DE1111614B - Process for removing organic sulfur compounds from gases containing olefins - Google Patents

Description

Process for removing organic sulfur compounds from olefins containing gases It is known olefins, for example ethylene and propylene, by the catalytic action of aluminum alkyl and / or haloalkyl titanium compounds to polymerize (Belgian patents 533 362 and 534792). in this implementation however, the small amounts that may be present in the starting materials have an effect of acetylenic hydrocarbons and of oxygen-containing compounds, for example CO and C 02, as well as elemental oxygen and water vapor, interfering. It is therefore Process described by which some of these compounds are catalytically hydrogenated can be. To carry out this process, the gases to be treated are with a sufficient amount of hydrogen, which may have to be added, via a catalyst, preferably via a nickel-containing catalyst, directed.

However, there are organic sulfur compounds in the gases used present, this procedure is not readily applicable, since these sulfur compounds the activity of the hydrogenation catalyst used after a relatively short time Weaken operating time so that a sufficient hydrogenation of the above Acetylene hydrocarbons and oxygen-containing compounds are no longer guaranteed is. To remove the sulfur compounds from these gases is the application of fine cleaning compound because of the high concentration of olefin compounds and the Presence of acetylene hydrocarbons unsuitable. Other methods too, for example Extraction processes do not produce sufficient results, especially with longer periods of operation Removal of the sulfur compounds and are because of high operating and investment costs uneconomical.

It has been found that the removal of organic sulfur compounds from gases containing olefins, which are used as starting material for catalytic polymerization of the olefins contained therein and their content of organically bound sulfur is below 10g / 100Nm3, preferably below 5g / 100Nm3, with very favorable results can be carried out if these gases have been removed in a known manner of the sulfur optionally present in the form of hydrogen sulfide up to a content of 1 g / 100 Nm3 for the hydrogenation of the organic sulfur compounds at temperatures of 200 to 6000 C, preferably 300 to 5000 C, at normal or elevated pressure over known per se, possibly deposited on carrier materials Hydrogenation catalysts are passed, which are made from nickel sulfide or from oxidic, cobalt or nickel-containing molybdenum or tungsten compounds, whereupon one the gases after removal of the hydrogen sulfide formed in a known manner at temperatures between about 2 and 1000 C, preferably about 20 and 600 C, and at normal or increased pressure via one arranged in one or two stages Second pre-cleaning catalyst conducts, which consists of an applied to carrier materials reduced nickel catalyst with a nickel content of over 300/0, preferably 60 to 80o, and possibly also activators, such as magnesium oxide, contains.

The method according to the invention will be explained in more detail using the scheme. According to the figure, the olefin-containing gases, optionally after the addition of hydrogen (1 a), passed over the first pre-cleaning catalyst (I). The one formed in stage 1 Hydrogen sulfide is removed (II). Before flowing through the second pre-cleaning catalyst (III) hydrogen is optionally added again to the gases to be treated (IIIa). After the removal of the organic sulfur compounds, the hydrogenation takes place of the oxygen-containing compounds and acetylenes (IV) present in the treated gases available.

The water formed in this reaction is replaced by potassium hydroxide removed on pumice stone (V). The drying (V) completes the pretreatment of the gases from, which are then fed to further use, in particular to a polymerization can be (VI).

The carrier materials for the pre-cleaning catalyst are kieselguhr, Aluminum oxides or bleaching earths suitable. You can also use mixtures use of such carriers.

According to the method according to the invention, the to be treated Gases first the sulfur present in it in the form of hydrogen sulfide in known Way, for example by passing over lawn iron ore, down to a sulfur content removed from about 1 g / 100 NmS. For the catalytic hydrogenation of the gases in these gases In addition, organic sulfur compounds usually present, it is expedient that the gas not only used for the hydrogenation of the organic sulfur compounds, the Acetylenic hydrocarbons, the oxygen-containing compounds and the elemental Oxygen stoichiometrically necessary amount of hydrogen, but an excess contains. If there is not a sufficient amount of hydrogen in the gases, it must give this a corresponding amount of hydrogen before being passed over the catalyst can be added. The gases are then at temperatures of 200 to 6000 C, preferably 300 to 5000 C, passed over this first pre-cleaning catalyst, the Gas loading of this catalyst 100 to 3000 ViV / h, preferably 500 to 2000 ViV / h, should be.

The pre-cleaning catalyst can be used at elevated pressure or normal pressure.

However, it is expedient to use the pressure under which later the polymerization of the olefinic constituents of the gases to be treated is carried out.

Through the action of the proposed first pre-cleaning catalysts becomes most of the organic sulfur compounds present in these gases if the specified reaction conditions are observed, reduced to hydrogen sulfide.

