JPH049582B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a honeycomb type deodorizing catalyst. Specifically, the present invention converts foul-smelling exhaust gas containing a large amount of dust, which is generated from various end-stage sources, into a harmless, odorless gas by contacting the exhaust gas without deteriorating the performance due to abrasion or peeling of the catalyst component due to dust, and without clogging. This invention relates to a honeycomb-type deodorizing catalyst that converts and removes odors. In recent years, various types of foul-smelling exhaust gases, such as organic solvent-based foul-smelling exhaust gases generated from printing, painting, resin processing, and surface treatment factories, and dust-containing foul-smelling exhaust gases generated from garbage incinerators, scrap preheating furnaces, etc., have become increasingly important from an occupational health perspective. However, they have also become a problem in terms of environmental health, and from the standpoint of pollution prevention, there is an urgent need to remove these foul-smelling components. Conventional methods for removing these foul-smelling exhaust gases include (1) atmospheric diffusion using odor stacks, (2) direct combustion, (3) cleaning using scrubbers, and (4) adsorption using adsorbents such as activated carbon. However, each has the following drawbacks. In other words, method (1) is effective only when the amount of bad odor generated is small, and method (2) requires high temperatures of 750 to 900°C, which is disadvantageous due to its high fuel cost and also produces nitrogen oxide (NOx) by-products. There is a risk of secondary pollution, method (3) increases the cost of wastewater treatment, and method (4) involves complicated operations such as regenerating and replacing the adsorbent. For the reasons mentioned above, there are very few cases in which these methods have been put into practical use as decisive methods for deodorization. On the other hand, there is a catalytic combustion deodorization method that improves the above-mentioned drawbacks, and since this method is effective at relatively low temperatures (150 to 450°C), fuel costs are low and it is suitable for secondary treatment such as wastewater treatment. It is currently in practical use because it has advantages such as no need for it and there is no need to worry about NOx by-products because it is processed at low temperatures. The catalysts used in this catalytic combustion deodorization method are granular activated alumina supported with noble metals such as platinum and palladium, and base metals such as copper, chromium, and iron.Recently, catalysts used in automobile exhaust gas purification have also been used. Catalysts have been put into practical use in which active alumina is supported on a cordierite honeycomb type carrier with a small pore diameter, and noble metals such as platinum and palladium are supported in a thin layer on the surface. However, granular catalysts have high ventilation resistance and cannot process exhaust gas at high linear velocity.
Therefore, it is necessary to have a large exhaust gas flow cross-sectional area, which increases the area occupied by the reactor, and when treating dust-containing exhaust gas, clogging increases ventilation resistance, leading to increased running costs. ing. On the other hand, when a catalyst using a cordierite honeycomb type carrier is used to treat dust-containing exhaust gas, the noble metal catalyst material thinly supported on the surface is abraded and peeled off by the hard fine powder in the dust, resulting in a decrease in activity. Due to the small pore size, airflow resistance increases due to clogging.
Furthermore, when exhaust gas containing several g/Nm ³ of dust is vented through the catalyst, it has the disadvantage that it becomes clogged to the extent that it cannot be used within one to two days. More specifically, it is as follows. Catalysts conventionally used for deodorization, in which noble metals such as platinum and palladium and base metals such as copper, chromium and iron are supported on granular activated alumina as a carrier, have a particle size of 2 to 6 mmφ. It is.
However, this granular catalyst has a space velocity of 10,000 ~
When used at 30,000 Hr ^-1 , the catalyst layer length is limited to about 200 mm due to the catalyst layer ventilation resistance, which results in a large reactor installation cross-sectional area. Furthermore, when processing foul-smelling exhaust gas containing a large amount of dust, such as scrap preheating furnace exhaust gas, rubber incinerator exhaust gas, sintering furnace exhaust gas, foundry exhaust gas, etc., even with a layer length of about 100 mm, ventilation resistance increases due to dust clogging in a short period of time. This increases running costs and requires complicated operations such as frequent catalyst cleaning and catalyst replacement, and conventional honeycomb-type deodorizing catalysts have pores of 100 to 300 per square inch and a pore diameter of 1 to 2 mm. Generally used is a cordierite honeycomb carrier supporting activated alumina, and a thin layer of precious metals such as platinum or palladium being supported on the carrier. When this catalyst is used to treat the above-mentioned dust-containing foul-smelling exhaust gas, there are problems such as abrasion of the surface metal catalyst due to dust, performance deterioration due to peeling, and increased ventilation resistance due to clogging due to the small pore diameter. When this honeycomb type catalyst is used at a space velocity of 10,000 to 50,000 Hr ^-1 , the catalyst layer length is limited to about 400 mm due to the catalyst layer ventilation resistance, and like the granular catalyst, the device becomes large-scale. There is. The fact that the catalyst layer length has to be shortened means that the exhaust gas cannot be processed at a high linear velocity, which means that the gas flow inside the catalyst pores becomes more laminar and less turbulent, which leads to dust. It is also one of the causes of clogging.
