Catalysts having enhanced stability, efficiency and/or activity for alkylene oxide production
A catalyst for the manufacture of alkylene oxide, for example ethylene oxide, by the vapor-phase epoxidation of alkene containing impregnated silver and at least one efficiency-enhancing promoter on an inert, refractory solid support, said support incorporating a sufficient amount of zirconium component (present and remaining substantially as zirconium silicate) as to enhance at least one of catalyst activity, efficiency and stability as compared to a similar catalyst which does not contain the zirconium component.
1. A catalyst for the manufacture of alkylene oxide by the vapor-phase epoxidation of alkene, said catalyst comprising impregnated silver and at least one efficiency-enhancing promoter on a refractory solid support, wherein the refractory solid support comprises zirconium silicate in an amount from about 0.3 to 3.0% by weight of zirconium silicate based on the total weight of the support wherein the refractory solid support, exclusive of zirconium silicate, is at least 95% by weight alpha alumina, and wherein the refractory solid support, exclusive of zirconium silicate, contains less than about 500 ppmw alkaline earth metal excluding calcium compounds, measured as the alkaline earth metal oxide, and less than about 350 ppmw calcium.
2. The catalyst of claim 1 wherein the impregnated silver is present from about 2 to 60% by weight of the catalyst.
3. The catalyst of claim 2 wherein the impregnated silver is present from about 5 to 50% by weight of the catalyst.
4. The catalyst of claim 3 wherein the impregnated silver is present from about 10 to 40% by weight of the catalyst.
5. The catalyst of claim 1 wherein at least one of the efficiency enhancing promoters comprises at least one alkali metal, alkaline earth metal and/or oxyanion of an element, other than oxygen, having an atomic number of 5 to 83 and being selected from groups 3b through 7b and 3a through 7a of the Periodic Table.
6. The catalyst of claim 1 wherein at least one of the efficiency-enhancing promoters is an efficiency enhancing salt of a member of a redox-half reaction pair.
7. The catalyst of claim 1 wherein at least one of the efficiency-enhancing promoters is a rhenium component.
8. The catalyst of claim 1 wherein the refractory solid support, exclusive of zirconium silicate, is at least 99% by weight alpha alumina.
9. The catalyst of claim 8 wherein the refractory solid support has a morphology comprising interlocking platelets of alpha-alumina.
10. The catalyst of claim 1 wherein the refractory solid support has a surface area of at least about 0.5 m2/g, a pore volume of at least about 0.5 cc/g, and a median pore diameter between about 1 to 50 microns.