This hydrogen sulfide is made from the gases that make up the first pre-cleaning catalyst have gone through, removed in a known manner. After this treatment is the sulfur content of the gases used to about 1 g'100 Nm3, preferably less than 1 g / 100 Nm-3, sunk.

However, it has been found necessary to reduce the sulfur content of the for the aforementioned polymerization process serving as starting material gases lower than 0.3 g / 100 Nm. For this purpose, the gases are in a further Process stage at temperatures of 20 to 1000 C, preferably 20 to 600 C, and passed over a reduced nickel catalyst at normal or elevated pressure. To successfully carry out the method according to the invention, reduced Nickel catalysts of any kind can be used in the specified composition. Catalysts obtained by precipitation from nickel salt solutions are particularly advantageous and subsequent reduction. But also Raney nickel or catalysts, obtained by the hydrogenative decomposition of organic nickel compounds, are applicable. The working pressures of this stage correspond to those of the previous one Stage, the gas load should be between 250 and 2500, preferably 500 and 1500V / V / h, lie. Under certain circumstances it can be useful to do another add a small amount of hydrogen.

This second pre-cleaning catalyst can be of the same type in one or two built-up treatment stages for the hydrogenation of the organic sulfur compounds can be used. In the case of one-step Application is made by those emerging from this catalyst Gases still have a sulfur content after removal of the hydrogen sulfide formed from 0.1 to 0.3 g / 100 Nm3. However, there will be a further reduction in the sulfur content aimed at the gases used, it is advantageous to have a two-stage second Apply pre-cleaner. This will decrease the sulfur content of the treated gases Removal of the hydrogen sulfide formed to below 0.1 g / 100 Nm3, for example 10 to 50 mg / 100 Nm3, reduced. Such small amounts of sulfur can, however, the catalyst an optionally downstream further hydrogenation process for removal the oxygen-containing hydrocarbons, the acetylene hydrocarbons and des do not damage elemental oxygen in its activity.

The catalysts used for this hydrogenation process have advantageously a lower nickel content than the second pre-cleaning catalyst.

The nickel content of this hydrogenation catalyst should be below 500/0, preferably 5 to 20,206 / o.

As carrier substances for this catalyst, besides bleaching earth and kieselguhr, aluminum oxide and magnetite are also used. The addition of Activators, such as magnesium compounds, have also been found for this Tried and tested catalyst.

The in this stage by the hydrogenation of the oxygen-containing components and the amount of water vapor formed by the elemental oxygen is known in Way, e.g. B. by solid potassium hydroxide, calcium chloride, deposited on pumice stone Potassium hydroxide, etc. removed.

If the gases used initially contain less than 2 g / 100 Nm3 Sulfur in organic bond, so it is advantageous to eliminate the first pre-cleaning catalyst and the lawn iron ore stage directly, if necessary with prior addition of hydrogen, via the second pre-cleaning catalyst conduct.

The method according to the invention therefore provides the possibility of olefin-containing gases in a particularly advantageous manner from that contained therein to free organically bound sulfur, so as to remove the gases for a subsequent Further use, in particular polymerisation processes of a known type, to prepare.

The olefin concentration in the gases to be treated can be wide Limits can be varied. 100% olefins can be purified in the manner indicated However, cleaning is also possible at a lower concentration, e.g. 80, 60 or 40 ° / o, easily possible.

One method for sulfur purification from olefins is disclosed in U.S. Patent 2236216.

Olefins in predominantly liquid form are evaporated and the vapors at 360 to 4250 C over catalysts consisting of sulphides of the iron group, especially iron sulfide itself. This process used to purify olefinic liquids serves, does not achieve the purity levels required for the purification of olefinic gases should be achieved.

Another sulfur purification process is described in Kirk-Othmer, »Encyclopedie of Chemical Technology ", Vol. 6 (1951), pp. 966/967, paragraph 3, cited. Synthesis gas, produced by enriching hydrogen in water gas, with lux mass nud strongly alkalized iron oxide at 200 to 3000 C. of organic Purified sulfur compounds. The procedure is a way of working that aimed solely at the purification of hydrogen-rich water gas in which no olefins are present.

The procedure is not suitable for an olefin-rich gas. the The invention works independently of the elimination of organic sulfur compounds in olefinic liquids and the fine purification of synthesis gas the possibility of Gases with a high olefin content to an exceptional degree of freedom from sulfur to clean.

Example 1 Propylene, by distillative decomposition from petroleum cracked gas obtained with a propylene content of 98% and small amounts of propane and hydrogen in addition to carbon dioxide and carbonic acid as well as nitrogen was at a temperature of 4500 C passed over a catalyst containing cobalt molybdate. The speed was 750 V / V / h.

