Catalytic nitrogen oxide(s) redn. appts. for vehicles - comprises flow mixer urea evaporator hydrolysis catalyst, for exhaust gas treatment

摘要

The appts. has a redn. catalyst (5), in an oxygen-contg. exhaust gas pipe, and an urea container (7) connected to a spray nozzle (9) for finely spraying urea soln. onto an evaporator (3). The evaporator (3) is in the form of a flow mixer. Pref. the flow mixer acts as a hydrolysis catalyst comprising a support structure coated with a 90-10:10-90 wt. ratio mixt. of Al2O3 and TiO2, SiO2, ZrO2 and/or H-zeolite. ADVANTAGE - Vehicle space requirement for the exhaust gas treatment appts. (comprising evaporator, hydrolyser and SCR catalyst) is reduced and quantitative (more than 99.9%) decompsn. of urea into NH3 and CO2 is ensured to avoid urea deposition of the catalyst inlet, fouling of the SCR catalyst and emission of urea and urea-generated particles (e.g. cyanuric acid).