KR930011063B1 - Process for removing carbonyl sulphide from liquid hydrocarbon feed stocks - Google Patents

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Description

Removal of Carbonyl Sulfide from Liquid Hydrocarbon Feedstocks

The present invention relates to a process for removing sulfur present in the form of carbon oxysulfide or carbonyl sulfide from liquid hydrocarbons. More specifically, the present invention relates to a process for the removal of carbonyl sulfide from a hydrocarbon feed stock containing propylene.

The industrial use of liquid hydrocarbons, especially liquefied olefinic hydrocarbons, has become more and more specialized. As currently developed, this technique utilizes a catalyst that is very effective at converting liquefied hydrocarbon feedstocks into end products such as polymers. However, these very effective catalysts are very sensitive to the contaminants found in the hydrocarbon feedstock, in particular sulfur pollutants.

In addition to well-known sulfur compounds such as hydrogen sulfide and mercaptans, hydrocarbon feedstocks usually contain small amounts of carbonyl sulfide (COS). In general, COS is present in the order of only a few hundred ppm by weight. However, these small amounts usually go further than the acceptable limit of acceptable products. Since carbonyl sulfide is almost always produced when carbon, oxygen, and sulfur, or their compounds such as carbon monoxide, carbon disulfide, etc. all at once reach high temperatures, these compounds are in some cases a virgin petroleum fraction. ), But is most often found in hydrocarbon feedstocks obtained from thermal and / or catalytic cracking operations. To some extent, carbonyl sulfide does not react friendly with hydrocarbons and hydrogen sulfide. According to the following publication (Kirkothmer's Encyclopedia of Chemical Technology, Vol. 13, pages 384-386, 1954 edition), carbonyl sulfide reacts slowly with hydrogen alkali metal hydroxides and only hydrolyzes slowly with carbon dioxide and hydrogen sulfide. This relatively unreactive nature of carbonyl sulfide makes it very difficult to remove carbonyl sulfide from petroleum flows by conventional desulfurization techniques.

Even at very low concentrations, the presence of COS often drops the value of olefins for many purposes. For example, high purity olefins are necessary for the satisfactory production of many polymer products, especially those useful as plastics including polymers such as ethylene, propylene and the like. In conclusion, it is indeed necessary to improve the technique for removing COS from hydrocarbons, especially hydrocarbons used for the production of polymers.

Some of the known methods for removing carbon oxysulfide (COS) from a hydrocarbon stream are as follows. In British Patent Specification No. 1,142,239, issued February 5, 1969, the inventors found that propene, or at atmospheric or superatmospheric pressure, on a material containing at least one of oxides of cadmium, zinc, nickel or cobalt supported on a carrier. A method for removing COS from such a gas mixture is provided, which comprises passing a gas mixture in which a unsaturated compound such as propadiene is present in a liquid state. This method is defined as reducing the COS concentration to less than 1 ppm.

U.S. Patent No. 4,290,879 to Woodall et al. Discloses the removal of carbonyl sulfide from propane and other similar liquefied petroleum gas products by mixing untreated liquefied gas with methane and then contacting the liquid mixture with solid potassium hydroxide. Presented. COS concentrations are reduced to less than 1 volume ppm.

In Khelghatian, U. S. Patent No. 3,315, 003 describes that carbonyl sulfide can be effectively removed from gaseous hydrocarbons in general by first liquefying the hydrocarbon and then soda ashing contacting it. The eluent gas must then be dried to remove moisture from it.

Shaw US Pat. No. 3,284,531 describes that COS can be removed by passing fluidized hydrocarbons through a layer of slightly basic anhydrous anion exchange resin.

Hamm, US Pat. No. 3,282,831, describes a method for removing COS from a hydrocarbon stream using an anion exchange resin that is in a hydroxyl cycle and is not fully hydrated.

The problem with purifying olephine, such as propylene, is particularly complicated by the nearly same boiling point of propylene and COS, which makes the removal of COS by fractional distillation unsuitable. As a result, the level of COS impurities in the propylene feedstock is often unacceptably high.

Still another drawback is faced in the methods known to date for the removal of COS from hydrocarbons, especially hydrocarbons used for olefin polymerization. For example, some of the known methods introduce water or other contaminants into the hydrocarbon stream, all of which must be removed by further processing in order to keep the hydrocarbons suitable for use. In addition to any such additional processing, any requirement to use elevated temperatures increases the operating rate substantially and unfavorably.

None of the above methods can reduce the COS content to less than 50 ppm by weight. Accordingly, it is seen that there is a need for a method for reducing the concentration of COS in a hydrocarbon stream to 50 ppm by weight or less.

The present invention relates to a process for removing carbonyl sulfide from a hydrocarbon feedstock, in particular an olefin hydrocarbon feedstock containing propylene. According to the present invention, COS is removed by passing a hydrocarbon feed over an adsorbent material comprising nickel deposited on a support material, where nickel constitutes 40 to 70% by weight of the adsorbent and the nickel is present in metallic nickel. Is present in the form of metallic nickel and nickel oxide to the extent that constitutes from about 35% to about 70% by weight of the total nickel.

