Process for removing sulfur oxides from a gas

Claim 2

A process for removing sulfur oxides from a gas which comprises: (a) absorbing sulfur oxides from the gas with an absorbent which comprises a physical mixture of: (i) a particulate cracking catalyst comprising from about 0.5 to about 50 weight percent of a crystalline alumino-silicate zeolite which is distributed throughout a porous matrix wherein said matrix comprises from about 70 to about 100 weight percent of alumina and (ii) a particulate solid other than cracking catalyst which comprises at least one inorganic oxide selected from the group consisting of the oxides of aluminum and magnesium in association with at least one free or combined rare earth metal selected from the group consisting of lanthanum, cerium, praseodymium, samarium and dysprosium, wherein the ratio by weight of inorganic oxide or oxides to rare earth metal or metals is from about 1.0 to about 1,000 and (b) removing said absorbed sulfur oxides from the absorbent as a sulfur-containing gas which comprises hydrogen sulfide by contacting said absorbent with a hydrocarbon at a temperature in the range from about 375° to about 900° C.

Claim 3

The process as set forth in claim 1 wherein said inorganic oxide comprises alumina.

Claim 4

The process as set forth in claim 1 wherein said inorganic oxide is selected from the group consisting of gamma-alumina and eta-alumina.

Claim 5

The process as set forth in claim 1 wherein said inorganic oxide comprises gamma-alumina.

Claim 6

The process as set forth in claim 1 wherein said free or combined rare earth metal is selected from the group consisting of lanthanum and cerium.

Claim 7

The process as set forth in claim 1 wherein said free or combined rare earth metal comprises an oxide selected from the group consisting of the oxides of lanthanum and cerium.

Claim 8

The process as set forth in claim 1 wherein the ratio by weight of inorganic oxide or oxides to rare earth metal or metals is from about 2.0 to about 100.

Claim 9

The process as set forth in claim 1 wherein the sulfur oxide containing gas also contains an amount of molecular oxygen which is in excess of the stoichiometric amount required to convert any sulfur dioxide present to sulfur trioxide.

Claim 10

The process as set forth in claim 1 wherein the absorbent containing absorbed sulfur oxides is simultaneously contacted with added steam while it is contacted with said hydrocarbon; and the amount of steam is greater, on a mole basis, than the amount of sulfur oxides absorbed by the absorbent.

Claim 11

The process as set forth in claim 1 wherein the absorbent is contacted with steam subsequent to said contacting with a hydrocarbon, and the amount of steam is greater, on a mole basis, than the amount of sulfur oxides absorbed by the absorbent.

Claim 12

A process for the cyclic, fluidized catalytic cracking of a hydrocarbon feedstock containing organic sulfur compounds wherein: (i) said feedstock is subjected to cracking in a reaction zone through contact with a particulate cracking catalyst at a temperature in the range from 430° to 700° C.; (ii) cracking catalyst, which is deactivated by sulfur-containing coke deposits, is separated from reaction zone effluent and passes to a stripping zone wherein volatile deposits are removed from said catalyst by contact with a stripping gas comprising steam at a temperature in the range from 430° to 700° C.; (iii) stripped catalyst is separated from stripping zone effluent and passes to a catalyst regeneration zone and non-stripped, sulfur-containing coke deposits are removed from the stripped catalyst by burning with an oxygen containing regeneration gas at a temperature in the range from 565° to 790° C., thereby forming sulfur oxides; and (iv) resulting catalyst is separated from regeneration zone effluent gas and recycled to the reaction zone; and wherein emissions of sulfur oxides in the regeneration zone effluent gas are reduced by the method which comprises: (a) circulating a fluidizable physical mixture of solid particles through the catalytic cracking process which comprises: (i) a particulate cracking catalyst comprising from about 0.5 to about 50 weight percent of a crystalline aluminosilicate zeolite which is distributed throughout a porous matrix wherein said matrix comprises from about 70 to about 100 weight percent of alumina and (ii) a particulate solid other than cracking catalyst which comprises at least one inorganic oxide selected from the group consisting of the oxides of aluminum and magnesium in association with at least one free or combined rare earth metal selected from the group consisting of lanthanum, cerium, praseodymium, samarium and dysprosium, wherein the ratio by weight of inorganic oxide or oxides to rare earth metal or metals is from about 1.0 to about 1,000; (b) absorbing sulfur oxides in said regeneration zone with the mixture of solid particles; and (c) removing said absorbed sulfur oxides from the mixture of solid particles as a sulfur-containing gas which comprises hydrogen sulfide by contacting said mixture of solid particles with the hydrocarbon feedstock in said reaction zone.

