Catalyst for sulfuric acid contact process

Abstract

A catalyst for oxidation of SO 2 to SO 3 , which can be used as a fluidized bed catalyst. An abrasive resistant support is formed by adding silica filler and a clay binder to a silica sol; adding hydrated magnesium oxide to the resulting mixture, to form a gellable composition; dispersing the gellable composition in a liquid to form gel spheres; calcining the spheres; and treating them with an acid to remove acid soluble components. After the acid treatment, the support is impregnated with an alkali metal vanadate solution and calcined.

What is claimed is: 
     
       1. A process for the production of bead-form, highly active, supported catalyst for oxidation of sulfur dioxide into sulfur trioxide comprising: 1. suspending solids in an aqueous stable, silica sol, said solids being a silica filler having a specific surface area of about 40 to 80 m. 2  /g. according to BET in amount of 20-60% by weight of clay based upon a final weight of a resultant calcined granulate;   2. mixing the resultant suspension with an aqueous suspension of hydrated magnesium oxide to form a gellable mixture;   3. forming a calcined granulate by dispersing the gellable mixture in a liquid immiscible with water to form gel spheres, separating the gel spheres from the liquid and calcining the spheres;   4. treating the resultant calcined granulate from step (3) with acid to extract therefrom acid-soluble constituents;   5. calcining the granulate following said acid treatment of (4) by heating for at least 10 minutes at above 400° C; and   6. activating the resultant calcined granulate by impregnating it with an alkali metal vanadate solution.   
     
     
       2. A process according to claim 1 wherein the silica so employed in step (1) has a BET specific surface of about 150 to 400 m. 2  /g.; the amount of magnesium oxide employed in step (2) is about 0.1 to 3% by weight, based upon the resultant calcined granulate; the calcination of step (3) is performed by heating the spheres for at least 10 minutes at above about 500° C. and calcination following the acid treatment is performed by heating the acid extracted granulate at a temperature of 400 to 500° C. 
     
     
       3. Process according to claim 1, wherein said clay is kaolin. 
     
     
       4. Process according to claim 2, wherein said clay is kaolin. 
     
     
       5. Process according to claim 1, wherein said alkali metal vanadate solution is a potassium vanadate solution with a molar ratio of K 2  O to V 2  O 5  of 1.5:1 to 3.0:1 in a concentration such that the catalyst contains from 4 to 8% by weight of V 2  O 5 , based on impregnated anhydrous granulate. 
     
     
       6. A process according to claim 1 wherein the silica filler employed in step (1) contains about 5 to 10% by weight CaO. 
     
     
       7. A .Iadd.bead-form .Iaddend.catalyst comprising a support and activating agent, the support being at least 97% by weight of amorphous silica, based on the calcined support, the activating agent being from 4 to 8% by weight of V 2  O 5  and 3.1 to 12.4% by weight of K 2  O, based on the impregnated anhydrous catalyst, a portion of pores with diameters of from about 100 to 1500° A. of at least 80% of the total pore volume present.[...]. .Iadd., said catalyst having an abrasion resistance of about 0 to 3% by weight. .Iaddend..[.8. A catalyst composition according to claim 7 having an abrasion resistance from about 0 to 3% by weight..]. 
     
     
         . A .Iadd.bead-form .Iaddend.catalyst comprising a support and activating agent, the support being at least 97% by weight of silica, based on the calcined support, the activating agent being up to 8% by weight of V 2  O 5  and 3.1 to 12.4% by weight of K 2  O, based on the impregnated anhydrous catalyst, a proportion of pores with diameters of from about 100 to 1500 A. of at least 80% of the total pore volume present.[...]. .Iadd., said catalyst having an abrasion resistance from about 0 to 3% by weight. .Iaddend..[.10. A catalyst composition according to claim 9 having abrasion resistance from about 0 to 3% by weight..]..Iadd. based on 11. A silica gel bonded bead-form catalyst comprising a siliceous support having at least 97% by weight silica and a finite amount up to 8% by weight of V 2  O 5  and 3.1 to 12.4% by weight of K 2  O, based on the weight of the catalyst, said catalyst having a proportion of pores with diameters of about 100 to 1500 A. of at least 80% of the total pore volume present, said catalyst having an abrasion resistance of from about 0 to 3% by weight. .Iaddend. .Iadd.12. A catalyst according to claim 11 wherein the V 2  O 5  is present in an amount from 4 to 8% by weight based upon the weight of the catalyst. .Iaddend..Iadd.13. A catalyst according to claim 11 having a pore volume of 300 to 450 mm. 3  /g. .Iaddend. .Iadd.14. A catalyst prepared by the process of claim 1. .Iaddend..Iadd.15. A catalyst according to claim 14 wherein the silica sol employed in step (1) has a BET specific surface of about 150 to 400 m 2  /g; the amount of magnesium oxide employed in step (2) is about 0.2 to 3% by weight, based upon the resultant calcined granulate; the calcination of step (3) is performed by heating the spheres for at least 10 minutes at above at about 500° C and calcination following the acid treatment is performed by heating the acid extracted granulate at a temperature of 400 to 500° C. .Iaddend. .Iadd.16. A catalyst according to claim 14 which is in bead form. .Iaddend.