Synthesis of hierarchical titanium silicalite-1 in the presence of polyquaternium-7 and its application in the hydroxylation of phenol

Hierarchical titanium silicalite-1 (TS-1) without generated anatase TiO2 species was synthesized in the presence of polyquaternium-7 (M550) by one-step hydrothermal crystallization method and characterized by field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, X-ray fluorescence (XRF), Fourier transform infrared spectra, ultraviolet visible spectra, Raman spectroscopy and N2 adsorption–desorption measurements. The experimental results show that highly porous TS-1 crystals, with pores of ca. 2.6–4.9 nm diameter, are obtained under hydrothermal conditions by using polyquaternium-7 as the mesopore-directing agent. The polyquaternium-7 has a great influence on both the textural properties and the coordination of Ti species in the framework of TS-1. The catalytic properties and recyclability of the prepared mesoporous TS-1 for hydroxylation of phenol with H2O2 have been evaluated, and their activity has been compared with those of TS-1 with only micropores. The great catalytic activity, selectivity and stability of the hierarchical TS-1 as well as the cheap price and environmental-friendly nature of the used mesopore-directing agent allow to consider this hierarchical TS-1 as a promising catalyst for industry application.