JP2005305245A - Method for treating smelly exhaust gas and apparatus for deodorizing exhaust gas - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for treating smelly exhaust gas, by which volatile organic compounds in low-temperature exhaust gas of ≤300°C, particularly ethyl acetate, 2-butanone and 2-propanol contained in the exhaust gas from a printing factory in large quantities, can be removed by using an inexpensive catalyst at a low running cost. <P>SOLUTION: The smelly exhaust gas is treated at 180-300°C by using the molded catalyst obtained by depositing an oxide (component A) of at least one element selected from the group consisting of Cr, Fe, V, W, Mn, Mo and Ce and Pt and/or Pd (component B) on a titanium oxide carrier. It is preferable that component A is V<SB>2</SB>O<SB>5</SB>, component B is Pd, the amount of V<SB>2</SB>O<SB>5</SB>to be deposited is 0.1-20 wt.% of the total amount of the titanium oxide carrier and component A, the amount of Pd to be deposited is 0.001-20 wt.% of the total amount of all the catalyst components and an oxide of Ni and/or Co (component C) are furthermore deposited on the titanium oxide carrier by 0.01-10 wt.% of the total amount of all the catalyst components. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for treating odorous exhaust gas and an exhaust gas deodorization apparatus.

  Volatile organic compounds contain such volatile organic compounds because they cause deterioration of living environment due to their own carcinogenicity, toxicity, odor, etc., or generation of photochemical oxidants. Various types of removal methods for removing these volatile organic compounds are employed for the exhaust gas. In particular, the catalytic oxidative decomposition method using a catalyst eliminates the generation of thermal NOx because harmful volatile organic compounds are oxidatively decomposed at a relatively low temperature and converted into harmless carbon dioxide gas to make them harmless and non-brominated. Since the device can be made compact, it is widely adopted.

JP-A-8-332384 “Chemical Engineering” (May 1975, pages 35-41)

  Conventionally, as a catalytic oxidative decomposition catalyst for volatile organic compounds, a catalyst in which a noble metal such as platinum is supported as an active component on a support such as alumina has been used. However, such an active ingredient is expensive and is used at a reaction temperature of about 300 ° C. Therefore, when the exhaust gas temperature is lower than 300 ° C., it is necessary to raise the temperature of the exhaust gas and / or the catalyst.

  However, as described above, a method having a high fixed cost and a high running cost is a heavy burden in terms of cost, particularly in exhaust gas treatment from a small apparatus. For this reason, it is not always easy to introduce a volatile organic compound removing facility for a small odorous exhaust gas generating small facility such as in a printing factory or painting factory.

  The present invention has been made in view of the above circumstances, and the object thereof is to use an inexpensive catalyst and to be contained in a large amount in a volatile organic compound in a low-temperature exhaust gas at 300 ° C. or lower, particularly in an exhaust gas from a printing factory. It is an object of the present invention to provide a method and apparatus capable of removing ethyl acetate, 2-butanone and 2-propanol at a low running cost.

  As a result of various studies to solve the above problems, the present inventors have obtained the following knowledge. That is, a catalyst mainly composed of oxides of vanadium and titanium shows a high decomposition rate with respect to ethyl acetate, 2-butanone and 2propanol even at 250 ° C. or lower, but at the same time generates a large amount of carbon monoxide (CO). To do. However, if Pt and / or Pd is supported on such a catalyst, the production of CO is suppressed while maintaining the above high decomposition performance. Further, even if a part of expensive Pt and / or Pd is replaced with Ni and / or Co, the same or higher CO production suppressing effect is exhibited.

  The present invention has been completed based on the above findings, and the first gist thereof is that the titanium oxide support is at least one selected from the group consisting of Cr, Fe, V, W, Mn, Mo, and Ce. Odorous exhaust gas is treated at a temperature of 180 to 300 ° C. using a molded catalyst comprising an oxide of the element (component A) and Pt and / or Pd (component B). It exists in the processing method of odor exhaust gas.

