CN104128193B - A kind of CeO 2base SCR catalyst and preparation method thereof - Google Patents
A kind of CeO 2base SCR catalyst and preparation method thereof Download PDFInfo
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- CN104128193B CN104128193B CN201410368155.0A CN201410368155A CN104128193B CN 104128193 B CN104128193 B CN 104128193B CN 201410368155 A CN201410368155 A CN 201410368155A CN 104128193 B CN104128193 B CN 104128193B
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Abstract
The invention discloses a kind of CeO
2base SCR catalyst and preparation method thereof, preparation method comprises the following steps: get and appropriate comprise CeO
2metal-oxide powder or comprise the metal salt solution of soluble salt solutions of Ce; The soluble-salt getting appropriate soluble phosphate and zirconium makes mixed aqueous solution, Zr in described mixed aqueous solution
4+and PO
4 3-mol ratio be 0.5 ~ 2, Zr
4+and PO
4 3-ion concentration sum be 0.1 ~ 5mol/L; Zr
4+and PO
4 3-the heteropoly acid material of porous is formed in mixed aqueous solution; Use infusion process by the surface of heteropoly acid species adsorbs at metal oxide, or use sol-gel process, by complexing agent, the soluble salt solutions of Ce is formed colloidal sol together with the complexing of heteropoly acid material, finally equal Kaolinite Preparation of Catalyst powder after super-dry, roasting.In catalyst, the mass fraction of metal oxide is 60% ~ 95%; The mass fraction of heteropoly acid material is 5% ~ 40%.The catalyst water resistant heat ageing that the present invention obtains, the ability of sulfuration resistant are comparatively strong, and cost is lower.
Description
[technical field]
The present invention relates to SCR catalyst, particularly relate to a kind of CeO
2base SCR catalyst and preparation method thereof.
[background technology]
It is high that diesel vehicle has the thermal efficiency compared to gasoline car, economical good, CO
2discharge low feature; but due to the feature of diesel car engine; NOx and particle (the dissolved organic matter SOF of liquid phase and the solid particulate matter such as the dry soot C of solid phase and sulfate) discharge comparatively gasoline overall height; wherein NOx a kind of main polluter especially, all constitutes great harm for environmental protection and health.Diesel engine owing to being lean-combustion engine, the O in tail gas
2concentration higher (> 6%), therefore three-way catalyst (TWC) can not be utilized carry out the removal of NOx as gasoline car, the purified treatment that SCR catalyst carries out NOx must be installed in the after-treatment device of tail gas, for denitration.Power plant and cement plant are owing to using a large amount of coals as fuel; there is in the flue gas of discharge the NOx of high level, in order to requirement and the regulation of the protection that conforms, also in power plant and cement plant, SCR after-treatment device must be installed; SCR catalyst is utilized to carry out the purified treatment of NOx, for denitration.
In the last few years, V
2o
5-WO
3/ TiO
2catalyst is widely used as the commercial catalyst of exhaust gas from diesel vehicle and power plant, smoke denitration of cement plant due to good activity, preferably heat endurance.But V is a kind of poisonous element, flow in nature and produce a large amount of harm by the enrichment of biological chain to environment and human body, this runs counter to the sustainable development view mutually coordinated between environmental protection and economic development.So the exploitation without V catalyst causes the attention of people gradually.CeO
2there is good oxygen migration rate, there is certain redox active simultaneously, be widely used as in gasoline car three-way catalyst.Therefore, people also start to pay close attention to CeO gradually
2application in preparation SCR catalyst.
Existing CeO
2base SCR catalyst is mainly with CeO
2for active component, or with CeO
2and ZrO
2the metal oxide of composition is active component, the basis of active component is added and improves component, such as P
2o
5or Nb
2o
5, by the catalyst cupport (different according to application scenarios, to select different carriers) on carrier obtained.Above-mentioned SCR catalyst, although during NOx purified treatment in certain temperature range the conversion ratio of NOx can reach more than 80%, its sulfuration resistant, water resistant heat aging performance are strong, also limit the use of catalyst.This is because: diesel oil and coal can produce a large amount of high-temperature vapors and SO as fuel combustion
2, therefore SCR catalyst needs to have certain water resistant heat ageing, the ability of sulfuration resistant.
