The feasibility of the selective catalytic reduction (SCR) of NOx with ammonia in unsteady-state reactors is investigated by means of numerical simulations. A reactors network (RN) with periodical change of the feeding position is shown to be an alternative to the well investigated reverse-flow reactor (RFR) in order to fulfil the requirements on NOx conversion and ammonia emissions. Non-isothermal operation was studied, with low temperature feed, and the influence of the switching time on the mean outlet concentration of NH3 and NOx was investigated, as well as the response of these devices to perturbations in the pollutant feed concentration. (c) 2005 Elsevier Ltd. All fights reserved.