Research On The Catalytic Oxidation Of Benzyl Alcohol By Mo/SiO₂

Alcohol selective oxidation reaction plays a very important role oxidation reaction, some important chemical products and chemical intermediates were obtained through alcohol selective oxidation. Benzaldehyde, a kind of important intermediates and fine chemical materials, widely used in dyes, medicine, pesticide, etc is produced by partial oxidation of benzyl alcohol. This papers highly isolation or high dispersed transition metal ions molybdenum were supported on SiO₂ and used solid-phase and gas-solid phase oxidation reaction on benzyl alcohol, respectively. ESR, UV-vis, FI-IR and BET, etc were taken part in studying characterization of the catalysts, the experiment results of this work are as follows:1 The Mo/SiO₂ catalysts gave certain activity for the oxidation reaction of benzyl alcohol. The activity of catalysts and selectivity of benzaldehyde by highly isolation were caused by the transition metal ions. At least there were two activity centers: highly segregated transition metal ions and polymerization of transition metal ions. Highly segregated transition metal ions generated primarily target product benzaldehyde and the polymerization of transition metal ions were generated byproduct.2 The catalysts Mo/SiO₂ prepared by ion beam implantation and impregnation gave 100% benzaldehyde selectivity in the liquid-solid reaction system when metal load on 0.00936%wt. While the metal load over 0.1% by impregnation were used, the selectivity of benzaldehyde was less than 70%.3 The optimum reaction conditions for gas-solid phase benzyl alcohol selective oxidation is as followed. Reaction temperature 673K, total velocity 40 mL/min,O₂:He=1:5. In this reaction condition the conversion of benzyl alcohol was 28.3% and benzaldehyde selectivity was 90.3%, when the catalysts prepared by ion beam implantation were used. When the catalysts prepared by impregnation used have the same metal load with the catalysts prepared by ion beam implantation, the conversion of benzyl alcohol was 25.7%, selectivity of benzaldehyde was 63.5%. The catalysts prepared by impregnation method, loading 0.05wt.% Mo on SiO₂ gave the highest reactivity, the conversion of benzyl alcohol was 58.8%, selectivity of benzaldehyde was 86.2% .4 The highly isolated catalyst, the ion beam implantation catalyst and the catalyst prepared with impregnation method are showing good reproducibility. Results show that after the second and the third reaction, the conversion of benzyl alcohol and selectivity of benzaldehyde didn't lower than the first time. However, benzaldehyde selectivity showed more optimum.