DD209803A5 - PROCESS FOR PREPARING TERT.-BUTYL-ALKYL ETHERS - Google Patents

Abstract

The object of the invention is to provide an improved process with which the transformers of a part of the components of the starting C 4 hydrocarbon mixtures, which are not isobutene, in tert-butyl alkyl ether, together with the isobutene originally contained in the feed stream, allows becomes. According to the invention, the synthesis of tertiary butyl alkyl ethers is combined with a process for isomerizing butene-1 and / or butene-2 to increase the yield of ether; the butene-1 and / or butene-2 is separated from the saturated C 4 hydrocarbons after formation of the tert-butyl alkyl ether and its separation from the remaining C 4 deep stream.

Description

Berlin, 25, 8 · 83 AP C 07 C / 251 077 0 62 479 18

Ve for the production of tert-butyl alkyl ethers application of the invention

The invention relates to a process for the preparation of tert-butyl alkyl ethers, in particular for the preparation of tert-butyl methyl ether.

Characteristic of the known technical solutions

There are numerous processes for preparing tert-butyl alkyl ethers based on the fact that isobutene possibly contained in hydrocarbon streams of various origins, and in particular in the stream obtained from a steam cracking or catalytic cracking plant or isobutane dehydrogenation plant , is reacted with an alcohol, preferably methanol or ethanol in the presence of an acidic ion exchange resin. Reference is made to IT-PS 1 012 686, 1 012 687 and 1 012 690.

The known methods allow almost complete isobutene conversion; but the other components remain virtually unchanged and therefore can not be used immediately.

Object of the invention

The object of the invention is to provide an improved method of converting part of the components to

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in the tert-butyl alkyl ether used together with the isobutene originally contained in the feed stream, the (-hydrocarbon mixtures which are not isobutene, which are used as starting material, are made possible »

Explanation of the essence of the invention

The invention has for its object to find a process technology with which a conversion of C. hydrocarbon mixtures takes place together with isobutene ·

The inventive method consists of the following steps together

1 The C. hydrocarbon feed stream, which is either free or substantially free of butadiene, is fed into a unit for the synthesis of tertiary butyl alkyl ethers, this synthesis unit being filled with a catalyst consisting of an acidic ion exchange resin is, preferably a sulfonated divinylbenzene-styrene resin ·

2. The isobutene contained in the C. hydrocarbon feed stream (mentioned under point 1.) is reacted with an aliphatic alcohol fed into the synthesis unit, the molar ratio of alcohol to isobutene being 0.9 to 1.3 and the reaction product a tertiary butyl alkyl ether.

3 "The tert-butyl alkyl ether is separated from the C. hydrocarbons by distillation, either in the J

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same reaction zone or in a separate zone ·

4. The remainder of the C. hydrocarbon stream is fractionally distilled in two or three stages at a temperature between 50 and 130 C and at a pressure of 4 to 26 bar using 100 to 220 trays to obtain the saturated hydrocarbons ( Butane and isobutane) from butene-1 and butene-2,

The butene-1 and / or butene-2 and the non-separated saturated components of stage 4 are fed into an isomerization stage in which the butene-1 and / or butene-2 are partly rearranged into isobutene, so that they are independent obtained from the starting olefin or mixture a hydrocarbon fraction consisting essentially of butene-1, butene-2 and isobutene, wherein the butene-l / butene-2 molar ratio practically corresponds to the thermodynamic equilibrium, while the molar ratio \ isobutene / linear butenes ranges from 0.3 to 0.6 «

6 · The butene-1, butene-2 and isobutene-containing hydrocarbon fraction according to item 5 · is separated from the heavy products.

7. The hydrocarbon fraction containing butene-1, butene-2 and isobutene and optionally part of the heavy and saturated products, is fed to the synthesis unit tert-butyl-ethers, either directly or after mixing with the C ₄ hydrocarbon stream which is free or substantially free of butadiene "the as _starting}

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material used C. hydrocarbon stream optionally also contains C_ and C ^ components.

