JP6225807B2 - VOC decomposition removal catalyst, method for producing the same, and VOC decomposition removal method using the same - Google Patents

Description

  The present invention relates to a VOC decomposition / removal catalyst, a production method thereof, and a VOC decomposition / removal method using the same.

  VOC is an abbreviation for volatile organic compounds, and a volatile organic compound is a general term for organic compounds that are volatile and gaseous in the atmosphere. Examples of VOCs include toluene, xylene, benzene, ethyl acetate, methanol, and dichloromethane, and are used in a wide range of applications such as paints, adhesives, printing inks, and cleaning agents.

  On the other hand, air pollution due to photochemical oxidants is still serious, and in urban areas such as Tokyo and Nagoya, the concentration of photochemical oxidants does not meet the environmental standard value, and there is concern about the effect on the human body. The cause of such an optical oxidant includes various things such as exhaust gas discharged from an internal combustion engine such as an automobile, and the VOC is one of the causes of the generation of the optical oxidant. Therefore, in recent years, the amount of VOC emissions into the atmosphere tends to be severely regulated, and in particular, in factories or the like that are fixed sources of VOC, measures to further reduce VOC emissions are required.

  VOC treatment technology for reducing VOC emissions includes, for example, an adsorption method in which VOC is adsorbed on a porous body such as activated carbon or metal oxide and recovered, a catalyst method in which VOC is oxidatively decomposed using a catalyst, and VOC There are known a combustion method in which combustion is performed at a high temperature and oxidative decomposition, a catalytic combustion method in which the catalyst method and the combustion method are combined, and the like. A photocatalyst is a typical catalyst used in the catalyst method, but it has a problem that the processing speed is slow and the amount of VOC that can be decomposed is small. Further, examples of the catalyst used in the catalytic combustion method include a catalyst in which a noble metal such as platinum or palladium is supported on a honeycomb-like or pellet-like carrier. It was difficult to procure noble metals.

In order to solve such problems, H.C. Einaga et al. , J .; Catalysis 227 (2004) p. 304-312 (Non-patent Document 1) discloses a manganese oxide-supported alumina catalyst prepared by impregnating an aqueous solution containing manganese (II) acetate tetrahydrate with γ-Al ₂ O ₃ . However, the manganese oxide-supported alumina catalyst described in Non-Patent Document 1 does not always have sufficient VOC decomposition removal performance.

  Japanese Patent Laid-Open No. 6-142455 (Patent Document 1) discloses that a catalyst is selected from oxides of Mn and Ni as a first component in a method in which an odorous component is catalytically oxidized and decomposed on a catalyst using ozone. There has been disclosed a deodorizing method characterized in that at least one or more of those composed of an oxide of Al is used as the second component. However, even with the deodorization method and the deodorization catalyst disclosed in Patent Document 1, the VOC decomposition and removal performance is not always sufficient.

  Further, JP-A-53-30978 (Patent Document 2) discloses an ozone generator, a catalytic reaction tank through which a mixed gas obtained by mixing malodorous gas with ozone generated by the ozone generator, and this catalyst. In a deodorizing apparatus comprising a heating apparatus for heating a reaction tank, as a catalyst of the catalytic reaction tank, at least one metal or metal oxide of manganese, iron, nickel, cobalt, chromium, molybdenum, lead, tungsten, copper, vanadium There has been disclosed a deodorizing apparatus in which a deodorizing catalyst comprising a product supported on activated alumina is arranged. However, even in the deodorization apparatus disclosed in Patent Document 2, the VOC decomposition and removal performance is not always sufficient.

  As described above, none of the catalysts disclosed in Non-Patent Document 1, Patent Document 1, and Patent Document 2 have sufficient VOC decomposition removal performance.

  However, in recent years, the required characteristics for the VOC decomposition / removal catalyst have been increasingly increased, and a VOC decomposition / removal catalyst having higher VOC decomposition / removal performance has been demanded.

JP-A-6-142455 Japanese Patent Laid-Open No. 53-30978

H. Einaga et al. , J .; Catalysis 227 (2004) p. 304-312

  The present invention has been made in view of the above-mentioned problems of the prior art, and provides a VOC decomposition / removal catalyst having excellent VOC decomposition / removal performance, a method for producing the same, and a VOC decomposition / removal method using the same. With the goal.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors have adopted a so-called sol-supporting method when supporting manganese on an alumina support, and an average that cannot be obtained by a conventional impregnation method. A predetermined amount of manganese can be supported on an alumina support having a small primary particle size of 6 to 15 nm. According to the VOC decomposition / removal catalyst of the present invention obtained thereby, VOC decomposition / removal significantly superior to conventional ones is achieved. It was found that performance was demonstrated. Moreover, it has been found that such VOC decomposition / removal performance is remarkably improved when ozone is used in combination, and the present invention has been completed.

  That is, the VOC decomposition / removal catalyst of the present invention comprises an alumina support having an average primary particle size of 6 to 15 nm and manganese supported on the alumina support, and the amount of manganese supported is the alumina support and It is 0.5 to 8.0 mass% with respect to the total amount with the said manganese.

  In the VOC decomposition / removal catalyst of the present invention, the average primary particle size of the alumina support is 8 to 13 nm, and the supported amount of manganese is 1.0 to 5.5 with respect to the total amount of the alumina support and manganese. It is preferably 0% by mass.

  The method for producing a VOC decomposition / removal catalyst of the present invention comprises the steps of preparing an alumina sol having an average primary particle size of 5 to 40 nm, contacting the alumina sol with a manganese salt aqueous solution, and the amount of manganese supported after firing is A step of obtaining a gelled product in which an amount of manganese of 0.5 to 8.0% by mass with respect to the total amount of manganese is supported on an alumina sol; and the gelled product at a temperature within a range of 300 to 900 ° C. And a step of obtaining the VOC decomposition / removal catalyst of the present invention by calcination.

