JPS6150650B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for treating laughing gas in surplus anesthetic gas.

It has been revealed that inhaling anesthetic gas leaked into an operating room for a long period of time can cause health problems for doctors and nurses working in the operating room. Therefore, the US National Institute for Occupational
Safety and Health (NIOSH) recommends that the concentration of leaked anesthetic gas in the operating room be kept below 25 ppm of laughing gas and 0.5 ppm of halothane. Due to this situation, measures to prevent anesthetic gas contamination in operating rooms have recently attracted attention, and a small number of hospitals are beginning to install devices to remove excess anesthetic gas. This discharge device is a device that uses a pump to suck in excess anesthetic gas, which is exhaled air from a patient, and discharges it directly to the outdoors. Although the use of this evacuation device is certainly effective in reducing the concentration of anesthetic gas in the operating room, on the other hand, it may spread anesthetic gas contamination to the surrounding area of the hospital, resulting in secondary pollution. Therefore, when exhausting excess anesthetic gas using an exhaust device, it is necessary to remove or detoxify the anesthetic gas contained therein as much as possible, rather than exhausting it as is. The anesthetic gases mainly used in operating rooms are laughing gas (nitrous oxide, N ₂ O) and halothane (1,1,1-trifluoro-2-bromo-2-chloroethane).
Since anesthetic gases other than laughing gas such as halothane are well adsorbed by activated carbon, they can be adsorbed and removed relatively easily by incorporating an activated carbon canister into the surplus anesthetic gas discharge device. On the other hand, there is currently no known practical method for removing laughing gas. Therefore, the current situation is that the laughing gas in the surplus anesthetic gas has no choice but to be discharged outdoors.

In order to detoxify laughing gas in surplus anesthetic gas, the present inventors have investigated decomposition using a catalyst. The inventors of the present invention have already recognized that the catalyst containing the metal of white metal thread as a component has high catalytic activity, and the amount of by-products of nitrogen dioxide and nitrogen monoxide is extremely small, and has previously filed a patent application. There (patent application 1973-105739)
issue). However, this catalyst was found to have the drawback of being slightly susceptible to poisoning by halothane. In addition, it has been recognized that catalysts using metal oxides such as cupric oxide and chromium oxide alone are effective as catalysts for decomposing laughing gas, and a patent application has already been filed (Japanese Patent Application No.
No. 128235). However, although the catalyst containing cupric oxide as a component has a high catalytic activity, it produces a rather large amount of nitrogen dioxide and nitrogen monoxide as by-products, and has a tendency to be easily poisoned by halothane. In addition, catalysts containing chromium oxide produce a small amount of nitrogen dioxide and nitrogen monoxide as by-products, and have a certain level of catalytic activity.
There were some areas where the catalyst activity was insufficient.

Based on the above results, the present inventors conducted studies in order to obtain an even more excellent catalyst. That is, we sought a catalyst for decomposing laughing gas that satisfies the following requirements.

(a) Has high catalytic activity and can decompose laughing gas into nitrogen and oxygen at low temperatures. (b) When laughing gas is decomposed into nitrogen and oxygen, the amount of harmful by-products such as nitrogen dioxide and nitric oxide produced is small. (c) It is less likely to be poisoned by anesthetics such as halothane, which are halogenated hydrocarbon compounds that are often used together with laughing gas. (d) Good heat resistance and long catalyst life. (e)
It must be cheap.

As a result, they discovered that a catalyst containing a mixture of cupric oxide and chromium oxide has high catalytic activity, produces less nitrogen dioxide and nitrogen monoxide byproducts, and is less likely to be poisoned by halothane. Reached. That is, the present invention (1) brings laughing gas in surplus anesthetic gas into contact with a catalyst mainly composed of a mixture of cupric oxide and chromium oxide at a temperature of 250 to 650°C, and converts the laughing gas into nitrogen and oxygen. (2) A method for treating laughing gas in surplus anesthetic gas, which is characterized by decomposing laughing gas into 250 ~ This is a device for processing laughing gas in surplus anesthetic gas, which consists of a reactor for decomposing it into nitrogen and oxygen at 650℃. Furthermore, the inventors
A catalyst comprising a mixture of cupric oxide and chromium oxide to which at least one of the group consisting of ferric oxide, nickel oxide, cobalt oxide, and manganese dioxide is added, especially cupric oxide and chromium oxide. The catalyst, which consists of a mixture of manganese dioxide, has high catalytic activity, produces a small amount of nitrogen dioxide and nitrogen monoxide as by-products, is less likely to be poisoned by halothane, and has excellent heat resistance. It was found that it is optimal as a gas decomposition catalyst.

