SYSTEM FOR DECREASING TOXICITY OF ENGINE OFFGAS USING SELECTIVE CATALYTIC REDUCTION CATALYST Russian patent published in 2013 - IPC B01D53/94 B01J23/30 B01J21/06 B01J23/10 B01J29/72 B01J35/00 F01N3/20 

FIELD: process engineering.

SUBSTANCE: invention relates to reduction of toxicity of automotive diesel exhaust gases containing nitrogen oxides and hydrocarbons by adding ammonium or compounds decomposing thereto to offgas flow to be forced above two selective reduction catalysts (SRC). First SRC catalyst arranged at inlet side catalyses efficiently the co-proportioning of nitrogen oxides by ammonium at 300-500°C and contains tungsten oxide WO₃ and homogeneous mixed cerium and zirconium oxides (Ce, Zr)O₂. Note here that hydrocarbons contained in exhaust gas are partially oxidised. Second SRC catalyst arranged at outlet side contains copper-substituted zeolite compound and catalyses efficiently the co-proportioning of nitrogen oxides by ammonium at 150-400°C and, at a time, accumulates excess ammonium.

EFFECT: good initial working characteristics at lower temperatures, higher efficiency nitrogen oxide conversion in wide temperature range.

17 cl, 4 dwg, 1 ex