CA1091899A - Method for removal of nitrogen oxides from nitrogen oxides-containing exhaust gas - Google Patents
Method for removal of nitrogen oxides from nitrogen oxides-containing exhaust gasInfo
- Publication number
- CA1091899A CA1091899A CA304,764A CA304764A CA1091899A CA 1091899 A CA1091899 A CA 1091899A CA 304764 A CA304764 A CA 304764A CA 1091899 A CA1091899 A CA 1091899A
- Authority
- CA
- Canada
- Prior art keywords
- catalyst
- nitrogen oxides
- exhaust gas
- manganese
- removal
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8621—Removing nitrogen compounds
- B01D53/8625—Nitrogen oxides
- B01D53/8628—Processes characterised by a specific catalyst
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
- B01J23/16—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of arsenic, antimony, bismuth, vanadium, niobium, tantalum, polonium, chromium, molybdenum, tungsten, manganese, technetium or rhenium
- B01J23/32—Manganese, technetium or rhenium
- B01J23/34—Manganese
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
- B01J37/08—Heat treatment
Abstract
METHOD FOR REMOVAL OF NITROGEN OXIDES
FROM NITROGEN OXIDES-CONTAINING EXHAUST GAS
Abstract of the Disclosure Nitrogen oxides can be advantageously removed from an exhaust gas containing nitrogen oxides by contacting the exhaust gas with ammonia in the presence of a catalyst com-prising a manganese oxide product obtained by thermally treating manganese carbonate at a temperature of from 200 to 500°C in an atmosphere of a gas containing not less than 1%
by volume of oxygen. The manganese oxide product used in the method is inexpensive to prepare and is an effective catalyst, particularly because of the fact that it is quite porous.
FROM NITROGEN OXIDES-CONTAINING EXHAUST GAS
Abstract of the Disclosure Nitrogen oxides can be advantageously removed from an exhaust gas containing nitrogen oxides by contacting the exhaust gas with ammonia in the presence of a catalyst com-prising a manganese oxide product obtained by thermally treating manganese carbonate at a temperature of from 200 to 500°C in an atmosphere of a gas containing not less than 1%
by volume of oxygen. The manganese oxide product used in the method is inexpensive to prepare and is an effective catalyst, particularly because of the fact that it is quite porous.
Description
1~J91899 This invention relates to a method for removing nil:rogen oxides (hereinafter referred to as NOX) from exhaust gases containing the same, by contacting the exhaust gases wi1h ammonia in the presence of a manganese oxide product.
Various methods have been heretofore suggested for the removal of NOX from NOx-containing exhaust gases such as those issuing from combustion sources. Among them, a method which resorts to contact reduction using ammonia as the reducing agent is considered to be highly promising because it is amply effective even when it is used for the treatment of exhaust gases of the type containing NOX and oxygen in relatively high concentrations. This method includes contacting a given exhaust gas containing NOX with ammonia at a temperature in the range of from 200C to 400C in the presence of a catalyst and permitting the NOX to react with the ammonia thereby effect-ing conversion of the NOX into N2. The reactions involved in this method are represented by the following formulae:
6NO + 4NH ~ 5N + 6H 0 6NO2 + ~NH3 ~ 7N + 12H 0 For use in the treatments by the contact reduction method, there have been developed and suggested various kinds of synthetic catalysts including platinum-based catalysts, iron-based catalysts, copper-based catalysts, and manganese dioxide-based catalys~s. Of these catalysts, those other than platinum-based catalysts and manganese dioxide-based catalysts are generally deficient in activity at low temperatures below the level of 200C. Platinum-based catalysts, however, have the disadvantage that, with the progress of the reduction, they . have their activity gradually degraded owing to poisoning caused by sulfur oxides (hereinafter referred to as SOx) present in the exhaust gas under treatment and, moreover, the range of ~()91899 temperature at which the~ exhibit high activity is narxow.
Worse still, platinum-based catalysts are expensive.
On the other hand, known manganese dioxide~based catalysts (such as disclosed, for example, in Japanese Patent Laid-Open Publication No. 17368/1975~ are very dense in structure and therefore have only small pore at the surface thereof, so that if used in the form of very small-sized particles, they exhibit fair catalytic activity at low tem-peratures of not more than 200C, but are not really satisfac-tory in activity. Furthermore, the catalytic activity decreasesconsiderably with an increase of the particle size~ Thus, it is difficult to maintain a high rate of NOx-removal when an NOx-containing exhaust gas is treated at a temperature of not more than 200C by the methods using these known catalysts described above.
