UNIFAC
Documentation
DDBSP Dortmund Data Bank Software Package
DDBST Dortmund Data Bank Software & Separation Technology GmbH
Marie-Curie-Strae 10
D-26129 Oldenburg
Tel.: +49 441 361819 0
Fax: +49 441 361819 10
E-Mail: support@ddbst.com
Web: www.ddbst.com
DDBSP- Dortmund Data Bank Software Package
2014
Table of Contents
Introduction........................................................................................................................................3
Tutorial...............................................................................................................................................3
Building a System.........................................................................................................................4
Checking Parameter Availability...................................................................................................6
Calculation.....................................................................................................................................9
Isothermal Calculation over a Concentration Range................................................................9
Calculation at Constant Compositions over a Temperature Range.........................................11
Result Grid.......................................................................................................................................11
Activity Coefficient Diagram...........................................................................................................12
The Menus........................................................................................................................................12
Appendix..........................................................................................................................................13
UNIFAC......................................................................................................................................13
Table of Figures
Figure 1: UNIFAC Graphical User Interface..........................................................................................4
Figure 2: Component Selection..............................................................................................................5
Figure 3: Component List.......................................................................................................................5
Figure 4: Group Assignment Details......................................................................................................6
Figure 5: Parameter Availability.............................................................................................................7
Figure 6: Calculation Settings.................................................................................................................9
Figure 7: Calculation at Constant Temperature......................................................................................9
Figure 8: Composition Settings............................................................................................................10
Figure 9: Special Compositions............................................................................................................10
Figure 10: Calculation Setting for Constant Compositions..................................................................11
Figure 11: Result Grid...........................................................................................................................11
Figure 12: Result Grid with LLE Calculation.......................................................................................11
Figure 13: Temperature-dependent Activity Coefficients.....................................................................12
UNIFAC
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Introduction
This software allows calculating activity coefficients, heats of mixing, and excess heat capacity by
the activity coefficient models UNIFAC1 and modified UNIFAC (Dortmund)2 for mixtures with up to
fifty components.
If the LLE extension license is available it is also possible to calculate the liquid-liquid equilibrium
for binary and ternary systems.
The software is an integral part of the Dortmund Data Bank software package and uses the
component, the groups assignment, and other tools from this package. The package therefore
includes
1. the main calculation program (described here)
2. a component selection tool (described in ComponentManagement.pdf)
3. a component editing tool (described in ComponentManagement.pdf)
4. a UNIFAC interaction parameter editor (described in GC Model Parameters.pdf)
5. a DDB configuration editing tool (described in DDBConfiguration.pdf)
The software comes with a list of more than 37000 components from the main DDB component list and
approx. 18800 of them have a UNIFAC group assignment and about 20000 have a group assignment for
modified UNIFAC (Dortmund). For most components the DDB provides CAS registry numbers (24250),
empirical formula molecular weights (almost all). All other components are applicable in both methods (e. g.
salts, metals and metal complexes, etc.).
The latest UNIFAC parameters have been published in 20033, the latest parameter for mod. UNIFAC
(Dortmund) have been published 20024, 20065 and 2011 (ionic liquids)6.
Most current parameters can be obtained from the UNIFAC Consortium.
Tutorial
This tutorial shows all functions inside the main calculation software. Additional PDFs are available
for editing, adding, and searching components, as well as for modifying/understanding the DDB
configuration, and the interaction parameter editor.
1 Fredenslund A., Jones R.L., Prausnitz J.M., Group-Contribution Estimation of Activity Coefficients in Nonideal
Liquid Mixtures, AIChE J., 21(6), 1086-1099, 1975
2 Weidlich U., Gmehling J., A Modified UNIFAC Model. 1. Prediction of VLE, hE, and , Ind. Eng. Chem. Res.,
26(7), 1372-1381, 1987
3 Wittig R., Lohmann J., Gmehling J., Vapor-Liquid Equilibria by UNIFAC Group Contribution. 6. Revision and
Extension, Ind. Eng. Chem. Res., 42(1), 183-188, 2003
4 Gmehling J., Wittig R., Lohmann J., Joh R., A Modified UNIFAC (Dortmund) Model. 4. Revision and Extension,
Ind. Eng. Chem. Res., 41(6), 1678-1688, 2002
5 Jakob A., Grensemann H., Lohmann J., Gmehling J., Further Development of Modified UNIFAC (Dortmund):
Revision and Extension 5, Ind. Eng. Chem. Res., 45(23), 7924-7933, 2006
6 Nebig S., Gmehling J., Prediction of phase equilibria and excess properties for systems with ionic liquids using
modified UNIFAC: Typical results and present status of the modified UNIFAC matrix for ionic liquids, Fluid Phase
Equilib., 302(1-2), 220-225, 2011
UNIFAC
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Building a System
System
(List of
Components)
Add
Components
Figure 1: UNIFAC Graphical User Interface
A system contains of several pure components. Component can be added by the Add Component
button. The calls the standard DDB component selection package which is described in details in a
separate PDF (Component Management, Chapter 9).
