JP2017094309A - Aldehyde removal catalyst, method for producing the same, and aldehyde gas removal method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low temperature removal catalyst and a removal method for aldehyde gas, which have high performance of aldehyde gas removal in a low temperature region without using a noble metal and have little effect on environmental pollution and human body.SOLUTION: The problem can be solved by: using a composite metal catalyst containing cerium and copper; making the catalyst come in contact with aldehyde gas which is oxidatively decomposed; and having decomposition products of the aldehyde gas adsorbed and removed by the catalyst.SELECTED DRAWING: None

Description

  The present invention relates to an aldehyde removal catalyst, a method for producing the catalyst, and a method for removing aldehyde gas.

  Conventionally, air purifiers and deodorizing agents have been widely used mainly for the purpose of removing tobacco odors in the interior of buildings or in automobiles. These are intended to remove acetaldehyde, which is the main component of tobacco odor, or formaldehyde, which is a causative substance of sick house, and many removal agents have been studied. Among them, activated carbon has long been known as a material for adsorbing and removing various organic substances, but it cannot sufficiently adsorb and remove low-molecular and high-polarity organic substances (for example, acetaldehyde, formaldehyde, etc.). In the case of use in the present invention, an activated carbon having amines, ascorbic acid or the like supported thereon to enhance the adsorption removal ability is used.

  Thus, as what carried amines, the thing using aniline (patent document 1), the thing using ethanol system amine, etc. are disclosed, for example (patent document 2).

  However, the technology for supporting amines is unstable in the state of the supported amines, and thus is easily deactivated due to thermal and chemical changes over time, and can exhibit satisfactory removal performance over a long period of time. There is a problem that it is difficult. In addition, ascorbic acid also has a problem that when it absorbs moisture, it is easily oxidized and decomposed in the air and deactivated, resulting in performance deterioration.

  On the other hand, as a processing technique for aldehyde gases, a processing technique for oxidatively decomposing aldehydes using a noble metal-supported catalyst is known. As the noble metal-supported catalyst, for example, there is a gold-supported cerium-containing oxide (Patent Document 3). However, since this uses a noble metal, there is a problem that the cost increases.

  In addition, as a catalyst for decomposing volatile organic compounds that do not use precious metals, complex oxides containing cerium, cobalt, and copper (Patent Documents 4 and 5), and formaldehyde oxidation catalysts comprising complex oxides containing cerium and manganese (patents) Document 6) is disclosed. However, such cobalt-containing composite oxides and manganese-containing composite oxides contain cobalt compounds and manganese compounds that are PRTR first-class designated chemical substances, and there is a concern about environmental pollution. Further, these have low activity at low temperatures, and there is a problem that sufficient removal performance cannot be obtained unless a temperature higher than 100 ° C. is applied.

  Furthermore, although cerium oxide alone, which does not contain manganese or cobalt, has the ability to remove aldehydes at low temperatures, alcohol is generated as a decomposition product, which does not adsorb on the removal material and scatters in the air. It is harmful.

  As described above, there is currently no aldehyde gas removal catalyst that does not use precious metals, has a low temperature range, has a low influence on environmental pollution and the human body, and has a high removal performance. The low temperature region referred to in the present application is 100 ° C. or lower.

JP 56-53744 A JP-A-60-202735 JP 2004-74069 A Japanese Patent No. 5414719 Japanese Patent No. 5422320 JP 2010-58074 A

  The present invention provides a low-temperature removal catalyst for aldehyde gases, which has high aldehyde gas removal performance in a low-temperature region without using precious metals, and has low impact on the environment and the human body, a method for producing the same, and a method for producing aldehyde gases. An object is to provide a removal method.

As a result of intensive studies to solve the above problems, the present inventors have finally completed the present invention. That is, this invention consists of the following structures.
1. A composite metal catalyst containing cerium and copper, wherein the composite metal oxide contains 4 to 20% by mass of copper in terms of CuO.
2. The aldehyde removal catalyst according to 1 above, which has an aldehyde removal performance at a low temperature of 100 ° C. or lower.
3. 3. The aldehyde removal catalyst according to 1 or 2 above, wherein ethanol is not produced when air containing 100 ppm of acetaldehyde is sealed in the presence of an aldehyde removal catalyst and heated at 80 ° C. for 100 minutes.
4). 4. The low temperature removal catalyst for aldehydes according to any one of 1 to 3 above, wherein the composite metal oxide containing cerium and copper has a BET specific surface area of 30 m ² / g or more.
5. The method for producing an aldehyde removal catalyst according to any one of the above 1 to 4, wherein a compound obtained by coprecipitation from cerium salt and copper salt is calcined.
6). 6. The method for producing an aldehyde removal catalyst according to 5 above, wherein the cerium salt and the copper salt are both nitrates.
7). An aldehyde gas characterized in that the aldehyde removal catalyst according to any one of the above 1 to 5 is brought into contact with an aldehyde gas to undergo oxidative decomposition, and the decomposition product of the aldehyde gas is adsorbed and removed by the catalyst. Removal method.
8). A method for removing aldehyde gas, wherein the aldehyde gas is removed by low-temperature heating within a range of 40 ° C to 100 ° C using the aldehyde removal catalyst according to any one of 1 to 4 above.

