Selective production of light olefins from methanol over desilicated highly siliceous ZSM-5 nanocatalysts

Abstract

Highly siliceous ZSM-5 nanocatalysts can dehydrate methanol to a wide range of hydrocarbons. In this study, the development of hierarchical H-ZSM-5 nanocatalysts (Si/Al=200) were reported for the methanol-toolefins (MTO) reaction. The nanocatalysts were prepared through a hydrothermal technique and treated by NaOH desilication. The parent and desilicated nanocatalysts were characterized using FE-SEM, XRD, FTIR, NH3-TPD and N2 adsorption-desorption techniques. The mesoporosity increased five times without significant collapse of the crystalline framework as a result of the appropriate desilication of H-ZSM-5 nanocatalyst. For the nanocatalyst, a high surface area of 189.5 m2 g-1, mesopore volume of 0.35 cm3 g-1 and well-adjusted strong acidity of 0.16 mmol NH3 g-1 resulted in a high methanol conversion of 100%, high propylene selectivity of 43% and low light paraffins selectivity of <8% in the MTO reaction. A broad mesopore size of 2-10 nm suppressed coke deposition and provided a long catalytic life time of 75 h. The developed high silica nanocatalyst showed a high potential for industrial applications due to its stable performance.