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Non-porous catalysts

I. Dense (non-porous) catalyst electrode film hindering ion spillover. [Pg.538]

Using 324 measuring points taken at temperatures between 35 and 75 °C, hydrogen concentrations between 1.6 10-3 and 11.0 10-3 mol NdnT3 and oxygen concentrations between 1.7 10 3 and 7.3 10 3 mol Ndm-3, a kinetic expression for the reaction was determined on the basis of a Langmuir-Hinshelwood model (Figure 2.30). The Mears criterion was applied to verify that no mass transfer limitation was to be expected for the system from the gas phase to the non-porous catalyst ... [Pg.322]

Here, we look at the conversion of a gaseous component A on a non-porous catalyst under isothermal conditions. In the steady-state, the volume-related rates of the gas-side mass transfer and the surface reaction are equal to each other ... [Pg.184]

Elnashaie, S.S.E.H. and Elmuhanna, S., Effect of Diffusional Resistance on the Rates of o-Xylene Partial Oxidation over VjOs Non-Porous Catalyst Pellets. Studies in Surface Science and Catalysis, Vol. 73, Progress in Catalysis, Proceedings of the 12th Canadian Sympo-... [Pg.12]

The equations of the adiabatic case also represent the case of non-porous catalyst pellets with external mass and heat transfer resistances and negligible intraparticle heat transfer resistance but with different meaning to the parameters. [Pg.73]

Equations 4.4-4.6 can be solved simultaneously for a certain set of parameters in order to obtain the values of X, Xg, y (the concentrations and temperature at the exit of the reactor for the CSTR case and the surface of the catalyst pellet for the non-porous catalyst pellet case). However, it is possible to reduce equations 4.4-4.6 to a single non-linear equation in y together with two explicit linear equations for the computation of X, Xg once y has been determined. The single non-linear equation can be written as ... [Pg.73]

The Non-isotherinal Catalyst Pellets with Linear Kinetics (Non-porous Catalyst Pellet with Unimolecular Reaction)... [Pg.87]

FIGURE 5.3 Schematic representation of a single non-isothermal non-porous catalyst pellet. [Pg.87]

Various simplified models can be used with varying degrees of accuracy for the simulation of the transient behaviour of non-porous catalyst pellets. The most suitable unsteady state model for this problem is that with infinite thermal conductivity. This simplified model is quite accurate for metal and metal oxide catalysts. In this model, equation (5.45) disappears and the model becomes strictly lumped parameter described only by ordinary initial value differential equations. [Pg.92]

Network on Non-porous Catalyst Pellets. The Steady State Analysis for the Catalytic Partial Oxidation of... [Pg.94]

In this section, the steady state models for an actual reaction taking place on the surface of the non-porous catalyst pellets are formulated, solved and some simulation results presented. This serves as a simple illustration for the use of the forgoing information for the analysis of a real catalytic reaction system. The following simplifying assumptions are used in the derivation of the model equations for the catalyst pellets ... [Pg.94]

The mathematical models for the partial oxidation of o-Xylene to phthalic anhydride on non-porous catalyst pellets for two different kinetic models... [Pg.94]

Chapter 3 dealt with the problem of the reaction kinetics for different gas-solid reactions, while chapter 5 dealt with the mass and heat transfer problems for porous as well as non-porous catalyst pellets. In chapter 5 different degrees of complexities and rigor were used. In chapter 5, the analysis started with the simplest case of non-porous catalyst pellets where the only mass and heat transfer Coefficients are those at the external surface which depend mainly on the flow conditions around the catalyst pellet and the properties of the reaction mixture. It was shown clearly that j-factor correlations are adequate for the estimation of the external mass and heat transfer coefficients (k, h) associated with these resistances. For the porous catalyst pellets different models with different degrees of rigor have been used, starting from the simplest case of Fickian diffusion with constant diffusivity, to the rigorous dusty gas model based on the Stefan-Maxwell equations for multicomp>onent diffusion. [Pg.144]

Non-porous catalyst pellet 141, 145, 153-192, 379-397 Number, Nusselt 213-219, 421 Peclet 16 Prandtl 299... [Pg.253]

Results and Discussion of the Steady State for Non-isothermal, Non-porous Catalyst Pellet for a Single Unimolecular Irreversible Reaction... [Pg.256]