  The aldehyde removal catalyst according to the present invention is a cerium-copper composite oxide obtained by calcining a compound obtained from a cerium salt and a copper salt by a coprecipitation method. It has the advantage that there is little influence on. Further, the aldehyde removal catalyst of the present invention oxidatively decomposes aldehyde gas, and the catalyst absorbs and removes the decomposition product of aldehyde gas, so that no decomposition component drifts in the air, and there is little influence on the human body. This can be said to be a method for removing aldehyde gases.

Hereinafter, the present invention will be described in detail.
The aldehyde removal catalyst in the present invention is composed of a cerium-copper-containing composite metal oxide. The method for synthesizing the cerium-copper composite oxide is preferably a method in which a cerium salt and a copper salt are used as raw materials, a compound is obtained by a coprecipitation method, and they are fired. By using the cerium-copper composite oxide synthesized using the coprecipitation method as a low-temperature removal catalyst for aldehydes, it has low impact on the environment and the human body, and aldehyde gases can be removed with high efficiency in the low-temperature region. I found. Examples of aldehydes mentioned here include formaldehyde and acetaldehyde. The coprecipitation method is a method in which a plurality of types of hardly soluble salts are simultaneously precipitated from a solution containing two or more types of metal ions, and a highly uniform compound can be obtained.

  In the aldehyde removal catalyst comprising a complex oxide containing cerium and copper according to the present invention, it is preferably synthesized by a coprecipitation method. In synthesis methods other than the coprecipitation method, for example, physical decomposition of oxides or decomposition of carbonate by baking carbonate mixed powder, copper element is not highly dispersed in cerium element, and as a result, aldehyde gas However, when it comes to the vicinity of the catalyst, the synergistic effect of copper and cerium cannot be expressed, the influence on the human body is low, and the aldehyde gas cannot be removed with high efficiency in a low temperature region. The catalyst having a low influence on the human body is a catalyst that does not generate decomposition products harmful to the human body such as alcohol and carboxylic acid in the air when the aldehyde gas is decomposed by the catalyst. Although the mechanism of the synergistic effect is not clear, it is presumed as the following (1) to (4).

That is, first, (1) the aldehyde gas is captured on the cerium element, and then (2) the aldehyde gas captured on the cerium element is activated and easily decomposed by the electron transfer function of cerium. (3) The aldehyde gas activated on the cerium element is oxidatively decomposed into acetic acid by the copper element located in the very vicinity thereof. At that time, (4) it is considered that the decomposing power is improved also in the copper element due to the electron transfer action from the cerium element located in the vicinity. Further, since cerium oxide also has an action of absorbing and releasing oxygen as in the following formula, it is considered that it acts as an oxygen supply source and promotes oxidative decomposition of aldehyde gas using copper as a catalyst.
2CeO ₂ ⇔ Ce ₂ O ₃ + O

  As described above, when the copper element is highly dispersed in the cerium element using the coprecipitation method, and copper and cerium are in the vicinity, oxidative decomposition using copper as a catalyst proceeds to produce acetic acid. Since this acetic acid is adsorbed and removed by the catalyst, it is not dispersed in the air. On the other hand, when a method other than the coprecipitation method is used, the disproportionation reaction of the aldehyde gas by cerium alone proceeds to produce acetic acid and ethanol. In this case, acetic acid is adsorbed and removed by the catalyst, but ethanol is not removed and drifts in the air, which is harmful to the human body.

