Catalyst for selective oxidation of sulphur compounds

Abstract

The present invention is related to a catalyst supported for the selective oxidation of sulphur compounds of the tail gas from the Claus process or streams with an equivalent composition to elemental sulphur or sulphur dioxide (SO.sub.2). It is also the object of the present invention, a process for the preparation of a catalyst of this type, as well as the process of selective oxidation of sulphur compounds to elemental sulphur using the catalyst of the invention, as well as the process of catalytic incineration of the tail gas from the Claus process using the catalyst of the present invention.

Claims

1. A catalyst for selective oxidation or incineration of compounds containing sulphur which are contained in a gas stream, the catalyst consisting of a support material comprising clinoptilolite and a binder or agglomerant in an amount from 0% to 99% by weight with respect to the total weight of the support material; and a catalytically active material consisting of cobalt oxide, which is supported on said support material; the cobalt content in the catalyst being comprised from 0.05% to 2% by weight based on the total weight of the support material; where the catalyst has the following properties: a specific surface area, measured with nitrogen porosimetry according to the ASTM D-3663 standard year 2003, and using the BET method, comprised from 10 to 150 m.sup.2/g; a pore volume, measured with mercury intrusion porosimetry according to ASTM D-4284 standard year 2003, comprised from 0.05 to 10 cc/g; an average pore diameter, measured with mercury intrusion porosimetry according to ASTM D-4284 standard year 2003, comprised from 2 to 50 nm; and a crush strength measured according to the ASTM D-4179 standard year 2002, higher than 29.42 N.

2. The catalyst according to claim 1, wherein the compounds containing sulphur are hydrogen sulphide (H.sub.2S), carbonyl sulphide (COS), carbonyl disulphide (CS.sub.2), or a combination thereof.

3. The catalyst according to claim 1, wherein the specific surface area of the catalyst is from 20 to 140 m.sup.2/g.

4. The catalyst according to claim 1, where the catalytically active material is a mixture of CoO and Co.sub.3O.sub.4 in a ratio by weight of between 10:1 and 1:10.

5. The catalyst according to claim 1, wherein the cobalt content in the catalyst is comprised from 0.1% to 2% by weight based on the total weight of the support material.

6. A catalyst for selective oxidation or incineration of compounds containing sulphur which are contained in a gas stream, the catalyst consisting of a support material comprising clinoptilolite and a binder or agglomerant in an amount from 0% to 99% by weight with respect to the total weight of the support material; and a catalytically active material consisting of cobalt oxide, which is supported on said support material; the cobalt content in the catalyst being comprised from 0.1% to 2% by weight based on the total weight of the support material; where the catalyst has the following properties: a specific surface area, measured with nitrogen porosimetry according to the ASTM D-3663 standard year 2003, and using the BET method, comprised from 10 to 150 m.sup.2/g; a pore volume, measured with mercury intrusion porosimetry according to ASTM D-4284 standard year 2003, comprised from 0.05 to 10 cc/g; an average pore diameter, measured with mercury intrusion porosimetry according to ASTM D-4284 standard year 2003, comprised from 2 to 50 nm; and a crush strength measured according to the ASTM D-4179 standard year 2002, higher than 29.42 N.

7. Process for the preparation of the catalyst defined in claim 1, comprising the impregnation of a solution of a cobalt salt on the surface of a support material; followed by the drying and calcination of the catalyst.

8. Process for the selective oxidation of compounds that contain sulphur, comprising contacting a gas stream containing the sulphur compounds with a gas stream containing oxygen in the presence of a catalyst defined in claim 1; and a gaseous effluent with a reduced content of H.sub.2S is recovered.

9. Process according to claim 8, where the gas stream containing sulphur compounds is a natural gas, a gas from refinery, a synthesis gas, a tail gas from a process of recovery of sulphur or a gas from a previous partial oxidation of a gas comprising H.sub.2S in which a substantial portion of H.sub.2S was oxidized to elemental sulphur followed by the separation of the same from said elemental sulphur.

10. Process according to claim 8, where said gas stream containing sulphur compounds comprises from 0.01 to 4% of H.sub.2S; and the inlet temperature of the gas stream containing the sulphur compounds is 150 to 240° C.

11. Process according to claim 10, where the gas stream containing sulphur compounds is a tail gas from the Claus process.

12. Process according to claim 8, where said gas stream containing sulphur compounds comprises from 0.01 to 4% of H.sub.2S; and the inlet temperature of the gas stream containing the sulphur compounds is 210 to 400° C.

13. Process according to claim 12, where the gas stream containing sulphur compounds is from a gas resulting from a previous partial oxidation of a gas comprising H.sub.2S in which a substantial portion of H.sub.2S was oxidized to elemental sulphur followed by the separation of the same from said elemental sulphur.

14. Process according to claim 13, where said previous partial oxidation is carried out according to a process for the selective oxidation of compounds that contain sulphur, comprising contacting a gas stream containing the sulphur compounds with a gas stream containing oxygen in the presence of a catalyst; and a gaseous effluent with a reduced content of H.sub.2S is recovered.

Description

EXAMPLES

Example 1

Preparation of the Catalyst

(1) a. 650 Kg of alumina were impregnated for 30 minutes with an aqueous solution of cobalt acetate, with a sufficient concentration to obtain the desired final content. Later it was proceeded to the draining and drying with air flow at a temperature of 170° C. for four hours. After the drying process it was subjected again to a heat treatment in calcination kiln of 300° C. for four hours, thus leaving the catalyst prepared for use.

