JP4096052B2 - Method for decomposing nitrile compounds contained in waste gas - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for detoxifying a nitrile compound contained in waste gas, and more particularly to a method for efficiently decomposing a nitrile compound contained in the waste gas.
[0002]
[Prior art]
An organic nitrogen compound such as acrylonitrile is a useful chemical substance used as a synthetic fiber, synthetic rubber, synthetic resin (AA resin, ABS resin, etc.), paint, and other chemical raw materials. In recent years, strong toxicity to the human body including carcinogenicity has been pointed out.
[0003]
Although the annual discharge of acrylonitrile to the atmosphere is about 1500 tons, which is small compared to other volatile organic compounds, the half-life in air is 2-4 days, and the residence time compared to formaldehyde (several hours) However, although it is considered that it does not exist at a high concentration in the general atmosphere, the general atmospheric environment concentration shows a high concentration value of 0.3 ppb according to actual measurement.
Based on this situation, acrylonitrile has been designated as one of the 22 priority action substances among the air pollutants established by the Ministry of the Environment.
[0004]
As methods for recovering acrylonitrile from a gas containing acrylonitrile generated in the process of producing acrylonitrile monomer, for example, JP-A-11-199560 and JP-A-2001-213857 are known, but these methods are complicated and large-scale. In addition, there is a limit to increasing the recovery rate, and there is a problem that acrylonitrile still remains in a high concentration in the waste gas immediately before being discharged into the atmosphere.
[0005]
In addition, a simple oxidative thermal decomposition (incineration) method can be considered as a method for treating acrylonitrile contained in the waste gas immediately before being discharged into the atmosphere, but in this case, nitrogen in acrylonitrile A new problem arises in which atoms cause harmful substances and environmental pollutants such as HCN or NOx.
[0006]
Therefore, it is indispensable to completely detoxify the source, and development of a method for completely detoxifying is also strong from the viewpoint of working environment conservation and respect for the air pollution environment at the site where organic nitrogen compounds such as nitriles are used. It has been requested.
[0007]
[Problems to be solved by the invention]
The present invention has been made to overcome the above-mentioned problems of the prior art, and the processing gas containing a nitrile compound is efficiently harmless without causing by-product harmful substances such as HCN or NOx and environmental pollutants. It is an object of the present invention to provide a decomposition method that is extremely effective as a measure against air pollution and work environment conservation.
[0008]
[Means for Solving the Problems]
As a result of intensive studies to solve the above-mentioned problems, the present inventors have determined that nitrogen in nitrile compounds does not by-produce HCN or NOx as a specific metal catalyst among metal catalysts exhibiting oxidative pyrolysis. The inventors have found that it can be decomposed to N ₂ and have completed the present invention.
[0009]
That is, according to this application, the following invention is provided.
(1) The nitrile compound contained in the waste gas is 400 to 500 in the presence of a catalyst in which at least one metal selected from Fe and Cu or a metal compound is supported on zeolite in the presence of oxygen gas and water vapor. A method for decomposing a nitrile compound contained in waste gas, characterized by oxidative thermal decomposition at ° C.
(2) The method for decomposing a nitrile compound according to (1), wherein the zeolite is ZSM-5 or ferrierite.
(3) The method for decomposing a nitrile compound according to (1) or (2), wherein the nitrile compound is acrylonitrile.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
The decomposition catalyst for nitrile compounds contained in the waste gas of the present invention is characterized in that at least one metal or metal compound selected from Fe and Cu is supported on zeolite.
[0011]
In general, metals or metal compound catalysts such as Pt and Pd are generally used for the oxidative pyrolysis treatment of organic compounds, but the effectiveness of such metal catalysts for waste gas containing nitrile compounds. In addition, there is no example of the verification of a specific catalyst that can convert nitrogen atoms contained in nitrile compounds to N ₂ gas without generating by-product HCN harmful to the human body or NOx, which is an environmental pollutant. No reports have been made.