[summary of the invention]
Technical problem to be solved by this invention is: make up above-mentioned the deficiencies in the prior art, proposes a kind of CeO
2base SCR catalyst and preparation method thereof, obtained catalyst water resistant heat ageing, the ability of sulfuration resistant are comparatively strong, and cost is lower, and the conversion ratio of the NOx in simultaneous temperature operation window (250 ~ 450 DEG C) is also higher, meets application demand.
Technical problem of the present invention is solved by following technical scheme:
A kind of CeO
2the preparation method of base SCR catalyst, comprises the following steps: 1) get appropriate metal-oxide powder, and described metal oxide at least comprises CeO
2; 2) soluble-salt getting appropriate soluble phosphate and zirconium makes mixed aqueous solution, Zr in described mixed aqueous solution
4+and PO
4 3-mol ratio be 0.5 ~ 2, the Zr in described mixed aqueous solution
4+and PO
4 3-ion concentration sum be 0.1 ~ 5mol/L; Described Zr
4+and PO
4 3-the heteropoly acid material of porous is formed in described mixed aqueous solution; 3) by step 1) in metal-oxide powder and step 2) in mixed aqueous solution adopt infusion process mix, make described heteropoly acid material be attached to described metal oxide surface; 4) by step 3) mixture that obtains at 80 ~ 120 DEG C of dry process 1 ~ 10h, then roasting 1 ~ 5 hour at 450 ~ 700 DEG C, obtained catalyst powder; Wherein, in the quality of described metal-oxide powder, the quality of the described aqueous solution and the described aqueous solution, the concentration of each ion makes the mass fraction of metal oxide in final obtained catalyst be 60% ~ 95%, and the mass fraction of the heteropoly acid material of described porous is 5% ~ 40%.
A kind of CeO
2the preparation method of base SCR catalyst, comprises the following steps: 1) get appropriate metal salt solution, and described metal salt solution at least comprises the soluble salt solutions of Ce, and Ce
4+ion concentration be 0.1 ~ 5mol/L; 2) soluble-salt getting appropriate soluble phosphate and zirconium makes mixed aqueous solution, Zr in described mixed aqueous solution
4+and PO
4 3-mol ratio be 0.5 ~ 2, the Zr of described mixed aqueous solution
4+and PO
4 3-ion concentration sum be 0.1 ~ 5mol/L; Described Zr
4+and PO
4 3-the heteropoly acid material of porous is formed in described mixed aqueous solution; 3) by step 1) in solution and step 2) in aqueous solution, add appropriate complexing agent, make described heteropoly acid material and described Ce
4+complexing together, is stirred, is obtained solution; Wherein, the gram-equivalent number of complexing agent is 1 ~ 5 times of the gram-equivalent number sum of all metal ions in solution; 4) by step 3) solution that obtains carries out continuous heating stirring at 100 ~ 120 DEG C, evaporate to dryness, forms gel; Gel is placed in drying box and dries 12 hours in 80 ~ 150 DEG C; 5) by step 4) gel solids that obtains or powder smash to pieces, grinding, roasting 0.5 ~ 3 hour at 200 ~ 350 DEG C, and then roasting 1 ~ 5 hour at 450 ~ 700 DEG C, obtains catalyst powder; Wherein, the quality of the soluble salt solutions of described Ce and Ce
4+concentration, Zr in the quality of the described aqueous solution and the described aqueous solution
4+, PO
4 3-concentration make the mass fraction of metal oxide in final obtained catalyst be 60% ~ 95%, the mass fraction of the heteropoly acid material of described porous is 5% ~ 40%.
A kind of CeO
2base SCR catalyst, comprise metal oxide and be attached to metal oxide surface by Zr
4+-and PO
4 3the heteropoly acid material of the porous formed; Wherein, described metal oxide comprises CeO
2, the quality of metal oxide accounts for 60% ~ 95% of whole catalyst quality; Zr in described heteropoly acid material
4+and PO
4 3-mol ratio be 0.5 ~ 2, the quality of described heteropoly acid material accounts for 5% ~ 40% of whole catalyst quality.
