Process for the reduction of NH.sub.3 in regeneration zone off gas by select recycle of certain-sized NH.sub.3 decomposition catalysts

摘要

This process discloses a reduction in the content of ammonia in a regeneration zone off gas of a fluid catalytic cracking unit by the select recycle of certain sized ammonia decomposition catalyst particles. The ammonia decomposition may be aided by injection of NO.sub.x into the off gas. The particles are acquired from a separation means through which is passed the regeneration zone off gas. A solid-free regeneration zone off gas and a stream of solid particles, including a noble metal dispersed on an inorganic support, having a size of from 10 to 40 microns, are acquired. The latter segregated particles are then injected into the regeneration zone at a predetermined make-up rate to insure a very short residence time in the dense phase of the regeneration zone and to provide a relatively constant concentration of the NH.sub.3 decomposition catalyst in the dilute phase of the regeneration zone to convert NH.sub.3 to N.sub.2 and water vapor. The regeneration zone is operated in a partial combustion mode defined by a CO content of from 1 to 6 percent by volume.