CO2 solubility and thermophysical properties in aqueous mixtures of piperazine and diethanolamine

Abstract

The population rise and economic development lead to increased energy utilization. This energy utilization is largely based on fossil fuel combustion and the industrial operations in oil and gas industry that result in CO2 emissions. The solvent mixtures of piperazine/diethanolamine (PZ/DEA) were examined to substitute for improved carbon dioxide (CO2) absorption from the natural gas stream. The CO2 solubility in the blends of the piperazine (PZ) and diethanolamine (DEA) was evaluated at 303.2, 323.2, and 343.2 K, and partial pressures of CO2 at (100–1000 kPa). The mixtures considered were DEA (20, 40 wt%), DEA (20 wt%) + PZ (5 wt%), DEA (20 wt%) + PZ (10 wt%), DEA (40 wt%) + PZ (5 wt%), and DEA (40 wt%) + PZ (10 wt%) aqueous solutions. The CO2 loadings (mole CO2/mole amine) into the solutions were described concerning the equilibrium partial pressures of CO2 at the considered temperatures. An increase in solubility of CO2 was achieved using aqueous PZ, showing prospects to be a desirable mixture with the DEA solvent for CO2 absorption. The experimental results showed reasonable correlations to the modified Kent-Eisenberg model. The refractive index and density data of the alkanolamine blends were determined as a feature of temperature, demonstrating the decrement in the thermophysical properties when the temperature of the mixtures was increased. These findings on CO2 solubility and thermophysical properties provide key insights into the screening and practical use of next-generation solvents for CO2 absorption.