A single channel model for a heavy-duty SCR catalyst was derived based on first principles. The model considered heat and mass transfer between the channel gas phase and the wash coat phase. The parameters of the kinetic model were estimated using bench-scale monolith isothermal data. Validation was done by simulating the output from a full-scale SCR monolith that was treating real engine gases from the European Transient Cycle (ETC). Three simplified models were derived, with simplifications that substantially decreased simulation time. These simplified models were coupled with the kinetic model and parameters of the nominal model, and their predictive performances were compared. Based on the results, two of the models were chosen for recalibration of the kinetic parameters, and analysed again. The results show that, after recalibration, the model that included simplifications related to mass transfer was able to keep most of its predictive capabilities, while the simulation time was reduced substantially. (C) 2016 Published by Elsevier Ltd.