  In the method for producing a VOC decomposition / removal catalyst of the present invention, in the step of obtaining the VOC decomposition / removal catalyst, the gelled product obtained by the step of obtaining the gelled product before the calcination is within a range of 50 to 200 ° C. It is preferable to include a step of drying at a temperature of 5 to remove moisture to obtain a dried product.

  The VOC decomposition / removal method of the present invention is characterized in that the VOC is decomposed and removed by bringing a gas containing VOC into contact with the VOC decomposition / removal catalyst of the present invention in the presence of ozone.

  In the VOC decomposition and removal method of the present invention, it is preferable that the concentration (C1 conversion) ratio (B / A) of the ozone (B) to the VOC (A) of the gas containing the VOC is 0.1 to 4. .

  Although the reason why the excellent VOC decomposition / removal performance is exhibited by using the VOC decomposition / removal catalyst of the present invention is not necessarily clear, the present inventors infer as follows.

  That is, in the method for producing a VOC decomposition / removal catalyst of the present invention, by adopting a so-called sol-supporting method in which a gelled product obtained by bringing a manganese salt aqueous solution into contact with an alumina sol having an average primary particle size in a specific range is fired. A VOC decomposition removal catalyst having an excellent VOC decomposition removal performance capable of supporting a predetermined amount of manganese on an alumina support having an average primary particle diameter of 6 to 15 nm, which could not be obtained by a conventional impregnation method. The present inventors infer that the product can be manufactured.

  Further, in the VOC decomposition / removal catalyst of the present invention, the active primary species generated by decomposing ozone into manganese by supporting alumina with an average primary particle size of 6 to 15 nm as a carrier and carrying a predetermined amount of manganese on the carrier. VOC is more highly decomposed and removed by VOC, and further, VOC and ozone are sufficiently dispersed and adsorbed in the alumina carrier, so that the VOC decomposition and removal rate is further improved, and excellent VOC decomposition and removal performance is exhibited. The present inventors speculate. In the VOC decomposition / removal catalyst of the present invention, manganese itself acts as an active species on the surface of the alumina support. In the present invention, the supported amount of manganese is based on the total amount of the alumina support and manganese. By supporting 0.5 to 8.0% by mass of manganese on the alumina carrier, the contact between VOC and ozone and manganese is improved, and the VOC decomposition / removal is further promoted, and particularly excellent VOC decomposition / removal is achieved. The present inventors speculate that the performance is exhibited.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the VOC decomposition removal catalyst which has the outstanding VOC decomposition removal performance, its manufacturing method, and the VOC decomposition removal method using the same.

It is a graph which shows the toluene removal rate of the catalyst for VOC decomposition | disassembly removal obtained in Examples 1-3 and the catalyst for comparison obtained in Comparative Examples 1-8. It is a graph which shows the relationship between the load of manganese (Mn) and the toluene removal rate in the catalyst for VOC decomposition | disassembly removal obtained in Examples 1-3 and the catalyst for comparison obtained in Comparative Examples 2-3. It is a graph which shows the relationship between the average primary particle diameter of the alumina support | carrier in the catalyst for VOC decomposition | disassembly removal obtained in Examples 1-3, and the catalyst for comparison obtained in Comparative Examples 4-6, and the toluene removal rate.

  Hereinafter, the present invention will be described in detail with reference to preferred embodiments thereof.

  First, the VOC decomposition removal catalyst of the present invention will be described. The VOC decomposition / removal catalyst of the present invention comprises an alumina support having an average primary particle size of 6 to 15 nm and manganese supported on the alumina support, and the supported amount of manganese is the alumina support and the manganese. It is characterized by being 0.5 to 8.0 mass% with respect to the total amount.

  In the present invention, VOC is an abbreviation for volatile organic compounds, and the volatile organic compound is volatile and volatilizes in the atmosphere (normal temperature and pressure) to become a gas. A general term for organic compounds. Examples of the VOC include toluene, xylene, benzene, ethyl acetate, ethylbenzene, styrene, ethanol, acetaldehyde, formaldehyde, and the like. The VOC decomposition / removal catalyst of the present invention is a catalyst capable of removing VOC from a VOC-containing gas containing such VOC by decomposing VOC, and preferably oxidatively decomposes VOC. Is a catalyst capable of removing VOC from a VOC-containing gas. The VOC decomposition removal catalyst of the present invention is particularly excellent in the decomposition removal performance of toluene, benzene, xylene, ethylbenzene, and styrene among the VOCs. Furthermore, the VOC decomposition / removal catalyst of the present invention is particularly excellent as a VOC decomposition / removal catalyst for decomposing and removing VOC in the presence of ozone.

(Alumina carrier)
The alumina carrier according to the present invention needs to be a carrier mainly composed of alumina (Al ₂ O ₃ ). Such an alumina carrier containing alumina as a main component is not particularly limited except that it contains alumina as a main component. Here, “mainly composed of alumina” means that the carrier is composed only of alumina, or is composed mainly of alumina and includes other components. As other components, other compounds used as a carrier for an exhaust gas purifying catalyst for this type of application can be used. In the latter case, the content of alumina in the carrier is preferably 50% by mass or more, more preferably 70% by mass or more, and 90% by mass or more with respect to 100% by mass of the total mass of the carrier. Is particularly preferred. When the content of alumina in such a carrier is less than the lower limit, the VOC decomposition / removal performance of the supported manganese tends to decrease.

  The alumina in such a carrier is selected from the group consisting of boehmite type, pseudo boehmite type, χ type, κ type, ρ type, η type, γ type, pseudo γ type, δ type, θ type and α type. A group consisting of γ-type, pseudo-γ-type, δ-type, and θ-type from the viewpoint that it is inexpensive and has a large specific surface area and tends to adsorb gas. It is preferable to use at least one kind of alumina selected from the group consisting of γ-alumina having high activity.

