Spatially and chemically resolved measurement of intra- and inter-particle molecular diffusion in a fixed-bed reactor

▶ New technique for measurement of spatially and chemically resolved diffusion. ▶ Discrimination between inter- and intra-particle diffusion is achieved. ▶ Esterification of ethanol and acetic acid over an ion-exchange resin is studied. ▶ Concentration gradients consistent with a mass transfer limitation are observed. ▶ Measurement is generic and can be applied to other catalyst systems.