As a countermeasure against dust clogging, it is possible to use an electrostatic precipitator, bag filter, etc. to remove dust and then deodorize it. However, when using a bag filter, for example, its heat resistance is low, so it is necessary to cool the exhaust gas once before removing dust. Therefore, it is necessary to heat the exhaust gas again by burning a fuel such as butane to the treatment temperature before entering the catalyst layer, which increases fuel costs and running costs accordingly.The exhaust gas is deodorized by containing dust. The method is extremely advantageous. In addition, as a deodorizing carrier, it has a relatively large pore size (pore size 4
mm) There are also honeycomb-shaped mullite and alumina carriers, and catalysts in which catalyst materials are directly supported on these carriers are also considered, but when mullite carriers are used, there are problems with the physical properties of the catalyst, i.e. ,
BET surface area less than 1 m ² /g, pore volume 0.25
As it is less than cc/g, it is not fully satisfactory in terms of catalyst performance, and even when an alumina support is used, there are problems with poisoning by sulfur compounds (SOx) contained in exhaust gas and wear resistance against dust. . Thus, in view of the above-mentioned drawbacks, the present invention can employ a higher linear velocity than these conventional products, and especially when treating dust-containing exhaust gas, there is no performance deterioration due to abrasion or peeling of the catalyst material, and furthermore, clogging due to dust can be prevented. The purpose of the present invention is to provide a honeycomb type deodorizing catalyst. The present invention is specified as follows. (1) At least one selected from the group consisting of titanium, silicon, and zirconium as catalyst A component
oxide of at least one element selected from the group consisting of copper, chromium, iron, vanadium, tungsten, manganese, nickel, cobalt, molybdenum, cerium, calcium and lead as catalyst B component; and a catalyst composition comprising as a catalyst component at least one noble metal selected from the group consisting of platinum, palladium, rhodium, ruthenium and iridium, and this composition has a plurality of pores with an average pore diameter in the range of 3 to 12 mm. A honeycomb-type deodorizing catalyst characterized by being molded into an integral structure having through-holes. (2) The above product in which catalyst B component and catalyst C component are dispersed and supported on a molded body of catalyst A component.
(1) Catalyst as described. (3) The catalyst according to (1) above, wherein the catalyst C component is dispersed and supported on a molded body consisting of the catalyst A component and the catalyst B component. The present invention will be explained in more detail below. The pore diameter of the honeycomb catalyst (equivalent diameter of through holes)
If the pore size is increased, the ventilation resistance decreases proportionally and clogging due to dust can be prevented, but at the same time, the geometric surface area of the catalyst also decreases, and in order to achieve a certain level of processing efficiency, the amount of catalyst must be reduced to compensate for the increased pore diameter. Since it is necessary to increase the number of pores, the pore size is limited in relation to treatment efficiency and catalyst performance. As a result of intensive studies including the selection of the catalyst material, the inventors found that the catalyst specified above satisfies the catalytic performance targeted by the present invention, and there is no performance deterioration due to abrasion or peeling of the catalyst material due to dust. The present invention was achieved by discovering that clogging can be prevented and high space velocities can be adopted. According to the findings of the present inventors, aluminum oxide can also be used as the catalyst A component, but when aluminum oxide is used alone as the A component, the wear resistance against the catalyst and dust caused by SOx contained in exhaust gas may be affected. However, when an aluminum component is used, the purpose of the present invention can be achieved by using it in a mixed system with other A components. The shape of the through hole employed in the present invention may be square, hexagonal, wavy, or any other shape as long as its equivalent diameter is within the above range. The proportion of the catalyst components used in the catalyst of the present invention is 30 to 99% by weight of component A in the form of oxide, preferably
40-90% by weight, component B is 1 in oxide form
A range of from 0.01 to 0.6 weight percent, preferably from 0.03 to 0.4 weight percent of the C component in metallic form is suitable. The starting material can be appropriately selected from oxides, hydroxides, inorganic acid salts, organic acid salts, etc., especially ammonium salts, nitrates, sulfates, and halides. Since the catalyst of the present invention is impregnated and supported with a catalytic material as described above, the catalytic material is uniformly distributed throughout the interior, and even if the surface layer is worn away or peeled off by dust, a new catalytic surface is exposed, resulting in wear and tear. There is no performance deterioration due to peeling, and the catalyst has a satisfactory lifespan. The ventilation resistance of the catalyst of the present invention is less than 1/100 that of the granular catalyst.
This is less than 1/10 compared to the conventionally used honeycomb catalyst, which has relatively small pores, and the gas superficial velocity of the honeycomb catalyst layer is approximately 10 m/sec. can take speed,
Therefore, the design of the catalytic reactor becomes easy, and a compact reactor that is vertically long and has a small exhaust gas flow cross-sectional area can be manufactured. In addition, TiO ₂ −SiO ₂ − is used as a preparation method for this catalyst.
In the V ₂ O ₅ -Pd system, it is as follows. first
Prepare _TiO2 - _SiO2 . A titanium salt such as titanium tetrachloride or titanium sulfate is mixed with silica sol and ammonia is added to form a precipitate. After washing and drying, the precipitate is calcined at 150 to 850°C to form a binary TiO ₂ -SiO ₂ oxide. I can do it. TiO ₂ -SiO ₂ obtained by the above method and organic forming aids such as methyl cellulose, polyethylene oxide, polyacrylamide, polyvinyl alcohol, starch and an appropriate amount of water that are decomposed and scattered during firing are added and thoroughly kneaded, and then formed into a honeycomb mold. Extrusion molding. It is also possible to add glass fiber, glass powder, etc. to increase the strength of the catalyst. After that, this molded body