(2) b. 800 Kg of a natural zeolite, clinoptilolite or mordenite, previously calcined at 300° C. for 4 hours, which were impregnated for 30 minutes with an aqueous solution of cobalt acetate, with a sufficient concentration to obtain the desired final content. Later it was proceeded to the draining and drying with air flow at a temperature of 170° C. for four hours. After the drying process it was subjected again to a heat treatment in calcination kiln of 300° C. for four additional hours, thus leaving the catalyst prepared for use.

Example 2

H2S to S Process

(3) In all the cases a gas containing 1% of H.sub.2S, 2% of O.sub.2, 0.35% of SO.sub.2 and N.sub.2 rest on dry basis and additional 25% of water was fed.

(4) A stream containing H.sub.2S was subjected to a process of catalytic oxidation for its conversion into elemental sulphur in the presence of the catalyst previously obtained according to the example 1, obtaining the following results.

(5) a. With Cobalt Oxide Supported on theta-Alumina

(6) TABLE-US-00001 Example 2.a GHSV (h.sup.−1) 1000 1000 1000 1000 T (° C.) 225 230 235 240 Conversion (%) 88.2 85.5 91.6 93.2 Selectivity (%) 77.2 83.8 86.9 67.5 S Yield (%) 68.1 71.6 79.6 62.9

(7) b. With Cobalt Oxide Supported on Clinoptilolite

(8) TABLE-US-00002 Example 2.b GHSV (h−1) 1000 1000 1000 1000 2000 T (° C.) 220 225 230 235 225 Conversion (%) 77.3 71.0 94.1 94.7 64.6 Selectivity (%) 91.7 94.7 98.9 90.7 89.9 S Yield (%) 70.9 94.2 93.1 85.9 58.1

Example 3

Comparative Example of the H2S to S Process

(9) a. Commercial catalyst of iron oxide on alumina (Catalysis Today, 16 (1993), 263-271)

(10) TABLE-US-00003 Example 3.a GHSV (h−1) 1000 T (° C.) 225-275 S Yield (%) .sup. 80-90%

(11) b. Only Clinoptilolite

(12) TABLE-US-00004 Example 3.b GHSV (h.sup.−1) 1000 1000 1000 T (° C.) 245 255 265 Conversion (%) 82.5 86.5 88.6 Selectivity (%) 52.1 81.3 92.2 S Yield (%) 48.2 78.5 90.9

Example 4

Incineration Process to SO2

(13) A gas containing 1% of H.sub.2S, 2% of O.sub.2, 0.35% of SO.sub.2 and N.sub.2 rest on dry basis and additional 25% of water was fed.

(14) Said stream was subjected to a catalytic incineration process for its conversion into elemental sulphur in the presence of the catalyst previously obtained according to the example 1, obtaining the following results.

(15) a. With Cobalt Oxide Supported on theta-Alumina

(16) TABLE-US-00005 Example 4.a GHSV (h−1) 1000 1000 1000 1000 T (° C.) 270 275 280 285 Conversion (%) 98.6 99.5 99.5 99.5 Selectivity (%) 90.9 95.7 91.2 86.9 SO2 Yield (%) 89.6 95.2 90.7 86.5

Example 5

Comparative Example of the Incineration Process to SO2

(17) a. Cu—Bi Commercial Catalyst on Alumina (Catalyst C-099 from Criterion Catalysts Co. Ltd., Reference C-099 Operating Guide).

(18) As it is described in the above-mentioned document, a gas containing 0.2% of H.sub.2S, 2% of O.sub.2, 0.1% of SO.sub.2, 0.2% of CO, 1.3% H.sub.2 and N.sub.2 rest on dry basis and additional 15% of water was fed. Said stream was subjected to a catalytic incineration process for its conversion into elemental sulphur in the presence of the commercial catalyst C-099 from Criterion Catalysts Co., Ltd., obtaining the following results.

(19) TABLE-US-00006 Example 5.a GHSV (h−1) 5000 5000 T (° C.) 300 400 Conversion (%) 99.8 99.8 Selectivity (%) 99.9 100 SO2 Yield (%) 99.7 99.8

(20) From the results of the examples described above it can be concluded that the catalyst object of the invention is more active than the existing ones because it achieves similar yields with temperatures between 25 and 40° C. lower, representing a substantial improvement of the energy efficiency of the process.

REFERENCES CITED IN THE APPLICATION

(21) EP242006 U.S. Pat. No. 5,814,293 DAVYDOV, A., et al. Metal oxides in hydrogen sulfide oxidation by oxygen and sulphur dioxide I. The comparison study of the catalytic activity. Mechanism of the interactions between H.sub.2S and SO.sub.2 on some oxides. Applied Catalysis A: General. 2003, vol. 244, no. 1, p. 93-100. HIDEAKI, HAMADA, et al. Role of supported metals in the selective reduction of nitrogen monoxide with hydrocarbons over metal/alumina catalysts. Catalysis Today. 1996, vol. 29, no. 1-4, p. 53-57 JANSSON, J. Low-Temperature CO Oxidation over Co.sub.3O.sub.4/Al.sub.2O.sub.3. Journal of Catalysis. 2000. vol. 194, no. 1, p. 55-60. GARBOWSKI, E., et al. Catalytic properties and surface states of cobalt-containing oxidation catalysts. Applied Catalysis. 1990. vol. 64, no. 1-2, p. 209-24. ASTM-D-4284 ASTM-D-3663 ASTM-D-4179 U.S. Pat. No. 5,814,293 BRUNAUER S. et al., J. Am. Chem. Soc., 1938, 60. 309 Catalysis Today, 16 (1993), 263-271 Criterion Catalysts Co. Ltd., C-099 Operating Guide