Reaction kinetics of hydrogen and aqueous sodium and potassium bicarbonate catalysed by palladium on activated carbon

The intrinsic reaction kinetics of hydrogen and the aqueous bicarbonate ion has been studied in the presence of a Pd/C catalyst up to saturation of the salt solution. Experiments were carried out at temperatures of 20, 40 and 60°C and at hydrogen pressures ranging from 1-20 bar using a mechanically agitated slurry reactor. Based on the initial rates, it is proposed that in the rate determining step a surface reaction between unadsorbed bicarbonate and associatively adsorbed hydrogen is involved. A Langmuir-Hinshelwood type rate equation has been derived, which is based on the activities of the reacting species. Evaluation of the experimental data resulted in approximate values of the activation energy for the sodium and potassium salt. These were found to be about 23-25 kJ mol^-1. A good correlation (within 10% error) was demonstrated between the predictions of the proposed rate equation and the experimental data at a constant carbon dioxide pressure of about 1 bar.