Thermally integrated process for producing c2-c4

Abstract

The invention relates to a method for producing C2-C4 olefins from dimethyl ether and optionally methanol, having the following steps: A) providing a stream A containing dimethyl ether; b) mixing at least a portion of the stream A with at least one hydrocarbon reflux R containing C2-C6 hydrocarbons and with a water vapor stream G2, 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 DEG C to 500 DEG C and feeding it into an olefin fixed bed reactor, wherein the heating process may also be carried out prior to mixing the individual sub-streams so as to form the feed stream B in step B); d) catalytically converting the feed stream B at a temperature ranging from 430 DEG C to 520 DEG C so as to form a product gas stream D containing C2-C4 olefins, additional C2-C6 hydrocarbons, methanol and water vapor; e) cooling the product gas stream D to a temperature in the range of 170 DEG C to 220 DEG C by exchanging heat with the feed gas stream B in one or more heat exchangers; f) further cooling the product gas stream D to a temperature in the range of 35 DEG C to 65 DEG C by bringing the product gas stream into contact with at least one aqueous quench circuit stream K wherein water and methanol are condensed from the product gas stream and a water-and methanol-depleted hydrocarbon product gas stream F is obtained; g) separating at least one sub-stream G1 of the at least one aqueous quench circuit stream K and heating and vaporizing the sub-stream G1 by exchanging heat with medium-pressure water vapor in one or more heat exchangers or by means of an electrical heating process, obtaining a water vapor stream G2 and feeding the water vapor stream G2 to step B); and H) separating one or more C2-C4 olefin-containing product streams P from the hydrocarbon product gas stream F and obtaining at least one C2-C6 hydrocarbon-containing hydrocarbon return stream R and returning it to step B).

Description

[0001] The present invention relates to a heat-integrated process for preparing C2-C4 olefins from dimethyl ether with or without methanol.

[0002] It is known that propylene can be produced by converting a methanol / dimethyl ether mixture in a fixed bed reactor (methanol to propylene, MTP reactor). The known fixed bed reactor is operated with a zeolite catalyst at a temperature of about 480° C. For this purpose, the methanol / DME-containing reactant gas stream must be heated to a high temperature before entering the reactor.

[0003] L. Jiang et al., Chinese Journal of Chemical Engineering 26 (2018), 2102-2111, describe a process for preparing propylene from methanol, wherein methanol is first converted into dimethyl ether (DME), and then the product mixture is converted into propylene and further products. Figure 8 , the method is described as follows: methanol is preheated, evaporated and further heated by heat exchange with the product gas from the DME reactor in a heat exchanger. Methanol vapor is fed to the DME reactor at a temperature of 270°C. Then, the first substream of the product gas from the DME reactor is 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 heated again, while the liquid phase is further cooled, and the gas phase and the liquid phase are fed to a separate tray of a propylene fixed bed reactor (MTP reactor). Alternatively, methanol can also be fed separately to a separate tray of the MTP reactor. The second substream of the product gas from the DME reactor is mixed with a hydrocarbon recycle stream and water vapor, heated to a temperature of about 460°C with a burner and fed to a propylene reactor, in which almost all of the methanol and DME are converted into propylene and additional hydrocarbons.

[0004] A disadvantage of the process described is that most of the heat required for heating the reactant stream fed to the propylene reactor is provided by burning natural gas or other fossil hydrocarbons in the burner. This has a very negative effect on the CO2 balance of the entire process. However, against the background of increasingly severe climate change caused by anthropogenic activities, there is an increasing drive to achieve industrial production processes that emit only small amounts of CO2 of fossil origin into the atmosphere, or better still, no CO2 at all.

[0005] The object of the present invention is to provide a heat-integrated process for the preparation of C2-C4-olefins from dimethyl ether in which the provision of process heat by combustion of exogenous fossil hydrocarbons can be dispensed with in steady-state operation.

[0006] This object is achieved by a process for preparing C2-C4 olefins from dimethyl ether with or without methanol, the process comprising the following steps:

[0007] A) providing a stream A comprising dimethyl ether;

[0008] B) mixing at least a portion of stream A with at least one hydrocarbon recycle stream R comprising C2-C6 hydrocarbons and a steam stream G2 to obtain a feed stream B;

[0009] C) heating the feed stream B to a temperature in the range of 430° C. to 500° C. in one or more heat exchangers and feeding it into an olefin fixed bed reactor, wherein the heating can also be carried out before mixing the individual substreams to obtain the feed stream B in step B);

[0010] D) catalytically converting the feed stream B at a temperature in the range of 430° C. to 520° C. into a product gas stream D comprising C2-C4 olefins, additional C2-C6 hydrocarbons, methanol and water vapor;

[0011] E) cooling the product gas stream D to a temperature in the range of 170° C. to 220° C. by heat exchange with the feed gas stream B in one or more heat exchangers;

[0012] F) further cooling the product gas stream D to a temperature in the range of 35° C. to 65° C. by contacting with at least one quench circulation stream K comprising water and condensing water and methanol to obtain a hydrocarbon product gas stream F depleted in water and methanol;

[0013] G) separating at least one substream G1 of the at least one aqueous quench circulation stream K and heating and evaporating the substream G1 by heat exchange with medium-pressure steam in one or more heat exchangers or by electrical heating to obtain a steam stream G2, and feeding the steam stream G2 into step B);

[0014] H) separating one or more product streams P comprising C2-C4 olefins from the hydrocarbon product gas stream F and obtaining at least one hydrocarbon recycle stream R comprising C2-C6 hydrocarbons and recycling it to step B).

[0015] In one embodiment of the process of the present invention, in step A), a stream A consisting essentially of DME (>90% DME by weight) is fed into the process and divided into two substreams. The first substream A-1 accounts for no more than 80% by weight of stream A and is used as described in step B). The second substream is mixed with a substream G3 of the aqueous quenching circulation stream mentioned in step G) and fed as stream A-2 without further heating to one or more separate trays of the olefin fixed bed reactor in step C). The olefin fixed bed reactor can also be operated isothermally. Isothermal operation can be carried out, for example, in the manner described in WO 2017 / 102096 A1. For example, there may be heat transfer surfaces installed in the olefin fixed bed reactor, which are operated, for example, with liquid salt or high-pressure steam as a heat transfer medium. By means of the heat transfer medium flowing through the heat transfer surface in the reactor, the generated reaction heat is removed from the reactor and therefore this is an isothermal operation.

