the feed stream A) originating from the dimethyl ether fixed bed reactor.

In general, the water-containing quench circuit stream in step G) is heated to at least 50%, based on the amount of heat supplied, by heat exchange with medium-pressure steam or via electrical heating. In addition, the partial stream G1 of the water-containing quench cycle stream in step G) can be additionally heated and evaporated by heat exchange with the product gas stream D.

Before heating, the separated partial stream G1 of the quench circulation stream K is liquid and generally has a temperature in the range from 70 to 100 ° C. After heating and evaporation, the steam stream G1 has a temperature in the range of 100 to 150 ° C, preferably 120 to 140 ° C, and correspondingly a pressure of 1 to 6 bar, preferably 2 to 4 bar.

In a first embodiment, the water stream G1 taken from the quench circuit is heated by heat exchange with medium-pressure steam. Medium-pressure steam in the context of the present invention is steam with a temperature of at least 150 ° C and a pressure of at least 5 bar, preferably a temperature in the range of 150 to 250 ° C, preferably 150 to 200 ° C and correspondingly a pressure in the range from 5 to 17 bar, preferably 5 to 11 bar.

All pressures given are absolute pressures.

The medium-pressure steam stream used in step G) preferably comes from a methanol synthesis upstream of step A) and/or from a synthesis gas production upstream of this methanol synthesis. The medium-pressure steam stream can come from spatially adjacent, separate production plants.

In a second embodiment, the water stream G1 taken from the quench circuit is heated by electrical heating. Electrical heating can take place, for example, in a boiler with built-in electric heating elements. According to the invention, the electrical energy supplied to the electrical heating is predominantly generated regeneratively, i.e. without burning fossil fuels. The electrical energy supplied to the electrical heating is therefore largely provided without any climate-damaging CC>2 emissions.

The medium-pressure steam can also be generated by electrical heating. Electrical heating can take place, for example, in a boiler with built-in electric heating elements.

In a step H), one or more product streams P containing C2-C4 olefins are separated from the hydrocarbon product gas stream F and at least one recycle stream R containing C2-Ce hydrocarbons is obtained. The total recirculation stream R is generally composed of several individual recirculation streams. In general, the entire recycle stream R containing C2-C6 hydrocarbons essentially contains, that is to say >95% by weight, C2-C6 hydrocarbons.

The hydrocarbon recycle stream R containing C2-C6 hydrocarbons can also be heated by heat exchange with medium-pressure steam.

The hydrocarbon recycle stream R containing C2-C6 hydrocarbons can be heated by heat exchange with the product gas stream D before mixing with the stream A to form the feed stream B.

In general, step H) includes steps H1) to H7):

H1) compression of the hydrocarbon product gas stream F, obtaining a liquid hydrocarbon stream H11 containing propylene, C4, C5 and C6 ⁺ hydrocarbons and a gaseous hydrocarbon stream H12 containing ethane, ethene and propylene;

H2) separation of water from the liquid hydrocarbon stream H11 by phase separation, thereby obtaining a liquid hydrocarbon stream H21;

H3) separating a propylene-containing stream H31 from the liquid hydrocarbon stream H21, obtaining a stream H32 containing C ₄ , C5 and C6 ⁺ hydrocarbons; or separating a stream H31 containing propylene and C4 hydrocarbons, obtaining a stream H32 containing C4, C5 and C6 ⁺ hydrocarbons;

H4) separating a stream H41 containing C6 ⁺ hydrocarbons from the stream H32 containing C4, C5 and C6 ⁺ hydrocarbons, whereby a stream H42 containing C ₄ , C5 and Cß hydrocarbons is obtained; Optionally, stream H41 contains aromatic Ce hydrocarbons and stream H42 contains aliphatic Ce hydrocarbons; H5) separation of a propylene-containing stream H51 from the ethane, ethene and propylene-containing gaseous hydrocarbon stream H12, whereby a ethane and ethene-containing stream H52 is obtained;

H6) separation of a butene-containing stream H61 from the C4, C5 and Ce hydrocarbon-containing stream H42, whereby a C5 and Ce hydrocarbon-containing stream H62 is obtained; and/or separating a propylene-containing stream H63 from the stream H31, obtaining a butene-containing stream H64;

H7) Obtaining at least one recycle stream R from one or more of the streams selected from the stream H42 containing _C4 , C5 and Cß hydrocarbons, the stream H62 containing C5 and Ce hydrocarbons, the stream H31 containing propylene, the stream H31 containing propylene Stream H51, the propylene-containing stream H63, the butene-containing stream H61, the butene-containing stream H64 and the ethane and ethene-containing stream H52.

