JPS58223736A - Collecting method of nitrogen monoxide - Google Patents

Abstract

PURPOSE:To measure a trace quantity of NO in sample gas with high accuracy, by collecting the NO in the gas by adsorption by passing the sample gas through a powdered and granular layer of manganese oxide. CONSTITUTION:In the case where a sample gas 1 contains an acidic or alkaline nitrogen compound, the gas 1 is passed through an alkaline matter removing vessel 5 and an acidic matter removing vessel 6 and in the case where the gas 1 contains only neutral gas, the gas 1 is passed directly through a dehydrator 7. Hereafter, said gas is passed through a quartz tube 3 filled up with 5-200 mesh powdered and granular body 4 of manganese oxide (1.5-1.95 O atoms per 1 Mn atom and amorphous manganese oxide is preferable). NO in the gas is collected by adsorption at 5-40 deg.C (room temperature may be preferable) by the body 4. A fixed quantity of the collected manganese oxide is weighed in a platinum boat and weighed manganese oxide is heated at 800 deg.C in a gaseous H2 current. Then, generated NH3 is absorbed in a collection liquid and the coulometric titration is performed. Manganese dioxide for an elemental analysis available on the market is used for said manganese oxide. In this manner, the measurement of extremely minute quantity of the NO is made possible.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for collecting trace amounts of nitric oxide contained in gas, and particularly to a method for collecting nitric oxide suitable for measuring the concentration of trace amounts of nitrogen oxide in gas.

Conventionally, nitrogen monoxide in flue gas emitted from flues, chimneys, etc. has been measured continuously by chemiluminescence, infrared absorption, and ultraviolet absorption methods, or by measuring hydrogen peroxide in a sulfuric acid solution or peroxide. It is passed through an oxidizing absorbent such as a sulfuric acid solution of potassium manganate, absorbed and concentrated, and then measured by, for example, phenol disulfonic acid spectrophotometry. However, with the chemiluminescence method, which is considered to be a highly sensitive analytical method, the quantification limit for nitrogen oxide is at the ppm level, and ppb
Measuring levels is difficult and impossible.

Furthermore, the method of lowering the quantification limit level by absorbing and concentrating nitrogen monoxide by passing a large amount of gas through an oxidizing absorbent cannot be applied to sample gases that react with the oxidizing absorbent, so its scope of application is limited.

The present invention focuses on such a problem and provides a method for collecting nitrogen oxides that makes it possible to measure trace amounts of nitrogen oxides at the ppb level in a sample gas. By passing the powder j- of
The present invention provides a method for collecting nitric oxide, which is characterized by adsorbing and collecting nitric oxide contained in a sample gas on manganese oxide.

As a powder or granule of manganese oxide, 5 to 200 mesh,
Preferably, 10 to 40 meshes of manganese oxide are used.

As manganese oxide, an amorphous one is preferable, and manganese oxide with a large amount of crystallinity is not preferable because its adsorption capacity decreases.

In addition, the composition ratio of manganese and oxygen is 2.0 or less, generally 1.5 to 1.95, preferably 1.5 to 1.95 oxygen per 1 atom of manganese,
1.85 to L90 is used.

Such manganese dioxide can be selected from those commercially available as manganese dioxide for elemental analysis.

Manganese oxide is generally filled into a tube made of glass, quartz glass, metal, etc. to form a collection layer. - When used for measuring nitrogen oxide, pretreatment is performed by passing a high purity non-nitrogen-containing gas such as argon, helium, oxygen, etc. at a high temperature of about 200 to 600°C.

The collection of nitrogen monoxide in the sample gas is carried out at a temperature of 5 to 20°C, preferably 5 to 40°C.

- Manganese oxide that adsorbed nitrogen oxide was mixed with a known nitrogen analysis sample in 1. It can be served as
Nitrogen-enriched dust is measured. An example of an analysis method is -
A certain amount of nitrogen oxide adsorbing and manganese oxide powder was weighed into the platinum port, and the nuclear platinum boat was heated in a hydrogen stream for 8 hours.
After heating to 00° C. and absorbing the generated NH3 into an ammonia collection liquid, ammonia can be measured by coulometric titration.

The present invention can measure the concentration of nitrogen monoxide in a sample gas containing nitrogen monoxide and nitrogen dioxide by passing the sample gas through a suitable absorbent and removing nitrogen dioxide from the gas. By direct collection, nitrogen dioxide and nitrogen monoxide can be measured as the total nitrogen amount.

EXAMPLES Below, the performance confirmation test results of the present invention will be demonstrated along with examples in which the present invention is used for measuring nitrogen monoxide.

Figure 1 shows a cylinder filled with high-purity gas, 2 a generator that generates a certain amount of nitrogen monoxide, and 3 a container filled with purified manganese oxide 4 to collect nitrogen monoxide. Showing the waste collection tube. After passing the high purity gas L together with nitrogen monoxide from the generator 2 through the collection tube 3 for a certain period of time, the manganese oxide is taken out and the total nitrogen content in the manganese oxide 4 is measured.

An experiment was conducted using the apparatus shown in FIG. 1 under the following conditions, and the results shown in Table 1 were obtained. - It can be confirmed that about 10% of nitrogen oxides are completely collected.

Manganese dioxide: Manufactured by Kishida Chemical Co., Ltd. Mn:O=1:lj, 88 14-16 mesh 1.0 Of Collection tube used Made of diquartz gas 2s Internal diameter 8 Capture temperature/Room temperature (23℃) Acidic or alkaline An example of absorbing and concentrating -oxidizing chamber elements in a gas containing nitrogen compounds is shown in Fig. 2.
, In Fig. 2, ] is a container containing naphtha decomposition gas, which is a sample gas, 5 is an acidic substance removal container containing an alkaline substance, 6 is an alkaline substance removal vessel containing an acidic substance, and 7 is a container containing a dehydrating agent. It is a moisture removal container. As the alkaline substance, 254 potassium hydroxide aqueous solution, as the acidic substance, a pentavalent sulfuric acid aqueous solution, and as a dehydrating agent and 12, silica gel was used. After passing the naphtha cracked gas together with nitrogen monoxide from the generator 2 or only the naphtha cracked gas through the collection tube 3 for a certain period of time, the manganese oxide 4 is taken out and the total nitrogen content in the manganese oxide is measured. ,Ta.

As a result, the values shown in Table 2 were obtained using the same collection agent and collection temperature as in the method described above.

By adding the above-mentioned removal container, a part of the introduced nitrogen oxide is absorbed by the removal material, and the recovery rate of nitrogen monoxide tends to decrease slightly, but in the analysis of nitrogen monoxide in the trace amount range, There are no problems.

Table 1 Table 2

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing an example of absorbing and concentrating nitrogen monoxide in a gas that does not contain acidic or alkaline nitrogen compounds. FIG. 2 is an explanatory diagram showing an example of absorbing and concentrating nitric oxide. 1: Sample gas 3: Collection tube 4: Manganese oxide Patent applicant Mitsubishi Yuka Co., Ltd. agent Patent attorney Hidetoshi Furukawa (1 other person)

Claims (1)

[Claims] A method for collecting nitric oxide, which comprises passing a sample gas through a powder layer of manganese oxide, thereby adsorbing and collecting nitric oxide contained in the sample gas onto the manganese oxide.