Catalysts having enhanced stability, efficiency and/or activity for alkylene oxide production

Abstract

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.

Description

CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims the benefit of U.S. Provisional Patent Application Ser. No. 60 / 511,975, filed Oct. 16, 2003.FIELD OF INVENTION [0002] This invention relates to catalysts for the epoxidation of alkene, especially ethylene, to the corresponding alkylene oxide, for example, ethylene oxide, which have enhanced stability, efficiency and / or activity by incorporating sufficient amount of a zirconium component substantially as zirconium silicate. BACKGROUND OF THE INVENTION [0003] The production of alkylene oxide, such as ethylene oxide, by the reaction of oxygen or oxygen-containing gases with ethylene in the presence of a silver-containing catalyst at elevated temperature is an old and well-known art. For example, U.S. Pat. No. 2,040,782, dated May 12, 1936, describes the manufacture of ethylene oxide by the reaction of oxygen with ethylene in the presence of silver catalysts which contain a class of metal-containing promoters. In Reis...

AI Technical Summary

Benefits of technology

[0013] One aspect of the present invention is a catalyst for the manufacture of alkylene oxide by the vapor-phase epoxidation of alkene, said catalyst containing impregnated silver and at least one efficiency-enhancing promoter on a refractory solid support, said support incorporating a sufficient amount of zirconium component to enhance at least one of catalyst activity, efficiency and stability as compared to a similar catalyst which does not contain the zirconium component, said zirconium component being present in the support substantially as zirconium silicate.

[0016] While the present invention should be understood as being unconstrained by any particular theory, it is believed that the zirconium silicate (commonly referred to as zircon), added as an ingredient with other raw materials used to form the carrier support, survives the rigors of the calcining process without being oxidized or otherwise undergoing a substantial chemical change, and thereby becomes an integral part of the modified carrier, ultimately contributing to the favorable and unexpected characteristics observed in catalysts of the present invention employing such modified carriers.

[0017] A key distinguishing feature of the present invention is the use of zirconium silicate with other raw materials to modify the inert, refractory solid support (such as alpha-alumina) used as a carrier in a manner described herein, prior to depositing silver thereon with a well known promoter (and other optional additives) to convert the carrier to a catalyst. Zirconium silicate is employed in such a way and in sufficient amount that its presence in the modified carrier ultimately enhances the activity, efficiency and / or stability of the resultant catalyst of the present invention. Zirconium silicate remains substantially the same chemically throughout various preparation steps (including multiple calcining or roasting steps involving relatively high temperatures noted herein) for making the catalyst of the present invention, from its initial introduction as a part of raw materials for the modified carrier to the finished catalyst.

Problems solved by technology

When the efficiency and / or activity of a catalyst has declined to an unacceptably low level, typically the reactor must be shut down and partially dismantled to remove the catalyst.

This results in losses in time, productivity and materials, for example silver catalytic material and alumina carrier.

At best, replacement or regeneration of catalyst requires additional losses in production time to treat the catalyst and, at worst, requires replacement of the catalyst with the associated costs.

Images