NOx emissions from the energy and transport sectors represent a major hazard to human health and this has been the focus of significant industrial and academic research. One of the important processes in the armoury available for emissions control from vehicles, large and small, power stations, ships, trains and non-road machinery is the selective catalytic reduction reaction (SCR), in which a reductant such as ammonia, urea or hydrocarbon fuel, is injected into the exhaust to reduce the NO and NO2 (NOx) to harmless nitrogen. Copper supported on a zeolite have proven to be extremely active for SCR, and also demonstrate excellent long term stability, and are therefore often the prime choice for use in the catalytic SCR system. For these initial experiments we wish to investigate how the presence of copper and the shape of the zeolite modifies the diffusion of ammonia.