  The alumina carrier used in the present invention needs to have an average primary particle size of 6 to 15 nm. If the average primary particle size of the alumina support is less than the lower limit, the gas diffusion performance is lowered and the VOC decomposition / removal performance becomes insufficient. On the other hand, when the upper limit is exceeded, there arises a problem that the gas adsorption performance is lowered and the VOC decomposition / removal performance is lowered. The average primary particle size is preferably 7 to 13 nm, particularly preferably 8 to 13 nm, from the viewpoint of securing a high specific surface and efficiently adsorbing large molecules. The average primary particle size of such a carrier can be measured by calculating from the line width of the powder X-ray diffraction peak using the Scherrer's equation using an X-ray diffractometer. . In addition, the average primary particle size of such a carrier may be obtained by measuring any 100 or more particles with a transmission electron microscope (TEM) to determine the particle size of each particle and averaging the values. it can. In addition, such a particle diameter means the maximum diameter of the cross section of a particle, and when the cross section of the particle is not circular, the diameter is the maximum circumscribed circle of the cross section of the particle.

In addition, the alumina support according to the present invention is preferably a porous body from the viewpoint that a sufficient specific surface area can be obtained. Specifically, the specific surface area determined by a nitrogen adsorption method is 10 m ² / g or more ( More preferably, it is 50-500 m < ² > / g). When the specific surface area is less than the lower limit, the performance of adsorbing the VOC-containing gas is lowered, and the VOC decomposition / removal performance tends to be lowered.

  Furthermore, in the alumina support | carrier which concerns on this invention, it is preferable that the center pore diameter calculated | required by the nitrogen adsorption method is 2-100 nm, and it is more preferable that it is 5-50 nm. When the central pore diameter is less than the lower limit, the VOC-containing gas and ozone are not sufficiently diffused into the pores of the alumina carrier, and the decomposition and removal performance of VOCs on the outer surface and pores of the carrier tends to be lowered. On the other hand, if the upper limit is exceeded, the ability to adsorb the VOC-containing gas tends to be lowered, and the VOC decomposition / removal performance tends to be lowered.

Moreover, in the alumina support | carrier which concerns on this invention, it is preferable that the pore volume calculated | required by the nitrogen adsorption method is 0.3-1.5 cm < ³ > / g. If the pore volume is less than the lower limit, the gas diffusion performance tends to decrease and the VOC decomposition / removal performance tends to decrease. On the other hand, if the upper limit is exceeded, the gas adsorption performance decreases and the VOC decomposition / removal performance decreases. There is a tendency.

  In the present invention, the specific surface area, the center pore diameter and the pore volume of the porous body can be determined from the nitrogen adsorption isotherm obtained by the nitrogen adsorption method by the BET isotherm adsorption equation. That is, for example, first, the VOC decomposition / removal catalyst is cooled to liquid nitrogen temperature (−196 ° C.), nitrogen gas is introduced, the adsorption amount is determined by a constant volume method or a gravimetric method, and then the nitrogen gas to be introduced is determined. The pressure is gradually increased, and the adsorption amount of nitrogen gas with respect to each pressure is plotted to obtain an adsorption isotherm. The specific surface area can be calculated as a BET specific surface area from the adsorption isotherm using a BET isotherm adsorption equation. The central pore diameter is the pore at the maximum peak of the pore diameter distribution curve obtained by adopting a calculation method such as Cranston-Inklay method, Pollimore-Heal method, BJH method using the adsorption isotherm. It can be calculated as a value obtained by doubling the radius. Furthermore, the pore volume can be determined from the nitrogen adsorption amount when the relative pressure reaches the maximum value using the nitrogen adsorption isotherm.

(manganese)
Manganese (Mn) according to the present invention is manganese as a metal active species supported on an alumina support. Such manganese is not particularly limited except that it is manganese. In the VOC decomposition / removal catalyst of the present invention, by supporting manganese on the alumina carrier, VOC and ozone are sufficiently dispersed and adsorbed in the alumina carrier, so that the VOC decomposition / removal rate is further improved. In the VOC decomposition removal reaction, the VOC removal performance of the catalyst is exhibited by the contact of the gas containing VOC and Mn which is the active species of the catalyst, and the excellent VOC decomposition removal performance is exhibited.

  Manganese (Mn) used in the present invention is required to have a supported amount of 0.5 to 8.0% by mass with respect to the total amount of the alumina support and manganese. In both cases where the supported amount of manganese (Mn) is less than the lower limit and exceeds the upper limit, sufficient VOC decomposition / removal performance is not exhibited, and the VOC removal rate decreases. Further, the amount of manganese (Mn) supported is preferably 0.75 to 5.0% by mass, and 1.0 to 2.5% by mass with respect to the total amount of the alumina support and the manganese. % Is more preferable. If the supported amount is less than the lower limit, the active point of the catalytic reaction tends to be insufficient, and the VOC decomposition / removal performance tends to decrease. On the other hand, if the upper limit is exceeded, manganese particles become coarse and contact area with the gas Tends to decrease and the VOC decomposition / removal performance tends to decrease. Such manganese loading is, for example, inductively coupled plasma (ICP) emission analysis, electron probe microanalyzer (EPMA) analysis, XRF analysis (XRF: X-ray Fluorescence). It can be confirmed by elemental analysis using (Analysis).

  Further, such manganese is preferably in the form of particles, the average primary particle diameter is more preferably 1.0 to 50 nm, and further preferably 2.0 to 20 nm. If the average primary particle size is less than the lower limit, the affinity with the alumina support tends to be too strong and does not function sufficiently as an active site. On the other hand, if the upper limit is exceeded, the contact area with the gas decreases. However, the VOC decomposition / removal performance tends to decrease.

  In such a VOC decomposition / removal catalyst of the present invention, the manganese supported on the alumina support is preferably manganese in a manganese (IV) oxide state. It should be noted that the manganese is a chemical species (for example, manganese metal) between the manganese metal-like state and the manganese oxide (IV) -like state due to changes in the atmosphere environment of the manganese (eg, change in atmosphere such as temperature and oxidation-reduction). Transition to a metal manganese-like state, a manganese (0) state, a manganese (II) -like state, a manganese (II) state, a manganese oxide (II) -like state, a manganese oxide (IV) -like state, manganese dioxide).

