Determination of the Low-Temperature Water-Gas Shift Reaction Kinetics Using a Cu-Based Catalyst

An integral packed-bed reactor was used to determine the kinetics of the water-gas shift (WGS) reaction over a CuO/ZnO/Al2O3 catalyst, under operating conditions such that there was no film or intraparticle resistance. Experiments were carried out over a wide range of temperatures and space times using a typical reformate gas mixture (4.70% CO, 34.78% H2O, 28.70% H-2, 10.16% CO2, balance N-2). In the first part of the work, three different mechanistic-rate equations and two empirical kinetic models are proposed to describe the WGS kinetic data throughout the entire range of temperatures. To improve the independence of the parameters in using the Arrhenius and van't Hoff equations, the temperature was centered. Good agreement was obtained between the Langmuir-Hinshelwood (LH) rate equations and the experimental results. Further, analysis using two different temperature ranges for parameter estimation revealed distinct rate-controlling mechanisms for each range. For temperatures of 180-200 degrees C, the associative (LH) mechanism was predominant, whereas the redox pathway showed the best fit to the experimental reaction rates in the range of 230-300 degrees C. Finally, an isothermal plug-flow reactor model was used to simulate the packed-bed tubular reactor for the WGS reaction using the composed kinetics. The reactor model was assessed against the experimental CO outlet concentration, and satisfactory agreement was found between the model predictions and the experimental results.