KR20050088206A - Multicomponent sorption bed for the desulfurization of hydrocarbons - Google Patents

Abstract

A novel hydrocarbon feedstream catalyst bed for the desulfurization of a gas or a liquid hydrocarbon feedstream and a process comprising passing a hydrocarbon feedstream over the catalyst bed is descrived. The bed comprises a least two catalysts having different sulfur compound affinities and / or specificities thereby improving the overall amount of sulfur compound removal. The process reduces the sulfur content in a gas hydrocarbon feedstream from up to about 300 ppm to less than about 500 ppb, and in a liquid hydrocarbon feedstream from up to about 3% to less than about 500 ppb.

Description

Multi-component Sorption Bed for Hydrocarbon Desulfurization {MULTICOMPONENT SORPTION BED FOR THE DESULFURIZATION OF HYDROCARBONS}

The present invention relates to a catalyst bed for desulfurization of a hydrocarbon feed stream. These catalyst beds contain two or more catalysts each having an affinity for sulfur-containing compounds. When used in this composite, the catalyst bed was found to significantly reduce the sulfur concentration in the feed stream. The present invention also discloses a method for reducing the sulfur compound concentration in a hydrocarbon feed stream to levels below about 500 ppb.

Hydrocarbon feed streams, such as natural gas (NG), liquefied petroleum gas (LPG) and gasoline, are mostly used as starting materials for many chemical processes that utilize catalysts in one or more reaction stages. However, if such hydrocarbon feed streams also contain sulfur compounds, they are often problematic during chemical processes. These sulfur compounds inactivate the catalyst bed by poisoning the reaction catalyst. Nickel catalysts, which are generally useful for hydrogenation reactions, are particularly sensitive to sulfur poisoning on their active surface. Likewise, many precious metals used in various catalysts are susceptible to sulfur and can be easily poisoned due to the presence of sulfur compounds or sulfur compounds. Poisoning of the catalyst leads to longer reaction times than the desired reaction time, formation of unnecessary side reaction products, reduction in the useful life of the nickel catalyst, and in some cases poor quality of the final product. Therefore, it is advantageous to reduce the sulfur content in the hydrocarbon feedstream prior to reaching the catalyst bed of the chemical process.

However, hydrocarbon feedstreams vary in source of origin. This means that each feed stream contains unique sulfur compounds and different concentrations of pollutants. For example, Table 1 lists some of the sulfur compound species commonly found in natural gas, LPG and gasoline streams. Moreover, the sulfur compound species may depend on the type of source stream as well as the source of the source. In other words, the natural gas feedstream composition produced in Alaska may differ significantly from the natural gas feedstream composition produced in North Russia.

Some sulfur compound species commonly found in hydrocarbon feedstocks Compound species Natural gas LPG Gasoline H ₂ S X X - Carbonyl Sulfide (COS) X - - t-butyl mercaptan X X - Disulfides X X X Dimethyl Sulfide (DMS) X - - Tetrahydrothiophene (THT) X - X C2-C3 mercaptans X X X Thiophene - - X C4 + mercaptans - - X Benzothiophenes - - X Substituted Benzothiophenes - - X Sulfides - - X X indicates presence in the feedstock; -Indicates no presence in the feedstock.

Many other catalysts effective for the removal of sulfur compounds are known in the art. For example, activated carbon has high activity against ethyl mercaptan, manganese oxide is effective for removing dimethyl sulfoxide, and zinc oxide can be used for hydrogen sulfide removal.

Other catalysts known to be effective in the desulfurization process include carbon, copper / zinc oxide, nickel-based adsorbents, nickel oxides, zeolites, molecular sieves and faujasites. In addition, various methods are used to reduce the sulfur concentration in the feed stream. The most commonly used procedure involves applying a hydrogen regeneration step to convert the sulfur compound to H ₂ S and then removing the sulfur compound in a separate step. However, this can be a difficult and time consuming process. Therefore, there is a need for a better method for removing sulfur-containing compounds. However, it will be difficult to find a single catalyst composition that is universally effective in removing almost all sulfur compounds from gas and liquid hydrocarbon streams due to the diversity of specific sulfur compound species present in the feed stream and the concentration of sulfur compounds.

