Novel Method for Characterization of Gas Separation Membranes

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Separation processes are a major contributor to the total energy consumed in the world. Over 40,000 of the distillation columns currently in operation in the United States alone are responsible for 11% of the global energy usage. Implementation of less energy-intensive competitors of distillation could bring a huge reduction in the energy used for separation. ******Gas separation membranes are attractive because they do not require a thermal driving force and do not involve sorbents to separate mixtures. Since the 1980s they have become widely used in various industrial applications, competing with cryogenic distillation, absorption, and adsorption. Nevertheless their share in the global separation market remains rather insignificant. The main challenge that limits this technology is a tradeoff between permeability and selectivity of the membranes. Overcoming this challenge requires improvements in properties of membrane materials. Recent developments in thermally rearranged (TR) polymers and polymers of intrinsic microporosity (PIMs) have helped to push the tradeoff line up, but more progress is needed for gas separation membranes to increase their share of the global separation market. The key aspects in the development of membrane materials is the accurate characterization of their gas transport coefficients, such as diffusion, solubility and permeability coefficients. These transport coefficients are determined in a dynamic membrane gas permeation test, also referred to as a time-lag test.******The objective of this research is to develop a new method for characterization of gas separation membranes, which relies on accurate monitoring of pressure decay due to gas molecules entering the membrane at high pressure. Unlike the conventional method, which relies on monitoring of pressure rise due to gas molecules emerging from the membrane, the new method will allow to maintain a zero concentration of the gas at the permeate-side of the membrane during the entire test. The latter is the key assumption of the time-lag analysis, which is inherently violated in the current state-of-the-art testing systems. The new method, which will require building a new generation of membrane testing systems, will allow for the more accurate determination of gas transport properties in membranes, and the better understanding of transport mechanism taking place in membranes. Ultimately, the progress in these most fundamental aspects of gas separation membranes will help them to become more competitive in the already existing markets such as refinery gas purification, syngas ratio adjustment, acid gas purification, nitrogen enrichment and dehydration, as well as making them attractive in other applications including separation of nitrogen from natural gas and capture of carbon dioxide from flue gases.