CS219725B1 - Method of preparation of the butene -1 from the butene fraction - Google Patents

Description

The invention deals with the isolation of the distillation of 1-butene from the residual C ₄ -fractions falling off from the production of methyl tert-butyl ether (MTBE) by the treatment consisting in a reduction of the

1,3-butadiene and acetylenes or isobutylene such that the buten-1 obtained by distillation can be used for copolymerization purposes.

The butane-butene fraction from the pyrolysis of hydrocarbons after butadiene extraction is mainly processed into high-octane components of autobenzine or is used in refineries for heating purposes, etc.

Currently, there are several variants of the butane-butene fraction treatment, which mainly consist in the fact that from the original hydrocarbon boiling point ° C

The C ₄ fraction resulting from the pyrolysis of hydrocarbons first extracts butadiene, and the remaining, so-called "depleted C ₄ fraction", which contains isobutylene as the main product, is etherified with methanol to obtain an isobutylene-methanol MTBE adduct which serves predominantly as into a high-octane component of automobile gasoline, and the residual C ₄ -fractions substantially free of isobutene are used for further processing.

The residual C ₄ -fractions comprises a mixture of C ₄ -uhlovodíků which have relatively close boiling points and their isolation distillation is quite difficult, as is evident from the data in Table následjící:

relative volatility isobutane isobutylene butene-11,3-butadiene n-butane

2-trans-butene

2-cis-butene

-11.7 1.20 - 6,9 1.07 - 6,3 1.04 - 4,4 1.00 - 0,5 0.87 +: 0.9 0.85 + '3.7 0.79

A number of processes have been proposed for the preparation of butene-1, the main of which being the preparation of very pure butene-1 by dimerization of ethylene or dehydration of n-butanol. However, these processes use relatively expensive products as starting materials, although the actual production method of these raw materials is not very demanding and does not require a very efficient distillation plant. However, it has now been found that for the production of butene-1 is preferably used as feedstock residual C ₄ -fractions falling off from the production of MTBE, which comprises from 30 to 50 ° / ^o! butene-1 which can be of the residual C ₄ -fractions distillation to obtain insulation of the required purity, when performed by the treatment with the so prepared contains butene-1 as a minor component of a predominantly butanes, which for purposes of polymerization are not harmful.

Process for the preparation of butene-1 from a butane-butene fraction after butadiene extraction falling off from the production of methyl ether terciámího invention resides in the fact that the residual C ₄ -fractions containing at least 35% by weight. % butene-1, optionally 0.1 to 2 wt. % of butadiene and acetylenes and 0.5 to 5 wt. % isobutylene and optionally 0.1 to 2 wt. % methanol, is hydrotreated in a hydrogen stream using an alumina or aluminosilicate catalyst or a metal activated VIII zeolite. or VIII. and VI. buten-1 of at least 90% purity is distilled off.

If it contains the residual C ₄ -fractions methanol, which is received in the distillate in the separation of MTBE, it can be removed either by washing with water, e.g. in a pulsed packed column at 25 ° C and 0.3 MPa, or the distillation, because methanol forms with C _{4 -} Hydrocarbons azeotropic mixture. Depending on the C ₄ -carbon type and the pressure used in the distillation, 10 to 120 grams of hydrocarbon are required to remove 1 g of methanol by distillation. However, the pressure used in the distillation plays a major role, as can be seen from the following table: pressure 10 ^{* 5} Pa methanol% wt.

0.8

1.7

2.6

4.4

6.1

7.6

9.1

With increasing pressure in the distillation column increases the proportion of methanol in the azeotrope _of C ₄ hydrocarbon-methanol.

At lower pressure, the amount of residual methanol in the C ₄ -fractions going over the top of the column after separation of the MTBE is relatively lower and vice versa. This procedure azeotropic distillation -uhlovodíků C ₄ can be separated from the residual C ₄ -fractions unreacted isobutylene and other C ₄ next -uhlovodíků.

Thus e.g. -from residual C ₄ -fractions · after separation of the MTBE obtained via the top of the distillation column and containing about 2.8% methanol and about 1% 'entrapped MTBE is obtained using a pressure distillation in distillation column efficiency about 20 theoretical plates under pressure 0,45 MPa and the temperature at the column head 38 ° C and in the column bottom 110 ° C at a reflux ratio of about 0.5 over the head of the column _C4 -fractions containing about 2.5% methanol and about 1% isobutylene.

After washing, methanol, water, or through a molecular sieve drying the thus treated residual C ₄ -fractions be used after previous hydrotreating hydrogen or directly (no 1,3-butadienj distillation for isolating the butene -1.

Unreacted residual isobutylene in the range of 0.5 to 5% w / w. however, it can also be separated as an adduct with methanol to form MTBE and using a suitable catalyst such as a cation exchanger from a sulfonated styrene-divinylbenzene copolymer or H ₂ SO ₄ . H ₃ PO ₄ or aluminosilicate, zeolite and the like.