The catalyst used in the present invention is a mixture of cupric oxide and chromium oxide, and the mixing ratio is 0.1 to 10 (weight ratio) of chromium oxide to 1 cup of cupric oxide, more preferably 0.2 to 5. It is preferable that it is in the range of . If the mixing ratio is 0.1 or more, the amount of by-products of nitrogen dioxide and nitrogen monoxide tends to increase, making it easier to be poisoned by halothane. On the other hand, if the mixing ratio is 10 or more, the catalyst activity tends to decrease. Furthermore, the component selected from the group consisting of ferric oxide, nickel oxide, cobalt oxide, and manganese dioxide, which is added to the mixture of cupric oxide and chromium oxide, is added to the mixture of cupric oxide and chromium oxide. 0.05-20 for 1 cupric oxide in
(More preferably, it is in the range of 0.2 to 5). Being within this range is effective in reducing poisoning by nitrogen dioxide, nitrogen monoxide by-products, and halothane.

One or more components from the above group are added to the mixture of cupric oxide and chromium oxide,
Among these, manganese dioxide is preferred. The catalyst of the present invention is used by molding the above oxide as it is or by supporting it on a carrier. Examples of the carrier include alumina, silica, and titania. The amount of catalyst components supported on the carrier is determined for each oxide component.
It is 0.1 to 30% by weight, particularly preferably 1 to 30% by weight.

In the present invention, the excess anesthetic gas is heated to a temperature of 250 to 650°C.
Therefore, it is necessary to contact the catalyst for 0.2 seconds or more. At temperatures above 250°C, it is difficult to sufficiently decompose laughing gas into nitrogen and oxygen, and it is not desirable from a safety standpoint to use high temperatures above 650°C in facilities such as hospitals.

Next, the processing device of the present invention will be explained. FIG. 1 schematically shows a processing apparatus of the present invention. Excess anesthetic gas discharged from the pop-off valve of the anesthesia machine is sucked together with air by a surplus anesthetic gas exhaust device. Reactor 1 where this mixture of excess anesthetic gas and air is heated to 250-650℃
The laughing gas contained therein is decomposed into nitrogen and oxygen.

The reactor used in the apparatus of the present invention is made of a material that can withstand the operating temperature of the reactor, and is filled with the above-mentioned catalyst, and the contact time between the introduced gas and the catalyst is
The shape, size, etc. are selected and manufactured as appropriate so that the time is 0.2 seconds or more. In particular, a reactor in which a stainless steel tube or the like is filled with a catalyst supported on a granular carrier can be preferably used. Further, in the processing apparatus of the present invention, as shown in FIG. 1, a preheater 3 can be placed at the front of the reactor to preheat the gas entering the reactor. Furthermore, in the processing apparatus of the present invention, as shown in FIG. 1, in order to utilize energy effectively, heat exchange is performed between the high temperature gas discharged from the reactor and the gas introduced into the reactor. The heat exchanger 4 can be placed so that the Furthermore, in the processing apparatus of the present invention, the blower 2 can be installed to dilute and cool the high temperature gas discharged from the reactor with air.

In addition, in the present invention, although a catalyst that is not easily poisoned by halothane is used, in order to prevent deterioration of the catalyst due to halothane, an activated carbon canister for adsorbing and removing halothane is incorporated into the surplus anesthetic gas discharge device. It is desirable to reduce the amount of halothane contained in the gas introduced into the processing equipment as much as possible.

The present invention will be explained below with reference to Examples.

Example 1 Granular alumina carrier (Neobead CB manufactured by Mizusawa Chemical Co., Ltd., baked at 900°C for 3 hours)
The sample was impregnated with a mixed aqueous solution of copper nitrate and chromium nitrate in an amount of 5% by weight of the cupric oxide and 5% by weight of the chromium oxide based on the carrier, and after drying, it was impregnated with a mixed aqueous solution of 5% by weight of the carrier at 600°C. The nitrates were converted into oxides by heating for a period of time to obtain a catalyst in which 5% by weight of cupric oxide and 5% by weight of chromium oxide were supported on the carrier. This catalyst was filled in a stainless steel tube with an inner diameter of 1.5 cm to a length of 10 cm to form a reactor. This reactor is placed in an electric furnace and heated to 500℃, and a mixture of laughing gas and oxygen (laughing gas: oxygen = 50:50 volume %), which is a component of surplus anesthetic gas, is heated to 500℃ in a preheater. After that, the flow was conducted from the inlet of the reactor at 50 ml/min. The gas coming out from the outlet of the reactor was collected and the concentration of laughing gas was measured by gas chromatography, and it was found to be 0% by volume. Therefore, the decomposition rate of laughing gas was 100°C. Furthermore, the total concentration of nitrogen dioxide and nitrogen monoxide contained in the gas coming out from the outlet of the reactor at this time was 32 ppm.

