Near-Unity Reaction Probability in Olefin Hydrogenation Promoted by Heterogeneous Metal Catalysts.
The kinetics of the hydrogenation of ethylene on platinum surfaces was studied by using high-flux effusive molecular beams and reflection-absorption infrared spectroscopy (RAIRS). It was determined that steady-state ethylene conversion with probabilities close to unity could be achieved by using beams with ethylene fluxes equivalent to pressures in the mTorr range and high (≥100) H2:C2H4 ratios. The RAIRS data suggest that the high reaction probability is possible because such conditions lead to the removal of most of the ethylidyne layer known to form during catalysis. The observations from this study are contrasted with those under vacuum, where catalytic behavior is not sustainable, and with catalysis under more realistic atmospheric pressures, where reaction probabilities are estimated to be much lower (≤1 × 10(-5)).
Department of Chemistry, University of California, Riverside, 900 University Avenue, Riverside, California 92521, United States.
Maryam
M
Ebrahimi
Department of Chemistry, University of California, Riverside, 900 University Avenue, Riverside, California 92521, United States.
Juan Pablo
JP
Simonovis
Department of Chemistry, University of California, Riverside, 900 University Avenue, Riverside, California 92521, United States.
Francisco
F
Zaera
ethylidyne; infrared absorption spectroscopy; kinetics; molecular beam; operando; platinum