DE1195294B - Process for removing alkynes from 1,3-butadiene or isoprene-containing C or C hydrocarbon mixtures - Google Patents

Description

Process for removing alkynes from 1,3-butadiene or isoprene containing C4 or. C5 hydrocarbon mixture in British patent specification 866 395 describes a process for the removal of alkynes, in particular acetylenes, which consists in a liquid C4 fraction containing butadiene by means of trickle technology in the presence of hydrogen under special conditions a hydrogenation catalyst, e.g. B. a palladium catalyst is passed. For the purpose of Avoidance of polymerization is done at a relatively low temperature worked, and an undesirable rise in temperature as a result of during the Heat generated by hydrogenation is generated by cooling either the reaction vessel, whichever contains the catalyst bed, or the starting materials before these are in the reaction vessel get, avoided. Nevertheless, the butadiene losses are mainly due to conversion in saturated C £ hydrocarbons, still considerable.

According to the invention these disadvantages are avoided, it is particularly external cooling is no longer necessary, and yet the alkadiene losses are surprising low, which also results in a low hydrogen consumption.

The process of the invention for removing alkynes from 1,3-butadiene or isoprene-containing C4 or C5 hydrocarbon mixtures by catalytic Hydrogenation over a fixed supported palladium catalyst in the liquid phase is characterized in that the hydrogen-laden liquid hydrocarbon mixture passes over the catalyst in an upward stream.

In general, the method according to the invention is carried out, by making a gaseous hydrocarbon mixture in the presence of hydrogen is to be cleaned, first condensed and the liquid obtained into the Initiate reaction vessel. In some cases it is desirable on the way to the reaction vessel to introduce additional hydrogen into the liquid. Of course are the pressures in the feed lines and in the reaction vessel are at least sufficient, to substantially all of the hydrocarbon mixture to be purified in the liquid To keep state. The pressure to be maintained in the reaction vessel is in general less than 25 kg / cm2 abs .; preferably between 3 and 20 kg / cma abs .; if desired the pressure to which the feed stream is subjected can vary from that im Deviate reaction vessel. It is Z. B. has been found to be in some cases it is preferable to lower the pressure shortly before the starting point material in the Reaction vessel enters, with some gas being evolved, which mainly consists of Hydrogen exists, so that even during the hydrogenation gaseous hydrogen is available.

The temperature to be used depends on the pressure and the composition of the hydrocarbon mixture from; Temperatures above 60 "C are mostly avoided. For practical reasons, the process according to the invention is preferably carried out at room temperature performed without adding or removing heat. Probably because of the large hydrogenation selectivity described above, which means that an alkadiene conversion takes place only to a small extent, the heat generated in the process is proportionate low and can easily be removed from the reaction chamber by direct heat exchange with the surrounding air. When the alkyne concentration in the to be cleaned Hydrocarbon mixture is extraordinarily high, it is beneficial to feel.

The palladium catalyst used in the process of the invention contains palladium in chemically bound and / or in elemental form as active Component, usually in amounts of 0.1 to 5 percent by weight on a support is applied by any known method.

If desired, palladium can be catalytically active in conjunction with others effective metals such as platinum, nickel, cobalt and copper can be used.

In addition, other metals or metal compounds, such as Oxides or salts of iron, aluminum, zinc, cadmium, lead, bismuth, mercury and tallium can be used.

Suitable carriers are all solid materials that are subject to the reaction conditions are essentially inert. In general, macroporous materials are preferred, such as activated carbon, natural silicates, e.g. B. aluminum silicates, carbonates, e.g. B.

Calcium and barium carbonate, clays, pumice stone, active silicon dioxide gel, Silicon dioxide, aluminum oxide, such as alpha or gamma aluminum oxide, and mixtures the oxides of aluminum and silicon.

The carriers can be of any chemical or physical prior to application Treatment, e.g. B. by calcining at a temperature of 500 to 800 "C.

In general, the hydrocarbon mixture to be treated according to the invention consists mainly from hydrocarbons, which have the same carbon number, like the alkadiene components, although other hydrocarbons are also present can. Particularly useful starting materials are butadiene or isoprene mixtures, which are obtained as distillation fractions. Of course you have to focus of catalyst poisons such as thiols and other sulfur compounds in the to be used Hydrocarbon mixture should be low. This also applies to the hydrogen to be used, which can come from any source. The hydrogen can, if desired mixed with other gases which do not adversely affect the hydrogenation.

