CN1123375C - Process of partially selective reducting of NO for hydrogen under oxygen-enrciched condition - Google Patents
Process of partially selective reducting of NO for hydrogen under oxygen-enrciched condition Download PDFInfo
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- CN1123375C CN1123375C CN98114397A CN98114397A CN1123375C CN 1123375 C CN1123375 C CN 1123375C CN 98114397 A CN98114397 A CN 98114397A CN 98114397 A CN98114397 A CN 98114397A CN 1123375 C CN1123375 C CN 1123375C
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Abstract
The present invention relates to a method for partially and selectively reducing NO by hydrogen under an oxygen-enriched condition. The present invention is characterized in that the reaction of the selective reduction of NO is carried out under the conditions that active uneven Pd/Al2O3 catalysts are used, namely Pd active components forms eggshell-shaped distribution on carriers, and the content of Pd is from 0.1 to 0.5% weight; hydrogen with the quantity smaller than the stoichiometry ratio for reaction of oxygen in waste gas is led in under an oxygen-enriched condition, and the molar ratio of hydrogen and oxygen is between 0.25 and 2; the operation temperature is from normal temperature to 250 DEG C at lower temperature. The present invention has the advantages of high NO elimination rate, low operation temperature, low hydrogen consumption, low dosage of catalysts and noble metal, simple flow path and convenient operation.
Description
The present invention relates to fields such as environmental protection, Industrial Catalysis, gas purification.Provide first one active non-uniform Pd (M)/Al
2O
3On the catalyst, under the excess oxygen, the new way of hydrogen partial Selective Catalytic Reduction of NO.
In industry such as chemistry, electric power, the toxic emission that contains NO is in a large number arranged in atmosphere.NO can become environmental problems such as acid rain, photochemical fog, photochemical pollution through a series of variations, and the mankind and ecological environment are caused huge infringement.The processing of NO becomes more and more important in the waste gas.Hydrogen partial Selective Catalytic Reduction of NO method is one of numerous NO removal methods, generally is on noble metal catalyst (Pd, Pt, Rh), adds to surpass and O in waste gas
2, NO carries out the hydrogen of the metering ratio of chemical reaction, makes O
2, the basic complete reaction of NO, reach the purpose that removes NO.Because reacting, a large amount of hydrogen and reducing agent produce a large amount of heat, so generally be furnished with energy-recuperation system.This process exists significantly not enough:
(1) the hydrogen amount of allocating into is big, reducing agent expense height;
(2) reaction temperature height, equipment investment is big;
(3) catalyst noble metal dosage height is generally 0.5～1% (by weight);
(4) be not suitable for the high atmosphere of oxygen content.
The object of the present invention is to provide the method for hydrogen partial selective reduction NO under a kind of excess oxygen, its NO removal efficiency height, operating temperature is low, and hydrogen-consuming volume is low, and the catalyst noble metal dosage is few, and flow process is simple, and is easy to operate.
The invention provides the method for hydrogen partial selective reduction NO under a kind of excess oxygen, it is characterized in that the reaction of selective reduction NO is carried out under the following conditions:
(1) uses active non-uniform Pd/Al
2O
3Catalyst, promptly the Pd active constituent is the eggshell type distribution on carrier, and Pd content is 0.1～0.5% weight;
(2) under excess oxygen, promptly allocate the stoichiometric proportion of reacting that the hydrogen amount is lower than oxygen in the waste gas into, the hydrogen-oxygen mol ratio is between 0.25～2;
(3) at a lower temperature, operating temperature normal temperature～250 ℃.
In the catalyst of the present invention, that can also add Sr, Mg, Ca, Mn, Cr, V, Zn a kind ofly is auxiliary agent, and content is 0.1～10% weight.
Principle of the present invention be utilize active non-uniform Pd (M)/Al
2O
3On the catalyst, hydrogen reduction NO is reflected in the parallel competition process with oxyhydrogen reaction and preponderates, thereby realizes the hydrogen partial selective reduction NO process under the excess oxygen.Under normal temperature, the low temperature (15～250 ℃), hydrogen reduction NO selectivity height, the NO removal efficiency is up to 80～100%; Under the high temperature (250～700 ℃), hydrogen reduction NO selectivity is low, the corresponding reduction of NO removal efficiency.Key reaction is as follows:
Reaction I II III is the NO reduction reaction, and reaction IV is an oxyhydrogen reaction.After reaction causes, H
2Distribute to NO, O simultaneously
2Carry out reduction reaction and oxyhydrogen reaction.The key of this process is to control temperature, and guaranteeing has enough hydrogen and NO to carry out reduction reaction I, II, III.
