JPS6339864B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention is an analytical method based on the principle of quantifying carbon monoxide by oxidizing carbon monoxide CO in exhaust gas to carbon dioxide CO ₂ .
It uses a catalyst that oxidizes CO. According to the Japanese Industrial Standards (K0098), methods for quantifying CO in exhaust gas include oxidation condensation method, gas chromatography method, non-dispersive infrared analysis method, detection tube method,
Examples include oxidation titration method and spectrophotometry method. In particular, the oxidation condensation method and oxidation titration method are based on the principle of oxidizing CO to CO ₂ and quantifying CO based on its properties as CO ₂ .
According to the Japanese Industrial Standards, CuO/MnO ₂ = 40/60 (wt%), MnO ₂ /CuO _/
A hopcalite catalyst with CoO/Ag ₂ O = 50/30/15/5 (wt%) is currently being used.
oxidize only CO below; (2) completely oxidize hydrocarbons at 120 to 500°C and decompose them into water (H ₂ O) and carbon dioxide (CO ₂ ); (3) oxidize carbon dioxide generated below 240°C. It has the property of adsorbing carbon (CO ₂ ) as manganese carbonate and copper carbonate. Therefore, in analytical methods using the oxidation condensation method, the differential pressure method removes the condensable components in the sample gas by cooling with liquid air, and the remaining gas is passed through a hopcalite catalyst at room temperature.
Oxidizing CO to _CO2 . On the other hand, in the vaporization pressure measurement method using a vacuum type quantitative device and the vaporization pressure measurement method using a gas passage type quantitative device, condensable components in the sample gas are removed by cooling with liquid air, but the remaining gas is transferred to a hopcalite catalyst heated to 240°C. CO by passing CO ₂
It is oxidized to The reason for heating the catalyst to 240℃ is
This is because CO ₂ adsorbed on the catalyst as carbonate is completely desorbed at 240°C. Therefore, the differential pressure method used at room temperature is effective at low concentrations because CO ₂ is adsorbed on the catalyst.
Not suitable for CO analysis, suitable for analysis of 0.1% or more. On the other hand, the vaporization pressure measurement method using a vacuum quantitative device is suitable for CO analysis of 0.001% or more, and the vaporization measurement method using a gas passage quantitative device is suitable for CO analysis of 0.0001% or more. In the oxidation titration method, CO is oxidized to _CO2 by passing the sample gas through a hopcalite layer heated to 120℃, so hydrocarbons other than methane are also oxidized, making it possible to analyze relatively high concentrations of CO (0.01 to 1.1%). Are suitable. The present invention has the following advantages: (1) Even at room temperature in the presence of water, CO
quantifies CO in exhaust gas using a catalyst that has properties such as (2) no sorption or adsorption of CO ₂ even at room temperature, and ( ₃ ) no oxidation of hydrocarbons at temperatures below 150°C. This is an analytical method that does not require cooling with liquid air to remove condensed components in the sample gas, and has the advantage that CO can be completely oxidized to CO ₂ at room temperature or with only slight heating. Therefore, it is possible to analyze relatively low concentrations of CO using the dropwise titration method or differential pressure method.
Furthermore, there is no need to heat the catalyst to 240°C as in the vaporization pressure measurement method, and it is only necessary to heat it to room temperature or slightly. Examples of the present invention will be described in detail below. FIG. 1 is an example of an apparatus for measuring CO concentration using a vaporization pressure measurement method using a gas passage quantitative device, which is a method of the oxidation condensation method. 1 is a gas sample introduction port, but it may also be a calibration gas sample cylinder connection port. 2 is a U-shaped tube for CO ₂ condensation, 3 is a dewar bottle for liquid air or dry ice, 4 is a CO oxidation catalyst as a gas oxidizer, 5 is a heater, 6
is a capillary pressure gauge, 7 is a scale, 8 is a mercury reservoir, 9
is a trap for moisture removal, 10 is an exhaust pump, 1
1a-g are Kotoku, 12 is wet gas meter, 1
3 is a thermometer, and 14 is a differential pressure gauge. The method for quantifying CO follows the Japanese Industrial Standards (JISK0098); the sample gas is introduced through the gas sample inlet 1, passed through the CO oxidation catalyst 4, oxidizes CO to CO ₂ , and then condensed with liquid air in the distiller bottle 3. This is then vaporized into a certain volume and the pressure is measured to quantify it. The details of the analysis procedure are shown in (1) to (6) below. (1) Close Kotoku 11a and 11c, and close Kotoku 11
After opening b, 11d, 11e, 11f, and 11g and evacuating the device with the exhaust pump 10, read the height H (mmHg) of the mercury column. Put the U-shaped tube 2 into the juicer bottle 3 containing liquid air, and
Open a and introduce the sample gas from the gas sample inlet 1.
