CN1209191C - Rarefied combustion tail gas nitrogen oxide purification catalyst and its purification - Google Patents
Rarefied combustion tail gas nitrogen oxide purification catalyst and its purification Download PDFInfo
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- CN1209191C CN1209191C CN 02100669 CN02100669A CN1209191C CN 1209191 C CN1209191 C CN 1209191C CN 02100669 CN02100669 CN 02100669 CN 02100669 A CN02100669 A CN 02100669A CN 1209191 C CN1209191 C CN 1209191C
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Abstract
The present invention relates to a catalyst which is used for purifying combustion tail gas and can simultaneously and selectively reduce and remove nitrous oxides in thin combustion tail gas and remove incompletely combusted hydrocarbons and carbon monoxide in an oxidation method. The catalyst is composed of 0.1% to 17% of (metal element weight equivalent value) silver components which are supported on porosity inorganic oxide carriers; the silver components can be silver and silver oxides and in any inorganic salt form without changed function. The present invention is suitable for being used for tail gas sources comprising maneuver or fixed combustion devices, such as diesel engines, thin combustion gasoline engines, natural gas engines, etc. The present invention has the purification method that the made catalyst is put in tail gas pipelines; organics is added in the upper stream of the catalyst and is used as reducer to be mixed with tail gas; mixed gas touches the catalyst at temperature of 150 DEG C to 600 DEG C, thereby, nitrous oxides are reduced to nitrogen gas, and redundant reducer is oxidized into carbon dioxide and water.
Description
Technical field
The present invention is used for the nitrogen oxide of purification of exhaust gases of internal combustion engines, particularly nitrogen oxides reduction in oxidizing atmosphere.These are different with the three-way catalyst that generally is used at present to purify gasoline engine tail gas.The use of three-way catalyst is to be based upon the ratio of strict control petrol engine air and fuel near theoretical air-fuel ratio (stoichiometric proportion), and remaining oxygen content is seldom in the tail gas at this moment.Its mechanism of action is to make carbon monoxide and hydrocarbon as reducing agent nitrogen oxides reduction (NO by catalyst
X) become nitrogen, and the remaining carbon monoxide of catalytic oxidation becomes carbon dioxide and water with hydrocarbon.Nearly all new product gasoline car (not containing lean-burn gasoline motor car) all is equipped with three-way catalyst at present, and what form sharp contrast therewith is that diesel vehicle is not taked similar control techniques basically.The practical air-fuel ratio of diesel engine is much larger than its chemically correct fuel, belong to lean combustion engine, in the tail gas content of carbon monoxide and hydrocarbon seldom, but oxygen content is tens times of gasoline engine, can reach 15% volume ratio, clearly three-way catalyst is not suitable for the operating mode of diesel engine.Diesel engine becomes a main flow direction of following motor vehicle development with its good dynamic property and economy, diesel generation and electricity-Re one residential quarter facility is also more prevalent, yet its discharged nitrous oxides pollution that does not add processing is restricting development of diesel.
Technical background
Up to the present, for the Rarefied combustion tail gas catalysis and purification technology of nitrogen oxide in diesel engine and the gasoline engine tail gas particularly, the catalyst of studying can be divided into zeolite, load type metal or metal oxide and the carried noble metal three major types of ion-exchange, and reducing agent mainly contains Ammonia, low-carbon alkene, alkane, alcohol, ketone and ether etc.At present, the subject matter that catalyst in the research exists is, zeolite catalyst is to steam and sulfur dioxide poisoning, and hydrothermal stability is poor; The noble metal catalyst poor selectivity, and the active temperature scope is narrow, and most of reducing agent loses the ability of nitrogen oxides reduction at the high-temperature region oxidizing fire; Load type metal or metal oxide catalyst low temperature active when making reducing agent with hydrocarbons such as low-carbon alkene, alkane is still waiting to improve.
Summary of the invention
The purpose of this invention is to provide a kind of particularly diesel engine vent gas oxynitrides (NO of combustion tail gas that is used under the excess oxygen
X) the catalyst and the purification method of catalytic purification.
