Molecular transport data estimation

This appendix gives a brief description of the computer programs used to estimate thermodynamic, kinetic and molecular transport data, computer programs for the generation, analysis and reduction of reaction mechanisms and computer programs for the simulation of laboratory reactors. 

A pseudo-quantitative application of the theoretical formalism has been made for Nafion. The values for the requisite molecular parameters were estimated from a combination of experimental bulk thermodynamic data and molecular structure calculations using both molecular and quantum mechanics (23,24). A constraint was imposed in the development of the structural formalism. The model was constructed so that the predicted structural information could be used in a computer simulation of ion transport through an ionomer, that is, modeling the ionomer as a permselective membrane. 

The validity of some of the assumptions made in the interpretation of transport data for poly-ionic solutions has been questioned [1, 2]. However, no real quantitative estimate of the errors has as yet been established and the question of which molecular parameters are actually attainable by transport measurements remains to be answered. 

The empirical rules for estimating potential parameters for pure substances are summarized in this section. These rules are stated in the preferred order of application from most reliable to very approximate. If the needed transport or molecular data are not available to use a certain formula, a subsequent rule in the list should be tried. (Methods of estimating parameters for the interactions between two different species i, j, i.e., combining rules, are given in the next section, 12.2.4.)... 

Several laboratories have measured solubilities and/or partition coefficients of solutes in higher molecular weight media, and their data provides a test of this approach to estimating polymer solubilities. Flynn and Yalkowsky (17,18) studied the transport and solubility properties of a series of p-aminobenzoate esters, p-HjNCjH COOR, R = methyl to hexyl, in poly(dimethylsiloxane) fluid (PDMS). We find that their values of log P(PDMS) correlate well with reported (33) values of log P values of the same series of solutes in oleyl alcohol/water, as illustrated by the plot in Figure 8 and the correlation statistics (Equation 17). 

Since the degree of coupling is directly proportional to the product Q (D/k)in, the error level of the predictions of q is mainly related to the reported error levels of Q values. The polynomial fits to the thermal conductivity, mass diifusivity, and heat of transport for the alkanes in chloroform and in carbon tetrachloride are given in Tables C1-C6 in Appendix C. The thermal conductivity for the hexane-carbon tetrachloride mixture has been predicted by the local composition model NRTL. The various activity coefficient models with the data given in DECHEMA series may be used to estimate the thermodynamic factors. However, it should be noted that the thermodynamic factors obtained from various molecular models as well as from two sets of parameters of the same model might be different. 

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