[0016] In a preferred embodiment of the process of the present invention, step A) comprises feeding a feed gas stream A1 comprising methanol into a dimethyl ether fixed bed reactor and catalytically converting the methanol into dimethyl ether to obtain a product gas stream comprising dimethyl ether, methanol and water vapor. If the stream A1 comprises ethanol, the product stream A will not only comprise dimethyl ether, methanol and water vapor, but also ethanol and ethylene.

[0017] C2-C4 olefins are ethylene, propylene, 1-butene, 2-butene and isobutylene. It is preferred that ethylene and / or propylene are prepared by the process of the invention.

[0018] In a preferred embodiment, the method of the present invention therefore comprises the following steps:

[0019] A) feeding a feed stream A1 comprising methanol into a dimethyl ether fixed bed reactor and catalytically converting the methanol into dimethyl ether to obtain a product stream A comprising dimethyl ether, methanol and water vapor;

[0020] B) mixing at least a portion of the product stream A with at least one hydrocarbon recycle stream R comprising C2-C6 hydrocarbons and a steam stream G2 to obtain a second feed stream B;

[0021] C) heating the second feed stream B to a temperature in the range of 430° C. to 500° C. in one or more heat exchangers and feeding it into an olefin fixed bed reactor, wherein the heating can also be carried out before mixing the individual substreams to obtain feed stream B in step B);

[0022] D) catalytically converting the feed stream B at a temperature in the range of 430° C. to 520° C. into a product gas stream D comprising ethylene, propylene, further C2-C6 hydrocarbons, methanol and water vapor;

[0023] E) cooling the product gas stream D to a temperature in the range of 170° C. to 220° C. by heat exchange with the feed stream B in one or more heat exchangers;

[0024] F) further cooling the product gas stream D to a temperature in the range of 35° C. to 65° C. by contacting with at least one quench circulation stream K comprising water and condensing water and methanol to obtain a hydrocarbon product gas stream F depleted in water and methanol;

[0025] G) separating at least one substream G1 of the at least one aqueous quench circulation stream K and heating and evaporating the substream G1 by heat exchange with medium-pressure steam in one or more heat exchangers or by electrical heating to obtain a steam stream G2, and feeding the steam stream G2 into step B);

[0026] H) separating one or more product streams P comprising ethylene and / or propylene from the hydrocarbon product gas stream F and obtaining at least one hydrocarbon recycle stream R comprising C2-C6 hydrocarbons and recycling it to step B).

[0027] In step A), preferably a feed stream A1 comprising methanol is fed into a dimethyl ether fixed bed reactor and the methanol is catalytically converted into dimethyl ether to obtain a product stream A comprising dimethyl ether, methanol and water vapor.

[0028] A feed stream A1 comprising methanol, preferably from an upstream methanol synthesis plant, is evaporated and heated to a temperature of typically 250° C. to 300° C. (e.g. 275° C.) and fed into a dimethyl ether fixed bed reactor. The catalyst used is typically γ-alumina. The conversion temperature is typically 250° C. to 400° C.; the pressure is typically 1 to 25 bar, e.g. 4 bar. The first product gas stream leaving the dimethyl ether fixed bed reactor is at a temperature of typically 350° C. to 400° C. (e.g. 370° C.). The methanol conversion is typically 50% to 90%, preferably 65% ​​to 85%, e.g. 75%. The product gas stream A is cooled by heat exchange with the feed stream A1 comprising methanol. After the heat exchange, the first product gas stream is at a temperature of typically 180° C. to 250° C.

[0029] In step B), at least a portion of this stream A is mixed with a hydrocarbon recycle stream comprising C2-C6 hydrocarbons and a steam stream G2 to obtain a feed gas stream B. Typically, this portion of stream A is at least 50% by weight and preferably up to 80% by weight. A further portion A-2 of stream A, preferably at least 20% by weight, can be fed directly into one or more trays of the fixed bed reactor of olefins. If this portion of stream A comes from an upstream dimethyl ether reactor, it is typically cooled before being fed into the trays of the fixed bed reactor of olefins, preferably to a temperature in the range of 30° C. to 60° C. This substream A-2 is preferably fed into the reactor in liquid form.

[0030] If the olefin fixed bed reactor is operated isothermally and cooled, the cooling of substream A-2 can also be omitted. Isothermal operation can be carried out, for example, in the manner described in WO 2017 / 102096 A1. For example, there may be heat transfer surfaces installed in the olefin fixed bed reactor, which are operated, for example, with liquid salt or high-pressure steam as heat transfer medium. By means of the heat transfer medium flowing through the heat transfer surface in the reactor, the generated reaction heat is removed from the reactor and therefore this is an isothermal operation. In order to establish the desired product distribution in the product gas stream D, substream A-2 can also be fed to the intermediate stage of the olefin fixed bed reactor.

[0031] In a further embodiment, a stream comprising methanol is fed directly into one or more trays of an olefin fixed bed reactor. It is preferred to feed a portion of a first feed stream A1 comprising methanol, for example from an upstream methanol synthesis unit, directly into an olefin fixed bed reactor. This portion of the feed stream A1 comprising methanol may be up to 60% by weight of the total feed stream A1.

[0032] The hydrocarbon recycle stream R from the removal of C2-C4 olefins generally comprises C4-C6 hydrocarbons. Depending on whether ethylene, propylene or butenes are obtained as valuable products in step H), the hydrocarbon recycle stream R may also comprise ethylene, propylene and / or butenes. If the amount of C2-C4 olefins obtained as products in step H) comprises propylene to an extent of at least 85% by weight, for example the stream R will consist of C4-C6 hydrocarbons to an extent of at least 50% by weight. The hydrocarbon recycle stream R is generally at a temperature in the range of 100° C. to 175° C., preferably in the range of 130° C. to 160° C., before mixing. The hydrocarbon recycle stream R is preferably heated by heat exchange with medium-pressure steam and is generally at a temperature of 30° C. to 100° C., preferably 50° C. to 80° C., before heating.