The beneficial effect that the present invention is compared with the prior art is:
CeO of the present invention
2base SCR catalyst and preparation method thereof, by Zr in obtained catalyst
4+and PO
4 3-form the heteropoly acid material of porous according to certain mol proportion, this heteropoly acid material is attached to CeO by the mode of dipping or complexing
2the surface of metal oxide.This heteropoly acid material can improve catalyst surface acidity and then reduce SO
2at CeO
2the adsorption and oxidation on surface, thus the sulfuration resistant performance improving catalyst; The heteropoly acid structure of similar basic zirconium phosphate prepared by simultaneously the present invention has very high heat endurance, under hot environment also can not with CeO
2structural interaction cause catalysqt deactivation, and then make catalyst have very high water resistant hot property.Experimental verification, catalyst is after over cure, hydrothermal treatment consists, and the property retention of catalyst is stablized, and the conversion ratio of NOx still keeps higher level.In addition, in preparation process, PO
4 3-react with zirconates the porous heteropoly acid material generating stratiform, this heteropoly acid material not only can improve the surface acidity of catalyst, and also can increase the specific area of catalyst due to its high-specific surface area, promotes catalyst for NH from two aspects
3adsorptivity, promote catalytic efficiency.Experimental verification, the conversion ratio of the NOx in 250 ~ 450 DEG C is higher, close to 100%.Meanwhile, catalyst n
2selective also higher, all more than 90%.In preparation process, the material selected is CeO
2or the soluble-salt of Ce, the soluble-salt of soluble phosphate and zirconium, uses CeO relative in existing preparation process
2, P
2o
5or Nb
2o
5, the cost of raw material reduces a lot, and therefore the cost of catalyst prod is lower.Method for preparing catalyst of the present invention is simple, and production cost is low, is convenient to industrialization, can be widely used in NO in exhaust gas from diesel vehicle and power plant, cement plant flue gas
xdenitration process.
[accompanying drawing explanation]
Fig. 1 a is the scanning electron microscope (SEM) photograph of catalyst under a kind of resolution ratio obtained in the experimental example 1 of the specific embodiment of the invention;
Fig. 1 b is the scanning electron microscope (SEM) photograph of catalyst under another kind of resolution ratio obtained in the experimental example 1 of the specific embodiment of the invention;
Fig. 2 a is the scanning electron microscope (SEM) photograph of catalyst under a kind of resolution ratio obtained in the experimental example 4 of the specific embodiment of the invention;
Fig. 2 b is the scanning electron microscope (SEM) photograph of catalyst under another kind of resolution ratio obtained in the experimental example 4 of the specific embodiment of the invention;
Fig. 3 a is the scanning electron microscope (SEM) photograph of catalyst under a kind of resolution ratio obtained in the experimental example 5 of the specific embodiment of the invention;
Fig. 3 b is the scanning electron microscope (SEM) photograph of catalyst under another kind of resolution ratio obtained in the experimental example 5 of the specific embodiment of the invention;
Fig. 4 a is the scanning electron microscope (SEM) photograph of catalyst under a kind of resolution ratio obtained in the experimental example 8 of the specific embodiment of the invention;
Fig. 4 b is the scanning electron microscope (SEM) photograph of catalyst under another kind of resolution ratio obtained in the experimental example 8 of the specific embodiment of the invention.
[detailed description of the invention]
Contrast accompanying drawing below in conjunction with detailed description of the invention the present invention is described in further details.