The present invention is fully taking into account on the basis of previous studies, is carrying out the result of big quantity research.The catalyst that is provided is oxygen content (for example 10% volume) oxygen content when burning far above stoichiometric proportion in tail gas, and still nitrogen oxide is had very high reducing activity under the water vapor conditions of 10% volume, particularly than the activity under the low exhaust gas temperature.In addition, sulfur dioxide in the tail gas and phosphorus composition there is very strong anti-poisoning capability.
This catalyst is carried on a shoulder pole to be held on the porous inorganic oxide carrier by the silver components of 0.1-17% (metallic element weight scaled value) and is constituted.When silver components during less than 0.1% (metallic element weight scaled value), the activity of such catalysts particularly conversion ratio of cryogenic nitrogen oxide can reduce.And silver components is during greater than 17% (metallic element weight scaled value), hydrocarbon or (with) oxygen-bearing organic matter can preferential combustion and reduce the conversion ratio of nitrogen oxide.The indication silver components can be the oxide of silver and silver and the form of any inorganic salts and do not change its effect.The porous inorganic oxide carrier of catalyst can be alundum (Al, silica, zeolite, sepiolite, titanium dioxide, zirconium dioxide, zinc oxide, magnesia, tin ash one or more hopcalites or its composite oxides wherein.Porous inorganic oxide carrier is Powdered or moulding coccoid.Aforesaid porous inorganic oxide carrier should have 10 meters squared per gram or bigger specific area, is preferably 30 meters squared per gram or bigger specific area.
According to the present invention, the component of silver can be by using silver-colored soluble compound water solution with well-known infusion process, and the precipitation method or sol-gel process are deposited on the aforesaid porous inorganic oxide carrier.During such as the use infusion process, selected porous inorganic oxide carrier can be soaked in the aqueous solution of silver nitrate, stir 1-24 hour, 80-150 ℃ of drying, interim ground is warming up to 700 ℃ from 100 ℃ in air or nitrogen or hydrogen or vacuum.The granular size of silver components can be controlled by adjusting factors such as temperature, time and atmosphere.According to the present invention, silver components has the particle diameter of average 5-1000 nanometer on porous inorganic oxide carrier, is preferably average 20-300 nanometer, more preferably the 10-50 nanometer.With silver or silver-colored oxide diameter sizes is example, during less than 5 nanometers, aforesaid hydrocarbon or (with) oxygen-bearing organic matter can preferential combustion and reduce the conversion ratio of nitrogen oxide.And silver or silver-colored oxide diameter sizes be during greater than 1000 nanometers, and the activity of such catalysts particularly conversion ratio of nitrogen oxide can reduce.
Aforesaid catalyst, preferably be coated on the wall surface of circulation passage of pottery or metal honeycomb with the form of coating, this one-piece type catalyst has the passage of the parallel circulation of many tail gas, and vapour lock is very little, can be applicable to handle diesel engine vent gas or gasoline engine tail gas.The hole density of preferred honeycomb is the 100-400/ square inch.Catalyst is coated on these carrier structures with the concentration of 30-300 gram/every liter of carrier structure.According to different needs, other structures also can be as the structural carrier of catalyst as metallic sieve or open-celled foams.Also catalyst can be made spherical or tabular use.
Be suitable for the tail gas source and comprise Diesel engine, fixing or motor-driven burner such as lean-burn gasoline engine and natural gas engine.It is characterized in that, when the content of oxygen in tail gas catalyst when equivalent burns still effective, but when imperfect combustion hydrocarbon and carbon monoxide content are not enough to be used for nitrogen oxides reduction under the above-mentioned lean burn situation, need to add hydrocarbon/or oxygen-bearing organic matter/or the mixture of hydrocarbon and oxygen-bearing organic matter as reducing agent with nitrogen oxides reduction.The reducing agent of indication can be that second is rare, acetylene, third rare, propane, gasoline, heptane, diesel oil, hexadecane, acetaldehyde, acetone, contain the above alcohols of two carbon atoms, and composition thereof, be preferably oxygen-bearing organic matter.The normality of these reducing agents both can be a gaseous state, also can be liquid.The requirement of reducing agent can be 0.2-5 a times of nitrogen oxide in the aforementioned tail gas (in nitric oxide) weight, is preferably 0.3-4 doubly.
