Improved ethylbenzene suppression and coke-resistance on benzene methylation over metals doped fibrous silica-HZSM-5 zeolite

It is well recognized that the side reaction of methanol to olefin is challenging to suppress in benzene methylation, which leads to the production of the undesired ethylbenzene and coke. In this study, the effect of transition metals (Co, Mn and Ti) on the fibrous silica ZSM-5 zeolite (HFZ) for benzene methylation was investigated. The characterization results showed that the addition of transition metals into HFZ has reduced the surface area and obtained different acidities proportions, suggesting the successful incorporation of those metals into HFZ. The Mn/HFZ appeared to be the optimum catalyst as it exhibited the high suppression of ethylbenzene with a high yield of toluene (69.6%) due to the adequate acidity that originated from the existence of more interaction of Mn and HFZ. Also, the Mn/HFZ catalyst remained active for the 75 h time-on-stream, together with the absence of graphitic carbon in post-characterization analyses. This suggests that its excellent catalytic performance may be attributed to the preservation of the most active sites as a result of the enhanced methanol and benzene adsorption on the catalyst surface.