Pseudo-Compounds

The pseudo-compounds node allows you to add and modify the artificial compounds. You may find this useful when the reaction rates cannot be expressed as a function of the actual compounds by using the Mass Action or LHHW kinetics.
Generally, pseudo-compounds are calculated in terms of linear or nonlinear relationships of other compound concentrations and/or previously defined pseudo-compounds. A good way to understand pseudo-compounds is to see the example. Another special type of pseudo-compounds may be calculated by interpolating values entered by the user as measurements.
For efficiency reasons, it is preferable to define only those artificial compounds that affect the reaction kinetics as pseudo-compounds. Variables which do not affect the reaction, should be entered in the Derived Quantities node.
When estimating, the experimental data for pseudo-compounds can be reconciled similar to the regular compounds, as long as the pseudocompounds are not specified directly as data. To understand more about how pseudo-compounds are calculated at the experimental points, please view the information provided in Note1.

Grid Views

Pseudo-Compounds

Pseudo-Compound terms

Pseudo-Compounds

You may enter the name, abbreviation, defining equation type, and a constant term for the pseudo-compounds. It is organized in columns as follows:

The Pseudo-Compound column is used to enter the pseudo-compound name. It can be renamed by editing this field.
The Type column is to select the type of equation that defines the pseudo-compound.
Two options are available, and the general expression for each of them are:
- Linear Sum:
- Nonlinear Product:
Where Constant and coeff_i and exp_i are numerical values entered by the user that represent the Constant Term, Coefficients and Exponents respectively, while C_i are the concentrations in the reaction phase for the selected compounds in each term. Please be aware that the concentration for the compounds are selected to be either Molarity or Partial Pressure in the Units Configuration node.
The default value is Linear Sum.
The Constant Term column is to enter the constant for both definition types, Linear Sum and Nonlinear Product.
The Expression column (Read-Only) displays pseudocompounds formula.
The Conserved column allows you to specify the pseudo-compounds that will satisfy mass balance constraints. The default specification is not conserved.
A pseudocompound may be selected as conserved if it is defined by a Linear Sum in the Type column, and with a zero value for the constant term. Otherwise a message will appear in the Solver → CheckModel view.
You should select a pseudo-compound as conserved if you intend to calculate its conversion and/or it will be involved in a yield calculation in the Yields Calculations node for either Estimation or Optimization modes. Only conserved pseudo-compounds are available for yield calculations. Furthermore, the calculation of the pseudo-compounds at experimental data points differs depending on this choice as discussed in Note1.
The Units column (Optional) is a text field (maximum 50 characters) used to define units for each PseudoCompounds. The user defined units assigned here are shown in other nodes where the pseudocompounds are displayed.
The Notes column (Optional) is a text field (maximum 100 characters) used to store comments about the pseudo-compounds.

Adding a Pseudo-Compound

You can add a pseudo-compound by entering the name of the pseudo-compound in the last row. The row will change to edit mode, and you may save this new pseudo-compound with the <ENTER> key or clicking on the pencil icon in the row header. Deleting a Pseudo-Compound

There are two ways to delete pseudo-compounds:

Select the pseudo-compound row and use the <DELETE> key.
Execute the Delete action

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Pseudo-Compound terms

In this grid, the terms that are used to define each pseudo-compound are entered. It is organized in columns as follows:

The Compound column, that is used to select a compound or a previously defined pseudo-compound. The concentration (molarity or partial pressure) of the chosen compound is considered for the pseudo-compound definition. When dealing with a Multiphase reactor, the concentration in the reaction phase is the one to be taken into account for the calculations. You may enter up to ten(10) compounds/pseudo-compounds when defining a pseudo-compound.
For each term, the Coefficient/Exponent column is used to enter the coefficient (in the case when the pseudo-compound is defined by a Linear Sum type equation), or the exponent (when the Nonlinear Product Type is selected).

Pseudo-Compounds »