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

Catalytic combustion of propane in a membrane reactor with separate feed of reactants. I: Operation in absence of trans-membrane pressure gradients

A pilot plant study on propane catalytic combustion in a membrane reactor with separate reactant feeds is presented. The membrane consisted of a porous alumina tube activated by insertion into its pores of a Pt/γ-Al2O3 catalyst. The role of reactants concentration and of the feed flow rates were studied in the transport-controlled operating regime, where a number of interesting properties of this reactor setup can be exploited (absence of reactant slip through the membrane, lower risks of thermal runaways, possibility of increasing conversion by application of a pressure difference over the membrane, etc.). Attention is here focused on operation in the absence of trans-membrane pressure gradients. The reactor fluid-dynamics are investigated, too. The experimental results are in good agreement with the predictions of an isothermal model, analytically solved and based on the simplifying assumption that the reaction takes place in a limited zone inside the membrane (i.e. a surface for infinitely fast reactions)