Oxygen content is higher than that the purification of nitrogen oxides method is in the combustion tail gas of stoichiometric proportion when burning oxygen content, aforesaid catalyst can be placed aforesaid exhaust pipe way, add in the upstream of catalyst hydrocarbon/or oxygen-bearing organic matter/or the mixture and the tail gas of hydrocarbon and oxygen-bearing organic matter mix, gaseous mixture is contacted with catalyst at 150-600 ℃, thus make nitrogen oxide and hydrocarbon/or oxygen-bearing organic matter/or the mixture reaction of hydrocarbon and oxygen-bearing organic matter be reduced into nitrogen.Preferred exhaust temperature scope is 250-550 ℃.Unnecessary reducing agent is oxidized to carbon dioxide and water under the effect of catalyst.The method of the interpolation of above-mentioned reducing agent (gaseous state or liquid state) can be carried out with the form of spraying the upstream of catalyst in exhaust pipe.Also above-mentioned reducing agent (gaseous state or liquid state) can be injected in the combustion chambers of internal combustion engines, utilize the remaining component of burning to make reducing agent and contact nitrogen oxide in the reduction tail gas with catalyst.The air/fuel ratio that can also adjust internal combustion engine makes and contains more unburned hydrocarbons and oxygen-bearing organic matter in the tail gas, contacts nitrogen oxide in the reduction tail gas with catalyst.Relatively above several method can obtain most economical and effective Rarefied combustion tail gas nitrogen oxide purification method.
Describe the present invention in detail by following embodiment.
Embodiment 1
100 gram γ-alundum (Al powder (particle diameter less than 120 orders, specific area: be not less than 250 meters squared per gram) are soaked in the aqueous solution of silver nitrate, stir 1 hour, after 90 ℃ of dryings, are warming up to 700 ℃ from 100 ℃ in air interimly, keep 3 hours.The silver components load capacity is 2.5% (metallic element weight scaled value), and the granular size of silver and silver oxide can be observed on average in 20 nanometers down by electron microscope.
The catalyst particles that 2.0 grams are made by above method for making is positioned in the tubular reactor, feeds 4 liters/per minute of simulation Rarefied combustion tail gas as shown in table 1, and corresponding air speed (GHSV) is 50,000/ hours.The temperature that enters the simulated exhaust gas of reactor begins to warm to 600 ℃ from 200 ℃, observes nitrogen oxide by the situation of third rare reduction.
Utilize chemiluminescence formula nitrogen oxide (nitric oxide, nitrogen dioxide and total nitrogen oxide) analysis-e/or determining by the nitrous oxides concentration in the simulated exhaust gas behind the catalyst (nitric oxide and nitrogen dioxide sum).The results are shown in Table 3.
Table 1 with third rare be the simulated exhaust gas composition and the reaction condition of reducing agent
Constituent concentration
Nitric oxide 700ppm
Carbon monoxide 90ppm
Sulfur dioxide 80ppm
Oxygen 10% volume ratio
Third rare 1500ppm (3 times of amounts of nitric oxide weight)
Nitrogen balance
Water 10% volume ratio
Air speed (GHSV) 50,000/ hours
Table 2 is with third rare influence that is the simulated exhaust gas temperature of reducing agent to catalyst activity
Exhaust temperature (℃) 200 250 300 350 400 450 500 550 600
Nitrogen oxide
Conversion ratio (%) 0.0 0.0 7.7 12.5 25.8 65.0 82.6 57.5 10.0
As can be seen from Table 2, use aforesaid catalyst can in wider temperature range, remove nitrogen oxide well, with third rare be that average transformation efficiency of the oxides of nitrogen is 57.7% in the scope of 400-550 ℃ of simulated exhaust gas temperature of reducing agent.
