No abstract

Water activities of binary and ternary mixtures containing polyols were measured using an electronic hygrometer with temperature ranging from (10 to 35) °C. The concentrations of the mixtures varied according to the solubility limit for each polyol (D-sorbitol, D-mannitol, xylitol, meso-erythritol, and glycerol). Results were compared with the group contribution-based models ASOG and UNIFAC. The predictions using parameters from the literature were poor, probably as a consequence of the strongly polar hydroxyl groups bounded to consecutive carbon atoms in the polyol molecule. Better agreement was obtained by readjusting some of the interaction parameters. The data bank used in this procedure included water activity data as well as polyol solubility data taken from the literature. The best results were achieved using the UNIFAC-Larsen model with an average relative deviation of 0.9% for water activity and solubility data.

Kinematic viscosities of aqueous mixtures containing poly(ethylene glycol)s (PEGs) with nominal molecular masses ranging from (200 to 10 000) g·mol-1 have been determined at various concentrations and temperatures. The binary experimental data were used to adjust the parameters of a Kumar-like equation. Relative errors around 5.5% were observed between calculated and experimental results. The adjusted parameters also allowed the viscosity prediction for multicomponent mixtures, with an overall deviation of 9.9%.

The water activity, pH and density of some aqueous amino acid solutions were determined at 25 degrees C in three different types of solvents. Previous published experimental data on water activity and solubility of amino acids in aqueous solutions were used together with data from this work to test the applicability of a group contribution model. The activity coefficients were estimated by the UNIFAC-Larsen model combined with the Debye-Hückel equation, taking also into account the partial dissociation phenomena of species in solution. Interaction energies between the charged species Na(+) and Cl(-) and the specific groups of amino acids (COOH and NH(2)) were adjusted using experimental solubility data.

New amines for reactive absorption of CO 2 from process gases were investigated in a comprehensive experimental screening. All studied amines are derivates of triacetoneamine and differ only in the substituent of the triacetoneamine ring structure. The amines are abbreviated by the acronym EvA with a consecutive number, designating the derivate. About 50 EvAs were considered in this work from which 26 were actually synthesized and investigated in aqueous solution. The mass fraction of the amines in the unloaded solution was eitherw 0 EvA = 0.05 g/g orw 0 EvA = 0.4 g/g. The following properties were studied: solubility of CO 2 , rate of absorption of CO 2 , liquid-liquid and solid-liquid equilibrium, foaming behavior, dynamic viscosity, and acid constants. The nine most promising EvAs were evaluated with the NoVa short-cut method [1]. The method yields estimates for the specific energy demand and recirculation rate for a given purification task. Two typical purification tasks were considered: the CO 2 -removal from natural gas and from synthesis gas, respectively. Some of the EvAs showed significantly improved performance compared to monoethanolamine (MEA) and a solvent-blend of methyl-diethanolamine and piperazine (MDEA/PZ).