Steps H3), H4), H5) and H6) are carried out in conventional distillation devices. In principle, the devices known to those skilled in the art for such separation tasks can be used as distillation devices. In addition to the actual column body with internals, the distillation column, as usual, also contains a top condenser and a bottom evaporator. The column body can, for example, be equipped with packings, packings or trays. The distillation devices can be designed and operated with the general knowledge of those skilled in the art.

The process according to the invention for producing C2- _C4 olefins from dimethyl ether and optionally methanol preferably follows a process for producing methanol, the process for producing methanol comprising the following steps:

(a) a synthesis gas (II) containing carbon monoxide, carbon dioxide and hydrogen is produced from a carbon-containing feedstock (I) in a synthesis gas production unit;

(b) the synthesis gas (II) from stage (a) is fed to a methanol synthesis unit and at a temperature of 150 to 300 ° C and a pressure of 5 to 10 MPa abs in the presence of a methanol synthesis catalyst to form a methanol, water, Reaction mixture containing carbon monoxide, carbon dioxide, hydrogen, dimethyl ether and methane is implemented, from which a raw methanol stream (III) enriched with methanol and water is condensed out, and the raw methanol stream (III) and a gaseous stream containing carbon monoxide, carbon dioxide, hydrogen and methane ( IV) removed from the methanol synthesis unit;

(c) the raw methanol stream (III) from stage (b) is expanded in an expansion unit to a pressure of 0.1 to 2 MPa abs and an expansion gas (V) containing carbon dioxide and methane and a degassed raw material enriched with methanol and water - Methanol stream (VI) obtained; (d) a low boiler stream (VII) containing carbon dioxide and dimethyl ether is distilled off from the degassed crude methanol stream (VI) from stage (c) in a distillation device and a bottom stream (VIII) enriched with methanol and water is obtained; and

(e) optionally, a water-containing high boiler stream (IX) is separated from the bottom stream (VIII) from stage (d) in a further distillation device and methanol is obtained by distillation as stream (X). Step (e) can also be omitted since anhydrous methanol is not required.

The bottom stream (VIII) enriched with methanol and water or, if appropriate, the pure methanol stream (X) can be used in the process according to the invention.

The medium-pressure steam stream used according to the invention in step G) of the propylene production preferably comes from the synthesis gas production unit of step (a) of the methanol production and / or the methanol synthesis unit of step (b) of the methanol production.

The process for producing methanol preferably also includes the following steps:

(f) the valuable components carbon monoxide, carbon dioxide, dimethyl ether and methane of the streams (IV) and of at least one of the two streams (V) and (VII) are fed to a combustion unit and therein with the supply of an oxygen-containing gas (XI), which has an oxygen content from 30 to 100% by volume, burned and flue gas containing carbon dioxide (XII) is formed;

(g) a carbon dioxide-enriched stream (XIV) is separated from the carbon dioxide-containing flue gas (XII) from stage (f) in a carbon dioxide recovery unit to form an exhaust gas stream (XIII); and

(h) the stream (XIV) from stage (g) separated in the carbon dioxide recovery unit and enriched with carbon dioxide is recycled to the synthesis gas production unit of stage (a) and/or to the methanol synthesis unit of stage (b).

Such a method, comprising steps (f), (g) and (h), is described in WO 2020/048809 A1.

The medium-pressure steam stream used in step G) of the production of C2- _C4 olefins preferably comes from the synthesis gas production unit of step (a) of the methanol production and/or the methanol synthesis unit of step (b) of the methanol production . In this process, a wide variety of carbon-containing feedstocks can be used as feedstocks producing synthesis gas, regardless of whether they are in solid, liquid or gaseous form, and regardless of their chemical nature. For example, both coal and hydrocarbons as well as compounds containing carbon and hydrogen can be used to produce synthesis gas. Natural gas, biogas, coal, wood, plastics, petroleum, bionaphtha or hydrocarbon-containing streams from crude oil or natural gas processing, from chemical production processes, from renewable raw materials or from plastic recycling are mentioned as preferred carbon-containing feedstocks. In the case of coal or wood, synthesis gas is produced, for example, through a gasification process, also called coal gasification or wood gasification. Suitable input materials from crude oil or natural gas processing include naphtha, LPG, gasoline, heavy oil or vacuum residue. Hydrocarbon-containing streams from chemical production processes are, for example, hydrocarbon-containing streams that arise as by-products and can also be used as a feedstock for the production of synthesis gas instead of purely thermal utilization.