Dry at 50 to 150℃, and further under an atmosphere with appropriately controlled oxygen concentration at 300 to 700℃, preferably 350 to 600℃.
The desired molded body can be obtained by firing at a temperature of 1 to 10 hours, preferably 2 to 6 hours. The obtained molded body is impregnated in an aqueous solution containing a vanadium compound or an aqueous solution of oxalic acid or hydrochloric acid, and after drying.
Firing treatment is carried out at 300 to 700°C, preferably 350 to 600°C, for 1 to 10 hours, preferably 2 to 6 hours. In addition, if the predetermined amount of vanadium cannot be supported by one impregnation, the predetermined amount of vanadium can be supported by repeating the operations of further impregnating the dried and calcined catalyst with a vanadium compound-containing solution, drying, and calcining. . The thus obtained molded body is impregnated in an aqueous solution containing a palladium compound or an aqueous solution of nitric acid or hydrochloric acid, and after drying,
The desired catalyst can be obtained by calcining at 350 to 600°C for 1 to 10 hours, preferably 2 to 6 hours. The desired catalyst can also be obtained by impregnating the molded body with a mixed solution of vanadium and palladium and then performing the same operations as described above. Alternatively, TiO ₂ − prepared according to the method described above
Mix an aqueous solution containing SiO ₂ and a vanadium compound, or an aqueous solution of oxalic acid or hydrochloric acid, then add a molding aid of organic matter that decomposes and scatters during firing, such as methyl cellulose, polyethylene oxide, polyacrylamide, polyvinyl alcohol, starch, and an appropriate amount of water, and mix thoroughly. After that, it is extruded into a honeycomb mold. After that, this molded body is dried at 50 to 150℃ and further in an atmosphere with an appropriately controlled oxygen concentration.
It is baked at 300-700°C, preferably 350-600°C for 1-10 hours, preferably 2-6 hours. The thus obtained molded body is impregnated in an aqueous solution containing a palladium compound or an aqueous nitric acid or hydrochloric acid solution, dried and then fired at 300 to 700°C, preferably 350 to 600°C for 1 to 10 hours, preferably 2 to 6 hours. The desired catalyst can be obtained. The catalyst of the present invention thus prepared by the method described above has a BET surface area of 30 to 180 m ² /g and a pore volume of 0.3 to 0.5 cc/g. Examples of the exhaust gas to be treated using the catalyst of the present invention include enameled wire baking furnace exhaust gas,
Exhaust gas containing organic solvents such as color iron plate baking furnace exhaust gas and offset printing rotary press exhaust gas, such as cresol, phenol, formalin, xylene, toluene, benzene, etc., formaldehyde-containing exhaust gas discharged during the synthetic fiber manufacturing process, phthalic anhydride, Exhaust gas containing various flammable organic compounds with a strong pungent odor from the maleic anhydride manufacturing process, exhaust gas containing styrene and methanol emitted from the resin processing process, and other foul odors emitted from paper mills, foundries, urban cleaning facilities, etc. Regarding exhaust gas, the catalyst of the present invention is particularly effective against bad odors such as scrap preheating furnace exhaust gas and garbage incinerator exhaust gas, which have a large dust content (5 to 40 g/m ³ ) and contain hard metal oxides such as iron oxide. Demonstrates excellent effectiveness in treating exhaust gas. Example 1 A binary oxide containing titanium and silicon (TiO ₂ -SiO ₂ ) was prepared by the method described below.
11.4Kg of titanium tetrachloride [TiCl ₄ ] was gradually added dropwise to 80% of water while stirring on ice, and then Snotex-O
(4.5 kg of silica sol manufactured by Nissan Chemical, containing 20 to 21% by weight as SiO ₂ ) was added. While maintaining the temperature at about 30°C and stirring well, ammonia water was gradually added dropwise to the mixture until the pH reached 7, and the mixture was left to mature for 2 hours. That's how I got it
The TiO ₂ -SiO ₂ gel was washed with water, dried at 120°C for 10 hours, further washed with water, and then fired at 500°C for 3 hours.
The composition of the obtained powder is TiO ₂ /SiO ₂ as an oxide.
=4 (molar ratio). 900ml of water and 1500ml of said powder
gFurthermore, 75 g of starch was added, mixed well, and kneaded thoroughly with a kneader. After kneading while adding an appropriate amount of water, the pore diameter (equivalent diameter of the through hole) was 4.
It was extruded into three types of honeycomb molds with mm, 6 mm, and 8 mm porosity of 64%, dried at 120°C for 6 hours, and then fired at 450°C for 6 hours in an atmosphere with an oxygen concentration of 15% or less. . 500g of oxalic acid and 600c.c. of water.
ammonium metavanadate dissolved in
The molded body was immersed in the solution in which 467 g was added and dissolved for 2 minutes, dried at 120°C for 6 hours, and then baked at 450°C for 6 hours in an air atmosphere. The molded body thus obtained was immersed in an aqueous palladium nitrate solution with a palladium concentration of 1.6 gPd/d for 2 minutes, and then heated at 120°C.
After drying for 6 hours at 450° C. in an air atmosphere, it was fired for 6 hours. The composition of the finished catalyst obtained was TiO ₂ −SiO ₂ :V ₂ O ₅ :Pd=89.95:10:0.05 in weight percentage.
The BET surface area was 115 m ² /g and the pore volume was 0.36 cc/g. Using this catalyst, forced abrasion and peeling tests were conducted under an air flow with a dust concentration of 10 g/Nm ³ and a superficial linear velocity of 35 m/sec.
The test was carried out for 100 hours, and the catalysts before and after the test were subjected to an exhaust gas treatment test (Experiment-A) in which the main malodorous substance was acetaldehyde. In addition, this catalyst can be applied to dust concentration
A forced clogging test (Experiment-B) was conducted at 15 g/Nm ³ and a superficial linear velocity of 15 and 30 m/sec. For comparison, a similar test was conducted using a conventional type of honeycomb catalyst. Conventional type honeycomb catalyst has equivalent diameter of through holes.
Activated alumina was supported on a 1.5 mm (210 cells/square inch) cordierite honeycomb carrier, and 0.3 weight percent (2 g) of palladium was added as a catalyst material.
Pd/) was used.