[0033] The product stream A from the dimethyl ether fixed bed reactor is also mixed with a steam stream G2. The steam stream G2 is generally at a temperature in the range of 100° C. to 200° C., preferably in the range of 100° C. to 150° C. According to the invention, this steam stream is heated by heat exchange with medium-pressure steam.

[0034] The feed stream B thus obtained generally comprises from 15 to 50% by weight, preferably from 20 to 40% by weight, of water vapor. It generally further comprises from 5 to 10% by weight of methanol, from 10 to 20% by weight of dimethyl ether and from 25 to 50% by weight of C2-C6 hydrocarbons.

[0035] In step C), feed stream B is heated in one or more heat exchangers to a temperature in the range of 430° C. to 500° C. and fed to the olefin fixed bed reactor. This heating can also be carried out before the mixing of the individual substreams in step B).

[0036] Typically, feed stream B is at a temperature in the range of 430°C to 500°C (e.g., 470°C) when fed into the olefin fixed bed reactor. Feed stream B is heated to this temperature by heat exchange with the (second) product gas stream D from the olefin fixed bed reactor. The present invention heats the steam stream G1 by heat exchange with medium-pressure steam, so that a temperature of 430°C to 500°C can be reached in feed stream B by heat exchange with the (second) product gas stream D, without the need for additional heating with a burner in steady-state operation. The small temperature difference between the two gas streams B and D increases the required heat transfer area. In equipment with high production capacity, this may result in a disproportionately large heat exchanger. In this case, the heating of the last part of feed stream B can also be carried out with an electric heat exchanger, which increases the temperature difference in the heat exchanger between streams B and D. This reduces the necessary heat transfer area to an practicable level. As long as electricity is generated without burning fossil energy carriers, stream B is still heated without CO2 emissions.

[0037] In one embodiment of the process according to the invention, the second feed gas stream B is heated in step C) partly by means of an electric heat exchanger.

[0038] The olefins are subsequently converted catalytically in a fixed bed reactor in step D) into a product gas stream D comprising ethylene, propylene, further C2-C6 hydrocarbons, methanol and water vapor. The conversion is usually carried out over a zeolite catalyst, preferably over a catalyst based on ZSM-5 zeolite. The reaction temperature is usually 430° C. to 500° C., preferably 460° C. to 480° C. The pressure is usually 1.3 to 4 bar. The resulting second product gas stream D preferably has the following composition: 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, and also C6 + Hydrocarbons and 0.1 to 1.5% by weight of methanol and DME.

[0039] The olefin fixed bed reactor is usually in the form of a tray reactor. The number of trays is preferably 4 to 6. In one embodiment, up to 50% by weight of the gas stream A is directly fed into one or more trays of the olefin fixed bed reactor, preferably all trays of the olefin fixed bed reactor. In another embodiment, a stream containing methanol is directly fed into one or more trays of the olefin fixed bed reactor, preferably all trays of the olefin fixed bed reactor.

[0040] The (second) product gas stream D on leaving the reactor is at a temperature of typically 430 to 520°C, preferably 460 to 480°C.

[0041] In step E), the product gas stream D is cooled in one or more heat exchangers by heat exchange with the feed gas stream B to a temperature in the range of 160° C. to 220° C. After this cooling step, the temperature of the (second) product gas stream D is typically 160° C. to 220° C., preferably 170° C. to 210° C., for example 190° C.

[0042] In step F), the product gas stream D is further cooled to a temperature in the range of 35°C to 60°C by contacting with one or more quench recycle streams comprising water, and condensing water and methanol, to obtain a water- and methanol-depleted hydrocarbon product gas stream F. The hydrocarbon product gas stream F thus obtained substantially comprises ethylene, propylene and further C2-C6 hydrocarbons.

[0043] In step G), a portion of the water in at least one quench circulation stream K is separated and, according to the invention, the substream G1 is heated and evaporated in one or more heat exchangers by heat exchange with medium-pressure steam or by electrical heating to obtain a heated steam stream G2. In step B), the heated steam stream G2 is mixed with the first product stream A (or feed stream A) originating from the dimethyl ether fixed bed reactor.

[0044] Typically, the aqueous quench circulation stream is heated in step G) to an extent of at least 50% based on the heat supplied by heat exchange with medium-pressure steam or by electrical heating. In addition, a substream G1 of the aqueous quench circulation stream can be additionally heated and evaporated in step G) by heat exchange with the product gas stream D.

[0045] Before heating, the substream G1 separated from the quench circulation stream K is in liquid form and is generally at a temperature in the range of 70° C. to 100° C. After heating and evaporation, the vapor stream G1 is at a temperature in the range of 100° C. to 150° C., preferably 120° C. to 140° C., and correspondingly at a pressure of 1 to 6 bar, preferably 2 to 4 bar.

[0046] In a first embodiment, the water stream G1 withdrawn from the quench circuit is heated by heat exchange with medium-pressure steam. In the context of the present invention, medium-pressure steam is steam at a temperature of at least 150° C. and a pressure of at least 5 bar, preferably at a temperature in the range of 150° C. to 250° C., preferably 150° C. to 200° C. and correspondingly at a pressure in the range of 5 to 17 bar, preferably 5 to 11 bar.

[0047] All stated pressures are absolute pressures.

[0048] The medium-pressure steam stream used in step G) preferably comes from the methanol synthesis upstream of step A) and / or from the synthesis gas production upstream of said methanol synthesis. The medium-pressure steam stream may come from spatially adjacent, separate production plants.

[0049] In a second embodiment, the water flow G1 drawn off from the quench circuit is heated by electrical heating. The electrical heating can be performed, for example, in a tank with installed electrical heating elements.

[0050] According to the invention, the electrical energy supplied to the electric heating is mainly generated in a renewable manner, ie without the combustion of fossil energy carriers. Therefore, the electrical energy supplied to the electric heating is provided to a large extent without climate-damaging CO2 emissions.

[0051] Medium-pressure steam can also be generated by electrical heating. Electrical heating can be carried out, for example, in a tank with an installed electrical heating element.