  An aldehyde low temperature removal catalyst comprising a composite metal oxide containing cerium and copper is synthesized by a coprecipitation method as described above. As a synthesis procedure, it can be obtained by preparing an aqueous solution containing a cerium salt and a copper salt, adding an alkali to form a precipitate, and firing the precipitate. Examples of the cerium salt and copper salt used as the raw material for synthesis include nitrates, sulfates, carbonates, hydrates, chlorides and the like, and nitrates are preferred. Examples of the alkali include sodium hydroxide, potassium hydroxide, sodium carbonate and ammonium hydroxide solution. It is preferable to use an ammonium hydroxide solution from the viewpoint of reducing the particle size of the primary particles and preventing impurities from remaining in the prepared sample. As pH of the aqueous solution for producing | generating a deposit, it is 7-12, Preferably it is 8-10. The resulting precipitate is dried and calcined in air. The drying temperature is preferably 30 to 120 ° C., and the drying time is preferably 5 to 10 hours. The firing temperature is preferably 300 ° C to 800 ° C, more preferably 500 ° C to 700 ° C. The firing time is preferably 1 hour to 8 hours, more preferably 3 hours to 6 hours.

  The copper content in the composite oxide containing cerium and copper is not particularly limited, but is preferably 4 to 20% by mass, more preferably 4 to 20% in terms of CuO from the viewpoint of further enhancing the catalytic ability of copper. It is preferably 15% by mass, and most preferably 4 to 7% by mass. If it is less than 4% by mass, the amount of copper oxide is too small, and therefore the influence of (3) in the synergistic effect mechanism becomes small, and as a result, sufficient removal performance cannot be realized. Moreover, when it exceeds 20 mass%, a cerium element is coat | covered with a copper element, (1) and (2) in the mechanism of the said synergistic effect will be inhibited, and a synergistic effect will become small, As a result, sufficient Removal performance cannot be realized.

  The content of cerium is preferably 80 to 96% by mass in terms of CeO, more preferably 85 to 96% by mass, and most preferably 93 to 96% by mass. When it exceeds 96 mass%, since the amount of cerium is too large, (3) in the synergistic effect mechanism does not work effectively, and the oxidation reaction hardly proceeds in the first place. If the amount is less than 80% by mass, the cerium element is coated with the copper element, and (1) and (2) in the mechanism of the synergistic effect are hindered, and the synergistic effect is reduced. Performance cannot be realized.

The BET specific surface area of the composite metal oxide containing cerium and copper is preferably 30 m ² / g or more. If it is less than 30 m ² / g, the concentration effect by the pores is small, and the reaction rate of the catalyst becomes slow.

  As a method for removing the aldehyde gas using the aldehyde removal catalyst of the present invention, the aldehyde gas is brought into contact with the aldehyde removal catalyst of the present invention at 40 to 100 ° C., preferably 80 to 100 ° C. Good. The ability to remove aldehyde gases at a low temperature makes it possible to use them in household and automobile filters, and they can be installed in factory exhaust gas treatment equipment to decompose aldehydes with low energy.

  Hereinafter, the present invention will be described more specifically with reference to examples. The present invention is not limited by the following examples, and can of course be implemented with appropriate modifications within a range that can be adapted to the above-described gist. Included in the range. In addition, the analysis or evaluation in an Example and a comparative example was performed as follows.

<Measuring method of metal ratio in composite metal oxide>
Using a scanning X-ray fluorescence analyzer (ZSX100e: 4.0 kW Rh tube manufactured by RIGAKU), quantitative analysis was performed by performing a theoretical calculation by a thin film FP method (fundamental parameter method). The cerium oxide, copper oxide, zirconium oxide, and iron oxide in the composite metal oxide were assumed to have a composition of CeO2, CuO, Zr2O3, and Fe2O3, respectively, and the respective contents (weight fractions) were calculated.

<Measurement method of BET specific surface area>
About 100 mg of a sample was taken, vacuum-dried at 120 ° C. for 12 hours, and then weighed. Using a high-functional specific surface area / pore distribution measuring device (“ASAP2020” manufactured by Micromeritics), the adsorption amount of nitrogen gas at the boiling point (-195.8 ° C.) of liquid nitrogen is 0.02 to 0.95. 40 points were measured while gradually increasing in the above range, and an adsorption isotherm of the sample was prepared. Using analysis software (“ASAP 2020 V3.04” manufactured by Micromeritics), the results at a relative pressure of 0.02 to 0.15 were BET-plotted to obtain the BET specific surface area (m ² / g) per weight.

