Studies on viscosity and conductivity of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-glycerol and CO2-DBU-glycerol solutions at temperatures from 288.1 K to 328.1 K

Abstract

Solutions of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU)-glycerol are promising chemical absorbents for CO2 removal. Understanding the physicochemical properties of the solution and solution-absorbed CO2 are essential for its applications. The viscosity and electrical conductivity of DBU-glycerol and CO2-DBU-glycerol solutions were studied using a cone-plate viscometer and a conductivity-measuring instrument, respectively, at temperatures from 288.1 K to 328.1 K. For the DBU-glycerol system, the viscosity decreases with increasing temperature, whereas its conductivity increases. The viscosity and conductivity initially increase with DBU molar fraction (x1), with maximum viscosity and conductivity observed at x1 = 0.2153 and 0.0914, respectively. The viscosity and conductivity were calculated using the Redlich-Kister method and Castell-Amis equation, respectively. For the CO2-DBU-glycerol system, the highest viscosity was 52 times higher than that of DBU-glycerol system when the mass content of CO2 (ωCO2, based on the total mass of DBU and glycerol) was less than 0.08. However, the conductivity decreased by approximately 70–89% when ωCO2 increased from 0 to 0.0417 for x1 = 0.1000 or from 0 to 0.0886 for x1 = 0.2000. But when x1 = 0.5000, 0.7500 and 0.8333, the conductivity initially increased by 1.4–14 times and subsequently decreased by 6–95% when ωCO2 increased from 0 to 0.1395. Modified viscosity and conductivity models are proposed herein for the CO2-DBU-glycerol mixtures with average relative deviations of 5.13% and 2.99%, respectively.