The present invention reduces the concentration of carbonyl sulfide in hydrocarbon feeds up to 50 ppm by weight.

The present invention relates to the removal of carbonyl sulfide (COS), often referred to as carbon oxysulfide, from a liquid hydrocarbon stream. Of particular note is the treatment of a liquid hydrocarbon stream comprising olefins in which the stream is subsequently polymerized using a polymerization catalyst. As already indicated, propylene-containing hydrocarbon streams present special problems because the boiling points of propylene and COS are about the same. Although the following inference describes the present invention in terms of treating propylene feed, the present invention generally describes a liquid hydrocarbon stream and in particular an olefin liquid hydrocarbon stream, ie hydrocarbons containing ethylene, propylene, butene or any combination thereof. It should be understood that it can be applied to the processing of flows.

The process of the present invention reduces the COS concentration in the treated hydrocarbon feedstock up to 50 ppm by weight. The original COS concentration may be as high as 1000 ppm by weight or more, depending on the origin of the hydrocarbon feedstock and the method of preparation. Because of the cost and specificity of the present invention, it is desirable to use a less expensive and less complex method to reduce the concentration of COS below 70 ppm prior to treatment with the present invention.

The adsorbent material of the present invention contains nickel deposited on the support material. Silica, silico-alumina, alumina, diatomaceous earth and other similar materials can be used as the support. Nickel must be present as both metallic nickel and nickel oxide. Metallic nickel should comprise 35% to 70% by weight of total nickel. Preferably the adsorbent comprises about 40 to about 70 weight percent of the total nickel and about 30 to about 60 weight percent of the support material.

Nickel may be precipitated on the support by any of several methods well known to those skilled in the art. For example, nickel dissolves nickel nitrate in water and mixes the solution with the support and precipitates the nickel in the form of nickel carbonate, for example, by continuing to wash, dry and calcinate the precipitate. Can be precipitated. The nickel precipitated in this way is then partially reduced by hydrogen to form metallic nickel in an amount of about 35 to 70% by weight of the total amount of nickel deposited, with the remainder being in the form of nickel oxide.

Generally, the size of nickel crystals after reduction is about 10 to about 200 A. The size of the nickel crystals depends on the degree of reduction performed. In fact, as the degree of reduction increases, the crystal size increases but the obtained adsorbent material does not have the desired properties. On the other hand, if the degree of reduction is too low, the crystals still have good dimensions but the amount of nickel useful in this case is too low to ensure successful purification of the feedstock.

The specific surface area of the adsorbent material obtained after reduction is generally 100 to 200 m 2 / g.

The particle size of the adsorbent material depends in particular on the pressure loss allowed in the reactor; It should be appreciated that it is useful to use particulate adsorbent materials. Preferably, the particle size of such materials does not exceed about 3.5 mm, most preferably about 1 to 2.5 mm.

In using recent Ziegler-type catalysts in the production of polypropylene, it is important that the Propylene feedstock should contain less than 50 ppb and preferably less than 30 ppb COS. Feedstock obtained by passing a propylene feedstock on an adsorbent material consisting essentially of about 40 to about 70 weight percent nickel deposited on a support material selected from the group consisting of silica, silico-alumina, alumina, diatomaceous earth, and similar materials. It is unexpectedly found that has a COS content that does not exceed 30 ppb, where nickel is present as both metallic nickel and nickel oxide and metallic nickel accounts for about 35 to 70 weight percent of the total nickel. This result is unexpected because of the degree of purity obtained and the fact that this method can be carried out in the presence or absence of water.

In the production of polypropylene, the liquid hydrocarbon feedstock generally comprises at least 75% by weight of propylene, more specifically 85 to 99% by weight of propylene, and about 1 to 10 ppm of COS. In one embodiment of the invention, the liquid propylene feedstock passes through the adsorbent material at a temperature of about 0 to about 90 ° C. under pressure sufficient to maintain the medium in the liquid phase. The liquid time space velocity (LHSV) used is about 0.1 to about 20, preferably about 0.2 to 15.

The following examples are provided to further illustrate the method of the present invention and do not limit the scope of the present invention.

Example 1

A hydroxyhydrocarbon feedstock containing 99% propylene and having a residual COS content of 2.7 ppm is passed over an adsorbent material consisting of 43.3 wt% silica as the support on which nickel is deposited, where nickel is up to 34 wt%. In the form of NiO and up to 22.7% by weight of metallic Ni.

Prior to reduction, the adsorbent material contains about 49% nickel by weight.

The adsorbent material is finely divided to obtain an average particle size of about 1 mm.

The specific surface area of these materials is 145 m 2 / g.

The above feedstock is passed through the adsorbent material at LHSV of 5 at ambient temperature and at a pressure sufficient to maintain the feedstock in the liquid phase.

