Pure Component Properties
Pure component properties are of great importance in all fields of chemical engineering for the design of chemical processes and other applications like environmental protection, workplace safety, etc.. In addition they form the basis for the description of mixture properties. Since the experimental determination of pure component properties is usually time consuming, rather expensive or not possible due to e.g. chemical reactions, estimation methods are of great importance.
Due to the limited scope of existing data bases for pure component properties and the often poor knowledge about the applicability of estimation methods, work on pure component properties was started in 1992 at the University of Oldenburg.
The main aims of the project were:
- Collection of pure component properties also including Russian, East - Asian etc. references.
- Correlation of recommended values and model parameters for the description of pure component properties.
- Development of a program package for the graphical input, storage and automatic fragmentation of molecular structures on the basis of the different fragmentation rules (Joback, Benson, ...)
- Extensive test of existing estimation methods and development of methods for the estimation of probable errors of these methods.
- Development of new estimation methods on the basis of a very large set of critically evaluated data. These methods should also employ parameters from molecular modeling (size, shape, charge distribution, internal tension, hydrophilicity / hydrophobicity).
With the help of these data and programs, the solution of numerous interesting problems becomes readily available, for example the development of a program for the generation of substances with given physical properties (computer aided molecular design). Altogether the manpower of approx. 20 scientists and numerous co-workers in Oldenburg, Berlin, Prague, Tallinn and Minsk was financed by the project. The results of the project shall is used for various purposes. These include:
- Publication in form of data handbooks or as online or inhouse versions of the electronic data bank.
- Publication of the data and methods on CD-ROM using a hypertext user interface.
- Development of correlations and estimation methods for pure component properties using information from molecular modelling.
- Generation of components with specific physical properties (computer aided molecular design) for process synthesis.
Since the end of the project, the data bank is continuously updated by DDBST GmbH and FIZ Chemie GmbH. It is of great importance to include the latest available information on new components. It can be observed that due to the development in experimental techniques the reported values for some properties can change significantly with the year of publication. A nice example is given in the following figure (D. Zudkevitch, private communication)
Estimation of pure component properties to a great extend is based on the knowledge of the molecular structure. Most estimation methods employ the group contribution approach, each using a different definition of the basic structural groups. More elaborated methods make use of correction terms based on the neighborhood of a structural group in a molecule. This makes it difficult for an unexperienced user to estimate physical properties. Some modern group contribution methods (e.g. Joback) try to solve this problem by using only a limited number of rather simple structural groups. For the Pure Component Data Project a different approach was employed. A graphical editor (ARTIST) for molecular structures was developed and more than 17000 structures were stored in a data bank in form of connection tables.
With the help of a special program (AutoInkr) these structures can be fragmented following the rules of a large number of different group contribution methods. The graphical editor (ARTIST, see figure above) serves as a user interface to the structure data base, the automatic fragmentation of molecules and different group contribution methods.
We would like to thank BMBF, FIZ Chemie GmbH and DDBST GmbH for financial support.
- Institute of Chemical Technology, Prague (Prof. Dr. J. Matous)
- FIZ Chemie GmbH, Berlin (Dr. R. Deplanque; Dr. H.-J. Scharnow)
- Institute of Chemistry, Tallinn (Prof. Dr. E. Siimer)
- Byelorussian University of Technology, Minsk (Prof. Dr. I. Shulgin)
- Institute of Chemical Engineering, Graz (Priv. Doz. H . Huemer)
- DDBST GmbH, Oldenburg