JP4499512B2 - Method for treating exhaust gas containing odor components - Google Patents

Description

  The present invention relates to a method for treating an exhaust gas containing an odor component, and more particularly to a method for efficiently removing an odor component by treating an exhaust gas containing an odor component in a low temperature range of 150 ° C. or higher and lower than 200 ° C.

  The exhaust gas discharged from incinerators contains nitrogen oxides (NOx), sulfur oxides (SOx), aldehydes, sulfides, fatty acids, amines, hydrocarbons, etc. Even in trace amounts, it is extremely odorous and how to remove these substances is a problem. In order to remove these substances, generally, a method of removing odor by desulfurizing the exhaust gas with an alkali scrubber, a method of adding ammonia to the exhaust gas and denitrating, etc. are employed. However, since the deodorization efficiency of aldehydes, sulfides, fatty acids, amines, etc. is low in the normally used denitration catalyst, in order to treat these substances, after denitration treatment, further deodorization is required. An oxidation catalyst is required.

  As the deodorization catalyst, for example, a binary composite oxide composed of titanium (Ti) and silicon (Si) is used as a carrier, and copper (Cu), chromium (Cr), iron (Fe), vanadium (V), Honeycomb carrying an oxide of at least one element selected from the group consisting of tungsten (W), manganese (Mn), nickel (Ni), cobalt (Co), molybdenum (Mo), and lead (Pb) A type deodorizing catalyst has been proposed (see Patent Document 1).

  Further, as a catalyst for simultaneously performing deodorization and denitration treatment of exhaust gas, a binary composite oxide composed of Ti and Si is used as a support, and Cu, Cr, Fe, V, W, Mn, Ni, Co, Mo, and An oxide of at least one element selected from the group consisting of Pb and at least one selected from the group consisting of platinum (Pt), palladium (Pd), rhodium (Rh), ruthenium (Ru) and iridium (Ir) An exhaust gas deodorization and denitration catalyst characterized by containing a catalyst C component which is a kind of noble metal or a compound thereof has been proposed (see Patent Document 2).

  However, Patent Documents 1 and 2 do not disclose the expression of deodorizing performance when each catalyst is used in a low temperature range of less than 200 ° C.

  On the other hand, as a method of removing nitrogen oxides in exhaust gas discharged from thermal power plants, garbage incinerators, etc., nitrogen oxides in exhaust gas are reduced and decomposed on the catalyst using a reducing agent such as ammonia or urea. A selective catalytic reduction (SCR) process that decomposes into harmless nitrogen and water is common. As a catalyst for removing nitrogen oxide (denitration catalyst) used for this, an oxide carrier containing Ti such as a titania carrier, a binary composite oxide carrier comprising Ti and Si, and a metal oxide such as V, W, and Mo However, these catalysts are designed to exhibit an efficient denitration function at a high temperature of 200 ° C. or higher, usually 250 ° C. or higher. It is. On the other hand, in recent years, utilization of thermal recycling of waste has been studied, and thermal energy obtained by burning waste is used for various purposes. There is an increasing demand to remove nitrogen oxides and odor components in gases discharged from these various thermal recycling facilities, but the exhaust gas temperature of this type of facility is as low as 200 ° C. There is a problem that a high-temperature type denitration catalyst cannot sufficiently exhibit both functions of denitration and deodorization.

  Conventionally, various catalyst systems have been proposed as this low-temperature type denitration catalyst. Among them, titanium oxide is used as a carrier and base metal oxide such as manganese (Mn) is supported as a main active component. As a catalyst, a catalyst in which a manganese oxide is supported on a titanium oxide support having a nitrate radical content as low as 0.1% by mass or less has been proposed (Patent Document 3). However, the deodorizing function is not described at all.

  Further, as a catalyst for denitration in the presence of ammonia in the temperature range of 200 to 500 ° C., a binary composite oxide composed of Ti and Si is used as a support, and V, W, Mo, Mn, Cu, Cr, Ce and A catalyst that supports an oxide of at least one element selected from the group consisting of Sn has been proposed (see Patent Document 4). However, this document does not disclose the denitration performance when the catalyst system is used in a temperature range below 200 ° C.

  Further, in the presence of a reducing agent such as hydrocarbons and ammonia in a temperature range of 200 to 250 ° C., a NOx oxidation catalyst such as a Ti—Mn system and a Ti—Cr system is disposed upstream of the exhaust gas flow, and then A method of denitration using a catalyst device in which a denitration catalyst is arranged on the flow side has been proposed (see Patent Document 5). However, in this document, there is no specific description regarding the catalyst composition, the catalyst preparation method, and the like for the NO oxidation catalyst such as Ti—Mn and Ti—Cr, and it is not possible to specify what the catalyst is.