Embodiment 2
Prepare catalyst fines by the mode identical with embodiment 1.All change into moisture dispersion then in ball mill, it is 300 grams per liters that this dispersion dilute with water makes solids content.Coating hole density is 400/ square inch cordierite honeycomb structure, this cordierite honeycomb structure is immersed in the aforesaid dispersion, blow out dispersion unnecessary in the passage with compressed air then, the cordierite honeycomb structure of 120 ℃ of this coatings of drying in drying cupboard, repeat this process, make the coating coated weight of the cordierite honeycomb structure that applied reach 420 grams per liters.The cordierite honeycomb structure that applied at last kept 3 hours down at 700 ℃ in air.
The cordierite honeycomb structure catalyst of making is cut into 15 millimeters of diameters, grows 27 millimeters Cylinder, be positioned in the tubular reactor, feed 4 liters/per minute of simulation Rarefied combustion tail gas as shown in table 3, corresponding air speed (GHSV) is 50,000/ hours.The temperature that enters the simulated exhaust gas of reactor begins to warm to 600 ℃, the situation that the observation nitrogen oxide is reduced by ethanol from 200 ℃.
Utilize chemiluminescence formula nitrogen oxide (nitric oxide, nitrogen dioxide and total nitrogen oxide) analysis-e/or determining by the nitrous oxides concentration in the simulated exhaust gas behind the catalyst (nitric oxide and nitrogen dioxide sum).The results are shown in Table 4.
Table 3 is the simulated exhaust gas composition and the reaction condition of reducing agent with ethanol
Constituent concentration
Nitric oxide 700ppm
Carbon monoxide 90ppm
Sulfur dioxide 80ppm
Oxygen 10% volume ratio
3 times of amounts of ethanol nitric oxide weight
(the about 1370ppm in gasification back)
Nitrogen balance
Water 10% volume ratio
Air speed (GHSV) 50,000/ hours
Table 4 is the influence of the simulated exhaust gas temperature of reducing agent to catalyst activity with ethanol
Exhaust temperature (℃) 200 250 300 350 400 450 500 550 600
Nitrogen oxide
Conversion ratio (%) 60.3 93.5 100 100 100 91.7 77.8 59.5 48.1
As can be seen from Table 4, use aforesaid catalyst can remove nitrogen oxide well in very wide temperature range, in the scope of 200-550 ℃ of simulated exhaust gas temperature that with ethanol is reducing agent, average transformation efficiency of the oxides of nitrogen is 85.4%.Amazing especially is that in low temperature 250-450 ℃ scope, average transformation efficiency of the oxides of nitrogen is 97%.Generally the temperature than the stoichiometric proportion combustion tail gas is low to consider the temperature of Rarefied combustion tail gas, and this is a particularly advantageous factor.
As mentioned above, use catalyst provided by the invention and purification of nitrogen oxides method, can the nitrogen oxide in the Rarefied combustion tail gas effectively be purified.Catalyst provided by the invention and purification of nitrogen oxides method can be widely used in Diesel engine, the motor vehicles such as lean-burn gasoline engine and natural gas engine or the fixing tail gas clean-up of lean burn device.
Claims (7)
1. one kind is used for the catalyst of purification of combustion tail gas, be used for optionally reducing and remove in the Rarefied combustion tail gas nitrogen oxide and oxidation and remove imperfect combustion hydrocarbon and carbon monoxide, it is characterized in that Ag and the Ag of this catalyst by metallic element weight scaled value 0.1-17%
2O component load is held on the porous inorganic oxide carrier and constitutes Ag and Ag
2O component average grain diameter is the 10-50 nanometer.
2. catalyst as claimed in claim 1, it is characterized in that porous inorganic oxide carrier is alundum (Al, silica, zeolite, sepiolite, titanium dioxide, zirconium dioxide, zinc oxide, magnesia, tin ash one or more hopcalites or its composite oxides wherein, porous inorganic oxide carrier has 10 meters squared per gram or bigger specific area, and porous inorganic oxide carrier is Powdered or moulding coccoid.
3. as the described catalyst of claim 1-2, it is characterized in that catalyst is coated in the form of coating on the wall surface of circulation passage of pottery or metal honeycomb, or catalyst is made spherical or tabular.
