WO2014044385A1

WO2014044385A1 - Method for producing acetylene and/or ethylene

Info

Publication number: WO2014044385A1
Application number: PCT/EP2013/002807
Authority: WO
Inventors: Nicole SCHÖDEL; Volker Göke; Harald SCHMADERER; Christina KUTH
Original assignee: Linde Aktiengesellschaft
Priority date: 2012-09-20
Filing date: 2013-09-18
Publication date: 2014-03-27

Abstract

The invention relates to a method for producing unsaturated hydrocarbons having two carbons, in particular for producing acetylene and/or ethylene, said method having the following steps: producing an acetylene-containing product stream (P) in a reactor (100), separating a C1 stream and an acetylene-containing C2 stream from said product stream (P), and optionally hydrogenating said C2 stream in order to produce ethylene. According to the invention, the C1 stream is divided at least into a first and optionally a second and/or third partial stream (T, Τ', T"), said first partial stream (T) being fed to a methanation unit (210) in which CO is reacted with H₂ to form CH₄ and H₂O, said second partial stream (Τ') being mixed with H₂O in a reactor for adjusting a CO/H₂ ratio according to CO + H₂O -> CO₂ + H₂ in the second partial stream (T), and said third partial stream (T") being fed to a pressure swing adsorption device (211) in which hydrogen is separated from the third partial stream (T").

Description

description

Process for the preparation of acetylene and / or ethylene The invention relates to a process for the preparation of unsaturated

Hydrocarbons with two carbons.

For the production of ethylene from methane is usually first acetylene from methane z. B. produced in a thermal process or otherwise, and then hydrogenated acetylene selectively to ethylene. The said thermal process can, for. B. in a burner (eg BASF process according to DE 875 198) or a H ₂ - plasma (arc process) are performed.

Within the product gas treatment of such acetylene processes after partial oxidation, H ₂ and CO and methane occur in different compositions. In known processes, such a mixture of H ₂ , CO and CH ₄ is upgraded by downstream reactions. In this process, a CO / H ₂ mixture (synthesis gas) or maximized hydrogen is regularly obtained as the sole additional value product (C0 ₂ is not considered a value product in this context).

However, such by-products can not be fully utilized in terms of material or energy at every location.

On this basis, the present invention is therefore based on the problem to provide an alternative method of the type mentioned, which is improved in terms of the utilization of such by-products.

This problem is solved by a method having the features of claim 1. Thereafter, the inventive method for the production of unsaturated

Hydrocarbons having two carbons the steps on: generating an acetylene-containing product stream in a reactor, wherein in particular a feed gas comprising methane and 0 ₂ in the reactor to produce the acetylene (C ₂ H ₂ ) containing product stream is provided, in particular the product stream in a thermal Process (including, for example, an oxidation of methane), especially in the presence of a catalyst, separating a C1 stream and an acetylene-containing C2 stream from that product stream, and in particular hydrogenating the C2 stream to produce ethylene, the C1 stream or a first substream of the C1 Is stream methanated, so it contained CO and H ₂ to CH ₄ and H ₂ 0 is reacted. Such produced CH ₄ is then returned to the reactor (recycle).

Thus, a 1-product process can be realized with advantage; ie, the possibly unusable by-products H ₂ and CO are made available again as raw material through the methanation.

Furthermore, the C1 stream in addition to the first partial stream (or alternatively thereto) can be divided into a second and / or third partial stream, preferably the second partial stream for adjusting a CO / H ₂ ratio in the second partial stream in a WGS reactor H ₂ 0 is mixed to convert CO and H ₂ 0 in C0 ₂ and H ₂ , and wherein preferably the said third partial stream is fed to a pressure swing adsorption device in which H _{2 is separated} from the third partial stream. Preferably, the acetylene-containing product gas stream after the production of the

Acetylene quenched (cooled), preferably by applying the product gas stream with oil. Possibly. the product gas stream can then be treated with water for further cooling. Then first the heavy components of the product stream, such as

in particular tar and coke, separated from the crude gas contained in the product stream (methane, acetylene, etc.), the cooled product gas stream is preferably subjected to a water wash. The crude gas thus obtained is preferably compressed in a crude gas compressor, preferably to a pressure in the range of 15 bar to 35 bar.

