Analysis of CO2/CH4 gas permeation of gamma-cyclodextrin based polymeric mixed matrix membrane

Abstract

In today’s world, energy crisis is a prevalent problem and to overcome this, carbon dioxide must be separated from fuel gases to improve the energy content of the fuel. This can be achieved by employing either conventional or un-conventional processes. In this thesis, separation is being done by using polymeric membranes and better results were achieved in terms of permeability and selectivity of CO2 and CH4. For this purpose, it is proposed to use mixed matrix membrane, which consists of Gamma-cyclodextrin-metal organic frame work (γ-CD-MOF) incorporated into two polymers mainly: polyurethane and cellulose acetate. γ-CD-MOF is classified under the category of green mof synthesized from potassium hydroxide (KOH) and cyclodextrin from starch by employing vapordiffusion method. Having body centered cubic structure with cavity diameter 7.8A and spherical voids of 17A. γ-CD-MOF gained significant attention for being used as gas adsorbent material. Therefore, it is recommended to be used as filler in polymeric membrane for fabrication of mixed matrix membrane. Hence, CA/ γ-CD-MOF and PU/γCD-MOF mixed matrix membrane were synthesized from solution casting method and characterized by using SEM analysis, FTIR spectroscopy, XRD analysis and ultimate tensile testing In this thesis γ-CD-MOF is being incorporated into cellulose acetate and polyurethane and fabricate. These membranes undergo different characterization techniques i.e. SEM analysis, FTIR, XRD and ultimate tensile testing. These two membranes were then tested for gas permeation using single and mixed gas permeation testing of carbon dioxide and methane using gas chromatogram. It was found that CA/γCD-MOF membrane gave CO2/CH4 selectivity up to 39 but with low permeability of CO2. While, CO2/CH4 selectivity achieved up to 29 and permeability maximum of 214 barrer of CO2 in PU/γ-CD-MOF membranes. Both membranes possess highly dense surface morphology and no voids or cavities have been seen even at magnification of 20000x in SEM images. These features endorse solution-diffusion mechanism for the transport of gases through these dense membranes. After studying these two types of membranes, it was concluded that CA/γ-CD-MOF membrane employed where only focus in on high selectivity of carbon dioxide. To achieve better selectivity along with high permeability of carbon dioxide PU/γ-CD-MOF membrane is most suitable candidates for gas separation.