JP5414719B2 - INORGANIC OXIDE FORMED CATALYST FOR DECOMPOSING VOLATILE ORGANIC COMPOUNDS AND METHOD FOR PRODUCING THE SAME - Google Patents

Description

  The present invention relates to an inorganic oxide forming catalyst, a method for producing the same, and decomposition of a volatile organic compound (VOC) using the same.

  Volatile organic compounds (VOCs) cause photochemical smog and airborne particulate matter contamination, causing health problems for residents. Therefore, a catalyst for decomposing VOC into water and carbon dioxide has been attracting attention. Since the combustion temperature of the VOC is lowered and the catalyst body can be used semipermanently, it is considered effective to use a catalyst as one means for processing the VOC. Conventionally, it is known that noble metals such as platinum are used as catalysts for such VOC treatment apparatuses, but these noble metals are expensive and have great restrictions on their use as resources. For this reason, it is important to use an inexpensive material instead of a widely used precious metal such as platinum in order to promote the cost reduction of the apparatus and to spread the apparatus. VOCs that are aliphatic hydrocarbons such as hexane, aromatic hydrocarbons such as benzene and toluene, and polycyclic aromatic hydrocarbons such as naphthalene, especially toluene that is used in a wide range of applications such as organic solvents and paints, For aromatic hydrocarbons such as benzene, development of new catalysts using inexpensive materials is desired. In addition, it is known that the activity of a platinum catalyst decreases in the presence of water vapor, and there is a problem that the original performance cannot be exhibited when used in a practical environment with humidity.

Inexpensive inorganic oxides are expected as catalysts for VOC decomposition that can replace noble metals. As an example, as disclosed in Patent Document 1, it has been reported that cerium oxide (CeO ₂ ) exhibits high activity against the decomposition of toluene.

  However, unlike noble metal catalysts supported on honeycomb-type carriers and the like, inorganic oxide catalysts such as cerium oxide are powders, so when introducing these catalysts into a practical device, pressure loss and the atmosphere Therefore, it is necessary to form a catalyst because it is necessary to prevent the splattering and clogging of the filter.

  In general, the strength of the molded catalyst is good in the tableting molding method, but the production cost is expensive, and further, there is a demerit that the pores are crushed by applying pressure and the surface area effective for catalytic activity is reduced. On the other hand, the extrusion molding method is low in production cost and retains pores and increases in activity, but has low strength as a catalyst and easily causes trouble in practical apparatuses and systems.

JP 2006-015338 A

  From the background as described above, the present invention solves the problems in molding inorganic oxide powders such as cerium oxide, which have been reported as inorganic oxide catalysts for VOC decomposition, and has high activity in decomposing VOCs such as toluene. In addition, the present invention aims to provide a new molded catalyst for VOC decomposition that has a high strength as a molded catalyst and is suitable for use in apparatuses and systems under practical conditions.

  In order to solve the above problems, the present invention uses a volatile organic compound (VOC) decomposition that can be used as a molding binder to maintain a high VOC decomposition performance and a high strength of the molded article after extrusion molding even at a high surface area. A molding catalyst is provided.

That is, the present invention is characterized by the following.
1st: The inorganic oxide shaping | molding catalyst containing an inorganic oxide and the shaping | molding binder which contains at least 1 sort (s) of a clay substance and a metal oxide as a main component.
Second: The inorganic oxide used above is at least one metal selected from cerium, manganese, nickel, selenium, zirconium, yttrium, tantalum, tungsten, bismuth, iron, copper, chromium, titanium, vanadium, zinc, and lanthanum It is an oxide of an element.
Third: The clay material used in the above is at least one selected from kaolin, bentonite white clay, and diatomaceous earth.
Fourth: The metal oxide used in the above is at least one selected from cobalt oxide, copper oxide, chromium oxide, tungsten oxide and zinc oxide.
Fifth: The cobalt oxide used above is tricobalt tetroxide.
Sixth: BET specific surface area of 70 m ² g ⁻¹ or more and strength of 0.1 Nmm ⁻² or more Seventh: The method for producing an inorganic oxide molded catalyst, comprising at least the following steps: A method for producing an inorganic oxide shaped catalyst.

(A) Firing of a mixture of the inorganic oxide raw material or the inorganic oxide raw material and a metal oxide raw material as a molding binder main component,
(B) extrusion molding using a molding binder or molding auxiliary containing a clay substance as a main component,
(C) Firing after molding.
Eighth: A method for producing the inorganic oxide shaped catalyst, comprising at least the following steps.

