CH4 Decomposition with a Pd−Ag Hydrogen-Permeating Membrane Reactor for Hydrogen Production at Decreased Temperature

The decomposition of CH 4 into C and H 2 over Ni/SiO 2 was investigated with a Pd−Ag hydrogen-permeating membrane reactor. The CH 4 decomposition reaction hardly proceeded at temperatures lower than 773 K in a conventional fixed-bed reactor because of a chemical equilibrium limit. However, the conversion of CH 4 was dramatically increased by removing the formed hydrogen by the Pd−Ag membrane. Because higher CH 4 decomposition conversions were achieved at higher hydrogen removal rates in the Pd−Ag membrane, the removal of the formed hydrogen seems to be the key step for CH 4 decomposition reaction at decreased temperature. Because a higher hydrogen permeation rate was achieved on the Pd(77)−Ag(23) membrane than on the Pd(90)−Ag(10) membrane, the CH 4 conversion was always higher in membrane reactors using Pd(77)−Ag(23) than in reactors using Pd(90)−Ag(10) for the hydrogen separation membrane. The CH 4 conversion increased with increasing contact time of the reactant and/or with increasing sweep Ar flow rate, because the hydrogen removal rate was improved. Consequently, this study revealed that CH 4 decomposition into CO and H 2 can occur with sufficiently high conversion (>88%) at 773 K and this process can provide hydrogen at decreased temperature.