PROCESS AND COMPOSITION FOR SEPARATION OF OXYGEN FROM AIR USING PR-CE OXIDES AS THE CARRIER

摘要

1489224 Oxygen separation UNION CARBIDE CORP 24 Oct 1974 [25 Oct 1973] 45984/74 Heading ClA Oxygen is separated from an O 2 containing gas mixture by oxidizing a Pr-Ce oxide mixture present in a "first oxidized state" by reacting with the gas mixture to convert at least a portion of the reaction mass into a relatively more "oxidized state" followed by separation of the O 2 depleted gas mixture from the relatively more oxidized Pr-Ce oxide reaction mass and then dissociating at least a portion of the oxidized mass to a relatively more reduced state of Pr-Ce oxide with liberation of O 2 ; the Pr-Ce oxide mixture and O 2 are then separated. The reaction masses may have the general formula (Pr x Ce y )O z where x and y are the relative molar amounts of cations in the oxide materials and x + y = 1 and z varies from 1À5 to 2À0; at values of z = 2À0 the materials are in their fully oxidized state while at z = 1À5 they are at their lower limit of dissociation. The Pr-Ce oxide mixture may contain a surface dopant, e.g. Ag, which increases the resistance of the oxide material to the effects of CO 2 and H 2 O which may be present in the gas mixture. A Pr-Ce oxide reaction mass of general formula (Pr x Ce y )O z , containing a dopant, preferably silver, is synthesized by contacting an aqueous solution comprising the nitrate salts of Pr, Ce and dopant with excess precipitating agent with respect to the molar amount of Pr and Ce in the aqueous starting solution; the precipitated material is separated from the aqueous solution, dried and then calcined at 600-1000‹ C. to form the mixed oxide; the precipitating agent is selected from the group ammonium oxalate or hydroxide or oxalic acid.