International Journal of Greenhouse Gas Control 26 (2014) 39–50 Contents lists available at ScienceDirect International Journal of Greenhouse Gas Control j ourna l h o mepage: www.elsevier.com/locate/ijggc Catalytic and non catalytic solvent regeneration during absorption-based CO 2 capture with single and blended reactive amine solvents Huancong Shi, Abdulaziz Naami, Raphael Idem ∗ , Paitoon Tontiwachwuthikul International Test Centre for CO2 Capture (ITC), Faculty of Engineering and Applied Science, University of Regina, Regina, Saskatchewan S4S 0A2, Canada a r t i c l e i n f o Article history: Received 1 October 2013 Received in revised form 17 March 2014 Accepted 7 April 2014 Keywords: Solvent regeneration Blended quaternary amine systems Heat duty reduction Catalyst-aided CO2 stripping Potential energy surface diagram Bicarbonates a b s t r a c t Molecular potential energy surface (PES) diagrams of the deprotonation of a protonated amine (AmineH + ) were used in combination with ion speciation plots of the vapour liquid equilibrium (VLE) model to provide a better understanding of the reasons for the drastic reduction of energy required for CO 2 stripping from some amine solutions under certain operating conditions. Experiments for CO 2 stripping were performed using single and blended amines (namely, MEA, MEA–MDEA, MEA–DEAB (4-(diethylamine)-2- butanol)) with and without solid acid catalysts (Al 2 O 3 or HZSM-5) at 90–95 ◦ C. The heat duty to regenerate 5 M MEA without any catalyst was the baseline taken as 100%. The results showed that the CO 2 stripping performance in terms of heat duty decreased in the order: MEA–DEAB with HZSM-5 (38%) > MEA–DEAB with -Al 2 O 3 (40%) > MEA–DEAB with no catalyst (51%) > MEA with HZSM-5 (65%) > MEA with -Al 2 O 3 (73%) > MEA–MDEA with -Al 2 O 3 /no catalyst (74%), all relative to MEA with no catalyst (100%). The results further show that the addition of MDEA or DEAB (as tertiary amines) in a blended solvent provided R 3 N and HCO 3 - , which split and thus decreased the free energy gaps. On the other hand, even though MDEA is intrinsically less basic as per the energy diagram, DEAB generated a lot more HCO 3 - resulting in a tremendously lower heat duty. -Al 2 O 3 (Lewis acid) was more effective in the CO 2 lean region by duplicating the role of HCO 3 - , which is negligible in the CO 2 lean region, whereas HZSM-5 (Brnsted acid) is effective throughout the loading range by donating protons. The implication is that the use of solid acid catalysts could result in stripper size and heat duty reductions during solvent regeneration. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction Carbon capture, utilization and storage (CCUS) is a major option that can be used to mitigate carbon dioxide emissions which is blamed for global warming and climate change. The amine-based post-combustion capture of CO 2 is regarded as one of the mature technologies that can be employed in CCUS. The major drawback of this technology is that the energy required for the process, espe- cially during solvent regeneration for CO 2 stripping, is still too high (Idem et al., 2006). Recently, Rochelle (2009) has highlighted the approaches that could be used to minimize the heat required for regeneration. Using the bench mark solvent of 30 wt% (5 kmol/m 3 ) MEA aqueous solutions, the optimized energy required has been reported to be in the range from 2057 to 3165 kJ/kg of CO 2 according to data from the literature in the 1980s (Astarita et al., 1983). More recent heat duty of the main amine scrubbing pilot plants in the US, ∗ Corresponding author. Tel.: +1 306 585 4470; fax: +1 306 585 4855. E-mail address: raphael.idem@uregina.ca (R. Idem). utilizing the same solution, was reported to be 0.37 MWh/ton CO 2 (i.e. 1468.8 kJ/kg CO 2 ) in 2001 and 0.51 MWh/ton CO 2 (2023.2 kJ/kg CO 2 ) in 2006, respectively (Rochelle, 2009), which shows that heat duty has been greatly decreased. According to Rochelle (2009), the theoretical minimum energy of CO 2 separation and compres- sion is estimated to be (0.11 MWh/ton CO 2 /435.6 kJ/kg CO 2 ) which remains a challenge to be attained. This researcher suggested that the two significant methods to cut heat duty to achieve the expected value were solvent optimization and process integration. The heat duty is considered to be more specific to operat- ing conditions such as temperature (T) and pressure (P) with less dependence on process configurations, with the exception of process integration and heat optimization (Sakwattanapong et al., 2005). A number of researchers have reported measures that have been used to effectively reduce heat duty (Idem et al., 2006; Aroonwilas and Veawab, 2007; Sakwattanapong et al., 2005; Rochelle, 2009; Zhang et al., 2012). These include the development of a series of different novel solvents, which can reduce the heat duty from 1.738 to 0.409 MWh/ton CO 2 (i.e. 6256.8–1742.4 kg/kg CO 2 ) and reflux ratio of H 2 O/CO 2 from 0.7 to 0.1 (Feron, 2010). http://dx.doi.org/10.1016/j.ijggc.2014.04.007 1750-5836/© 2014 Elsevier Ltd. All rights reserved.