Conversion of methanol to propylene(MTP)was comparatively studied over four zeolites with different topologies

em.e.SAPO-34

ZSM-48

ZSM-5 and beta at atmospheric pressure

450℃ and WHSV=1.5 h-1.The correlations between product selectivity

catalyst stability and zeolite topology were investigated.Besides

coking behavior of the four zeolite catalysts during the reaction was also discussed.Among the studied catalysts

SAPO-34 with narrow 8-member ring openings showed the highest selectivity to light olefins(ethylene and propylene).However

it seems that the high density of acid site and the large cages of SAPO-34 resulted in an extremely fast coking deactivation.Beta zeolite with wide pore structure exhibited high propylene/ethylene(P/E)ratio

but the propylene selectivity was somewhat low due to the product distribution shifting towards heavier hydrocarbons.In contrast

ZSM-48 and ZSM-5 zeolite with 10-member ring openings gave higher propylene selectivity

but their deactivation rates were quite different.ZSM-48 zeolite with symmetrical straight channels underwent fast deactivation after a few hours on stream

while ZSM-5 zeolite with intersecting channel system presented superior resistance to coke deactivation.The significant difference in catalytic performance of the four zeolites could be mainly ascribed to the combined effect of shape selectivity for intermediates and products controlled by zeolites topology.