<Method for measuring acetaldehyde removal performance / Method for detecting volatile gas components in Tedlar bag>
A 5 L Tedlar bag containing 100 ppm of acetaldehyde at a temperature of 25 ° C. and a humidity of 50 RH% and a sample of 50 mg were sealed and placed in an oven heated to 80 ° C. The Tedlar bag was shaken appropriately so that the sample contained therein and the air containing acetaldehyde sufficiently contacted and reacted. The acetaldehyde gas concentration in the Tedlar bag after 100 minutes was measured with a gas chromatograph with FID, and the residual acetaldehyde ratio [%] in the Tedlar bag was determined from the change in the concentration of acetaldehyde before and after the reaction. The residual rate is the following formula (i);
Acetaldehyde residual ratio (%) = {(Acetaldehyde concentration in Tedlar bag after 100 minutes) / (Acetaldehyde concentration in Tedlar bag before reaction (100 ppm))} × 100 (i)
Calculated based on Therefore, it can be said that the lower the acetaldehyde residual rate in the Tedlar bag after 100 minutes, the higher the performance. Note that the volatile gas components other than acetaldehyde in the Tedlar bag were also measured by a gas chromatograph in the same manner as acetaldehyde.

<Example 1>
Copper (II) nitrate trihydrate (manufactured by Nacalai Tesque) 0.7 g and cerium nitrate (III) hexahydrate (manufactured by Nacalai Tesque) 5 g were dissolved in 75 ml of ion-exchanged water and 28% with stirring. Aqueous ammonia was added slowly until the solution pH was 10. After stirring for 1 hour at room temperature, the precipitate collected by filtration and washing was vacuum-dried at 120 ° C. for 6 hours to remove excess water. And the catalyst sample was obtained by baking the dried deposit in the air for 650 degreeC and 5 hours. About the obtained catalyst sample, the BET specific surface area, the acetaldehyde removal performance, the metal mixing ratio of copper and cerium, and volatile gas components other than acetaldehyde in the Tedlar bag were measured.

<Example 2>
While stirring 1.2 g of copper (II) nitrate trihydrate (Nacalai Tesque) and 4.1 g of cerium (III) nitrate hexahydrate (Nacalai Tesque) in 75 ml of ion-exchanged water, stirring 28% aqueous ammonia was slowly added until the solution pH was 10. After stirring for 1 hour at room temperature, the precipitate collected by filtration and washing was vacuum-dried at 120 ° C. for 6 hours to remove excess water. And the catalyst sample was obtained by baking the dried deposit in the air for 650 degreeC and 5 hours. About the obtained catalyst sample, the BET specific surface area, the acetaldehyde removal performance, the metal mixing ratio of copper and cerium, and volatile gas components other than acetaldehyde in the Tedlar bag were measured.

<Example 3>
While stirring 1.8 g of copper (II) nitrate trihydrate (manufactured by Nacalai Tesque) and 3.2 g of cerium nitrate (III) hexahydrate (manufactured by Nacalai Tesque) in 75 ml of ion-exchanged water, stirring the solution. 28% aqueous ammonia was slowly added until the solution pH was 10. After stirring for 1 hour at room temperature, the precipitate collected by filtration and washing was vacuum-dried at 120 ° C. for 6 hours to remove excess water. And the catalyst sample was obtained by baking the dried deposit in the air for 650 degreeC and 5 hours. About the obtained catalyst sample, the BET specific surface area, the acetaldehyde removal performance, the metal mixing ratio of copper and cerium, and volatile gas components other than acetaldehyde in the Tedlar bag were measured.

<Comparative Example 1>
While stirring 0.3 g of copper (II) nitrate trihydrate (manufactured by Nacalai Tesque) and 5.7 g of cerium (III) nitrate hexahydrate (manufactured by Nacalai Tesque) in 75 ml of ion-exchanged water, stirring the mixture 28% aqueous ammonia was slowly added until the solution pH was 10. After stirring for 1 hour at room temperature, the precipitate collected by filtration and washing was vacuum-dried at 120 ° C. for 6 hours to remove excess water. And the catalyst sample was obtained by baking the dried deposit in the air for 650 degreeC and 5 hours. About the obtained catalyst sample, the BET specific surface area, the acetaldehyde removal performance, the metal mixing ratio of copper and cerium, and volatile gas components other than acetaldehyde in the Tedlar bag were measured.

<Comparative example 2>
Copper (II) nitrate trihydrate (manufactured by Nacalai Tesque) (3.5 g) was dissolved in 75 ml of ion-exchanged water, and 28% aqueous ammonia was slowly added with stirring until the solution pH reached 10. After stirring at room temperature for 1 hour, the solution was vacuum-dried and further calcined in air at 650 ° C. for 5 hours to obtain a sample. About the obtained sample, BET specific surface area, acetaldehyde removal performance, and volatile gas components other than acetaldehyde in a Tedlar bag were measured.

