Kinetics of the water–gas shift reaction over nanostructured copper–ceria catalysts

Water–gas shift reaction was studied over two nanostructured Cu_xCe_1?xO_2?y catalysts: a Cu_0.1Ce_0.9O_2?y catalyst prepared by a sol–gel method and a Cu_0.2Ce_0.8O_2?y catalyst prepared by co-precipitation method. A commercial low temperature water–gas shift CuO–ZnO–Al₂O₃ catalyst was used as reference. The kinetics was studied in a plug flow micro reactor at an atmospheric pressure in the temperature interval between 298 and 673 K at two different space velocities: 5.000 and 30.000 h^?1, respectively. Experimentally estimated activation energy, E_af, of the forward water–gas shift reaction at CO/H₂O = 1/3 was 51 kJ/mol over the Cu_0.1Ce_0.9O_2?y, 34 kJ/mol over the Cu_0.2Ce_0.8O_2?y and 47 kJ/mol over the CuO–ZnO–Al₂O₃ catalyst. A simple rate expression approximating the water–gas shift process as a single reversible surface reaction was used to fit the experimental data in order to evaluate the rate constants of the forward and backward reactions and of the activation energy for the backward reaction.