PROCESS SYSTEMS ENGINEERING Investigation Mechanism of DEA as an Activator on Aqueous MEA Solution for Postcombustion CO 2 Capture Helei Liu Clean Energy Technologies Research Institute (CETRI), University of Regina, Saskatchewan, Regina, S4S 0A2, Canada Moxia Li, Xiao Luo, and Zhiwu Liang Joint International Center for CO 2 Capture and Storage (iCCS), Provincial Hunan Key Laboratory for Cost-effective Utilization of Fossil Fuel Aimed at Reducing Carbon-dioxide Emissions, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, PR China Raphael Idem and Paitoon Tontiwachwuthikul Clean Energy Technologies Research Institute (CETRI), University of Regina, Saskatchewan, Regina, S4S 0A2, Canada Joint International Center for CO 2 Capture and Storage (iCCS), Provincial Hunan Key Laboratory for Cost-effective Utilization of Fossil Fuel Aimed at Reducing Carbon-dioxide Emissions, College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, PR China DOI 10.1002/aic.16165 Published online in Wiley Online Library (wileyonlinelibrary.com) In this work, Diethanolamine (DEA) was considered as an activator to enhance the CO 2 capture performance of Monoe- thanolamine (MEA). The addition of DEA into MEA system was expected to improve disadvantages of MEA on regener- ation heat, degradation, and corrosivity. To understand the reaction mechanism of blended MEA-DEA solvent and CO 2 , 13 C nuclear magnetic resonance (NMR) technique was used to study the ions (MEACOO - , DEACOO – , MEA, DEA, MEAH 1 , DEAH 1 ,HCO 2 3 , CO 22 3 ) speciation in the blended MEA-DEA-CO 2 -H 2 O systems with CO 2 loading range from 0 to 0.7 mol CO 2 /mol amine at the temperature of 301 K. The different ratios of MEA and DEA (MEA: DEA 5 2.0:0, 1.5:0.5, 1.0:1.0, and 0:2.0) were studied to comprehensively investigate the role of DEA in the system of MEA-DEA- CO 2 -H 2 O. The results revealed that DEA performs the coordinative role at the low CO 2 loading and the competitive role at high CO 2 loading. Additionally, the mechanism was also proposed to interpret the reaction process of the blended solvent with CO 2 . V C 2018 American Institute of Chemical Engineers AIChE J, 00: 000–000, 2018 Keywords: mechanism, CO 2 absorption, blended solvent, NMR Introduction Global warming is becoming more and more dramatically evident, for which CO 2 is the main contributing factor. As the main emission source of CO 2 is attributed to the combustion of fossil fuels (such as coal, petroleum, and natural gas), the fossil fuels should be mined and used reasonably to decrease these emissions. Furthermore, to alleviate global warming and improve the quality of the environment, CO 2 needs to be cap- tured and stored effectively. 1 Moreover, the captured CO 2 could generate a noticeable economic benefit for the daily pro- duction of oil in Enhanced Oil Recovery, as well as for car- bonated beverage production and greenhouse cultivation. In addition, it is urgent for both environmental protection and economic development to carbon capture and utilization (CCU). 2,3 Chemical absorption by using amine solvents, a well- studied CO 2 processing technology, has become the main industrial process for CO 2 capture due to its advantages of fast absorption rate, high absorption capacity and low rates of equipment corrosion. 4,5 Although a lot of effort have been spent on exploiting more effective solvents, there is still a lot of work to do. There are two ways to obtain the effective sol- vents, one is to design and synthesize more new solvents, the other one is to improve the performance of the present sol- vents. Monoethanolamine (MEA), a primary amine, is the commonly used industrial solvent for CO 2 capture. However, it still has some disadvantages, such as high reaction enthalpy, regeneration energy, corrosivity and tendency of degradation, 6 Many investigations have been carried out for CO 2 absorption into blended amines containing the advantages and overcom- ing the disadvantages of different amines. Some researchers have studied the mechanism of CO 2 absorption into blended systems. Rinker et al. 7 studied the CO 2 absorption behavior in the blended system of DEA-MDEA, which showed that MDEA does not contribute significantly to the deportation of Correspondence concerning this article should be addressed to Z. Liang at zwliang@hnu.edu.cn or P. Tontiwachwuthikul at paitoon@uregina.ca. V C 2018 American Institute of Chemical Engineers AIChE Journal 1 2018 Vol. 00, No. 00