(A) a step of firing a mixture of the inorganic oxide raw material and the metal oxide raw material as a molding binder main component;
(B) a step of extruding the fired product,
(C) A step of firing after molding.
Ninth: The raw material of the inorganic oxide in step (A) is carbonate.
Tenth: The raw material for the metal oxide in step (A) is carbonate.
Eleventh: The molding aid in step (B) is a cellulosic material.
Twelfth: Firing in step (A) is firing in the range of 300 ° C. to 600 ° C. in air.
13th: Firing in step (C) is firing in the range of 300 ° C to 600 ° C in air.
14th: A method for decomposing a volatile organic compound (VOC), wherein the molding catalyst is brought into thermal contact with a gas phase containing a volatile organic compound (VOC) to oxidatively decompose the volatile organic compound.

  The feature of using metal oxides and clay materials as molding binders for various inorganic oxides keeps the strength strong and maintains high catalytic activity, and is an inexpensive and simple extrusion method, firing at low temperature, etc. Is expected to contribute to lowering the cost of VOC treatment equipment and to improving the environment through the spread of equipment.

The activity of Ce-Co (1: 1) oxide catalyst (solid line) and platinum catalyst (dashed line) for toluene decomposition shows the conversion of toluene and CO ₂ with respect to reaction temperature. The catalytic activity in the presence of 5% water vapor at a reaction temperature of 200 ° C is also shown. The toluene conversion rate of the composite molding catalyst of copper oxide and cobalt oxide with respect to the ratio of copper element is shown. As a comparison, the toluene conversion rate of a molded catalyst using commercially available CeO ₂ is indicated by a dotted line in the figure. It is a figure which shows the surface area of the composite shaping | molding catalyst of the copper oxide and cobalt oxide with respect to the ratio of a copper element, and the intensity | strength of a shaping | molding catalyst. (A) is a photograph showing a cylindrical shaped catalyst, and (b) is a photograph showing a honeycomb shaped catalyst. (A) shows the odor level of the malodorous gas before and after the treatment with the produced honeycomb shaped catalyst, and (b) shows the malodor before and after the treatment with the commercially available honeycomb type platinum catalyst. Indicates the odor level of the gas. (C) has shown the component of malodorous gas. The activity of ethyl acetate decomposition of (a) CuO—Co ₃ O ₄ —CeO ₂ powder and (b) Pt (0.08 wt%) / zeolite catalyst shows the conversion rate of CO ₂ with respect to the reaction temperature. (A) is a diagram showing changes in specific surface area to CuO-Co ₃ O ₄ -CeO ₂ powder and _{(b) CuO-Co 3 O} 4 powder heating time.

  The inorganic oxide forming catalyst of the present invention has a three-dimensional predetermined shape such as a columnar shape or a honeycomb shape, not a non-uniform powder or particle body in its shape.

  The inorganic oxide shaping | molding catalyst of this invention makes it essential that the following components are included in the composition.

  (A) An inorganic oxide, for example, one or more oxides of various metal elements as described above.

  (B) A shaped binder, that is, one or more of a clay material and a metal oxide. Here, preferred examples of the metal oxide include cobalt oxide, copper oxide, chromium oxide, tungsten oxide, and zinc oxide as described above.

  Suitable clay materials include, for example, kaolin, bentonite white clay, and diatomaceous earth.

  The inorganic oxide of component (A) has the activity of decomposing volatile organic compounds (VOC), or expresses this decomposing activity in combination with the molding binder of component (B). The component (B) has an effect of improving the molding strength, but may itself have the above-described decomposing activity, or may exhibit the decomposing activity as a combination as described above. . It can be said that the catalyst of the present invention capable of achieving both the molding strength and the catalytic activity has high technical value.

  The inorganic oxide molding catalyst is in the form of a composite in which the component (A) and the component (B) are in a separable mixed state or in a state where they are difficult to separate. Also good. In addition, a composite in which the oxide of the metal element as the inorganic oxide as the component (A) and the metal oxide contained in the molded binder as the component (B) are integrated in a state in which separation is difficult It may be in the state of the body.

