A kind of SCR catalyst for denitrating flue gas and preparation method thereof
Technical field
The present invention relates to the catalyst of SCR denitrating flue gas.
Background technology
NO in the boiler smoke
XMainly comprise NO, NO
2, N
2O (the general designation nitrogen oxide abbreviates " nitre " as) is one of atmosphere primary pollution source, and it can cause that not only acid rain, photochemical fog, greenhouse effects etc. destroy a series of problems of ball ecological environment, but also the health that is directly endangering human body.Administer NO
XOne of main method of polluting is NO in the flue gas
XBe reduced to N
2(nitrogen, this process is called denitrating flue gas), NH
3(ammonia) is again the most effectively reducing agent of having found so far.Wherein, in denitrification apparatus, set up catalytic unit and selection of catalysts property catalytic reduction (SCR) method of denitration thereof, than only using reducing agent NH
3Non-selective catalytic reduction (SNCR) method of denitration much superior, the former not only denitration rate is much higher but also NH than the latter
3Consumption and escape amount all be lower than the latter again.In other words, catalyst is to improve denitration rate, reduction improvement NO
XIt is active that the key of cost, some metal oxide have required denitration catalyst.At present to use morely be with itself the TiO of catalytic activity to be arranged also commercial
2(titanium dioxide) is carrier, V
2O
5The TiO that (vanadic anhydride) constitutes for main active constituent load above that
2-V
2O
5Catalyst system and catalyzing, application number are 200810224389.2 and are called " a kind of with TiO
2Be denitrating catalyst of raw material and preparation method thereof " in goods be exactly one of them.This denitrating catalyst is at TiO
2-V
2O
5On the catalyst system and catalyzing basis, increased a certain amount of co-catalyst WO
3(tungstic acid); In addition, the support structure material that in addition this denitrating catalyst is bonded together in its component (this case is called " auxiliary agent "), these auxiliary agents comprise clay, glass fibre and PEO etc.Yet, because this denitrating catalyst remains TiO after all
2-V
2O
5A kind of in the catalyst system and catalyzing (mainly is V so still there are raw material
2O
5) the higher relatively deficiency of cost; Especially this type catalyst need descend the competence exertion effect in higher flue-gas temperature (generally being 300 ℃~400 ℃), and impels down SO in high concentrate dust and the flue gas at higher temperature
2Cause poisoning again easily, so this type catalyst also has the deficiency of service life than weak point; And, SO in flue gas
2When concentration was higher, the catalytic activity of this type catalyst also can reduce.In addition, in this denitrating catalyst process of preparation, its technical process is relative complex also, for example, need to mix the tungsten titanium valve and make through a calcination, grinding, then with operations such as the residue component mixes after, need calcination (activation) again once.
Summary of the invention
First purpose of the present invention is, provide that a kind of cost is relatively low, temperature applicable range that broad is arranged, at higher SO
2Also can bring into play the SCR catalyst for denitrating flue gas of catalytic action under concentration, the low flue-gas temperature preferably.
Second purpose of the present invention is that a kind of preparation technology is provided the simple preparation method who realizes the SCR catalyst for denitrating flue gas of first goal of the invention.
The scheme that realizes said first goal of the invention is a kind of like this SCR catalyst for denitrating flue gas, and the aspect identical with prior art is to comprise carrier TiO in this denitrating catalyst component
2, load on TiO
2On main active constituent and co-catalyst WO
3, and with the support structure material of the bonding one-tenth particle of this denitrating catalyst, wherein, TiO
2Form with anatase titanium dioxide exists.Its improvements are that said main active constituent is MnO
2(manganese dioxide), said support structure material is Al
2O
3Gel (alundum (Al gel); The mass percentage content of each component is in this denitrating catalyst: 10% TiO
2, 4%~10% MnO
2, 4%~10% WO
3, surplus is Al
2O
3Gel; Said denitrating catalyst particle grain size is 0.8~1.2cm.
