Abstract: Modular, stackable, flow-through plate or channel reactor units for continuous, low temperature, catalytic reactions of two separate process reaction streams; typically the first is an exothermic combustion process and the second, an endothermic reforming process. Each reactor unit comprises two separate sets of flow channels or slot-type reaction zones formed in flow plates located between spaced, thin metal, highly heat-conductive metal foil or platelet separator walls, adjacent reactors in a stack including a common, medially located, bi-catalytic separator plate, i.e., a separator plate having on opposed surfaces the same or different catalysts selected for the particular reaction taking place in the adjacent reactor zone. Each flow plate has a relieved medial area defining the reaction zone, the side walls of which are the catalyst coated separator platelets.