  When the metal oxide of the forming binder is at least one selected from cobalt oxide, copper oxide, chromium oxide, tungsten oxide and zinc oxide, these metal oxides have a good effect of improving the forming strength. Therefore, an inorganic oxide molding catalyst having the desired effect can be obtained even if the molding binder does not contain a clay substance. Of course, the molded binder may contain the above-mentioned metal oxide and clay material, and in this case, the moldability becomes better in the production of the inorganic oxide molded catalyst. Moreover, the strength of the inorganic oxide shaped catalyst finally obtained also becomes better.

  Considering comprehensively the moldability, the strength of the inorganic oxide molding catalyst, the specific surface area, the catalytic activity, and the like, cobalt oxide can be mentioned as a preferable one among the above metal oxides. In particular, when the cobalt oxide is tricobalt tetroxide, it is preferable because the specific surface area can be kept high while maintaining the strength of the resulting inorganic oxide shaped catalyst to some extent, and the catalytic activity can be further improved. .

As a preferred embodiment of the inorganic oxide forming catalyst of the present invention, a combination of the component (A) in which the inorganic oxide is copper oxide and cerium oxide and the component (B) in which the forming binder contains cobalt oxide is used. Can be mentioned. This combination of inorganic oxide forming catalysts (for example, Cu-Co-Ce oxide catalysts such as CuO-Co ₃ O ₄ -CeO ₂ ) has a large specific surface area and is expected to have good catalytic activity and good mechanical strength. It is. In addition, there is an effect that sintering is suppressed. When the firing time of the powder catalyst is increased in the production of the inorganic oxide molded catalyst, the particles usually aggregate and the specific surface area tends to decrease. However, when the component (A) contains cerium oxide, the sintering Rings are suppressed and the degree of reduction in specific surface area over time is reduced. As will be described later, an inorganic oxide forming catalyst (for example, CuO—Co ₃ O ₄ ) in combination of a component (A) in which the inorganic oxide is copper oxide and a component (B) in which the forming binder contains cobalt oxide. From the comparison with Cu-Co oxide catalysts such as Cu-Co-Ce oxide catalyst, the Cu-Co-Ce oxide catalyst has a large specific surface area, and the change in the specific surface area with the firing time of the powder catalyst is small.

For the inorganic oxide shaped catalyst of the present invention, the BET specific surface area is 70 m ² g ⁻¹ or more, the strength is 0.1 Nmm ⁻² or more, and in the composition, the ratio of the copper element in the composite oxide with cobalt is A more preferable example is in the range of 3 to 20 mol% and the ratio of cerium element to 50%. The upper limit value of the BET specific surface area is not particularly limited, but can be, for example, 150 m ² g ⁻¹ . Further, the upper limit value of the strength is not particularly limited, but may be 5 Nmm ^-2 , for example. Here, strength refers to compressive stress.

In the inorganic oxide molding catalyst, when the metal binder is contained in the molding binder as the component (B), in the mixture or composite of the inorganic oxide as the component (A) and the metal oxide of the component (B) The molar ratio of the metal element of the inorganic oxide of the component (A) to the metal element of the metal oxide of the component (B) varies depending on the type of the metal element, but in order to achieve the desired effect, for example, 50 mol% or less It is preferably 3 to 50 mol%, more preferably 3 to 20 mol%. Taking an example of an inorganic oxide forming catalyst containing copper oxide as component (A) and cobalt oxide as component (B), the ratio of copper element in the complex oxide with cobalt is in the range of 3 to 20 mol%. It is exemplified as being more preferable. In the example of the inorganic oxide forming catalyst containing cerium oxide as the component (A) and cobalt oxide as the component (B), the ratio of the cerium element in the composite oxide with cobalt is more preferably about 50 mol%. It is illustrated as a thing.

  In the case where a clay binder is contained in the forming binder as the component (B) in the inorganic oxide forming catalyst, from the viewpoint of securing the amount of catalyst per unit mass of the inorganic oxide forming catalyst and maintaining the forming strength of the forming catalyst. The ratio of the clay substance in the inorganic oxide molding catalyst is 50 wt% or less, preferably 5 to 40 wt%, more preferably 8 to 30 wt%.

  The above inorganic oxide forming catalyst has activity in the decomposition of volatile organic compounds (VOC). VOCs to which the inorganic oxide forming catalyst of the present invention is applied include, for example, aliphatic hydrocarbons such as hexane, aromatic hydrocarbons such as benzene and toluene, polycyclic aromatic hydrocarbons such as naphthalene, methyl isobutyl ketone, Examples include ketones such as methyl ethyl ketone, esters of acetic acid such as ethyl acetate and butyl acetate, aldehydes such as acetaldehyde, and the like.