Chapter 5 is dedicated to the single particle problem, the main building block of the overall reactor model. Both porous and non-porous catalyst pellets are considered. The modelling of diffusion and chemical reaction in porous catalyst pellets is treated using two degrees of model sophistication, namely the approximate Fickian type description of the diffusion process and the more rigorous formulation based on the Stefan-Maxwell equations for diffusion in multicomponent systems. [Pg.267]

For non-porous catalyst pellets the reactants are chemisorbed on their external surface. However, for porous pellets the main surface area is distributed inside the pores of the catalyst pellets and the reactant molecules diffuse through these pores in order to reach the internal surface of these pellets. This process is usually called intraparticle diffusion of reactant molecules. The molecules are then chemisorbed on the internal surface of the catalyst pellets. The diffusion through the pores is usually described by Fickian diffusion models together with effective diffusivities that include porosity and tortuosity. Tortuosity accounts for the complex porous structure of the pellet. A more rigorous formulation for multicomponent systems is through the use of Stefan-Maxwell equations for multicomponent diffusion. Chemisorption is described through the net rate of adsorption (reaction with active sites) and desorption. Equilibrium adsorption isotherms are usually used to relate the gas phase concentrations to the solid surface concentrations. [Pg.272]

First, consideration is given to the simplest case that takes into account external mass and heat transfer resistances only. This situation is rigorous for non-porous catalyst pellets and approximate for porous catalyst pellets whenever the intraparticle resistances are much smaller than the external resistances. [Pg.335]

For the simple linear kinetics of the isothermal non-porous catalyst pellet described by equations (5.3, 5.4), the effectiveness factor is simply given by ... [Pg.338]

By lowering the absolute reaction rate (e.g., low temperature) or by reducing the diffusion resistance (non-porous catalyst), the negative influence of mass transfer on the A/F window width can be counterbalanced. For the system studied here it has to be concluded that only a compromise between A/F window width in the lean range and absolute reaction rate can be attained. [Pg.171]

We now compare the performance of non-porous catalysts with the selectivity expected for porous catalysts in Type III reactions. Referring to the Type III reaction scheme given above, we note that if ki and ki are the intrinsic rate constants per unit internal surface, then on a plane surface the yield of B for first order kinetics would be determined by the equations ... [Pg.317]

Transport phenomena often accompany processes conducted in reactors with a catalyst bed. Included are internal and external diffusion, and internal and external energy transfer. Chemical reactions taking place on the surface of non-porous catalyst grains usually meet a resistance in a form of an external mass or energy transfer, whereas the internal mass transfer and an external energy transfer most often accompany non-isodiermal processes in porous grains. [Pg.411]

Non-porous catalysts are monolithic catalysts. These are used in processes where heat removal is a major consideration because extra catalyst surface can enhance the reaction rate and heat removal can become severe. An example of a non-porous catalyst is platinum gauze used in ammonia oxidation in the nitric acid process. [Pg.81]

Combination of Eqs. (4.5.13) and (4.5.14) leads to the effective reaction rate for a porous particie (the rare case of an non-porous catalyst is inspected below) ... [Pg.236]

For the rare case of a non-porous catalyst - for example, a metal wire gauze used for NH3 oxidation (Section 6.4) - similar equations are valid. The rate of the chemical reaction is given by ... [Pg.236]

For a packed bed of spheres, the minimum value of the Sherwood number for reactant A (Sh = pdp/DA, of 3.8 (for Rep—>0) can be used (Section 3.2.2.2). Thus we can estimate the minimum values of for porous and non-porous catalysts (first-order reaction). For porous particles we obtain based on Eq. (4.5.17) ... [Pg.237]


See other pages where Non-porous catalysts is mentioned: [Pg.2121]    [Pg.266]    [Pg.426]    [Pg.1878]    [Pg.12]    [Pg.71]    [Pg.101]    [Pg.256]    [Pg.323]    [Pg.335]    [Pg.341]    [Pg.361]    [Pg.482]    [Pg.163]    [Pg.163]    [Pg.2125]    [Pg.26]    [Pg.244]   
See also in sourсe #XX -- [ Pg.2 ]




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