Introduce into the device at a flow rate of 200 ml/min. (2) Carbon monoxide is oxidized to carbon dioxide by the gas oxidizer 4, condensed and fixed in the U-shaped tube 2, and after passing a predetermined amount of sample gas, the introduction is stopped. Note that the temperature of the heater 5 is adjusted in advance so that the temperature of the gas oxidizing agent 4 is between room temperature and 150°C. (3) After closing the pot 11a and evacuating the inside of the device, close the pots 11d, 11e, and 11f, and use the scale 7 of the capillary pressure gauge 6 to check the pots 11e and 1 in the device.
Read the pressure h ₀ (mmHg) between 1f. (4) Open the pot 11e, remove the brewer bottle 3 from the U-shaped tube 2, warm the U-shaped tube 2 in a beaker filled with hot water to vaporize carbon dioxide, wipe off the water on the outside of the U-shaped tube 2, and return it to room temperature. After that, the scale 7 of the capillary pressure type 6 was set to 11d and 1 in the device.
Read the pressure h ₁ (mmHg) between 1f. (5) Open the pots 11c, 11d, and 11f. The height of the mercury column is increased to H (mmHg) by the exhaust pump 10.
The gas is evacuated until it shows , and is sent to the gas meter 12. Sample gas volume V ₀ passed throughout the entire operation
(ml) with gas meter 12. (6) Calculate the carbon monoxide concentration using the following formula. C=P ₁ V ₁ /P ₀ V ₀ ×100 where C: Carbon monoxide concentration (%) V ₁ : Volume of gas pressure measuring part (ml) P ₁ : Pressure increased by vaporization of carbon dioxide h ₁ −
h ₀ (mmHg) V ₀ : Total sample gas volume that passed through the gas meter (ml) P ₀ : P _a +P _n −P _v ≒P _a −P _v P _a : Atmospheric pressure (mmHg) P _n : Gauge in wet gas meter Differential pressure (mmHg) P _v : Saturated vapor pressure of water at that temperature of the wet gas meter (mmHg) The hand pressure gauge 6 has mercury sealed in a capillary tube, and a mercury reservoir 8 is placed at the bottom. . The gas meter 12 is also provided with a thermometer 13 and a differential pressure gauge 14, which are used to read the temperature of the sample gas and the gauge differential pressure. The CO oxidation catalyst 4, which is a gas oxidizer, is a mixture of alkali, cement agent, and powdered activated carbon mixed with platinum.
This is a catalyst in which one or more selected from the group of ruthenium and rhodium and palladium are simultaneously supported, or palladium alone is supported. The analysis method of this example can also be applied to other analysis methods, such as a vaporization pressure measurement method using a vacuum quantitative device, a differential pressure method, and an oxidation titration method, which is a method of the oxidation condensation method. Since the CO conversion rate of the CO oxidation catalyst 4 changes depending on the CO concentration and water content contained in the sample gas,
The oxidation catalyst 4 is heated by the heater 5 to a temperature at which CO is completely oxidized. However, the temperature of the CO oxidation catalyst 4 shall be 150°C or less. To collect sample gas, insert a pipe into the gas emission source, pass it through a dust removal bottle containing glass wool, etc., and then mix and mold an activated carbon layer, chlorite, alkali, and cement agent. is a thing
The NO ₂ remover layer is a mixture of alkali, powdered activated carbon, and cement. This is to prevent the CO oxidation catalyst 4 from being poisoned by ammonia, NO, NO ₂ , SO ₂ , etc. contained in the exhaust gas and reducing its activity. Catalysts in which one or more selected from the group of platinum, ruthenium, and rhodium and palladium are supported at the same time or palladium alone on a kneaded molded product of alkali, cement agent, and powdered activated carbon release CO even under humidified conditions at room temperature.
oxidizes to _CO2 . Now, we selected potassium carbonate as the alkali and alumina cement as the cement agent, added 0.5 wt% of sodium carboxymethyl cellulose and water to the composition of potassium carbonate/alumina cement/powdered activated carbon = 10/60/30 (wt%), and kneaded and molded the mixture. The material was dried and classified into 10 to 20 mesh pieces. After simultaneously supporting 0.3wt% each of platinum and palladium as precious metals on the above kneaded and molded product,
The catalyst was reduced with sodium borohydride, thoroughly washed with water, and dried at about 100°C. Figure 2 shows the temperature characteristics of the catalyst under conditions of CO 100 ppm, SV 24000 hr ^-1 , and absolute humidity 0.0145 Kg/Kg dry air.
Figure 3 shows the conditions: 100ppm, SV24000hr ^-1 temperature 30℃
Figure 4 shows the humidity characteristics under conditions of CO100ppm and temperature.
Figure 5 shows the space velocity (air passing flow rate/amount of catalyst used) at 25°C and 60% humidity.The conditions are SV24000hr ^-1 and temperature 25
Concentration characteristics at ℃ and 60% humidity are shown. The CO characteristics of the catalyst are determined using a fixed bed flow device, in which the catalyst is packed into an integral tubular reactor and the CO characteristics are measured at a predetermined concentration.
The change in concentration before and after the catalyst layer was measured using a non-dispersive infrared spectrometer by flowing air containing the catalyst at a constant flow rate. The oxidation properties of the catalyst for hydrocarbons are shown in Table 1, and the hydrocarbon concentration was 300ppm.
(in terms of _CH4 ), and the space velocity (SV) is 24000hr ^-1 .