The use of methane-containing streams and very particularly preferred natural gas or biogas is particularly preferred. It is possible and even advantageous to also supply carbon dioxide present in the natural gas and especially in the biogas to the synthesis gas production unit.

A synthesis gas (II) containing carbon monoxide, carbon dioxide and hydrogen is first produced from the carbon-containing feedstock (I) in the synthesis gas production unit. Natural gas usually contains 75 to 100 vol% methane. In addition to methane, the higher hydrocarbons ethane, propane, butane and also ethene are mentioned as accompanying substances. Biogas usually contains 40 to 75% by volume of methane and essentially carbon dioxide, water, nitrogen and oxygen as accompanying substances.

The synthesis gas (II) is usually produced by the production processes commonly used on an industrial scale, with the type of carbon-containing feedstock (I) also playing a role here. For methane-containing feedstocks, such as in the case of natural gas or biogas, the synthesis gas (II) is preferably produced in stage (a) by steam reforming, by autothermal reforming, by a combination of steam reforming and autothermal reforming or by partial oxidation.

A particular advantage of partial oxidation is that no separate fuel gas has to be supplied to the synthesis gas generation unit and therefore no flue gas containing carbon dioxide is formed. In partial oxidation, the energy required to generate synthesis gas is obtained directly from the methane-containing feedstock through partial oxidation and the resulting combustion gases, carbon dioxide and carbon monoxide, are also used in methanol synthesis. Therefore, the partial oxidation of methane-containing streams, such as natural gas or biogas, is preferred. The product stream of the partial oxidation must be cooled. This happens via heat exchangers with water as the cooling medium. The water is evaporated and overheated, forming high-pressure steam (p = 100 - 130 bar, T = 300 - 450 °C). This high-pressure steam can be expanded to the required pressure and temperature level of medium-pressure steam in the range of 150 to 250 °C and 5 to 17 bar. Alternatively, heat removal from the methanol synthesis reactor produces heating steam in a pressure range of 5 to 17 bar.

The synthesis gas (II) produced contains carbon monoxide, carbon dioxide and hydrogen, the concentration of which together is usually 50 to 100% by volume, preferably >80% by volume and particularly preferably >90% by volume. Possible accompanying substances include, in particular, unreacted components of the carbon-containing feedstock used and by-products from its implementation, such as nitrogen, argon, water or methane. In addition to carbon monoxide, carbon dioxide and hydrogen, the synthesis gas (II) usually contains methane, as well as nitrogen and argon, which was introduced, for example, through the use of air in the synthesis gas production.

The synthesis gas (II) is converted in a methanol synthesis unit at a temperature of 150 to 300 ° C and a pressure of 5 to 10 MPa abs in the presence of a methanol synthesis catalyst. For this purpose, the synthesis gas (II) is usually compressed to the desired pressure by a compressor and reacted in a reactor under the conditions mentioned.

The reaction preferably takes place at a temperature of >170°C and particularly preferably at >190°C and preferably at <280°C and particularly preferably at <260°C. The reaction preferably takes place at >6 MPa abs and preferably at >9 MPa abs.

In principle, all reactors that are suitable for the exothermic conversion of synthesis gas to methanol under the process conditions mentioned can be used as reactors. Reactors for synthesizing methanol from synthesis gas are generally known to those skilled in the art. Examples of this are the adiabatic and quasi-isothermal reactors mentioned in Ullmann's Encyclopedia of Industrial Chemistry, Chapter "Methanol", Section 5.2.1 "Reactor Design", 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany, variable Reactors and so-called double-walled superconverters mentioned.

Methanol synthesis catalysts are generally known to those skilled in the art. Heterogeneous catalysts containing copper and zinc may be mentioned as examples. In general, these contain other elements, such as aluminum, rare earths or chromium.