Most of the sulfur compounds present in the propylene was converted to hydrogen sulfide (the starting sulfur content of propylene was 6 g / 100 Nm3). The gas then passed through a cold cleaner that was weak alkalized I, uxmaterial contained to remove the hydrogen sulfide formed. The gas then still had a total residual sulfur content of about 1 g, most of it consisted of organic sulfur. The gas was then passed through a 600 / ( Nickel, 30% kieselguhr and 100% magnesium oxide existing nickel precipitation catalyst conducted which has a reduction value, d. H. a content of free nickel on the total nickel, of 85%. The temperature was 50 ° / oC. That still The residual sulfur content present in the propylene could in this way be reduced to about 0.15 g Total sulfur / 100 m can be reduced.

Then the gas was sent through another reactor, in which a reduced one made from 100 / o nickel on aluminum oxide by precipitation Catalyst was present which allowed the hydrogenation of residual amounts of acetylene as well as small amounts of elemental oxygen. The working temperature was about 2000 C. The load was 1000 V / V / h. The propylene possessed after this treatment an oxygen test below 15 ppm. The total sulfur content was below 0.1 g / 100 m3 removed.

In a further experiment a propylene with 9 g of total organic Sulfur used per 100 m3. A small amount of 0.5 per cent of hydrogen was required here added before the first stage and approximately the same amount before the second stage to achieve the desired purity. The one determined after the last stage The degree of purity was in the order of magnitude of the figures above.

Another propylene, which, however, only has a propylene content of 90 ore, the remainder preferably contained propane, along with small amounts of other compounds and the sulfur content of which was 7 g / 100 m 3 was purified as above. Of the The residual sulfur content was 0.1 g'100 m3.

Example 2 Propylene with 4 g, preferably from organic sulfur compounds existing impurities were at a pressure of 15 at over a cobalt molybdate containing catalyst passed. Before this, 0.4 percent by volume of hydrogen was added.

The resulting hydrogen sulfide was by means of iron oxide mass the same pressure removed and the gas then, as described in Example 1, over a catalyst consisting of nickel, diatomaceous earth, magnesium oxide with a nickel content of 72% and a reduction value, i.e. a free nickel content of 90% on all of the nickel present. The one found after this catalyst The amount of sulfur was less than 0.1 g / 100 m3.

Example 3 Ethylene from the decomposition of refinery gases With a sulfur content of 2 g / 100 ms, cleaning was carried out according to Example 1. The analytically determined residual sulfur content after the first stage was below 0.1 g / 100 m3, the oxygen test below 100 ppm.

Example 4 In a further experiment, instead of the previously used Cobalt molybdate catalyst comes from the second cleaning stage, 600 /, nickel containing catalyst used to convert any remaining amounts of metallic nickel and nickel oxide at normal temperature with hydrogen sulfide Water gas had been treated. This catalyst consisting practically of nickel sulfide was switched to the first stage, the ethylene being 1 percent by volume hydrogen was added. The sulfur in ethylene became 85 D / o in hydrogen sulfide converted, which was removed in a subsequent iron oxide cleaning stage. The further treatment of the gas took place as in Example 3.

Claims (3)

PATENT CLAIMS: 1. Process for removing organic sulfur compounds from gases containing olefins, in particular after catalytic hydrogenation the oxygen-containing compounds also present in these gases and / or Acetylene hydrocarbons and elemental oxygen as the starting material serve for the catalytic polymerization of the olefins contained therein and their Content of organically bound sulfur below 10 g / 100 Nml, -preferably below 5 g / 100 Nm3, is characterized in that these gases according to in a known manner carried out removal of the possibly present in the form of hydrogen sulfide Sulfur up to a content of about 1 g / 100 Nm3 for the hydrogenation of the organic Sulfur compounds at temperatures from 200 to 6000 C, preferably from 300 to 5000 C, at normal or elevated pressure above known, if necessary Carriers precipitated hydrogenation catalysts are passed from Nickel sulfide or from oxidic, cobalt or nickel containing molybdenum or Tungsten compounds exist, after which the gases are carried out in a known manner Removal of the hydrogen sulfide formed at temperatures between about 20 and 1000 C, preferably about 20 and 600 C, and at normal or elevated pressure about one in one or a second pre-cleaning catalyst arranged in two stages conducts, which consists of a reduced nickel catalyst applied to a carrier with a nickel content of over 309%, preferably 60 to 80%, and which optionally also contains activators such as magnesium oxide. 2. The method according to claim 1, characterized in that in the case of gases, which do not contain a sufficient amount of hydrogen, an addition of hydrogen, expedient in such an amount that an excess over that required for hydrogenation of the organic bound sulfur, the oxygen-containing compounds, the acetylene hydrocarbons and the required amount of elemental oxygen is present. 3. The method according to claim 1 and 2, characterized in that at Presence of too little hydrogen before the second pre-cleaning stage a small amount of hydrogen is added again. References considered: U.S. Patent No. 2,236 216; Kirk-Othmer, Encyclopedia of Chemical Technology, 1951, B. 6, p. 966.