  And the inorganic oxide shaping | molding catalyst of this invention has the advantage that the fall of activity is suppressed even in presence of water vapor | steam, and it is strong in water vapor | steam poisoning. It also has the advantage of being inexpensive. When the inorganic oxide forming catalyst is a Co—Ce oxide catalyst, it exhibits excellent activity for complete decomposition of toluene, particularly complete decomposition of ethyl acetate, and sintering does not easily occur even if the reaction is performed for a long time. In addition, the activity hardly decreases even in the reaction in the presence of water vapor, for example, in the presence of 5 vol% water vapor. Further, the Co oxide contributes to maintaining the molding strength and is easy to mold.

  The inorganic oxide forming catalyst of the present invention can be produced by mixing and firing an inorganic oxide raw material and a forming binder, for example, a metal oxide raw material, more preferably at least It can be manufactured by a method including the following steps.

(A-1) Firing of a mixture of a raw material of inorganic oxide or a raw material of inorganic oxide and a raw material of metal oxide as a forming binder main component,
(B-1) Extrusion molding using a molding binder or molding aid containing a clay substance as a main component,
(C-1) Firing after molding.

  About the inorganic oxide forming catalyst when the metal oxide contained in the component (B) is at least one selected from cobalt oxide, copper oxide, chromium oxide, tungsten oxide and zinc oxide, at least It can also be produced by a method including the steps of

(A-2) A step of firing a mixture of an inorganic oxide raw material and a metal oxide raw material as a main component of the molding binder (wherein the metal oxide is cobalt oxide, copper oxide, chromium oxide) , At least one selected from tungsten oxide and zinc oxide).
(B-2) a step of extruding the fired product,
(C-2) A step of firing after molding.

  In step (A-1), the inorganic oxide raw material of component (A) is fired, or a mixture of the inorganic oxide raw material of component (A) and the metal oxide raw material of component (B) is fired. Step (A-2) is a step of firing a mixture of the raw material of the component (A) inorganic oxide and the raw material of the component (B) metal oxide. More preferably, in step (A-1) and step (A-2), it is considered that carbonate is used as the raw material for the inorganic oxide and carbonate is used as the raw material for the metal oxide. Preferably, the calcination is performed in a relatively low temperature range of 300 ° C. to 400 ° C. in air, but may be 300 ° C. to 600 ° C. in air. Of course, oxidation baking using an oxygen-containing gas may be used.

  If the calcination temperature exceeds 600 ° C., the particles tend to aggregate and the activity tends to decrease.

  The fired products of step (A-1) and step (A-2) are usually obtained as a powder.

  In the step (B-1), the molding binder is preferably one or more selected from a clay material, and the molding auxiliary is selected from a cellulose material. More preferably, the clay material is kaolin, and the cellulose material is methylcellulose. Other examples include bentonite clay and diatomaceous earth as clay materials, and cellulose acetate and ethyl cellulose as cellulose materials. In the case where a metal oxide raw material is not used as a forming binder in the step (A-1), a forming binder containing a clay substance is used in the step (B-1), and further a forming aid is used as necessary. Can be extruded. In the step (B-2), extrusion molding can be performed using a molding aid as necessary. Such a molding aid is added, for example, in a proportion of 1 to 10 wt%, preferably 3 to 5 wt% in the molded catalyst material.

  In step (B-1) and step (B-2), water can be added to the fired products of step (A-1) and step (A-2) and kneaded, and the kneaded product can be extruded. The amount of water to be added is not particularly limited, and is appropriately set to such an extent that the kneaded product can maintain a predetermined three-dimensional shape even after extrusion molding. For example, water can be added at a ratio of 10 ml to 100 ml with respect to 100 g of the fired product.

  Extrusion molding can be performed using a known extruder such as a single-screw or twin-screw extruder. For example, the shaping | molding catalyst material mixed with the single screw extruder can be supplied, and it can shape | mold into a predetermined shape through a die | dye (metal mold | die). Depending on the type of the extruder such as a twin-screw extruder, the supplied formed catalyst material can be continuously extruded after being mixed in the apparatus.

