Plating thin Pd or Pd-Ag alloy film on the outer surface of a porous alumina ceramic tube enables very rapid hydrogen permeation with an absolute selectivity based on the solution-diffusion transport mechanism. Effectiveness, such as displacement of thermodynamic equilibrium, selectivity enhancement, is brought forth by incorporating the metal/ceramic composite membrane in the catalytic reactor, as demonstrated in concrete examples of steam and CO2 reforming of methane and dehydrogenation of isobutane. It is also shown that the membrane reactor occasionally requires its own catalyst which is different from conventional ones.