The dialog allows searching for names, formulas, CAS registry numbers, and many more criteria.
UNIFAC
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Search
Component
List
Figure 2: Component Selection
The component list shown is the complete list of components available in the Dortmund Data Bank.
It includes also many components for which no group assignments are available.
After a component has been selected (by a double-click or by
the component is added to the component list.
Group
Assignments
Figure 3: Component List
Missing
Group
Assignment
This list displays the DDB internal number, an English name, the empirical formula, the molecular
weight, and both the group assignments for UNIFAC and modified UNIFAC (Dortmund). If a group
assignment is not given a n.a. is written.
Single components can be removed by double-clicking the line, the
complete list can be cleared by clicking the Remove All button.
The system table has a context menu which allows
1. Remove all components
UNIFAC
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2. Remove the selected component
3. Copying, printing, and saving the component list
4. Auto-size the columns of the table
5. Display details of the group assignment
Figure 4: Group Assignment Details
The normal display in the component list only displays the sub groups of the components and this
dialog adds information about the main groups.
Checking Parameter Availability
UNIFAC needs the component specific group assignment and interaction parameters between all
main groups present in the current mixture.
The dialog has two pages:
1. The first page only displays if all parameters are available
UNIFAC
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Figure 5: Parameter Availability
2. The second page gives details about the group assignment for all components and all main
group interactions. The example shows that for the given system UNIFAC can be used but
modified UNIFAC (Dortmund) will fail because of a missing interaction parameter.
UNIFAC
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UNIFAC
Component
Component
Component
Component
11: Ethanol
Subgroups:
1
12: Diethyl ether
Subgroups:
1
17: Aniline
Subgroups:
9
15: Formic acid
Subgroups:
43
List of Main Groups
Maingroups:
1 (CH2
(COOH
)
(CH3
2 (CH2
14 (OH
(CH3
2 (CH2
25 (OCH2
(ACH
(HCOOH
3 (ACH
36 (ACNH2
5 (OH
13 (CH2O
17 (ACNH2
20
Interaction parameters
1 3: 1 parameter/s
1 5: 1 parameter/s
1 - 13: 1 parameter/s
1 - 17: 1 parameter/s
1 - 20: 1 parameter/s
3 5: 1 parameter/s
3 - 13: 1 parameter/s
3 - 17: 1 parameter/s
3 - 20: 1 parameter/s
5 - 13: 1 parameter/s
5 - 17: 1 parameter/s
5 - 20: 1 parameter/s
13 - 17: 1 parameter/s
13 - 20: 1 parameter/s
17 - 20: 1 parameter/s
System has all parameters available.
mod. UNIFAC (Dortmund)
Component
Component
Component
Component
11: Ethanol
Subgroups:
1
12: Diethyl ether
Subgroups:
2
17: Aniline
Subgroups:
9
15: Formic acid
Subgroups:
43
List of Main Groups
Maingroups:
1 (CH2)
3 (ACH)
(CH3
2 (CH2
14 (OH (P)
(CH2
1 (CH3
25 (OCH2
(ACH
(HCOOH
5 (OH)
36 (ACNH2
13 (CH2O)
17 (ACNH2)
44 (HCOOH)
Interaction parameters
1 3: 2 parameter/s
1 5: 3 parameter/s
1 - 13: 2 parameter/s
1 - 17: 3 parameter/s
1 - 44: 1 parameter/s
3 5: 3 parameter/s
UNIFAC
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3
3
3
5
5
5
13
13
17
13:
17:
44:
13:
17:
44:
17:
44:
44:
2
3
3
3
3
0
2
1
0
2014
parameter/s
parameter/s
parameter/s
parameter/s
parameter/s
parameter/s
parameter/s
parameter/s
parameter/s
Parameters are missing.