[0012]
As a result of many years of research on an effective catalyst for oxidative thermal decomposition of a nitrile compound contained in waste gas, the present inventors have been selected from Fe and Cu from the viewpoint of environmental pollution countermeasures and work environment protection. In addition, the inventors have found that at least one kind of metal or metal compound supported on zeolite is extremely effective. The present invention has been made based on these findings.
[0013]
As used herein, “nitrile compound contained in waste gas” is an organic nitrogen compound such as polyacrylonitrile, synthetic rubber, ABS resin, AS resin, synthetic paint, or organic nitrogen compound monomer. It means a very small amount (about 1 to 300 ppm) of a nitrile compound contained in a gas discharged in a chemical factory that is produced or handled.
Specific examples of such a nitrile compound include nitrile compounds such as acrylonitrile and acetonilyl, and acrylonitrile is particularly preferable.
[0014]
The decomposition catalyst for the nitrile compound contained in the waste gas according to the present invention is at least one metal or metal compound selected from Fe and Cu .
[0015]
In this case, examples of the metal compound include oxides, nitrates, acetates, and chlorides.
[0016]
Although the catalyst according to the present invention may be used directly as it is, it is used by being supported on a carrier from the viewpoints of catalyst activity and handleability. As the carrier, zeolites such as ZSM-5, ferrierite and mordenite are used.
The amount of catalyst used may be appropriately determined according to conditions such as oxygen concentration, water vapor concentration, exhaust gas flow rate, etc. When using a carrier, the amount of catalyst used may be about 1 to 5% by weight with respect to the carrier. desirable.
[0017]
The catalyst according to the present invention can be easily prepared by a conventionally known catalyst preparation method such as an impregnation method, a coprecipitation method, an ion exchange method and the like.
[0018]
In the present invention, in order to decompose the organic nitrogen compound contained in the waste gas, the organic nitrogen compound-containing waste gas may be oxidatively pyrolyzed in the presence of the catalyst.
[0019]
Oxidative pyrolysis is performed in the presence of oxygen gas and water vapor.
In this case, it is preferable to select conditions with an oxygen concentration of 1 to 20% by weight; a water vapor concentration of 0.5 to 10%, and an oxygen / water vapor ratio of about 0.1 to 40.
[0020]
Although there is no limit to the anti 応温degree is 400 to 500 ° C. in the range of 150 to 500 ° C., The reaction pressure is vacuum to atmospheric pressure, but may be any of pressure, it is preferably carried out in atmospheric pressure.
The volume of the catalyst bed, by considering the feed rate of the waste gas containing an organic nitrogen compound may be determined appropriately, but is usually a space velocity 500～200000H ^-1 preferably 50000-100000H ^-1 .
[0021]
Moreover, although there is no special restriction | limiting in the apparatus used in order to decompose | disassemble the waste gas containing the nitrile compound of this invention, It is desirable to use a fixed bed flow reaction apparatus.
[0022]
【Example】
Hereinafter, the present invention will be described in more detail with reference to examples.
[0023]
Example 1
A ZSM-5-supported Cu catalyst body and a ferrierite-supported Cu catalyst were prepared as follows by an ion exchange method.
The ZSM-5-supported Cu catalyst was prepared by dissolving 0.4 g of copper acetate in 100 ml of ion-exchanged distilled water and heating to 80 ° C. Then, 2.9 g of NH ₄ -ZSM-5 was added to this solution and refluxed. Stir for hours and ion exchange. The catalyst was suction filtered, washed with 100 ml of ion-exchanged distilled water, dried at 110 ° C. for 12 hours, and calcined at 500 ° C. for 4 hours to prepare each of the above catalysts.
0.1 g of each supported catalyst obtained above was taken and filled in a quartz reaction tube having an inner diameter of 8 mm, and the reaction tube was installed in a fixed bed flow reactor. The flow rate was adjusted with a mass flow controller, and a 5% O ₂ / He mixture was passed through the reaction tube at a flow rate of 160 ml / min and pretreated at 500 ° C. for 2 hours. Each pre-treated supported catalyst was introduced with a mixed gas of acrylonitrile and oxidizing gas having the following composition (1) at a total flow rate of 160 ml / min.