  And the second gist of the present invention is a reactor provided between the odorous exhaust gas generation facility and the exhaust gas blower or at the rear stage of the exhaust gas blower for the odorous exhaust gas generation facility and filled with a catalyst, An exhaust gas deodorization apparatus including temperature detection means for detecting the temperature of the catalyst and temperature adjustment means for maintaining the temperature of the catalyst at 180 ° C. to 300 ° C. based on the temperature detected by the temperature detection means. As the above catalyst, a titanium oxide support, an oxide (component A) of at least one element selected from the group consisting of Cr, Fe, V, W, Mn, Mo, Ce and Pt and / or Pd The present invention resides in an exhaust gas deodorizing apparatus characterized in that it uses a molded catalyst carrying (Component B).

  According to the present invention, volatile organic compounds such as 2-propanol, 2-butanone, and ethyl acetate can be decomposed and removed while suppressing the production of CO even at a low temperature of 300 ° C. or lower.

  First, a method for treating odorous exhaust gas according to the present invention will be described. In the present invention, a catalyst in which a predetermined active component is supported on a titanium oxide carrier is used as an oxidative decomposition catalyst for volatile organic compounds.

The titanium oxide carrier may contain an oxide of W or Si. Specific examples of such a titanium oxide support include TiO ₂ , TiO ₂ —WO ₃ , TiO ₂ —SiO ₂ , TiO ₂ —SiO ₂ —WO _{3 and the} like. In particular, since W is expensive, it is economically preferable to make it 20% by weight or less based on titanium oxide.

  The titanium oxide carrier includes an oxide (component A) of at least one element selected from the group consisting of Cr, Fe, V, W, Mn, Mo, and Ce and Pt and / or Pd (component B). Is supported. The component A is preferably an oxide of vanadium, and the component B is preferably Pd. Further, the titanium oxide carrier can further carry an oxide of Ni and / or Co (component C).

  The amount of component A supported is usually 0.1 to 20% by weight, preferably 0.1 to 10% by weight, based on the total amount of the titanium oxide support and component A. When the amount of the component A supported is too small, the decomposition performance of the volatile organic compound is deteriorated, and when too large, the cost is disadvantageous. The amount of component B supported is usually 0.001 to 20% by weight, preferably 0.001 to 5% by weight, based on the total amount of all catalyst components. When the loading amount of component B is too small, the effect of suppressing CO production is reduced, and when too much, the cost is disadvantageous. The amount of component C supported is usually 0.01 to 10% by weight based on the total amount of all catalyst components. That is, if a necessary amount of component B is present, a part of it can be replaced with component C within the above range. For example, the CO suppression effect of the catalyst (I) of Pd: 0.1% by weight and the catalyst (II) of Pd: 0.02% by weight + Ni: 0.1% by weight (or Co: 0.1% by weight) is approximately It is equivalent. In addition, when the loading amount of component C is less than the above range, the effect due to the addition cannot be sufficiently obtained. On the other hand, when it exceeds the above range, an effect commensurate with the increase in the addition amount cannot be obtained, which is not efficient.

The raw material of the vanadium oxide is not particularly limited, but vanadium pentoxide or ammonium metavanadate (NH ₄ VO ₃ ) is preferable. These raw materials are usually used after being dissolved in an oxalic acid aqueous solution or a monomethanolamine aqueous solution. The raw materials for each oxide such as Pt, Pd, Ni, and Co are not particularly limited. From the viewpoint of impregnation operation on the support and coating operation on the geometric surface of the support, for example, a raw material that dissolves in water, for example, Nitrate and chloride are preferred. For example, in the case of Pd, an aqueous solution in which palladium nitrate is dissolved in a 10% nitric acid aqueous solution is suitable.

  The method for producing the molding catalyst is not particularly limited, and for example, a method of extrusion molding after kneading the carrier component and the active ingredient raw material together with the molding aid can be adopted, but impregnation from the viewpoint of increasing the utilization rate of the active ingredient The method is preferred.

The impregnation method may be a method of impregnating the titanium oxide carrier with all active ingredients, but particularly when the component A is vanadium, the carrier and the vanadium raw material liquid are well mixed and molded, and then fired. A method of firing after impregnating the raw material aqueous solution of the active ingredient component B or component C into the molded body is preferable. In this case, if the immersion time is too short, a predetermined amount of impregnation cannot be achieved, and if it is too long, the vanadium oxide as an active ingredient is eluted, and thus it is usually 10 to 60 minutes, preferably 15 to 40 minutes. In the shaped catalyst obtained by such a method, a support layer of V ₂ O ₅ is formed on the surface of the titanium oxide support, and component B and component C (Pt, Pd, Ni, Co) are formed on the support layer of V ₂ O _5. Has a supported structure. In the above impregnation method, it is preferable to prepare a calibration curve of the raw material liquid concentration and the impregnation amount in advance and determine the raw material liquid concentration so that it becomes a predetermined amount. A similar method can be adopted when using a mixed solution of two or more active ingredients. The shape and size of the catalyst are appropriately selected depending on the amount of processing gas, the shape and size of the reactor, and the like. Examples of the shape of the catalyst include a honeycomb shape, a columnar shape, a spherical shape, and a plate shape. The following method is mentioned as an example of said impregnation method.

