Abstract: Urea synthesis in two stages, in which the first stage of ammonium carbamate formation is in indirect heat exchange with the second stage of ammonium carbamate dehydration to synthesize urea. Excess ammonia is separately preheated by heat exchange with the second stage and added to the main process stream between the first stage and the second stage.

Abstract: The exhaust gas discharged from an engine such as an internal combustion engine or the like is treated to convert harmful or noxious pollutant components such as nitrogen oxides, carbon monoxide and unburned hydrocarbons to innocuous compounds, by contacting the exhaust gas with two stages in series of a catalyst composition containing 8% to 20% by weight of copper as equivalent copper oxide, 1% to 5% by weight of cobalt as equivalent cobalt oxide, and 0.5% to 3% by weight of manganese as equivalent manganese dioxide, deposited on particles of transitional alumina having a surface area in the range of 200 to 400 square meters per gram. The copper and cobalt are at least partially present in the form of reduced oxides, and the catalyst may also contain 1% to 5% nickel as equivalent nickel oxide.