(VOC decomposition removal catalyst)
As the VOC decomposition / removal catalyst of the present invention, a precious metal such as Pt, Pd, Rh, Ir, Au, Ag, Ru, Os, Ni, Co, Fe, Cu, etc., as long as the effects of the present invention are not impaired. However, since the VOC decomposition / removal catalyst of the present invention can exhibit sufficient reaction activity without containing the noble metal, from the viewpoint of reducing the production cost, the noble metal may be contained. It is preferable not to contain.

  The usage form of the VOC decomposition / removal catalyst of the present invention is not particularly limited, and for example, a powdered catalyst may be used as it is, or a powdered catalyst may be formed into a pellet by a conventional method, A slurry containing a powdered catalyst may be coated on another substrate and used. In such molding, the metal oxide support according to the present invention may be supported after manganese chloride is formed, and the metal oxide support according to the present invention may be molded and then manganese is formed. Chloride may be supported.

  The other substrate is not particularly limited, and a monolith carrier substrate (honeycomb filter, high-density honeycomb, etc.), foam filter substrate, pellet-shaped substrate, plate-shaped substrate and the like are preferably employed. Further, the material of the base material is not particularly limited, and a base material made of a ceramic such as cordierite, silicon carbide, mullite, or a base material made of a metal such as stainless steel including chromium and aluminum is suitably employed. .

[Method for producing catalyst for removing VOC decomposition]
Next, a method for producing the VOC decomposition / removal catalyst of the present invention will be described. The method for producing a VOC decomposition / removal catalyst according to the present invention is a method for producing a VOC decomposition / removal catalyst for decomposing and removing VOC containing VOC, and preparing an alumina sol having an average primary particle size of 5 to 40 nm. (Alumina sol preparatory step) and a manganese salt aqueous solution in contact with the alumina sol, and the amount of manganese supported after firing is 0.5 to 8.0% by mass with respect to the total amount of the alumina support and the manganese A step of obtaining a gelled product supported on alumina sol (gelation step), and a step of obtaining the VOC decomposition / removal catalyst of the present invention by firing the gelled product at a temperature in the range of 300 to 900 ° C. Firing step).

(Alumina sol preparation process)
In the method for producing a VOC decomposition removal catalyst of the present invention, first, an alumina sol as an alumina carrier source is prepared. A method for preparing the alumina sol is not particularly limited, and a known method can be appropriately employed. As such an alumina sol, a commercially available product may be used.

  The alumina sol prepared in the alumina sol preparation step according to the present invention needs to be an alumina sol having an average primary particle size of 5 to 40 nm. When the average primary particle size of the alumina sol is less than the lower limit, the thermal stability during firing becomes insufficient. On the other hand, when the upper limit is exceeded, there arises a problem that the specific surface area decreases. The average primary particle size is preferably 7.5 to 30 nm, and particularly preferably 10 to 20 nm, from the viewpoint of increasing the specific surface area and ensuring the stability during firing. The average primary particle size of such an alumina sol can be measured by, for example, a dynamic light scattering method.

  As a method for preparing such an alumina sol, specifically, a method of obtaining an alumina sol by suspending ultrafine aluminum oxide in water, a hydrolyzate of an aluminum alkoxide, a basic aluminum salt and an acid, an alkali or an acid Examples thereof include a method of obtaining an alumina sol by adding an acid to a reaction product of an aluminum salt and a base and peptizing to obtain an alumina sol, and a method of obtaining an alumina sol by reacting a metal aluminum powder with a dilute acid aqueous solution.

  Moreover, as such an alumina sol, the alumina sol solid content is preferably 5 to 60% by mass, and more preferably 10 to 30% by mass. If the alumina sol solid content is less than the lower limit, it takes a long time to dry, and the manufacturing cost tends to increase. On the other hand, if the upper limit is exceeded, the sol tends to aggregate and the characteristics of the catalyst tend to become unstable. It is in.

(Gelification process)
Next, a manganese salt aqueous solution is brought into contact with the alumina sol obtained in the alumina sol preparation step, and the amount of manganese supported after firing becomes 0.5 to 8.0 mass% with respect to the total amount of the alumina support and the manganese. A gelled product in which an amount of manganese is supported on alumina sol is obtained (gelation step). In such a method for producing a VOC decomposition / removal catalyst of the present invention, the method for bringing an alumina sol into contact with an aqueous manganese salt solution for gelation is not particularly limited except the above, and a known method can be appropriately employed. .

  In such a gelation step, the manganese salt aqueous solution is not particularly limited, and a manganese salt aqueous solution such as manganese nitrate, manganese acetate, manganese sulfate, manganese chloride, or the like can be used. Among these, manganese nitrate aqueous solution and manganese acetate are particularly preferable in order to avoid mixing of sulfur and chlorine.

  The method of bringing the aqueous manganese salt solution into contact with the alumina sol is not particularly limited, and a known method such as a method of adding the aqueous solution to the alumina sol and mixing it can be appropriately employed.

  The amount and concentration of the manganese salt aqueous solution used in the gelation step of the present invention is such that the amount of manganese supported after firing is 0.5 to 8.0% by mass with respect to the total amount of the alumina carrier and manganese. It is necessary that the amount and concentration be sufficient to support manganese. For example, when the total amount of manganese in the manganese salt aqueous solution used is supported on alumina (the total amount of manganese charged is supported), the amount of manganese in the manganese salt aqueous solution (in metal conversion) / (alumina component amount + the amount of manganese) ) Is adjusted so that the desired manganese content is within the range of 0.5 to 8.0 mass% after firing.

  In addition, as a liquid quantity of such manganese salt aqueous solution, it is preferable that it is the range of 0.5-40 times of alumina support | carrier mass, for example, and 1-20 times is more preferable. Moreover, as a density | concentration of such manganese salt aqueous solution, it is preferable that it is the range of 1-30 mass% with respect to an alumina support | carrier mass, for example, and 5-20 mass% is more preferable.