  Furthermore, according to the study by the present inventors, as an odor component, for example, when an exhaust gas containing aldehydes is to be treated in a low temperature range of less than 200 ° C. using a known catalyst system as described above, aldehydes It can be removed with high degradation rates, but it has been found that undesirable compounds such as acetic acid may be by-produced and require further processing.

Japanese Examined Patent Publication No. 4-9581 Japanese Patent No. 3091820 JP-A-9-155190 Japanese Patent Publication No. 5-87291 (Claims, Examples 9, 10, and 11) JP-A-8-103636

  An object of the present invention is to efficiently decompose and remove odor components in a low temperature range where the exhaust gas temperature is 150 ° C. or higher and lower than 200 ° C. in the treatment of exhaust gas containing odor components in the absence of a reducing agent such as ammonia. It is to provide a method.

  In addition, the problem of the present invention is that, even in the case of exhaust gas containing odor components such as aldehydes, while suppressing the by-product of undesirable compounds such as acetic acid, in a low temperature range of 150 ° C. or more and less than 200 ° C., An object of the present invention is to provide a method for treating exhaust gas containing an odor component, which enables efficient deodorization treatment.

  According to the study by the present inventors, it was found that the above-mentioned problems can be solved by using a catalyst comprising (A) a composite oxide of titanium and silicon and (B) a manganese oxide as a deodorization catalyst. The present invention has been completed.

  That is, the present invention relates to a method for treating exhaust gas in which acetaldehyde or acetic acid, which is an odor component in exhaust gas, is decomposed and removed in the presence of a catalyst, and (A) titanium and silicon at a temperature of 150 ° C. or higher and lower than 200 ° C. It is made to contact the catalyst which consists of a complex oxide of (B), and a manganese oxide, The processing method of the waste gas containing the odor component characterized by the above-mentioned.

  According to the method of the present invention, odor components contained in exhaust gas can be efficiently decomposed and removed in a low temperature range of 150 ° C. or higher and lower than 200 ° C.

  Further, according to the method of the present invention, for example, in the case of exhaust gas containing acetaldehyde as an odor component while suppressing the generation of undesirable by-products, the exhaust gas containing an odor component is suppressed while suppressing by-product formation of undesirable acetic acid. It can be processed efficiently.

  Furthermore, according to the method of the present invention, acetic acid in exhaust gas can be decomposed and removed with high efficiency.

  The deodorization catalyst used in the present invention is composed of (A) a composite oxide of titanium and silicon and (B) a manganese oxide.

  Of the component (A), both Ti—Si composite oxide and Ti—Zr composite oxide are generally well known and can be easily prepared according to conventionally known methods.

  As the titanium source, in addition to titanium oxide, any inorganic and organic compound can be used as long as it can be baked to produce a titanium oxide. For example, an inorganic titanium compound such as titanium tetrachloride or titanium sulfate, or an organic titanium compound such as titanium oxalate or tetraisopropyl titanate can be used.

  As the silicon source, colloidal silica, water glass, fine silicon, inorganic silicon compounds such as silicon tetrachloride, and organic silicon compounds such as tetraethyl silicate can be used.

  As the zirconium source, inorganic zirconium compounds such as zirconium chloride and zirconium sulfate, and organic zirconium compounds such as zirconium oxalate can be used.

The Ti—Si composite oxide can be prepared, for example, by the following procedures (a) to (d).
(A) Silica sol and ammonia water are mixed, a sulfuric acid aqueous solution of titanium sulfate is added to cause precipitation, and the obtained precipitate is washed and dried, and then baked at 300 to 700 ° C.
(B) A sodium silicate aqueous solution is added to a titanium sulfate aqueous solution and reacted to cause precipitation. The obtained precipitate is washed and dried, and then baked at 300 to 700 ° C.
(C) Ethyl silicate (tetraethoxysilane) is added to a water-alcohol solution of titanium tetrachloride and then hydrolyzed to form a precipitate. The resulting precipitate is washed and dried, and then 300 to 700 ° C. Bake with.
(D) Ammonia is added to a water-alcohol solution of titanium oxide chloride (titanium oxytrichloride) and ethyl silicate to cause precipitation. The resulting precipitate is washed and dried, and then calcined at 300 to 700 ° C. To do.

