Abstract: The preparation of Pd composite membrane (Pd-CM) by impregnation or electroless plating was studied. The permeaselectivity to hydrogen and the catalytic activity
for the dehydrogenation of methanol to methy1 formate (MeF) of “Pd/SiO₂/ceramic?” membranes were measured. The results show that the quality of “SiO₂/ceramic
” substrate membrane has an influence on the properties of “Pd/SiO₂/ceramic?”. In the process of preparing Pd-CM, the growing mechanism of Pd surface membrane
in impregnation method is different with that in electroless plating method. When the same “SiO₂/ceramic” is used as a substrate membrane, the Pd-CM prepared
by electroless planting has a good behavior than by impregnation. Hydrogen in mixture gases of N₂/H₂ or H₂/CH₃OH, can be separated completely with the Pd-CM
prepared by impregnation at 150℃. For the topic reaction at 100℃, the higher conversion of methanol and lower selectivity to product MeF can be obtained
in the Pd-CM reactor prepared by electroless plating than that by impregnation. The Pd-CM was also characterized by SEM, XRD and the structure difference between two
Pd-CMs prepared with different methods was discussed.

Key words: Pd composite membrane, preparation, hydrogen separation, catalytic dehydrogenation, methanol