The present invention adopt with Pd be main active constituent low palladium content active non-uniform Pd (M)/Al
2O
3Catalyst.This catalyst has active high and low temperature stability and reaches the advantage that repeatedly startability is good, noble metal dosage is few.The consumption of noble metal only is 0.1～0.5%, than low 5～10 times of the noble metal dosage of custom catalysts, thereby the catalyst price is reduced significantly.
The present invention adopts hydrogen as part selective reduction agent, and the hydrogen amount of allocating into is regulated according to the oxygen amount in the waste gas.Oxygen amount height, the hydrogen amount height of allocating into; Otherwise it is low to join the hydrogen amount.The hydrogen amount of allocating into is lower than the stoichiometric proportion of reacting with oxygen all the time.Make that the reducing agent consumption is few, effectively reduced the expense of reducing agent.The hydrogen of allocating into both can adopt pure hydrogen, also can adopt thick hydrogen or useless hydrogen, can further reduce the reducing agent expense like this.
Reaction initiation temperature of the present invention low (35～50 ℃) after reaction causes, utilizes reaction heat to keep operating temperature (50～250 ℃), effectively reduces energy consumption.
Below by embodiment in detail the present invention is described in detail:
Accompanying drawing 1 is tail gas H
2, O
2Content and the temperature variant result of NO removal efficiency;
-mouth-tail gas hydrogen content-■-tail gas oxygen content-●-NO removal efficiency
Accompanying drawing 2 is that bed temperature and NO removal efficiency are to duration of ventilation figure;
-●-bed temperature-mouth-NO removal efficiency
Accompanying drawing 3 is that Pd content is to catalytic activity influence figure;
-■-6×10
-6Pd/Al
2O
3 -●-8×10
-5Pd/Al
2O
3
-▲-1.28×10
-3Pd/Al
2O
3 --4.93×10
-3Pd/Al
2O
3
Accompanying drawing 4 is different Pd content catalyst hydrogen consumption curve maps.
--6×10
-6Pd/Al
2O
3 -▲-8×10
-5Pd/Al
2O
3
-●-1.28×10
-3Pd/Al
2O
3 -■-4.93×10
-3Pd/Al
2O
3
Accompanying drawing 5 is at 0.405%Mg/Al
2O
3Last NO removal efficiency and tail gas hydrogen content are with variation of temperature figure.
-●-NO removal efficiency-zero-tail gas hydrogen content
Embodiment 1
Get φ 3～4mm, intensity 〉=5kgf/cm
2Ball-aluminium oxide be carrier, carrier was carried out the presaturation adsorption treatment 12 hours with 40% oxygen-containing organic compound acetaldehyde.Claim the 120mg palladium, use the 1ml aqua regia dissolution, volume is controlled at 20ml, this solution of the carrier impregnation that the 20g preliminary treatment is good 5 minutes is 1200 ℃ of high-temperature heat treatment after 20 minutes, 800 ℃ of roastings 4 hours, after the cooling, the hydrazine solution with 1% reduces above-mentioned catalyst, and reduction is the back cleaning-drying fully.Get 0.128% active non-uniform Pd/Al
2O
3Catalyst.
Get the carrier identical 50 grams with embodiment 1, to carrier with 35% ethanolic solution presaturation adsorption treatment 12 hours, with the PdCl of 2.3g
2, 0.03gSrCO
3With 3mlHCl dissolving, the 50ml that the control volume is is with this solution of carrier impregnation of handling well 2 minutes, 1200 ℃ of high-temperature heat treatment 10 minutes, again 800 ℃ of following roastings 2 hours, after the cooling, the hydrazine solution with 1% reduces above-mentioned catalyst 12 hours, clean the chlorine root, alkalescence and impurity, drying.Get 0.49%Pd, 0.006%Sr non-uniform activity distribution catalyst.