Among the above methods, the method (a) is particularly preferable. Specifically, the ammonia source, the silicon source and the titanium source are each in an aqueous solution or a sol state, and each amount is a predetermined amount (the ammonia source is NH ₃ , the silicon source is SiO ₂ and the titanium source are converted to TiO ₂ . Next, an ammonia source and a silicon source were mixed, and while maintaining the mixed solution at 10 to 100 ° C., a titanium source was dropped into the mixed solution and kept at pH 2 to 10 for 1 to 50 hours. A silicon coprecipitate is produced, and this precipitate is filtered, washed thoroughly, dried at 80 to 140 ° C. for 10 minutes to 3 hours, and calcined at 300 to 700 ° C. for 1 to 10 hours. A Ti—Si composite oxide can be obtained.

  The Ti—Zr composite oxide may be prepared in accordance with the above-described method for preparing the Ti—Si composite oxide, and may be prepared using a water-soluble zirconium compound or the like as the zirconium source instead of the silica source.

The content of silicon or zirconium oxide in the Ti-Si composite oxide or Ti-Zr composite oxide is 0.560 mol%, preferably 1.5-60 mol%, based on titanium oxide. more preferably from 1.5 to 45 mol% (titanium, silicon and zirconium, respectively calculated as _TiO 2, SiO ₂ and ZrO _2).

  As the manganese source of component (B), in addition to manganese oxide, any inorganic and organic compounds can be used as long as they generate oxides by firing. For example, manganese-containing hydroxide, ammonium salt, oxalate, halide, sulfate, nitrate, carbonate, acetic acid and the like can be used.

  As the copper, chromium, iron and nickel sources, in addition to the respective oxides, any inorganic and organic compounds can be used as long as they generate oxides by firing. For example, hydroxides, ammonium salts, oxalates, halides, sulfates, nitrates, carbonates, acetic acids and the like containing each element can be used.

  The method for preparing the catalyst containing the components (A) and (B) of the present invention may be appropriately selected from known methods usually employed in this field such as a normal impregnation supporting method, a kneading method, and a dipping method. it can. For example, after obtaining a powder of a mixture of components (A) and (B), it is molded into a desired shape. In that case, each component may be prepared by mixing in the form of powder or slurry, or may be prepared by coprecipitation from a mixture of solutions of each salt. In addition, as a method of supporting the component (B) on the component (A), a method of adding the salt of the component (B) or a solution thereof to the powder or slurry mixture of the component (A), or from the component (A) A method of impregnating and supporting a solution of the salt of component (B) on the resulting molded body can be used.

About the composition of the catalyst of this invention, a component (B) is 0.1-40 mass% on the mass reference | standard of a component (A), Preferably it is 1-40 mass% (Ti-Si complex oxide is all Mass and manganese are converted as MnO ₂ ). When the content of the component (B) is less than 0.1% by mass of the component (A), the denitration activity is low. On the other hand, when the content exceeds 40% by mass, no significant improvement in activity is observed, and in some cases the activity is It may decrease.

The total pore volume measured by the mercury intrusion method of the deodorizing catalyst is preferably in the range of 0.2 to 0.6 cm ³ / g. If the total pore volume of the catalyst is smaller than 0.2 cm ³ / g, the deodorizing activity is low. On the other hand, if it exceeds 0.6 cm ³ / g, the mechanical strength of the catalyst is lowered, which is not preferable. BET specific surface area of the deodorizing catalyst 30~250m ² / g, preferably, from the 40 to 200 m ² / g. If the specific surface area of the catalyst is less than 30 m ² / g, the deodorizing activity is low, while if it exceeds 250 m ² / g, no significant improvement in activity is observed, and in some cases the accumulated amount of catalyst poisoning components increases. Thus, the catalyst life may be adversely affected.

Therefore, the deodorization catalyst contains component (B), particularly manganese oxide in a proportion of 0.1 to 40% by mass of component (A), and the total pore volume measured by the mercury intrusion method is 0.00. A catalyst having a specific surface area of ² to 0.6 cm ³ / g and a specific surface area by the BET method of 30 to 250 m ² / g is particularly preferably used.

  The shape of the deodorizing catalyst is not particularly limited, and may be used by molding into a desired shape selected from a plate shape, a corrugated plate shape, a net shape, a honeycomb shape, a columnar shape, a cylindrical shape, etc. You may carry | support and use on the support | carrier of the desired shape chosen from plate shape, corrugated plate shape, net shape, honeycomb shape, cylindrical shape, cylindrical shape etc. which consist of silica, cordierite, titania, stainless steel, etc.

  The deodorizing catalyst is used for processing various exhaust gases containing odor components. There are no particular restrictions on the composition of the exhaust gas, but aldehydes, sulfides, fatty acids, amines, hydrocarbons, nitrogen dioxide, etc. emitted from boilers, incinerators, gas turbines, diesel engines and various industrial processes Therefore, it is suitably used for the treatment of exhaust gas containing these odor components.

