Abstract Hydrogen and oxygen gases are safely recombined in the presence of a catalytic device which operates in two stages in a secondary battery system. Recombination continues in a controlled manner while the battery is on discharge and charge for periods corresponding to the normal life of a conventional secondary battery. In sealed secondary battery systems hydrogen and oxygen gases evolved during operation of the battery are releasably contained through a range of pressures during which long-term stoichiometric recombination of the gases takes place. The catalytic device in a preferred form comprises a foraminous body which includes exposed catalytic surfaces of relatively low gas recombining capacity and an inner nucleus of enclosed catalytic material. The nucleus comprises enclosed catalytic surfaces on which gases passing through the formaminous body react initially within a thermally favorable environment whereby cumulative heating can take place. A resulting build-up of heat at the nucleus is released to raise the temperature of the exposed catalytic surfaces to temperatures at which gases coming into contact with the exposed catalytic surfaces will start to recombine thereon, and continue to react in a sustained manner within a limited temperature range. When, as may occur, the exposed catalyst surfaces are subjected to increasing gas pressure in the battery they become self-limiting in the extent to which their temperature may be raised by exothermic reaction. Thus the rate of recombination of gases at catalyst surfaces is controlled and limited to positively prevent the exposed catalyst surfaces from reaching temperatures at which an explosion may take place, i.e., temperatures found to be within upper limits of from about 400* C up to about 600* C, and the range of control may be extended downwardly to values as low as 250*C for some battery operations. Water resulting from the controlled recombination at the catalyst surface is returned to the electrolyte with catalyst surfaces being maintained in a constantly reactive condition.
A SELF-LIMITING COMPOSITE CATALYST DEVICE FOR RECOMBINING HYDROGEN AND OXYGEN WITH EXOTHERMIC HEATING IN A SEALED BATTERY CHAMBER IN WHICH HYDROGEN AND OXYGEN ARE EVOLVED AND EXERT INCREASED PRESSURE, SAID CATALYST DEVICE INCLUDING A NUCLEUS OF ENCLOSED CATALYST CONSISTING IN A CATALYST-SUPPORTING BODY OF ALUMINA AND A CATALYST METAL OF PALLADIUM HAVING A RELATIVELY HIGH-LEVEL GAS-RECOMBINING CAPABILITY CONTAINED ON THE CATALYST-SUPPORTING BODY, AND A FORAMINOUS OUTER CYLINDRICAL ENCLOSURE MEMBER WHICH DEFINES AN ENCLOSED SPACE IN WHICH GASES MAY BE RECEIVED AND HELD IN CONTACT WITH THE NUCLEUS, SAID ENCLOSURE MEMBER HAVING EXPOSED SURFACES OF RELATIVELY LOW-LEVEL GAS-RECOMBINING CAPABILITY THROUGH WHICH HYDROGEN AND OXYGEN GASES MAY PASS INTO CONTACT WITH THE NUCLEUS AND SAID EXPOSED SURFACES CONSISTING IN A CATALYST SUPPORTING MATERIAL HAVING CONTAINED THEREIN A QUANTITY OF CATALYST METAL CAPABLE OF UNDERGOING HEATING IN A RANGE OF EXOTHERMIC HEATING WHICH IS LIMITED IN RESPONSE TO INCREASE IN PRESSURE IN THE SEALED BATTERY CHAMBER AND WHICH LIES WITHIN LIMITS OF FROM 400*C TO 600*C, AND SAID QUANTITY OF CATALYTIC METAL IN THE EXPSED SURFACES OCCURRING IN AMOUNTS OF FROM ABOUT 0.01% UP TO 0.1% BY WEIGHT, AND SAID OUTER CATALYST SUPPORTING MATERIAL HAVING AN INTERNAL SURFACE AREA OCCURRING BETWEEN 0.3 SQUARE METERS PER GRAM UP TO A VALUE OF LESS THAN SQUARE METER PER GRAM, AND SAID CATALYST METAL OF RELATIVELY HIGH-LEVEL GAS-RECOMBINING CAPABILITY IN THE NUCLEUS OCCURRING IN A QUANTITY OF NOT LESS THAN 2% OF CATALYST METAL, AND SAID CATALYST SUPPORTING BODY IN THE NUCLEUS HAVING A SURFACE AREA OF MORE THAN 50 SQUARE METERS PER GRAM.
Claim 2
Dependent Claim
258 words
A SELF-LIMITING COMPOSITE CATALYST DEVICE FOR RECOMBINING HYDROGEN AND OXYGEN WITH EXOTHERMIC HEATING IN A SEALED BATTERY CHAMBER IN WHICH HYDROGEN AND OXYGEN ARE EVOLVED AND EXERT INCREASED PRESSURE, SAID CATALYST DEVICE INCLUDING A NUCLEUS OF ENCLOSED CATALYST CONSISTING IN A CATALYST-SUPPORTING BODY OF ALUMINA AND A CATALYST METAL OF PALLADIUM HAVING A RELATIVELY HIGH-LEVEL GAS-RECOMBINING CAPABILITY CONTAINED ON THE CATALYST-SUPPORTING BODY, AND A FORAMINOUS OUTER CYLINDRICAL ENCLOSURE MEMBER WHICH DEFINES AN ENCLOSED SPACE IN WHICH GASES MAY BE RECEIVED AND HELD IN CONTACT WITH THE NUCLEUS, SAID ENCLOSURE MEMBER HAVING EXPOSED SURFACES OF RELATIVELY LOW-LEVEL GAS-RECOMBINING CAPABILITY THROUGH WHICH HYDROGEN AND OXYGEN GASES MAY PASS INTO CONTACT WITH THE NUCLEUS AND SAID EXPOSED SURFACES CONSISTING IN A CATALYST SUPPORTING MATERIAL HAVING CONTAINED THEREIN A QUANTITY OF CATALYST METAL CAPABLE OF UNDERGOING HEATING IN A RANGE OF EXOTHERMIC HEATING WHICH IS LIMITED IN RESPONSE TO INCREASE IN PRESSURE IN THE SEALED BATTERY CHAMBER AND WHICH LIES WITHIN LIMITS OF FROM 400*C TO 600*C, AND SAID QUANTITY OF CATALYTIC METAL IN THE EXPSED SURFACES OCCURRING IN AMOUNTS OF FROM ABOUT 0.01% UP TO 0.1% BY WEIGHT, AND SAID OUTER CATALYST SUPPORTING MATERIAL HAVING AN INTERNAL SURFACE AREA OCCURRING BETWEEN 0.3 SQUARE METERS PER GRAM UP TO A VALUE OF LESS THAN SQUARE METER PER GRAM, AND SAID CATALYST METAL OF RELATIVELY HIGH-LEVEL GAS-RECOMBINING CAPABILITY IN THE NUCLEUS OCCURRING IN A QUANTITY OF NOT LESS THAN 2% OF CATALYST METAL, AND SAID CATALYST SUPPORTING BODY IN THE NUCLEUS HAVING A SURFACE AREA OF MORE THAN 50 SQUARE METERS PER GRAM.