The scheme that realizes said second goal of the invention is a kind of like this preparation method of SCR catalyst for denitrating flue gas, and this catalyst for denitrating flue gas is a SCR catalyst for denitrating flue gas of realizing said first goal of the invention, and this method comprises the steps:
(1) preparation active constituent solution: with said WO
3Content is as the criterion, and takes by weighing (NH after the conversion
4)
5H
5[H
2(WO
4)
6] H
2O (ammonium tungstate) adds deionized water then, and under 50 ℃~80 ℃ temperature, is stirred to dissolving fully, obtains (NH
4)
5H
5[H
2(WO
4)
6] H
2O solution; Wherein, (NH
4)
5H
5[H
2(WO
4)
6] H
2O: deionized water=1g: 40ml;
According to the mass percent of each component in the said denitrating catalyst, again with said MnO
2Content is as the criterion, and takes by weighing Mn (CH after the conversion
3COO)
24H
2O (manganese acetate) adds above-mentioned (NH then
4)
5H
5[H
2(WO
4)
6] H
2In the O solution, and under 50 ℃~80 ℃ temperature, be stirred to dissolving fully, obtain active constituent solution;
(2) catalyst powder preparation: the mass percent according to each component in the said denitrating catalyst takes by weighing said TiO
2Powder, join in the active constituent solution of step (1) gained, stir down fully at 45 ℃~55 ℃ then, with said (NH
4)
5H
5[H
2(WO
4)
6] H
2O and Mn (CH
3COO)
24H
2O loads on this TiO
2On the carrier, the time is no less than 30min;
Be warming up to 78 ℃~82 ℃ then, under this temperature, evaporate the part deionized water, obtain tungsten-manganese/titanium slurry; The evaporation capacity of this deionized water is beneficial in (3) step of back and said Al with the flowability of gained tungsten-manganese/titanium slurry
2O
3Gel is degree of being mixed into fully;
(3) powder shaping of catalyst: according to the mass percent of each component in the said denitrating catalyst, with step (2) gained tungsten-manganese/titanium slurry, under natural cooling state and said Al
2O
3Gel fully mixes, and gets the powder catalyst pulp;
Continue to evaporate the part deionized water then, the evaporation capacity of current deionized water is beneficial to then rubbing, processes particle for spending; These particle grain size are that 0.8~1.2cm is as the criterion with (4) step gained denitrating catalyst particle grain size of back;
(4) catalyst activation: step (3) gained particle is placed on earlier under 70 ℃~90 ℃ and 90 ℃~100 ℃ respectively dried by the fire 2 hours, and then these particles are placed on 1 hour, 440 ℃~460 ℃ roastings of 250 ℃~270 ℃ roastings 2 hours earlier, load on TiO to let
2On (NH
4)
5H
5[H
2(WO
4)
6] H
2O and Mn (CH
3COO)
24H
2O decomposes in roasting process, is converted into WO
3And MnO
2Be evenly dispersed in carrier TiO
2On the surface;
Then, naturally cool to room temperature, get said catalyst for denitrating flue gas.
From the scheme that realizes first goal of the invention, can find out, in SCR catalyst for denitrating flue gas of the present invention, be the equal of to use MnO
2Replaced V in the prior art
2O
5The main active constituent that this price is more expensive, total consumption of other active constituents are also than the lacking of prior art, so its cost of material just decreases.From the scheme that realizes second goal of the invention, can find out; The present invention not directly tungstic acid and manganese dioxide load on titanium dioxide, but be the transition component with ammonium tungstate, manganese acetate, let them load on the titanium dioxide earlier; Add the alundum (Al gel cementing again and as its support structure; Then through moulding, steps such as oven dry, roasting one by one, with ammonium tungstate and the manganese acetate decomposition that lets on the titanium dioxide, be converted into tungstic acid and manganese dioxide.So, tungstic acid and the manganese dioxide as final component just can extremely be evenly dispersed in the carrier titanium dioxide surface; Owing to only carry out calcination for activation one time, therefore, the inventive method not only has the advantage of the catalytic activity of the catalyst for denitrating flue gas that can further improve the present invention again, but also it is simple to have a technological process, has practiced thrift the advantage of Preparation of catalysts time.Therefore, reduced the totle drilling cost of goods SCR catalyst for denitrating flue gas of the present invention.
In the SCR catalyst for denitrating flue gas of the present invention; Titanium dioxide, manganese dioxide and tungstic acid can combine well; Not only improved the denitration rate; Also increased the temperature window of catalyst, made it denitration activity preferably all arranged, heat endurance has preferably been arranged again 250 ℃~400 ℃ temperature ranges 150 ℃~250 ℃ temperature ranges.So the life-span of its catalytic activity is able to prolong relatively.Again owing to combined MnO
2Catalyst for denitrating flue gas have good anti-sulphur property, so not only can be because of there be SO in catalyst for denitrating flue gas of the present invention in the flue gas
2And poison, and work as SO
2When concentration is higher, also still can keep advantages of high catalytic activity.
In a word, the present invention is that a kind of preparation technology is simple relatively, cost is relatively low, and the temperature applicable range of broad, the higher relatively SCR catalyst for denitrating flue gas of sulfur resistance, and its denitration are preferably arranged.
Below in conjunction with the specific embodiment the present invention is further described.
The specific embodiment
One, a kind of SCR catalyst for denitrating flue gas comprises carrier TiO in this denitrating catalyst component
2, load on TiO
2On main active constituent and co-catalyst WO
3, and with the support structure material of the bonding one-tenth particle of this denitrating catalyst, wherein, TiO
2Form with anatase titanium dioxide exists.In the present invention, said main active constituent is MnO
2, said support structure material is Al
2O
3Gel; The mass percentage content of each component is in this denitrating catalyst: 10% TiO
2, 4%~10% MnO
2, 4%~10% WO
3, surplus is Al
2O
3Gel; Said denitrating catalyst particle grain size is 0.8~1.2cm.