Preferably, the second partial stream generated in said WGS reactor is returned to the crude gas compressor. As a result, in particular, the acetylene contained in the crude gas is diluted for safety reasons. Furthermore, the first substream containing methane and H ₂ O is preferably passed, after passing through the methanation unit, into a methane treatment device in which the methane contained therein is dried, ie, water is separated from the first part stream. The thus obtained (dried) methane is returned to the reactor.

Furthermore, the third partial stream is preferably introduced into a pressure swing adsorption device (PSA) and from this a hydrogen product stream containing hydrogen (H2 concentration greater than or equal to 99.5 mol%) is introduced

Hydrogen intermediate stream containing hydrogen and CO and CH4 (H2 concentration greater than or equal to 80 mol%) and a recycle stream containing CO and CH ₄ withdrawn. In pressure swing adsorption, in the present case CO and CH ₄ from the hydrogen product stream are adsorbed alternately at a process pressure to solids in preferably parallel adsorber vessels and then desorbed at a lower pressure (recycle stream). For purifying the adsorbers, they are preferably purged with a partial stream of the hydrogen product stream which forms said hydrogen intermediate product stream. Preferably, said hydrogen intermediate product stream is subjected to a C2-

Hydrogenation device is fed, in which the C2 stream is hydrogenated, wherein acetylene contained in the C2 stream is reacted to ethylene (The hydrogenation is preferably carried out on a catalyst, which is a group of metal VIII, in particular Pd or Pt, wherein Pd is preferred.

Furthermore, the said recycle stream is preferably recycled to the crude gas compressor.

To produce the acetylene-containing product stream in the aforementioned reactor, the procedures described below are conceivable.

Thereafter, first, a hot combustion gas may be generated at a solid state element disposed in the reactor, and that hot combustion gas may be mixed with unreacted methane in the reactor to produce the acetylene-containing product stream. Due to the solid state element In this case, a defined reaction zone is formed, which is an effective

Cooling downstream of that zone is allowed to prevent a decomposition of the formed acetylene defined. Preferably, said hot combustion gas has a temperature of at least 1800 ° C, preferably at least 2000 ° C, most preferably at least 2200 ° C.

The reactor operated in this way combines in particular two different ones

Reaction time scales. In this case, first preferably from a stoichiometric combustion of methane (or another suitable gas) with oxygen in a first step said hot combustion gas in the reactor on

Produced solid state element and this hot combustion gas preferably mixed with unreacted (ie, not yet reacted in the reactor existing) methane in a second step. As a result of the extremely rapid increase in temperature, the required high concentration of methyl radicals is produced here, which then further reacts via addition to the ethane and subsequent dehydrogenation via ethylene to form acetylene: CH ₃ + CH ₃ -> C ₂ H ₆ -> C ₂ H ₄ + H ₂ -> C ₂ H ₂ + 2H ₂ This process proceeds particularly favorably if a defined residence time distribution (time span) is set from the time of mixing to the said quenching (cooling) of the acetylene-containing product stream (product gas mixture), which is preferably in the range from 1 ms to 100 ms, preferably in the range of 5 ms to 50 ms, most preferably in the range of 10 ms to 20 ms.

The solid state element located in the reactor is particularly preferably formed by a monolith, which preferably consists of silicon carbide or silicon carbide, wherein the solid state element (monolith) preferably at least partially coated with a catalyst for the selective promotion of said oxidation (stoichiometric combustion) or . is provided. The said catalyst may e.g. Platinum and / or rhodium have.

For generating said combustion gas in the reactor, a feed gas is preferably provided in the reactor or its components introduced into the reactor, which contains at least a first gas and oxygen, wherein the first gas is in particular methane, hydrogen or ethane. Prefers the first gas contained in the feed gas is partially and / or completely oxidized on the solid-state element to form the combustion gas, so that molecules of the combustion gas formed therein, in the case of methane (first gas), in particular C0 ₂ and H ₂ 0, their Energy on in the reactor

Methane molecules (unreacted methane) transferred to form methyl radicals.

