Connecting active-site chemistry with observed macroscopic kinetic behaviour is required to rationally design active sites of heterogeneous catalysts. Isolated active sites limit co-adsorption complexities, which challenge reconciling elementary reaction mechanisms and rate constants to observed macroscopic kinetics. The Pd–Zn γ-brass intermetallic phase enables the controlled synthesis of Pd1 monomer and Pd3 trimer sites isolated in an inert Zn matrix. Here we utilize these isolated sites, combining experimental kinetic measurements, density functional theory (DFT) calculations and a fully coverage-enumerated microkinetic model (MKM) to provide detailed mechanistic understanding of elementary reaction chemistry for ethylene hydrogenation. With isolated sites reducing the complexity of co-adsorption coverage effects, remarkable agreement between experimental and DFT-MKM kinetics is reached. The acute temperature dependence of reaction orders, the site competition between C2 species and hydrogen, the degree of rate control of elementary reactions and the steady-state distribution of co-adsorption configurations are reconciled. [Figure not available: see fulltext.].
All Science Journal Classification (ASJC) codes
- Process Chemistry and Technology