Influence of exhaust temperature and catalytic substrate properties on diesel exhaust

Abstract: The influence of different temperatures and CDPF (catalyzed diesel particulate filter) substrate properties on NOx reduction and PM oxidation were studied by catalytic experiments, engine bench tests and simulation. From activity evaluation and characterization tests, it was found that owing to the higher mobility of lattice oxygen and the maximum concentrations of oxygen vacancies, La2Cu0.7Fe0.3O4 showed a relatively better catalytic performance between 300°C to 500°C. The NO conversion efficiency on SiC (Silicon carbide) substrate was better than that on cordierite substrate from 350℃ to 500℃ under simulated diesel emission conditions. The engine bench test results showed that NOx conversion efficiency increased from 340℃ to 528℃. Due to higher porosity and stronger thermal diffusion characteristics, the soot oxidation rate and NOx conversion rate on SiC substrate CDPF is better than that on cordierite substrate, under condition of 75% and 90% loads of engine at 1 600 r/min. From simulation researches, CDPF with higher cell density and specific surface-area cell resulted in lower internal mass-transfer resistances, and higher mass-transfer coefficients, which yielded better soot and NOx reduction performances.