Example 2 A catalyst in which 13% by weight of nickel oxide, 7% by weight of cupric oxide, and 2% by weight of chromium oxide were supported on a granular alumina carrier was obtained by the same operation as in Example 1. This catalyst was filled in a stainless steel tube to form a reactor in the same manner as in Example 1, and this reactor was heated to 480°C, and the same mixed gas of laughing gas and oxygen as in Example 1 was heated to 480°C in a preheater. , Example 1
It was communicated from the inlet of the reactor in the same way. At this time, the decomposition rate of laughing gas was 100%, and the total concentration of nitrogen dioxide and nitrogen monoxide contained in the gas coming out of the reactor outlet was 5 ppm. Additionally, when 750mg of halothane was added as vapor to the mixed gas of laughing gas and oxygen during the above reaction, the decomposition rate of laughing gas was only 100%.
% to 97%. As described above, this catalyst had high catalytic activity, produced small amounts of nitrogen dioxide and nitrogen monoxide, and was not easily poisoned by halothane.

Comparative Example By the same operation as in Example 1, a catalyst was obtained in which 10% by weight of cupric oxide was supported on a granular alumina carrier. This catalyst was packed into a stainless steel tube as in Example 1 to form a reactor.
The reactor was heated to 490°C, and the same mixed gas of laughing gas and oxygen as in Example 1 was heated to 490°C in a preheater and passed through the inlet of the reactor as in Example 1. At this time, the decomposition rate of laughing gas was 100%, but the total concentration of nitrogen dioxide and nitrogen monoxide contained in the gas coming out of the reactor outlet was as high as 100 ppm.

Example 3 By the same operation as in Example 1, 6% by weight of cupric oxide, 6% by weight of chromium oxide, and 1% by weight of manganese dioxide were added to a granular alumina carrier based on the carrier.
A supported catalyst was obtained. This catalyst was filled into a stainless steel tube to form a reactor in the same manner as in Example 1, and this reactor was heated to 480°C, and the same mixed gas of laughing gas and oxygen as in Example 1 was heated to 480°C in a preheater. , and communicated from the inlet of the reactor as in Example 1. At this time, the decomposition rate of laughing gas was 100%, and the total concentration of nitrogen dioxide and nitrogen monoxide contained in the gas coming out of the reactor outlet was 22 ppm. In addition, when 750 mg of halothane was added as vapor to the mixed gas of laughing gas and oxygen during the above reaction, the decomposition rate of laughing gas decreased from 100% to 100%.
It only slightly decreased to 99%. In addition, even when similar experiments were conducted after heat-treating this catalyst at 900°C for 3 hours, the rate of synthesis of laughing gas was
The total concentration of nitrogen dioxide and nitric oxide did not change. As described above, this catalyst had high catalytic activity, produced small amounts of nitrogen dioxide and nitrogen monoxide, was resistant to halothane poisoning, and had excellent heat resistance.

Example 4 By the same operation as in Example 1, a catalyst was obtained in which 5% by weight of cupric oxide, 5% by weight of chromium oxide, and 3% by weight of manganese dioxide were supported on a granular alumina carrier. . This catalyst was filled in a stainless steel tube with an inner diameter of 8 cm and a length of 75 cm to form a reactor. This reactor was heated to 540℃ with an electric heater, and a mixed gas of laughing gas and air (laughing gas: air = 27:74
% by volume) was introduced from the inlet of the reactor at 15/min. At this time, the decomposition rate of laughing gas was 98%. The total concentration of nitrogen dioxide and nitrogen monoxide contained in the gas coming out of the reactor outlet was 6 ppm. Furthermore, this experiment was repeated with each reaction time being about 3 hours, and even after a total reaction time of about 50 hours, no tendency for the decomposition rate of laughing gas to decrease was observed.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a processing device for laughing gas in surplus anesthetic gas, and shows 1...reactor, 2...blower, 3...preheater, 4...heat exchanger.

Claims (1)

[Claims] 1. Converting laughing gas in excess anesthetic gas to a catalyst containing a mixture of cupric oxide and chromium oxide at 250 to 650°C.
A method for processing laughing gas in surplus anesthetic gas, which comprises bringing the laughing gas into contact at a temperature of 100 to 1000 ml, and decomposing the laughing gas into nitrogen and oxygen. 2. Laughing gas in excess anesthetic gas according to claim 1, wherein the catalyst is a mixture further containing at least one selected from the group consisting of ferric oxide, nickel oxide, cobalt oxide, and manganese dioxide. processing method. 3. The method for treating laughing gas in surplus anesthetic gas according to claim 2, wherein the catalyst is a catalyst whose main component is a mixture of cupric oxide, chromium oxide, and manganese dioxide. 4. A reactor for decomposing laughing gas into nitrogen and oxygen at 250 to 650°C, which is filled with a catalyst mainly composed of a mixture of cupric oxide and chromium oxide. Processing equipment. 5. Laughing gas in excess anesthetic gas according to claim 4, wherein the catalyst is a mixture further containing at least one selected from the group consisting of ferric oxide, nickel oxide, cobalt oxide, and manganese dioxide. processing equipment. 6. The apparatus for treating laughing gas in surplus anesthetic gas according to claim 5, wherein the catalyst is a catalyst whose main component is a mixture of cupric oxide, chromium oxide, and manganese dioxide.