Embodiment 3
Get the carrier identical 50 grams, carrier was carried out the presaturation adsorption treatment 12 hours with 40% oxygen-containing organic compound acetaldehyde with embodiment 1.Take by weighing 10 milligrams of palladiums, with chloroazotic acid it is dissolved fully, volume is 50 milliliters, this solution of the carrier impregnation that preliminary treatment is good 1 minute, 1200 ℃ of high-temperature heat treatment 10 minutes, 800 ℃ of roastings 4 hours, after the cooling, the hydrazine solution with 1% reduces above-mentioned catalyst, and reduction is the back cleaning-drying fully.Obtain Pd content and be 0.008% non-uniform activity distribution catalyst; Using the same method and also obtaining Pd content is 0.0006% non-uniform activity distribution catalyst.
Embodiment 4
Get the carrier identical with embodiment 1 50 grams, using the method identical with embodiment 3 to prepare Mg content is 0.405% Mg/Al
2O
3Catalyst.
Embodiment 5
The active non-uniform Pd/Al of filling 0.5 gram embodiment 1 in normal pressure, fixed bed reactors
2O
3Catalyst, experiment condition: NO=1000 ± 20ppm, H
2=4%, O
2=3%, surplus is N
2, S.V.=1000ml/ghr obtains the temperature variant result of hydrogen-oxygen content such as Fig. 1 in NO conversion ratio and the tail gas.
From then among the figure as can be seen, the H that allocates into
2After the complete reaction, the residual O that has about 1% in the waste gas
2, be removing for NO under the excess oxygen.Under normal temperature, low temperature, NO has very high removal efficiency, and 100～200 ℃, the NO removal efficiency is higher than 90%; With the rising of temperature, the NO removal efficiency descends, and has realized under the excess oxygen hydrogen partial Selective Catalytic Reduction of NO process.
Embodiment 6
Under the identical condition of consersion unit and catalyst and embodiment 5, change H
2Content, all the other experiment conditions are identical with embodiment 5, obtain 115 ℃, the NO of different hydro content condition and remove counting rate meter 1.
The NO removal efficiency of 115 ℃ in table 1, different hydro content condition
| H 2(％) | 1 | 2 | 3 | 4 | 5 | 6.6 |
| R NO(％) | 85.3 | 87.9 | 93.8 | 96.2 | 100 | 100 |
From then on the table in as can be seen, for 3%O
2Condition under, allocate 1% hydrogen into and can make removing of NO be higher than 80%.Allocating between the hydrogen amount 1～6.6%, the NO removal efficiency is 85～100%.
Embodiment 7
Under the identical condition of consersion unit, catalyst, experiment condition and embodiment 5, obtain 100 ℃ catalyst stability table 2 as a result.
The catalyst stability result that table 2 is 100 ℃
| Time (h) | 4 | 8 | 12 | 16 | 20 | 24 |
| R NO(％) | 98.5 | 98.3 | 98.6 | 98.4 | 98.5 | 98.4 |
From then on find out that catalyst has good low-temperature stability in the table.
Under the identical condition of consersion unit, catalyst, gas composition, reaction velocity and embodiment 5, change the mode of operations, promptly feed H earlier
2, O
2, N
2Gas, oxyhydrogen reaction feed NO after proceeding to and stablizing again, obtain Fig. 2.From then on figure as seen, when 48 ℃ of beds, the removal efficiency of NO reaches more than 95%.Promptly utilize method of operating, can realize not having external heat, under the low temperature, NO removes more fully.
Embodiment 9
The temperature variant result of table 3 NO removal efficiency
| Temperature (℃) | 23.5 | 35.6 | 67 | 100 | 150 | 200 |
| R NO(％) | 26.3 | 66.1 | 89.7 | 100 | 99.8 | 96.2 |
From then on show as can be seen, this catalyst can reach higher NO removal efficiency at low temperatures.
3 two catalyst of embodiment are seated in the consersion unit identical with embodiment 5, under the experiment condition identical, obtain the temperature variant result of NO removal efficiency such as Fig. 3 and hydrogen consumption curve map 4 with embodiment 5.
Embodiment 11
Embodiment 4 catalyst are seated in the consersion unit identical with embodiment 5, under the experiment condition identical, obtain the temperature variant result of NO removal efficiency and tail gas hydrogen content result such as Fig. 5 with embodiment 5.This catalyst is (below 200 ℃) basic non-activity at low temperatures, and has high catalytic activity at middle warm area (300～400 ℃).High activity also can reach 100%.
