Simultaneous measurement absorption of CO2 and H2S mixture into aqueous solutions containing Diisopropanolamine blended with 1-butyl-3-methylimidazolium acetate ionic liquid

Abstract

In environmental industry, capturing of acid gases, particularly CO2, has always been a major problem. The different techniques such as absorption and adsorption processes have been used for removal of acid gases from flue and natural gases. In recent years, a new type of solvent, known as green solvent or ionic liquid (IL), due to its notable properties has been introduced. In this work, the mixtures of aqueous solutions of Diisopropanolamine (DIPA) blended with 1-butyl-3-methylimidazolium acetate ([bmim][acetate]) ionic liquid (IL) are used. Using a static high pressure equilibrium cell, the simultaneous absorption of a gas mixture of CO2 (70mol%) and H2S (30mol%) into aqueous solutions of DIPA blended with [bmim][acetate] was measured. The gas compositions were chosen in close to highest sour natural gas streams in gas treatment plants. The weight percent of the aqueous DIPA+ionic liquid systems are (50wt%+5wt%), (50wt%+10wt%), (30wt%+5wt%), (30wt%+10wt%) and (50wt%+50wt%), respectively. The experiments were carried out at 323.15 and 348.15K and in total pressure range of about 0.2–2.5MPa. The results illustrate that an increase in temperature and decrease in DIPA concentration lead to lower solubility of the both acid gases. Moreover, it can be deduced from the results that using ionic liquid at low concentrations leads to lower solubility of CO2 because of diminishing the solution alkalinity. However, at high IL concentrations, more CO2 absorption takes place through physical absorption. On the other hand, H2S solubility enhances at the whole range of ionic liquid mass percent, because the present IL is more selective towards H2S that leads to intensify physical absorption.