(1) Dissolve ammonium metavanadate in an aqueous solution of about 10% by weight monoethanolamine.
(2) A titanium sulfate solution is dissolved by heating to obtain a metatitanic acid slurry.
(3) After adjusting the pH by adding 15 wt% ammonia water to the metatitanic acid slurry, reflux treatment is performed for 1 hour or more.
(4) Ammonium paratungstate is added, and the reflux treatment is further performed for 1 hour or more.
(5) The obtained slurry is filtered, and the obtained cake is dried at a temperature of 50 to 150 ° C. for 3 to 50 hours, then baked at a temperature of 400 to 650 ° C., and pulverized after cooling.
(6) The obtained powdery WO ₃ —TiO ₂ binary composite oxide support and the aqueous solution prepared in the above (1) are kneaded with a kneader.
(7) (i) A kneaded product further kneaded with a molding aid is extruded, dried at a temperature of 50 to 150 ° C. for 3 to 50 hours, and then in an air stream of SV100 to 2000 Hr ⁻¹ , 400 to 650. Firing at a temperature of ° C., or (ii) drying the kneaded material at a temperature of 50 to 150 ° C. for 3 to 50 hours, firing at a temperature of 400 to 650 ° C., and then molding by adding a molding aid.
(8) The molded product is immersed in an aqueous palladium nitrate solution adjusted to a predetermined concentration at room temperature for 20 minutes.
(9) Excess liquid is removed by air blow, dried at a temperature of 50 to 150 ° C. for 3 to 50 hours, and then fired at a temperature of 400 to 650 ° C. in an air stream of SV100 to 2000 Hr ⁻¹ .

  In the present invention, as another method for producing a molded catalyst, a method of impregnating / supporting a carrier component and an active component on a substrate can be employed.

  Specifically, the carrier component prepared in the above (2) to (5) is coated on a base material having a desired shape such as a columnar shape, a spherical shape, a honeycomb shape, or a plate shape, and prepared in the above (1). The active ingredient is impregnated using an aqueous solution, dried at 50 to 150 ° C. for 3 to 50 hours, and then fired at a temperature of 400 to 650 ° C.

Further, the molded product is immersed in an aqueous palladium nitrate solution having a predetermined concentration at room temperature for 20 minutes and dried at a temperature of 50 to 150 ° C. for 3 to 50 hours, and then in an air stream of SV100 to 2000 Hr ⁻¹ , 400 to 650. Bake at a temperature of ° C.

In the case of the catalyst formed on the base material, SiO ₂ or Al ₂ O ₃ is used alone or in combination with TiO ₂ as the base material. The amount of the carrier component is usually 70 to 99.9% by weight based on the total amount of the carrier component and the active component. The total amount of the carrier component and the active component is usually 5 to 70% by weight, preferably 10 to 50% by weight, based on the total amount of the base material, the carrier component and the active component.

  When all of the added raw materials are active components as in the kneading / forming method, the catalyst composition can be estimated from the amount added, assuming that the raw material components such as the respective metal salts have changed to the corresponding metal oxides. I can do it. The impregnated component can be measured by a plasma emission analysis method (ICP-AES analysis method) after the catalyst is treated with sulfuric acid and then melted with ammonium sulfate.

  The carrier used in the present invention has a pore having a larger diameter than the pores formed by the primary particles according to a known method (specifically, the peak apex in the range of 0.05 to 1.0 μm). Pore distribution). Examples of the pore forming agent used for this purpose include crystalline cellulose, polyethylene glycol, polyvinyl alcohol, polyethylene oxide, and phenol resin that are generally used. In general, several types of pore forming agents are used, but the amount used varies depending on molding conditions and substances used. By providing such a pore distribution, the catalyst performance can be maintained even when the pores with small pore diameters formed by primary particles due to thermal degradation or coking due to carbon precipitation are greatly reduced and the specific surface area is lowered.