  Extrusion molding conditions are appropriately set according to the type of extruder, screw shape, die structure and the like. When water is contained in the molding catalyst material supplied to a molding tool such as an extruder, for example, cold water at a temperature of 5 ° C to 10 ° C is flowed around the molding tool in order to suppress moisture evaporation of the molding catalyst material. Consider keeping the temperature of the instrument low. In extrusion molding, vacuum deaeration may or may not be performed. When vacuum deaeration is not performed, a porous shaped body can be obtained, and an improvement in activity can be expected.

  The firing in the step (C-1) and the step (C-2) can be performed by oxidation firing using an oxygen-containing gas, as described above, but in a relatively low temperature range of 300 ° C. to 400 ° C. in air. However, it may be set to 300 ° C. to 600 ° C. in air.

  The firing here is usually preferably performed after drying (air drying). If the firing temperature exceeds 600 ° C., the particles tend to aggregate and the activity tends to decrease, and if it is less than 300 ° C., there is a problem that the molding aid cannot be completely combusted.

  For VOC decomposition using the catalyst of the present invention, the following are considered as operating conditions.

Space velocity (SV) 5000-35000h ^-1
Heating temperature 100 ~ 300 ℃
VOC concentration in treated air 1000ppm or less
Depending on the type of VOC, the VOC concentration in the air to be treated can be reduced to 1500 ppm or less.

  Then, an Example is shown below and it demonstrates in detail. Of course, the present invention is not limited to the following examples.

This is an example of a shaped catalyst in which the inorganic oxide is cerium oxide (CeO ₂ ) and the metal oxide of the shaped binder is cobalt oxide (Co ₃ O ₄ ).
<1-1> Catalyst synthesis
2CoCO ₃ 3Co (OH) ₂ 4H ₂ O, which is a carbonate of Co and Ce, was mixed with Ce ₂ (CO ₃ ) ₃ 8H ₂ O powder (commercially available) and calcined at 300 ° C. for 5 hours in air.
<1-2> Evaluation of activity of molded catalyst 1 g of a molded catalyst prepared by an extrusion molding method using a molded catalyst material containing a synthesized catalyst was packed in a Pyrex (registered trademark) glass reaction vessel. The reaction tube was heated with a heater installed around the reaction tube. A mixture of He, N ₂ , and O ₂ prepared so that VOC (toluene) is 210 ppm and oxygen concentration is 13% flows through the reaction tube at a rate of 304 ml per minute, and the gas components after passing through the reaction tube are gas chromatographs. And the conversion of toluene and CO ₂ was determined. The space velocity (SV) was set to 16600 h- ¹ .
<1-3> Results The results are summarized in FIG. FIG. 1 shows the activity of Ce-Co (1: 1 (molar ratio)) oxide catalyst and platinum catalyst for toluene decomposition as a conversion ratio of toluene and CO ₂ with respect to reaction temperature. Toluene reacts with oxygen, passes through various carbon compounds, and finally becomes CO ₂ and water. The developed Ce-Co oxide catalyst was able to achieve complete decomposition at a lower temperature than the platinum catalyst. Furthermore, the first stage in which toluene was decomposed was achieved at a low temperature of 50 ° C. to 160 ° C., greatly exceeding the platinum catalyst. Further, the catalytic activity in the presence of 5% water vapor at a reaction temperature of 200 ° C. is also shown in FIG. The activity of the Ce-Co (1: 1 (molar ratio)) oxide catalyst was hardly decreased compared to the platinum catalyst whose activity decreased to less than half.

This is an example of a shaped catalyst in which the inorganic oxide is copper oxide (CuO) and the metal oxide of the shaped binder is cobalt oxide (Co ₃ O ₄ ).
<2-1> Synthesis of catalyst
2CoCO ₃ 3Co (OH) ₂ 4H ₂ O, which is a carbonate of Co and Cu, and CuCO ₃ Cu (OH) ₂ powder (commercially available) were mixed and calcined in air at 300 ° C. for 5 hours.
<2-2> Molding of catalyst To the resulting molded catalyst material, 10 wt% binder (clay material) and 3 wt% methylcellulose 4000 were added and mixed, and then an appropriate amount of water was added and kneaded well. . Then, after extruding with an extruder and drying, it was fired in air at 300 ° C. for 5 hours.
<2-3> Activity Evaluation of Molded Catalyst 7 cm ³ of the produced molded catalyst (cylindrical shape having a diameter of about 1 mm and a length of about 5 mm) was packed in a Pyrex (registered trademark) glass reaction vessel. The reaction tube was heated with a heater installed around the reaction tube. Temperature measurement was performed at two locations inside and outside the reaction tube, and the average temperature was set to 220 ° C. About 6 L / min of dry air containing 100 ppm of VOC (toluene) was flowed into the reaction tube, and the components of the gas after passing through the reaction tube were analyzed using a micro GC to determine the conversion rate of toluene. The space velocity (SV) was set to 133000h- ^1, and it was set considerably higher than 30000h- ^1, which is the SV of a general apparatus for the purpose of verifying the strength and pressure loss of the molded body.
<2-4> Results FIG. 2 shows the conversion ratio of toluene with respect to the ratio of the molar amount of Cu element to Co in the Cu—Co oxide. The activity was the best when about 10 mol% of Cu was combined with Co.