It is, therefore, an object of the present invention to provide a method for the removal o NOX from NOx-containing exhaust gases, in which an effective reduction of NOX with ammonia can be ensured even at low reaction temperatures of not more than 200C.
As a result of an extensive study, it has been found that, when NOX is reduced with ammonia at various temperatures using, as a catalyst, a manganese oxide product which is obtained by heating manganese carbonate at a temperature of - from 200 to 500C in an atmosphere of a gas containing a pre-determined amount of oxygen, a high rate of NOx-removal can be maintained even at a temperature of not more than 200C.
Thus, according to the present invention, there is provided in a method for removing nitrogen oxides from an exhaust gas by contacting the exhaust gas with ammonia, the improvement comprising: contacting said exhaust gas with alnmoni.~ in the presence of a catal~st com~xising a manganese oxide pro~l~ct which is obtained by heating manganese carbonate at a temperature of from 2ao to 500C in an atmosphere of a gas containing not less than 1% by volume of oxygen.
The substance used as a catalyst in the present invention is a manganese oxide product of a specific type.
The manganese oxide product may be obtained by heating manganese carbonate (for example, in the form of a powder) at a temperature of from 200 to 500C in an atmosphere of a gas which contains not less than 1% by volume, preferably 10% by volume, of oxygen. In this case, the manganese carbonate powder is preferably heated until no carbon dioxide is sub-stantially yenerated from the carbonate. Then, the resultant manganese oxide product may be shaped into a suitable form by a usual manner. Alternatively, a suitable binder such as alumina sol or silica gel may be added to the manganese car-bonate powder to obtain a mixture which is then shaped into a desired form and tXermally treated under such conditions as indicated above to produce the manganese oxide product used in the present invention. Alternatively, the manganese oxide product used in the present invention may be produced as follows:
a manganese compound such as manganese nitrate, manganese sulfate or the like is first supported on a suitable porous carrier such as alumina, silica or the like (for example, by immersing the porous carrier in an aqueous solution of the manganese compound), and then, a carbonate such as sodium carbonate, ammonium carbonate or ammonium bicarbonate is added - to the carrier thus conYerting the manganese compound supported on the carrier into manganese carbonate, followed by thermally treating the product as described above.
The thermal treatment is conducted at a temperature of lQ91899 from 20Q to 50~C in an atmosphere of a gas containing not less than 1~ by volume of oxygen~ If the oxygen content in thle gas is less than 1% by volume, the oxidation will become un~3atisfactory, making it difficult to produce an active catalyst. Examples of the gases suitable for the thermal treatment are a com~ustion exhaust gas (which is preferably free of Sx because the final ca~alyst will be poisoned by means of Sx if contained in the gas) obtained by the combus-tion of a liquefied natural gas; air; pure oxygen; an oxygen-containing steam; and an oxygen-containing inert gas (such as - a mixed gas of nitrogen and oxygen). Of these, the combustion exhaust gas or air is preferred from the viewpoint of economy.
Preferably, the thermal treatment is conducted at a temperature ~ of from 250 to 350C for a time period of from 2 to 24 hours.
; In other words, when the manganese oxide product is expressed by ~nOx, the treatment i~ preferably effected until a product corresponding to x ~ 1.5, preferably x ~ 1.7, is obtained. It will be noted that the manganese oxide product is considered to be a mixture of MnO, MnO2, Un203 and Mn3O4 and thus the atomic ratio of Mn to O is not generally an integer. If the tempera-ture of the thermal treatment is below 200C, the decomposition or oxidation of manganese carbonate will not proceed satis-factorily. In contrast, when the temperature is above 500C, manganese oxides of lower activity are produced in increased amounts and the final catalyst will be poor in activity.
