An industrial Cu-based low-temperature water-gas shift (LTWGS) reactor, subject to deactivation by irreversible chlorine adsorption, has been modeled and optimized. Both the chlorine adsorption kinetics and deactivation kinetics were assumed first order to chlorine partial pressure, and the rate constants were considered independent of temperature. The Efficient Production (EP) method has been used to compute the reactor production until the outlet CO conversion decays below a permissible minimum level. Two alternative strategies for the inlet temperature have been used to maximize the EP: constant and time-variable. Compared to the EP obtained for the optimum constant inlet temperatures, EP resulting from the use of the optimum time-variable inlet temperature sequence were higher, affording important energy savings. Furthermore, a sensitivity study with respect to most influential operational variables, such as inlet total flow rate, steam-to-gas ratio, pressure, and concentrations of chlorine, hydrogen, carbon monoxide, and inert content, was carried out. (c) 2005 American Institute of Chemical Engineers.