Here, the solid state element can be designed so that the first gas formed as methane is only partially oxidized (pre-oxidation), wherein the

Combustion gases transfer their energy to the unreacted methane to form methyl radicals. Alternatively, there is the possibility that the first gas (methane) is substantially complete to produce a hot one

Combustion gas is oxidized (pre-oxidation) and (downstream of the

Solid state element) separately methane is introduced into the reactor, which is mixed with the combustion gas formed by the pre-oxidation and thus

Methyl radicals generated to produce acetylene.

In particular, it can be provided in particular that the feed gas for generating the combustion gas is introduced along a flow direction into channels (for example porous monolith) formed in the solid element, which extend from a first end area to a second end area of the solid element opposite the flow direction.

Here, those channels may be loaded only at the first end of the solid state element with the catalyst, so that only a part of the methane

formed first gas at the first end portion with the oxygen and molecules of the combustion gas, in particular C0 ₂ and H ₂ 0, transfer their energy to unreacted methane molecules of the first gas to form methyl radicals. In an alternative embodiment of the invention, in contrast, it is provided that the solid-state element has first and second channels, wherein only the first channels are loaded with the catalyst, so that at the second end portion of the solid-state element hot combustion gas from the first channels and preheated first gas in the form of Methane exits the not loaded with catalyst second channels of the solid state element, wherein the molecules of the Combustion gases transfer their energy to the unreacted methane molecules of the first gas to form methyl radicals.

In a further embodiment of the invention, it is provided that essentially all channels of the solid-state element are loaded along their entire length along the flow direction with the catalyst, so that at the second end region of the solid element substantially all of the combustion gas flue gas, wherein the combustion gas then with separately methane introduced into the reactor (see above) and the molecules of the combustion gas transfer their energy to the (unreacted) methane molecules to form methyl radicals.

Further details and advantages of the invention will be explained by the following description of exemplary embodiments with reference to the figures.

Show it:

Fig. 1 is a block diagram of a method according to the invention for

Production of ethylene; and

Fig. 2 is a block diagram of a method according to the invention

used reactor for the production of acetylene. FIG. 1 shows, on the basis of a block diagram, individual steps that are taken at a

process according to the invention for the production of ethylene can be passed through.

Thereafter, a feed gas E, present in the presence of methane and 0 ₂ , is first provided in the reactor 100 to produce an acetylene (C ₂ H ₂ ) containing product stream.

According to the invention, according to FIG. 2, a solid-state element 101 can be used in at least one part of a reactor 100 for the production of acetylene. Preferably, the solid state element 101 is a monolithic block (monolith for short). This solid state element 101 may be uncoated, partially or be fully functionalized with a catalytically active chemical element or a mixture of several such chemical elements (catalyst). The catalyst may be, for example, platinum and / or rhodium on a monolith 101 of silicon carbide.

The thus formed catalytic acetylene reactor 100 preferably combines two different reaction time scales. In this regard, first a feed gas E comprising a first gas G in the form of methane and 0 _{2 is provided} at an inlet side of the solid state element 101 in the reactor 100, so that the

Solid body member 101 is flown along a flow direction with the feed gas E and a hot combustion gas V is generated, for. by stoichiometric combustion of the first gas G, in particular methane, with the oxygen (pre-oxidation 100a), in which case this hot combustion gas V is mixed with unreacted methane (pyrolysis 100b).

This unreacted methane can also be passed through the solid state element 101, that is, only a portion of the methane introduced into the reactor 100 is oxidized at the monolith 101, with the unreacted portion passing through the solid state element 101

Combustion gas V is converted to methyl radicals. Alternatively, according to Figure 2, an additional stream comprising CH ₄ downstream of the solid state element 101 in the reactor 100 are given (two-stage reactor 100). In this case, first of all, preferably all of the solid element 101 fed methane (first G or feed gas E) is converted into a combustion gas V and this then mixed with the additional methane stream to produce methyl radicals (pyrolysis 100b).

The temperature of the hot combustion gas V is at least above 1800 ° C (see above). Due to the extremely rapid increase in temperature, the required high concentration of methyl radicals is generated here, which then further react via addition to the ethane and subsequent dehydrogenation via ethylene to acetylene.

After mixing (pyrolysis 100b), the resulting acetylene-containing product stream P is quenched 200 with oil within a predefined period of time or oil and subsequent water cooled to suppress further decomposition of acetylene (see Figure 1).

