Effect of nickel loading on the performance of nano- and micro-sized ZSM-5 catalysts for methanol to hydrocarbon conversion

Methanol to hydrocarbon process is becoming increasingly important as methanol can be manufactured from flare gas, biomass, shale gas and coal. In this work, micro- and nano- sized ZSM-5 zeolites have been modified with low level nickel loading and tested for methanol to hydrocarbon process. It is shown that nano-sized ZSM-5 catalyst doped with nickel with or without H2 reduction has higher yield of hydrocarbon than the micro-sized ZSM-5 catalyst. Pretreatment of the NiO/ZSM-5 catalyst with H2 reduction does not decrease aromatics yield in the hydrocarbon products, but in contrast increases the yield of C1-C4 gaseous products, which may be due to the lower loading (1.0% in wt.) of nickel metal substitution. The introduction of NiO to ZSM-5 catalyst increases acid amount and also acid strength, which may be due to the nickel entering the framework, thus changing the coordination environment of Si and Al. The structure of nano-sized ZSM-5 catalyst is more affected by the loading of nickel, such as more AlO5 units. In terms of catalytic performance, nano-sized ZSM-5 catalyst has high yield for hydrocarbon production, less gaseous yield, and less aromatics, which is probably due to the shorter distance for the diffusion and contact time of the dehydrated products over the acid sites