NZ204032A

NZ204032A - Process for producing tert butyl alkyl ethers

Info

Publication number: NZ204032A
Application number: NZ204032A
Authority: NZ
Inventors: Maglie B De
Original assignee: Snam Progetti
Priority date: 1982-05-20
Filing date: 1983-04-28
Publication date: 1985-04-30
Also published as: GB2121407A; DD209803A5; DE3318301A1; TR21617A; NL8301819A; MW1883A1; IT1151183B; DK221683A; SE8302577D0; YU110083A; CA1220230A; KR860001854B1; PH19481A; BG37678A3; DK221683D0; IN159788B; FR2527202B1; SE8302577L; BE896787A; FR2527202A1

Abstract

A process for synthesising t-butyl alkyl ethers is combined with a process for isomerising butene-1 and/or butene-2 in order to increase the ether yield. A C4 hydrocarbon feedstock (1) containing isobutene but free of butadiene is reacted (4) with an alkanol (6) and the ether product (5) is separated from residual hydrocarbons (7), (8); the latter are fractionated to separate saturated hydrocarbons (10), (14), from the butene-1 (12) and the butene-2 (15); the butene-1 and/or butene-2 are isomerised (16) to a product (2) containing isobutene which is recycled to reactor (4).

Description

<div class="application article clearfix" id="description"> 2 040 Priority Dste{s): ... .4?. ..... Ccitv£v?s'»« Specification Filed: Class: ... .. tPPftt I Publication Date: ... .^ P. ^Pft1385 .. ■ P.O. Journal, No: ... . \^P?. No.: Date: NEW ZEALAND PATENTS ACT, 1953 Jin r>v*o_ COMPLETE SPECIFICATION PROCESS FOR PRODUCING TERT.BUTYL £LKYL ETHERS *7 We, SNAMPPQGETTI S.p.A., a carrpany organized under the law of the Italian republic of Corso Venezia IS, Milan, Italy hereby declare the invention for which J*3/ we pray that a patent may be granted to m^/us, and the method by which it is to be performed, to be particularly described in and by the following statement: ~ - 1 - (followed by page la) 204032 esSE-ihtifS - le*- This invention relates to a process for producing tert.butyl alkyl ethers. More particularly, the present invention relates to a process for 5 producing tert.butyl methyl ether. Many processes are known in the art for producing tert.butyl alkyl ethers, consisting of reacting isobutene, contained in hydrocarbon streams of various origin and in particular in the scream originating from steam cracking, catalytic cracking or dehydrogenation of -isobutane, 10 with an alcohol, preferably methanol or ethanol, in the presence of an acid ion exchange resin. In this respect, reference can be made to SB patents 1,506,596, 1,506,461, 1,506,312 and 1,505,404. The known processes allow an almost total isobutene conversion, but 15 the other components remain practically unchanged, and cannot therefore be used as such directly as petrol components. The process according to the present invention allows the conversion of part of the components of the hydrocarbon feedstock with 4 carbon atoms, other than isobutene, into tert.butyl alkyl ethers, together 20 with the isobutene originally contained in said feedstock. The process according to the present invention consists of the following stages: 1) Feeding the hydrocarbon feedstock, either free or substantially free of butadiene, to a tert.butyl alkyl ether synthesis 25 section, said section containing a catalyst constituted by an acid ion exchange resin, preferably of the sulphonated divinylbenzene-styrene type. . 2) Reacting the isobutene contained in the hydrocarbon feedstock O V " - r - ■ ':.Cr 2 ^4 0 3 2 _ 2 _ of point 1) with an aliphatic alcohol fed to said synthesis section, the molar ratio of the alcohol to. the isobutene being between 0.9 and 1.3, the reaction product being a tert.butyl alkyl ether. 3) Separating the tert.butyl alkyl ether from the hydrocarbons 5 by distillation either in the same reaction zone or in a separate zone. 4) Fractionation of the residual hydrocarbon feed in two or three stages at a temperature of between 40°C and 130°C and a pressure of between 4 ata and 26 ata, using between 100 and 220 plates to separate the saturated hydrocarbons (butane and isobutane) from the 10 butene-1 and butene-2. 5) Feeding the butene-1 and/or butene-2. and the unseparated saturated components of stage 4) to an isomerisation stage in which the butene-1 and/or butene-2 are partl3r converted into isobutene, to obtain, whatever the starting olefin or the starting mixture, a hydrocarbon 15 fraction containing essentially butene-1, butene-2 and isobutene in which the butene-1/butene-2 molar ratio corresponds practically to thermodynamic equilibrium, whereas the isobutene/linear butene molar ratio lies between 0.6 and 0.3. 6) Separating the hydrocarbon fraction containing butene-1, butene-2 20 ana isobutene from the heavy products. 7) Feeding the hydrocarbon fraction containing butene-1, butene-2 and isobutene, and possibly also part of the heavy and saturated components, to the tert.butyl alkyl ether synthesis section, either directly or after mixing with the hydrocarbon stream which is free or substant- 25 ially free of butadiene. The C hydrocarbon feedstock pobbibly also contains C_ and C components.