Pressure Swing Reaction (PSR) is a novel type of operation which combines simultaneous pressure swing separation and reaction of a gas mixture. A mathematical model of a PSR has been formulated and solved numerically by the method of characteristics. Three process arrangements that are typical of conventional pressure swing adsorption (PSA) have been investigated to show the effect of the operating parameters on the reaction and on the separation of the product from the reactant. The results of simple cycles at low product amounts show a separation inversion compared to conventional PSA. Purge cycle and backfill cycle results show more conventional separation behaviour. In comparsion with simple plug flow and fully mixed reactors, a PSR offers process intensification by the combination of reaction with primary product separation.