[0052] In step H), one or more product streams P comprising C2-C4 olefins are separated from the hydrocarbon product gas stream F, and at least one recycle stream R comprising C2-C6 hydrocarbons is obtained. The overall recycle stream R is usually composed of a plurality of individual recycle streams. Typically, the total recycle stream R comprising C2-C6 hydrocarbons substantially (i.e. to an extent of >95% by weight) comprises C2-C6 hydrocarbons.

[0053] The hydrocarbon recycle stream R comprising C2-C6 hydrocarbons can likewise be heated by heat exchange with medium-pressure steam.

[0054] The hydrocarbon recycle stream R comprising C2-C6 hydrocarbons may be heated by heat exchange with a product gas stream D before being mixed with stream A to obtain feed stream B.

[0055] Typically, step H) comprises steps H1) to H7):

[0056] H1) compressing the hydrocarbon product gas stream F to obtain a product gas stream containing propylene and C4, C5 and C6 + a liquid hydrocarbon stream H11 of hydrocarbons, and a gaseous hydrocarbon stream H12 comprising ethane, ethylene and propylene;

[0057] H2) separating water from the liquid hydrocarbon stream H11 by phase separation to obtain a liquid hydrocarbon stream H21;

[0058] H3) separating a stream H31 comprising propylene from the liquid hydrocarbon stream H21 to obtain a stream H31 comprising C4, C5 and C6 + or separating the stream H31 containing propylene and C4 hydrocarbons to obtain a stream H32 containing C4, C5 and C6 + a hydrocarbon stream H32;

[0059] H4) from the containing C4, C5 and C6 + The hydrocarbon stream H32 contains C6 + a stream H41 of hydrocarbons to obtain a stream H42 comprising C4, C5 and C6 hydrocarbons; stream H41 optionally comprises aromatic C6 hydrocarbons and stream H42 optionally comprises aliphatic C6 hydrocarbons;

[0060] H5) separating a stream H51 comprising propylene from a gaseous hydrocarbon stream H12 comprising ethane, ethylene and propylene to obtain a stream H52 comprising ethane and ethylene;

[0061] H6) separating a stream H61 comprising butenes from a stream H42 comprising C4, C5 and C6 hydrocarbons to obtain a stream H62 comprising C5 and C6 hydrocarbons; and / or separating a stream H63 comprising propylene from a stream H31 to obtain a stream H64 comprising butenes;

[0062] H7) at least one recycle stream R is obtained from one or more streams selected from the following: a stream H42 comprising C4, C5 and C6 hydrocarbons, a stream H62 comprising C5 and C6 hydrocarbons, a stream H31 comprising propylene, a stream H51 comprising propylene, a stream H63 comprising propylene, a stream H61 comprising butenes, a stream H64 comprising butenes and a stream H52 comprising ethane and ethylene.

[0063] Steps H3), H4), H5) and H6) are carried out in a standard distillation apparatus. Useful distillation apparatuses include in principle the apparatuses known to the person skilled in the art for such separation tasks. And the actual column body with internal components, which usually also includes a top condenser and a reboiler. The column body may already be equipped with structured packing, random packing or trays, for example. The distillation apparatus can be designed and operated by the common general knowledge of the person skilled in the art.

[0064] The process of the present invention for preparing C2-C4 olefins from dimethyl ether with or without methanol preferably follows a process for preparing methanol, wherein the process for preparing methanol comprises the following steps:

[0065] (a) producing a synthesis gas (II) comprising carbon monoxide, carbon dioxide and hydrogen from a hydrocarbon-containing feedstock (I) in a synthesis gas production unit;

[0066] (b) feeding the synthesis gas (II) from stage (a) into a methanol synthesis unit and converting it in the presence of a methanol synthesis catalyst at a temperature of from 150° C. to 300° C. and a pressure of from 5 to 10 MPa absolute into a reaction mixture comprising methanol, water, carbon monoxide, carbon dioxide, hydrogen, dimethyl ether and methane, condensing a crude methanol stream (III) rich in methanol and water from said reaction mixture, and conducting the crude methanol stream (III) and a gaseous stream (IV) comprising carbon monoxide, carbon dioxide, hydrogen and methane from the methanol synthesis unit,

[0067] (c) expanding the crude methanol stream (III) from stage (b) to a pressure of from 0.1 to 2 MPa absolute in an expansion unit and obtaining an expanded gas (V) comprising carbon dioxide and methane and a degassed crude methanol stream (VI) rich in methanol and water;

[0068] (d) separating by distillation in a distillation apparatus a low-boiling stream (VII) comprising carbon dioxide and dimethyl ether from the degassed crude methanol stream (VI) from stage (c) and obtaining a methanol- and water-rich bottoms stream (VIII); and

[0069] (e) In a further distillation apparatus, a high-boiling stream (IX) comprising water is optionally separated from the bottom stream (VIII) from stage (d) and methanol is obtained as stream (X) by distillation. Step (e) can also be omitted, since anhydrous methanol is not required.

[0070] The methanol- and water-rich bottoms stream (VIII) or, as the case may be, the pure methanol stream (X) can be used in the process of the invention.

[0071] The medium-pressure steam stream used in step G) of the propylene production according to the present invention preferably comes from a synthesis gas production unit in step (a) of the methanol production and / or from a methanol synthesis unit in step (b) of the methanol production.

[0072] The method for preparing methanol preferably further comprises the following steps:

[0073] (f) feeding the valuable carbon monoxide, carbon dioxide, dimethyl ether and methane components of stream (IV) and at least one of the two streams (V) and (VII) into a combustion unit and combusting them in the combustion unit with supply of an oxygen-containing gas (XI) having an oxygen content of 30 to 100% by volume to form a flue gas (XII) containing carbon dioxide;

[0074] (g) separating a carbon dioxide-rich stream (XIV) from the carbon dioxide-containing flue gas (XII) from stage (f) in a carbon dioxide recovery unit to form a waste gas stream (XIII); and

[0075] (h) recycling the carbon dioxide-rich stream (XIV) separated off in the carbon dioxide recovery unit from stage (g) to the synthesis gas production unit of stage (a) and / or to the methanol synthesis unit of stage (b).