(Baking process)
Next, the VOC decomposition removal catalyst of the present invention is obtained by calcining the gelled product obtained in the gelation step at a temperature in the range of 300 to 900 ° C. (calcination step). In such a method for producing a VOC decomposition / removal catalyst of the present invention, the method for firing the gelated product obtained in the gelation step is not particularly limited except for the temperature (heating temperature), and a known method is used. It can be adopted as appropriate.

  In such a firing step, the heating temperature (firing temperature) needs to be within a range of 300 to 900 ° C. When the heating temperature is less than the lower limit, the average primary particle size of the alumina support tends to be outside the predetermined range and the VOC decomposition and removal performance of the catalyst tends to be reduced. On the other hand, when the upper limit is exceeded, manganese can be an oxide. The VOC decomposition and removal performance of the catalyst tends to decrease. Further, from the viewpoint of forming an alumina phase having a high specific surface area, such a heating temperature is preferably within a range of 400 to 700 ° C, and more preferably within a range of 450 to 650 ° C.

  In addition, the heating time in such a baking step is not particularly limited, and since it varies depending on the temperature of the baking, it cannot be generally stated, but is preferably in the range of 10 minutes to 12 hours, 30 Minute to 6 hours are more preferable. When the heating time is less than the lower limit, the average primary particle size of the alumina support is outside the predetermined range, and the VOC decomposition / removal performance of the catalyst tends to decrease. On the other hand, if the upper limit is exceeded, thermal degradation proceeds, manganese tends to grow and the dispersibility on the surface of the carrier tends to decrease, and / or the VOC decomposition and removal performance of the catalyst from which manganese can be converted into an oxide decreases. There is a tendency.

  Furthermore, as the heating temperature and heating time in such a firing step, it is preferable to perform the heat treatment in a heating temperature range of 300 to 900 ° C. and a heating time range of 10 minutes to 12 hours. Moreover, it is more preferable to perform the heat treatment in the range of the heating temperature of 400 to 700 ° C. and the heating time of 30 minutes to 6 hours.

  Further, in the firing step of the method for producing a VOC decomposition / removal catalyst of the present invention, the gelled product obtained by the gelation step is dried at a temperature within a range of 50 to 200 ° C. before the firing. It is preferable to include a step of removing moisture to obtain a dry body (drying step). The method for drying the gelled product obtained in the gelation step to remove moisture is not particularly limited, and a known method can be appropriately employed. The heating temperature in such a drying step is preferably a temperature within the range of 50 to 200 ° C, and more preferably within the range of 80 to 150 ° C. When the heating temperature is less than the lower limit, the drying time tends to be remarkably long. On the other hand, when the heating temperature is higher than the upper limit, the VOC decomposition / removal performance of the resulting catalyst becomes poor. Further, the heating time in such a drying step is not particularly limited and cannot be generally described because it varies depending on the temperature of the drying, but is preferably within a range of 30 minutes to 48 hours. More preferably, it is -24 hours. When the heating time is less than the lower limit, a preferable alumina phase or manganese state tends to be difficult to be formed. On the other hand, when the upper limit is exceeded, the alumina surface area decreases or the manganese particles tend to become coarse.

  According to the method for producing a VOC decomposition / removal catalyst of the present invention, the average primary particle diameter of the alumina support is 6 to 15 nm and the VOC decomposition / removal performance is excellent without coarsening the alumina primary particles. It becomes possible to produce a VOC decomposition removal catalyst.

[VOC decomposition and removal method]
Next, the VOC decomposition and removal method of the present invention will be described. The VOC decomposition / removal method of the present invention is a method of decomposing VOC by bringing a gas containing VOC into contact with the VOC decomposition / removal catalyst of the present invention in the presence of ozone.

  Examples of the gas containing VOC include air containing VOC. In the VOC decomposition and removal method of the present invention, the concentration of VOC in the gas is preferably 0.05 ppm or more, and more preferably 0.1 to 100 ppm. If the VOC concentration is less than the lower limit, the amount of VOC adsorbed on the catalyst tends to be small and the decomposition reaction tends to be suppressed. On the other hand, if the VOC concentration exceeds the upper limit, the amount of VOC adsorbed on the catalyst will be saturated and unreacted. Tend to be released.

  There is no particular limitation on the method of contacting the VOC-containing gas (VOC-containing gas) with the VOC decomposition / removal catalyst in the presence of ozone, and the VOC-containing gas, the VOC decomposition / removal catalyst, and the ozone are mixed together. The VOC-containing gas is packed in the catalyst bed filled with the catalyst for removing the VOC decomposition, even in the case of a batch type in which the gas (ozone-containing gas) is introduced into the reaction vessel and reacted. And the ozone-containing gas may be made to circulate simultaneously from different suppliers, or a mixed gas containing VOC and ozone may be first prepared and circulated through the catalyst bed.

  Examples of the ozone-containing gas and the mixed gas include ozone or air containing VOC and ozone. In the VOC decomposition and removal method of the present invention, the concentration of ozone used in combination with the VOC decomposition and removal catalyst is preferably 5 ppb or more, more preferably 0.1 to 500 ppm in the reaction atmosphere. If the ozone concentration is less than the lower limit, the amount of ozone that reacts tends to decrease, so the VOC decomposition / removal performance tends to decrease. On the other hand, if the ozone concentration exceeds the upper limit, the energy required for ozone generation tends to increase. It is in.

  In such a VOC decomposition and removal method of the present invention, the concentration ratio (B / A, C1 conversion) of the ozone (B) to the VOC (A) of the gas containing the VOC is in the range of 0.1 to 4. It is necessary to be. When the ozone / VOC concentration ratio is less than the lower limit, the amount of ozone that reacts decreases, resulting in insufficient VOC decomposition and removal performance. On the other hand, if the ozone / VOC concentration ratio exceeds the upper limit, the energy required for ozone generation increases, resulting in a problem of high costs. The ozone / VOC concentration ratio is preferably 0.2 to 3 and preferably 0.5 to 2 from the viewpoint of removing VOC using ozone present in the atmosphere. Is particularly preferred.

