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Simple analytical equations of state have been derived for a mixture of heterochain molecules differing among themselves in both the chain length and primary structure. A model for a polymer chain has been constructed as a sequence of freely jointed tangent hard spheres, whose diameters are not necessarily identical. The statistical mechanical methods previously reported in the literature, namely, a polymeric analog of the Percus-Yevick approximation and the first-order thermodynamic perturbation theory (TPT) of polymerization, have been generalized. According to either of those approaches, the equation of state and residual thermodynamic potentials for the chain fluid are the sum of two terms of which one characterizw a system of disconnected monomers and the other one reflects the effect of monomer bonding in the chain. The specificity of the theories in question shows up in the representation of a second (bonding) term. The quantitative discrepancy in the predictive power of these theories tends to diminish with decreasing packing fraction of the system. As has been found, a version of perturbative theory recently developed by Freed for a homopolymer liquid and the TPT of polymerization lead to essentially the same result in their respective low-order approximations. The general results obtained have been exemplified by a binary copolymer-insolvent system. The copolymer primary structure has been accounted for in the thermodynamic formulas through a weight-average fraction of available chain unit diads, and the chain-length distribution, through anumber-average degree of polymerization. Given the packing fraction, the only necessary molecular parameter in the derived expressions is the ratio of hard-sphere diameters for monomer units and the solvent molecules.

In this study, the gas-liquid membrane contactor was considered for regeneration of the roomtemperature ionic liquids (RTIL) that can be used as physical solvents for carbon dioxide capture process at elevated pressures. Poly[1-(trimethylsilyl)-1-propyne] (PTMSP) was selected as a membrane material due to its high mass transport characteristics and good mechanical properties. Nine different RTILs, such asand [P66614][Phos], were used to evaluate the solvent-membrane compatibility. The long-term sorption tests (40+ days) revealed that the solvent-membrane interaction is mainly determined by the liquid surface tension regardless of viscosity and molecular size of RTILs. For instance, [Emim][BF4] and [Emim][DCA], having the surface tension of 60.3 and 54.0 mN/m, demonstrated a very low affinity to the bulk material of PTMSP (sorption as low as 0.02 g/g; no swelling); while for the next ionic liquid [Bmim][BF4] with surface tension of 44.4 mN/m, the sorption and swelling of PTMSP was 0.79 g/g and 21%, respectively. The long-term RTIL permeation test (p=40 bar, T=50°С, t>400 hours) confirmed that there is no hydrodynamic flow through PTMSP for [Emim][DCA] and [Emim][BF4]. The concept of CO2 stripping from RTIL with the membrane contactor by the pressure (p=40 bar) and temperature (T=20°С) swing was proofed by using PTMSP membrane and [Emim][BF4]. The overall mass transfer coefficient value was equal to(1.6-3.8)•10 -3 cm/s with respect to liquid flow rate. By using the resistance-in-series model, it was shown that the membrane resistance contribution to the gas transfer was estimated to be approximately 8%.

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A recently developed dynamic desorption technique is used for obtaining vapor isotherms on porous materials. This gravimetric technique does not require any preliminary calibration and is based on analyzing the kinetics of liquid evaporation from a porous sample under quasi-steady state conditions. The crucial feature of the technique is concerned with the fact that no vapor pressure measurements are necessary. The technique is illustrated by desorption of benzene vapors from mesoporous silica MCM-41. To calculate the pore size distribution, the Derjaguin-Broekhoffde Boer theory in its combination with the Wheeler model for capillary condensation is used. In the calculations, the reference data on benzene adsorption on a nonporous silica gel from two different sources (published by different authors) are applied. The mean mesopore sizes estimated from desorption isotherms are shown to be in a fair agreement with the calculations through the geometrical method based on the X-ray diffraction data. The dynamic desorption technique can serve as an additional tool for the characterization of a porous media.

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