Kinetic studies of the water - gas shift reaction - A comparison of chemical catalysts

Abstract

There have been many studies on the kinetics of the . ...J water-gas shift reaction but the results are in poor a,gre'ement0 The aim of the present work was to investigate, in the same , equipment and under carefully standardised conditions, the -behaviour of a number of commercially used catalysts. In this way 1, t was hoped to determine whether the contrad~ation of results found in the literature could be ascribed to the different kinetic behaviours of these catalysts. As a secondary aim it was intended to obtain some clues to the mechanisms of this reaction although it was realised that the statistical design method used was not particularly suitable for the production of rate equations of great accuracy. A differential reactor Was used in this work. The commercial catalysts studied in this investigation "",;rethe products of Girdler Catalysts (G-3A and G-66B),A.B.' Svenska Saltpeterverken of Sweden, Power Gas and I.C.I.Limited, • All the catalysts except Girdler G-66B worked between 3500 to 4500C. Working temperature range of Girdler G-66B was 1800 to .0 /320.C. All studies were carried out at atmospheric pressu~e, Results showed activities of the shift catalysts of the order: .Girdler G-66B, SSV (Sweden), Power Gas, I.C.I., Girdler G-3A. ,Kinetic studies showed that the forward reaction was nearly first • order with respect to carbon monoxide for Power Gas, I.C.I. and Girdler G-3A catalysts, but fractional for SSV and Girdler G-66B - catalysts. The order of reaction with respect to steam was fr.a,ctional for all the catalysts. The order with respect to . hydrogen was zero for SSV catalyst, but retarding effects were .. 'obserVed for the rest. The fon'iard reaction was unaffected by carbon dioxide for Girdler G-66B, but retarded in the. case of the rest of the catalysts, • • .. " • • • • • •• • • \ • • ... ' • • I , • \ .•. 1#". • . .. From these results it is bOficluded that the divergence in results can be ascribed to the different behaviour of individual catalysts. Comparison with previous work using the SSV catalyst gives good agreement with the present results. An expotential -t.ype of rate equation is shown to be of sufficient aCcur,acy to be used for the purpose of reactor design, but a ~ougen~ Watson type rate equation based on a possible reaction mechanism does not agree with the results obtained.