<Comparative Example 3>
6.3 g of cerium (III) nitrate hexahydrate (manufactured by Nacalai Tesque) was dissolved in 75 ml of ion-exchanged water, and 28% aqueous ammonia was slowly added with stirring until the pH of the solution reached 10. After stirring for 1 hour at room temperature, the precipitate collected by filtration and washing was vacuum-dried at 120 ° C. for 6 hours to remove excess water. And the sample was obtained by baking the dried deposit in air at 650 degreeC for 5 hours. About the obtained sample, BET specific surface area, acetaldehyde removal performance, and volatile gas components other than acetaldehyde in a Tedlar bag were measured.

<Comparative example 4>
A sample was obtained by mixing 5.5 mg of copper oxide prepared in Comparative Example 1 and 50 mg of cerium oxide prepared in Comparative Example 2 in a mortar for 30 minutes. About the obtained sample, acetaldehyde removal performance and volatile gas components other than acetaldehyde in a tedlar bag were measured.

<Comparative Example 5>
50 mg of copper oxide prepared in Comparative Example 1 and 50 mg of cerium oxide prepared in Comparative Example 2 were mixed in a mortar for 30 minutes to obtain a sample. About the obtained sample, acetaldehyde removal performance and volatile gas components other than acetaldehyde in a tedlar bag were measured.

<Comparative Example 6>
1.9 g of zirconium oxynitrate dihydrate (manufactured by Nacalai Tesque) and 3.2 g of cerium (III) nitrate hexahydrate (manufactured by Nacalai Tesque) were dissolved in 75 ml of ion-exchanged water and stirred with 1M water. Aqueous sodium oxide was added slowly until the solution pH was 10. After stirring at room temperature for 18 hours, the solution was heated at 80 ° C. for 2 hours, and the precipitate was filtered and washed. The obtained precipitate was dried at 110 ° C. overnight and then calcined in air at 400 ° C. for 4 hours to obtain a sample. About the obtained sample, BET specific surface area, acetaldehyde removal performance, the metal mixing ratio of zirconium and cerium, and volatile gas components other than acetaldehyde in the Tedlar bag were measured.

<Comparative Example 7>
Iron nitrate (III) nonahydrate (Wako Pure Chemical Industries, Ltd.) 1.2 g and cerium nitrate (III) hexahydrate (Nacalai Tesque, Inc.) 5 g were dissolved in 75 ml of ion-exchanged water and stirred for 28 % Aqueous ammonia was slowly added until the solution pH was 10. After stirring for 1 hour at room temperature, the precipitate collected by filtration and washing was vacuum-dried at 120 ° C. for 6 hours to remove excess water. And the sample was obtained by baking the dried deposit in air at 650 degreeC for 5 hours. About the obtained sample, BET specific surface area, acetaldehyde removal performance, the metal mixing ratio of iron and cerium, and volatile gas components other than acetaldehyde in the Tedlar bag were measured.

The low temperature removal catalyst for aldehydes and the method for removing aldehyde gas of the present invention can express satisfactory removal performance in a low temperature region at low cost and have low impact on environmental pollution and human body, so that it can be used in a wide range of fields. It can be used in and contributes to the industry.

Claims (8)

  A composite metal catalyst containing cerium and copper, wherein the composite metal oxide contains 4 to 20% by mass of copper in terms of CuO.   The aldehyde removal catalyst according to claim 1, which has an aldehyde removal performance at a low temperature of 100 ° C or lower.   The aldehyde removal catalyst according to claim 1 or 2, wherein ethanol is not produced when air containing 100 ppm of acetaldehyde is sealed in the presence of an aldehyde removal catalyst and heated at 80 ° C for 100 minutes. The aldehyde low temperature removal catalyst according to any one of claims 1 to 3, wherein the BET specific surface area of the composite metal oxide containing cerium and copper is 30 m ² / g or more.   The method for producing an aldehyde removal catalyst according to any one of claims 1 to 4, wherein a compound obtained by coprecipitation from cerium salt and copper salt is calcined.   6. The method for producing an aldehyde removal catalyst according to claim 5, wherein the cerium salt and the copper salt are both nitrates.   The aldehydes according to any one of claims 1 to 5, wherein the aldehyde removal catalyst according to any one of claims 1 to 5 is brought into contact with an aldehyde gas to undergo oxidative decomposition, and the decomposition product of the aldehyde gas is adsorbed and removed by the catalyst. Gas removal method.   A method for removing aldehyde gas, wherein the aldehyde gas is removed by low-temperature heating within a range of 40 ° C to 100 ° C using the aldehyde removal catalyst according to any one of claims 1 to 4.