[0076] Such a process comprising steps (f), (g) and (h) is described in WO 2020 / 048809 A1.

[0077] The medium-pressure steam stream used in step G) of the preparation of C2-C4 olefins preferably comes from a synthesis gas production unit in step (a) of the methanol preparation and / or a methanol synthesis unit in step (b) of the methanol preparation.

[0078] The raw material of the production synthesis gas that can be used in this method is a variety of different carbonaceous raw materials, no matter they are in solid, liquid or gaseous form, and no matter how their chemical properties are. For example, synthesis gas can be produced using coal or hydrocarbons and compounds comprising carbon and hydrogen. Preferred carbonaceous raw materials include natural gas, biogas, coal, wood, plastics, mineral oil, bio-naphtha, or from mineral oil or natural gas processing, from chemical production methods, from renewable raw materials or from the carbonaceous stream of plastic recycling. In the case of coal or wood, synthesis gas is produced, for example, by gasification process (also referred to as coal gasification or wood gasification). Suitable raw materials from mineral oil or natural gas processing are, for example, naphtha, LPG, gasoline, heavy oil or vacuum residue. Carbonaceous stream from chemical production process means, for example, obtained as by-product and not for pure heat utilization, and can also be used as the raw material for producing synthesis gas.

[0079] Particular preference is given to using methane-containing streams, and very particular preference is given to using natural gas or biogas. It is possible and even advantageous here to feed the carbon dioxide present in the natural gas and in particular in the biogas likewise into the synthesis gas production unit.

[0080] In the synthesis gas production unit, firstly a synthesis gas (II) containing carbon monoxide, carbon dioxide and hydrogen is produced from a hydrocarbonaceous feedstock (I). Natural gas typically contains 75% to 100% by volume of methane. Accompanying substances with methane include in particular the higher hydrocarbons ethane, propane, butane, but also ethylene. Biogas typically contains 40% to 75% by volume of methane and as accompanying substances mainly carbon dioxide, water, nitrogen and oxygen.

[0081] Typically, the synthesis gas (II) is produced by production methods commonly used on an industrial scale, although the nature of the carbonaceous feedstock (I) also plays a role here. In the case of methane-containing feedstocks, for example 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.

[0082] A particular advantage of partial oxidation is that the synthesis gas production unit does not need to be supplied with a separate fuel gas and therefore no flue gas containing carbon dioxide is formed. In partial oxidation, the energy required for synthesis gas production is obtained directly from the methane-containing feedstock by partial oxidation, and the combustion gases, carbon dioxide and carbon monoxide formed are likewise used in the methanol synthesis. Preference is therefore given to partially oxidizing methane-containing streams, such as, for example, natural gas or biogas.

[0083] The product stream from the partial oxidation must be cooled. This is achieved by a heat exchanger with water as the cooling medium. This evaporates and superheats the water, forming high-pressure steam (p = 100-130 bar, T = 300°C-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°C to 250°C and 5 to 17 bar. Alternatively, the removal of heat from the methanol synthesis reactor produces heating steam in the pressure range of 5 to 17 bar.

[0084] The synthesis gas (II) produced comprises carbon monoxide, carbon dioxide and hydrogen, wherein its overall concentration is typically 50% to 100% by volume, preferably ≥80% by volume and more preferably ≥90% by volume. Possible accompanying substances particularly include unconverted components of the carbonaceous raw materials used and by-products from their conversion, such as nitrogen, argon, water or methane. Typically, as a result of the preparation, the synthesis gas (II) comprises, in addition to carbon monoxide, carbon dioxide and hydrogen, methane and also nitrogen and argon, which have been introduced, for example, by using air in the synthesis gas production.

[0085] The conversion of synthesis gas (II) is carried out in the presence of a methanol synthesis catalyst at a temperature of 150° C. to 300° C. and a pressure of 5 to 10 MPa absolute in a methanol synthesis unit. For this purpose, the synthesis gas (II) is typically compressed to the desired pressure with the aid of a compressor and converted in a reactor under specified conditions.

[0086] The conversion is preferably carried out at a temperature of ≥170° C. and more preferably at ≥190° C. and preferably at ≤280° C. and more preferably at ≤260° C. The conversion is preferably carried out at a pressure of ≥6 MPa absolute and preferably at a pressure of ≥9 MPa absolute.

[0087] The reactor used can in principle be any reactor suitable for exothermic conversion of synthesis gas into methanol under specified process conditions. Reactors for synthesizing methanol from synthesis gas are common knowledge to those skilled in the art. Examples of these include adiabatic and quasi-isothermal reactors, variobar reactors and so-called double-walled superconverters, which are mentioned in Ullmann's Encyclopedia of Industrial Chemistry, "Methanol", chapter 5.2.1, "Reactor Design", 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim, Germany.

[0088] Methanol synthesis catalysts are common knowledge to those skilled in the art. Examples include copper-containing and zinc-containing heterogeneous catalysts. Typically, they also contain additional elements, such as aluminum, rare earths or chromium.

[0089] The conversion of synthesis gas (II) comprising carbon monoxide, carbon dioxide and hydrogen forms methanol and water.

[0090] The typical by-product formed is dimethyl ether. In addition, the complete hydrogenation of carbon monoxide or carbon dioxide also produces methane as another by-product. Therefore, the reaction mixture produced in the reactor comprises methanol, water, dimethyl ether, carbon monoxide, carbon dioxide, hydrogen and methane. However, under the reaction conditions mentioned, additionally formed typically are also other by-products, for example methyl formate, acetic acid, carbon number>2 higher alcohols, carbon number>2 esters and ethers and also paraffins.

[0091] In order to separate the complex reaction mixture, first condense out the crude methanol stream (III) rich in methanol and rich in water.For this purpose, typically the reaction mixture produced in the reactor is fed into a condenser.The condenser used can be a device well known to those skilled in the art suitable for obtaining the condensate of rich methanol and rich in water by controlled cooling under the conditions of the present invention.Usually, the reaction mixture is cooled to a temperature lower than the methanol dew point.According to the solubility and vapor pressure of the component present in the reaction mixture, the crude methanol stream (III) rich in methanol and rich in water still comprises the gas dissolved therein, such as hydrogen, carbon monoxide, carbon dioxide, dimethyl ether, methane and a component with a higher boiling point than methanol.Then the crude methanol stream (III) condensed out is discharged from the methanol synthesis unit to carry out further aftertreatment and is directed to stage (c).