^ The feedstock normally comprises C3 hydrocarbons, isobutane, isobutene, butene-1, n-butane, trans butene-2, cis butene-2, and C5 hydrocarbons. The C-3 and C5 hydrocarbons are in small quantities, 204032 and the others can be in relative quantities which vary greatly According to its origin. In order to obtain a constant molar ratio between butene-1, butene-2 and isobutene, isomerisation of the butene-1 and/or butene-2 is 5 carried out using a process such as that described in GB patent 1,505,404, with a catalyst based on silicised alumina such as that described in USA patents 4,013,589 and 4,013,590. It is interesting to note that the process according to the present invention enables not only the tert.butyl alkyl ether to be obtained, 10 but possibly also pure butene-1 or alternatively butene-2, which car-be used for purposes other than those mentioned herein. The process according to the present invention is therefore vary versatile, and it has been found that even significant variations in the isobutene content of the stream fed to the synthesis section do not 15 change the operating conditions of said synthesis. The process according to the present invention is illustrated hereinafter in a flon-limiting manner with reference to the scheme of the accompanying figure. In it, (1) indicates the hydrocarbon feedstock free or substantially 20 free of butadiene, (2) the stream from the isomerisation reactor (13) comprising butene-1, butene-2 and isobutene, and a certain quantity of saturated hydrocarbons, (3) the total stream of (1) and (2), (4) the synthesis unit for the tert.butyl methyl ether (MTBE), (5) the MT3E stream, (6) the methanol stream fed to the synthesis section, (7) the 25 fraction substantially free of isobutene, (15) a possible selective hydrogenation stage for the residual butadiene ar.d any acetylenic compounds, (8) the feed stream to the fractionation scction for the saturated hydrocarbons and olefins, (9) the column for separating the 2 04 0 3 2' - 4 - isobutane (10), (11) the column for separating the butene-1 (12), and (13) the column for separating the n-butane (14) from the cis and trans butene-2 (15). The butene-1 stream (12) can be fed to the isomerisation reactor (16) 5 through the line (17), or can be discharged at the required purity through the line (18). (20) represents the hydrogen stream. Table 1 illustrates by way of non-limiting example some experimental operating conditions together with the relative results obtained by the process according to the invention, with reference to Figure 10 using the selective hydrogenation unit (19) and the hydrogen stream (20), but without recycling the butene-1 to the isomerisation zone. TABLE 1. Position I 1 2 3 8 10 12 14 15 20 | j1kg/hr 1% p. | kg/hr \% p. Kg/hr !/o p.. kg/hr % p. kg/hr % p. kg/hr 1 % p. | kg/hr1 | % p. 1 kg/hr1 % p.1 kg/hr % p. H2 1 1 - 1 - - 1 - 14 0.1 14 0.3 - | | - 1 1 1 t I 1 22 100 C3 hydrocarbons 1 1 192 1 I 0.5 176 J 1.9 368 I 0.8 368 1.2 368 . 8.0 - 1 I - ( i 1 - - isobutane j 504 1 1.3 40 | 0.4 544 I,1*2 544 1.8: 516 11.2 28 1 0.2 - i - 1 1 1 - - isobutene .15520 i40.8 2304 | 25.4 17824 '1 37.9 146 0.5 30 0.7 114 | 0.9 1 2 j 0.1 1 1 _ 1 - - butene-1 [15374 1 140.5 1786 | 19.7 17160 1 36.4 16988 57.8 3500 76.1' 12877 1 98.6 1 603 j 24.2 1 I 1 1 ® 1 O'-M - - 1,3-butadiene | 114 I 0.3 - | - 114 1 0.2 - - - - - j - i 1 . 1 . 1 - - n-butane ji 1005 1 2.7 288 j 3.2 1293 1 2,7 1460 5.0 38 0.8 ■ ' 33 I 0*3 1181 | 47.3 j 208 | 2.2i - - trans butene-2 !i 327 7 1 8.6 2285 | 25.2 5562. 1 11.8 5734 13.5 85 1.9 - 1 1 542 j ' 21.7 r 5107 j 55.2| - - cis butene-2 ! | 2016 | 5.3 2128 | 23.4 4144 j 8.8 4144 14.1 47 1.0 - I 1 168' i 6.7 i3929 i 42.5i - - Cj hydrocarbons - 1 _ 74 0.8 .74 0.2 - - , - - ! ~ ' i ! - 1 _ 1 - 1 TOTAL 38002 1 i t '100. c 9081 'lOO.O 47083 'lOO.O 29398 100.0 4598 100.0 13052 'lOO.O 1 2496 1 100. Q '9252 'lOO.O' 22 ^ 100 • i -6 - &0)+0~b3L Table 2 illustrates by way of non-limiting example some experimental operating conditions and the results obtained by the process according to the invention, again with reference to Figure , without using the selective hydrogenation zone (19) but recycling the butene-1 to the isomerisation zone. • • TABLE 2 Position 1 , ' • 2 3 8- 1 10 12 ' 14 1 5 ■ 1 1 '1— 21 kg/hr % p. kg/hr % p. kg/hr % p. kg/h % p. kg/hr % p. kg/hr % p. kg/hr % p. kg/hr % p. kg/hr % p • Cg hytirocarbons 161 0.5 ' 689 • 2.0 850 1.3 850 1.9 850 16.7 - - - - - - ~ ' isobutane 422 1.3 279 0.8 701 1.1 701 1.6 588 11.6 113 0.7 - - • - •• 113 0.3 isobutene 12990 41.0 9023 25.5 22021 32.8 227 0.5 38 0.7 185 - 1.2 4 o.i 185 ■0.5 butene-1 12876 40.6 6994 19.8 19870 29.6 19671 43.7 3262 64.1 15666 97.8 728 19.8 15 0.1 15681 43.3 n-butane 842 2.7 785 2.2 1627 2.4 1627 3.6 63 1.2 53 0.3 1111 30.3 • 400 2.0 453 1.3 trans butene-2 2744 8.6 8951 25.3 11695 17.4 11894 26.4 177 3.5 - 1717 ' 46.7 10000 49.5 10000 27.6 cis butene-2 1688 5.3 8335 23.6 10023 15.0 10023 22.3 113 2,2 - - 115 3.1 9795 43.4 9795 27.0 Cg hydrocarbons - - 290 C.8 290 0.4 - - t } - J ^ - - - - - - TOTAT. 31731 (lOO.O 35346 100.0 67077 100.0 44993 100.0 5091 100.0 16017 100.0 3675 100.0 20210 100.0 36227 100.0 </div>

