We present complementary molecular simulations and experimental results of phase equilibria for carbon dioxide expanded acetonitrile, methanol, ethanol, acetone, acetic acid, toluene, and 1-octene. The volume expansion measurements were done using a high-pressure Jerguson view cell. Molecular simulations were performed using the Gibbs ensemble Monte Carlo method. Calculations in the canonical ensemble (NVT) were performed to determine the coexistence curve of the pure solvent systems. Binary mixtures were simulated in the isobaric-isothermal distribution (NPT). Predictions of vapor-liquid equilibria of the pure components agree well with experimental data. The simulations accurately reproduced experimental data on saturated liquid and vapor densities for carbon dioxide, methanol, ethanol, acetone, acetic acid, toluene, and 1-octene. In all carbon dioxide expanded liquids (CXL's) studied, the molecular simulation results for the volume expansion of these binary mixtures were found to be as good as, and in many cases superior to, predictions based on the Peng-Robinson equation of state, demonstrating the utility of molecular simulation in the prediction of CXL phase equilibria.
Summary: A mathematical model of the acid catalyzed 1,3‐propanediol polymerization has been developed. Two catalysts investigated include sulfuric acid and superacid (tetrafluoroethane sulfonic acid or triflic acid). Based on a detailed reaction mechanism, population and mass balance equations have been derived for small molecules as well as for polymeric species of numerous chain distributions, which are distinguishable in terms of protonation state and end group functionality. Due to the interaction of the sulfuric acid catalyst with the polymer ends, a novel, dual index polymer chain distribution was derived and implemented.The model has been validated with various sets of experimental data obtained in a lab‐scale reactor setup. Dynamic model outputs such as monomer concentration, molecular weight averages, unsaturated and sulfate end groups, water evaporation rate and sulfate middle groups have been compared with experimental data of sulfuric and super acid catalyzed polymerization runs. Very good agreement between model predictions and experimental data has been obtained for both catalyst systems over an extended range of conditions using the same set of model parameter values. It is worth noting that the model is also capable of predicting polymerization equilibrium.
Typically, the oxidation of organic substrates with H 2 O 2 and water-soluble catalysts involves biphasic systems in which the substrate resides in an organic phase and the reaction occurs in the aqueous phase. We demonstrate how the miscible region (in P-T-x space) for water/solvent/ CO 2 ternary systems can be exploited to overcome interphase mass-transfer limitations of such biphasic systems and perform homogeneous oxidations of organic substrates using water-soluble catalysts and oxidants. By employing CO 2 -expanded CH 3 CN/H 2 O 2 /H 2 O mixtures, a variety of olefins (cyclohexene, styrene, 1-methylcyclohexene, 4-methylcyclohexene) were oxidized homogeneously with high (>85%) epoxidation selectivities. An order-of-magnitude enhancement in epoxidation rates was achieved with the addition of pyridine to the homogeneous system, at pressures that are an order of magnitude lower than those needed in the biphasic system described in the literature. Plausible reaction pathways that involve the formation of peroxy carbonic acid as a catalyst are discussed.
This work correlates the basicity of various axial ligands (AL), including triethylamine, methylimidazole, pyridine, acetonitrile or water, with the efficacy of catalytic oxidation of 2,6-di-tert-butylphenol by Co(salen)(AL) in CO 2 -expanded methylene chloride. Further, Co(salen)(AL)O 2 abstracts hydrogen atoms from substrates of high to intermediate reactivity (BDECH B*90 kcal/mol).
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