Characterization of MIPA and DIPA aqueous solutions in relation to absorption, speciation and degradation A.B. Lo ´ pez b , M.D. La Rubia b, *, J.M. Navaza a , R. Pacheco b , D. Go ´ mez-Dı ´az a a PF&PT Research Team, Department of Chemical Engineering, ETSE, University of Santiago de Compostela, Santiago de Compostela, Galicia, Spain b Bioprocesos Research Team, Department of Chemical, Environmental and Materials Engineering, EPS, University of Jae ´n, Jae ´n, Andalucı´a, Spain 1. Introduction The development of more efficient processes for carbon dioxide capture has been the aim of an important number of research projects and studies in the last years. These studies have been focused on different premises, mainly on the use and development of new solvents [1–3] or the mixture of commonly used substances for carbon dioxide separation such as amines [4,5]. There is no consensus about the possibility of substituting the best available technique, which is the use of monoethanolamine as solvent, by blends of other amines. On the one hand, in comparison with the use of single amines, these systems have been proven to be efficient by several studies where an enhancement in the absorption rate, as well as, an increase in carbon loading, were observed [6]. On the other hand some research teams observed an increase in carbon dioxide loading probably caused by a more favorable reaction mechanism in relation with the stoichiometry but no enhancement of absorption rate was detected [7]. In any case, the use of amine blends is not the most suitable alternative for carbon dioxide capture and only certain blends have shown positive results [8,9]. While some systems show an increase in carbon dioxide loading despite of an improvement in mass transfer rate is not observed, others system are not better than single amine solutions [10]. Furthermore, even though the absorption process is enhanced; the regeneration process has worse behavior than the best available technique. In general the effect of amine blend upon absorption kinetics is not well- established nowadays [8]. The regeneration step is a necessary process accomplished with the absorption process. In chemical absorption the regeneration process involves the use of high temperatures which is necessary in order to produce the reversible reaction. The liquid phase for capturing carbon dioxide needs a suitable thermal stability to avoid its degradation which could be caused by oxidative or thermal processes [11]. A high degradation rate implies the use of higher amine solutions make-up flow-rates, increasing the operation costs and environmental impact. The aim of this work is to study the use of new amines for carbon dioxide capture by chemical absorption, by means of the analysis of mass transfer rate, reaction mechanism, stoichiome- try and degradation kinetics. These substances allow analyzing the influence of the substitution degree in the nitrogen atom. Also, studies performed in this work allow evaluating the suitability of these solvents for carbon dioxide capture at an industrial level. At the same time degradation studies of these amines aqueous solutions have been also included, in order to analyze the overall process. Journal of Industrial and Engineering Chemistry 21 (2015) 428–435 ARTICLE INFO Article history: Received 3 November 2013 Received in revised form 1 March 2014 Accepted 2 March 2014 Available online 13 March 2014 Keywords: Carbon dioxide capture Amine Absorption Degradation NMR ABSTRACT The carbon dioxide absorption process by 1-amino-2-propanol (MIPA) and bis(2-hydroxypropyl)amine (DIPA) aqueous solutions in bubble column reactor have been studied considering the influence of liquid phase physical properties and the amine group substitution on the overall process. The main objective of this work was to establish the carbon dioxide capture reaction mechanism for these systems, and then to obtain the predominant stoichiometry to calculate the mass transfer coefficient. NMR technique was used to determine the species present in the liquid phase during the absorption process and to confirm the reaction mechanism. The degradation of these amines was also evaluated. ß 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved. * Corresponding author. Tel.: +34 953212920. E-mail address: mdrubia@ujaen.es (M.D. La Rubia). Contents lists available at ScienceDirect Journal of Industrial and Engineering Chemistry journal homepage: www.elsevier.com/locate/jiec http://dx.doi.org/10.1016/j.jiec.2014.03.001 1226-086X/ß 2014 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.