Abstract: A cost effective process is presented for carrying out catalytic, in particular also exothermic, endothermic or autothermal reactions with optimum yield and selectivity. The system used is a wall-flow monolith which forces a flow from the inlet channel through the porous wall into the outlet channel by reciprocal closure of the gas channels. This is operated such that mass transfer and heat transport are determined virtually exclusively by convection, and diffusion-related thermal conduction phenomena can be neglected.