Effect of reaction conditions on methanol to gasoline conversion over nanocrystal ZSM-5 zeolite

A nanocrystal ZSM-5 zeolite comprising uniform single crystal particles of ~100 nm in size was synthesised and characterised using XRD, ICP-AES, SEM, TEM, solid state MAS NMR and nitrogen physisorption techniques. The catalytic performance was tested in methanol to gasoline (MTG) conversion with a particular focus on the effect of reaction conditions, namely, temperature from 300 to 450 °C, pressure from 0.1 to 2.0 MPa and WHSV from 1 to 4 h^-1. Temperature showed a significant impact. At temperatures ≤350 °C, methanol conversion did not complete while the catalyst was deactivated more rapidly. Increasing temperature to above 375 °C saw complete methanol conversion and durable catalyst activity. Further increasing the reaction temperature to above 400 °C reduced gasoline yield. Pressure mainly affected the product selectivity; a higher pressure led to a lower C₁-C₄ selectivity but enhanced durene formation. Further increasing pressure also favoured coke formation, leading to faster loss of catalyst activity. Likewise, increasing WHSV reduced C₁-C₄ selectivity but promoted the formation of durene and coke, resulting in a rapid deactivation of the catalyst. The optimal reaction conditions for this nanocrystal ZSM-5 catalyst in MTG were found to be 375 °C, 1.0 MPa and WHSV of 2 h^-1.