[Table] Test conditions SV = 10000Hr ^-1 , temperature 350℃ Gas composition: 300ppm aldehyde, 20% H ₂ O, remaining air Dust: Average particle size 13μ (main component iron oxide) From the above test results, the catalyst of the present invention is caused by dust. No performance deterioration due to wear or peeling was observed, whereas performance deterioration of conventional catalysts was significant.

[Table] From the above test results, no clogging or increase in ventilation resistance was observed in the catalyst of the present invention, whereas the increase in ventilation resistance in the conventional catalyst was significant. Example ₂ TiO2- _SiO2 was prepared as in Example 1. The composition of the obtained powder is as an oxide.
TiO ₂ /SiO ₂ =4 (molar ratio). oxalic acid 420g
was dissolved in 900ml of water, 214g of ammonium metavanadate was added to the solution, and the above powder was added to the dissolved solution.
1500 g and 75 g of starch were added and mixed well, and kneaded well with a kneader. After kneading while adding an appropriate amount of water, each pore size (equivalent diameter of the through hole)
It was extruded into three types of honeycomb molds of 4 mm, 6 mm, and 8 mm, each with a porosity of 64%, and dried at 120°C for 6 hours.
Then, in an atmosphere where the oxygen concentration was adjusted to 15% or less.
It was baked at 450°C for 6 hours. and palladium concentration
The molded body was immersed in an aqueous solution of palladium nitrate containing 1.6 g Pd for 2 minutes, dried at 120° C. for 6 hours, and then fired at 450° C. for 6 hours in an air atmosphere. The composition of the finished catalyst obtained is TiO ₂ − in weight percentage.
BET surface area with SiO ₂ :V ₂ O ₅ :Pd=89.95:10:0.05
The area was 120 m ² /g, and the pore volume was 0.38 cc/g. Tests similar to those in Example 1 were conducted using this catalyst, and the results shown in Table 3 were obtained.