Moreover, when distribute | circulating the said mixed gas, as a flow volume and flow velocity of the mixed gas to distribute | circulate, 1000-200000 [h < ^-1 >] is preferable as space velocity (SV), and 2000-100000 [h < ^-1 >] is more preferable. . When the space velocity (SV) is less than the lower limit, the apparatus weight and capacity tend to be excessive. On the other hand, when the upper limit is exceeded, the contact time between the gas and the catalyst is shortened and the VOC decomposition / removal performance tends to decrease. It is in.

  Furthermore, the conditions for bringing the VOC-containing gas into contact with the VOC decomposition / removal catalyst can be set as appropriate. However, the contact temperature is such that manganese chloride becomes an oxide and the VOC decomposition / removal performance decreases. From the standpoint of suppressing the deterioration, it is preferably 0 to 200 ° C, and from the viewpoint of suppressing the thermal decomposition of ozone and efficiently decomposing and removing VOC, the temperature is from room temperature (25 ° C) to 200 ° C. Is more preferable.

  Further, the reaction atmosphere in the VOC decomposition / removal method of the present invention is preferably an oxidizing atmosphere, and the oxidizing gas concentration in the reaction atmosphere is preferably 0.1% by volume or more, and 0.1 to 20 volumes. % Is more preferable. When the oxidizing gas concentration is less than the lower limit, the VOC decomposition / removal performance tends to decrease. Examples of the oxidizing gas include oxygen and nitric oxide. One of these may be used alone, or two or more may be used in combination. By such a VOC decomposition and removal method of the present invention, it is possible to remove 22% or more, preferably 25% or more of VOC from the VOC-containing gas.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

Example 1
<Preparation of VOC decomposition removal catalyst>
First, manganese nitrate (Mn (NO ₃ ) ₂ , 6H ₂ O) manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in ion exchange water to prepare an aqueous manganese nitrate solution. Next, 3 g of alumina sol (“AS-520” manufactured by Nissan Chemical Industries Ltd., average particle size of 10 to 20 nm, solid content of 20% by mass) is loaded with manganese on the basis of the total amount of the alumina support and the manganese after firing. 1 g of an aqueous manganese nitrate solution whose concentration was adjusted to 1.0 mass% was added and mixed to obtain a gel mixture (note that the entire amount of manganese charged was supported). Subsequently, the gel-like mixture was heated at 110 ° C. for 12 hours to be dried, and then calcined at 500 ° C. for 1 hour to obtain a VOC decomposition removal catalyst in which manganese was supported on alumina (support). The amount of manganese supported was 1.0% by mass with respect to the total amount of the alumina support and manganese.

<Measurement of average primary particle size of alumina support: X-ray diffraction (XRD) measurement>
For the VOC decomposition removal catalyst obtained in Example 1, the average crystallite size (average primary particle size) of the support (alumina) was measured as follows. First, using the obtained catalyst as a measurement sample, an X-ray diffraction (XRD) pattern of the catalyst support using a powder X-ray diffractometer (manufactured by Rigaku Corporation, Ultimate IV "), step width 0.02 °, diverging slit The measurement was performed under the conditions of 2/3 deg, scattering slit 8, CuKα ray (λ = 0.15418 nm), 40 kV, 40 mA, scan speed 20 deg / min. Based on the diffraction line width of the peak derived from Al ₂ O ₃ (2θ = 36.8 ° -37.2 °) for the catalyst support of the XRD pattern thus obtained, Scherrer's formula:
D = 0.9λ / βcos θ
(In the formula, D represents the crystallite diameter, λ represents the used X-ray wavelength, β represents the diffraction line width of the XRD measurement sample, and θ represents the diffraction angle)
Was calculated to calculate the average crystallite diameter (average primary particle diameter). The obtained results are shown in Table 1.
<Performance evaluation test: VOC decomposition removal rate measurement>
For the VOC decomposition / removal catalyst obtained in Example 1, the VOC decomposition / removal rate was measured as follows for the catalyst performance evaluation. First, the obtained VOC decomposition removal catalyst was molded into pellets having a particle size of 0.5 to 1.0 mm and a bulk density of 0.3 to 0.8 g / cm ³ . 0.5 g of this pellet-shaped catalyst was packed into the catalyst bed of an exhaust gas catalyst evaluation device (Best Instrument Co., Ltd. “CATA-5000-2”) connected to an ozone generator (“OZSD-3000AS” manufactured by Sugawara Jitsugyo Co., Ltd.). . Next, a mixed gas (input gas) containing ozone (130 ppm), oxygen (10 vol%), toluene (270 ppmC (carbon equivalent concentration)), and nitrogen (remainder) was added to the catalyst bed at 75 ° C. and a flow rate of 5 L / min. 30 minutes after flowing the mixed gas through the catalyst bed, the concentration of toluene (THC) in the mixed gas (outgas) before and after passing through the catalyst bed was measured, and the VOC decomposition removal rate (toluene removal) Rate) with the following formula:
VOC decomposition removal rate (%) = {(input gas THC concentration−output gas THC concentration) / input gas THC concentration} × 100
Determined by The obtained results are shown in Table 1.

(Example 2)
1 g of an aqueous manganese nitrate solution was added to the alumina so that the concentration of the manganese nitrate aqueous solution was adjusted so that the amount of manganese supported after firing was 5.0% by mass with respect to the total amount of the alumina support and the manganese. The catalyst for removing VOC decomposition was obtained in the same manner as in Example 1 except that the entire amount of manganese was supported. The amount of manganese supported in the obtained VOC decomposition removal catalyst was 5.0% by mass with respect to the total amount of the alumina support and manganese. With respect to the obtained VOC decomposition removal catalyst, the average crystallite size (average primary particle size) of the support (alumina) was measured in the same manner as in Example 1. The VOC decomposition removal rate was determined in the same manner as in Example 1 except that this VOC decomposition removal catalyst was used. The obtained results are shown in Table 1.

