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 alumina in association with free or combined lanthanum at a temperature in the range from about 100° to about 900° C., wherein the ratio by weight of alumina to lanthanum 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 in the presence of a hydrocarbon cracking catalyst 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 alumina is selected from the group consisting of gamma-alumina and eta-alumina.

Claim 4

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

Claim 5

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

Claim 6

The process as set forth in claim 1 wherein the ratio by weight of alumina to lanthanum is from about 2.0 to 100.

Claim 7

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 8

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 in the presence of a hydrocarbon cracking catalyst; and the amount of steam is greater, on a mole basis, than the amount of sulfur oxides absorbed by the absorbent.

Claim 9

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

Claim 10

A process for the cyclic, fluidized catalytic cracking of a hydrocarbon feedstock containing from about 0.2 to about 6 weight percent sulfur as 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) absorbing sulfur oxides in said regeneration zone with fluidizable particulate solids which comprise alumina in association with free or combined lanthanum, wherein said alumina and lanthanum are present in the particulate solids in sufficient amount to effect the absorption of at least about 50 percent of the sulfur oxides produced by the burning of sulfur-containing coke deposits in the regeneration zone and the ratio by weight of alumina to lanthanum is from about 1.0 to about 30,000; and (b) removing said absorbed sulfur oxides from the fluidizable particulate solids as a sulfur-containing gas which comprises hydrogen sulfide by contacting said particulate solids with the hydrocarbon feedstock in said reaction zone.

Claim 11

A process for the cyclic, fluidized catalytic cracking of a hydrocarbon feedstock containing from about 0.2 to about 6 weight percent sulfur as 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) absorbing sulfur oxides in said regeneration zone with fluidizable particulate solids which comprise alumina in association with free or combined lanthanum, wherein said alumina and lanthanum are present in the particulate solids in sufficient amount to effect the absorption of at least about 50 percent of the sulfur oxides produced by the burning of sulfur-containing coke deposits in the regeneration zone and the ratio by weight of alumina to lanthanum is from about 1.0 to about 30,000; and (b) removing said absorbed sulfur oxides from the fluidizable particulate solids as a sulfur-containing gas which comprises hydrogen sulfide by contacting said particulate solids with the hydrocarbon feedstock in said reaction zone.

Claim 12

The process as set forth in claim 9 wherein said alumina is selected from the group consisting of gamma-alumina and eta-alumina.

Claim 13

The process as set forth in claim 9 wherein said alumina comprises gamma-alumina.

Claim 14

The process as set forth in claim 9 wherein the regeneration zone effluent gas contains at least about 0.5 volume percent of molecular oxygen.

Claim 15

The process as set forth in claim 9 wherein the ratio by weight of alumina to lanthanum is from about 2.0 to about 100.

Claim 16

The process as set forth in claim 9 wherein the lanthanum is contained within the particles of cracking catalyst.

Claim 17

The process as set forth in claim 14 wherein said lanthanum is in non-ion-exchanged form.

Claim 18

The process as set forth in claim 9 wherein said lanthanum is incorporated into the fluidizable particulate solids in situ by introducing into the catalytic cracking process cycle an aqueous or organic solution or dispersion of at least one compound of said lanthanum.

Claim 19

The process as set forth in claim 9 wherein said alumina is contained in a particulate fluidizable solid other than said cracking catalyst.

Claim 20

The process as set forth in claim 9 wherein said lanthanum is contained in a particulate fluidizable solid other than said cracking catalyst.

Claim 21

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) absorbing sulfur oxides in said regeneration zone with a fluidizable particulate solid other than said cracking catalyst which comprises alumina in association with free or combined lanthanum, wherein the ratio by weight of alumina to lanthanum is from about 1.0 to about 1,000 and said particulate solid is physically admixed with said cracking catalyst; and (b) removing said absorbed sulfur oxides from the fluidizable particulate solid as a sulfur-containing gas which comprises hydrogen sulfide by contacting said particulate solid with the hydrocarbon feedstock in said reaction zone.

Claim 22

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) absorbing sulfur oxides in said regeneration zone with a fluidizable particulate solid other than said cracking catalyst which comprises alumina in association with free or combined lanthanum, wherein the ratio by weight of alumina to lanthanum is from about 1.0 to about 1,000 and said particulate solid is physically admixed with said cracking catalyst; and (b) removing said absorbed sulfur oxides from the fluidizable particulate solid as a sulfur-containing gas which comprises hydrogen sulfide by contacting said particulate solid with the hydrocarbon feedstock in said reaction zone.

Claim 23

The process as set forth in claim 19 wherein said alumina is selected from the group consisting of gamma-alumina and eta-alumina.

Claim 24

The process as set forth in claim 19 wherein said alumina comprises gamma-alumina.

Claim 25

The process as set forth in claim 19 wherein the regeneration zone effluent gas contains at least about 0.5 volume percent of molecular oxygen.

Claim 26

The process as set forth in claim 19 wherein the ratio by weight of alumina to lanthanum is from about 2.0 to about 100.

Claim 27

The process as set forth in claim 19 wherein the fluidizable particulate solid other than cracking catalyst contains at least about 40 weight percent of alumina.

Claim 28

The process as set forth in claim 19 wherein the amount of said fluidizable particulate solid other than cracking catalyst is from about 0.1 to about 50 weight percent of the total mixture of cracking catalyst and particulate solid other than cracking catalyst.

Claim 29

The process as set forth in claim 19 wherein the amount of said fluidizable particulate solid other than cracking catalyst is from about 0.5 to about 10 weight percent of the total mixture of cracking catalyst and particulate solid other than cracking catalyst.

Claim 30

The process as set forth in claim 19 wherein said free or combined lanthanum comprises lanthanum oxide.

Claim 31

The process as set forth in claim 19 wherein said particulate solid other than cracking catalyst additionally comprises magnesium oxide, and the weight ratio of alumina to magnesium oxide is from about 2.0 to about 100.

Claim 32

The process as set forth in claim 19 wherein said lanthanum is in the form of a lanthanum-containing mixture of free or combined rare earth metals wherein lanthanum is the major component of said mixture of rare earth metals.