Other reaction products or substances contained in the product stream P include C0 ₂ , CO, H ₂ , H ₂ 0 and hydrocarbons having in particular one, at most two or three (or more) carbon atoms (C1, C2 or C3 fraction). The said

Product stream P is subjected to a water wash 201 after cooling 200. The crude gas R thus obtained is fed to a crude gas compression 202 and to a C0 ₂ wash 203 (eg amine wash). If necessary, separated C0 ₂ can be returned to the reactor 100.

Subsequently, after precooling, a C2 fraction (here

Hydrocarbon compounds having two or less carbon atoms) from a C3 fraction (here, hydrocarbon compounds having three or more

Carbon atoms) and then a C1 fraction (here

Hydrocarbon compounds having one carbon atom) of one

C2 fraction (hydrocarbon compounds having two carbon atoms) separated 207. Refrigeration (cryogenic separation) 205 required for the separation can optionally come from an air separation 206 which extracts oxygen from the air fed to the reactor 100 as a component of the feed gas E.

The separated from the C1 fraction C2 fraction of the product stream P or raw gas R is subjected to a hydrogenation 213 to obtain ethylene according to C ₂ H ₂ + H ₂ -> C ₂ H ₄ . Subsequently, unreacted hydrogen is separated off in a C2 stripping 214 (ie, pressure reduction in a vessel / column, preferably to a pressure in the range of 8 bar to 20 bar, leads to the removal of volatile constituents overhead). Finally, in a C2 separation, ethane is separated from the ethylene (product) and optionally recycled to the reactor 100. The withdrawn during stripping hydrogen H ₂ can be further supplied to the crude gas compression 203.

The C1 fraction obtained from the C1 / C2 separation is compressed 208 and a methanation unit 210 (first substream T), a WGS reactor 209 (second substream T ') and a PSA stage (pressure swing adsorption device) 21 1 (PSA for pressure swing adsorption or pressure swing adsorption) (third substream T ") in which the C1 stream into a hydrogen product stream W containing H ₂ , a hydrogen intermediate stream W containing H ₂ for the hydrogenation of

Acetylene, which is fed to the C2 hydrogenation 213, and a recycle stream

(containing CO and CH ₄ ) W ", which is recycled to the raw gas compressor 202. The WGS reactor 209 (WGS for water gas shift) serves to adjust the CO / H ₂ ratio according to CO + H ₂ O -> C0 ₂ + H ₂ (water gas shift reaction), the resulting stream containing H ₂ , C0 ₂ and CH ₄ in the

Crude compressor 202 is returned. Finally, in the methanation unit 210, CO is reacted with 3H ₂ to give CH ₄ and H ₂ O, with the methane in one

Methane recovery facility 212 is treated, that is, dried and returned to the reactor 100.

With the pre-oxidation (staged methane gas addition) 100a according to FIG. 2, in principle all feed streams can be preheated separately to higher preheating temperatures. This considerably improves the energy balance. As the upper limiting temperature, autocracking of methane is limiting. In contrast, an acetylene burner has disadvantages here, since the flame front moves regularly chaotically and depending on the state, the quench liquid is injected into the flame zone (so that incomplete conversion results) or can take place only comparatively far away from the flame zone (which is too long Residence time with resulting excessive acetylene degradation can cause). Alternatively or additionally, it is also possible to quench by injecting hydrocarbons, it being possible with advantage to obtain further acetylene from those hydrocarbons (for example ethane) (see FIG.

As an alternative to a pre-oxidation 100a of methane, H ₂ can also be obtained from a

Product gas separation (C1 / C2 separation 207 according to Figure 1) of the C1 fraction and ethane from the C2 separation 215 (see Figure 1) of the hydrogenated C2 fraction are pre-oxidized. Both gases have the advantage of higher ignitability compared to the stable methane, that is, they react faster in response to the added oxygen than methane itself. Thus, less feedstock is consumed. Such

Application is conceivable, in particular, for a monolith 101 which is loaded with the catalyst only at the first free end region (entry side) (see above). Optionally, there is always the possibility during the procedure

separated C0 ₂ as a diluent gas in the reactor 100 due. This may be advantageous since the use of the monolith 101 as

Ignition catalyst and the associated use of technically pure

Oxygen as an oxidizing agent to very high temperatures at the outlet side (second free end region) of the solid state element 101 or on the catalyst leads. In order to largely prevent material-damaging influences, it is therefore possible, in particular, for a part of the CO ₂ obtained in an amine wash 203 (cf. FIG. 1) to be returned to the reactor 100. The C0 ₂ serves primarily as a dilution medium. The recycle rate is preferably just chosen so high that material damaging effects on the catalyst in the reactor 100 can be largely excluded.

