Studies have been made of the sorption equilibria of pyridine, picoline and lutidine in aqueous solution on ion-exchange and porous resins. The sorption behaviors of these pyridines on strong acid ion-exchange resin can be expressed by the Langmuir isotherms, and those on both weak acid ion-exchange and porous resins by the Freundlich isotherms. The sorption mechanisms followed either a neutralization reaction with the H-form ion-exchange resins, or a hydrophobic interaction with the porous resins. Methanol content of the aqueous solution as well as solution pH was found to have a significant effect on the sorption of pyridines. Furthermore, the separations of these pyridines from each other were examined for three binary solute solutions in a batch mode. The pyridines were sorbed preferentially on the resins in the following sequence:
Adsorption isotherms of a ternary mixture containing dimethyl phthalate, diethyl phthalate and di-n-butyl phthalate were measured by the step-pulse method in a wide range of concentration. They were expressed by Langmuir-type equations with weak interaction between components. The applicability or the proposed process to multicomponent continuous separation was confirmed by coupling the results of single-column experiments and simulation of the total process based on the isotherms obtained. It was found that non-linearity in adsorption isotherms had a positive effect on the separation. Separation performance depends significantly on the flow rates of desorbent fed to the columns in the refining zone and the shift time. Their effects on the separation were examined and the characteristic features of the proposed process were clarified. It was found for the ternary mixture tested that the middle component (i.e., diethyl phthalate) was quite sensitive to separation performance.
Fluid-liquid and liquid-liquid equilibria were measured for carbon dioxide-ethanol-water mixtures containing trace amounts of ethyl acetate, acetaldehyde, 2-pentanol, 1-propanol, diacetyl, acetic acid and methanol at temperatures near the critical temperature of carbon dioxide. Large separation factors were observed in the extraction of all the trace components except for acetic acid and methanol from ethanol aqueous solutions using supercritical or liquid carbon dioxide as solvent. The separation factor increased with increasing solvent density. A simple empirical model was developed to correlate the experimental data assuming the infinite dilution state for the trace components. The model correlates the separation factors with fairly good agreement with the experimental data.
The liquid-phase synthesis of methyl tert-butyl ether (MTBE) by the reaction between methanol and tert-butyl alcohol with several heteropoly acid catalysts was studied. Among the catalysts tested, acidic cesium salts of 12-tungstophosphoric acid and 12-tungstosilicic acid showed high activities and selectivities for the production of MTBE. The origin of high activity and selectivity of cesium heteropoly acids was discussed from kinetic viewpoints.
Isobaric vapor-liquid equilibrium data were measured at 74.66, 101.32 and 127.99 kPa for binary mixtures composed of methyl ethanoate or methyl propanoate and propan-2-ol using a dynamic method. In thermodynamic calcutions using the data, the vapor phase was considered to be non-ideal, and all the systems studied exhibit positive deviations from ideal solution behavior. At 74.66 kPa, the binary system (x1 methyl propanoate + x2 propan-2-ol) presents an azeotrope at x1 = 0.666, T = 340.47 K; as pressure increased, azeotrope concentration decreased quasi-regularly towards regions richer in propan-2-ol. After reduction of the data by fitting with a suitable equation and verification of thermodynamic consistency, various group-contribution models were applied to estimate the isobaric VLE data. The mean error in prediction of the activity coefficients for each system in no case exceeded 7%.
To obtain the theoretical maximum adsorption isotherms of methane in a slitlike pore of graphite carbon, the single-plane wall model, which allows molecules to be adsorbed on both sides of the graphite basal plane, is considered. The LJ potential function is used for describing interactions between both molecule-molecule and molecule-surface carbon. The equilibrium densities in a pore and in a gas phase are calculated by using the Gibbs ensemble Monte Carlo simulation technique. When the slitwidth is designed such that methane molecules are accommodated in two layers, the theoretical adsorptions in the single-plane wall pore almost quantitatively coincide with the experimental isotherms of methane and ethane on high-surface area carbon M-30 at 298 K, which suggests that carbon M-30 adsorbs methane to almost the theoretical maximum quantity. Comparisons are made with a different slitwidth pore and the double-plane wall model which assumes that only one side of the graphite plane is effective for adsorption.
A simplified method is proposed in this paper for simultaneously evaluating internal solid-film and external fluid-film capacity coefficients of mass transfer from the breakthrough curve of an adsorption bed. The method is based on a graphic technique of dividing a breakthrough curve into two pieces and is applicable to all favorable systems for adsorption. The two film capacity coefficients are directly obtained from the ratio of the time interval between the breakthrough point and the dividing point to that between the breakthrough point and the exhaustion point. Diagrams for adsorption systems with K < 0.5 for Langmuir isotherm and β < 0.5 for Freundlich isotherm are shown. Diagrams for graphically obtaining a diffusion coefficient from a breakthrough curve are also shown, and several examples of the evaluation are given.
