Kinetic model for the catalytic disproportionation of pine oleoresin over Pd/C catalyst

•Pine oleoresin is an important forestry product and can be modified by catalytic disproportionation.•We proposed a new reaction scheme together with a lumped kinetic model.•The various activation energies and pre-exponential factors were obtained.•Dehydrogenated acid and p-cymene were main components in the final products

The kinetics of the disproportionation of pine oleoresin (a renewable bioresource) over a carbon-supported palladium catalyst was studied. Kinetic experiments, constructed to eliminate internal and external mass transfer limitations, were performed in the temperature range of 210-250 °C. The samples, withdrawn from reaction mixtures at different intervals, were determined by GC-MS and GC. A new reaction scheme together with a lumped kinetic model was proposed to describe the complex reaction system. The kinetic parameters for each involved reaction were estimated using the Levenberg-Marquart method by MATLAB software. The various activation energies of rosin acids in pine oleoresin, for the isomerization, dehydrogenation and hydrogenation reactions, were 83.05-172.75 kJ mol−1. The various activation energies of monoterpenes in pine oleoresin, for the dehydrogenation and hydrogenation reactions, were 103.97-133.82 kJ mol−1. The kinetic model well fitted the experimental observations and could be used to predict the concentration distribution of the products at 260 °C. The results showed that the disproportionations of rosin acids and monoterpenes followed second order and first order reactions, respectively. In addition, dehydrogenation was the main reaction in the disproportionation of pine oleoresin. Dehydrogenated acid and p-cymene were main components in the final products.