Porous Catalyst
The catalyst is a kind of substance that increases the rate of a reaction without itself being consumed. The catalytic process usually consists of following steps:
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Adsorbate transfers across the fluid-adsorbent boundary layer to adsorbent surface;
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Adsorbate is absorbed on the adsorbent surface;
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Chemical reaction of adsorbate on the surface;
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Desorption of reaction products (adsorbate) from the adsorbent surface into the fluid-adsorbent boundary layer;
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Adsorbate transfers from the boundary layer into bulk fluid.
if the resistance in boundary layer is neglected, the five steps above may be reduced to three steps:
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Adsorption on to the adsorbent surface;
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Surface reaction at adsorbent surface;
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Desorption from adsorbent surface.
Use this feature to model a catalytic process where it concerns surface reaction and adsorption. It has four subnodes. Two of them are default: Fluid and Porous Matrix, and other two are selective: Surface Reaction and Adsorption.
reactive specific surface area
Enter a specific surface area for the adsorption and surface reaction processes. The default value is 1·107 1/m.
concentration input
Select a Concentration input — Molar concentration (mol/(m^2)) (the default), Amount per solid mass (mol/kg). This parameter determines the unit for initial values of adsorbed species and user-defined surface species.
adsorbed species
Specify these species which are adsorbate to the catalyst (adsorbent). The concentrations (for example, cads_i for species i) of adsorbed species are defined as dependent variables and solved. The rate of adsorption is defined in Adsorptions subnode. With an adsorbed species being selected, its initial value field is activated. Enter the initial value according to the concentration type which is decided by the selected value from Concentration input.
surface species
There could be extra surface species besides the adsorbed species (coupled to physics interface dependent variables) and their corresponding adsorbed sites on adsorbent surface. These extra surface species (also called user-defined species) could take part in catalytic reactions. The concentrations (for example, csurf_j for species j) of them are solved. The surface reaction rate is defined in the Surface Reaction subnode.
Add a user-defined surface species in the Surface species table by clicking the Add button under the table. The default name is cs<n> (n is a series number). The name can be changed into any valid name.