Catalyst of the present invention, with CeO
2based on, Zr
4+and PO
4 3-the heteropoly acid material of the porous of the stratiform formed is coated on CeO
2surface, by heteropoly acid material assistance CeO
2, make CeO
2give full play to the effect of active component, provide active oxygen to participate in catalytic reduction reaction, thus play the denitration of catalytic conversion NOx.Simple CeO
2for active component, because its surface acidity is very low, its denitration performance is very poor.And Surface coating has the CeO of heteropoly acid material
2, then its surface acidity is enhanced, and surface area is also increased dramatically, and therefore can effectively promote NH
3adsorptivity, utilize NH
3by the NO in waste gas
xsCR becomes N
2and water, promote catalytic efficiency.Meanwhile, this heteropoly acid material can improve catalyst surface acidity and then reduce SO
2at CeO
2the adsorption and oxidation on surface, thus the sulfuration resistant performance improving catalyst; The heteropoly acid structure of similar basic zirconium phosphate prepared by simultaneously the present invention has very high heat endurance, under hot environment also can not with CeO
2structural interaction, and then make catalyst have very high water resistant hot property.And determine by this Zr
4+and PO
4 3-the porous heteropoly acid material formed is as CeO
2auxiliary collaborative component, neither hold facile.In R&D process, also attempted SO
4 2-, Nb
2o
5h
2o, WO
3or MoO
3, but these compositions lead to the failure because of reasons different separately.Such as, when being used alone phosphoric acid as auxiliary element, phosphoric acid meeting and CeO
2interact and generate cerous phosphate, cause catalysqt deactivation.Again such as, Nb
2o
5h
2when O is as auxiliary element, easily in hot environment, become Nb
2o
5lose acid, make the catalyst obtained to be applicable to hot environment.As considered to use phosphoric acid and Nb
2o
5h
2o, then phosphoric acid is difficult to and Nb
2o
5reaction after mixing, but be easier to and CeO
2reaction generates cerous phosphate, causes catalysqt deactivation, then still can not address this problem.And WO
3and MoO
3same easy and active component CeO
2in hot environment, reaction generates cerium salt, causes catalysqt deactivation.Therefore, Zr is selected in the present invention
4+and PO
4 3-the porous heteropoly acid material formed is long-time research and development, determines to obtain after many-side test is feasible.
For making heteropoly acid material and CeO
2be attached together, heteropoly acid material and CeO
2carry out the mixing of atomic level, use infusion process by the surface of heteropoly acid species adsorbs at metal oxide, or use sol-gel process, by complexing agent, the soluble salt solutions of Ce is formed colloidal sol together with the complexing of heteropoly acid material, finally equal Kaolinite Preparation of Catalyst powder after super-dry, roasting.
In the present invention, the soluble-salt of the zirconium of use is Zr (NO
3)
45H
2o, ZrOCl
28H
2o, Zr (CH
3cO
2)
4, ZrCl
4or Zr (OH)
4.The soluble-salt of Ce is Ce (NO
3)
46H
2o, Ce (NO
3)
36H
2o, CeCl
37H
2o, Ce
2(C
2o
4)
310H
2o or (CH
3cO
2)
3ceKH
2o; Wherein, K represents positive integer.Soluble phosphate is (NH
4)
2hPO
4, or NH
4h
2pO
4, or (NH
4)
3pO
4, or (NH
4)
2hPO
4, or APP (NH
4, H)
n+ 2P
no
3n+1.
Arrange concrete experimental example to be as follows described:
Experimental example 1: adopt infusion process preparation.
1) a certain amount of CeO is got
2account for the cerium zirconium sosoloid powder of 80wt%, the amount chosen guarantees that the mass fraction that metal oxide accounts for obtained whole catalyst is 90%.Only CeO can be comprised in powder
2, why adulterate ZrO
2, be because doping ZrO
2after, can CeO be improved
2stability during catalytic reduction reaction.Similarly, also can doped with Al in metal-oxide powder
2o
3or SiO
2.
2) a certain amount of (NH is got
4)
2hPO
4and ZrOCl
28H
2o, the amount chosen ensures PO
4 3-+ Zr
4+the mass fraction of whole catalyst obtained after the heteropoly acid material formed accounts for is 10%, by Zr
4+with PO
4 3-1:1 is dissolved in deionized water in molar ratio, forms clear aqueous solution, the Zr in the aqueous solution
4+and PO
4 3-ion concentration sum be 1molL
-1.
3) by dipping mode by aqueous solution load in step 1) described in cerium zirconium sosoloid powder on.
4) powder is positioned over drying box and dries 12 hours, then smash to pieces, grind, at 500 DEG C, roasting 3 hours, obtains catalyst powder.This catalyst is designated as A-1.
Figure 1 shows that the scanning electron microscope sem figure of catalyst powder A-1, Fig. 1 a and Fig. 1 b represents the SEM figure under different multiples respectively.As we know from the figure, oxide particle surface is attached with loose structure material, and this loose structure is by PO
4 3-and Zr
4+the heteropoly acid material formed.Zr
4+and PO
4 3-form heteropoly acid material, both molar ratio range are 0.5 ~ 2, are preferably the mol ratio of the 1:1 in this experimental example.When both mol ratios are 1, the heteropoly acid structure of porous can be made for being similar to layer structure, making specific area reach largest optimization value.