The manganese oxide product thus obtained is very porous and has a specific surface area above 80m /g. In addition, the product has relatively large-sized pores with radii of, for example, above 40 A and a pore capacity of above 0.2 mQ/g. As will be understood from the above, the manganese oxide product used in the present invention has not only a ' 1(~91899 great specific surface area~ but also relatively large-sized pores, so that since the product allows diffusion of a gas belng treated into the insidè thereof, a wider surface area of the product is effectively used, ensur~ng a higher rate of NOx-removal. Since the manganese oxide product has both fine and relatively large pores, it can be used as a molding - of a larger size than in the case of known catalysts for reducing NOX. In general, known catalysts are used in forms having sizes of about 1 to 3 mm. On the other hand, the catalyst used in the present invention ensures a high rate of NOx-removal even when used as a molding having a size above 4 mm. When shaped into cylindrical form, for example, having a diameter of 6 mm and a length of about 10 mm, the catalyst ensures a high rate of NOx-removal of above 9~.
~s will be seen from the foregoing, the manganese oxide product obtained by thermally treating manganese car-bonate in an atmosphere containing oxygen is usable as a catalyst for the reduction of NOX even whe~ shaped into a large-; sized form. This manganese oxide product is effective for treating a large amount of an exhaust gas containing several hundred ppm of NOX. This will become clear by comparison with manganese oxides obtained by other methods as will be seen in Comparative Example 1 appearing hereinafter. For example, a catalyst which is obtained by finely powdering an electrolytic ::
manganese oxide to a size below 10 ~ and shaping the resultant powder similarly to the case of the catalyst of the present ` invention is generally low in catalytic act:ivity and the rate of NOx-removal is considerably reduced when the catalyst is of large size~
The present invention will be particularly illustrated ; by way of the following Examples.
1~91899 ~xample 1:
An aq~ous ammoniu~ carbonate solution was added to an aqueous manganese sulfate solution to prepare a manganese carbonate powder (having a particle size of 1 to 1.5 ~). The powder was thermally treated in a propane-combustion gas tcomposed of 9.8% by volume of 2~ 6.1~ by volume of CO2, 8~2~ by volume of H20, and a balance of N2) at 300C for 12 hours. The resultant product was a powder having a composition of Mnl 83 To 100 parts by weight of the powder was added 5 parts by weight of colloidal alumina as A1203, to which was added water for kneading. The mixture was then extrusion molded and dried at 150C for 5 hours to obtain a catalyst in cylindrical form having a diameter of 5 mm and a length of about 10 mm. The catalyst had a specific surface area of 142 m /g. The measurement of the pore distribution by a pre~suxized mercury method revealed that the catalyst had pores which were broadly classified into the three radius O O O
ranges of 40 - 200 A, 200 - 1000 A and above 1000 A and that the pore capacities in these ranges were, respectively, 0.18 mQ/g, 0.03 mQ/g and 0.25 mQ/g. Thus, the catalyst was very porous.
When an N2 gas containing 500 ppm of NO, 500 ppm of NH3, 4% by volume f 2 and 10% by volume of H20 was passed through the catalyst at a space velocity of 7,500 Hr 1, the removal rates for NO were found to be 98%, 99%, above 99~, above 99~ and above 99% at reaction ~emperatures of 120C, 130C, 140C, 150C and 200C, respectively.
Comparative Example 1:
~ Electrolytic manganese oxide was powdered to a size - below 10 ~, and then molded and dried in the same manner as . .
in Example 1 thereby obtaining two catalysts, i.e., a molded catalyst (catalyst A~ having a diameter of 3 mm and a length 1(~91899 of S mm and a molded catalyst (catalyst B) having a diameter of 5 mm and a length of 10 mm~ As a result of the measurement of the pore distribution by the pressurized mercury method, it was found that Catalyst A had pores in radius ranges of 40 -O O O
200 A, ~00 1000 A and above 1000 A and that the capacitiesof the pores in the above ranges were 0.06 mQ/g, 0.04 mQ/g and 0.03 mQ/g, respectively. Catalyst A had a specific surface -~
area of 58 m2~g. Similarly, Catalyst B was found to have pores in radius ranges of 40 - 200 A, 200 - 1000 A and above 1000 A
and capacities of the pores in the above ranges were 0.06 mQ/g, 0.05 mQ/g and 0.02 mQ/g, respectively. The specific surface area of Catalyst B was 58 m /g.
Catalysts A and B were used for removing NO under the same conditions as in Example 1 with the following results.
