Vanillin hydrodeoxygenation: Kinetic modelling and solvent effect

Vanillin hydrodeoxygenation was investigated using Pt/C catalyst in the temperature and total pressure ranges of 80-200 A degrees C and 20-30 bar in several solvents, such as tetrahydrofuran, 2-propanol, water and in solventless conditions using 1:1 mass ratio of vanillin to guaiacol. The results revealed that the rate increased with increasing solvent polarity as follows: tetrahydrofuran < 2-propanol < water. The main product was p-creosol with 66% selectivity at complete vanillin conversion in HDO under 30 bar total pressure at 100 A degrees C after 4 h using water as a solvent. In a solventless experiment with 1:1 mass ratio of vanillin-guaiacol as a feedstock only vanillin was transformed to p-creosol with 91% conversion in 4 h at 200 A degrees C under 30 bar total pressure, while guaiacol did not produce any HDO products. Both thermodynamic analysis and kinetic modelling were performed. Vanillin hydrodeoxygenation resulted in formation of p-creosol over Pt/C catalyst using an optimum vanillin initial concentration in water solution. From the industrial point of view vanillin hydrodeoxygenation proceeded rapidly giving high yields of p-creosol in solventless hydrodeoxygenation of vanillin-guaiacol mixture, while guaiacol was not deoxygenated.