The effect of pH and salt concentration on the partitioning behavior of bovine serum albumin (BSA) and cytochrome c in an aqueous two-phase polymer system containing a novel pH-responsive copolymer that mimics the structure of proteins and poly(ethylene glycol) (PEG) was investigated. The two-phase system has low viscosity. Depending on pH and salt concentration, the cytochrome c was found to preferentially partition into the pH-responsive copolymer-rich (bottom) phase under all conditions of pH and salt concentrations considered in the study. This was caused by the attraction between the positively charged protein and negatively charged copolymer. BSA partitioning showed a more complex behavior and partitioned either to the PEG phase or copolymer phase depending on the pH and ionic strength. Extremely high partitioning levels (partition coefficient of 0.004) and very high separation ratios of the two proteins (up to 48) were recorded in the new systems. This was attributed to strong electrostatic interactions between the proteins and the charged copolymer.

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The catalytic transformations of toluene, 1,2,4-trimethylbenzene (TMB), and an equimolar mixture of the two compounds were investigated over H-mordenite and H-ZSM-5 catalysts. A series of experiments were conducted in a riser simulator over a temperature range of 300−400 °C and reaction times of 5−20 s. The influence of reaction conditions on variation of 1,2,4-TMB conversion, toluene conversion, para- to ortho-xylene ratio, xylenes to TMB isomers ratio, 1,3,5-TMB to 1,2,3-TMB ratio, and xylenes to benzene ratio were discussed. The study also includes the development of comprehensive kinetic models for isomerization, disproportionation, and transalkylation reactions of 1,2,4-TMB and toluene. The models account for reversibility of the isomerization reaction based on values of temperature dependent thermodynamic equilibrium constants. Catalysts deactivation was modeled using an activity decay function based on time-on-stream (TOS). The developed models gave a good match with experimental data based on a statistically significant estimate of the kinetic parameters in the models. For the 1,2,4-TMB reaction and transalkylation of 1,2,4-TMB with toluene, the apparent activation energy over H-ZSM-5 was higher than that over H-mordenite (i.e., E app,(H-ZSM-5) > E app,(H-Mordenite)) while the reverse order was observed for the toluene reaction over the two catalysts. A simple correlation that gives accurate representation of the temperature dependency of thermodynamic equilibrium compositions of TMB isomers was also reported.

Thermo-economics analysis was used to identify the most economic distillation hybrid configuration to dehydrate bioethanol mash (12 wt%) to fuel grade (99.5 wt%) based on economic objective of minimization of operating cost in this work. Three different hybrids of THIDC with azeotropic and, extractive distillation units were assessed using similar feed and product specifications of 1200 kmol/h (12 wt% ethanol) and 55 kmol/h (99.5 wt% ethanol) respectively . The six hybrid configurations were simulated using Aspen Plus ®. The hybrid of THIDC with conventional extractive distillation (THEX1) was shown to have the lowest irreversibility rate (lost work) and highest exergetic efficiency followed by the hybrid containing thermally extractive sequence (THEX3). The latter also has the lowest energy consumption. However, economic evaluation showed that thermally coupled extractive distillation hybrid (with THIDC) is the most attractive hybrid configuration dehydrating bioethanol to fuel grade at commercial scale with the highest return on investment (ROI) and the least annual product cost. This indicates its economic attractiveness when compared with the other hybrids considered in this work. The trade-off existing between economic and exergy efficiency favors the selection of THEX3 as the preferred choice for bioethanol refining among all the six hybrids investigated.

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We present a volume-explicit equation of state for hard spheres and their mixtures that performs well in the isotropic, metastable, and random close-packed regions. The equation gives the exact second and third virial coefficients at low pressures and predicts the correct random close-packed density at infinite pressures. Comparison with simulation data showed that the equation is accurate for the isotropic, metastable, and random close-packed regions. The equation predicts phase splitting in the metastable region for molecules with large size differences.

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