Improved benzene production from methane dehydroaromatization over Mo/HZSM-5 catalysts via hydrogen-permselective palladium membrane reactors

The effectiveness of hydrogen-permselective palladium membrane reactors for non-oxidative methane dehydroaromatization (MDA) over 4 wt% Mo/HZSM-5 catalysts was investigated as a function of weight hourly space velocity (WHSV) at 700 degrees C and atmospheric pressure. CH4 conversion and aromatic product yield decrease with increasing WHSV from 750 to 9000 cm(3) g(cat)(-1) h(-1). C6H6 is the main C-containing product at and below 3000 cm(3) g(cat)(-1) h(-1) whereas C2H4 dominates the C-product distribution at higher WHSVs. Due to selective removal of H-2 from the reaction products in catalytic membrane reactors, C6H6 yield is significantly improved over the whole WHSV range compared to those obtained in fixed-bed reactors. H-2 recovery is strongly influenced by WHSV as it decreases from 48.3% at 750 cm(3) g(cat)(-1) h(-1) to 6.8% at 9000 cm(3) g(cat)(-1) h(-1). There exists a trade-off between catalytic activity and H-2 recovery, which results in the maximum enhancement (similar to 360%) in C6H6 yield at 3000 cm(3) g(cat)(-1) h(-1). At this intermediate space velocity, the largest concentration of H-2 is found in the retentate stream and helps alleviate coke accumulation particularly on HZSM-5. Carbon is deposited on the inner surface of the membrane reactor portion in contact with the catalyst bed and transports to the outer surface, thus causing H-2 permeability to decrease over the 15 h reaction period.