  The strength and BET surface area of the molded catalyst prepared in Example 2 were examined. The strength was determined as compressive stress. As shown in FIG. 3, the surface area increased in the region where the ratio of Cu element to Co element in the Cu—Co oxide was approximately 3-20 mol%. The strength decreased as the proportion of Cu element increased.

Moreover, when the strength (compressive stress) of commercially available activated carbon and the strength (compressive stress) of a molded catalyst using commercially available CeO ₂ (kaolin 10 wt%) were examined, the strength of commercially available activated carbon was 6.7 N / mm ² . The strength of the shaped catalyst using commercial CeO ₂ (kaolin 10 wt%) was about 0.2 N / mm ² .

From these results, it can be seen that by using Co ₃ O ₄ , the strength can be maintained to some extent and the surface area can be kept high.

An example of a molding catalyst in which the inorganic oxide is copper oxide (CuO) and cerium oxide (CeO ₂ ), the metal oxide of the molding binder is cobalt oxide (Co ₃ O ₄ ), and the clay material is kaolin. is there.
<4-1> Manufacture of molded catalyst
CuCO ₃ Cu (OH) ₂ , Ce ₂ (CO ₃ ) ₃ 8H ₂ O, 2CoCO ₃ 3Co (OH) ₂ 4H ₂ O powders, which are carbonates of Cu, Ce and Co, are mixed in air at 300 ° C. Calcination was performed for 5 hours to prepare CuO—Co ₃ O ₄ —CeO ₂ (Cu: Co: Ce = 10: 45: 45 mol%) powder. A suitable amount of water and kaolin powder (10 wt%), which is a clay material, are mixed and kneaded, and the kneaded product is extruded into a cylindrical shape, dried, and fired at 550 ° C. in the air as shown in FIG. A cylindrical shaped catalyst (CuO—Co ₃ O ₄ —CeO ₂ (Cu: Co: Ce = 10: 45: 45 mol%)) shown in a) was produced.

In addition, the kneaded product is extruded and formed into a honeycomb shape by the same method, then dried and fired at 550 ° C. in air, thereby forming a honeycomb-shaped forming catalyst (CuO—Co ₃ O ₄ ) shown in FIG. -CeO ₂ (Cu: Co: Ce = 10: 45: 45 mol%)) was also produced.

When the BET specific surface area of each formed catalyst was examined, it was about 100 m ² g ⁻¹ , and it was confirmed that the high surface area was maintained. Although the strength was inferior to that of the ceramic carrier, it was at a practically usable level.
<4-2> Catalyst activity evaluation 1
The malodor treatment performance was evaluated using the formed honeycomb shaped catalyst. The details of the malodorous gas that is the gas to be treated are as follows.

  The painted product actually painted with 1/100 scale of the actual machine was dried to generate almost the same malodorous gas as the paint shop site. Ingredients such as formaldehyde that are of concern for carcinogenicity are generated during the drying process, and these ingredients combine to form a malodor (burnt odor).

  The experimental conditions are as follows.

SV (space velocity): 16600h ^-1
LV (Line speed): 0.33m / s
Gas flow rate: Dry air 50L / min
Molded catalyst amount: 188ml
Reaction inlet temperature: 287 ° C
The odor level of the gas before passing the malodorous gas through the molded catalyst (before treatment) and the odor level of the gas after passing the malodorous gas through the molded catalyst (after treatment) were measured using a semiconductor-type VOC odor meter. . The result is shown in FIG. FIG. 5 (b) also shows the result of evaluating a commercially available honeycomb type platinum catalyst (0.3 wt% Pt / Al ₂ O ₃ supported ceramic honeycomb catalyst) under the same conditions instead of the produced honeycomb shaped catalyst. Moreover, the component of the malodorous gas which is to-be-processed gas is shown in FIG.5 (c).

