A fluid-wall reactor for high temperature chemical reactions comprising (A) a porous reactor tube, at least a portion of the interior of which defines a reaction zone, the tube being made of an electrically resistive, porous refractory material; (B) a pressure vessel enclosing the reactor tube to define an inert fluid plenum, the pressure vessel having at least one inlet for admitting the inert fluid which is directed under pressure through the porous tube wall to provide a protective blanket for the inside surface of the reactor tube; (C) means for introducing at least one reactant into the reaction zone, the reactants being directed in a predetermined path axially of the reactor tube and being confined by the protective blanket substantially centrally within the reaction zone; (D) means for passing an electric current through the reactor tube for heating the reactor tube to the temperature level at which it emits sufficient radiant energy to initiate and sustain the desired chemical reaction, the radiant energy being directed into the reaction zone to coincide with at least a portion of the path of the reactants; and (E) a heat shield disposed within the pressure vessel, substantially enclosing the reaction zone to define a black body cavity, the heat shield reflecting radiant energy toward the reaction zone.