4. the Application of Catalyst of making as one of claim 1-3, it is characterized in that being applied to purify the nitrogen oxide in the Rarefied combustion tail gas, be applicable to motor-driven or the fixed combustion device; when imperfect combustion hydrocarbon and carbon monoxide content are not enough to be used for nitrogen oxides reduction under the lean burn situation, the mixture that needs to add hydrocarbon or oxygen-bearing organic matter or hydrocarbon and oxygen-bearing organic matter as reducing agent with nitrogen oxides reduction.
5. application as claimed in claim 4 is characterized in that motor-driven or the fixed combustion device comprises Diesel engine, lean-burn gasoline engine and natural gas engine.
6. application as claimed in claim 4, it is characterized in that reducing agent is that second is rare, acetylene, third rare, propane, gasoline, heptane, diesel oil, hexadecane, acetaldehyde, acetone, contain the above alcohols of two carbon atoms, and composition thereof, the requirement of reducing agent is 0.3-5 a times of nitrogen oxide weight in the aforementioned tail gas.
7. as the described application of claim 4-6, it is characterized in that catalyst places the exhaust pipe way, the mixture and the tail gas that add hydrocarbon or oxygen-bearing organic matter or hydrocarbon and oxygen-bearing organic matter in the upstream of catalyst mix, gaseous mixture is contacted with catalyst at 150-600 ℃, thereby make the mixture reaction of nitrogen oxide and hydrocarbon or oxygen-bearing organic matter or hydrocarbon and oxygen-bearing organic matter be reduced into nitrogen, unnecessary reducing agent is oxidized to carbon dioxide and water.
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| CN 02100669 CN1209191C (en) | 2002-02-20 | 2002-02-20 | Rarefied combustion tail gas nitrogen oxide purification catalyst and its purification |
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| CN 02100669 CN1209191C (en) | 2002-02-20 | 2002-02-20 | Rarefied combustion tail gas nitrogen oxide purification catalyst and its purification |
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Families Citing this family (9)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN100355488C (en) * | 2003-05-07 | 2007-12-19 | 韩国高化环保技术有限公司 | Catalytic process for nitrogen oxides reduction by multi-injection and use thereof |
| CN100560204C (en) * | 2003-12-24 | 2009-11-18 | 中国科学院生态环境研究中心 | Catalyst for purification of nitrogen oxides in the sulfur-bearing oxygen enrichment tail gas |
| CN1795970B (en) * | 2004-12-28 | 2011-04-13 | 中国科学院生态环境研究中心 | High performance catalyst for catalyzing formaldehyde to complete oxidation under room temperature temperature |
| CN100371072C (en) * | 2005-09-30 | 2008-02-27 | 清华大学 | Preparation process of selective reduction catalyst for lean-burn gasoline motor car exhausted gas nitrogen oxide |
| CN103055694B (en) * | 2011-10-21 | 2015-08-12 | 中国石油化工股份有限公司 | A kind of method utilizing organic exhaust gas to carry out denitrating flue gas |
| CN103386328B (en) * | 2013-07-11 | 2015-07-08 | 南京吉安特环保技术有限公司 | Novel coating material of ternary catalyst for purifying automobile tailing gas and preparation method thereof |
| CN108043381A (en) * | 2017-12-28 | 2018-05-18 | 安徽宏实光机电高科有限公司 | A kind of preparation method of catalyst carrier material for purifying vehicle exhaust |
| CN112930226A (en) * | 2018-10-22 | 2021-06-08 | 上海必修福企业管理有限公司 | Engine tail gas ozone purification system and method |
| CN109675615A (en) * | 2019-01-09 | 2019-04-26 | 无锡威孚环保催化剂有限公司 | Improve low temperature NOxThe lean-burn NO of transformation efficiencyxTrap catalyst and preparation method thereof |
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Assignee: Changzhou hi tech Environmental Protection Technology Co Ltd Assignor: Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences Contract record no.: 2010320000436 Denomination of invention: Rarefied combustion tail gas nitrogen oxide purification catalyst and its purification Granted publication date: 20050706 License type: Exclusive License Open date: 20030903 Record date: 20100504 |
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