Reaction Temperature 120C 130C 140C 150C 200C
Catalyst A 85 % 89 % 93 % 95 % 97 %
Catalyst B 81 % 85 % 89 % 92 % 94 %
Example 2:
3 parts by weight of colloidal silica as SiO2 was added to 100 parts by weight of manganese carbonate powder of the same type as used in Example 1, to which was added water for kneading. The mixture was then extrusion molded and dried at 120C to obtain cylindrical moldings each having a diameter of 7 mm and a length of about 13 mm. The molding~
were thermally treated at 350C for 7 hours while passing air sufficiently to give a catalyst. The catalyst had a mangane~e oxide composition of MnOl 80 and a specific surface area of 158 m2/g. The measurement of a pore distribution by a pressurized mercury method revealed that the catalyst had 30 pores in radius ranges of 40 - 200 A, 200 - 1000 ~ and above ooo A and that capacities of the pores in such ranges were 0.18 mQ/g, 0.02 mQ/g and 0.27 mQ/g, respectively.
When the catalyst thus obtained was used for treatment l~alsss by passing therethrough an N2 gas containing 500 ppm of NO, 500 ppm of N~13, 3 ~ by volume of 2 and 15 % by volume of H2O
at a space velocity of 10,000 hr 1, the rates of removal of NO at reaction temperatures of 130C,150~C, 200C and 250C were found to be 95 %, 98 %, 99 % and 98 %, respectively.
Example 3:
Silica-alumina (product of Mizusawa Chem. Ind., Co., available under a commercial name of Neobead~D) suitable as carrier in the form of spheres of a diameter of about ~ mm was immersed in an aqueous manganese nitrate solution containing about 5 ~ of manganese for 3 hours thereby permitting manganese nitrate to be carried on the carrier. The carrier was then removed from the solution and introduced into an aqueous ammonium carbonate to convert the mangane~e nitrate on the carrier into manganese carbonate. The carbonate-bearing carrier was dried at 120C and thermally treated at 300C for 5 hours while passing air sufficiently to obtain a catalyst.
An N2 gas containing 200 ppm of NO, 200 ppm of NH3, 4% by volume of 2 and 10 % by volume of H2O was passed through the catalyst at a space velocity of 5,000 Hr 1. As a result, it was found that the rate of removal of NO reached 98 %, thus the catalyst being very high in activity.
Comparative Example 2:
A silica-alumina carrier of the same type as used in Example 3 was applied with manganese nitrate similarly to the case of Example 3 and then dried at 120C, followed by thermally treating it at 300C for 5 hours while passing air sufficiently, thereby obtaining a catalyst. When the thus o~tained catalyst was used for removing NO under the same procedure as in Example 3, the rate of removal of NO was found to be 46 ~.
tr~/e~rk
Various methods have been heretofore suggested for the removal of NOX from NOx-containing exhaust gases such as those issuing from combustion sources. Among them, a method which resorts to contact reduction using ammonia as the reducing agent is considered to be highly promising because it is amply effective even when it is used for the treatment of exhaust gases of the type containing NOX and oxygen in relatively high concentrations. This method includes contacting a given exhaust gas containing NOX with ammonia at a temperature in the range of from 200C to 400C in the presence of a catalyst and permitting the NOX to react with the ammonia thereby effect-ing conversion of the NOX into N2. The reactions involved in this method are represented by the following formulae:
6NO + 4NH ~ 5N + 6H 0 6NO2 + ~NH3 ~ 7N + 12H 0 For use in the treatments by the contact reduction method, there have been developed and suggested various kinds of synthetic catalysts including platinum-based catalysts, iron-based catalysts, copper-based catalysts, and manganese dioxide-based catalys~s. Of these catalysts, those other than platinum-based catalysts and manganese dioxide-based catalysts are generally deficient in activity at low temperatures below the level of 200C. Platinum-based catalysts, however, have the disadvantage that, with the progress of the reduction, they . have their activity gradually degraded owing to poisoning caused by sulfur oxides (hereinafter referred to as SOx) present in the exhaust gas under treatment and, moreover, the range of ~()91899 temperature at which the~ exhibit high activity is narxow.
Worse still, platinum-based catalysts are expensive.
On the other hand, known manganese dioxide~based catalysts (such as disclosed, for example, in Japanese Patent Laid-Open Publication No. 17368/1975~ are very dense in structure and therefore have only small pore at the surface thereof, so that if used in the form of very small-sized particles, they exhibit fair catalytic activity at low tem-peratures of not more than 200C, but are not really satisfac-tory in activity. Furthermore, the catalytic activity decreasesconsiderably with an increase of the particle size~ Thus, it is difficult to maintain a high rate of NOx-removal when an NOx-containing exhaust gas is treated at a temperature of not more than 200C by the methods using these known catalysts described above.
