Fe3+-Exchanged Titanate Nanotubes: A New Kind of Highly Active Heterogeneous Catalyst for Friedel-Crafts Type Benzylation

Yunchen Du,Yanwu Qi,Ping Xu,Chenkui Cui,Meiling Xiong,Xijiang Han,Di Guo,Jun Ma

doi:10.1155/2015/738089

Abstract

Heterogeneous catalysis for Friedel-Crafts type benzylation has received much attention in recent years due to its characteristic of environmental benefits. In this paper, titanate nanotubes (TNTs) were employed as heterogeneous catalyst support, and a new kind of Fe3+-exchanged titanate nanotubes (Fe-TNTs) catalyst with highly dispersed ferric sites was constructed by an ion exchange technique. The obtained catalyst was systematically characterized by XRD, TEM, N2adsorption, XPS, and UV-vis spectra. As expected, Fe-TNTs showed excellent catalytic activities in the benzylation of benzene and benzene derivatives. The recycling tests for Fe-TNTs were also carried out, where the reason for the gradually decreased activity was carefully investigated. Superior to some reported catalysts, the catalytic ability of used Fe-TNTs could be easily recovered by ion exchange again, indicating that Fe-TNTs herein were a highly active and durable heterogeneous catalyst for Friedel-Crafts type benzylation. These results might be helpful for the design and preparation of novel heterogeneous catalysts by combining the structural advantages of titanate nanotubes and active metal ions.

Highlights

Friedel-Crafts type benzylation, typically reacted between aromatic compounds and benzyl chloride/alcohol, is a classical chemical reaction for the production of diphenylmethane and substituted diphenylmethanes, which can be widely used in the fields of pharmaceuticals, agrochemicals, fine and bulk chemicals, and dielectric oil formulations [1, 2]
To evaluate the catalytic ability of Fe-titanate nanotubes (TNTs), we examined the conversion of benzyl chloride (BC) over different heterogeneous catalysts, including Fe-containing mesoporous silica (Fe-JLU-15), Fe-containing zeolites (FeZSM-5), and sulfated zirconia, which are prepared according to previous literatures [11, 16, 53]
Fe3+-exchanged titanate nanotubes (Fe-TNTs) were universal for the benzylation of benzene and its derivatives, where the poisonous phenomenon by the adsorption of aromatic substrates in some previous catalysts was not observed

Summary

Introduction

Friedel-Crafts type benzylation, typically reacted between aromatic compounds and benzyl chloride/alcohol, is a classical chemical reaction for the production of diphenylmethane and substituted diphenylmethanes, which can be widely used in the fields of pharmaceuticals, agrochemicals, fine and bulk chemicals, and dielectric oil formulations [1, 2]. Following the advanced development of green chemistry, various kinds of heterogeneous solid catalysts, for example, zeolites, metal oxides, sulfated zirconia, clay, doped mesoporous silica, and heteropoly acids, for Friedel-Crafts type benzylation have been extensively studied in past decades [4,5,6,7,8,9,10,11,12,13,14,15] Among those different active sites in heterogeneous catalysts, Fe-containing sites have received more and more attention due to their superior catalytic activities and low cost. It may be an effective method to further improve

Methods

Results

Conclusion