Highly Efficient Nanocrytalline Zeolite Catalyst for the Hydroxyalkylation of Anisole with Benzaldehyde

Abstract

The heterogeneous solid acid catalyzed hydroxyalkylation of arenes with benzaldehyde yields triarylmethane (TRAM) compounds which have gained significant attention due to their notable application in dyes, pharmaceuticals and the synthesis of various functional materials. In the present study the activity of nanocrystalline Beta and ZSM-5 zeolites was studied in the liquid phase hydroxyalkylation of anisole with benzaldehyde. The catalysts were characterized by Dynamic Light Scattering measurements, an X-ray diffraction study and scanning electron microscope and transmission electron microscope analyses. The reaction parameters, such as-catalyst loading, mole ratio, reaction temperature, and catalyst reusability were optimized. The efficiency of zeolite catalysts having different pore sizes was tested under the optimum reaction conditions. The results showed that the larger pore of nanocrystalline Beta exhibited the highest activity, which was due to the increased pore size of the crystal for the easy adsorption of reactants and the desorption of bulky products. It is important to highlight that the nanocrystalline Beta catalysts showed higher efficiency compared to other reported results in the literature, with the advantage of high activity, selectivity, separation of the catalyst and excellent reusability. Therefore, these catalysts can be used instead of conventional homogeneous catalysts such as AlCl3, ZnCl2 and H2SO4 for an eco-friendly selective production of tri aryl methane compounds.