LIST OF REFERENCE NUMBERS

100 reactor

100a preoxidation

100b pyrolysis

101 solid element / monolith

200 quench (cooling the product stream)

201 water wash

202 crude gas compressor

203 C0 ₂ washing with amines / lye

204 C2 / C3 separation

205 Cryogenic decomposition

206 air separators

207 C1 / C2 separation

208 C1 compression

209 WGS reactor

210 methanation unit

211 Pressure swing adsorption device (PSA)

212 Methane treatment facility (methane recovery)

213 C2 hydrogenation

214 C2 stripping

215 C2 separation

E feed gas

G First gas (methane)

P product stream

R raw gas

T First partial flow

T Second partial flow

T "Third partial flow

w hydrogen product stream

w hydrogen intermediate product stream

W "recycle stream

V combustion gas

Claims

claims

Process for the preparation of ethylene, comprising the steps:

Producing an acetylene-containing product stream (P) in a reactor (100), wherein a feed gas (E) comprising methane and O _{2 is provided} in the reactor (100) to produce the acetylene-containing product stream (P),

Separating a C1 stream and an acetylene-containing C2 stream from that product stream (P),

- Wherein the H ₂ - and CO-containing C 1 stream or a first partial stream (T) of the C 1 stream is fed to a methanation unit (210) in which CO is reacted with H ₂ to CH ₄ and H ₂ O, in such a way produced CH _{4 is} at least partially recycled to the reactor (100).

Method according to claim 1, characterized by

Hydrogenating the acetylene-containing C2 stream to produce ethylene.

A method according to claim 1 or 2, characterized in that the C1 stream is further divided into a second partial flow (T), wherein the second partial flow (Τ ') for setting a CO / H ₂ ratio in the second partial flow (Τ') in a WGS reactor (209) with H ₂ 0 is mixed to CO and H ₂ 0 in C0 ₂ and H ₂ implement.

Method according to one of the preceding claims, characterized

characterized in that the C1 stream is further divided into a third partial flow (T "), the third partial flow (T") being fed to a pressure swing adsorption device (211) in which H ₂ is supplied from the third partial flow (T "). ) is separated.

Method according to one of the preceding claims, characterized

in that the acetylene-containing product stream (P) is cooled (200), in particular by pressurizing the product stream (P) with an oil, according to which, in particular, the product stream (P) is supplied with water for further cooling.

6. The method according to claim 5, characterized in that the cooled product stream (P) of a water wash (201) for producing an acetylene-containing raw gas (R) is subjected.

7. The method according to claim 6, characterized in that the raw gas (R) in a crude gas compressor (202) is compressed, in particular to a pressure in the range of 25 bar to 35 bar.

8. The method according to claims 3 and 7, characterized in that the second partial flow (Τ ') is returned to the crude gas compressor (202). 9. The method according to any one of the preceding claims, characterized

in that the first substream (T) containing methane and H ₂ O after passing through the methanation unit (210) into a

Methane treatment device (212) is passed, in which H ₂ 0 is separated from the methane, wherein the methane is recycled to the reactor (100).

10. The method according to claim 4 or according to one of claims 5 to 9 so far

With reference to claim 4, characterized in that from the third partial flow (T ") in the pressure swing adsorption (211) a

Hydrogen product stream (W) containing hydrogen

Hydrogen intermediate stream (W ^l ) containing hydrogen and

Recycled stream (W ") containing CO and CH _{4 are} generated.

1 1. A method according to claim 10, characterized in that the

Hydrogen intermediate stream (W ') of a C2 hydrogenation means (213) is supplied, in which the C2 stream is hydrogenated, wherein contained in the C2 stream

Acetylene is converted to ethylene.

12. The method according to claims 7 and 10, characterized in that the recycle stream (W ") is returned to the crude gas compressor (202).