Viktor Ermatchkov

Chemical equilibrium constants for the formation of carbamates in (carbon dioxide + piperazine + water) from 1H-NMR-spectroscopy

Abstract 1 H -NMR spectroscopic investigations were performed on aqueous solutions of carbon dioxide and piperazine at temperatures ranging from (283 to 333) K to determine quantitatively the speciation. The experimental results were used to determine the chemical equilibrium constants for the formation of piperazine carbamate, piperazine dicarbamate and protonated piperazine carbamate.

Solubility of Carbon Dioxide in Aqueous Solutions of N-Methyldiethanolamine and Piperazine in the High Gas Loading Region

A synthetic technique was used to measure the solubility of carbon dioxide in three aqueous solutions of 2,2′-methyliminodiethanol (N-methyldiethanolamine, MDEA) and piperazine (PZ) at around (313, 333, 353, and 393) K and pressures between about (0.2 and 10) MPa. The molalities of (MDEA + PZ) in the aqueous solutions were (2.2 + 1.97), (4.22 + 2.01), and (7.83 + 2.07), respectively. The loading of the amines by carbon dioxide (i.e., the molar ratio of (MDEA + PZ) and CO2 varied between 0.2 and 2.0 The new experimental results are to supplement previously published experimental data of our research group for a single solution of both amines {molalities of (MDEA + PZ) in the aqueous solutions: (2.0 + 2.0)}. The new experimental results are compared to predictions from a model that combines previously published models for (CO2 + MDEA + H2O) and (CO2 + PZ + H2O).

Influence of Salt and pH on the Swelling Equilibrium of Ionizable N-IPAAm Based Hydrogels: Experimental Results and Modeling

The influence of sodium chloride and of pH on the equilibrium swelling of ionic hydrogels consisting of N-isopropyl acrylamide (N-IPAAm), a weak cationic comonomer N-[3-(dimethylamino)propyl] methacrylamide (DMAPMA) and/or a strong anionic comonomer 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPS) was investigated in aqueous solutions at 298 K. The mass fraction of the polymerizable substances in the aqueous solution was kept at 0.1. The sum of the mole fractions of the comonomers in the gel was 0.05 while the mole fraction of a single comonomer was varied between 0 and 0.05. The mass fraction of NaCl in the aqueous solution was varied between 3 · 10−6 and 0.25. The pH-sensitive comonomer DMAPMA causes an influence of pH on the degree of swelling. The pH of the aqueous solutions was adjusted by adding HCl or NaOH. A thermodynamic framework was applied to model (i.e., correlate and predict) the experimental results. The calculations revealed that dissolved carbon dioxide (resulting from air that was in contact with the condensed phases) might have a remarkable influence on the swelling behavior.