The C starting mixture usually comprises C, hydrocarbons, isobutane, isobutene, butene-1, η-butane, trans-butene-2, cis-butene-2 and Cg-Kohlenwaseerstoffe "The Cj and Cg hydrocarbons are in small Quantities available; the ratio of the other components can vary within wide limits, depending on the origin of the mixture.

In order to obtain a constant molar ratio between 8-butene-1, butene-2 and isobutene, the isomerization is carried out using a method as described in IT Patent No. 1,017,878 using a silicon-based or silicon-based catalyst Silica-treated alumina as described in U.S. Patent Nos. 4,013,589 and 4,013,590. '

It is interesting to note that the process of the present invention allows not only the preparation of pure tert-butyl alkyl ether, but optionally also the recovery of pure butene-1 or butene-2, which are used for purposes other than those described herein can "

The process of the invention is therefore highly adaptive and it has been found that even significant changes in the isobutene content of the hydrocarbon stream fed to the synthesis unit or zone do not alter the working conditions for this synthesis. "

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Working Example

The method according to the invention is explained in more detail below with reference to the attached drawing.

In this 1 means the C. hydrocarbon starting mixture which is free or practically free of butadiene, 2 the hydrocarbon stream from the Isoroerisierungsreaktor 13 containing butene-1, 2-butene and isobutene and a certain amount of saturated hydrocarbons; 3 the combined streams 1 and 2; 4 the synthesis unit for the tert-butyl methyl ether (MTBE); 5 the MTBE product stream; Figure 6 shows the methanol stream being fed to the synthesis unit. 7 the C hydrocarbon fraction, which is virtually free of isobutene; 19 an optional zone or unit for selectively hydrogenating residual butadiene and any acetylenic compounds present; 8 the hydrocarbon stream fed to fractional distillation unit 9 for the production of saturated hydrocarbons and olefins; 9 the distillation column for the separation of isobutene 10; 11 the fractionation column for the separation of butene-l 12; and 13 the fractionation column for the separation of n-butane 14 from the stream 15 of cis- and trans-butene-2, which is fed via line 21 to the isomerization reactor 16. "

The butene-1 stream 12 can be passed via the line 17 to the isomerization reactor 16 or can be discharged with the required purity via the line 18 "20 means the hydrogen stream,

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Table I exemplifies some experimental working conditions along with the results obtained by the method of the invention, with reference to the drawing using the selective hydrogenation unit 19 and the hydrogen stream 20, but without recycling the butene-1 into the isomerization zone

Table 1

Hydrocarbon stream 1 kg / h Weight ft 2 kg / h G Jew .- * kg / h 3% by weight 8 kg / h G 0.1 ^H 2 - - - - - - 14 1.2 C, ⁰ -Kohlenwasser- materials 192 0.5 176 1.9 368 0.8 368 1.8 isobutane 604 1.3 40 0.4 544 1.2 544 0.5 isobutene 15620 40.8 2304 25.4 17824 37.9 146 57, 8 Butene-1 15374 40.5 1786 19.7 17160 36.4 16988 - 1,3-butadiene 114 0.3 - - 114 0.2 - 5.0 n-butane 1005 2.7 288 3.2 1293 2.7 1460 19.5 trans-butene-2 3277 8.6 2285 25.2 5562 11.8 5734 14.1 cis-butene-2 2016 5.3 2128 23.4 4144 8.8 4144 - C_-hydrocarbons - - 74 0.8 74 0.2 - 100.0 total 38002 100.0 9081 100.0 47083 100.0 29398

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Table 1 (continued)

Hydrocarbon stream 10 kg / h G 0.3 kg / h 28 33 - 12 weight .2 kg / h 2 14% by weight · Τ-. 15 kg / h weight · .1 20 kg / h% by weight 100 ^H 2 14 8.0 - 114 - - , 9 -__ 603 - '- - - 22 Cj-hydrocarbons ⁰ materials 368 11.2 12877 - _- »6 - 2 - isobutane 516 0.7 - O - 1181 - - - 2 - - isobutene 30 76.1 O .3 542 0 ,1 - .5 - - Butene-1 3500 - 98 168 24 2 8th O - 1,3-butadiene - 0.8 - - - - - - - n-butane 38 1.9 0 47 .3 208 2 - - trans-butene-2 85 1.0 - 21 , 7 5107 55 - - cis-butene-2 47 - - 6 .7 3929 42 - - C ² -C ⁴ hydrocarbons - - - - '- -

Total 4598 100.0 13052 100.0 2496 100.0 9252 100.0 22 100

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Table 2 illustrates by way of example some experimental working conditions and the corresponding results achieved by the method of the invention, again with reference to the drawing, but without the unit 19 for the selective hydrogenation, but with recycling of the butene-1 to the isomerization zone.

