Method and apparatus for treating an engine exhaust gas stream

An exhaust gas purifying apparatus for converting noxious components such as hydrocarbons and other pollutants from an engine exhaust gas into innocuous products, the apparatus comprising:

• a flow path for conveying engine exhaust gases containing hydrocarbons and other pollutants from an engine and comprising;
• a first catalyst zone in the flow path and downstream of the engine comprising a first catalyst effective for the conversion of at least some of the other pollutants into innocuous substances,
• an adsorbent zone, comprising H Beta zeolite material having a relative Bronsted acidity of less than 0.5, disposed in the flow path in gas flow communication with and downstream of the first catalyst zone and comprising an adsorbent for adsorbing at least some hydrocarbons in the engine exhaust gas, at least during a cold-start period of engine operation, and
• a second catalyst zone disposed in gas flow communication with and downstream of the adsorbent zone and comprising a second catalyst for at least converting unburned hydrocarbons into innocuous substances;
• and
• heat exchange means disposed in a heat transfer relation between the first catalyst zone and the second catalyst zone for providing heat transfer by indirect heat exchange from the first catalyst zone to the second catalyst zone, wherein the heat exchange means comprises a crossflow monolith comprising a first heat exchange zone, the first heat exchange zone comprising the first catalyst zone, and a second heat exchange zone, the second heat exchange zone comprises the second catalyst zone.