It is, therefore, an object of the present invention to provide a method for the removal o NOX from NOx-containing exhaust gases, in which an effective reduction of NOX with ammonia can be ensured even at low reaction temperatures of not more than 200C.
As a result of an extensive study, it has been found that, when NOX is reduced with ammonia at various temperatures using, as a catalyst, a manganese oxide product which is obtained by heating manganese carbonate at a temperature of - from 200 to 500C in an atmosphere of a gas containing a pre-determined amount of oxygen, a high rate of NOx-removal can be maintained even at a temperature of not more than 200C.
Thus, according to the present invention, there is provided in a method for removing nitrogen oxides from an exhaust gas by contacting the exhaust gas with ammonia, the improvement comprising: contacting said exhaust gas with alnmoni.~ in the presence of a catal~st com~xising a manganese oxide pro~l~ct which is obtained by heating manganese carbonate at a temperature of from 2ao to 500C in an atmosphere of a gas containing not less than 1% by volume of oxygen.
The substance used as a catalyst in the present invention is a manganese oxide product of a specific type.
The manganese oxide product may be obtained by heating manganese carbonate (for example, in the form of a powder) at a temperature of from 200 to 500C in an atmosphere of a gas which contains not less than 1% by volume, preferably 10% by volume, of oxygen. In this case, the manganese carbonate powder is preferably heated until no carbon dioxide is sub-stantially yenerated from the carbonate. Then, the resultant manganese oxide product may be shaped into a suitable form by a usual manner. Alternatively, a suitable binder such as alumina sol or silica gel may be added to the manganese car-bonate powder to obtain a mixture which is then shaped into a desired form and tXermally treated under such conditions as indicated above to produce the manganese oxide product used in the present invention. Alternatively, the manganese oxide product used in the present invention may be produced as follows:
a manganese compound such as manganese nitrate, manganese sulfate or the like is first supported on a suitable porous carrier such as alumina, silica or the like (for example, by immersing the porous carrier in an aqueous solution of the manganese compound), and then, a carbonate such as sodium carbonate, ammonium carbonate or ammonium bicarbonate is added - to the carrier thus conYerting the manganese compound supported on the carrier into manganese carbonate, followed by thermally treating the product as described above.
The thermal treatment is conducted at a temperature of lQ91899 from 20Q to 50~C in an atmosphere of a gas containing not less than 1~ by volume of oxygen~ If the oxygen content in thle gas is less than 1% by volume, the oxidation will become un~3atisfactory, making it difficult to produce an active catalyst. Examples of the gases suitable for the thermal treatment are a com~ustion exhaust gas (which is preferably free of Sx because the final ca~alyst will be poisoned by means of Sx if contained in the gas) obtained by the combus-tion of a liquefied natural gas; air; pure oxygen; an oxygen-containing steam; and an oxygen-containing inert gas (such as - a mixed gas of nitrogen and oxygen). Of these, the combustion exhaust gas or air is preferred from the viewpoint of economy.
Preferably, the thermal treatment is conducted at a temperature ~ of from 250 to 350C for a time period of from 2 to 24 hours.
; In other words, when the manganese oxide product is expressed by ~nOx, the treatment i~ preferably effected until a product corresponding to x ~ 1.5, preferably x ~ 1.7, is obtained. It will be noted that the manganese oxide product is considered to be a mixture of MnO, MnO2, Un203 and Mn3O4 and thus the atomic ratio of Mn to O is not generally an integer. If the tempera-ture of the thermal treatment is below 200C, the decomposition or oxidation of manganese carbonate will not proceed satis-factorily. In contrast, when the temperature is above 500C, manganese oxides of lower activity are produced in increased amounts and the final catalyst will be poor in activity.
The manganese oxide product thus obtained is very porous and has a specific surface area above 80m /g. In addition, the product has relatively large-sized pores with radii of, for example, above 40 A and a pore capacity of above 0.2 mQ/g. As will be understood from the above, the manganese oxide product used in the present invention has not only a ' 1(~91899 great specific surface area~ but also relatively large-sized pores, so that since the product allows diffusion of a gas belng treated into the insidè thereof, a wider surface area of the product is effectively used, ensur~ng a higher rate of NOx-removal. Since the manganese oxide product has both fine and relatively large pores, it can be used as a molding - of a larger size than in the case of known catalysts for reducing NOX. In general, known catalysts are used in forms having sizes of about 1 to 3 mm. On the other hand, the catalyst used in the present invention ensures a high rate of NOx-removal even when used as a molding having a size above 4 mm. When shaped into cylindrical form, for example, having a diameter of 6 mm and a length of about 10 mm, the catalyst ensures a high rate of NOx-removal of above 9~.
