Ionic liquids (ILs) are being considered as solvents for gas absorption processes as they have the potential, in general, for improved efficiency of gas separations, as well as lower capital and operating costs compared to current commercial processes. In this study the solvent properties of ILs are investigated for use in the absorption of carbon dioxide (CO2) and oxygen (O2). The absorption of these gases in ILs was measured in the temperature range 303.15-333.15 K and at pressures up to 1.5 MPa by gravimetric analysis. The ILs used were methyl trioctyl ammonium bis (trifluoromethylsulfonyl) imide ([MOA][Tf2N]), 1-butyl-3-methyl imidazolium bis (trifluoromethylsulfonyl) imide ([BMIM][Tf2N]), and 1-butyl-3-methyl imidazolium methyl sulfate ([BMIM][MeSO4]). The measurement technique employed in this study is fast and accurate, and requires small quantities of solvent. The results indicated that absorption of both gases increased with a decrease in operating temperature and an increase in pressure. [MOA][Tf2N] had the highest CO2 and O2 solubility. [BMIM][Tf2N] was determined to have the highest selectivity for CO2 absorption. [BMIM][MeSO4] achieved the lowest CO2 absorption with a moderate O2 absorption, revealing this IL to be the least desirable for CO2 and O2 absorption. Calculation of Henry's law constants for all systems confirmed the deductions made from absorption data analysis. Calculation of enthalpy and entropy of absorption for each system revealed CO2 absorption in [MOA][Tf2N] to be the least sensitive to temperature increases. The absorption data was modeled using the generic Redlich-Kwong cubic equation of state (RK-EOS) coupled with a group contribution method.

No abstract

No abstract

Carbon dioxide (CO 2) emissions and their association with climate change are currently a major discussion point in government and amongst the public at large in South Africa, especially because of the country's heavy reliance on fossil fuels for electricity production. Here we review the current situation regarding CO 2 emissions in the South African power generation sector, and potential process engineering solutions to reduce these emissions. Estimates of CO 2 emissions are presented, with the main sources of emissions identified and benchmarked to other countries. A promising mid-term solution for mitigation of high CO 2 emissions, known as CO 2 capture and storage, is reviewed. The various aspects of CO 2 capture and storage technology and techniques for CO 2 capture from pulverised coal power plants are discussed; these techniques include processes such as gas absorption, hydrate formation, cryogenic separation, membrane usage, sorbent usage, enzyme-based systems and metal organic frameworks. The latest power plant designs which optimise CO 2 capture are also discussed and include integrated gasification combined cycle, oxy-fuel combustion, integrated gasification steam cycle and chemical looping combustion. Each CO 2 capture technique and plant modification is presented in terms of the conceptual idea, the advantages and disadvantages, and the extent of development and applicability in a South African context. Lastly, CO 2 transportation, storage, and potential uses are also presented. The main conclusions of this review are that gas absorption using solvents is currently most applicable for CO 2 capture and that enhanced coal bed methane recovery could provide the best disposal route for CO 2 emissions mitigation in South Africa.