The concentration of the alkadiene in the hydrocarbon mixture can fluctuate within wide limits. For example, are mixed C4 fractions or Cr fractions with an alkadiene concentration between 20 and 50 percent by weight, which occur in many dehydrogenation plants, but butadiene and isoprene blends with degrees of purity up to 90 percent by weight are also available suitable. In addition, however, the concentration of the alkynes is not of decisive importance Meaning.

When the alkyne content in the hydrocarbon mixture is a few However, in some cases it is advisable to use at least one by volume Part of the hydrogenation product of a second hydrogenation in the manner described above to subdue by adding additional hydrogen to the re-treating Introduces current and so a relatively small amount of hydrogen in the feed stream maintains.

The method of the invention can be exemplified by the following explained.

Example 1 Continuous tests were carried out in which butadiene, which had been obtained as the top fraction from a distillation column and had been condensed in the presence of hydrogen, was used as the starting material. Before flowing into the reaction vessel, which consisted of a vertical tube with a diameter of 20 cm and contained 15 kg of 0.5 weight percent Pd on alumina as catalyst, more hydrogen was added to the butadiene stream to a concentration of 1.3 mole percent. The other working conditions were as follows: LHSV (volume starting material / volume catalyst / h ... ....... 10 height of the catalyst bed, cm ...... 47 condenser temperature, ° C .. ..... .... 25 pressure, kg / cm² abs. .. ........... 5.5 reaction vessel temperature, ° C ................. 27 Pressure, kg / cm2 abs. 8 No cooling of the starting material or the reaction vessel was used. The analysis of the current before and after the hydrogenation can be seen from the table below, in which the abbreviation »ppm« »parts per 1 million« means. Components concentration before i after 1-butene ........ 0.7 1.6 2-butene, trans ... 0.6 0.9 2-butene, cis ..... | 0.1 volume 0.2 volume percent percent Butane .......... 0.2 1,3-butadiene .... 98.3 97.0 Propyne ........ 43 ppm <5 ppm 1-butene-3-yne .... 119 ppm <5 ppm After passing 25,000 kg of butadiene through to the kilogram of catalyst, there was no indication of a decrease in the efficiency of the catalyst.

Example 2 Some small scale experiments were carried out at room temperature performed in which a mixture of C4 hydrocarbons including Butadiene saturated with hydrogen and with flow direction from bottom to top with an LHSV of 10 through a vertical tubular reactor with a length to diameter ratio of 50, which contained the same catalyst as in Example 1.

The other conditions and the results are shown in the following table: Concentration in pressure in kg / cm² abs. at attempt Components saturation with No. Supply drain hydration Feed outflow hydrogen hydrogenation Propyne 160 ppm 73 ppm 1-butene-3-yne 160 ppm 43 ppm 1 # # 8 8 1-butyne 310 pp, 210 ppm 1,3-butadiene 27.9 percent by volume 27.3 percent by volume @ Propyne 775 ppm 200 ppm 1-butene-3-yne 200 ppm 16 ppm 16 5 2 1-butyne 210 ppm 100 ppm 16.5 8 1,3-butadiene 34.2 percent by volume 33.8 percent by volume Propyne 570 ppm 53 ppm 1-butene-3-yne 380 ppm 6 ppm 3 l-butyne 230 ppm 59 ppm 16.5 16.5 1,3-butadiene 34.7 percent by volume 32.0 percent by volume Propyne 505 ppm 190 ppm 1-butene-3-yne 500 ppm <5 ppm 4 # # 18 3.6 1-butyne not detected 1,3-butadiene 45.3 percent by volume j 44.8 percent by volume Propyne 502 ppm 200 ppm 1-butene-3-yne 720 ppm 240 ppm 8.4 8.2 | 1-butyne | 480 ppm | 300 ppm 1,3-butadiene 28.8 percent by volume 28.5 percent by volume Propyne 230 ppm 54 ppm 1-butene-3-yne 105 ppm; 6 ppm 6 l-butyne 170 ppm 58 ppm, 1,3-butadiene 33.1 percent by volume 32.5 percent by volume In experiment no. 3, the hydrocarbon stream was passed twice over the catalyst.

