BACKGROUNDEnvironmental regulations are moving to tighter control of NOx emissions produced at both stationary and mobile sources. Selective catalytic reduction (SCR) of NOx with NH3 is an efficient treatment technique capable of operating at high gas flow rates (e.g. using monolithic catalysts) and a wide range of NO concentrations. The aim of this work is to provide guidelines for designing this kind of reactor taking into account both intrinsic kinetics and mass transfer. RESULTSExperiments have been done in lab-scale (0.5g) and bench-scale (430g) reactors operating under different conditions: temperature (150-320 degrees C), space velocity (WHSV 5360-16100molh(-1) kg(cat)(-1)), oxygen concentration (0-21%) and NH3/NO ratio (0.2-1.2). Temperature has a great influence on the reaction rate, and at least 300 degrees C is required at a WHSV of 16100molh(-1) kg(cat)(-1). Oxygen is required in the feed because it participates as reactant in SCR. CONCLUSIONSData obtained from the lab-scale reactor in the absence of mass transfer limitations have been used to fit an intrinsic kinetic model of the SCR reaction. A more complex model has been used for the bench-scale reactor accounting for reaction kinetics and mass transfer (internal effectiveness factor was determined) in the monolithic catalyst. (c) 2014 Society of Chemical Industry