Electrolysis: processes – compositions used therein – and methods – Electrolytic synthesis – Preparing inorganic compound
Reexamination Certificate
1999-10-20
2001-10-02
Wong, Edna (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic synthesis
Preparing inorganic compound
Reexamination Certificate
active
06296754
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of reducing nitrous oxide and an electrolytic cell for use therein. More particularly, this invention relates to a method for nitrous oxide reduction by which the excess part of the nitrous oxide gas used as an anaesthetic gas in hospitals is efficiently and continuously decomposed with hydrogen atoms electrolytically generated on a cathode, and to an electrolytic cell for use in the method.
BACKGROUND OF THE INVENTION
Nitrous oxide is used as an anaesthetic gas in hospitals. However, if a doctor or nurse working in an operating room continuously inhales leaked nitrous oxide gas over a prolonged period, there is a fear that the doctor or nurse may have a health disorder. In addition, discharging the nitrous oxide gas ascends to the stratosphere, where it changes into nitrogen monoxide. The nitrogen monoxide reacts with ozone to form a substance which causes ozonosphere depletion like chlorofluorocarbon gases and the like. Furthermore, since nitrous oxide has a coefficient of global warming several hundred times that of carbon dioxide and the life thereof in the atmosphere is as long as about 150 years, it is a substance which exerts considerable influence on global warming. Inhibiting this harmful substance, nitrous oxide, from diffusing into the air is coming to be a future important need in hospitals, etc.
Although the leakage of nitrous oxide into an operating room is attributable to leakage from joints in the anaesthetic apparatus and to the excess discharge of the anaesthetic gas from the apparatus, it is mostly attributable to the latter. The currently employed measures for reducing the concentration of an anaesthetic gas in an operating room include (1) ventilating the room, (2) adsorptively removing the excess anaesthetic gas with activated carbon, (3) discharging the excess anaesthetic gas into the atmosphere with a suction type discharge apparatus, and (4) decomposing the excess anaesthetic gas with a decomposing apparatus after the gas is collected with a suction type discharge apparatus. Among these, method (
2
) has a drawback in that the amount of nitrous oxide gas adsorbable onto activated carbon is small, while method (
3
) has a drawback in that discharging the gas outside is undesirable from the standpoint of avoiding global warming. Consequently, method (
4
) is considered to be the best.
With respect to an apparatus for decomposing nitrous oxide gas, a technique is described in JP-B-1-45487 (the term “JP-B” as used herein means an “examined Japanese patent publication”), in which a catalyst comprising a silica powder having, deposited thereon, both nickel containing a platinum group metal and lanthanum oxide, is packed into a reactor and the gas to be decomposed is passed through the reactor heated at 150 to 550° C. to decompose the same. However, this technique is undesirable in that this treatment is known to yield nitrogen dioxide and nitrogen monoxide, as by-products, which are harmful to the human body and cause environmental pollution. Another drawback thereof is that since the catalyst deteriorates at a high rate under such high-temperature conditions, the catalyst needs to be replaced with a fresh one in a short time period and periodic maintenance is necessary. Furthermore, it is extremely difficult to regenerate the deteriorated catalyst, so that the expense of discarding the catalyst cannot be avoided.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a method for continuously and easily converting nitrous oxide stably over a long period of time into substances harmless to the human body and the environment.
Another object of the present invention is to provide an apparatus for practicing the above method.
The present invention solves the above-described problems by providing:
(1) A method of reducing nitrous oxide which comprises introducing nitrous oxide into a reaction chamber disposed in contact with an electrolytic chamber having an anode and a cathode comprising a hydrogen-absorbing material, said cathode serving as a diaphragm separating said reaction chamber and said electrolytic chamber, and contacting the nitrous oxide with said diaphragm to thereby continuously reduce the nitrous oxide with hydrogen atoms electrolytically generated on the cathode, absorbed by said hydrogen-absorbing material and passing through said diaphragm.
(2) The method of reducing nitrous oxide as described in (1) above, wherein the cathode comprises a material selected from the group consisting of palladium, palladium alloys and hydrogen-absorbing nickel alloys.
(3) The method of reducing nitrous oxide as described in (2) above, wherein the cathode has a catalyst comprising a platinum group metal black deposited on the side of the cathode opposite the anode.
(4) An electrolytic cell for the reduction of nitrous oxide partitioned into an electrolytic chamber having an anode and a reduction reaction chamber, said diaphragm comprising a hydrogen-absorbing material, and the side of the diaphragm facing the electrolytic chamber serving as a cathode.
REFERENCES:
Otsuka et al., “Reduction of Nitrous Oxide by Electrochemically Generated Spillover Hydrogen”, Stud. Surf. Sci. Catal., vol. 77 (New Aspects of Spillover Effect in Catalysis), pp. 117-123. 1993 (no month available), Abstracts only.*
Furuya et al., “Electroreduction of Nitrous Oxide to Nitrogen Using a Gas-Diffusion Electrode Loaded With Various Catalysts”, Proc. —Electrochem. Soc., 93-18 (Proceedings of the Symposium on Environmental Aspects of Electrochemistry and Photoelectrochemi, 1993, no month available.*
Inoue Hiroshi
Iwakura Chiaki
Nakamatsu Shuji
Nishiki Yoshinori
Ogata Setsuro
Kabushiki Kaisha Maruzen Create
Sughrue Mion Zinn Macpeak & Seas, PLLC
Wong Edna
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