During the reaction of the synthesis gas (II) containing carbon monoxide, carbon dioxide and hydrogen, methanol and water are formed. Dimethyl ether is formed as a typical byproduct. In addition, complete hydrogenation of carbon monoxide or carbon dioxide also produces methane as a further byproduct. The reaction mixture produced in the reactor therefore contains methanol, water, dimethyl ether, carbon monoxide, carbon dioxide, hydrogen and methane. Furthermore, under the reaction conditions mentioned, other by-products usually also form, such as methyl formate, acetic acid, higher alcohols with carbon numbers of >2, esters and ethers with carbon numbers of >2, as well as paraffins.

To separate the complex reaction mixture, a crude methanol stream (III) enriched with methanol and water is first condensed out. For this purpose, the reaction mixture generated in the reactor is usually fed to a condenser. Apparatuses known to those skilled in the art can be used as capacitors, which are suitable for obtaining a condensate enriched with methanol and water under the present conditions through targeted cooling. In general, the reaction mixture is cooled to a temperature below the dew point of methanol. Depending on the solubilities and vapor pressures of the components contained in the reaction mixture, the raw methanol stream (III) enriched with methanol and water still contains gases dissolved therein, such as hydrogen, carbon monoxide, carbon dioxide, dimethyl ether, methane, as well as components that have a higher boiling point than methanol. The condensed crude methanol stream (III) is then discharged from the methanol synthesis unit for further processing and led to stage (c).

The non-condensed gas stream contains in particular the unreacted starting materials carbon monoxide, carbon dioxide and hydrogen, as well as methane. In order to maintain a high partial pressure of the synthesis gas components hydrogen, carbon monoxide and carbon dioxide, part of the gas stream that has not been condensed out is usually removed. If necessary, this discharged gas stream is fed to a hydrogen separation in order to increase the partial pressure of hydrogen in the reactor. A higher partial pressure of hydrogen in the reactor reduces the formation of secondary components and, in particular, also suppresses the Fischer-Tropsch reaction. The majority of the non-condensed gas stream is returned to the methanol synthesis unit as cycle gas and passed over the methanol synthesis catalyst in order to achieve the best possible utilization of the synthesis gas and thus high yields of methanol.

Accordingly, the methanol synthesis unit in stage (b) advantageously contains a compressor for compressing the synthesis gas (II), a reactor for converting the synthesis gas (II), a condenser for condensing out the raw methanol stream (III) and a line for recycling condensed gas to the reactor.

The non-condensed gas stream that is not recirculated as synthesis cycle gas is discharged from the methanol synthesis unit as a gaseous stream (IV) and, if necessary, passed to stage (f). In stage (c) of the process, the raw methanol stream (III) condensed out in stage (b) and discharged from the methanol synthesis unit is expanded in an expansion unit to a pressure of 0.1 to 2 MPa abs and an expansion gas containing carbon dioxide and methane (V) and a degassed crude methanol stream (VI) enriched with methanol and water. The expansion usually takes place in an apparatus in which the gas phase and liquid phase can be easily separated from each other. The device is usually a liquid separator. Suitable devices for this are known to those skilled in the art.

The relaxation is preferably carried out to a pressure of >0.2 MPa abs and particularly preferably to >0.4 MPa abs and preferably to <1.5 MPa abs and particularly preferably to <1 MPa abs. In general, the temperature of the relaxed mixture is 0 to 150 ° C, preferably > 10 ° C and particularly preferably > 20 ° C and preferably < 120 ° C and particularly preferably < 60 ° C.

The degassed raw methanol stream (VI) is further enriched in methanol and water, but, depending on the solubilities and vapor pressures of the components contained in the raw methanol stream (III), also contains other components, such as gases dissolved therein such as hydrogen, carbon monoxide, carbon dioxide, Dimethyl ether, methane or components boiling higher than methanol.

The expansion gas (V) containing carbon dioxide and methane is preferably passed to stage (f). Alternatively, the expansion gas (V) can also be discharged from the methanol synthesis plant and, for example, thermally utilized or otherwise disposed of. However, it is preferred to use it within the methanol synthesis plant as a feed stream to the combustion unit in stage (f).

In stage (d) of the process, the degassed crude methanol stream (VI) obtained in stage (c) is separated by distillation in a distillation device into a low boiler stream (VII) containing carbon dioxide and dimethyl ether and a bottom stream (VIII) enriched with methanol and water.