  As shown in FIGS. 5 (a) and 5 (b), the value of the odor level was high before the treatment and a fairly strong burning odor was confirmed, but the value of the odor level was low and almost odorless after the treatment. . The threshold for feeling odor varies depending on the type of gas, but in this case, the odor level was roughly between 20-30 and was almost odorless.

From these results, it was confirmed that the produced honeycomb shaped catalyst had the same malodor treatment performance as that of a commercially available honeycomb type platinum catalyst.
<4-3> Catalyst activity evaluation 2
The activity against ethyl acetate (concentration 1200 ppm) was evaluated using 1 g of CuO—Co ₃ O ₄ —CeO ₂ (Cu: Co: Ce = 10: 45: 45 mol%) powder. The activity evaluation method and operating conditions are the same as in Example 1. The activity of the Pt (0.08 wt%) / zeolite catalyst used in Example 1 as a control experiment for ethyl acetate decomposition was also evaluated. Commercially available platinum catalyst is usually 0.3 wt% on alumina, and 4 g of Pt (0.08 wt%) / zeolite catalyst was used to match it.

The results are shown in FIG. FIG. 6 shows the activity of CuO—Co ₃ O ₄ —CeO ₂ powder and Pt (0.08 wt%) / zeolite catalyst for ethyl acetate decomposition as a conversion ratio of CO ₂ to reaction temperature. In the figure, (a) is the result of CuO—Co ₃ O ₄ —CeO ₂ powder, and (b) is the result of Pt (0.08 wt%) / zeolite catalyst. Ethyl acetate reacts with oxygen, passes through various carbon compounds on the way, and finally becomes CO ₂ and water. It was confirmed that CuO-Co ₃ O ₄ -CeO ₂ powder could achieve complete decomposition at lower temperature than Pt (0.08wt%) / zeolite catalyst. From this, it is expected that the formed catalyst prepared using CuO—Co ₃ O ₄ —CeO ₂ powder can be completely decomposed at a lower temperature than the Pt (0.08 wt%) / zeolite catalyst.

  Various powder catalysts and clay substances were mixed with appropriate amounts of water, kneaded well, extruded, dried, and calcined at 300 ° C. for 5 hours to produce a molded catalyst. As the clay material, kaolin powder was used at the ratio shown in Table 1. The BET specific surface areas of various powder catalysts and their shaped catalysts were investigated. The results are shown in Table 1.

In Table 1, “cerium oxide (commercially available)” indicates that the powder catalyst is commercially available cerium oxide, and “cerium oxide (synthesized)” represents commercially available Ce ₂ (CO ₃ ) ₃ 8H ₂ O powder. It shows that it is cerium oxide produced by firing for 5 hours at 300 ° C. in air. In Table 1, “Co—Ce oxide” is the catalyst prepared in <1-1> of Example 1, and “Co—Cu oxide” is prepared in <2-1> of Example 2. Catalyst.

  Further, when the strength of the molded catalyst was examined, the compression stress of the Co—Cu oxide was the best and the molded state was the best.

When the catalytic activity of the molded catalyst using cerium oxide (commercially available) was evaluated by the method <2-3> in Example 2, the toluene conversion was 7%. When the catalytic activity was similarly evaluated for a molded catalyst (binder amount (kaolin) 50 wt%) using cerium oxide (synthesis), the toluene conversion was 10%.
<Reference Example 1>
Various metal oxide powders and clay materials were mixed with appropriate amounts of water, kneaded well, extruded, dried, fired at 300 ° C. for 5 hours, and the molding strength was examined. Kaolin powder was used as the clay material, and its weight was 10 wt% of the weight of the metal oxide. The results are shown in Table 2 .

  Good shapes were indicated by “◎”, the experimental level was indicated by “◯”, and those that were broken were indicated by “×”.

Table 2 also shows a molding catalyst of CuO—Co ₃ O ₄ (Cu: Co = 10: 90 mol%) prepared in Example 2, and CuO—Co ₃ O ₄ —CeO ₂ (Cu : Co: Ce = 10: 45: 45 mol%) The molding strength results of the respective shaped catalysts are also shown.