(Example 3)
1 g of an aqueous manganese nitrate solution adjusted so that the amount of manganese supported after firing was 7.5% by mass with respect to the total amount of the alumina support and manganese was added to the alumina. The catalyst for removing VOC decomposition was obtained in the same manner as in Example 1 except that the entire amount of manganese was supported. The amount of manganese supported in the obtained VOC decomposition removal catalyst was 7.5% by mass with respect to the total amount of the alumina support and manganese. With respect to the obtained VOC decomposition removal catalyst, the average crystallite size (average primary particle size) of the support (alumina) was measured in the same manner as in Example 1. The VOC decomposition removal rate was determined in the same manner as in Example 1 except that this VOC decomposition removal catalyst was used. The obtained results are shown in Table 1.

(Comparative Example 1)
Manganese dioxide powder (MnO ₂ , “CMD-K200” manufactured by Chuo Electric Industry Co., Ltd.) was used as a catalyst for comparison. The VOC decomposition removal rate of this comparative catalyst was measured in the same manner as in Example 1. The obtained results are shown in Table 1.

(Comparative Example 2)
1 g of an aqueous manganese nitrate solution was added to the alumina so that the concentration of the manganese nitrate aqueous solution was adjusted so that the amount of manganese supported after firing was 0.3 mass% with respect to the total amount of the alumina support and the manganese (note that The catalyst for comparison was obtained in the same manner as in Example 1 except that the entire amount of manganese charged was supported. In addition, the manganese carrying amount of the obtained comparative catalyst was 0.3% by mass with respect to the total amount of the alumina carrier and manganese. For the obtained comparative catalyst, the average crystallite size (average primary particle size) of the support (alumina) was measured in the same manner as in Example 1. Further, the VOC decomposition and removal rate was determined in the same manner as in Example 1 except that this comparative catalyst was used. The obtained results are shown in Table 1.

(Comparative Example 3)
1 g of a manganese nitrate aqueous solution whose concentration was adjusted so that the amount of manganese supported after firing was 10.0% by mass with respect to the total amount of the alumina support and the manganese was added to the alumina (note that The catalyst for comparison was obtained in the same manner as in Example 1 except that the entire amount of manganese charged was supported. In addition, the manganese carrying amount of the obtained comparative catalyst was 10.0% by mass with respect to the total amount of the alumina carrier and manganese. For the obtained comparative catalyst, the average crystallite size (average primary particle size) of the support (alumina) was measured in the same manner as in Example 1. Further, the VOC decomposition and removal rate was determined in the same manner as in Example 1 except that this comparative catalyst was used. The obtained results are shown in Table 1.

(Comparative Example 4)
First, 3 g of alumina sol (“AS-520” manufactured by Nissan Chemical Industries, Ltd., particle size 10 to 20 nm, solid content 20 mass%) was allowed to stand at 100 ° C. for about 1 hour to evaporate to dryness. It was heated at 110 ° C. for 12 hours and dried, and then calcined in air at 500 ° C. for 1 hour to obtain an alumina carrier (powder).

Next, manganese nitrate (Mn (NO ₃ ) ₂ .6H ₂ O) manufactured by Wako Pure Chemical Industries, Ltd.) was dissolved in 2 g of the obtained alumina carrier in ion exchange water, and the amount of manganese supported after firing was alumina. A mixture was obtained by adding 2.5 g of a manganese nitrate aqueous solution whose concentration was adjusted to 1.0 mass% with respect to the total amount of the carrier and the manganese (the whole amount of manganese charged was supported). . Next, this mixture was heated at 110 ° C. for 12 hours to dry, and then calcined at 500 ° C. for 1 hour to obtain a comparative catalyst in which manganese was supported on an alumina carrier. In addition, the manganese carrying amount of the obtained comparative catalyst was 1.0% by mass with respect to the total amount of the alumina carrier and manganese.

  About the obtained comparative catalyst, the average crystallite size (average primary particle size) of the alumina support was measured in the same manner as in Example 1. Further, the VOC decomposition and removal rate was determined in the same manner as in Example 1 except that this comparative catalyst was used. The obtained results are shown in Table 1.

(Comparative Example 5)
2.5 g of a manganese nitrate aqueous solution in which the concentration of the manganese nitrate aqueous solution was adjusted so that the supported amount of manganese after firing was 5.0% by mass with respect to the total amount of the alumina support and the manganese was added to the alumina. A comparative catalyst was obtained in the same manner as in Comparative Example 4 except that the whole amount of manganese charged was supported. In addition, the manganese carrying amount of the obtained comparative catalyst was 5.0% by mass with respect to the total amount of the alumina carrier and manganese. About the obtained comparative catalyst, the average crystallite size (average primary particle size) of the alumina support was measured in the same manner as in Example 1. Further, the VOC decomposition and removal rate was determined in the same manner as in Example 1 except that this comparative catalyst was used. The obtained results are shown in Table 1.

(Comparative Example 6)
The concentration of the manganese nitrate aqueous solution and 2.5 g of the manganese nitrate aqueous solution adjusted so that the supported amount of manganese after firing was 7.5% by mass with respect to the total amount of the alumina support and the manganese was added to the alumina ( A comparative catalyst was obtained in the same manner as in Comparative Example 4 except that the whole amount of manganese charged was supported). In addition, the manganese carrying amount of the obtained comparative catalyst was 7.5% by mass with respect to the total amount of the alumina carrier and manganese. About the obtained comparative catalyst, the average crystallite size (average primary particle size) of the alumina support was measured in the same manner as in Example 1. Further, the VOC decomposition and removal rate was determined in the same manner as in Example 1 except that this comparative catalyst was used. The obtained results are shown in Table 1.

