Claims
- 1. A high-density regenerated silica catalyst for the oxidation of sulphur dioxide to sulphur trioxide, comprising a catalyst supported on a siliceous matrix, based on vanadium, iron, oxygen and alkali metals (Me), wherein the V.sub.2 O.sub.5 content ranges from 6 to 9% by weight, wherein the Me.sub.2 O content ranges from 8.5 to 12% by weight, wherein the particle density ranges from 1.10 to 1.40 g/cm.sup.3 and wherein:
- the volume of the pores ranges from 0.20 to 0.70 cm.sup.3 /g and the surface area ranges from 0.30 to 5 m.sup.2 /g, the average radius of the pores being from 600 to 2,200 nanometers;
- the silica (SiO.sub.2) content is from 56% to 75% by weight and the Fe.sub.2 O.sub.3 content is from 0.90% to 1.45% by weight;
- said catalyst being obtained by a process comprising:
- a) grinding an exhausted catalyst comprising the catalyst to be obtained, but poorer as to catalytic elements, having a silica content lower than 75% by weight and a Fe.sub.2 O.sub.3 content from 0.90% to 1.45% by weight until the average diameter of the particles is from 1 to 50 micrometers; and
- b) impregnating the finely ground product from step (a) with an aqueous solution containing catalytic elements exhausted from the catalyst and
- c) obtaining the regenerated catalyst.
- 2. The catalyst of claim 1, having the shape of solid or hollow cylindrical pellets.
- 3. The catalyst of claim 1, having the shape of poly-lobed cylindrical pellets.
- 4. The catalyst of anyone of the preceding claims 1 or 2 or 3 further comprising the alkali metal caesium, together with another alkali metal.
- 5. The catalyst of claim 1, wherein the average radius of the pores ranges from 650 to 1,000 nanometers.
- 6. The catalyst of claim 1, wherein a fresh diatomaceous earth, in an amount up to 60% by weight on the whole catalyst, is added to the ground catalyst prior to impregnation.
- 7. The catalyst of claim 1, wherein impregnation is effected by conventional dry-impregnation technology.
- 8. The catalyst of claim 1, wherein impregnation is followed by thickening with thickening material.
- 9. The catalyst of claim 8, wherein thickening is preceded by adding a pore-forming agent.
- 10. The catalyst of claim 8, wherein thickening is followed by shaping, in the form of solid, hollow or poly-lobed cylindrical particles.
- 11. The catalyst of claim 10, wherein shaping is followed by drying and by calcining in the presence of SO.sub.2, at temperatures from 270.degree. to 600.degree. C.
- 12. The catalyst of claim 1, wherein impregnation is effected by using an aqueous solution containing:
- a) a water-soluble vanadium compound; and
- b) a water-soluble potassium compound.
- 13. A catalyst according to claim 12, wherein said solution also contains a water-soluble sodium compound.
- 14. The catalyst of claim 12, wherein said solution also contains a water-soluble caesium compound or a pore-forming agent or a water-soluble titanium compound.
- 15. The catalyst of claim 12, wherein said vanadium compound is selected from potassium metavanadate and ammonium metavanadate.
- 16. The catalyst of claim 12, wherein said potassium compound is selected from potassium metavanadate and potassium bisulphate.
- 17. The catalyst of claim 1, wherein the particle density ranges from 1.10 to 1.35 g/cm.sup.3.
- 18. The catalyst of claim 1, wherein the volume of the pores ranges from 0.30 to 0.70 cm.sup.3 /g.
- 19. The catalyst of claim 1, wherein the surface area ranges from 0.50 to 3 m.sup.2 /g.
- 20. The catalyst of claim 3, wherein the pellets have helical grooves.
- 21. The catalyst of claim 4, further comprising titanium.
- 22. The catalyst of claim 1, wherein the average diameter of the particles is from 5 to 40 micrometers.
- 23. The catalyst of claim 6, wherein the diatomaceous earth is an amount up to 60% by weight.
- 24. The catalyst of claim 6, wherein the diatomaceous earth is replaced by silicalites, titanium silicalites, vanadium silicalites or alpha-quartz.
- 25. The catalyst of claim 8, wherein thickening is effected by addition of carboxymethyl cellulose or of a polyacrylamide.
- 26. The catalyst of claim 25, wherein the polyacrylamide is hydrolized.
- 27. The catalyst of claim 9, wherein the pore-forming agent is selected from starch, ammonium phosphate, diammonium phosphate.
- 28. The catalyst of claim 27, wherein the pore forming agent includes water.
- 29. The catalyst of claim 10, wherein shaping is by extrusion.
- 30. The catalyst of claim 10, wherein the particles have helical grooves.
- 31. The catalyst of claim 12, wherein the vanadium compound is selected from KVO.sub.3, NaVO.sub.3 and NH.sub.4 VO.sub.3.
- 32. The catalyst of claim 12, wherein the water-soluble potassium compound is selected from potassium hydroxide, oxide, oxalate, carbonate, bicarbonate, sulphate, bisulphate and metavanadate.
- 33. The catalyst of claim 13, wherein the water-soluble sodium compound is selected from sodium hydroxide, oxide, carbonate, bicarbonate, sulphate, bisulphate and metavanadate.
Priority Claims (1)
Number |
Date |
Country |
Kind |
19098 A/88 |
Jan 1988 |
ITX |
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Parent Case Info
This is a continuation of co-pending application Ser. No. 07/297,335, filed on Jan. 17, 1989, now abandoned.
US Referenced Citations (8)
Foreign Referenced Citations (6)
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Jul 1985 |
CAX |
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EPX |
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EPX |
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Non-Patent Literature Citations (2)
Entry |
Journal of Catalysis, vol. 43, 1976, pp. 243-251, Hassan et al.: "Catalytic and surface characteristics of newly imported, exhausted, and regenerated V205 catalysts used in H2SO4 manufacturing". |
Ind. Eng. Chem. Prod. Dev., 1981, 20, 439-450, Neimark et al., "Theory of Preparation of Supported Catalysts". |
Continuations (1)
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Number |
Date |
Country |
Parent |
297335 |
Jan 1989 |
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