The low boiler stream (VII) separated off by distillation contains primarily carbon dioxide and dimethyl ether as separated low boilers and, based on the composition of the degassed raw methanol stream (VI), other low boilers, such as methane, as well as methanol or higher, depending on the separation performance and operation of the distillation device Methanol boiling components such as water. The low boiler stream (VII) containing carbon dioxide and dimethyl ether is also preferably passed to stage (f). If the expansion gas (V) is passed to the combustion unit of stage (f) and is therefore already reused within the methanol synthesis plant, the low boiler stream (VII) can alternatively also be discharged from the methanol synthesis plant and, for example, thermally utilized or otherwise disposed of. However, it is preferred to use it within the methanol synthesis plant as a feed stream to the combustion unit in stage (f). The bottom stream (VIII) enriched with methanol and water also contains other components that boil higher than methanol, such as by-products from methanol synthesis that boil higher than methanol, such as acetic acid, higher alcohols, higher esters, higher ethers or paraffins.

To obtain the methanol, a water-containing high boiler stream (IX) is finally separated in stage (e) from the bottom stream (VIII) obtained in stage (d) in a further distillation device and methanol is obtained by distillation as stream (X).

The high boiler stream (IX) contains water as well as other components that boil higher than methanol, such as by-products from methanol synthesis that boil higher than methanol, such as acetic acid, higher alcohols, higher esters, higher ethers or paraffins. This stream can, for example, be fed to wastewater treatment.

Methanol can be obtained via stream (X) in a high purity of >95% by weight, preferably >98% by weight and particularly preferably >99% by weight. Accompanying substances include residual amounts of low and high boilers that have not been completely separated off by distillation, in particular water, and very small amounts of ethanol, esters and ethers.

During the stepwise workup of the reaction mixture to obtain the methanol as stream (X), streams (IV), (V) and (VII) are separated off. However, these still contain valuable components, such as carbon monoxide, carbon dioxide, methane and dimethyl ether. The aim is to extensively reuse the carbon from these valuable components for the further synthesis of methanol while at the same time avoiding carbon dioxide emissions. The additional process steps (f), (g) and (h) make it possible to specifically reuse the carbon of the valuable components for the further synthesis of methanol, i.e. to produce further valuable product, and at the same time to avoid emissions of carbon dioxide from the methanol synthesis . Steps (f), (g) and (h) are described in detail in WO 2020/048809 A1.

The invention is explained in more detail with reference to Figures 1 to 10. Show it:

1 shows a method of operation not according to the invention using a burner 4 for heating the feed stream B, with a DME-containing partial stream A-2 being fed into individual trays of the reactor 2 after cooling in the heat exchanger HE8 for cooling the reactor 2.

2 shows a procedure according to the invention, whereby a partial stream A-2 containing DME is fed into individual trays of the reactor 2 after cooling in the heat exchanger HE8 for cooling the olefin fixed bed reactor 2.

3 shows a procedure according to the invention, with a partial stream A-2 containing DME

Cooling in the heat exchanger HE8 for cooling the olefin fixed bed reactor 2 into individual trays of the reactor 2 is fed. At the same time, electric heat exchanger EH1 is used to increase the temperature difference in the apparatus HE4 and thus significantly reduce the heat transfer area.

4 shows a procedure not according to the invention using a burner 4 for heating the feed stream B, a partial stream A-2 containing DME being fed into individual trays of the olefin fixed bed reactor 2 without cooling, and the reactor 2 being operated isothermally.

5 shows a procedure according to the invention, whereby a partial stream A-2 containing DME is fed into individual trays of the olefin fixed bed reactor 2 without cooling, and the reactor 2 is operated isothermally.

6 shows a procedure according to the invention, whereby a partial stream A-2 containing DME is fed into individual trays of the olefin fixed bed reactor 2 without cooling, and the reactor 2 is operated isothermally. At the same time, electric heat exchanger EH1 is used to increase the temperature difference in the apparatus HE4 and thus significantly reduce the heat transfer area.

7 shows a procedure not according to the invention using a burner 4 for heating the feed stream B, with a methanol partial stream A1-2 being fed into individual trays of the reactor 2 for cooling the olefin fixed bed reactor 2.

8 shows a procedure according to the invention, whereby a methanol partial stream A1-2 is fed into individual trays of the reactor 2 for cooling the olefin fixed bed reactor 2.

9 shows a procedure according to the invention, whereby a methanol partial stream A1-2 is fed into individual trays of the reactor 2 for cooling the olefin fixed bed reactor 2. At the same time, electric heat exchanger EH1 is used to increase the temperature difference in the apparatus HE4 and thus significantly reduce the heat transfer area.

