CO2 Capture from Natural and Flue Gases Using Polymeric Membranes

Abstract

Carbon dioxide (CO2) capture from the environment or other gas mixtures is extremely imperative to reduce the global warming. CO2 gas is acidic in nature and can adversely affect the earth atmosphere by enhancing its temperature. The drastic weather changes are observed with annual increment in concentration of CO2. In Pakistan, for last decades, people are suffering from floods, severe cold and drought. Therefore, to control the CO2 concentration in atmosphere and to enhance the efficiency of fuel, it is important to capture CO2 as much as possible. For the last three decades, membrane technology is considered better option to capture CO2 because membrane processes consume low energy and are economical. Recently, the polymeric membranes are attaining attention. In this work, it was planned to investigate the CO2 capture from natural and flue gases by using pure and modified cellulose acetate (CA) membranes. In first section, the novel calix[4]arene organic molecule was blended with cellulose acetate to fabricate polymer –organic material blended membrane to capture CO2 gas. The two different derivatives of calix named as 5,11,17,23-tetrakis(Nmorpholinomethyl)-25,26,27,28-tetrahydroxycalix[4]arene (CL) and 5,11,17,23- Tetratert-butyl-25,27-bis-(2-piprazinoethyl)-26-dihydroxycalix[4]arene were synthesized, blended with cellulose acetate polymer and studied for carbon dioxide (CO2) , nitrogen (N2) gas permeation and selectivity. The results showed that calix[4]arene has higher capability to permeate N2 gas than CO2 gas. Therefore, calix blended membranes have high permeability of N2 gas as compared to CO2 gas. In the last step, silica (Si) and silica functionalized with p tetranitrocalix[4]arene (Si-CL) was incorporated into the CA matrix to achieve better N2/CO2 gas selectivity. In second section, the titanium dioxide (TiO2) nano particles were used to synthesize polymer – inorganic material blended membrane to capture CO2 from methane gas. These TiO2 nanoparticles were then functionalised with amine, to study their effects on above mentioned gas separation. The results revealed that CA-TiO2 blended membrane can separate CO2/CH4 gas better than CA- functionalised TiO2 membrane. The separation of CO2 by a membrane is not just a process to physically sieve out CO2 gas through the controlled membrane pore size, it mainly depends upon diffusion and solubility of gases, particularly for composite membranes. The blended components in composite membranes have a high capability to adsorb CO2. Therefore, adsorption studies of CA and CA-inorganic blended membranes were also done. According to this work, CO2 gas adsorption phenomena takes active part in gas permeation process.