~s will be seen from the foregoing, the manganese oxide product obtained by thermally treating manganese car-bonate in an atmosphere containing oxygen is usable as a catalyst for the reduction of NOX even whe~ shaped into a large-; sized form. This manganese oxide product is effective for treating a large amount of an exhaust gas containing several hundred ppm of NOX. This will become clear by comparison with manganese oxides obtained by other methods as will be seen in Comparative Example 1 appearing hereinafter. For example, a catalyst which is obtained by finely powdering an electrolytic ::
manganese oxide to a size below 10 ~ and shaping the resultant powder similarly to the case of the catalyst of the present ` invention is generally low in catalytic act:ivity and the rate of NOx-removal is considerably reduced when the catalyst is of large size~
The present invention will be particularly illustrated ; by way of the following Examples.
1~91899 ~xample 1:
An aq~ous ammoniu~ carbonate solution was added to an aqueous manganese sulfate solution to prepare a manganese carbonate powder (having a particle size of 1 to 1.5 ~). The powder was thermally treated in a propane-combustion gas tcomposed of 9.8% by volume of 2~ 6.1~ by volume of CO2, 8~2~ by volume of H20, and a balance of N2) at 300C for 12 hours. The resultant product was a powder having a composition of Mnl 83 To 100 parts by weight of the powder was added 5 parts by weight of colloidal alumina as A1203, to which was added water for kneading. The mixture was then extrusion molded and dried at 150C for 5 hours to obtain a catalyst in cylindrical form having a diameter of 5 mm and a length of about 10 mm. The catalyst had a specific surface area of 142 m /g. The measurement of the pore distribution by a pre~suxized mercury method revealed that the catalyst had pores which were broadly classified into the three radius O O O
ranges of 40 - 200 A, 200 - 1000 A and above 1000 A and that the pore capacities in these ranges were, respectively, 0.18 mQ/g, 0.03 mQ/g and 0.25 mQ/g. Thus, the catalyst was very porous.
When an N2 gas containing 500 ppm of NO, 500 ppm of NH3, 4% by volume f 2 and 10% by volume of H20 was passed through the catalyst at a space velocity of 7,500 Hr 1, the removal rates for NO were found to be 98%, 99%, above 99~, above 99~ and above 99% at reaction ~emperatures of 120C, 130C, 140C, 150C and 200C, respectively.
Comparative Example 1:
~ Electrolytic manganese oxide was powdered to a size - below 10 ~, and then molded and dried in the same manner as . .
in Example 1 thereby obtaining two catalysts, i.e., a molded catalyst (catalyst A~ having a diameter of 3 mm and a length 1(~91899 of S mm and a molded catalyst (catalyst B) having a diameter of 5 mm and a length of 10 mm~ As a result of the measurement of the pore distribution by the pressurized mercury method, it was found that Catalyst A had pores in radius ranges of 40 -O O O
200 A, ~00 1000 A and above 1000 A and that the capacitiesof the pores in the above ranges were 0.06 mQ/g, 0.04 mQ/g and 0.03 mQ/g, respectively. Catalyst A had a specific surface -~
area of 58 m2~g. Similarly, Catalyst B was found to have pores in radius ranges of 40 - 200 A, 200 - 1000 A and above 1000 A
and capacities of the pores in the above ranges were 0.06 mQ/g, 0.05 mQ/g and 0.02 mQ/g, respectively. The specific surface area of Catalyst B was 58 m /g.
Catalysts A and B were used for removing NO under the same conditions as in Example 1 with the following results.