1 is a perspective view of a catalyst bed of a hydrocarbon feedstream desulfurization system in which a catalyst bed is prepared in accordance with the present invention and a selective adsorbent zone is near the inlet and a universal adsorbent zone is near the outlet;

2 is a perspective view of a catalyst bed of a hydrocarbon feedstream desulfurization system in which a catalyst bed is prepared in accordance with the present invention and a universal adsorbent zone is near the inlet and a selective adsorbent zone is near the outlet;

3 is a perspective view of a catalyst bed of a hydrocarbon feed stream desulfurization system in which a catalyst bed is prepared according to the present invention and a universal adsorbent is mixed with a selective adsorbent to form a filter bed.

details

The present invention provides a catalyst bed for use in removing contaminants in a gas or liquid hydrocarbon feedstream. As is known in the art, some of the most common contaminants of these feed streams are hydrogen sulfide, carbonyl sulfide, sulfides, mercaptans, thiophenes, tert-butyl mercaptans, disulfides, dimethyl sulfide, tetrahydrothiophene Sulfur compounds such as, but not limited to, ethyl mercaptan and benzothiophene. Most of these sulfur contaminants have a strong odor, making it difficult to work around processes using feed streams, as well as sulfur being toxic to many catalysts using hydrocarbon starting materials.

As shown in FIG. 1, the hydrocarbon feedstream desulfurization system 10 includes a catalyst bed reactor 12 having an inlet 14 and an outlet 16. This catalyst bed reactor 12 houses a catalyst bed 20. Hydrocarbon feedstream F enters reactor 12 at inlet 14. This hydrocarbon feed stream is brought into contact with the catalyst bed 20 for a predetermined residence time which is determined by the size of the bed 20 and the flow rate of the feed stream.

As is known in the art, catalyst bed 20 may be placed under controlled temperature and pressure. Feedstream F is then discharged from catalyst bed 20 through outlet 16. As feedstream F passes through bed 20, contaminants are removed from the feedstream.

The hydrocarbon feedstream can be supplied as a gas or a liquid. Typical sulfur concentrations in the crude gaseous hydrocarbon feedstream may be up to about 300 ppm and sulfur concentrations in the liquid feedstream may be up to about 3%. The method of the present invention reduces the sulfur concentration to less than about 500 ppb.

Referring again to FIG. 1, the catalyst bed 20 of the present invention contains a first catalyst or universal adsorbent catalyst 22 and a second catalyst or selective adsorbent catalyst 24, each of which has an affinity for sulfur-containing compounds. It is. The first catalyst 24 is located near the inlet 14 of the bed 20. The second catalyst 22 is located near the outlet 16 of the bed 20.

The first or selective adsorbent catalyst 24 is preferably selected based on the specificity of the catalytic material 24 for certain classes of chemical compounds. For example, non-limiting examples of some optional catalytic materials 24 may include copper / zinc catalysts, zinc oxide catalysts, copper / zinc / molybdenum oxide catalysts, nickel alumina, nickel silica, or mixtures thereof. “Selective adsorbent catalyst” as used herein refers to sulfur compounds such as ethyl mercaptan, tert-butyl mercaptan, tetrahydrothiophene at a temperature of about 38 ° C., a pressure of about 15 psig and a feedstream space velocity of at least about 3000 ^{hr −1.} And substances that do not adsorb at least one of dimethyl sulfide. If necessary, a series of adsorbents can be sorted by their relative specificity by increasing the reaction temperature and / or decreasing the space velocity. The greater the temperature gradient between the adsorption of the first sulfur compound and the second sulfur compound, the greater the specificity of the selective adsorbent for the first sulfur compound. Similarly, the larger the space velocity gradient between the adsorption of the first and second sulfur compounds, the greater the specificity of the first sulfur compound for the selective adsorbent.

The second or universal adsorbent catalyst 22 is preferably selected from the group of relative materials capable of adsorbing sulfur components without high specificity. For example, a non-limiting list of some universal adsorbent catalysts includes activated carbon, magnesium oxide, copper / manganese, silver on alumina, nickel silicate, nickel silica / magnesia / alumina, zeolites, molecular sieves, spores, and mixtures thereof. It may be included and has been suggested. As used herein, “universal adsorbent catalyst” refers to ethyl mercaptan, tert-butyl mercaptan, tetrahydrothiophene and dimethylsulfide at a temperature of about 38 ° C., a pressure of about 15 psig and a feedstream space velocity of at least about 3000 ^{hr −1.} It is a substance that adsorbs.

In the embodiment of FIG. 1, when the hydrocarbon feed stream passes through catalyst bed 20, the hydrocarbon first passes over selective adsorbent 24 where the sulfur-containing component of the target is adsorbed by selective adsorbent material 24. The remaining hydrocarbons then pass onto the universal adsorbent 22 where other sulfur-containing components can be retained by the adsorbent material 22. The remaining hydrocarbon is then discharged from the catalyst bed 20.