(Comparative Example 7)
In 2 g of the alumina carrier obtained in the same manner as in Comparative Example 4, a PtP-salt aqueous solution (Tanaka Kikinzoku Kogyo Kogyo Co., Ltd., 50 g Pt / L) was dissolved in ion-exchanged water, and the amount of platinum (Pt) supported after firing was alumina. A mixture was obtained by adding and mixing 2.5 g of a PtP-salt aqueous solution whose concentration was adjusted to 5.0 mass% with respect to the total amount of the carrier and platinum (Pt) (note that the total amount of Pt charged was Supported). Next, this mixture was heated at 110 ° C. for 12 hours and dried, and then calcined at 500 ° C. for 1 hour to obtain a comparative catalyst in which platinum (Pt) was supported on an alumina carrier. In addition, the platinum (Pt) carrying amount of the obtained comparative catalyst was 5.0% by mass with respect to the total amount of the alumina carrier and platinum (Pt). The VOC decomposition removal rate of the obtained comparative catalyst was measured in the same manner as in Example 1. The obtained results are shown in Table 1.

(Comparative Example 8)
The alumina carrier (powder) obtained in the same manner as in Comparative Example 4 was used as a comparative catalyst. The VOC decomposition removal rate of this comparative catalyst was measured in the same manner as in Example 1. The obtained results are shown in Table 1.

<Evaluation results>
In FIG. 1, the graph which shows the toluene removal rate (decomposition removal rate) of the VOC decomposition removal catalyst obtained in Examples 1-3 and the comparison catalyst obtained in Comparative Examples 1-8 is shown. As is clear from the results shown in FIG. 1, it was confirmed that the VOC decomposition / removal catalysts in which manganese of Examples 1 to 3 was supported on an alumina support had sufficient toluene removal performance. On the other hand, in Comparative Examples 1-8, it was confirmed that sufficient toluene removal performance was not obtained as in Examples 1-3.

  FIG. 2 is a graph showing the relationship between the amount of manganese (Mn) supported and the toluene removal rate in the VOC decomposition / removal catalysts obtained in Examples 1 to 3 and the comparative catalysts obtained in Comparative Examples 2 to 3. (0.3% by mass: Comparative Example 2, 1.0% by mass: Example 1, 5.0% by mass: Example 2, 7.5% by mass: Example 3, 10.0% by mass: Comparative Example 3). As apparent from the results shown in FIG. 2, when the amount of manganese supported is in the range of 0.5 to 8.0% by mass with respect to the total amount of the alumina support and manganese, sufficient toluene removal is achieved. It was confirmed to have performance. On the other hand, it was confirmed that even when the alumina carrier carried manganese, when the carrying amount was small (Comparative Example 2), sufficient toluene removal performance could not be obtained. Further, even when the alumina carrier carries manganese, when the carrying amount is large (Comparative Example 3), the toluene decomposition / removal rate decreases, and the VOC decomposition / removal performance is inhibited by a certain amount or more of manganese. It was confirmed.

  FIG. 3 is a graph showing the relationship between the average primary particle size of the alumina carrier and the toluene removal rate in the VOC decomposition removal catalyst obtained in Examples 1 to 3 and the comparison catalyst obtained in Comparative Examples 4 to 6. (8.1 nm: Example 1, 9.0 nm: Example 2, 13.5 nm: Example 3, 15.5 nm: Comparative Example 4, 15.7 nm: Comparative Example 5, 19.3: Comparative Example 6) . As is clear from the results shown in FIG. 3, it was confirmed that when the average primary particle size of the alumina support was in the range of 6 to 15 nm, it had sufficient toluene removal performance. On the other hand, even if the alumina carrier carries manganese, when the manganese is carried by the impregnation method (Comparative Examples 4 to 6), the average primary particle size of the alumina carrier becomes large and sufficient toluene removal performance is obtained. Not confirmed.

  The VOC decomposition / removal rate was determined in the same manner as in Examples 1 to 3 except that the ozone concentration of the mixed gas to be circulated was 0 ppm. As a result, in all cases, the toluene removal rate was less than the lower limit of measurement (less than 2%), and it was confirmed that sufficient toluene decomposition / removal performance was not achieved when ozone was not used in combination in such a VOC decomposition / removal method. It was.

  As described above, according to the present invention, it is possible to provide a VOC decomposition / removal catalyst having excellent VOC decomposition / removal performance, a production method thereof, and a VOC decomposition / removal method using the same.

Claims (6)

  An alumina support having an average primary particle size of 6 to 15 nm, and manganese supported on the alumina support, and the amount of manganese supported is 0.5 to the total amount of the alumina support and manganese. A catalyst for removing VOC decomposition, which is 8.0% by mass.   The average primary particle size of the alumina support is 8 to 13 nm, and the supported amount of manganese is 1.0 to 5.0 mass% with respect to the total amount of the alumina support and manganese. Item 4. The catalyst for removing VOC decomposition according to Item 1. Preparing an alumina sol having an average primary particle size of 5 to 40 nm;
A manganese salt aqueous solution is brought into contact with the alumina sol, and manganese is supported on the alumina sol in such an amount that the supported amount of manganese becomes 0.5 to 8.0% by mass with respect to the total amount of the alumina support and the manganese after firing. Obtaining a gelled product;
The step of obtaining the VOC decomposition removal catalyst according to claim 1 or 2 by calcining the gelled product at a temperature within a range of 300 to 900 ° C;
A method for producing a VOC decomposition removal catalyst comprising:   In the step of obtaining the VOC decomposition removal catalyst, the gelled product obtained by the step of obtaining the gelled product before the calcination is dried at a temperature in the range of 50 to 200 ° C. to remove moisture and obtain a dried product. 4. The method for producing a VOC decomposition / removal catalyst according to claim 3, further comprising a step.   A VOC decomposition / removal method comprising decomposing and removing the VOC by bringing a gas containing VOC into contact with the VOC decomposition / removal catalyst according to claim 1 or 2 in the presence of ozone.   6. The VOC decomposition according to claim 5, wherein a concentration ratio (B / A) of the ozone (B) to a VOC (A) of the gas containing the VOC is 0.1 to 4 (B / A). Removal method.

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