START-UP PROCESS FOR HIGH SELECTIVITY ETHYLENE OXIDE CATALYSTS

摘要

A high selectivity catalyst start-up process is provided in which an excess level of chloride moderator (greater than 1 ppm) is present in the feed gas composition during each of the various stages of the start-up process. The excess level of chloride used in the start-up process maintains a low level of selectivity (less than 86%) during the entire start-up process. Despite the low selectivity values achieved during the start-up process of the present disclosure, high selectivity catalysts that are conditioned by such a start-up process exhibit improved catalyst performance during the normal operation of the catalyst.

主权项

1. A method for the start-up of a process for the epoxidation of ethylene comprising:
initiating an epoxidation reaction by reacting a feed gas composition containing ethylene, oxygen and a chloride moderator in the presence of a silver-based epoxidation catalyst at a first temperature from about 180° C. to about 230° C., wherein said chloride moderator is present in the feed gas composition at a concentration of greater than 1 ppm, and wherein said epoxidation reaction has a selectivity of less than 86%; increasing the first temperature to a second temperature of about 235° C. to about 270° C. at a ramp of 0.5° C./h to about 10° C./h in the presence of the feed gas composition used during said initiating; maintaining the second temperature over a time period of from about 10 hours to about 400 hours in the presence of the feed gas composition used during said initiating; reducing the concentration of the chloride moderator in the feed gas composition below that used during said initiating; and reducing the second temperature to a third temperature in the presence of said feed gas composition including said reduced concentration of chloride moderator.