  According to the method of the present invention, the deodorizing treatment is performed by bringing the exhaust gas containing the deodorizing component into contact with the deodorizing catalyst at a temperature of 150 ° C. or higher and lower than 200 ° C. The conditions for the deodorizing treatment can be determined by appropriately selecting from the conditions generally used for the deodorizing treatment, except that the temperature of the exhaust gas is maintained in the range of 150 ° C. or higher and lower than 200 ° C.

The space velocity of the exhaust gas, usually, 100～100000Hr ^- a ¹ (STP), preferably 200～50000Hr ^- a ¹ (STP). 100 hr ^- it is less than ^1, the processing apparatus becomes inefficient because too large, whereas 100000Hr ^{- 1} and more than decomposition efficiency is lowered.

  The temperature of the exhaust gas when performing the deodorizing treatment of the present invention is 150 ° C. or more and less than 200 ° C., preferably 170 to 200 ° C. If the exhaust gas temperature is lower than 150 ° C., the denitration efficiency is lowered, which is not preferable.

  The sulfur oxide (SOx) concentration in the exhaust gas is preferably 1% or less. This is because when the SOx concentration in the exhaust gas exceeds 1%, the catalyst activity deteriorates greatly.

  The invention is further illustrated by the following examples, which illustrate advantageous embodiments of the invention.

Catalyst preparation example 1

After adding 21.3 kg of SNOWTEX-20 (silica sol manufactured by Nissan Chemical Co., Ltd., containing about 20% by mass of SiO ₂ ) to 700 L of 10% by mass ammonia water, stirring and mixing, a sulfuric acid solution of titanyl sulfate (TiO ₂₎ (125 g / liter, sulfuric acid concentration 550 g / liter) was gradually added dropwise with stirring. The obtained gel was allowed to stand for 20 hours, filtered, washed with water, and then dried at 150 ° C. for 10 hours. This was baked at 500 ° C. to obtain a powder. The composition of the obtained powder is TiO ₂ : SiO ₂ = 8.5: 1.5 (molar ratio), and clear intrinsic peaks of TiO ₂ and SiO ₂ are recognized in the X-ray diffraction chart of the powder. In addition, it was confirmed by a broad diffraction peak that it was a composite oxide of titanium and silicon (Ti-Si composite oxide) having an amorphous microstructure.

  Add organic binder (starch 0.5kg) to 10kg of the above Ti-Si composite oxide, mix, mix well with a blender while adding an appropriate amount of water, knead well with a continuous kneader, and extrude into a honeycomb. did. The shape was formed into a lattice shape having an opening of 4.35 mm, a thickness of 0.6 mm, and a length of 500 mm. Next, the obtained molded product was dried at 80 ° C. and then fired at 450 ° C. for 5 hours in an air atmosphere.

The molded body is impregnated with an aqueous solution of manganese nitrate [Mn (NO ₃ ) ₂ .6H ₂ O] (300 g-Mn / liter), then dried at 120 ° C. and calcined at 420 ° C. for 3 hours to give catalyst (a). Obtained. The composition of the catalyst (a) was Ti—Si composite oxide: MnO ₂ = 75: 25 (mass ratio) (component (B) / component (A) = 33.3 mass%).

Catalyst preparation example 2

9.15 kg of manganese nitrate [Mn (NO ₃ ) ₂ .6H ₂ O] aqueous solution (200 g-Mn / liter) was added to 10 kg of the Ti—Si composite oxide obtained in Catalyst Preparation Example 1, and an appropriate amount of water was further added. While mixing well with a blender, the mixture was sufficiently kneaded with a continuous kneader and extruded into a honeycomb shape. The shape was formed into a lattice shape having an opening of 4.35 mm, a thickness of 0.6 mm, and a length of 500 mm. Next, the obtained molded body was dried at 80 ° C. and then calcined at 450 ° C. for 5 hours in an air atmosphere to obtain a catalyst (b). The composition of the catalyst (b) was Ti—Si composite oxide: MnO ₂ = 75: 25 (mass ratio) (component (B) / component (A) = 33.3 mass%).

Catalyst preparation example 3

In the catalyst preparation example 1, except that the amount of manganese nitrate used was changed, similarly, Ti—Si composite oxide: MnO ₂ = 85: 15 (mass ratio) (component (B) / component (A) = 17. A catalyst (c) having a composition of 6% by mass was obtained.

Catalyst preparation example 4 Catalyst preparation example 5 Catalyst preparation example 6 Catalyst preparation example 7

  A uniform vanadium and tungsten-containing solution was prepared by mixing and dissolving 1.29 kg of ammonium metavanadate, 1.12 kg of ammonium paratungstate, 1.67 kg of oxalic acid and 0.85 kg of monoethanolamine in 8 liters of water.

