Chemical Engineering Journal 175 (2011) 388–395 Contents lists available at ScienceDirect Chemical Engineering Journal jo u r n al hom epage: www.elsevier.com/locate/cej Synthesis and usage of common and functionalized ionic liquids for biogas upgrading Christian Bidart a,∗ , Romel Jiménez b , Carlos Carlesi c , Mauricio Flores d , Álex Berg d a Institute for Industrial Production, Karlsruhe Institute of Technology, Karlsruhe, Germany b Departamento de Ingeniería Química, Universidad de Concepción, Concepción, Chile c Escuela de Ingeniería Química, Pontificia Universidad Católica de Valparaíso, Valparaíso, Chile d Unidad de Desarrollo Tecnológico (CCTE-UDT), Universidad de Concepción, Coronel, Chile a r t i c l e i n f o Article history: Received 2 March 2011 Received in revised form 5 July 2011 Accepted 20 July 2011 Keywords: Task-specific ionic liquid Carbon dioxide absorption Biogas upgrading Amines a b s t r a c t Halide imidazolium-based ionic liquids 1-butyl-3-methylimidazolium bromide [bmim][Br] and 1- propylamine-3-methylimidazolium bromide [pamim][Br] were synthesised and tested experimentally as absorbents for biogas upgrading . The former solvent is a conventional off-the-shelf room temperature ionic liquid (RTIL), which is soluble in water and expected to have a high CO 2 solubility. The second solvent is a new type of task-specific ionic liquid (TSIL) and has a straight amine-alkyl substitute incorporated to enhance CO 2 solubility. Experimental evidence suggests that the majority of known imidazolium-based ionic liquids are good CO 2 absorbents; adding these to a designed solvent that combines a long amino- alkyl lineal group is expected to improve the performance of CO 2 absorption over other alternatives under discussion. CO 2 absorption experiments were conducted in an absorbing column packed with randomly placed Raschig rings. A biogas model consisting of CO 2 (43% v/v) diluted in N 2 was used to test CO 2 uptake with aqueous solutions of the above-mentioned ILs at 5%, 10% and 15% (w/w) concentrations. The gaseous and liquid streams were operated under concurrent flow with a gas–liquid volumetric ratio of 1:2. Addition- ally, absorption tests were conducted with aqueous solutions of monoethanolamine (MEA) mixed with the ILs under investigation to elucidate potential activations of these amino solutions. In this experiment, the ILs used for biogas upgrading do not present a higher absorption than amino solutions, and there were no significant synergy results from mixing them with MEA, which could have enhanced the CO 2 uptake. © 2011 Elsevier B.V. All rights reserved. 1. Introduction The capture of carbon dioxide (CO 2 ) through efficient and cost- competitive processes has become a major technological challenge for the reduction of atmospheric greenhouse gases. The develop- ment of low-emission technology and design of high-performance novel solvents to capture CO 2 by means of standard technology will be a main focus of chemical and process science in the near future [1]. In biogas upgrading, the processes of adjustment of calorimetric and chemical properties by removing CO 2 and undesirable com- pounds [2] are of interest due to the particularities of the generation and treatment of this biofuel, as well as its potential as a renewable source of energy. Prior experience in removing acid gases (obtained from the petroleum or natural gas industries) has contributed to the existing body of knowledge; however, in some cases, certain aspects have been rendered inapplicable. ∗ Corresponding author. Tel.: +49 721 608 44513; fax: +49 721 75 89 09. E-mail address: cbidart@udec.cl (C. Bidart). Among the state-of-the-art technologies based on chemical absorption to upgrade biogas, the most widely used solvents are alkanolamines, such as monoethanolamine (MEA), diethanolamine (DEA) or methyldiethanolamine (MDEA). These solvents are gener- ally dissolved in water to reduce corrosion problems and to enhance the CO 2 loading and rate of absorption [2,3]. These solutions for the upgrading of biogas, which is normally generated by anaero- bic digestion at atmospheric pressure in the 40–60 ◦ C temperature range, are characterised by a high capacity for removal of CO 2 from a crude biogas stream with a typical composition of 40–60% CH 4 , 30–45% CO 2 , water and other trace compounds [4]. Nonetheless, amino solvents mainly exhibit disadvantages as a result of chem- ical decomposition (with the consequent loss of CO 2 -remotion performance), toxicological impacts for fugitive emissions, and equipment corrosion and high enthalpy of reaction, which makes the process highly energy-intensive for the amino regeneration. This disadvantage is a limiting factor for large-scale applications [5]. Several characteristics have drawn significant attention to ionic liquids (ILs) as an alternative absorption media to traditional 1385-8947/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.cej.2011.07.024