Kinetics of the catalytic isomerization and disproportionation of rosin over carbon-supported palladium

The kinetics of the catalytic isomerization and disproportionation of rosin over a Pd/C catalyst was investigated, using a novel experimental setup with a double-tier paddle agitator and specially designed sampling system, in No. 200 solvent oil and under a nitrogen atmosphere. The catalyst was characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD) and nitrogen physisorption. Kinetic experiments, designed to eliminate mass transfer effects, were carried out at temperatures ranging from 483 to 533 K by gas chromatographic analysis of samples that were withdrawn at different intervals. A kinetic model for catalytic isomerization and disproportionation of rosin over a Pd/C catalyst was proposed, and the various activation energies were determined for the isomerization of neoabietic acid to abietic acid (156.14 kJ mol−1), the isomerization of palustric acid to abietic acid (78.80 kJ mol−1), the dehydrogenation of abietic acid to dehydroabietic acid (108.56 kJ mol−1), the hydrogenation of abietic acid to hydrogenated abietic-type resin acids (105.75 kJ mol−1) and the hydrogenation of pimarenoic acid-type resin acids to hydrogenated pimarenoic acid-type resin acids (97.35 kJ mol−1). The results of the kinetic model agreed well with experimental observations within the initial experimental range and successfully predicted the concentration distribution of the products outside that range at 543 K.