10 shows a method of operation not according to the invention without a DME pre-reactor using a burner 4 for heating the feed stream B, with a DME partial stream A-2 being fed into individual trays of the reactor 2 for cooling the olefin fixed bed reactor 2.

11 shows a procedure according to the invention without a DME pre-reactor, with a DME partial stream A-2 being fed into individual trays of the reactor 2 for cooling the olefin fixed bed reactor 2.

12 shows a procedure according to the invention without a DME pre-reactor, with a DME partial stream A-2 being fed into individual trays of the reactor 2 for cooling the olefin fixed bed reactor 2. At the same time, electric heat exchanger EH1 is used to increase the temperature difference in the apparatus HE4 and thus significantly reduce the heat transfer area. 13 shows a procedure not according to the invention without a DME pre-reactor using a burner 4 for heating the feed stream B, with a DME partial stream A-2 being fed into individual trays of the olefin fixed bed reactor 2 and the reactor 2 being operated isothermally.

14 shows a procedure according to the invention without a DME pre-reactor, whereby a DME partial stream A-2 is fed into individual trays of the olefin fixed bed reactor 2 and the reactor 2 is operated isothermally.

15 shows a procedure according to the invention without a DME pre-reactor, whereby a DME partial stream A-2 is fed into individual trays of the olefin fixed bed reactor 2 and the reactor 2 is operated isothermally. At the same time, electric heat exchanger EH1 is used to increase the temperature difference in the apparatus HE4 and thus significantly reduce the heat transfer area.

List of reference symbols:

1 DME pre-reactor

2 Olefin fixed bed reactor

3 product gas quench

4 burners

5 product separation section

6 compressor

HE1 to HE9 heat exchanger

EH1 Electric heat exchanger

A1 stream containing methanol

A1-1, A1-2 partial streams of A1

A DME containing stream

A-1, A-2 partial streams of A

B DME, recycled hydrocarbons and steam containing feed stream to the olefin fixed bed reactor

D Product gas stream of the olefin fixed bed reactor F Product gas stream containing hydrocarbons G1, G2, G3 Water streams

H 1 hydrocarbon recycle stream

K quench water circulation stream

P product hydrocarbons

W wastewater stream

Q1 to Q12 heat flows

Examples

The heat flows Q1 to Q11 according to the procedures corresponding to FIGS. 1 to 15 were calculated as an example for a production of 60 t/h of propylene with minimal production of ethylene and butylene. Results are summarized in the table below.

Claims

Patent claims

1 . Process for producing C2- _C4 olefins from dimethyl ether and optionally methanol with the steps:

A) providing a stream A containing dimethyl ether;

C) heating the feed stream B in one or more heat exchangers to a temperature in the range from 430 to 500 ° C and feeding it into an olefin fixed bed reactor, the heating also being able to take place before mixing individual partial streams to form the feed stream B in step B);

D) Catalytic conversion of the feed stream B at a temperature in the range from 430 to 520 ° C to give a product gas stream D containing C2-C4 olefins, further C2-C6 hydrocarbons, methanol and water vapor;

F) Further cooling of the product gas stream D to a temperature in the range from 35 to 65 ° C by bringing it into contact with at least one water-containing quench cycle stream K, whereby water and methanol are condensed out and a hydrocarbon product gas stream F depleted in water and methanol is obtained;

H) separation of one or more product streams P containing C2-C4 olefins and recovery of at least one hydrocarbon recycle stream R containing C2-Ce hydrocarbons from the hydrocarbon product gas stream F and recycling to step B).

2. The method according to claim 1, characterized in that no additional heat generated by combustion of fossil fuels is used to heat the second feed gas stream B in step C).

3. The method according to claim 2, characterized in that the heating of the second feed gas stream B in step C) takes place in part by means of an electrical heat exchanger.

4. The method according to any one of claims 1 to 3, characterized in that the medium-pressure steam stream has a temperature in the range of 150 to 250 ° C and a pressure in the range of 5 to 17 bar.

5. The method according to any one of claims 1 to 4, characterized in that the medium-pressure steam stream is generated in a methanol synthesis upstream of step A) and / or in a synthesis gas production upstream of this methanol synthesis.

6. The method according to any one of claims 1 to 5, characterized in that the partial stream G1 of the water-containing quench cycle stream in step G) is additionally heated and evaporated by heat exchange with the product gas stream D.

