Development of Asymmetric Polycarbonate (PC) Membrane for Carbon Dioxide Removal from Methane

• Main Author: Iqbal, Muhammad
• Format: Thesis
• Language: English
• Published: 2007
• Subjects: TP Chemical technology
• Online Access: http://utpedia.utp.edu.my/9695/1/2007%20Master%20-%20Development%20Of%20Asymmetric%20Polycarbonate%20%28PC%29%20Membrane%20For%20Carbon%20Dioxide%20Removal%20Fr.pdf; http://utpedia.utp.edu.my/9695/

The morphology of asymmetric membrane strongly influences the performance of membrane in removing C02 from CH4. The understanding of mechanism of asymmetric membrane formation is very crucial in order to produce desirable morphology that leads to enhancement of the membrane performance. The objectives of this work are to study the effect of various preparation conditions on the morphologies of asymmetric polycarbonate (PC) membrane and its relation to CO2/CH4 separation characteristic. Asymmetric PC membranes were fabricated using dry/wet phase inversion technique. The effects of solvent - non-solvent pair, non-solvent concentration, evaporation time and composition of water-MeOH mixtures in coagulation bath on membrane morphologies were investigated. The mechanism of membrane morphologies formation was explained using solvent and non-solvent evaporation, solubility parameter and coagulation value. Dichloromethane (DCM) and chloroform were selected as more volatile solvents while ethanol (EtOH), propanol (PrOH) and butanol (BuOH) were used as non-solvents. In addition, methanol (MeOH) and 1,1,2 trichlorethane (TEC) were used as the coagulant and less volatile solvent, respectively. Membrane characterization was carried out by using SEM and DMA. Gas permeation unitwasusedto evaluate the performance of membrane. Experimental results showed that high boiling point of BuOH was responsible in forming highly porous substructure with macrovoid formation in the DCM and chloroform-based membranes prepared using BuOH as non-solvent. Increasing BuOH concentration from 0 to 10 wt.% in DCMcasting solution produced macrovoids and a more porous substructure. This is due to smaller coagulation value and solubility parameter difference between solvent mixtures and MeOH. hi addition, by increasing the evaporation time for casting film from 0 to 60 seconds, and water content from 0 vol.% to 30 vol.% in MeOH coagulation bath, less porous and macrovoid-free substructure were obtained. This is due to thicker skin layer formation and larger solubility parameter difference between solvent mixtures and MeOH, respectively. The performance of asymmetric PC membranes was evaluated bymeasuring C02 and CH4 permeances as well as C02/CH4 ideal selectivity. The results showed that C02 and CH4 were strongly dependent upon membrane morphologies formed during fabrication. Highly porous membranes prepared from DCM-BuOH and chloroform- BuOH pairs were found to give higher C02 and CH4 permeance as compared to EtOH and PrOH membranes. Increasing the BuOH concentration from 0% to 10 wt.% of casting solution would increase the C02 and CH4 permeances as a result from highly porous substructure and the existence of macrovoids. Lower C02 and CH4 permeances obtained on asymmetric PC membranes prepared from the effect of longer evaporation time of casting film and from the effect of higher water concentration in MeOH coagulation bath were due to less porous substructure formation. In term of selectivity, the highest C02/CH4 ideal selectivity of the fabricated asymmetric PC membrane is approximately 175. These results demonstrated significant improvement in C02/CH4 separation as compared to other membranes reported by previous researchers. In conclusion, asymmetric PC membranes produced in this work show promising performance and have high potential to be used for C02/CH4 separation.