Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/17141
Title: Polymeric-based membranes for hydrogen enrichment and natural gas sweetening
Authors: LOW BEE TING
Keywords: Polymer, membranes, hydrogen, natural gas, chemical modification
Issue Date: 30-Sep-2009
Source: LOW BEE TING (2009-09-30). Polymeric-based membranes for hydrogen enrichment and natural gas sweetening. ScholarBank@NUS Repository.
Abstract: The volatile and escalating oil prices, combined with concerns about the environmental consequences of anthropogenic carbon dioxide emissions, have led to the growing interest in the development of alternative energy sources. The world energy consumption continues to be at the core of the climate change debate and the use of natural gas and hydrogen is recommended to alleviate global warming. Membrane technology is a promising purification technique for hydrogen enrichment (i.e. H2/CO2 separation) and natural gas sweetening (i.e. CO2/CH4 separation). Polymeric membranes remain as the most viable commercial choice and substantial research works on the design of polymers with improved gas separation performance and physicochemical properties are in progress. Various approaches have been utilized by membrane scientists to overcome the bottlenecks and to achieve this goal. Due to the undesirable coupling of high H2 diffusivity and CO2 solubility, it is an exceptionally challenging task to separate H2 and CO2 by polymeric membranes. Majority of the polymers display inferior H2/CO2 selectivity and the current state of the art remains inadequate for industrial applications. For CO2/CH4 separation, polymers with good CO2/CH4 selectivity and CO2 permeability are available. Hence, greater emphasis must be placed on strategies to suppress CO2-induced plasticization. In this study, the diamine modification of polyimide dense membranes is investigated for enhancing the intrinsic H2/CO2 selectivity. The critical parameters that determine the effectiveness of the modification approach are comprehensively examined. Commercially, asymmetric hollow fiber membranes are of greater significance compared to dense films. Therefore, the fabrication of polyimide/polyethersulfone dual-layer hollow fiber membranes and the post-treatment with an aliphatic diamine are studied for H2/CO2 separation. A synthetic approach that involves the in-situ preparation of a pseudo interpenetrating polymer network (IPN) comprising of an azido-containing monomer and a polyimide is explored. The CO2/CH4 separation performance and the CO2-plasticization behavior of the pseudo-IPNs are evaluated. In summary, polymeric membranes with enhanced H2/CO2 selectivity via the diamine modification of polyimides have been developed. The chemistry and key parameters to optimize the diamine modification approach are identified and established. This modification technique is demonstrated on asymmetric hollow fiber membranes which are of greater commercial importance. In addition, polyimide/azide pseudo-interpenetrating polymer networks with promising CO2/CH4 separation performance and enhanced anti-plasticization properties against CO2 are discovered. The applicability of polymeric membranes for hydrogen enrichment and natural gas sweetening are evident. This motivates one to work towards the realization of membrane technology for clean energy applications.
URI: http://scholarbank.nus.edu.sg/handle/10635/17141
Appears in Collections:Ph.D Theses (Open)

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