CO2 capture using ionic liquids

• Autor(a) principal: Correia, Cristina Isabel Pereira
• Data de Publicação: 2020
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10773/30417
• topic: Protic ionic liquids; Carbon dioxide; Density; Solubility; Modelling

The emission of greenhouse gases into the atmosphere, in particular carbon dioxide (CO2), has become problematic due to climate change. To combat this problem, many researchers have focused their activities on the development of new processes and methodologies to mitigate greenhouse gases. Among the alternatives, carbon capture and storage technologies play a key role in mitigating CO2. Within the range of solvents proposed as innovative and with a high potential for CO2 capture, ionic liquids (ILs) offer unique properties, being a promising alternative in the replacement of critical solvents commonly used in the physical sorption of this gas. Although the potential of ILs is evident in CO2 capture, the application of these solvents to industrial-scale processes is still at a very early stage. This is partly due to the little knowledge of thermophysical properties of ILs, such as density and solubility, that limit the development of robust models essential in the development of processes. Thus, in this thesis, ILs based on carboxylates are evaluated as potential solvents for CO2 capture. To study the viability of this alternative, liquid-vapor equilibrium data are necessary. In addition, the description of thermophysical properties by equations of state (EoS) are essential for the design of industrial process. The solubility data - pVT diagram - were obtained using an isochoric cell, in the range of temperatures and pressures from 303 to 343 K and 0.1 to 0.5 MPa. The density data were measured using a high-pressure measuring cell - diagram ρpT - in the temperature and pressure range from 283 to 363 K and 0.1 to 95 MPa. These were modeled using EoS based on statistical mechanics, PC-SAFT and soft-SAFT. The ILs analyzed in this work show a high capacity for the physical absorption of CO2. The compound with the highest absorption capacity is [DEEA][Prop]│1.5:1 with a solubility value of xCO2=0.10 and molality mCO2=0.49 molCO2ꞏkgIL-1 at 0.5 MPa and 303 K. The density and derived properties, namely isothermal compressibility and isobaric thermal expansion, were modeled using PC-SAFT and soft-SAFT EoS. The EoS PC-SAFT demonstrated difficulty in describing the experimental data, with the association volume parameter very close to zero, which has no physical significance, since the compounds have functional groups that interact with each other. soft-SAFT provides a better description of the experimental data, with parameters with valid physical meaning. According to the results obtained in this work, further studies of thermophysical characterization of different ionic liquids are necessary to create a solid database that allows its application at an industrial level.