Selective hydrogenation of 3,4-dimethoxybenzophenone in liquid phase over Pd/C catalyst in a slurry reactor

Abstract

Selective hydrogenation of benzophenone to benzhydrol is industrially relevant. In the current work, selective hydrogenation of 3,4-dimethoxybenzophenone (3,4-DMBP) to 3,4-dimethoxybenzhydrol (3,4-DMBH) was investigated over 5 % w/w Pd/C and 5 % w/w Pt/C as catalysts in a slurry reactor. The effects of hydrogen partial pressure (0.2–1 MPa), catalyst loading (2.0 × 10⁻⁴ to 8.0 × 10⁻⁴ g/cm³), initial concentration of 3,4-dimethoxybenzophenone (5.0 × 10⁻⁶ to 1.5 × 10⁻⁴ mol/cm³) and temperature (40–70 °C) on rate of reaction and selectivity were studied. Effect of solvent such as methanol, ethanol, 2-propanol and tetrahydrofuran (THF) was also investigated. 5 % w/w Pd/C was the better catalyst with THF as the best solvent, which gave 100 % conversion and 80 % selectivity in 1 h for 0.5 MPa hydrogen pressure at 60 °C. The Langmuir-Hinshelwood-Hougen-Watson model was fitted. The intrinsic kinetics and mechanism of hydrogenation were established.