Abstract
Background: The preparation of hierarchical Y is of practical importance for industrial applications. Here, we utilized NaY or NH4Y as parent material to investigate its influence on catalytic performance of hierarchical Y prepared by post-treatment method. It was found that the hierarchical Y obtained by treating NaY exhibited superior catalytic performance than that by NH4Y in the benzylation of aromatics with benzyl chloride and the acid-washing step after alkali-leaching could not help improve the catalytic performance.
Methods: The techniques of XRD, N2 sorption, SEM, NH3-TPD, and XPS were used to characterize the textural properties of catalysts. The benzylation reactions of aromatics with benzyl chloride were used as probe reactions to evaluate the catalytic performance of samples. Results: NaY and NH4Y were used as parent materials to prepare hierarchical Y by performing a variety of acid and base treatments. The type of parent Y had a big influence on catalytic performance of the obtained hierarchical Y. The hierarchical Y prepared by using NaY exhibited better catalytic performance than that by using NH4Y in the benzylations. The catalyst MY-Na prepared without acid wash exhibited superior catalytic performance than MY-Na with acid wash and parent Y in the benzylation of aromatics with benzyl chloride. In the benzylation of benzene, BC conversion over MY-Na is nearly twice as that over HY, which could be mainly attributed to the improvement of mass transfer ability. In the case of p-xylene or mesitylene with relatively large molecular size, BC conversion over MY-Na is three times more than that over HY. The inaccessibility of acid sites in micropores should be partly responsible for the low catalytic activity of HY. Conclusion: A catalyst with good combination of accessible acid sites, mesopore volume and external surface area would give superior catalytic activity in the benzylation. Further, hierarchical Y could be reused and almost maintain the initial catalytic activity. It has been demonstrated that hierarchical Y has potential applications in Friedel-Crafts alkylations, especially of large molecules.Keywords: Hierarchical, zeolite Y, mesopore, benzylation, alkylation.
Graphical Abstract
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