[Table] Examples 3 to 8 Using the same TiO ₂ -SiO ₂ powder as used in Example 1, following the preparation method of Example 1, changing the catalyst components added to TiO ₂ -SiO ₂ . A catalyst having the composition shown was prepared. Copper nitrate, cobalt nitrate, iron nitrate, palladium nitrate, and platinum nitrate were used as starting materials. The composition of the finished catalyst obtained is expressed as a weight percentage.
_TiO2 - _SiO2 :CuO:Pd=89.95:10:0.05 (Example 3), TiO2 _{- SiO2} :CoO:Pd=89.95:10:
0.05 (Example 4), _TiO2 - _SiO2 : _Fe2O3 : _Pd =
89.95:10:0.05 (Example 5), _TiO2 - _SiO2 :
CuO:Pt=89.95:10:0.05 (Example 6), TiO ₂ −
_SiO2 :CoO:Pt=89.95:10:0.05 (Example 7),
TiO ₂ −SiO ₂ :Fe ₂ O ₃ :Pt=89.95:10:0.05 (Example 8) with a BET surface area in the range of 115 to 117 m ² /g, respectively;
The pore volumes each ranged from 0.35 to 0.37 cc/g.
Tests similar to those in Example 1 were conducted using each of the catalysts, and the results shown in Table 4 were obtained.

