Excess properties of binary mixtures of n-alkanes have been evaluated from perturbation theory. A good equation of state for the reference system mixture is combined with a simple approximation to the perturbation term and with a reasonable set of potential parameters to yield a qualitatively correct description of the trends of excess volumes and excess Gibbs energies of n-alkane mixtures without the need for any adjustable parameter. Moreover, the theory can be made quantitative by introducing two adjustable parameters for each temperature. These two parameters have a clear molecular origin and they could be removed if some of the approximations of the theory proposed here were replaced by a more rigorous evaluation. In this sense this paper is just a first step toward a fully molecular theory of excess properties of alkanes. Excess properties estimated from perturbation theory by using these two adjustable parameters are in excellent agreement with experiment and are clearly superior to those obtained from the classic FOV theory proposed by Flory, Orwoll and Vrij [J. Am. Chem. Soc. 86, 3507, 3515 (1964)]. It is our view that the theory of this work is also conceptually superior to the FOV theory, since it rests on a more rigorous molecular basis.

In this work we analyze the feasibility of using numerical inversion techniques for recovering MWD of actual polymers from a transformed domain, specifically the one defined by probability generating functions. We start from known experimental MWDs, transform them, and then apply two different numerical techniques to recover the MWD. We analyze the influence of noise in the calculated probability generating functions on the quality of the recovered molecular weight distributions. We also study how the range of molecular weight selected for the inversion procedure affects the results. We compare the recovered distributions obtained by both methods and suggest a criterion for establishing the reliability of a given solution. We find that this general strategy is appropriate for the recovery of MWDs whether they are monomodal, multimodal, wide or narrow. This provides a tool for the treatment of actual polymerization systems for which there is no analytical solution for the mass balance equations.

We have incorporated mass balances of monomer, radical and polymer species to a previously developed mixing model for high pressure autoclave polymerization reactors. The customary quasi steady state approximation is not used, and the method of moments is used to simplify the mass balance calculations. The resulting moment model is able to calculate conversions, average molecular weights, long chain branching and melt flow indexes at any point in the reactor. It may also calculate concentration and temperature profiles along the reactor. Results for two base cases are presented in detail. Model predictions were compared with experimental data obtained at the industrial reactor; excellent agreement was obtained. The moment balance equations are presented in a modular way so that they may be easily adapted to be used with any other mixing model for this type of reactor. A m F e m h d e z fflddle L wall cells shaft cells Moment ModelFWk-l J.FZk

The critical properties of binary mixtures of linear and branched alkanes have been evaluated using perturbation theory. An accurate equation of state for the reference system is combined with a mean field treatment of the perturbation term, along with a reasonable potential model. No adjustable parameters were used either for the pure compounds or for the binary mixtures. The aim of this work is to show which features of the critical properties of alkane mixtures can be obtained from a fully molecular based theory. It is shown that the main trends of the critical properties of alkane binary mixtures can be described qualitatively by the theory.

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