After 18 kg of the Ti-Si composite oxide obtained in Catalyst Preparation Example 1 was put into a kneader, the above vanadium and tungsten-containing solution was added together with an organic binder (starch 0.5 kg) and stirred well. Furthermore, after adding a proper amount of water and mixing well with a blender, the mixture was sufficiently kneaded with a continuous kneader and extruded into a honeycomb shape. The shape was formed into a lattice shape having an opening of 4.35 mm, a thickness of 0.6 mm, and a length of 500 mm. Next, the obtained molded product was dried at 60 ° C. and then calcined at 450 ° C. for 5 hours in an air atmosphere to obtain a comparative catalyst ( d ).

The composition of this comparative catalyst ( d ) was Ti—Si composite oxide: V ₂ O ₅ : W ₂ O ₃ = 90: 5: 5 (mass ratio).
(Catalyst Preparation Example 5)

Catalyst preparation example 8

The comparative catalyst ( d ) shaped body obtained in Catalyst Preparation Example 4 was impregnated with an aqueous platinum nitrate solution, then dried at 100 ° C., and calcined at 450 ° C. for 3 hours to obtain a comparative catalyst ( e ). The composition of this comparative catalyst ( e ) was Ti—Si composite oxide: V ₂ O ₅ : W ₂ O ₃ : Pt = 89.8: 5: 5: 0.2 (mass ratio).
(Catalyst Preparation Example 6)

Catalyst preparation example 9

The molded product of the comparative catalyst ( d ) obtained in Catalyst Preparation Example 4 was impregnated with palladium nitrate, then dried at 100 ° C., and calcined at 450 ° C. for 3 hours to obtain a comparative catalyst ( f ). The composition of this comparative catalyst ( f ) was Ti—Si composite oxide: V ₂ O ₅ : W ₂ O ₃ : Pd = 89.8: 5: 5: 0.2 (mass ratio).
(Example 1)

Activity tests were performed on the catalysts (a) to ( c ) obtained in Catalyst Preparation Examples 1 to 6 and the comparative catalysts ( d ) to ( f ). Each honeycomb-type catalyst was cut into an outer shape of 15.5 mm (3 × 3 cells) and a length of 126 mm, and this was packed into a catalyst reactor having a diameter of 35 mm so as to be parallel to the gas flow direction. Two types of synthesis gas of the following composition-1 and composition-2 were flowed to this apparatus at 0.5 Nm <3> / h.
(Gas composition-1) Acetaldehyde: 50 ppm, SO ₂ : 0 ppm, H ₂ O: 10%, N ₂ : Balance (Gas composition-2) Acetic acid: 50 ppm, SO ₂ : 0 ppm, H ₂ O: 10%, N ₂ : Balance (gas temperature) 150 ° C, 180 ° C, 195 ° C
The acetaldehyde removal rate, the acetic acid removal rate, and the acetic acid production rate were determined according to the following formulas.
Acetaldehyde removal rate (%) = [(reactor inlet acetaldehyde concentration) − (reactor outlet acetaldehyde concentration)] ÷ (reactor inlet acetaldehyde concentration) × 100
Acetic acid removal rate (%) = [(reactor inlet acetic acid concentration) − (reactor outlet acetic acid concentration)] ÷ (reactor inlet acetic acid concentration) × 100
Acetic acid production rate (%) = (reactor outlet acetic acid concentration) ÷ (reactor inlet acetaldehyde concentration) × 100
The results of gas composition-1 and gas composition-2 are shown in Table 1 and Table 2, respectively.

Claims (4)

  In a method for treating exhaust gas in which acetaldehyde or acetic acid, which is an odor component in exhaust gas, is decomposed and removed in the presence of a catalyst, the exhaust gas is treated at a temperature of 150 ° C. or higher and lower than 200 ° C. (A) a composite oxide of titanium and silicon ( B) A method for treating an exhaust gas containing an odor component, which is brought into contact with a catalyst comprising manganese oxide.   The method for treating an exhaust gas containing an odor component according to claim 1, wherein the amount of the component (B) is 0.1 to 40% by mass of the component (A). Method of processing an exhaust gas total pore volume measured by mercury porosimetry of catalyst containing odorous components of claim 1 or 2 wherein the 0.2~0.6cm 3 / ^g. The method for treating exhaust gas containing an odor component according to any one of claims 1 to 3, wherein the catalyst has a specific surface area of 30 to 250 m ² / g as measured by the BET method.