CO-free H-2 in close to stoichiometric amounts was produced continuously at a constant H-2 production rate by the stepwise steam reforming of methane at low temperature (500 degreesC) in two parallel catalytic reactors operated in cyclic manner. The process involved two simultaneous reactions: first, catalytic decomposition of methane to H-2 and carbon (deposited on the catalyst), and second, gasification of the carbon deposited on the catalyst by steam to H-2 and CO2. The two reactions were carried out separately in two parallel reactors (both containing the same Ni-containing catalyst), operated in cyclic manner by switching a methane-containing feed and a steam-containing feed between the two reactors at a predecided interval of time. The process shows best performance at an optimum value of the feed switchover time. Among the different Ni-containing metal oxide (ZrO2, MgO, ThO2, CeO2, UO3, B2O3 or MoO3) and zeolite [HZSM-5, H beta, HM, NaY, Ce(72)NaY, or Si-MCM-41] catalysts, the Ni/ZrO2 and Ni/Ce(72)NaY showed promising results for the cyclic process. (C) 2001 Academic Press.