A UBI–QEP microkinetic model for the water–gas shift reaction on Cu(1 1 1)

Utilizing the conventional transition state theory along with the unity bond index–quadratic exponential potential method to predict elementary reaction step energetics, a microkinetic model is developed that quantitatively describes the kinetics of the water–gas-shift reaction (WGSR) on a Cu(1 1 1) catalyst. The model is further analyzed, simplified and dramatically reduced without sacrificing accuracy by employing the systematic reaction route (RR) analysis algorithm developed recently by us (Ind. Eng. Chem. Res. 40 (2001) 2416). It is shown that only three from the total of 17 possible overall RRs dominate the kinetics of the WGSR on Cu(1 1 1). Namely, the formate and associative RRs are dominant at lower temperatures while the redox RR is dominant at higher temperatures. Utilizing the quasi-equilibrium and steady-state assumptions, the microkinetic model is further reduced to a two-step mechanism model similar to that of Temkin. The corresponding explicit rate expression with all parameters predicted apriori provides excellent agreement with the complete microkinetic model.