ИСТИНА

Development of new high-efficiency techniques for hydrogen separation and purification is one of the key areas in hydrogen energy. Membrane is of particular attractiveness for this purpose because of its simplicity and efficiency, easy combination with other methods. Conventional polymeric and palladium-based membranes have a number of serious shortcomings related to the low selectivity of the first, high cost and limited service life of the second. An alternative approach consists in development of composite membrane materials based on dispersed hydride-forming intermetallic compounds and polymer binder [1]. Herein, we report the experimental results on synthesis and testing of metal-polymer composites specially designed for hydrogen separation processe within the general concept of mixed matrix membranes (MMM). The main aspects considered in the work are the following: - selection of hydride-forming intermetallic compounds suitable for membrane technology. AB5-type alloys were employed thanks to their easy activation and low sensibility to impurity gases. In order to adjust the metal hydride component to operating parameters of the membranes, alloying of the base LaNi5 composition with Al, Co, Mn, Cu and Ce was performed. The effects of the substituents and the alloys processing mode (e.g. ball milling) on pressure-composition diagrams at various temperatures, pressure hysteresis and volume expansion at different hydrogen content were evaluated; - selection of polymer binders. Basic requirement for these components relate to good conjunction with metal hydride fillers, ability to withstand the alternating volume effects accompanying the hydrogen interaction with the metal particles, and limited permeability low permeability to impurity gases. Polyethylene and polysulfone were chosen as the most satisfying to these conditions; - membrane formation techniques. Conventional polymer membrane formation method based on phase inversion from the polymer solution with subsequent phase inversion was unsuitable for this type of materials. It does not provide steady interfacing between metallic particles and polymer matrix: the cyclic hydrogen absorption/desorption leads to the formation of the interface defects. These defects act as a bypass for all components of the gas mixture to be separated that results in the reduced selectivity of the membrane. In contrast, ball milling pre-treatment ensures optimal polymer-filler adhesion. The composites produced in such a way retained their reactivity with respect to hydrogen, prevent the pulverization of the metal hydride and demonstrate the resistance to surface poisoning; - gas transport measurements were carried out by barometric method at pressures up to 1.5 bars. The permeability of hydrogen and the most common impurity gases, including nitrogen, methane, carbon dioxide, were evaluated. It was shown that the ideal selectivity with respect to hydrogen increased 50-150 times for the composite film membranes as compared to individual polymer. It is concluded that the incorporation of hydride-forming intermetallic compounds into a polymer matrix is a promising approach to increasing the hydrogen separation performance of membrane materials