Example 3 An experiment with a long duration was carried out, in which a solution of hydrogen in a C4 hydrocarbon mixture which Contained 36.1 to 36.3 mole percent 1,3-butadiene and 3100 to 3250 ppm l-butene-3-yne, was passed in an upward stream into a vertical reaction vessel (stainless steel pipe, length 45 cm, diameter 2 cm), which contains the same catalyst as used in Example 1 using a temperature of 40 "C, a pressure of 6 at abs., an" hourly liquid space velocity " of 10 and a ratio of hydrogen to starting material of 1.5 mole percent.

On the second day of operation, it contained the hydrogenation product 35.1 mole percent 1,3-butadiene and 184 ppm 1-butene-3-yne (resulting in conversions of 1.9 or 94.3%). The corresponding dates were on the 8th and 15th day of operation 35.4 or

35.3 mole percent 1,3-butadiene (conversion 2.6 and 3.5%) and 338 and 265 ppm 1-butene-3-yne (conversion 89.3 and 9150 / o).

Example 4 A series of laboratory tests on a small scale were carried out Scale carried out. This was a saturated solution of hydrogen in a C4 mixture continuously for 6 hours over the same catalyst as in Example 1, directed.

The working conditions and the complete analysis results are summarized in the following table. Attempt no. 1 2 3 4 5 Off Off Off Off Off End end end end end gang gang gang gang gang gang product product product product product material material material material material conditions H2 mole percent on Aus | | | raw material 0.6 <0.1 1.2 <0.1 1.1 <0.1 1.0 <0.1 1.6 <0.1 Total pressure outlet material, kg / cm3 g ...... 15.5 15.9 17.8 18.0 23.6 Total pressure reactor, kg / cm² g ............... | 15.5 | 4.3 | 4.2 | 3.6 | 3.9 Temperature reactor inlet, ° C .................... | 16 | 19.0 | 17.0 | 17.0 | 25th (Continuation) Attempt no. 1 2 3 4 5 Off Off Off Off Off End End End End End gang gang gang gang gang gang product product product product product material material material material material Reactor outlet temperature, ° C .................... | 19 | 22.5 | 20.5 | 18.0 | 26.5 l / d ratio of the reactor 50 50 50 50 50 LHSV .................. 10 10 10 10 9 composition CO2 + C8H8, weight percent ................ <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 <0.1 < 0.1 <0.1 C3H6, weight percent .... 1.5 1.3 1.6 1.2 2.1 1.1 2.2 1.4 0.2 0.2 l-C4Hs + i-C4H8, weight percent ................ | 24.2 | 25.3 | 16.7 | 16.6 | 16.4 | 16.9 | 17.6 | 18.0 | 44.5 | 45.2 t-2-C4H8, weight percent 22.8 23.5 19.6 20.2 19.4 20.3 21.2 21.7 7.1 7.9 c-2-C4H8, weight percent 15.7 15.4 16.4 17.2 16.2 17.2 18.1 18.6 5.6 5.8 1,3-butadiene by weight percent ................ 33.1 32.0 42.0 41.6 42.4 40.9 37.2 36.3 34.3 32.8 C2H2, ppm ............... <2 <2 <2 <2 <2 <2 <2 <2 Propyne, ppm 230 54 835 210 590 87 660 160 560 80 Propadiene, ppm 130 70 165 70 145 67 145 75 430 310 1,2-butadiene, ppm ......... | 120 | 152 | 670 | 490 | 635 | 510 | 600 | 615 | 2400 | 2200 1-butyne, ppm 170 59 405 245 355 160 430 220 1100 400 1-butene-3-yne, ppm ......... 105 6 520 38 665 10 490 <5 3500 20 2-butyne, ppm ............ <5 <5 160 175 170 200 405 460 20 65 conversion Butadiene,% .............. 2.54 1.81 2.17 2.55 2.88 Propyne,% ................ 76.5 74.9 85.3 75.8 85.7 1-butyne,% ............... 65.3 39.5 54.9 48.8 63.6 1-butene-3-yne,% ........... 94.3 92.7 98.5 99.3 99.4

Claims (1)

Claim: Process for removing alkynes from 1,3-butadiene or isoprene-containing C4 or C5 hydrocarbon mixtures by catalytic hydrogenation on one fixed palladium supported catalyst in the liquid phase, d a d u r c h G It is not noted that the liquid hydrocarbon mixture loaded with hydrogen is used passes over the catalyst in an upward stream. Documents considered: British Patent No. 866 395.