STUDY ON REACION MECHANISM OF CATALYTIC HYDROGENATION OF ROSIN ON Pd/C CATALYST

The hydrogenated rosin was prepared by Pd/C catalyst and solvent process. The optimal process conditions such as temperature, pressure, solvent content (based on solution weight), catalyst content (based on rosin weight), reaction time and rotational speed, are 423K, S.OMPa, 50%, 0.14%, 60min and 520rmin~' respectively, have been gained by Uniform Design. The quality of hydrogenated rosin is better than specific standard of GB/T-14020-92.Equilibrium gas solubility of hydrogen in rosin liquid has been measured at various pressures (2.0~10.0MPa). The result shows that equilibrium gas solubility of hydrogen increases with temperature and pressure, and the solubility of hydrogen accords with Henry Law. The relationship of gas solubility coefficient with temperature and dissolution heat of hydrogen in rosin liquid have also been obtained, i.e., * = ?0526exp(-575.25 IT) and AHA=4.7826kJ-morl.The effects of internal diffusion and external diffusion were eliminated by improving rotational speed and decreasing the granularity of catalyst. When the rotational speed is more than 600rmm~1, and the granularity of catalyst is less than 60~80 y m, the catalytic hydrogenation of rosin enters the controlling region of kinetics. Under the optimal reaction condition of 423K and S.OMPa, the changes of resin acid compositions with reaction time has been traced on-line in the course of reaction, the result shows that hydrogenation of abietic-acid to abietenoic-acid and abietanoic-acid is a parallel reaction.The intrinsic kinetics of catalytic hydrogenation of rosin on Pd/C catalyst was investigated at temperature 403K to 433K and under pressure 3.0MPa to 7.0MPa. Based on the kinetic data, a suitable reaction model has been selected from 17 probable reaction mechanism models, i.e. the main component abietic-acid in rosin is not adsorbed, adsorption of atomic hydrogen with reaction between atomically adsorbed hydrogen on catalyst surface and abietic-acid could be the controlling step, the intrinsic kinetic equationka P could be written as: r = , and its reaction activation energy is20.773kJ-mor1. It is very necessary to provide a theoretical basis for the development of industrial process.