Hougen-Watson type equation

This Hougen-Watson type equation considers the inhibiting influence of H2O on the reaction rate, whereby the intrinsic reaction rate constant k, h2,hw and the coefficient Khw are given by... 

A higher form of interpretation of the effect of solvents on the rate of heterogeneously catalyzed reactions was represented by the Langmuir-Hinshelwood kinetics (7), in the form published by Hougen and Watson (2), where the effect of the solvent on the reaction course was characterized by the adsorption term in the kinetic equation. In catalytic hydrogenations in the liquid state kinetic equations of the Hougen-Watson type very frequently degrade to equations of pseudo-zero order with respect to the concentration of the substrate (the catalyst surface is saturated with the substrate), so that such an interpretation is not possible. At the same time, of course, also in these cases the solvent may considerably affect the reaction. As is shown below, this influence is very adequately described by relations of the LFER type. 

Langmuir-Hinshelwood/Hougen-Watson Type of Rate Equations. If the global, reversible reaction... 

Several more complex reactions such as the catalytic reforming of heptanes on Pt/Re/alumina were dealt with in terms of sets of rate equations of the Hougen-Watson type by Van Trimpont et al. [1986]. The hydrogenolysis of thiophene and benzothiophene on Co/Mo/alumina was studied along the same lines by Van Parijs et al. [1986a, b] and is also discussed in Examples 2.6.4.A and 2.7.2.2.A. 

Mention should be made of an approach using selectivity relationships rather than concentration versus space-time relationships. The selectivity relationships lend themselves more to anal5dical integration. The method is of fairly general application when the feed consists of a single component and the Hougen-Watson-type rate equations aU have the same denominator. Froment [1975] discussed the application of the method to o-xylene oxidation. 

Peterson [1965a, b] used some of the data of Austin and Walker [1963] to show how the application of a first-order criterion would not be correct. Here, the data are recalculated on the basis of (3.9-7). This reaction appears to be very strongly inhibited by adsorption of the product, carbon monoxide, which leads to large deviations from first-order behavior. The rate equation was of the Hougen-Watson type ... 

Even with an isothermal particle and without including the film, multiplicity is theoretically possible when the rate increases with conversion as may occur for some type of Hougen-Watson rate equations and some particular parameter values. According to Luss, the sufficient condition for uniqueness of the concentration profile in the particle is... 

In general, the use of Langmuir-Hinshelwood-Hougen-Watson (LHHW)-type of rate equation for representing the hydrogenation kinetics of industrial feedstocks is complicated, and there are too many coefficients that are difficult to determine. Therefore, simple power law models have been used by most researchers to fit kinetic data and to obtain kinetic parameters. 

For most gas-solid catalytic reactions, usually a rate equation corresponding to one form or another of the Hougen and Watson type described above can be found to fit the experimental data by a suitable choice of the constants that appear in the adsorption and driving force terms. The following examples have been chosen to illustrate this type of rate equation. However, there are some industrially important reactions for which rate equations of other forms have been found to be more appropriate, of particular importance being ammonia synthesis and sulphur dioxide oxidation 42 . 

If the model is linear in the parameters each point on the surface of this volume, that is, each set of parameter values corresponding to a point on the surface, will lead to the same sum of squares of residuals. The example given in the figure is typical for rate equations of the Hougen and Watson type. The long, narrow... 

Estimation of the kinetic parameters in Langmiiir - Hinshelwood - Hougen -Watson (LHHW) type rate equations, using experimental data sets obtained from a batch and a CSTR reactor. 

Such data are described by an equation of the Langmuir-Hinshelwood-Hougen-Watson (LHHW) type ... 

Langmuir-Hinshelwood-Hougen-Watson (LHHW) Rate Equations (1947) Hougen and Watson analyzed several types of catalytic reactions with different ratedetermining steps (adsorption, surface reaction), different types of adsorption (one or more species, dissociative or molecular adsorption), and different types of reactions (mono- or bimolecular, reversible or irreversible). They derived a general rate equation based on three terms ... 

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