Heat transfer between exothermic and endothermic reaction streams can take place at extremely high rates if one or both reactions take place catalytically on opposite sides of a thin wall. This eliminates the resistance to heat transfer in thermal boundary layers, potentially permitting much smaller reactors. A coupled catalytic wall reactor operating at temperatures of similar to 1000degreesC was built which enabled efficient heat exchange between exothermic methane catalytic combustion and endothermic homogeneous ethane cracking. Multiple passes were added on the combustion side to reduce heat losses in the system. A two-pass system operating in a co-current mode gave 77% ethane conversion and 87% selectivity to ethylene with a residence time of similar to 50 ms, with a residence time on the combustion side of similar to 10 ms. This reactor has been operated for many hours without any deterioration in performance.