As shown in the embodiment of FIG. 2, catalyst bed 120 contains a universal adsorbent catalyst 122 located near inlet 114 and a selective adsorbent catalyst 124 located near outlet 116. Depending on the relative position of this alternative universal catalyst 122 and the selective catalyst 124, the hydrocarbon feedstream may first pass over the universal catalyst 122 and then over the selective catalyst 124. If the selective adsorbent catalyst 124 is highly selective, this catalyst will be relatively unaffected by the presence of other sulfur compounds. However, if the selective adsorbent catalyst 124 is affinity for sulfur-containing compounds other than the target compound of the catalyst 124, this arrangement risks making the selective catalyst 124 act as a universal adsorbent in some respects. As a result, the total efficacy of the catalyst bed 120 may be reduced.

3 illustrates another alternative embodiment of catalyst bed 220. In this bed 220, a universal adsorbent catalyst 222 is present in admixture with the selective adsorbent catalyst throughout the length of the catalyst bed 220. As the hydrocarbon feed stream passes over the catalyst bed 220, the selected sulfur-containing compound is mainly adsorbed onto the selective catalyst 224 while the universal catalyst 222 is allowed to adsorb other sulfur-containing compounds. The bed 220 in which the catalysts are mixed is most effective when the catalysts 222 and 224 are affinity for a specific class of sulfur-containing compounds. For example, if the "universal" catalyst mainly adsorbs thiophenes and the "selective" catalyst mainly adsorbs mercaptans, these two classes of sulfur compounds can be removed as the feedstream passes through the mixed bed phase. .

The embodiments of FIGS. 1-3 are illustrated and described using only two catalysts or adsorbents. However, more than one type of catalyst may be mixed to form a "universal adsorbent catalyst" and / or more than one type of catalyst may be mixed to form a "selective adsorbent catalyst".

Also, the embodiments of FIGS. 1-3 are illustrated and described in connection with removing sulfur-containing compounds from hydrocarbon feed streams. However, the choice of catalyst material may vary and this choice may depend on the particular contaminant to be removed from the feedstream.

From the above description, those skilled in the art will be able to devise variations on the features of the present invention. For example, the catalyst bed can be modified with other designs and devices than those illustrated herein. In addition, universal adsorbent catalysts and selective adsorbent catalysts can be optimized depending on the particular hydrocarbon feedstream or contamination mixture. Such and other variations are to be regarded as belonging to the spirit and scope of the appended claims.

The present invention relates to a novel hydrocarbon feedstream catalyst bed effective for desulfurization of gas or liquid hydrocarbon feedstreams. These beds contain two or more catalysts with different sulfur compound affinity and / or specificity to increase the total removal of sulfur compounds. In one embodiment, the catalyst bed of the present invention is arranged to be in primary contact with a first catalyst having greater affinity or greater selectivity for sulfur compounds present in relatively high concentrations in the feed stream. As this feed stream passes over the first catalyst, the sulfur compound of the target is removed to produce a cleaner stream that is reacted with the second catalyst.

Thus the efficiency of the second catalyst is improved because the stream is cleaner when it reaches the second catalyst. In alternative embodiments, the catalysts may be mixed in the catalyst bed. As the feed stream passes over the catalyst bed, the sulfur compounds are adsorbed by the catalyst having the highest affinity for a particular sulfur compound.

The invention also relates to a process for increasing the total removal of sulfur compounds by passing a hydrocarbon feed stream onto a catalyst bed containing two or more catalysts having different sulfur compound affinity and / or specificity. This method reduces the sulfur content in the gaseous hydrocarbon feed stream from up to about 300 ppm to less than about 500 ppb, and reduces the sulfur content in the liquid hydrocarbon feedstream from up to about 3% to less than about 500 ppb.