Reaction Temperature 120C 130C 140C 150C 200C
Catalyst A 85 % 89 % 93 % 95 % 97 %
Catalyst B 81 % 85 % 89 % 92 % 94 %
Example 2:
3 parts by weight of colloidal silica as SiO2 was added to 100 parts by weight of manganese carbonate powder of the same type as used in Example 1, to which was added water for kneading. The mixture was then extrusion molded and dried at 120C to obtain cylindrical moldings each having a diameter of 7 mm and a length of about 13 mm. The molding~
were thermally treated at 350C for 7 hours while passing air sufficiently to give a catalyst. The catalyst had a mangane~e oxide composition of MnOl 80 and a specific surface area of 158 m2/g. The measurement of a pore distribution by a pressurized mercury method revealed that the catalyst had 30 pores in radius ranges of 40 - 200 A, 200 - 1000 ~ and above ooo A and that capacities of the pores in such ranges were 0.18 mQ/g, 0.02 mQ/g and 0.27 mQ/g, respectively.
When the catalyst thus obtained was used for treatment l~alsss by passing therethrough an N2 gas containing 500 ppm of NO, 500 ppm of N~13, 3 ~ by volume of 2 and 15 % by volume of H2O
at a space velocity of 10,000 hr 1, the rates of removal of NO at reaction temperatures of 130C,150~C, 200C and 250C were found to be 95 %, 98 %, 99 % and 98 %, respectively.
Example 3:
Silica-alumina (product of Mizusawa Chem. Ind., Co., available under a commercial name of Neobead~D) suitable as carrier in the form of spheres of a diameter of about ~ mm was immersed in an aqueous manganese nitrate solution containing about 5 ~ of manganese for 3 hours thereby permitting manganese nitrate to be carried on the carrier. The carrier was then removed from the solution and introduced into an aqueous ammonium carbonate to convert the mangane~e nitrate on the carrier into manganese carbonate. The carbonate-bearing carrier was dried at 120C and thermally treated at 300C for 5 hours while passing air sufficiently to obtain a catalyst.
An N2 gas containing 200 ppm of NO, 200 ppm of NH3, 4% by volume of 2 and 10 % by volume of H2O was passed through the catalyst at a space velocity of 5,000 Hr 1. As a result, it was found that the rate of removal of NO reached 98 %, thus the catalyst being very high in activity.
Comparative Example 2:
A silica-alumina carrier of the same type as used in Example 3 was applied with manganese nitrate similarly to the case of Example 3 and then dried at 120C, followed by thermally treating it at 300C for 5 hours while passing air sufficiently, thereby obtaining a catalyst. When the thus o~tained catalyst was used for removing NO under the same procedure as in Example 3, the rate of removal of NO was found to be 46 ~.
tr~/e~rk
Claims (2)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a method for removing nitrogen oxides from an exhaust gas by contacting the exhaust gas with ammonia, the improvement comprising:
contacting said exhaust gas with ammonia in the presence of a catalyst comprising a manganese oxide product which is obtained by heating manganese carbonate at a tem-perature of from 200 to 500°C in an atmosphere of a gas containing not less than 1 % by volume of oxygen.
contacting said exhaust gas with ammonia in the presence of a catalyst comprising a manganese oxide product which is obtained by heating manganese carbonate at a tem-perature of from 200 to 500°C in an atmosphere of a gas containing not less than 1 % by volume of oxygen.
2. The method of claim 1, wherein said exhaust gas is contacted with ammonia and the catalyst at a temperature of not more than 200°C.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP52067584A JPS5920383B2 (en) | 1977-06-08 | 1977-06-08 | NOx reduction catalyst with high activity at low temperatures |
| JP67584/1977 | 1977-06-08 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1091899A true CA1091899A (en) | 1980-12-23 |
Family
ID=13349104
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA304,764A Expired CA1091899A (en) | 1977-06-08 | 1978-06-05 | Method for removal of nitrogen oxides from nitrogen oxides-containing exhaust gas |
Country Status (7)
| Country | Link |
|---|---|
| JP (1) | JPS5920383B2 (en) |
| CA (1) | CA1091899A (en) |
| DE (1) | DE2824246A1 (en) |
