HYDROGEN SEPARATION MEMBRANES

MEMBRANE-BASED GAS SEPARATIONS ARE ATTRACTIVE BECAUSE OF THEIR INHERENT ENERGY EFFICIENCY AND LOW OPERATING COSTS. HOWEVER, METHODS CURRENTLY AVAILABLE FOR HYDROGEN SEPARATIONS ARE COSTLY AND INEFFICIENT. POLYMERIC MEMBRANESNOW IN USE ARE CAPABLE OF ONLY LIMITED SELECTIVITY, WHICH LEAVES SUBSTANTIAL AMOUNTS OF IMPURITIES IN THE HYDROGEN STREAM. THOSE MEMBRANES ARE ALSO HEAT-SENSITIVE; CONSEQUENTLY, MANY HYDROGEN-CONTAINING FEED STREAMS MUST BE COOLED BEFORE PROCESSING. METAL MEMBRANES OVERCOME MOST OF THESE PROBLEMS BY BEING HIGHLY SELECTIVE AND RESISTANT TO TEMPERATURES OF UP TO 500 DEGREE CELLCIUS. HOWEVER, CURRENT METALLIC HYDROGEN-SEPARATION MEMBRANES HAVE AN EXTREMELY HIGH CAPITAL COST, AS THEY ARE COMPOSED OF PALLADIUM ALLOYED WITHSILVER. IN THIS PROGRAM, BEND RESEARCH, INC. WILL EXAMINE THE TECHNICAL FEASIBILITY OF REPLACING THIS COSTLY MATERIAL WITHA TITANIUM ALLOY THAT IS HIGHLY PERMEABLE TO HYDROGEN. IN ORDER TO PREVENT OXIDES FROM FORMING ON THE SURFACE OF THE ALLOY AND THUS IMPEDING HYDROGEN TRANSPORT, ALLOY FILMS WILLBE CLEANED AND THEN COATED WITH A THIN LAYER ( 1 ) OF A NON-OXIDIZING METAL SUCH AS PALLADIUM OR NICKEL. SUCH MEMBRANES SHOULD IN PRINCIPLE BE MORE THAN THIRTY TIMES AS PERMEABLE TO HYDROGEN AND LESS THAN ONE-SEVENTH AS COSTLY AS PALLADIUM-SILVER MEMBRANES. DURING PHASE I, TECHNIQUES WILL BE DEVELOPED FOR CLEANING AND COATING THE ALLOY FILMS. THESE COATED-ALLOY MEMBRANES WILL THEN BE TESTED FOR HYDROGEN PERMEATION RATES AND SELECTIVITY USING FEED-STREAM COMPOSITIONS AND TEMPERATURES LIKELY TO BE FOUND IN ACTUAL FEED STREAMS. USING THESE RESULTS, THE RESEARCHERS WILL EVALUATE THE TECHNICAL AND ECONOMIC FEASIBILITY OF UTILIZING COATED-ALLOYMEMBRANES FOR IMPROVED HYDROGEN SEPARATIONS.