Controllable synthesis of ultra-tiny nano-ZSM-5 catalyst based on the control of crystal growth for methanol to hydrocarbon reaction

Abstract

A series of aggregated nano-ZSM-5 with controlled crystal size (<100 nm) were prepared via low temperature hydrothermal synthesis and utilized for the study of particle size effect of ZSM-5 on methanol to hydrocarbon (MTH) reaction for the first time. The textural and acidic properties of ZSM-5 at different crystal growth process were characterized and analyzed by N2-sorption, XRD, NH3-TPD, TEM, SEM, TG, Py-IR and XPS. Two stages of crystal growth were found during the synthesis which could be used to guide the controlled synthesis of ultra-tiny nano-ZSM-5. According to catalytic performance, it was found that compared to external acid sites, internal acid sites play a crucial role on the synthesis of gasoline products. A positive relationship was found between the acidity and liquid hydrocarbon yield. In nanometer scale (<100 nm) the crystal size and acidity of ZSM-5 still strongly influenced the catalytic performance and a balance existed between the crystal size control and acidity regulation for the catalytic stability. This work could attract more attention on the structure fine control of nanoscale ZSM-5 catalyst.