As a new photochemical process for synthesizing 1,1-dichloroethylene (VC) from 1,1-dichloroethane (1,1-DCE), the laser-induced photochlorination of 1,1-DCE followed by its dehydrochlorination has been examined with excimer laser irradiation in a flow reactor under normal pressure and 298–623 K. In the laser-induced photochlorination of 1,1-DCE, a high selectivity for 1,1,1-trichloroethane (1,1,1-TCE), which was expected to yield VC uniquely in the following dehydrochlorination stage, was obtained in the lower temperature range. In the laser-induced photodehydrochlorination of 1,1,1-TCE, a small amount of Cl2 addition promoted the formation of VC, and the yield of VC was strongly dependent on the Cl2/1,1,1-TCE ration and the reaction temperature. By experimental work and kinetics study, both of these reactions are thought to proceed by a chain mechanism. By connecting two reaction cells in series, in which the above two reactions are individually carried out, a new photochemical process for synthesizing VC from 1,1-DCE was designed. In this system, experimental results suggested that two factors, the complete consumption of substrate in the first cell and the addition of Cl2 before the second cell, are important for attaining a higher selectivity for the desired product.
Changes in conformational and surface properties in refolding processes were quantitatively investigated in aqueous two-phase systems, using bovine carbonic anhydrase (CAB) as a model protein. Surface net hydrophobicity (HFS) of a native CAB was determined as –84 kj·mol–1, showing a moderately hydrophilic surface. By addition of 1.5–2 M guanidine hydrochloride (GuHCl), CAB was denatured and HFS increased drastically up to about 300 kj·mol–1, accompanied by some increment of local hydrophobicity. The fully unfolded state was achieved in 5 M GuHCl. The unsteady change of local hydrophobicity during CAB refolding was also quantified using phase separation of Triton solution. Yield of CAB reactivation was enhanced by the addition of Triton X-405, due to hydrophobic interaction with hydrophobic residues exposed during the refolding process.
A plant cell culture controlling phytohormone concentration was undertaken in a bioreactor system equipped with a 2,4-dichlorophenoxyacetic acid (2,4-D)-adsorbed activated carbon column, through which the culture medium was recirculated. Elation of 2,4-D from the column was controlled by the medium recirculation rate. The elution kinetics was expressed by a simple model based on the liquid film theory. Using this system, a 2,4-D intermittently feeding culture revealed that the 2,4-D uptake rate of Phytolacca americana callus was associated with the growth rate. In the 2,4-D constantly feeding culture, the 2,4-D concentration in the medium was maintained at an almost constant level after medium recirculation.
The present paper, which is predominantly experimental, provides information on bubble shape, drag coefficient and bubble rocking in highly viscous Newtonian and non-Newtonian media, which was hitherto lacking. Results covering a wide range of bubble size (about 0.2–3 cm equivalent spherical diameter) are reported. The observed changes in bubble shape as the ratio of the major axis of the bubble to equivalent spherical diameter and the aspect ratio are shown, and empirical correlations are obtained. The drag coefficient calculated from the terminal velocity data for gas bubbles provides reasonable agreement with the Hadamard-Rybczynski equation in both highly viscous Newtonian and non-Newtonian media in the low Reynolds number region. Furthermore, bubble rocking caused by wake shedding was observed in the higher Reynolds number region in non-Newtonian media. The Strouhal number including bubble rocking frequency is correlated with the Reynolds number and the Morton number.
The crystallization and transformation behavior of the polymorphs of L-histidine (A, B) and the transformation kinetics were investigated in aqueous solutions. Both polymorphs precipitate in almost the same ratio from solutions in a wide concentration range. The ratio of the polymorphs. in the precipitate was scarcely influenced by temperature, unlike the behavior of L-glutamic acid. Transformation from B to A with a solution-mediated transformation mechanism occurred. The activation energy for the overall transformation was estimated as about 38 kJ/mol. From measurements of the solubilities at temperatures between 283 and 333 K, it was confirmed that A is a stable and B a metastable form. From a van’t Hoff plot the heat of fusion of L-histidine polymorphs was obtained as 15 kJ/mol, which is about half that of L-glutamic acid. No seed effect of either A or B crystals on the precipitation behavior was observed. A kinetic study of the transformation process was carried out and both the rate constants of growth of A(kG) and dissolution of B crystals(kD) were estimated simultaneously. At 313 K kD was nearly six times larger than kG, indicating that the transformation process is growth-controlled.
A new system to measure very short bubble coalescence time was developed using a laser. The system’s reliability was confirmed by comparing the system output with photographic observation by high-speed video camera. The result for aqueous solutions of n-alcohol was in good agreement with the previous data. The system was applied to various kinds of aqueous solutions more dilute than those in previous work where the value of bubble coalescence time was expected to be less than 2 ms. It was revealed that the bubble coalescence time reported in previous work was composed of two parts. The first part was the time length of the contacting period of two bubbles and the second was the time length of the initial stage of a film rupture between the bubbles. The former decreased considerably, even to an undetectably small value, with decrease in concentration, but the latter was constantly at about 0.3 ms regardless of concentration. Effects of bubble age and bubble approach velocity were examined. It was also found that the bubble coalescence time in surfactant solution was significantly influenced in a narrow concentration region as low as ppb order and that the bubbles did not coalesce in solution of higher concentration.