Propyne Hydrogenation Kinetics over Surfactant-Stabilized Palladium Nanoclusters

Abstract

The kinetics of propyne hydrogenation over surfactant-stabilized palladium nanoclusters was studied in a batch reactor under isothermal conditions (308 K). The method of initial rates was adopted to elucidate the reaction mechanism and a rate equation was derived. Although the methodology employed does not exclude other reaction schemes, it was found that experimental rate data agree well with a Langmuir−Hinshelwood mechanism that involves noncompetitive adsorption between propyne and hydrogen for the catalyst surface, where hydrogen addition in the surface reaction(s) is the limiting step. Nonlinear model fitting to initial rate data provided the kinetic parameters of the rate equation (k (mol·gPd-1·s-1·bar-2) = 4.1; KC3H4 (bar-1) = 8.7 × 102; and KH2 (bar-1) = 1.0 × 10-5). Finally, experimental compositions of the reaction mixture over time, as well as the overall advancement history, were compared favorably with the kinetic model through integration of the mass balance in the batch reactor.