Propylene/propane and ethylene/ethane separation was examined with Ag-exchanged X-type zeolite membrane (Ag-X membrane). The Na-X membrane was prepared on a porous tubular α-alumina support by a secondary growth method. The resulting Na-X membrane was ion-exchanged by using AgNO 3 aq. Olefin selectivities in both mixtures were markedly improved after the ion exchange from Na to Ag cation. The Ag-X membrane exhibited a maximum propylene selectivity of 55.4 with a permeance of 4.13 × 10 −8 mol m −2 s −1 Pa −1 at 353 K for a propylene/propane (50:50) mixture. This membrane also exhibited a maximum ethylene selectivity of 15.9 with a permeance of 9.04 × 10 −8 mol m −2 s −1 Pa −1 at 303 K for an ethylene/ethane (50:50) mixture. We consider that the strong interaction between olefin and Ag cation plays an important role for the appearance of such high selectivity of olefin.

A silica membrane prepared by a counterdiffusion CVD method using tetramethyl orthosilicate and O 2 was applied to a steam reforming reaction of methane. This silica membrane showed hydrothermal stability for more than 80 h at 773 K under H 2 O/N 2 ) 3. The H 2 /H 2 O 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 H 2 /H 2 O that was confirmed by the simulation evaluation.

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Long-term durability tests of dimethoxydiphenylsilane-derived silica membranes for purifying H 2 from H 2 − toluene mixtures were carried out. The silica membrane maintained excellent H 2 -selective performance under H 2 −toluene mixture condition, despite H 2 permeance was decreased from its initial value. Membrane performance changed in two steps. Performance initially decreased rapidly, and then decreased very slowly. We also examined membrane performance using H 2 − dehydrated toluene and H 2 −water mixtures, and it was indicated that adsorption of toluene molecules and water molecules dissolved in toluene on membrane surfaces was the predominant factor for the rapid initial decrease. Water molecules present within toluene also affected the subsequent slower decrease. These decrements were partially recovered by placing the membranes in an H 2 stream. Incomplete recovery during regeneration was due to the strong effect of water molecules dissolved in toluene, even though the amount of water was quite small.