Carbon Dioside Removal from Natural Gas Stream Using Polycarbonate Membrane

This report presents a research study on application of membrane system in removal carbon dioxide from natural gas stream which represented by methane in this project. The morphology of asymmetric membrane is very important factor in orderto produce membrane with desirable properties that able to remove carbon dioxide from natural gas stream. The objectives of this research study 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. Dry/wet phase inversion technique was used to fabricate asymmetric PC membranes. The effect of solvent-non-solvent pair on membrane morphologies and separation characteristic were investigated. The chemical used are dichloromethane (DCM) as more volatile solvent while methanol (MeOH), ethanol (EtOH) and propanol (PrOH) were selected as non-solvents. In addition, methanol (MeOH) and tetrahydrofiiran (THF) were used as coagulant and less volatile solvent, respectively. Based on the literatures studied, the propanol and butanol-based membranes showed promising performance. Fourier Transform Infrared (FTIR) Spectroscopy is used for analyzing organic materials in order to obtain specific information about the chemical bonding and also the molecular structures of the membrane. Scanning electron microscopy (SEM) is used to observe the membrane morphologies. Gas permeation unit was used to evaluate the performance of membrane. Experimental results showed that high boiling point ofPrOHwas responsible in forming highly porous substructure with macrovoid formation in the DCMbased membranes prepared using PrOH as non-solvent. The performance of asymmetric PC membranes was evaluated by measuring CO2and CH4permeances as well as CO2/CH4 ideal selectivity. The results showed that CO2 and CH4 were strongly dependent upon membrane morphologies formed during fabrication. A highly porous membrane prepared from DCMPrOH and was found to give higher C02 and CH4permeance (C02:182 GPU; CH^Ml GPU) as compared to MeOH (COz:149 GPU; CH4:104 GPU) and EtOH (C02:165 GPU; CH4:129 GPU) membranes. In term of selectivity, the highest CO2/CH4 ideal selectivity of the fabricated asymmetric PC membrane is approximately 1.54. In conclusion, asymmetric PC membranes show promising performance and have high potential to be used for CO2/CH4 separation