Mass transfer characteristics of gases in methanol and ethanol under elevated pressures and temperatures

Abstract

Abstract The effect of pressure, temperature and mixing speed on the solubilities C*) and mass transfer coefficients KLa for different gases (H2, N2, CO, CH4 and CO2) in two liquids (methanol and ethanol) were investigated in a 4-liter gas-inducing agitated autoclave. The C* and kLa values were obtained using a modified Peng-Robinson equation of state and the transient physical gas absorption technique respectively. The C* values for all gases studied in methanol and ethanol were found to increase with the solute gas partial pressure P1,F. In the range of operating conditions used, the solubilities of the gases in both liquids behaved as (C*)CO2 > (C*)CH4 > (C*)CO > (C*)N2 > (C*)H2. At 328 K and 378 K the C* values for H2, N2, CO and CH4 in ethanol were slightly higher and those for CO2 were lower than those in methanol. At 428 K, however, the C* values for H2, N2, CO and CH4 were slightly higher and those for CO2 were lower than those in ethanol. kLa values for all gases in methanol and ethanol appeared to be a strong function of mixing speed and increased slightly with the mean partial pressure of the gas component P1,m. kLa values for H2 in methanol and ethanol were the highest, those for CO2 were the lowest, and kLa values for N2 CO and CH4 in both liquids were not significantly different. An empirical correlation was proposed to predict kLa values fo H2, N2, CO, CH4 and CO2 in methanol and ethanol with a reasonable accuracy.