Table 2 1 ^ i Ott) Bh oil 2 2.0 3 1.3 kg / h 8th Wt .-% kg / h 0.5 kg / h C 0.8 kg / h C 1.1 850 1.9 hydrocarbon 161 1.3 689 25.5 850 32.8 701 1.6 material stream 422 41.0 279 19.8 701 29.6 227 0.5 C ₃ hydrocarbons 12998 40.6 9023 2.2 22021 2.4 19671 43, 7 isobutane 12876 2.7 6994 25.3 19870 17.4 1627 3.6 isobutene 842 8.6 785 23.6 1627 15.0 11894 26.4 Butene-1 2744 5.3 8951 0.8 11695 0.4 10023 22.3 n-butane 1688 - 8335 100.0 10023 100.0 - - trans-butene-2 - 100.0 290 290 44993 100.0 cis-butene-2 31731 35346 67077 Cc-hydro- ⁰ Fabrics Gesarot

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Table 2 (continued)

IO kg / h wt.% 16.7 12 kg / h G ew. - * kg / h 4 14% by weight 15 kg / h of weight, O -% 21 kg / h wt, -% 0.3 I Hydrocarbon stream 850 11.6 , 728 2 0.5 M (^ Hydrocarbons 588 0.7 113 O »7 - 111 - - 49 - 113 43.3 I isobutane 38 64.1 185 1 .2 1717 0.1 - 48 - 185 1.3 isobutene 3262 1.2 15666 97 ,8th 115 19.8 15 .1 15681 27.6 Butene-1 63 3.5 53 O .3 30.3 400 .0 453 27.0 n-butane 177 2.2 - - 46.7 10000 .5 10000 trans-butene-2 113 - 3.1 9795 .4 9795 cis-butene-2

Cc-hydro- ^D materials

total

100.0 16017 100.0 3675 100.0 20210 100.0 36227 100.0

Claims (4)

invention claim 1. A process for the preparation of tert-butyl alkyl ethers from a C. hydrocarbon starting mixture, which optionally also contains C, - and Cg components and has been separated from the previously butadiene, in which the butadiene-free or practically free C. hydrocarbon starting mixture is fed into a unit for the synthesis of tert-butyl alkyl ethers containing a catalyst in the form of an acidic ion exchange resin, preferably a sulfonated divinylbenzene-styrene resin, with the isobutene contained in the C-hydrocarbon starting mixture an aliphatic alcohol and the resulting tert-butyl alkyl ether is separated from the remaining C. hydrocarbons, characterized in that the remaining C. hydrocarbons by fractional distillation in two or three stages in saturated hydrocarbons and in butene-1 and butene-2 is separated and the latter partly converted into isobutene in an isomerization step elt and the resulting hydrocarbon fraction, which contains essentially butene !, butene-2 and isobutene optionally together with heavy products and saturated components, in the unit for the synthesis of tert-butyl alkyl ethers. 2. The method according to item 1, characterized in that one obtains in the isomerization a hydrocarbon mixture in which the molar ratio of butene-1 to butene-2 corresponds to the thermodynamic equilibrium, while AP C 07 C / 251 077 0 62 479 18 the molar ratio of isobutene to linear butenes is O, 6 to 0.3. 3. Process according to item 1 or 2, characterized in that the hydrocarbon fraction obtained from the isomerization stage is first mixed with the butadiene-free or practically free C. hydrocarbon stream and then fed into the synthesis zone, 4. Method according to one of the preceding points, characterized in that "only the cis- and trans-butene-2 are fed into the isomerization stage" i page drawings