Kinetic modeling of the combined HCHO/SCR reaction on V2O5/WO3/TiO2 catalyst in lean exhaust gas of stationary gas engines

For the simultaneous removal of NO x and HCHO from lean exhaust gas of stationary gas engines, V₂O₅/WO₃/TiO₂ (VWT) catalysts are used. The VWT catalysts oxidize HCHO and convert NO x according to the selective catalytic reduction (SCR). However, the combined HCHO/SCR conversion leads to the production of HCN, which can subsequently decompose along the VWT catalyst. In this context, a global kinetic model of the combined HCHO/SCR conversion was developed using a VWT monolith with a V 2 O 5 load of 2 %. The model was based on a systematic series of kinetic studies performed in a gradient free loop reactor as well as a plug flow reactor The kinetic model represented a network of 8 reactions consisting of the NH 3 adsorption and desorption, SCR reaction, NH 3 oxidation, HCHO oxidation, HCN formation as well as hydrolysis and oxidation of HCN. The kinetics of the respective reactions was described by Arrhenius-based rate expressions including 19 kinetic parameters. The kinetic parameters were primarily obtained from numerical fitting calculations. The model and the implemented kinetic parameters were finally validated by predicting kinetic experiments. Moreover, the model was used to simulate the fractions of NO x , NH 3 , HCHO and HCN along the VWT monolith. Using these axial profiles operation temperatures and design of the monolith were evaluated to limit the emissions of a stationary lean-burn gas engine. • Global kinetic model of HCHO-SCR conversion in lean exhaust gas was developed. • Highly active SCR catalyst with a V 2 O 5 load of 2 % was considered. • Kinetic model includes the SCR reaction and the HCHO oxidation. • Model also describes the kinetics of side-production and decay of HCN. • Model was validated by predicting experiments.