Claims

<div class="application article clearfix printTableText" id="claims"> CAGE iSjM 0 j 2 what;^WE CLaim ^ 8_ CLAiiiS; i, —

1. A process for producing tert.butyl alkyl ethers from a hydrocarbon feedstock optionally also containing and components from which the butadiene has previously been separated, consisting of 5 feeding the hydrocarbon feedstock free or substantially free of butadiene to a tert.butyl alkyl ether synthesis section containing a catalyst constituted by an acid ion exchange resin,- — reacting the isobutene contained in the hydrocarbon feedstock with an aliphatic alcohol 10 in order to produce a tert.butyl alkyl ether, and separating the tert.but.yl alkyl ether from the residual hydrocarbons, characterised in that the residual hydrocarbons are subjected to fractionation in two or three stages in order to separate the saturated hydrocarbons from the butene-1 and butene-2, and the butene-1 and/or butene-2 are 15 fed to an isomerisation stage where they are partly converted into isobutene to obtain a hydrocarbon fraction containing essentially butene-1, butene-2 and isobutene together with heavy products, the hydrocarbon fraction containing essentially butene-1, butene-2 and isobutene and cptianaHy part of the heavy and saturated components 20 being fed to the tert.butyl alkyl ether synthesis reaction.

2. A process as claimed in claim 1 or 6, wherein the butene-1, butene -2 and isobutene are present in the hydrocarbon fraction obtained from the isomerisation stage in such proportions that the butene-1/ butene-2 molar ratio corresponds to thermodynamic equilibrium, whereas 25 the isobutene/linear butene molar ratio lies betueen 0.6 and 0.

3. 3 • A process as claxmed in claim 1, 2 or 6, viierein the hydrocarbon1 fraction obtained from the butene-1 and/or butene-2 isomerisation stage is fed to the synthesis section after mixing with the C, 4 or •' "" L. U n uO - 9 - hydrocarbon stream free or substantially free of butadiene.

4. A process as claimed in any one of claims 1 to 3 and 6 wherein the iscmerisaticn stage is effected by feeding only the cis and trans butene-2.

5. A process for producing tert.butyl alkyl ethers substantially as herein described with reference to the acccsroanying drawing.

6. A process as claimed in claim 1 wherein the acid ion exchange resin is a sulphonated divinylbenzene styrene resin. <o By h£&/thetr authorised Agents.^ \ J. PARK & SON'. </div>