[0092] Uncondensed gas stream especially comprises unconverted carbon monoxide, carbon dioxide and hydrogen raw material and methane.In order to obtain the high partial pressure of synthesis gas component hydrogen, carbon monoxide and carbon dioxide, typically discharge a part of uncondensed gas stream.If necessary, the gas stream of this discharge is sent to remove hydrogen so as to increase the partial pressure of hydrogen in the reactor.Higher hydrogen partial pressure in the reactor reduces the formation of secondary components and especially also suppresses Fischer-Tropsch reaction.The major part of uncondensed gas stream is recycled in the methanol synthesis unit as circulating gas, and is directed on the methanol synthesis catalyst, so as to realize the maximum utilization of synthesis gas, and therefore realize the high yield of methanol.

[0093] Thus, the methanol synthesis unit in stage (b) advantageously comprises a compressor for compressing the synthesis gas (II), a reactor for converting the synthesis gas (II), a condenser for condensing out a crude methanol stream (III), and a conduit for recycling the uncondensed gases to the reactor.

[0094] The uncondensed gas stream which is not recirculated as synthesis cycle gas is discharged from the methanol synthesis unit as gaseous stream (IV) and optionally conducted to stage (f).

[0095] In the stage (c) of the method, the crude methanol stream (III) condensed out in stage (b) and discharged from the methanol synthesis unit is expanded to a pressure of 0.1 to 2 MPa absolute pressure in an expansion unit, and an expanded gas (V) comprising carbon dioxide and methane and a degassed crude methanol stream (VI) rich in methanol and water are obtained. The expansion is typically achieved in a device in which the gas phase and the liquid phase can be efficiently separated from each other. Typically, the device is a liquid separator. Suitable equipment for this purpose is known to those skilled in the art.

[0096] The expansion is preferably carried out to a pressure of ≥ 0.2 MPa absolute and more preferably ≥ 0.4 MPa absolute, and preferably to a pressure of ≤ 1.5 MPa absolute and more preferably ≤ 1 MPa absolute. Typically, the temperature of the expanded mixture is 0°C to 150°C, preferably ≥ 10°C and more preferably ≥ 20°C, and preferably ≤ 120°C and more preferably ≤ 60°C.

[0097] The degassed crude methanol stream (VI) has been further enriched with methanol and water and also comprises additional components depending on the solubility and vapor pressure of the components present in the crude methanol stream (III), for example gases dissolved therein, such as hydrogen, carbon monoxide, carbon dioxide, dimethyl ether, methane or components with a higher boiling point than methanol.

[0098] The expanded gas (V) comprising carbon dioxide and methane is preferably directed to stage (f). Alternatively, however, the expanded gas (V) can also be discharged from the methanol synthesis plant and, for example, utilized thermally or disposed of in some other way. However, it is preferably used in the methanol synthesis plant as a feed stream for the combustion unit in stage (f).

[0099] In stage (d) of the process, the degassed crude methanol stream (VI) obtained in stage (c) is separated by distillation in a distillation apparatus into a low-boiling stream (VII) comprising carbon dioxide and dimethyl ether and a bottom stream (VIII) rich in methanol and water.

[0100] The low boiling stream (VII) separated by distillation mainly comprises carbon dioxide and dimethyl ether as the low boiling substance separated, and based on the composition of the crude methanol stream (VI) of degassing, also comprises other low boiling substances (for example methane), and according to the separation performance and the operating mode of distilling apparatus, also comprises methanol or a component (for example water) with a higher boiling point than methanol. The low boiling stream (VII) comprising carbon dioxide and dimethyl ether is preferably directed to the stage (f) as well. If expansion gas (V) is directed to the combustion unit in the stage (f) and therefore directly reused in the methanol synthesis equipment, the low boiling stream (VII) also can be discharged from the methanol synthesis equipment alternatively and for example thermally utilized or disposed of in some other manner. However, it is preferably used as the feed stream of the combustion unit in the stage (f) in the methanol synthesis equipment.

[0101] The methanol- and water-rich bottom stream (VIII) additionally comprises further components having a higher boiling point than methanol, for example by-products having a higher boiling point than methanol from the methanol synthesis, such as acetic acid, higher alcohols, higher esters, higher ethers or alkanes.

[0102] To obtain methanol, finally, in stage (e), the water-comprising high boiler stream (IX) is separated from the bottom stream (VIII) obtained in stage (d) in a further distillation apparatus and methanol is obtained as stream (X) by distillation.

[0103] The high boiler stream (IX) comprises water and also further components having a higher boiling point than methanol, for example by-products having a higher boiling point than methanol from methanol synthesis, for example acetic acid, higher alcohols, higher esters, higher ethers or paraffins. For example, this stream can be sent to wastewater treatment.

[0104] Via stream (X), methanol can be obtained in a high purity of ≥95% by weight, preferably ≥98% by weight and more preferably ≥99% by weight. Accompanying substances include residual amounts of low boilers and high boilers which have not been completely removed by distillation, in particular water, and also very small amounts of ethanol, esters and ethers.

[0105] When the reaction mixture is gradually post-treated to obtain methanol as stream (X), streams (IV), (V) and (VII) are separated. However, these still contain valuable components, such as carbon monoxide, carbon dioxide, methane and dimethyl ether. Its purpose is mainly to physically reuse the carbon in these valuable components for further synthesis of methanol while avoiding carbon dioxide emissions. Through additional method steps (f), (g) and (h), the carbon in the valuable components can be specifically reused for further synthesis of methanol, i.e., to produce other valuable products, and to avoid carbon dioxide emissions from methanol synthesis at the same time. Steps (f), (g) and (h) are described in detail in WO 2020 / 048809A1.

[0106] pass Figures 1 to 10 The present invention will be described in more detail. The accompanying drawings show:

[0107] Figure 1 : Non-inventive procedure for heating the feed stream B using burner 4, wherein after cooling in heat exchanger HE8, substream A-2 comprising DME is fed to a separate tray of reactor 2 to cool reactor 2.