7. The method according to any one of claims 1 to 6, characterized in that the partial stream G1 of the water-containing quench cycle stream in step G) is heated to at least 50%, based on the amount of heat supplied, by heat exchange with medium-pressure steam.

8. The method according to any one of claims 1 to 7, characterized in that the hydrocarbon recycle stream H1 containing C2-C6 hydrocarbons is additionally heated by heat exchange with medium-pressure steam.

9. The method according to any one of claims 1 to 8, characterized in that step H) comprises:

H1) Compression of the hydrocarbon product gas stream F, whereby a liquid hydrocarbon stream H11 containing propylene, C ₄ -, C5 and C6 ⁺ hydrocarbons and a gaseous hydrocarbon stream H12 containing ethane, ethene and propylene are obtained;

H3) separating a propylene-containing stream H31 from the liquid hydrocarbon stream H21, obtaining a stream H32 containing C ₄ , C5 and C6 ⁺ hydrocarbons; or separating a stream H31 containing propylene and C ₄ hydrocarbons, obtaining a stream H32 containing C ₄ , C5 and C6 ⁺ hydrocarbons;

H4) separating a stream H41 containing C6 ⁺ hydrocarbons from the stream H32 containing C ₄ , C5 and C6 ⁺ hydrocarbons, whereby a stream H42 containing C ₄ , C5 and Ce hydrocarbons is obtained; the current may contain H41 aromatic Cβ hydrocarbons and the stream H42 aliphatic Cβ hydrocarbons;

H5) separation of a propylene-containing stream H51 from the ethane, ethene and propylene-containing gaseous hydrocarbon stream H12, whereby a ethane and ethene-containing stream H52 is obtained;

H6) separation of a butene-containing stream H61 from the C4, C5 and Ce hydrocarbon-containing stream H42, whereby a C5 and Ce hydrocarbon-containing stream H62 is obtained; and/or separating a propylene-containing stream H63 from the stream H31, obtaining a butene-containing stream H64; H7) Obtaining at least one recycle stream R from one or more of the streams selected from the stream H42 containing C4, C5 and Ce hydrocarbons, the stream H62 containing C5 and Ce hydrocarbons, the stream H31 containing propylene, the stream containing propylene H51, the propylene-containing stream H63, the butene-containing stream H61, the butene-containing stream H64 and the ethane and ethene-containing stream H52. Method according to one of claims 1 to 9, characterized in that step A) involves feeding a methanol-containing feed stream A1 into a dimethyl ether fixed-bed reactor and catalytic conversion of methanol to dimethyl ether, whereby a product stream A containing dimethyl ether, methanol and water vapor is obtained. Method according to claim 10, characterized in that the methanol fed in step A) is produced in an upstream methanol production with the steps:

(c) the raw methanol stream (III) from stage (b) is expanded in an expansion unit to a pressure of 0.1 to 2 MPa abs and an expansion gas (V) containing carbon dioxide and methane and a degassed raw material enriched with methanol and water -Methanol stream (VI) obtained;

(d) the degassed crude methanol stream (VI) from stage (d) is converted into a low boiler stream (VII) containing carbon dioxide and dimethyl ether in a distillation device. separated by distillation and a bottom stream (VIII) enriched with methanol and water is obtained; and

(e) optionally, a water-containing high boiler stream (IX) is separated from the bottom stream (VIII) from stage (d) in a further distillation device and methanol is obtained by distillation as stream (X). Method according to claim 11, characterized in that the methanol production also includes steps (f) to (h):

(f) the valuable components carbon monoxide, carbon dioxide, dimethyl ether and methane of the streams (IV) and of at least one of the two streams (V) and (VII) are fed to a combustion unit and therein with the supply of an oxygen-containing gas (XI), which has an oxygen content from 30 to 100% by volume, burned and carbon dioxide-containing flue gas (XII) is formed;

(h) the stream (XIV) from stage (g) separated in the carbon dioxide recovery unit and enriched with carbon dioxide is recycled to the synthesis gas production unit of stage (a) and/or to the methanol synthesis unit of stage (b). Method according to claim 11 or 12, characterized in that the medium-pressure steam stream used in step G) of the production of C2-C ₄ olefins comes from the synthesis gas production unit of step (a) of the methanol production and/or the methanol synthesis unit of step (b) of methanol production.