Catalyst with bimodal pore size distribution and the use thereof

摘要

The invention pertains to a catalyst useful for the epoxidation of an olefin. More particularly, the invention pertains to an improved catalyst useful for the epoxidation of ethylene to ethylene oxide. The catalyst has improved selectivity in the epoxidation process. The catalyst comprises a solid support having a surface, which has a first mode of pores which have a diameter ranging from about 0.01 μm to about 5 μm and having a differential pore volume peak in the range of from about 0.01 μm to about 5 μm. The surface then has a second mode of pores, different from the first mode of pores, which second mode of pores have a diameter ranging from about 1 μm to about 20 μm and have a differential pore volume peak in the range of from about 1 μm to about 20 μm. On the bimodal pore surface is a catalytically effective amount of silver or a silver-containing compound, a promoting amount of rhenium or a rhenium-containing compound, and a promoting amount of one or more alkali metals or alkali-metal-containing compounds.

主权项

1. A method for the oxidation of an olefin to an olefin oxide, the method comprising:
performing a vapor phase oxidation of an olefin with molecular oxygen in a fixed-bed tubular reactor in the presence of a catalyst, the catalyst comprising: (i) a support having a bimodal pore size distribution with a first mode of pores having a mean diameter ranging from about 0.01 μm to about 5 μm, and a second mode of pores having a mean diameter that is greater than the mean diameter range from about 0.01 μm to about 5 μm of said first mode of pores and is up to about 30 μm, wherein said first mode of pores comprises at most 45% of a total pore volume and said second mode of pores comprises at least 55% of the total pore volume, and (ii) a catalytically effective amount of silver, (iii) a promoting amount of rhenium, and (iv) a promoting amount of one or more alkali metals.