[0108] Figure 2 : The procedure of the invention, wherein after cooling in the heat exchanger HE8, the DME-containing substream A-2 is fed to a separate tray of the olefin fixed bed reactor 2 to cool the reactor 2.

[0109] Figure 3 : The procedure of the invention, wherein after cooling in the heat exchanger HE8, the DME-containing substream A-2 is fed to a separate tray of the olefin fixed bed reactor 2 to cool the reactor 2. At the same time, the electric heat exchanger EH1 is used to increase the temperature difference in the device HE4 and thus significantly reduce the heat transfer area.

[0110] Figure 4 : Non-inventive procedure for heating feed stream B using burner 4, wherein substream A-2 comprising DME is fed into a separate tray of olefin fixed bed reactor 2 without cooling, and reactor 2 is operated isothermally.

[0111] Figure 5 : The procedure of the invention, wherein the substream A-2 comprising DME is fed without cooling to a separate tray of an olefin fixed bed reactor 2, and the reactor 2 is operated isothermally.

[0112] Figure 6 : The procedure of the invention, in which the substream A-2 comprising DME is fed without cooling to a separate tray of the olefin fixed bed reactor 2, and the reactor 2 is operated isothermally. At the same time, the electric heat exchanger EH1 is used to increase the temperature difference in the device HE4 and thus significantly reduce the heat transfer area.

[0113] Figure 7 : Non-inventive procedure for heating feed stream B using burner 4, wherein methanol substream A1-2 is fed into a separate tray of olefin fixed bed reactor 2 to cool reactor 2.

[0114] Figure 8 : The procedure of the present invention, wherein the methanol substream A1-2 is fed into a separate tray of the olefin fixed bed reactor 2 to cool the reactor 2.

[0115] Fig. 9: The procedure of the invention, wherein the methanol substream A1-2 is fed to a separate tray of the olefin fixed bed reactor 2 to cool the reactor 2. At the same time, the electric heat exchanger EH1 is used to increase the temperature difference in the unit HE4 and thus significantly reduce the heat transfer area.

[0116] Fig.10 : Non-inventive procedure without DME pre-reactor using burner 4 to heat feed stream B, wherein DME substream A-2 is fed to a separate tray of olefin fixed bed reactor 2 to cool reactor 2.

[0117] Fig.11 : The procedure of the present invention without a DME prereactor, wherein the DME substream A-2 is fed to a separate tray of the olefin fixed bed reactor 2 to cool the reactor 2.

[0118] Fig.12 : The procedure of the invention without DME prereactor, in which the DME substream A-2 is fed to a separate tray of the olefin fixed bed reactor 2 to cool the reactor 2. At the same time, the electric heat exchanger EH1 is used to increase the temperature difference in the unit HE4 and thus significantly reduce the heat transfer area.

[0119] Fig.13 : A non-inventive procedure without a DME pre-reactor using a burner 4 to heat the feed stream B, wherein the DME substream A-2 is fed to a separate tray of an olefin fixed bed reactor 2 and the reactor 2 is operated isothermally.

[0120] Fig.14 : The procedure of the present invention without a DME prereactor, wherein the DME substream A-2 is fed to a separate tray of an olefin fixed bed reactor 2, and the reactor 2 is operated isothermally.

[0121] Fig.15 : The procedure of the invention without a DME prereactor, in which the DME substream A-2 is fed to a separate tray of the olefin fixed bed reactor 2 and the reactor 2 is operated isothermally. At the same time, the electric heat exchanger EH1 is used to increase the temperature difference in the device HE4 and thus significantly reduce the heat transfer area.

[0122] Reference Symbols List:

[0123] 1 DME pre-reactor

[0124] 2 Olefin Fixed Bed Reactor

[0125] 3. Product gas quenching

[0126] 4 Burner

[0127] 5 Product separation section

[0128] 6 Compressor

[0129] HE1 to HE9 Heat Exchangers

[0130] EH1 Electric Heat Exchanger

[0131] A1 Stream containing methanol

[0132] A1-1, A1-2 Sub-flow of A1

[0133] A Stream containing DME

[0134] A-1, A-2 Substream of A

[0135] B Feed stream containing DME, recycled hydrocarbon and steam to the olefin fixed bed reactor

[0136] D Product gas stream from olefin fixed bed reactor

[0137] F Product gas stream containing hydrocarbons

[0138] G1, G2, G3 water flow

[0139] H1 Hydrocarbon recycle stream

[0140] K Quenching water circulation flow

[0141] P Product hydrocarbon

[0142] W Wastewater Flow

[0143] Q1 to Q12 Heat flow

[0144] Examples

[0145] according to Figures 1 to 15 The program calculates by way of example the heat flows Q1 to Q11 for the production of 60 t / h of propylene with a minimum production of ethylene and butenes.

[0146]

Claims

1. A method for preparing C2-C4 olefins from dimethyl ether with or without methanol, the method comprising the following steps: A) providing a stream A comprising dimethyl ether; B) mixing at least a portion of stream A with at least one hydrocarbon recycle stream R comprising C2-C6 hydrocarbons and a steam stream G2 to obtain a feed stream B; C) heating the feed stream B to a temperature in the range of 430° C. to 500° C. in one or more heat exchangers and feeding it into an olefin fixed bed reactor, wherein the heating can also be carried out before mixing the individual substreams to obtain the feed stream B in step B); D) catalytically converting the feed stream B at a temperature in the range of 430° C. to 520° C. into a product gas stream D comprising C2-C4 olefins, additional C2-C6 hydrocarbons, methanol and water vapor; E) cooling the product gas stream D to a temperature in the range of 170° C. to 220° C. by heat exchange with the feed gas stream B in one or more heat exchangers; F) further cooling the product gas stream D to a temperature in the range of 35° C. to 65° C. by contacting with at least one quench circulation stream K comprising water and condensing water and methanol to obtain a hydrocarbon product gas stream F depleted in water and methanol; G) separating at least one substream G1 of the at least one aqueous quench circulation stream K and heating and evaporating the substream G1 by heat exchange with medium-pressure steam in one or more heat exchangers or by electrical heating to obtain a steam stream G2, and feeding the steam stream G2 into step B); H) separating one or more product streams P comprising C2-C4 olefins from the hydrocarbon product gas stream F and obtaining at least one hydrocarbon recycle stream R comprising C2-C6 hydrocarbons and recycling it to step B).

