Kinetics of phenol hydroxylation reaction of open mesoporous TS-1 with high backbone titanium content

Abstract

High skeletal titanium content, open mesoporous TS-1 titanosilica molecular sieves with more accessible active centres exhibit higher catalytic activity, target product selectivity and resistance to coking deactivation in green catalytic oxidation reactions using hydrogen peroxide as oxidant. In this paper, TS-1 titania-silica molecular sieves without anatase, with the highest theoretical skeletal titanium content (2.0 wt%) and open mesopores (mesopore volume 0.71 cm3/g) were synthesised based on the ageing dry gel limited domain conversion method invented in previous research work. The intrinsic kinetics of the catalytic reaction of phenol with hydrogen peroxide for direct hydroxylation of benzenes was investigated. The effects of stirring rate, phenol concentration, hydrogen peroxide concentration, catalyst dosage and reaction temperature on the initial conversion rate of phenol were investigated, and the experimental data were fitted with a power function equation to obtain the intrinsic kinetic equation of the catalyst ( r = 2.98 × 10 6 exp ( − 56.43 × 10 3 R T ) c 1.07 ( Phenol ) c 0.10 ( H 2 O 2 ) ) \left( {{\rm{r}} = 2.98 \times {{10}^6}\,\exp \,\left( { - {{56.43 \times {{10}^3}} \over {RT}}} \right){c^{1.07}}\left( {{\rm{Phenol}}} \right){c^{0.10}}\left( {{{\rm{H}}_2}{{\rm{O}}_2}} \right)} \right) . Under the condition of eliminating the effect of internal and external diffusion, the reaction was 1.07 and 0.10 for phenol and hydrogen peroxide, respectively, with a reaction activation energy of 56.43 kJ/mol. This study provides a theoretical basis for the reactor and process design of hydroxylation of phenol to benzenediol based on this new catalyst.