REDUCING NOX IN DIESEL EXHAUSTS BY SCR TECHNIQUE - EXPERIMENTS AND SIMULATIONS

Results of experiments are compared to simulations of the performance of V2O5/gamma-alumina SCR catalyst used to remove nitrogen oxides from diesel exhausts. The kinetic model is based on Eley-Rideal kinetics. Temperature programmed desorption (TPD) of the ammonia is used to evaluate adsorption/desorption parameters. Stationary experiments on a 3.6-dm(3) engine with a 4.8-dm(3) honeycomb catalyst is used to evaluate kinetic rate parameters for the reduction of NO with NH3. The desorption activation energy, E(a,des), is best fitted as a function of surface coverage yielding E(a,des) = 240 * (1-0.44 * theta(NH3)(0.36)) kJ/mol. A dynamic test (FTP) with a 12-dm(3) engine and 24.8-dm(3) honeycomb catalyst is done with a stoichiometric injection of ammonia. The NOx conversion is 52%, but during the freeway traffic the conversion reached 72%. The prediction of NOx conversion is good, but there are some deviations for temperature and ammonia slip.