Comparative example
Preparing palladium content with the method for incipient impregnation is 0.5% Pd/Al
2O
3Catalyst.In normal pressure, fixed bed reactors, load 100 milliliters of these catalyst, feed and consist of 3000ppm NO, 1.28%H
2, 3%O
2, surplus is N
2Gas, at S.V.=12000CFH/CF, under 282 ℃, the NO removal efficiency is 12.5%.
Claims (2)
1. the method for hydrogen partial selective reduction NO under the excess oxygen is characterized in that the reaction of selective reduction NO is carried out under the following conditions:
(1) uses active non-uniform Pd/Al
2O
3Catalyst, promptly the Pd active constituent is the eggshell type distribution on carrier, and Pd content is 0.1～0.5% weight;
(2) under excess oxygen, promptly allocate the stoichiometric proportion of reacting that the hydrogen amount is lower than oxygen in the waste gas into, the hydrogen-oxygen mol ratio is between 0.25～2;
(3) at a lower temperature, operating temperature normal temperature～250 ℃.
2. according to the method for hydrogen partial selective reduction NO under the described excess oxygen of claim 1, it is characterized in that: what also contain Sr, Mg, Ca, Mn, Cr, V, Zn in the catalyst a kind ofly is auxiliary agent, and content is 0.1～10% weight.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN98114397A CN1123375C (en) | 1998-10-21 | 1998-10-21 | Process of partially selective reducting of NO for hydrogen under oxygen-enrciched condition |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN98114397A CN1123375C (en) | 1998-10-21 | 1998-10-21 | Process of partially selective reducting of NO for hydrogen under oxygen-enrciched condition |
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| Publication Number | Publication Date |
|---|---|
| CN1251316A CN1251316A (en) | 2000-04-26 |
| CN1123375C true CN1123375C (en) | 2003-10-08 |
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| CN98114397A Expired - Fee Related CN1123375C (en) | 1998-10-21 | 1998-10-21 | Process of partially selective reducting of NO for hydrogen under oxygen-enrciched condition |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102451715B (en) * | 2010-10-15 | 2013-10-09 | 中国石油化工股份有限公司 | Selective hydrogenation de-diene catalyst and preparation method thereof |
| CN102430415A (en) * | 2011-09-16 | 2012-05-02 | 华东理工大学 | Solid acid catalyst for selective catalystic reduction of NOx by methane and preparation method thereof |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57127446A (en) * | 1981-01-29 | 1982-08-07 | Mitsui Mining & Smelting Co Ltd | Catalyst for gas purification |
| JPS58210860A (en) * | 1982-06-01 | 1983-12-08 | Hiroyoshi Inoue | Alloy catalyst for reduction and its production |
| US4981659A (en) * | 1988-12-14 | 1991-01-01 | Atomic Energy Of Canada Limited | Reduction of nitrogen oxides |
| CN1070352A (en) * | 1991-08-01 | 1993-03-31 | 气体产品与化学公司 | The catalytic reduction that nitrogen oxide carries out with methane in the presence of oxygen |
| JPH07108139A (en) * | 1993-10-12 | 1995-04-25 | Toyota Central Res & Dev Lab Inc | Exhaust gas purifying device |
| CN1138833A (en) * | 1994-02-15 | 1996-12-25 | 罗伯特·博施有限公司 | Device and process for reducing the quantity of pollutants in combustion exhaust gases |
-
1998
- 1998-10-21 CN CN98114397A patent/CN1123375C/en not_active Expired - Fee Related
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS57127446A (en) * | 1981-01-29 | 1982-08-07 | Mitsui Mining & Smelting Co Ltd | Catalyst for gas purification |
| JPS58210860A (en) * | 1982-06-01 | 1983-12-08 | Hiroyoshi Inoue | Alloy catalyst for reduction and its production |
| US4981659A (en) * | 1988-12-14 | 1991-01-01 | Atomic Energy Of Canada Limited | Reduction of nitrogen oxides |
| CN1070352A (en) * | 1991-08-01 | 1993-03-31 | 气体产品与化学公司 | The catalytic reduction that nitrogen oxide carries out with methane in the presence of oxygen |
| JPH07108139A (en) * | 1993-10-12 | 1995-04-25 | Toyota Central Res & Dev Lab Inc | Exhaust gas purifying device |
| CN1138833A (en) * | 1994-02-15 | 1996-12-25 | 罗伯特·博施有限公司 | Device and process for reducing the quantity of pollutants in combustion exhaust gases |
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| CN1251316A (en) | 2000-04-26 |
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