Influence of surface design on performance of MnO-decorated nanocatalyst for olefin production from methanol: ZSM-5@MnO core-shell versus MnO/ZSM-5 dispersed nanocatalysts

BACKGROUND In the assembly of nanoparticles (NPs) onto zeolites, the surface design of NPs has a great influence on various catalytic properties. Herein, ZSM-5 was hydrothermally synthesized and its external surface was decorated by MnO NPs in two different surface designs: distributed MnO NPs and MnO shell. RESULTS The synthesized MnO-decorated samples, MnO/ZSM-5 and ZSM-5@MnO, were analyzed using various techniques. The results of these analyses reveal the formation of desired crystal phases without any impurities and confirm the perfect assembly of uniform MnO NPs on the surface of ZSM-5. Also, it was found that the surface design of MnO NPs has a great impact on the physicochemical properties of the nanocatalyst. Basically, ZSM-5 is highly selective toward propylene, but the shape selectivity of MnO NPs increases the selectivity of MnO-decorated nanocatalysts toward ethylene. Moreover, this study delves deeply into differences in catalytic behaviors of the nanocatalysts during the methanol-to-olefin process and explains how they are attributed to the applied surface designs. CONCLUSIONS The catalytic performance studies at optimum temperature show that the ZSM-5@MnO nanocatalyst is more selective toward ethylene, and it has a nearly 20% higher methanol conversion rate compared to the MnO/ZSM-5 nanostructured catalyst. Due to the surface acidity adjustment of MnO shell as well as high control of core-shell structure over the location of coke formation, the ZSM-5@MnO nanocatalyst shows longer stability and its activity remains constant with time on stream. (c) 2020 Society of Chemical Industry