Claims (19)

(a) selective adsorbent catalysts having affinity for certain classes of chemical compounds; And (b) contains a universal adsorbent catalyst capable of adsorbing hydrocarbon feedstream contaminants without high specificity, A catalyst bed for removing contaminants from a hydrocarbon feed stream in which the selective adsorbent catalyst and the universal adsorbent catalyst are arranged in series to form a catalyst bed. The contaminant of claim 1, wherein the selective adsorbent material is selected from the group consisting of copper / zinc catalyst, zinc oxide catalyst, copper / zinc / molybdenum oxide catalyst, nickel alumina, nickel silica and mixtures thereof. Catalyst bed for removal. The method of claim 1 wherein the universal adsorbent material is selected from the group consisting of activated carbon, magnesium oxide, copper / manganese, silver on alumina, nickel silicate, nickel silica / magnesia / alumina, zeolites, molecular sieves, sporesite and mixtures thereof A catalyst bed for removing contaminants from a hydrocarbon feed stream. The catalyst bed of claim 1 wherein the universal adsorbent catalyst is located near the inlet of the catalyst bed. The catalyst bed of claim 1 wherein the selective adsorbent catalyst is located near the inlet of the catalyst bed. Selective adsorbent catalysts having affinity for certain classes of chemical compounds; And a mixture of universal adsorbent catalysts capable of adsorbing hydrocarbon feedstream contaminants without high specificity. The contaminant of a hydrocarbon feed stream according to claim 6, wherein the selective adsorbent material is selected from the group consisting of copper / zinc catalyst, zinc oxide catalyst, copper / zinc / molybdenum oxide catalyst, nickel alumina, nickel silica and mixtures thereof. Catalyst bed for removal. The method of claim 6 wherein the universal adsorbent material is selected from the group consisting of activated carbon, magnesium oxide, copper / manganese, silver on alumina, nickel silicate, nickel silica / magnesia / alumina, zeolites, molecular sieves, sporesite and mixtures thereof A catalyst bed for removing contaminants from a hydrocarbon feed stream. (a) providing a catalyst bed having an inlet and an outlet and containing a selective adsorbent catalyst and a universal adsorbent catalyst; And (b) introducing a hydrocarbon feed stream into the catalyst bed through the inlet and exiting the catalyst bed through the outlet, leaving the feed stream in the catalyst bed for a predetermined time at a predetermined temperature and pressure; A method for removing contaminants from hydrocarbon feed streams. 10. The method of claim 9, wherein the selective adsorbent material is selected from the group consisting of copper / zinc catalyst, zinc oxide catalyst, copper / zinc / molybdenum oxide catalyst, nickel alumina, nickel silica and mixtures thereof. 10. The method of claim 9, wherein the universal adsorbent material is selected from the group consisting of activated carbon, magnesium oxide, copper / manganese, silver on alumina, nickel silicate, nickel silica / magnesia / alumina, zeolites, molecular sieves, sporesite and mixtures thereof Characterized by being. (a) a selective adsorbent catalyst having affinity for at least one sulfur containing compound; And (b) contains a universal adsorbent catalyst capable of adsorbing sulfur-containing compounds in the hydrocarbon feedstream without high specificity, A catalyst bed for removing sulfur-containing components of a hydrocarbon feed stream, wherein the selective adsorbent catalyst and the universal adsorbent catalyst are arranged in series to form a catalyst bed. 13. The process of claim 12, wherein the selective adsorbent material is selected from the group consisting of copper / zinc catalyst, zinc oxide catalyst, copper / zinc / molybdenum oxide catalyst, nickel alumina, nickel silica and mixtures thereof. Catalyst bed for component removal. 13. The method of claim 12 wherein the universal adsorbent material is selected from the group consisting of activated carbon, magnesium oxide, copper / manganese, silver on alumina, nickel silicate, nickel silica / magnesia / alumina, zeolites, molecular sieves, sporesites and mixtures thereof A catalyst bed for removing sulfur-containing components of a hydrocarbon feed stream. 13. The catalyst bed of claim 12, wherein the universal adsorbent catalyst is located near the inlet of the catalyst bed. 13. The catalyst bed of claim 12, wherein the selective adsorbent catalyst is located near the inlet of the catalyst bed. Selective adsorbent catalysts having affinity for at least one sulfur-containing compound; And a mixture of universal adsorbent catalysts capable of adsorbing sulfur compounds in a hydrocarbon feed stream without high specificity. 18. The process of claim 17, wherein the selective adsorbent material is selected from the group consisting of copper / zinc catalyst, zinc oxide catalyst, copper / zinc / molybdenum oxide catalyst, nickel alumina, nickel silica and mixtures thereof. Catalyst bed for component removal. 18. The process of claim 17 wherein the universal adsorbent material is selected from the group consisting of activated carbon, magnesium oxide, copper / manganese, silver on alumina, nickel silicate, nickel silica / magnesia / alumina, zeolites, molecular sieves, sporesite and mixtures thereof. A catalyst bed for removing sulfur-containing components of a hydrocarbon feed stream.