(1) Acrylonitrile (200 ppm) + O ₂ (5%) + H ₂ O (0.5%)
Next, the N ₂ concentration produced at each decomposition temperature was measured with a gas chromatograph. The result is shown in FIG.
[0024]
Example 2
Produced at each reaction decomposition temperature in the same manner as in Example 1 except that ZSM-5-supported Fe catalyst body and ferrierite-supported Fe catalyst were prepared by solid-phase ion exchange using iron chloride ( II ) instead of copper acetate. The N ₂ concentration to be measured was measured with a gas chromatograph. The result is shown in FIG.
[0025]
Reference example 1
The N ₂ concentration produced at each reaction decomposition temperature was measured by a gas chromatograph in the same manner as in Example 1 except that an Al ₂ O ₃ supported Fe catalyst and a TiO ₂ supported Fe catalyst were prepared using the impregnation method . The result is shown in FIG.
[0026]
Reference example 2
The N ₂ concentration produced at each reaction decomposition temperature was measured with a gas chromatograph in the same manner as in Example 1 except that a Zr ₂ O ₃ supported Ag catalyst and a TiO ₂ supported Ag catalyst were prepared using the impregnation method . The result is shown in FIG.
[0027]
Reference example 3
The N ₂ concentration produced at each reaction decomposition temperature was determined in the same manner as in Example 1 except that a ZSM-5 supported Co catalyst using an ion exchange method and an Al ₂ O ₃ supported Co catalyst using an impregnation method were prepared. Measured with a graph. The result is shown in FIG.
[0028]
Comparative Example 1
The N ₂ concentration produced at each reaction decomposition temperature was measured by a gas chromatograph in the same manner as in Example 1 except that an impregnation method was used to prepare an Al ₂ O ₃ supported Pt catalyst and an Al ₂ O ₃ supported Pd catalyst, respectively . . The result is shown in FIG.
In the figure, NOx, e. t. c. Is a total of NOx, HCN, NH ₃ , N ₂ O, and acetonitrile obtained as by-products .
[0029]
【The invention's effect】
The decomposition treatment method according to the present invention is capable of efficiently detoxifying a treatment gas containing a nitrile compound without generating by-product harmful substances or environmental pollutants such as HCN or NOx, and measures against air pollution and working environment. It can be said that it is a very effective method for maintenance.
[Brief description of the drawings]
FIG. 1 is a graph showing the relationship between the conversion rate of nitrogen in acrylonitrile to N ₂ and the decomposition temperature (decomposition catalyst of Example 1).
FIG. 2 is a graph showing the relationship between the conversion rate of nitrogen in acrylonitrile to N ₂ and the decomposition temperature (decomposition catalyst of Example 2).
FIG. 3 is a graph showing the relationship between the conversion rate of nitrogen in acrylonitrile to N ₂ and the decomposition temperature (decomposition catalyst of Reference Example 1).
FIG. 4 is a graph showing the relationship between the conversion rate of nitrogen in acrylonitrile to N ₂ and the decomposition temperature (decomposition catalyst of Reference Example 2).
FIG. 5 is a graph showing the relationship between the conversion rate of nitrogen in acrylonitrile to N ₂ and the decomposition temperature (decomposition catalyst of Reference Example 3).
FIG. 6 is a graph showing the relationship between the conversion rate of nitrogen in acrylonitrile to N ₂ and the decomposition temperature (decomposition catalyst of Comparative Example 1).

Claims (3)

The nitrile compound contained in the waste gas is oxidized at 400 to 500 ° C. in the presence of oxygen gas and water vapor in the presence of a catalyst in which at least one metal selected from Fe and Cu or a metal compound is supported on zeolite. A method for decomposing a nitrile compound contained in waste gas, characterized by thermally decomposing it. The method for decomposing a nitrile compound according to claim 1, wherein the zeolite is ZSM-5 or ferrierite. The method for decomposing a nitrile compound according to claim 1 or 2, wherein the nitrile compound is acrylonitrile.

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