Deactivation and regeneration of TS-1/diatomite catalyst for hydroxylation of phenol in fixed-bed reactor

The performance of the TS-1/diatomite catalyst for hydroxylation of phenol was investigated in the fixed-bed reactor. The results show that the activity and the selectivity to product of the TS-1/diatomite catalyst decrease simultaneously with an increase of the reaction time, which indicates that the TS-1/diatomite catalyst has deactivated gradually during the reaction. The deactivated catalyst was characterized by XRD, UV-vis, FT-IR, N2 adsorption and thermogravimetric analysis techniques. It was found that the crystallinity of TS-1/diatomite catalyst decreased slightly, but the structure of TS-1 zeolite and the content of titanium in the framework were unchanged. Compared with the fresh catalyst, the channels of the TS-1/diatomite catalyst were blocked by the organic byproducts, to result in the obvious decrease in the surface area and pore volume of the deactivated catalyst. The deposited byproducts inside the channels of TS-1/diatomite can be removed by calcining at 550 °C or refluxing with dilute hydrogen peroxide, which makes the performance of the deactivated catalyst recover completely.