The purified feedstock had a COS content of 18 ppb.

Example 2

A liquid hydrocarbon feedstock containing 99% by weight of propylene and having a current COS content of 2.7 ppm is passed over the adsorption material as in Example 1.

The nickel-containing adsorbent material has a nickel content of about 49% by weight. The adsorbent material is finely divided into an average particle size of about 1 mm. The specific surface area of these materials is about 145 m 2 / g.

The feedstock is passed through a nickel containing material under various operating conditions given in the following table (1).

As can be seen from the results, the purified feedstock has a COS content of less than 30 ppm, even when the feed contains water, which is known to be harmful.

TABLE 1

Example 3

Of 95.6% by weight of propylene, a liquid hydrocarbon feed containing C ₄ ⁺ 0.6% by weight of propane and 3.8% by weight and having a water content and different residual COS content of 10ppm or less, the average diameter of the particles is 3.2mm Except that it is passed over an adsorbent as described in Examples 1 and 2. This example is given to illustrate the activity of the catalyst over a long time.

The feedstock is passed under a pressure of 14 bar on a layer containing 2 liters of nickel-containing adsorbent material.

Other operating conditions such as LHSV and temperature layer are shown in the following table (II).

TABLE 2

This example shows that the activity of the catalyst is preserved very high even after 88 days.

Claims (19)

CLAIMS 1. A method for removing carbonyl sulfide from a liquid hydrocarbon feedstock, the method comprising: a) passing a hydrocarbon feedstock through an adsorption material comprising nickel precipitated on a support material, wherein both metallic nickel and nickel oxide are present; b) recovering the liquid hydrocarbon stream having a reduced carbonyl sulfide content. 2. The process of claim 1 wherein said liquid hydrocarbon feedstock is an olefin hydrocarbon feedstock. The method of claim 1, wherein the adsorbent material has a particle size of 3.5 mm or less. The method according to claim 1, wherein the adsorbent material has a specific surface area of 100 to 200 m 2 / g. The method of claim 1 wherein the hydrocarbon feedstock contains at least 75% by weight propylene. 6. The method of claim 5 wherein the adsorbent material comprises 40 to 70 weight percent total nickel and metallic nickel comprises 35 to 70 weight percent of the total nickel. The process according to claim 5, wherein the process is carried out at an LHSV of 0.1 to 20 at a temperature of 0 ° C. to 90 ° C. under pressure sufficient to maintain the feedstock in the liquid phase. 2. The process of claim 1 wherein the recovered hydrocarbon stream has a carbonyl sulfide concentration that does not exceed 50 parts by weight ppb. A method for removing carbonyl sulfide from a liquid hydrocarbon feedstock containing propylene, comprising the steps of: a) nickel precipitated on a support selected from the group consisting of silica, silico-alumina, alumina, diatomaceous earth and any combination thereof Silver is sufficient to reduce the concentration of carbonyl sulfide in the feedstock to a concentration not exceeding 50 ppb, on an adsorbent material consisting of 35 to 70 weight percent metallic nickel and 30 to 65 weight percent nickel oxide. Passing said hydrocarbon feedstock for a period of time and b) recovering a liquid hydrocarbon stream having a reduced carbonyl sulfide content. 10. The method according to claim 9, wherein the adsorbent material has a particle size of 3.5 mm or less. 10. The method according to claim 9, wherein the adsorbent material has a specific surface area of 100 to 200 m 2 / g. 10. The process of claim 9, wherein the hydrocarbon feedstock contains at least 75% by weight propylene. 10. The method of claim 9, wherein the adsorbent material contains 40 to 70 weight percent nickel and 30 to 60 weight percent support material. 10. The process according to claim 9, wherein the process is carried out at an LHSV of 0.1 to 20 at a temperature of 0 ° C to 90 ° C under pressure sufficient to maintain the feedstock in the liquid phase. 10. The process of claim 9, wherein the hydrocarbon feedstock contains at least 95% by weight propylene. A process for removing carbonyl sulfide from a liquid propylene feedstock, comprising: a) 40 to 70 weight percent nickel deposited on a support selected from the group consisting of silica, silico-alumina, and any combination thereof; This nickel comprises 35 to 70% by weight of metallic nickel and 30 to 65% by weight of nickel oxide) and on the adsorbent material to hold the propylene feedstock in the liquid phase at a temperature of 0 ° C to 90 ° C Under sufficient pressure to pass the propylene feedstock at a liquid time-space velocity (LHSV) sufficient to reduce the carbonyl sulfide concentration to a level not exceeding 50 ppb; b) recovering the treated propylene feedstock. 17. The process of claim 16, wherein the original concentration of carbonyl sulfide in the propylene feedstock is 1 to 70 weight ppb. The method of claim 16 wherein the adsorbent material has a particle size of 3.5 mm or less and a specific surface area of 100 to 200 m 2 / g. 17. The method of claim 16, wherein the liquid time-space velocity is 0.1-20.