2. The method according to claim 1, wherein: The second feed gas stream B is heated in step C) without using additional heat generated by the combustion of fossil energy carriers.

3. The method according to claim 2, wherein: The second feed gas stream B is heated in step C) partly by means of an electric heat exchanger.

4. The method according to any one of claims 1 to 3, wherein: The medium pressure vapour stream is at a temperature in the range of 150°C 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, wherein: This medium-pressure steam stream is produced in the methanol synthesis upstream of step A) and / or in the synthesis gas preparation upstream of said methanol synthesis.

6. The method according to any one of claims 1 to 5, wherein: In step G), a substream G1 of the aqueous quench circulation stream is additionally heated by heat exchange with the product gas stream D and evaporated.

7. The method according to any one of claims 1 to 6, wherein: In step G) the substream G1 of the aqueous quench circulation stream is heated by heat exchange with medium-pressure steam to an extent of at least 50%, based on the heat supplied.

8. The method according to any one of claims 1 to 7, wherein: The hydrocarbon recycle stream H1 comprising 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, wherein: Step H) comprises: H1) compressing the hydrocarbon product gas stream F to obtain a product gas stream containing propylene and C4, C5 and C6 + a liquid hydrocarbon stream H11 of hydrocarbons, and a gaseous hydrocarbon stream H12 comprising ethane, ethylene and propylene; H2) separating water from the liquid hydrocarbon stream H11 by phase separation to obtain a liquid hydrocarbon stream H21; H3) separating a stream H31 comprising propylene from the liquid hydrocarbon stream H21 to obtain a stream H31 comprising C4, C5 and C6 + or separating the stream H31 containing propylene and C4 hydrocarbons to obtain a stream H32 containing C4, C5 and C6 + a hydrocarbon stream H32; H4) From the containing C4, C5 and C6 + The hydrocarbon stream H32 contains C6 + a stream H41 of hydrocarbons to obtain a stream H42 comprising C4, C5 and C6 hydrocarbons; stream H41 optionally comprises aromatic C6 hydrocarbons and stream H42 optionally comprises aliphatic C6 hydrocarbons; H5) separating a stream H51 comprising propylene from the gaseous hydrocarbon stream H12 comprising ethane, ethylene and propylene to obtain a stream H52 comprising ethane and ethylene; H6) separating a stream H61 comprising butenes from the stream H42 comprising C4, C5 and C6 hydrocarbons to obtain a stream H62 comprising C5 and C6 hydrocarbons; and / or separating a stream H63 comprising propylene from the stream H31 to obtain a stream H64 comprising butenes; H7) obtaining at least one recycle stream R from one or more streams selected from: a stream H42 comprising C4, C5 and C6 hydrocarbons, a stream H62 comprising C5 and C6 hydrocarbons, a stream H31 comprising propylene, a stream H51 comprising propylene, a stream H63 comprising propylene, a stream H61 comprising butenes, a stream H64 comprising butenes and a stream H52 comprising ethane and ethylene.

10. The method according to any one of claims 1 to 9, wherein: Step A) A feed stream A1 comprising methanol is fed into a dimethyl ether fixed bed reactor and the methanol is catalytically converted into dimethyl ether to obtain a product stream A comprising dimethyl ether, methanol and water vapor.

11. The method according to claim 10, wherein: The methanol fed in step A) is produced in an upstream methanol production comprising the following steps: (a) producing a synthesis gas (II) comprising carbon monoxide, carbon dioxide and hydrogen from a hydrocarbon-containing feedstock (I) in a synthesis gas production unit; (b) feeding the synthesis gas (II) from stage (a) into a methanol synthesis unit and converting it into a reaction mixture comprising methanol, water, carbon monoxide, carbon dioxide, hydrogen, dimethyl ether and methane in the presence of a methanol synthesis catalyst at a temperature of 150° C. to 300° C. and a pressure of 5 to 10 MPa absolute, condensing a crude methanol stream (III) rich in methanol and water from said reaction mixture, and withdrawing the crude methanol stream (III) and a gaseous stream (IV) comprising carbon monoxide, carbon dioxide, hydrogen and methane from the methanol synthesis unit; (c) expanding the crude methanol stream (III) from stage (b) to a pressure of from 0.1 to 2 MPa absolute in an expansion unit and obtaining an expanded gas (V) comprising carbon dioxide and methane and a degassed crude methanol stream (VI) rich in methanol and water; (d) separating by distillation in a distillation apparatus a low-boiling stream (VII) comprising carbon dioxide and dimethyl ether from the degassed crude methanol stream (VI) from stage (d) and obtaining a methanol- and water-rich bottoms stream (VIII); and (e) optionally separating a high-boiling stream (IX) comprising water from the bottom stream (VIII) from stage (d) in a further distillation apparatus and obtaining methanol as stream (X) by distillation.

12. The method according to claim 11, wherein: The methanol preparation further comprises steps (f) to (h): (f) feeding the valuable carbon monoxide, carbon dioxide, dimethyl ether and methane components of stream (IV) and at least one of the two streams (V) and (VII) into a combustion unit and combusting them in the combustion unit with supply of an oxygen-containing gas (XI) having an oxygen content of 30 to 100% by volume to form a flue gas (XII) containing carbon dioxide; (g) separating a carbon dioxide-rich stream (XIV) from the carbon dioxide-containing flue gas (XII) from stage (f) in a carbon dioxide recovery unit to form a waste gas stream (XIII); and (h) recycling the carbon dioxide-rich stream (XIV) separated off in the carbon dioxide recovery unit from stage (g) to the synthesis gas production unit of stage (a) and / or to the methanol synthesis unit of stage (b).

13. The method according to claim 11 or 12, wherein: The medium-pressure steam stream used in step G) of preparing C2-C4 olefins comes from the synthesis gas production unit in step (a) of the methanol preparation and / or from the methanol synthesis unit in step (b) of the methanol preparation.

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