METHOD AND APPARATUS FOR TREATING AN ENGINE EXHAUST GAS STREAM

摘要

A method and apparatus in accordance with the invention is described which comprises treating an engine (12) exhaust gas stream containing hydrocarbons and other pollutants. The method of this invention comprises the steps of flowing the exhaust gas stream through a catalytic member comprising a monolith body (16) having a first catalyst zone (18) and a second catalyst zone (28) therein to contact a catalyst in a first catalyst zone (18) to convert at least some of the pollutants in the exhaust gas stream into innocuous products. The exhaust gas stream is then discharged from the catalytic member and flowed through an adsorbent zone (24) to adsorb at least some of the hydrocarbon pollutants with an adsorbent composition. The exhaust gas stream is then discharged from the adsorbent zone (24) and flowed to the second catalyst zone (28) to convert at least some of the pollutants into innocuous products. The exhaust gas stream, so treated, is then discharged to the atmosphere through suitable discharge means. A preferred adsorbent is a zeolite, having a relatively high silica to alumina ratio and a low relative Bronsted acidity. The preferred adsorbent compositions comprise Beta zeolites. An oxidant such as air (32) may be added to the exhaust gas stream at a point upstream of the second catalyst zone.