Preparation and characterization of high catalytic performance supported TS-2 zeolites for phenol hydroxylation

Abstract

Good inter-grown TS-2 zeolites layer is successfully prepared on the outer surface of porous millimeter α-Al2O3 sphere by secondary hydrothermal synthesis. The supported TS-2 zeolites are loaded into a fixed-bed catalytic reactor for catalyzing phenol hydroxylation by hydrogen peroxide, which could efficiently avoid the fussy separation process. Influences of synthesis parameters on Ti active micro-environment, crystal morphology and catalytic performance of the supported TS-2 zeolites are investigated in this work, medium isopropanol content is necessary for preparing fine and homogenous TS-2 zeolites layer on the porous α-Al2O3 sphere. Besides, formation process of the supported TS-2 zeolites is studied in this study, which divided into three stages, dissolution of seed crystals, formation of novel nuclei, growth and aggregation of TS-2 zeolites layer. When the titanium source, isopropanol/SiO2 and TiO2/SiO2 molar ratio of the initial synthesis gel are tetrabutyl titanate, 1.0 and 0.035, tetra-coordinated titanium containing and compact TS-2 zeolites layer are fully covered on the α-Al2O3 sphere, the optimum phenol conversion and dihydroxybenzene selectivity of the zeolites are 40.07% and 98.52% at 65 °C.