Two, a kind of preparation method of SCR catalyst for denitrating flue gas, this catalyst for denitrating flue gas is the above-mentioned specific embodiment one described SCR catalyst for denitrating flue gas, this method comprises the steps:
(1) preparation active constituent solution: with said WO
3Content is as the criterion, and takes by weighing (NH after the conversion
4)
5H
5[H
2(WO
4)
6] H
2O adds deionized water then, and under 50 ℃~80 ℃ temperature, be stirred to fully dissolving (actual temp is with degree of being dissolved as fully, when being lower than 50 ℃ dissolving slower, ammonia volatilizees easily too much when being higher than 80 ℃), obtain (NH
4)
5H
5[H
2(WO
4)
6] H
2O solution; Wherein, (NH
4)
5H
5[H
2(WO
4)
6] H
2O: deionized water=1g: 40ml;
According to the mass percent of each component in the said denitrating catalyst, again with said MnO
2Content is as the criterion, and takes by weighing Mn (CH after the conversion
3COO)
24H
2O, adding then should (NH
4)
5H
5[H
2(WO
4)
6] H
2In the O solution, and under 50 ℃~80 ℃ temperature, be stirred to fully dissolving, obtain active constituent solution (actual temp is also with degree of being dissolved as fully, when being lower than 50 ℃ dissolving slower, ammonia volatilizees easily too much when being higher than 80 ℃);
(2) catalyst powder preparation: the mass percent according to each component in the said denitrating catalyst takes by weighing said TiO
2Powder, join in the active constituent solution of step (1) gained, stir down fully at 45 ℃~55 ℃ then, with said (NH
4)
5H
5[H
2(WO
4)
6] H
2O and Mn (CH
3COO)
24H
2O loads on this TiO
2On the carrier, the time is no less than 30min;
Be warming up to 78 ℃~82 ℃ then, under this temperature, evaporate the part deionized water, obtain tungsten-manganese/titanium slurry; The evaporation capacity of this deionized water is beneficial in (3) step of back and said Al with the flowability of gained tungsten-manganese/titanium slurry
2O
3Gel is degree of being mixed into fully---and that is to say, in (3) step of back, also need further evaporate some deionized waters;
(3) powder shaping of catalyst: according to the mass percent of each component in the said denitrating catalyst, with step (2) gained tungsten-manganese/titanium slurry, under natural cooling state and said Al
2O
3Gel fully mixes, and gets the powder catalyst pulp;
Continue to evaporate the part deionized water then; The evaporation capacity of current deionized water, being beneficial to then rubbing, processing particle is that degree (carries out rubbing, granulation for the preparation catalyst granules to those skilled in the art; The prior art known of right and wrong Changshu is not so be described in detail); These particle grain size are that 0.8~1.2cm is as the criterion with (4) step gained denitrating catalyst particle grain size of back---also i.e. denitrating catalyst particle grain size in this step needs than the particle diameter of end article approximately more greatly.Owing to both can confirm according to conventional experience, also can confirm through limited routine test, so, do not detail yet;
(4) catalyst activation: step (3) gained particle is placed on earlier under 70 ℃~90 ℃ and 90 ℃~100 ℃ respectively dried by the fire 2 hours, and then these particles are placed on 1 hour, 440 ℃~460 ℃ roastings of 250 ℃~270 ℃ roastings 2 hours earlier, load on TiO to let
2On (NH
4)
5H
5[H
2(WO
4)
6] H
2O and Mn (CH
3COO)
24H
2O decomposes in roasting process, is converted into WO
3And MnO
2Be evenly dispersed in carrier TiO
2On the surface;
Then, naturally cool to room temperature, get said catalyst for denitrating flue gas.
Specify that the temperature range in each stage that relates in step (2), (4) specifically is meant the last lower deviation of permission.
Passed through experimental verification by the present invention.During checking, at first prepared the SCR catalyst for denitrating flue gas of different component ratios respectively, then these catalyst have been put in the fixed-bed tube reactor respectively with said method.Simulated flue gas has been used respectively and has not been contained SO
2With contain SO
2Two kinds.
With not containing SO
2Simulated flue gas the time, be 10000h in air speed
-1, flue-gas temperature is under 100 ℃~400 ℃ the condition, will contain the simulated flue gas of 500ppmNO and the reducing gas NH of 500ppm concentration
3, feed this reactor with 1: 1 ratio; The concentration of NO in the simulated flue gas of last detection reaction device outlet, thus calculate the denitration rate.The checking result sees table 1.
Table 1
Because the SO in the flue gas
2Causing that catalyst for denitrating flue gas poisons, is to occur under the higher environment of flue-gas temperature, so with containing SO
2Simulated flue gas when each example in the his-and-hers watches 1 is verified once more, only under 350 ℃ and 400 ℃ of two temperature conditions, carry out.During concrete the checking, be 10000h in air speed
-1, with the SO of concentration 400~2000ppm
2With the simulation mixed flue gas of 500ppmNO and the reducing gas NH of 500ppm concentration
3, with NH
3: NO is that 1: 1 ratio feeds this reactor; The concentration of NO in the simulated flue gas of last detection reaction device outlet, thus calculate the denitration rate.The checking result sees table 2.
Table 2
Can find out that from above-mentioned checking example SCR catalyst for denitrating flue gas of the present invention under 150~400 ℃ flue-gas temperature condition, all has denitration effect preferably; Under the flue-gas temperature conditions of higher, anti-sulphur effect is also better.