Claim 13

A process for the cyclic, fluidized catalytic cracking of a hydrocarbon feedstock containing organic sulfur compounds wherein: (i) said feedstock is subjected to cracking in a reaction zone through contact with a particulate cracking catalyst at a temperature in the range from 430° to 700° C.; (ii) cracking catalyst, which is deactivated by sulfur-containing coke deposits, is separated from reaction zone effluent and passes to a stripping zone wherein volatile deposits are removed from said catalyst by contact with a stripping gas comprising steam at a temperature in the range from 430° to 700° C.; (iii) stripped catalyst is separated from stripping zone effluent and passes to a catalyst regeneration zone and non-stripped, sulfur-containing coke deposits are removed from the stripped catalyst by burning with an oxygen containing regeneration gas at a temperature in the range from 565° to 790° C., thereby forming sulfur oxides; and (iv) resulting catalyst is separated from regeneration zone effluent gas and recycled to the reaction zone; and wherein emissions of sulfur oxides in the regeneration zone effluent gas are reduced by the method which comprises: (a) circulating a fluidizable physical mixture of solid particles through the catalytic cracking process which comprises: (i) a particulate cracking catalyst comprising from about 0.5 to about 50 weight percent of a crystalline aluminosilicate zeolite which is distributed throughout a porous matrix wherein said matrix comprises from about 70 to about 100 weight percent of alumina and (ii) a particulate solid other than cracking catalyst which comprises at least one inorganic oxide selected from the group consisting of the oxides of aluminum and magnesium in association with at least one free or combined rare earth metal selected from the group consisting of lanthanum, cerium, praseodymium, samarium and dysprosium, wherein the ratio by weight of inorganic oxide or oxides to rare earth metal or metals is from about 1.0 to about 1,000; (b) absorbing sulfur oxides in said regeneration zone with the mixture of solid particles; and (c) removing said absorbed sulfur oxides from the mixture of solid particles as a sulfur-containing gas which comprises hydrogen sulfide by contacting said mixture of solid particles with the hydrocarbon feedstock in said reaction zone.

Claim 14

The process as set forth in claim 11 wherein said inorganic oxide comprises alumina.

Claim 15

The process as set forth in claim 11 wherein said inorganic oxide is selected from the group consisting of gamma-alumina and eta-alumina.

Claim 16

The process as set forth in claim 11 wherein said inorganic oxide comprises gamma-alumina.

Claim 17

The process as set forth in claim 11 wherein said free or combined rare earth metal is selected from the group consisting of lanthanum and cerium.

Claim 18

The process as set forth in claim 11 wherein said free or combined rare earth metal comprises an oxide selected from the group consisting of the oxides of lanthanum and cerium.

Claim 19

The process as set forth in claim 11 wherein the ratio by weight of inorganic oxide or oxides to rare earth metal or metals is from about 2.0 to about 100.

Claim 20

The process as set forth in claim 11 wherein said particulate solid other than cracking catalyst contains at least about 40 weight percent of the inorganic oxide or oxides.

Claim 21

The process as set forth in claim 11 wherein said mixture of solid particles contains from about 0.1 to about 50 weight percent of the particulate solid other than cracking catalyst.

Claim 22

The process as set forth in claim 11 wherein said mixture of solid particles contains from about 0.5 to about 10 weight percent of the particulate solid other than cracking catalyst.

Claim 23

The process as set forth in claim 11 wherein the regeneration zone effluent gas contains at least about 0.5 volume percent of molecular oxygen.

Claim 24

The process as set forth in claim 1 wherein said free or combined rare earth metal comprises lanthanum.

Claim 25

The process as set forth in claim 11 wherein said free or combined rare earth metal comprises lanthanum.