Quaternary ammonium cellulose promoted synthesis of hollow nano-sized ZSM-5 zeolite as stable catalyst for benzene alkylation with ethanol

Abstract

Catalytic alkylation of benzene with ethanol has been considered as a sustainable alternative for producing ethylbenzene/diethylbenzene. This paper reports the promoted synthesis of hollow nano-sized (20–80 nm) ZSM-5 zeolite as excellent yet durable catalyst of benzene alkylation, which is achieved by adding N-methyl-2-pyrrolidone (NMP) and quaternary ammonium cationic hydroxyethyl cellulose (JR-400) in its synthesis gel during the synthesis. It is revealed by the ESI–MS and TEM characterization that the NMP promotes the dissolution–recrystallization of the ZSM-5 and a hollow structure is generated during the process. The JR-400 as special promoter further favors the formation of ordered nano-zeolite grain and suitable microstructure, confirmed by the molecular dynamic modeling and characterization. That action corporately contributed to the hollow nano-sized ZSM-5 zeolite that provided hierarchical porous structure and mild acid centers, as evidenced by the 129Xe and 1H NMR spectra. The obtained hollow zeolite ZSM-5 then exhibits enhanced catalytic activities and selectivity for benzene alkylation. Moreover, it also displays an extremely superior stability (deactivation rate constant, −0.06%/h) in the catalysis of benzene alkylation with ethanol. This behavior is attributed to its hierarchical porous structure (namely less diffusion resistance) and mild acid centers, which is beneficial to moderate the carbon deposition and then the catalyst deactivation. Those research results urge the JR-400-promoted synthesis as a facile strategy for the hollow nano-sized ZSM-5 with enhanced catalytic performance during the benzene alkylation with the ethanol.