Preparation of a Catalyst Composite Silica Membrane Reactor for Steam Reforming Reaction by Using a Counterdiffusion CVD Method

A silica membrane prepared by a counterdiffusion CVD method using tetramethyl orthosilicate and O2 was applied to a steam reforming reaction of methane. This silica membrane showed hydrothermal stability for more than 80 h at 773 K under H2O/N2 = 3. The H2/H2O permeance ratio was about 290 after the hydrothermal stability test. Rh or Ni catalyst was dipped on a porous alumina substrate before chemical vapor deposition (CVD). As a result, a composite catalytic membrane of a hydrogen permselective silica layer and a catalyst layer was obtained. This catalyst composite membrane reactor was applied to steam reforming reaction to extract hydrogen. Rh catalyst showed better stability than that for Ni catalyst. Methane conversion was increased to 64.5% from the equilibrium value (31.4%) at 773 K under S/C = 2 by the Rh-dipped membrane reactor. High conversion of methane was due to high selectivity of H2/H2O that was confirmed by the simulation evaluation.