**Solvents for Carbon Dioxide Capture**

Fernando Vega, Mercedes Cano, Sara Camino,

**Solvents for Carbon Dioxide Capture**

Fernando Vega, Mercedes Cano, Sara Camino, Luz M. Gallego Fernández, Esmeralda Portillo and Benito Navarrete Luz M. Gallego Fernández, Esmeralda Portillo and Benito Navarrete Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.71443

#### **Abstract**

Anthropogenic CO2 emissions are considered the major contributor of greenhouse gas emissions worldwide. The mitigation of this kind of CO2 emissions relies on a portfolio of alternatives where CO2 absorption appears as the nearest approach to be applied at industrial scale. Researchers have been focused on developing new formulations of solvents to make more competitive CO2 absorption as a carbon capture and storage (CCS) technology. In this sense, this chapter summarizes both the conventional solvents and the most recent investigations on this field. Chemical absorption is more suitable for a lot of industrial process due to the flue gas conditions: ambient pressure, low CO<sup>2</sup> concentration and large volume. Therefore numerous novel solvents came up in recent years and they are further discussed in this chapter. The most recent solvents, their mechanisms and kinetics and the advantages and disadvantages are also included. Finally, physical solvents are adequate in high CO2 partial pressure applications and they are reported in the last section. Although physical absorption field is constrained to high-pressure flue gas, physical solvents provided higher performance in CO2 separation process and their characteristics are also summarized.

DOI: 10.5772/intechopen.71443

**Keywords:** solvent, CO2 , CCS, absorption, capture

### **1. Introduction**

Carbon capture and storage (CCS) is one of the pathways for anthropogenic CO2 emission mitigation. Among the wide portfolio of CCS technologies, physical and chemical absorption are considered the most close-to-market approaches to be applied at industrial scale, mainly focused on their implementation in energy production from fossil fuels [1]. Physical absorption is based on the CO2 solubility into the solution without chemical reaction which is

Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons

based on Henry's law and hence high CO2 partial pressures and low-temperatures are highly recommended for its application. Chemical absorption is based on the reaction between CO2 and specific compounds—solvents—that lead to form a weak bond between CO<sup>2</sup> and the solvent. Chemical absorption occurs indeed at low CO2 partial pressure. Low-temperature is also recommended for this mechanism. Numerous solvents have been developed since the first chemical absorption process was patented in the early 1930s. However, the implementation of CO2 absorption at industrial processes such as cement production, iron and steel manufacturing and fossil-fuel power plants requires novel solvent formulations that can address the main constrains limiting its deployment: the huge volume of treated gas, the low CO<sup>2</sup> concentration in the flue gas and the presence of trace components such as NO<sup>x</sup> , SO2 and particulate matter which degrade the solvents [2, 3]. This chapter summarizes both conventional and newly developed solvents mainly focused on CO2 capture processes based on physical and chemical absorption. A deep revision of the solvents reported from the literature was made including primary, secondary, tertiary amines and non-amine-based solvents. Novel solvents such as sterically hindered amines and blends were discussed further. In respect to physical solvents, authors report the conventional solvents used by licensed processes such us Rectisol™, Selexol™, Sulfinol™ and Purisol™. Special attention will be paid in ionic liquids and novel biphasic configurations and their use as CO<sup>2</sup> capture solvents.