| FR (1) | FR2393602A1 (en) |
| GB (1) | GB1599079A (en) |
| NL (1) | NL7806130A (en) |
| PL (1) | PL207401A1 (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5790159A (en) * | 1980-11-27 | 1982-06-04 | Toa Medical Electronics Co Ltd | Blood analyzer |
| DE3634553A1 (en) * | 1986-10-10 | 1988-04-21 | Didier Werke Ag | USE OF MANGANE NUMBERS OR MANGANEOUS DEEP SEA ORES IN CATALYSTS TO REDUCE NITROGEN OXIDES IN EXHAUST GAS |
| EP0596927B1 (en) * | 1991-07-29 | 1995-08-23 | British Technology Group Ltd | Catalyst and catalytic reduction |
| JPH06509273A (en) * | 1991-07-29 | 1994-10-20 | ビーティージー・インターナショナル・リミテッド | Catalysts and catalytic reduction |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE1253685B (en) * | 1963-01-22 | 1967-11-09 | Degussa | Process for the removal of nitrogen oxides from nitrogen oxide-containing exhaust gases |
| BE789846A (en) * | 1971-10-08 | 1973-02-01 | Du Pont | PROCESS FOR PURIFYING GASEOUS CURRENTS CONTAINING SULFUR IMPURITIES |
| US4003854A (en) * | 1974-06-03 | 1977-01-18 | Gennady Alexeevich Skvortsov | Catalyst of supported vanadium oxide and manganese oxide and method of producing same |
-
1977
- 1977-06-08 JP JP52067584A patent/JPS5920383B2/en not_active Expired
-
1978
- 1978-05-31 GB GB2518578A patent/GB1599079A/en not_active Expired
- 1978-06-02 DE DE19782824246 patent/DE2824246A1/en active Pending
- 1978-06-05 CA CA304,764A patent/CA1091899A/en not_active Expired
- 1978-06-06 NL NL7806130A patent/NL7806130A/en not_active Application Discontinuation
- 1978-06-06 PL PL20740178A patent/PL207401A1/en unknown
- 1978-06-07 FR FR787816995A patent/FR2393602A1/en not_active Withdrawn
Also Published As
| Publication number | Publication date |
|---|---|
| GB1599079A (en) | 1981-09-30 |
| DE2824246A1 (en) | 1978-12-14 |
| NL7806130A (en) | 1978-12-12 |
| JPS5920383B2 (en) | 1984-05-12 |
| FR2393602A1 (en) | 1979-01-05 |
| JPS542289A (en) | 1979-01-09 |
| PL207401A1 (en) | 1979-03-12 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US7005116B2 (en) | Process for reducing nitrogen oxides | |
| US10661225B2 (en) | Copper supported catalyst comprising a Ca-deficient hydroxyapatite for waste gas NOx removal | |
| US4640908A (en) | Catalyst for the oxidation of hydrogen sulfide and process for the preparation of the catalyst | |
| EP0210681A1 (en) | Bivalent metal-aluminate catalyst | |
| US5068217A (en) | Carrier catalysts for oxidizing carbon monoxide and process for their production | |
| US4062810A (en) | Carrier-supported catalyst | |
| US3993731A (en) | Selective removal of nitrogen oxides from waste gas | |
| CA1091899A (en) | Method for removal of nitrogen oxides from nitrogen oxides-containing exhaust gas | |
| CN110215923B (en) | Catalyst for reducing nitrogen oxide and nitrogen oxide reduction system using same | |
| US3880982A (en) | Process for removing nitrogen oxides from exhaust gases | |
| WO1994021373A1 (en) | Nitrogen oxide decomposing catalyst and denitration method using the same | |
| US3981971A (en) | Process for reducing nitrogen oxides | |
| US3867309A (en) | Catalyst composition for removing noxious components from a gaseous stream | |
| JP4512691B2 (en) | Catalyst for selective reduction of nitrogen oxides by carbon monoxide and its preparation | |
| US4199555A (en) | Catalyst for reducing nitrogen oxides | |
| EP0262754A1 (en) | Selective catalytic reduction catalysts | |
| KR101251499B1 (en) | Zeolite catalyst for removing nitrogen oxides, method for preparing the same, and removing method of nitrogen oxides using the same | |
| Nozaki et al. | Low temperature activity of the copper oxide catalyst supported on activated carbon for reduction of nitric oxide with ammonia | |
| US6077493A (en) | Method for removing nitrogen oxides | |
| SU421166A3 (en) | ||
| CA1050522A (en) | Carrier-supported catalyst | |
| CA1065123A (en) | Process for the oxidation of carbon monoxide and hydrocarbons | |
| JP2001129406A (en) | Low temperature denitration catalyst | |
| CN108435237B (en) | Middle and low temperature NH3-SCR catalyst, preparation method and application thereof | |
| CA1045342A (en) | Process for removing hydrocarbons |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |