Liquid-phase Alkylation of Toluene by Benzyl Alcohol over Micro-mesoporous Hierarchical Mordenite Zeolite

Abstract

In this work, post-synthetic effective acid (HNO3) and base (NaOH) etching technique are used to create hierarchical mordenite having different pore structure. The powder X-ray diffraction (P-XRD) technique was used to confirm the crystalline structure of the base modified and acid modified mordenite. Field emission-Scanning electron microscope (FE-SEM) was employed to confirm the structural morphology of the materials. The modified mordenite were further characterized by Inductive coupled plasma-optical emission spectrometry (ICP-OES), N2 adsorption-desorption isotherms, thermogravimetric analysis (TGA), acid base titration, to confirm the structural integrity, presence of active acidic sites, and other vital parameters. The structure was well conserved after the change, as evidenced by the characterization. The toluene alkylation with benzyl alcohol using hierarchical Mordenite and H-Mordenite produced mono-benzylated toluene. Comparison between acid treated, base treated and H-Mordenite was done. All samples were catalytically active as proved by the catalytic result in the alkylation reaction. The results show that the base alteration dramatically enhances the mesoporous surface area of H-Mordenite. Furthermore, the acid treated Mordenite had the highest benzyl alcohol conversion (75%), but the base modified Mordenite had benzyl alcohol conversion of 73% with the highest mono-benzylated toluene selectivity (61%). The process was further optimised by varying the reaction temperature, duration, and catalyst quantity. Gas Chromatography (GC) was used to evaluate the reaction products and gas chromatography-mass spectrometry (GC-MS) was used to confirm them. Introduction of mesoporosity in the microporous Mordenite was found to have significant effect on their catalytic activity.