Calculation
Figure 6: Calculation Settings
Isothermal Calculation over a Concentration Range
For a constant temperature it is possible to
enter compositions manually or let the
program calculate some auto-distributed
composition points.
Figure 7: Calculation at Constant Temperature
UNIFAC
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The Set Compositions button opens a
dialog where compositions can be created
(Create Data Points). In this dialog it is
possible to enter compositions directly in
the data grid and it allows creating data
points over a composition range.
Special case like constant compositions or
composition ratios for single or few
components are also supported. The
composition grid can be copied to the
Windows clipboard as well as data can be
pasted from the clipboard. This allows
creating and managing compositions
outside this program (maybe in Microsoft
Excel or OpenOffice Calc).
Compositions can also be saved to and
restored (Open) from files.
Data Grid
The number of possible data points is
limited to 10001.
Figure 8: Composition Settings
Special compositions can be constant compositions for single components or special composition
ratios (specified by integer values like 4 and 5 four a 4/5 ratio) for a list of components.
Figure 9: Special Compositions
UNIFAC
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Calculation at Constant Compositions over a Temperature Range
Figure 10: Calculation Setting for Constant Compositions
This calculation type allows the specification of a single composition line and a temperature range. The
composition can be entered as mole fractions and as weight fractions.
Result Grid
Figure 11: Result Grid
The result grid shows all given compositions and the wanted temperatures first followed by the
calculated activity coefficients, the heat of mixing and the excess heat capacity.
Figure 12: Result Grid with LLE Calculation
If the LLE calculation is active the initial concentrations are treated as feed. The result grid will then
be extended by two phase columns for each component and two activity coefficient/hE/cpE columns
for the second phase. The additional columns will be present even if no LLE was found.
The table can be saved as Microsoft Excel (xls) file (
clipboard (
UNIFAC
) or copied to the Windows
).
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Activity Coefficient Diagram
In case of the calculation at a fixed single composition at different temperatures a diagram with the
temperature-dependent activity coefficients is displayed.
Figure 13: Temperature-dependent Activity Coefficients
The Menus
Component lists are files
containing raw data set
numbers. These file have the
extension stl.
The system grid (component
list) can be copied and printed.
Show Hints activates
additional hints for many items
on the form.
Components starts the
Component Editor (described in Interaction Parameter Matrix
The system grid can also be
ComponentManagement.pdf) starts the parameter editor
saved as a comma separated file
(described in GC Model
which can be loaded in spread
Parameters.pdf)
UNIFAC
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sheet programs.
DDB Configuration starts the
configuration program
(described in
DDBConfiguration.pdf)
Appendix
UNIFAC
The UNIFAC group contribution model7 has been developed to estimate the real vapor-liquid
equilibrium behavior. In a group contribution model the mixture is not seen as a mixture of
components but as a mixture of groups. The large advantage is that the number of structural groups is
much smaller (dozens) than the number of components (millions). This means that it is possible to
calculate most systems of commercial interest with very few group information.
UNIFAC is based on the UNIQUAC equation. Therefore activity coefficients are calculated from two
terms,
ln ln iC ln iR .
The combinatorial part is calculated in the same manner as in UNIQUAC,
V
V
ln iC 1 Vi ln Vi 5qi 1 i ln i
Fi
Fi
with
Vi
ri
rj x j
j
and
Fi
qi
qjxj .
j
For the calculation of the combinatorial part only the relative van der Waals volume ri and surface qi
together with the mole fractions xi are needed.
The van der Waals volume and surface can be calculated from group volumes and surfaces,
ri k(i ) Rk
k
qi k(i ) Qk
7 Gmehling J.,Kolbe B., Thermodynamik, Verlag Chemie, Weinheim (1987)
UNIFAC
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(i )
with k as the number of structural groups of type k in the molecule i .
The residual part has to be calculated from the group activity coefficients k ,
ln iR k(i ) ln k ln k(i ) .
The concentration dependency of the group activity coefficients in the mixture k (and in the pure
(i )
component k ) must be calculated in analogy to the UNIQUAC equation,
m m
ln k Qk 1 ln m m
.
m
m n n
n
The surface contribution m and the mole fraction X m of the group is defined by
m
Qm X m
Qn X n
n
Xm
m
j
xj
n, j
xj
and the parameter nm is defined as
nm e
anm
T
with a nm as group interaction parameters between the groups n and m .
Modified UNIFAC (Dortmund) uses temperature-dependent interaction parameters:
nm e
UNIFAC
anm bnm T cnm T 2
T
T
T
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