  The method for treating odorous exhaust gas according to the present invention is characterized in that the odorous exhaust gas is treated at a temperature of 180 to 300 ° C. using the above-mentioned specific catalyst. The odorous exhaust gas is typically exhaust gas containing a volatile organic compound such as ethyl acetate, 2-butanone, 2-propanol, and specific examples thereof include exhaust gas from a resin processing factory and a printing factory. . And if necessary, a high boiling point solvent removal step may be provided in advance.

The treatment temperature of the odorous exhaust gas (contact temperature with the catalyst) is preferably 180 to 200 ° C. When the contact temperature is less than 180 ° C., dew condensation causing trouble in operation is caused, and oxidative decomposition of the volatile organic compound becomes insufficient. When the contact temperature exceeds 250 ° C., the energy for heating becomes great, which is disadvantageous in terms of running cost. The pressure of the catalyst layer is usually −0.05 to 0.9 MPa, preferably −0.01 to 0.5 MPa as a gauge pressure. Also, the space velocity (SV) is usually 100～20000Hr ^-1, preferably 1000~5000Hr ^-1.

  Next, the exhaust gas deodorizing apparatus according to the present invention will be described. 1 (a) and 1 (b) are conceptual explanatory views of an example of an exhaust gas deodorizing apparatus according to the present invention. The exhaust gas deodorization apparatus according to the present invention is provided between the odorous exhaust gas generation facility (1) and the exhaust gas blower (21) or after the exhaust gas blower (22) for the odorous exhaust gas generation facility, and is filled with a catalyst therein. And a temperature detecting means (4) for detecting the temperature of the catalyst, and for maintaining the temperature of the catalyst at 180 to 300 ° C. based on the temperature detected by the temperature detecting means. An exhaust gas deodorization apparatus including a temperature control means (5), wherein the catalyst is at least one selected from the group consisting of Cr, Fe, V, W, Mn, Mo, and Ce as a catalyst. It is characterized by using a formed catalyst comprising an elemental oxide (component A) and Pt and / or Pd (component B). Such an exhaust gas deodorizer is operated in accordance with the above-described method for treating odorous exhaust gas.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited by a following example, unless the summary is exceeded. The catalysts (A) to (D) used in the examples were prepared as follows.

(1) Preparation of catalyst A:
A raw material liquid (1) was prepared by dissolving 347 g of ammonium metavanadate and 943 g of ammonium paratungstate in 6000 g of a 10 wt% monoethanolamine aqueous solution heated to 80 ° C. Further, 5 g of palladium nitrate aqueous solution (manufactured by Engelhard Japan Ltd .: Pd concentration 30 wt% solution) was dissolved in 2995 g of pure water to prepare a raw material liquid (2). 7830 g of TiO ₂ powder (“MC-90” manufactured by Ishihara Sangyo), 1000 g of molding aid (active clay), 500 g of polyethylene oxide, 200 g of crystalline cellulose (Asahi Kasei Co., Ltd. “Avicel TG-101”) in a double-arm kneader After mixing for 2 hours, the raw material liquid (1) was added to the double-arm kneader and kneaded for 3 hours. The obtained kneaded product was molded into a 3 mm diameter cylindrical shape from an extruder. The obtained molded product was dried at a temperature of 130 ° C. for 24 hours, and then calcined for 3 hours under conditions of SV100Hr ⁻¹ and a temperature of 450 ° C. under air flow. After immersing 500 g of the baked product in the raw material liquid (2) for 20 minutes, the excess liquid was removed by air blow, and then dried again at a temperature of 130 ° C. for 24 hours, and then SV100Hr ⁻¹ , temperature 450 under air circulation. The catalyst (A) shown in Table 1 was obtained by calcination for 3 hours under the condition of ° C.

(2) Preparation of catalyst B:
Catalysts shown in Table 1 were prepared in the same manner as in the preparation of Catalyst A, except that 2 g of palladium nitrate aqueous solution and 14.8 g of nickel nitrate hexahydrate were dissolved in 2983 g of pure water to prepare raw material liquid (2). B was prepared.

