Abstract: Hydrogen gas is generated in a fluidized bed reactor by reacting gases namely steam and a hydrocarbon gas such as methane or natural gas in a fluidized bed of particulate catalytic material. The catalytic material is fluidized by injecting the mixture of the reacting gases at the bottom of the bed. Hydrogen generated within the bed is removed via a selectively permeable membrane that extends through the bed and through a freeboard area above the bed. The reaction is endothermic and therefore heat to maintain the bed at the desired temperature is added as required. Preferably a separator separates particulate catalytic material entrained in the gases in the freeboard area and delivers the particulate material separated from the gas back into the bed.