From the results shown in Table 2, the Co ₃ O ₄ molded product showed high mechanical strength in the same manner as the molded catalyst of CuO—Co ₃ O ₄ (Cu: Co = 10: 90 mol%). As reported by the inventor in the Tokyo Metropolitan Industrial Technology Research Center Research Report, No. 5, 2010, pages 48-51, Co ₃ O ₄ exhibits high activity for complete decomposition of VOCs. Therefore, Co ₃ O ₄ is a substance that has high catalytic activity for VOC decomposition and can maintain the molding strength, and can be effectively used as a molding binder. CuO, Cr ₂ O ₃ , WO ₃ and ZnO molded products also showed relatively high mechanical strength. For this reason, CuO, Cr ₂ O ₃ , WO ₃ , and ZnO are substances that can maintain the molding strength relatively, and can be used as a molding binder.
<Reference example 2>
Each of the CuO—Co ₃ O ₄ powder produced in <2-1> of Example 2 and the CuO—Co ₃ O ₄ —CeO ₂ powder produced in Example 4 were continuously subjected to 300 ° C. conditions in air. The BET specific surface area was examined by heating for a long time. FIG. 7 shows the measurement results of the specific surface area of the powder catalyst with respect to the heating time. (A) is CuO—Co ₃ O ₄ —CeO ₂ powder, and (b) is CuO—Co ₃ O ₄ powder. Although the specific surface area of the CuO—Co ₃ O ₄ powder of (b) rapidly decreased with time, sintering was suppressed in the CuO—Co ₃ O ₄ —CeO ₂ powder of (a). It can be seen that CeO ₂ is effective in suppressing sintering.

Claims (13)

  An inorganic oxide molding catalyst for decomposing volatile organic compounds, comprising an inorganic oxide and a molding binder containing a clay substance and a metal oxide as main components, wherein the inorganic oxide is an oxide of cerium, or It is an oxide of cerium and copper, and the metal oxide is at least one metal oxide selected from cobalt oxide, copper oxide, chromium oxide, tungsten oxide and zinc oxide. An inorganic oxide molding catalyst for decomposing volatile organic compounds.   The inorganic oxide forming catalyst for volatile organic compound decomposition according to claim 1, wherein the clay material is at least one clay material selected from kaolin, bentonite clay and diatomaceous earth.   The inorganic oxide forming catalyst for volatile organic compound decomposition according to claim 1 or 2, wherein the cobalt oxide is tricobalt tetroxide. The inorganic oxide forming catalyst for volatile organic compound decomposition according to any one of claims 1 to 3, wherein the BET specific surface area is 70 m ² g ^-1 or more and the strength is 0.1 Nmm ^-2 or more.   The molar ratio of the metal element of the inorganic oxide to the metal element of the metal oxide in the mixture or composite of the metal oxide and the inorganic oxide is 3 to 50 mol%. The inorganic oxide shaping | molding catalyst for volatile organic compound decomposition | disassembly as described in any one of 1-4.   6. The volatile organic compound decomposing method according to claim 1, wherein a ratio of the clay substance in the inorganic oxide forming catalyst for decomposing the volatile organic compound is 5 to 40 wt%. Inorganic oxide forming catalyst. A method for producing an inorganic oxide-forming catalyst for decomposing volatile organic compounds according to any one of claims 1 to 6, comprising at least the following steps: A method for producing a catalyst.
(A) a step of firing a mixture of the inorganic oxide raw material and the metal oxide raw material;
(B) a step of extrusion molding using the clay material;
(C) The process of baking after shaping | molding.   The production method according to claim 7, wherein the raw material of the inorganic oxide in the step (A) is a carbonate.   The production method according to claim 7, wherein the raw material of the metal oxide in the step (A) is a carbonate.   The process according to claim 7, wherein a cellulose substance is further used together with the clay substance in the step (B).   The method according to any one of claims 7 to 10, wherein the firing in the step (A) is firing in the range of 300 ° C to 600 ° C in the air.   The method according to any one of claims 7 to 11, wherein the firing in the step (C) is firing in the range of 300 ° C to 600 ° C in air.   A method for decomposing a volatile organic compound, wherein the catalyst according to any one of claims 1 to 6 is brought into thermal contact with a gas phase containing a volatile organic compound to oxidatively decompose the volatile organic compound.