[Table] The catalyst oxidizes hydrocarbons at a temperature of 150°C or higher.
The oxidation characteristics for a mixed gas of CO and hydrocarbons are shown in Table 2. SV is 24000hr ^-1 , absolute humidity is 0.0145Kg/Kg
It was made into dry air.

[Table] The catalyst selectively oxidizes CO even in a mixed gas of CO and hydrocarbons at temperatures below 150°C without any interference from hydrocarbons. In addition, in terms of durability, the catalyst decomposes with heat generation at 385℃ according to differential thermal analysis, but it is stable in the temperature range below that and is preferably 100℃ or below.
It is thermally stable enough when used at ~80°C. Regarding the influence of inorganic gases on the catalyst, it is known that the catalyst is poisoned by ammonia, NO, NO ₂ and SO ₂ and its activity decreases. However, when collecting sample gases, ammonia is mixed with activated carbon, NO and SO ₂ are mixed with baseite, alkali, and cement material, and NO ₂ and SO ₂ are mixed with alkali, powdered activated carbon, and cement material. Since the catalyst can be removed even under humidified conditions at room temperature using a kneaded molded product, a decrease in the activity of the catalyst can be prevented by passing through these layers. Next, the effects of this embodiment will be described. CO in flue gas was analyzed at a temperature of 25°C and a relative humidity of 63%. The exhaust gas contained only CO, and the CO analysis was conducted by imitating the operating procedures of the Japanese Industrial Standards (K0098) and applying the vaporization pressure measurement method using a gas passage quantitative device. The catalyst shown in Figure 1 is filled with the catalyst manufactured according to the above-mentioned adjustment procedure so that the bed height is 50 mm. Before use, the catalyst is loaded into the equipment and dried under vacuum heating at approximately 100°C. The temperature of the catalyst layer was 50°C when the sample gas was passing through. Table 3 shows the results analyzed using the non-dispersive infrared analysis method, and those analyzed using the vaporization pressure measurement method using a JISK0098 gas-passing quantitative device, which was cooled with liquid air and heated to 240℃ to remove condensable components from the exhaust gas. The results are shown below, which were analyzed by passing through the hopcalite catalyst and analyzed by this example.

[Table] As shown above, it can be seen that the CO concentration can be accurately measured according to this example. As described above, the advantages of the present invention are as follows, and are of extremely great industrial value. In the oxidation condensation method, there is no need to cool the sample gas with liquid air immediately before passing it through the catalyst layer to remove condensable components in the sample gas, and the sample gas can be directly introduced into the catalyst layer, making it possible to prepare liquid air for each measurement. There's no need to. In addition, in the vaporization method using a vacuum type or gas passage type metering device, there is no need to heat the catalyst to 240°C, and a low temperature of 150°C or less is sufficient.
A low-capacity heater is sufficient, resulting in energy savings. The applicable concentration range of the catalyst used is from the environmental concentration range (10 ppm or less) to 2000 ppm.
As can be seen from the figure, the CO conversion rate decreases as the concentration becomes higher than 100 ppm, making it ideal for low concentration gas analysis, and for concentrations below 0.1% that cannot be accurately analyzed using the differential pressure method or oxidation titration method. Analysis becomes possible.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of a gas passage type metering device according to an embodiment of the present invention, FIG. 2 is a temperature characteristic diagram of a catalyst,
Figure 3 is the humidity characteristic diagram of the catalyst, and Figure 4 is the S.
V. Characteristic Diagram, Figure 5 is a concentration characteristic diagram of the catalyst.

Claims (1)

[Claims] 1 A catalyst in which platinum and palladium were simultaneously supported on a carrier with a composition of potassium carbonate: alumina cement: powdered activated carbon = 10:60:30 (wt%) was packed into a gas passage type metering device equipped with an exhaust pump. The sample gas is passed through the catalyst heated to room temperature to 150°C to oxidize carbon monoxide to carbon dioxide, and this carbon dioxide is condensed and fixed with liquid air, then vaporized into a certain volume, and the pressure is measured. A carbon monoxide analysis method characterized by quantifying carbon monoxide concentration.