Removal of residual 1,3-butadiene and acetylenes such as vinylacetylene and ethylacetylene in particular may be accomplished by the treatment of the hydrogenation that can be included either before the treatment C ₄ -fractions with methanol or hydrotreated residual C ₄ -fractions falling off from the MTBE process, or may be subjected buten-1 hydrotreatment buten-1 concentrate or buten-1 distillation. The residual C ₄ -fractions falling off from the production of MTBE as a main component contains butene-1 and a variable amount of unreacted isobutylene, the content ranges from 0.5 to 5% by weight. depending on the operating conditions and the activity of the catalyst used in the process of etherification of the butane-butene fraction, preferably in the range of 1 to 2 wt.

If the default butane-butene fraction was subjected to etherification before hydrotreating, the residual C ₄ -fractions contains 0.5-2% by weight. 1,3-butadiene and 0.1-1.5% acetylenes. These contaminants are removed from residual C ₄ -fractions hydrotreating in a stream of H ₂ at low temperature and pressure, preferably in the liquid phase, with selectively hydrogenated 1,3-butadiene and acetylenes while other _C4 -uhlovodíky varies slightly. While this hydrotreating process is partially residual to the hydrogen residue

The _4- fractionation or isomerization of butene-1 according to the nature of the catalyst used and the operating conditions used, whereby the butene-1 content of the hydrotreated butane-butene fraction is somewhat reduced, but care must be taken to minimize these losses.

The isomerization of butene-1 can be limited by carrying out the hydrotreating at a low temperature and without excess hydrogen. Kinetic tests have shown that the isomerisation rate constant can be up to 30 times lower than that of diolefins, while the olefin hydrogenation is negligible.

The conversion of 1,3-butadiene was found to follow the following scheme:

buten-l

1,3-butadiene-butene-2 and indicates the use of low temperature in hydrotreating. The catalyst used is no less important in hydrotreating. A catalyst comprising metals VIII is suitable for this purpose. or VI. and VIII. groups of the periodic system deposited on alumina or aluminosilicate or zeolite, in particular 0.1 to 0.5% Pd on Al ₂ O ₃ or aluminosilicate. However, it is also possible to use Ni on Al ₂ O ₃ or Ni - W - Al ₂ O ₃ and the like. The catalyst may be used in oxidic or sulphide form.

Hydrofinishing can be either residual C ₄ -fractions falling off from the production of MTBE and 1-butene concentrate, as seen from the values given in the table:

po hydrog. butene-1 after hydrogen.

refining conc. refining

Catalyst Pd-Al ₂ O ₃ Pd — A1 ₂ O ₃ prac. conditions: temperature ° C 70 50 pressure MPa 0.9 0.9 mol. H ₂ / C ₄ H ₆ ratio 0.5 1.0 Product composition: isobutane% wt. 8.5 8.9 9.6 10.0 n-butane% wt. 16,9 17,8 15.1 18.4 butene-1 wt. 39.7 36.1 70,5 66,4 trans-butene-2 wt. 19,5 22,1 1,1 2,1 cis-butene-2 wt 11,4 12,7 0,1 0,8 isobutylene% wt. 2,5 2,4 2,7 2,3 1,3-butadiene wt. 1.0 50 ppm 0.7 40 ppm acetylenes% wt. 0.5 50 ppm 0.2 40 ppm

Residual 1,3-butadiene can be removed selectively by hydrogenation refining at 25 to 70 ° C, preferably 25 to 40 ° C, and at a molar ratio of hydrogen to C ₄ H ₆ and acetylenes, such that only hydrogenation of butadiene is hydrogenated and acetylenes, while other C ₄ -olefins remained intact and were not hydrogenated or isomerized, or only to a minor extent.

From the above figures, it can be seen that satisfactory results can be obtained if the low molar ratio H ₂ : C ₄ H ₆ is maintained.

The actual distillation isolation of butene-1 from the residual C ₄ -fraction leaving the MTBE production can be carried out using two distillation columns by first preparing the butene-1 concentrate over the top of the first distillation column while concentrating the 2-butenes and n- butane. This butene-1 concentrate contains 65 to 85 wt. butene-1, depending on the yield chosen for the distillation and the butene-1 content of the starting material. The butene-1 concentrate is fed to a second distillation column, where isobutane is largely separated from the top of the column and 90-99% of butene-1 is obtained from the bottom of the column, which can optionally be purified prior to polymerization, molecular sieves or distillation etc. .

Butene-1, which contains minor amounts of n-butane and isobutylene, is suitable for the co-product

C ₄ fraction after butadiene extraction Residual C ₄ fraction falling off MTBE Residual C ₄ fraction after hydrogen. butene-1 concentrate refining

2-butene concentrate isobutane concentrate butene-1 approx. 98%

The isobutane concentrate can be used, for example, to recover butene-1 or isobutane to prepare a catalyst for the polymerization of ethylene and the like.