(3) Preparation of catalyst C:
Catalysts shown in Table 1 were prepared in the same manner as in the preparation of Catalyst A except that 2 g of palladium nitrate aqueous solution and 14.8 g of cobalt nitrate hexahydrate were dissolved in 2983 g of pure water to prepare raw material liquid (2). C was prepared.

(4) Preparation of catalyst D:
A catalyst D shown in Table 1 was prepared in the same manner as in the preparation of the catalyst A, except that the immersion, drying and firing in the raw material liquid (2) were not performed.

<Volatile organic compound decomposition performance evaluation method>
A columnar catalyst having a diameter of 3 mm and a length of 5 mm to 15 mm manufactured for evaluation is set in the center of a reaction tube made of quartz glass (inner diameter: 30 mm, length: 600 mm). The inner diameter is 40 mm, the outer diameter is 200 mm, and the length is 450 mm. Set in a tubular heating furnace.

Gas composition is O ₂ : 10%, H ₂ O: 10%, gas to be decomposed (any one of ethyl acetate, 2-butanone and 2-propanol): 1000 ppm, N ₂ : 60 L of a mixed gas of balance amount / Hr (NTP) at a flow rate of 120 ° C., 140 ° C., 160 ° C., 180 ° C., 200 ° C., 220 ° C., 240 ° C., 260 ° C., 280 ° C., 300 ° C. The amount of CO produced was measured. Quantification of ethyl acetate, 2-butanone, and 2-propanol was performed by gas chromatography (absolute calibration curve method) by holding the reactor at each temperature for about 30 minutes, sampling the gas passing through the reactor with a microsyringe. A CO concentration measuring device (manufactured by Test Corp.) was used for the quantitative determination of CO.

Examples 1-3 and Comparative Example 1:
Using catalysts A to D, 2-propanol decomposition performance was evaluated. The results are shown in Table 2.

Examples 4-6 and Comparative Example 2:
Using catalysts A to D, 2-butanone decomposition performance was evaluated. The results are shown in Table 3.

Examples 7-9 and Comparative Example 3:
Catalysts A to D were used to evaluate the ethyl acetate decomposition performance. The results are shown in Table 4.

Reference example 1:
An experiment similar to the above was performed using a catalyst in which 0.2% weight Pt was supported on an Al ₂ O ₃ support. The results are shown in Table 5.

(A) And (b) is a conceptual explanatory drawing of an example of the exhaust gas deodorizing apparatus which concerns on this invention.

Explanation of symbols

1: Odorous exhaust gas generation equipment 21: Exhaust gas blower 22: Exhaust gas blower for odorous exhaust gas generation equipment 3: Reactor 4: Temperature detection means 5: Temperature adjustment means

Claims (7)

  A titanium oxide carrier carries an oxide (component A) and Pt and / or Pd (component B) of at least one element selected from the group consisting of Cr, Fe, V, W, Mn, Mo, and Ce. A method for treating odorous exhaust gas, characterized in that the odorous exhaust gas is treated at a temperature of 180 to 300 ° C using a molded catalyst.   The amount of component A supported is 0.1 to 20% by weight based on the total amount of the titanium oxide support and component A, and the amount of component B supported is 0.001 to the total amount of all catalyst components. The method according to claim 1, which is 20% by weight.   The method according to claim 1 or 2, wherein component A is an oxide of vanadium and component B is Pd. The method according to claim 3, wherein the oxide of vanadium is V ₂ O ₅ .   The titanium oxide support is formed by supporting an oxide of Ni and / or Co (component C), and the supported amount is 0.01 to 10% by weight with respect to the total amount of all catalyst components. The method in any one.   The method according to any one of claims 1 to 5, wherein the odorous component in the exhaust gas is at least one selected from the group consisting of ethyl acetate, 2-butanone and 2-propanol.   A reactor provided between the odorous exhaust gas generation facility and the exhaust gas blower or after the exhaust gas blower for the odorous exhaust gas generation facility and filled with a catalyst therein, and temperature detection means for detecting the temperature of the catalyst And a temperature adjusting means for maintaining the temperature of the catalyst at 180 ° C. to 300 ° C. based on the temperature detected by the temperature detecting means, wherein the catalyst is a titanium oxide carrier. And forming an oxide (component A) of at least one element selected from the group consisting of Cr, Fe, V, W, Mn, Mo and Ce and Pt and / or Pd (component B). An exhaust gas deodorizing apparatus comprising a catalyst.