[Table] Examples 9 to 12 Using the same TiO ₂ -SiO ₂ powder used in Example 1, the catalyst was prepared according to the preparation method of Example 1 by changing the catalyst components added to TiO ₂ -SiO ₂ . Using the prepared catalyst, the same treatment test as in Example 1 was conducted, and the results are shown in Table 5. The composition of the completed catalyst was _TiO2 - _SiO2 : catalyst B component: catalyst C component = 89.95:10:0.05 by weight.

[Table] Example 13 Example 1 except that 11.4 kg of titanium tetrachloride and 4.8 kg of zirconium acid chloride (ZrOCl ₂ 8H ₂ O) were used.
A binary oxide powder (TiO ₂ -SiO ₂ ) containing titanium and zirconium was prepared according to the method. The composition of the obtained powder was _TiO2 - _SiO2 =4 (molar ratio). Using the obtained powder, the same preparation as in Example 1 was carried out to obtain a catalyst. The composition of the obtained finished catalyst is TiO ₂ −SiO ₂ :V ₂ O ₅ :Pd= in weight ratio.
89.95:10:0.05, the BET surface area was 80 m ² /g, and the pore volume was 0.33 cc/g. Tests similar to those in Example 1 were conducted using this catalyst, and the results shown in Table 6 were obtained.

[Table] Example 14 Binary oxide powder (TiO ₂ -SiO ₂ ) containing silicon and zirconium was prepared according to Example 1 except that 18.0 kg of Snowtex-O and 4.8 kg of zirconium chloride were used. . The composition of the obtained powder was SiO ₂ /ZrO ₂ =4 (molar ratio). Using the obtained powder, the same preparation as in Example 1 was carried out to obtain a catalyst. The composition of the obtained finished catalyst is TiO ₂ −SiO ₂ :V ₂ O ₅ :Pd= in weight ratio.
The ratio was 89.95:10:0.05, the BET surface area was 130 m ² /g, and the pore volume was 0.38 cc/g. Tests similar to those in Example 1 were conducted using this catalyst, and the results shown in Table 7 were obtained.

[Table] Example 15 Titanium tetrachloride 11.4Kg, Snowtex-O 3.6Kg
A ternary oxide powder containing titanium, silicon and zirconium (TiO ₂ −SiO ₂ −
ZrO ₂ ) was prepared. The composition of the obtained powder is
TiO ₂ /SiO ₂ /ZrO ₂ =20/4/1 (molar ratio). Using the obtained powder, the same preparation as in Example 1 was carried out to obtain a catalyst. The composition of the obtained finished catalyst is as follows in weight ratio: TiO ₂ −SiO ₂ −ZrO ₂ :V ₂ O ₅ :
Pd=89.95:10:0.05, BET surface area 110m ² /g,
The pore volume was 0.34 cc/g. Tests similar to those in Example 1 were conducted using this catalyst, and the results shown in Table 8 were obtained.

[Table] Example 16 Titanium oxide powder (TiO ₂ ) was prepared according to Example 1 except that Snowtex-O was not added. Using the obtained powder, the same preparation as in Example 1 was carried out to obtain a catalyst. The composition of the finished catalyst obtained was TiO ₂ :V ₂ O ₅ :Pd=89.95:
10:0.05, BET surface area 60m ² /g, pore volume 0.32
It was cc/g. Tests similar to those in Example 1 were conducted using this catalyst, and the results shown in Table 9 were obtained.

【table】

Claims (1)

[Claims] 1. Catalyst A component is an oxide of at least one element selected from the group consisting of titanium, silicon, and zirconium; catalyst B component is copper, chromium,
An oxide of at least one element selected from the group consisting of iron, vanadium, tungsten, manganese, nickel, cobalt, molybdenum, cerium, calcium and lead, and a catalyst C component consisting of platinum, palladium, rhodium, ruthenium and iridium. A catalyst composition comprising at least one noble metal selected from the group consisting of at least one noble metal as a catalyst component, and this composition is molded into an integral structure having a plurality of through holes with an average pore diameter in the range of 3 to 12 mm. A unique honeycomb deodorizing catalyst. 2. The catalyst according to claim 1, wherein catalyst B component and catalyst C component are dispersedly supported on a molded body of catalyst component A. 3. The catalyst according to claim 1, wherein the catalyst C component is dispersedly supported on a molded body consisting of the catalyst A component and the catalyst B component.