However, it is possible to select at a distillation · isolation of 1-butene from the residual C ₄ -fractions process such that over the head of the column afforded 1-butene with isobutane concentrate containing a lower content than 90% by weight. butene-1 and used directly as a product for copolymerization with ethylene.

butanes for this purpose do not matter.

However, the butene-1 distillation isolation can also be accomplished by first distilling isobutane through the top of the column and passing the residue to a second distillation column to obtain 90-95% butene-1 over the top of the column while leaving the mixture at the bottom. 2-butenes and n-butane.

Selection of individual variants distillation isolation of the butene-1 is "inter alia on the desired yield of butene-1 starting from the residual C ₄ -fractions and on its purity.

The following table summarizes the product yields of the butane-butene fraction from hydrocarbon pyrolysis:

to yield C ₄ -fractions wt%.

100 ALIGN!

30.8

24.2

8.3

22.5

Example 1

The residual C ₄ fraction resulting from MTBE production was hydrotreated using a catalyst containing 0.4% Pd to Al ₂ O ₃ in a stream of hydrogen at 45 ° C and the product obtained was injected onto a distillation column where butene was collected in front of the head. -1 concentrate containing about 75% butene-1, which was then processed on a second distillation column to 95% butene-1.

The composition of the starting material, intermediates and butene-1 obtained is summarized in the following table:

residual C ₄ -fraction jo hydrog. refining distillation I. distillation II. distillate residue distillate residue yield% wt. 100 ALIGN! 100 ALIGN! 46 • 54 30 70 isobutane% wt. 7.1 8.2 18.9 - 63.3 - n-butane% wt. 16.7 16.4 2.8 35.0 6.9 1.0 butene-1 wt. 43.5 38.5 74.8 5.1 28.7 95.1 isobutylene% wt. 1.5 • 1,4 2.8 0.4 1.1 3.0 trans-butene-2 wt. 18.8 21.8 0.5 40.2 - 0.7 cis-butene-2 wt. 11.6 13.7 0.2 19.3 - 0.2 butadiene-1.3 wt. 0.8 50 ppm - -

The residual C ₄ -fractions falling off from the MTBE process was hydrotreated in a hydrogen stream in an amount which was · chosen so that the stoichiometric ratio required for the hydrogenation of 1,3-butadiene, after which the product containing about 3.5 why. wt. The isobutylene is passed through a column packed with Ostion KS cation exchanger at 70 ° C with the addition of methanol. The refined product was then fed to distillation column I, where the light fractions containing predominantly isobutane were distilled off and at the same time most of the methanol was distilled off. The distillation residue was fed to a second distillation column where over 95% butene-1 was obtained overhead. The composition of the starting material, intermediates and prepared butene-1 is shown in the table:

residual hydrogen. C ₄ -fraction refining adjustment cation exchanger distillation I. distillation II. rain. residue rain. residue yield% wt. 100 ALIGN! 100 ALIGN! 97 15 Dec 85 35 65 isobutane% wt. 8.5 8.6 8.7 58.7 1.1 2.9 0.1 n-butane% wt. 17.4 18.7 18.9 1.3 22.5 0.9 34.0 butene-1 wt. 42.7 39.0 39.9 35.5 39.1 95.0 9.1 isobutylene% wt. 3.5 3.4 1.0 4,5 0.4 1.0 0.2 trans-butene-2 wt. 15.9 17.9 18.1 - 21.4 0.2 32.9 cis-butene-2 wt. 11.4 12.4 13.4 - 15.5 - 23.7 butadiene-1.3 wt. 0.7 50 ppm - - - - - It is therefore possible by distillation isolation after use columns filled cation exchanger or i extrak-

prepare two columns from the residual C ₄ fraction resulting from MTBE butene-1 purity min. 95% or more, the composition of the starting material being an important factor affecting the purity of the buten-1 distilled. It is preferred that the initial residual C ₄ -fractions not contain isobutylene, or only in small amounts, otherwise it is necessary to include still further reduction of isobutylene content to a value of preferably 1 to 2 wt.%, Which can be achieved stopper or by the treatment of sulfuric acid on the catalyst based on aluminosilicates, zeolites or phosphoric acid, etc. The second important factor is to reduce the content of 1,3-butadiene and acetylene below 50 ppm, which is achieved by hydrotreating using highly active alumina catalysts or zeolites containing metals VIII. or VIII. and VI. periodic system.

Claims (1)

Process for preparing 1-butene from a butane-butene fraction after butadiene extraction falling off from the production metylterciárního ether, wherein the residual C ₄ -fractions containing at least 35% by weight. % butene-1, optionally 0.1 to 2 wt. % of butadiene and acetylenes and 0.5 to 5 wt. isobutylene, the hydrogenation of the invention is refined in a stream of hydrogen using an alumina or aluminosilicate or zeolite activated metal catalyst VIII. or VIII. and VI. buten-1 purity of at least 90% and higher therefrom.