Watergas shift reaction

Application of wavefront analysis to watergas shift reaction... 

We report here about the investigation of the low temperature watergas shift reaction on an industrial catalyst (GIRDLER G 66-B and E with copper and zinc oxides as main components) under transient conditions by means of wavefront analysis. After a qualitative analysis to obtain information about the relevant mechanistic scheme the main effort has been concentrated on the dependence of the microkinetics on different oxidation states of the catalyst. The watergas shift reaction in its overall formulation... 

Fiolitakis, E. Hofmann, H. Dependence of the Kinetics of the Low Temperature Watergas Shift Reaction on the Catalyst Oxygen Activity, to be published in Journal of Catalysis... 

Since the gas phase contains five components which should satisfy three elementary mass balances, two arbitrarily chosen, but independent,conversions are required to define its composition, e.g. the total methane conversion, Xqjj, and the conversion of methane into C02, Xco2 The prediction of these conversions in any point of the reactor therefore necessitates two rate equations, each derived under the assumption of at least one rate determining step (r.d.s.). A number of authors have used one rate equation only, thereby assuming the watergas shift reaction (CO+H2O Z C02+H2) to be at equilibrium at any point in the reactor (2, 3, 4), but others have contradicted this assumption (5, 6). From this mechanism and after discrimination between more than 150 rival models (1), the... 

These problems have been studied on Fe304 by Mars (7). It was found that at 300°C the reaction proceeds as to 70-85% in the direction of dehydrogenation, giving a H2/CO ratio which is lower than would have to be expected if the watergas shift reaction had reached equilibrium. Even a long residence time of the gas in the reactor has no effect upon the selectivity, which shows that a secondary reaction does not take place. Moreover it was shown that formic acid completely poisons the conversion of additional CO + H20. Evidently, formic acid is adsorbed very strongly on the surface as a result, the decomposition of formic acid is zero-order. 

Androver, M. E., Lopez, E., Borio, D. O., Pedernera, M. N. (2009). Theoretical study of a membrane reactor for the watergas shift reaction under non-isothermal conditions. American Institute of Chemical Engineers Journal, 55, 3206—3213. 

The transient responses of different reactants are shown in Fig. 31 for the watergas shift reaction performed on a CuO/ZnO-catalyst. In the special case depicted in Fig. 31, the catalyst was pretreated with a H20/H2-mixture having a given p q/Ph =10, leading to a nigh and uniform oxidation level or the whole catalyst packing. After a step change of the inlet concentration... 

Fig. 32 Reaction scheme of the watergas shift reaction according to the wavefront analysis /49, 50/.

Fig. 33 Kinetic parameters for the different reaction steps the watergas shift reaction (see Fig. 32).

Effectiveness factors calculated in this way are of the order of 0.02-0.04 for both reactions. Van Hook (1 9) and Rostrup-Nielsen (20) published values which are of the same order of magnitude, but the latter were obtained assuming first order kinetics for the methane conversion and equilibrium for the watergas shift. The corresponding reaction layer amounts to 0.65-1.3 10 A, and to a surface area still exceeding Sp by a factor IOOO. 

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