Metal oxide (CeO in catalyst A-1
2+ ZrO
2) mass fraction be 90%, the mass fraction of heteropoly acid material is 10%, Zr in heteropoly acid material
4+and PO
4 3-mol ratio be 1.
Test the SCR performance of this catalyst.During test, the atmosphere configuration gas of simulation exhaust gas from diesel vehicle and power plant, cement plant flue gas, simulation distribution composition is O
2(5%), NO
x(500ppm), NH
3(500ppm), HO
2(5%), CO
2(20%), N
2balance, air speed is GHSV=30000h
– 1, gas flow: 1000mL/min.Before test, pretreatment is carried out to catalyst A-1 sample: with the speed of 10 DEG C/min at 10%O
2air-flow (N
2as carrier gas) in sample is heated to 500 DEG C, be incubated and be cooled to room temperature after 1 hour.During test, get catalyst 0.5ml, mix with the quartz sand of 1.5ml, load reactor, pass into simulation distribution and carry out catalytic reduction reaction, and regulate the temperature of course of reaction, heating rate is 10 DEG C/min, from room temperature to 500 DEG C.Measure the NO of reactor inlet
xcontent, NH
3the NO of content and reactor outlet
xcontent, NH
3content, thus calculate corresponding NO
xconversion ratio and N
2selective.Survey calculation the results are shown in Table 1.
The NO of catalyst
xconversion ratio is by formula
calculate, the N of catalyst
2selective by formula
calculate.
Vulcanizing treatment catalyst A-1: catalyst is loaded quartz ampoule, at 1000ppmSO
2under the atmosphere of+10% steam+air, at 400 DEG C, roasting 48 hours.Then the catalyst after roasting is smashed to pieces, ground, place.The SCR performance of the catalyst A-1 after test vulcanizing treatment, method of testing is same as above, and test result is in table 1.
Hydrothermal treatment consists catalyst A-1: catalyst is loaded quartz ampoule, under 800 DEG C of air atmospheres, roasting 100 hours, then smashs to pieces the catalyst after roasting, grinds, and places.The SCR performance of the catalyst A-1 after test water heat treatment, method of testing is same as above, and test result is in table 1.
Experimental example 2: identical with the preparation process of experimental example 1, difference is only: the difference of quality, the mass fraction making metal oxide account for obtained whole catalyst is 80%, and the mass fraction of the heteropoly acid material of porous is 20%.Zr in heteropoly acid material
4+and PO
4 3-mol ratio be still 1.Obtained catalyst is designated as A-2.
The SCR performance of detecting catalyst A-2, and vulcanizing treatment, the SCR performance after hydrothermal treatment consists.Method of testing is identical with experimental example 1, does not repeat at this.Measuring and calculation the results are shown in Table 1.
Experimental example 3: identical with the preparation process of experimental example 1, difference is only: the difference of quality, the mass fraction making metal oxide account for obtained whole catalyst is 70%, and the mass fraction of the heteropoly acid material of porous is 30%.Zr in heteropoly acid material
4+and PO
4 3-mol ratio be still 1.Obtained catalyst is designated as A-3.
The SCR performance of detecting catalyst A-3, and vulcanizing treatment, the SCR performance after hydrothermal treatment consists.Method of testing is identical with experimental example 1, does not repeat at this.Measuring and calculation the results are shown in Table 1.
Experimental example 4: identical with the preparation process of experimental example 1, difference is only: be added with promoter.Step 2) in, get a certain amount of (NH
4)
2hPO
4, ZrOCl
28H
2o and Na
2wO
42H
2o (WO
3soluble-salt), the amount chosen ensures PO
4 3-+ Zr
4++ MO
xthe mass fraction of whole catalyst obtained after the heteropoly acid material formed accounts for is 10%, by Zr
4+with PO
4 3-1:1 in molar ratio, (Zr
4++ PO
4 3-) and MO
xmol ratio be 3:1, be dissolved in deionized water, formed clear aqueous solution, the Zr in the aqueous solution
4+, PO
4 3-and MO
xion concentration sum be 1molL
-1.After adding promoter, obtained catalyst is designated as A-4.
Figure 2 shows that the scanning electron microscope sem figure of catalyst powder A-4, Fig. 2 a and Fig. 2 b represents the SEM figure under different multiples respectively.As we know from the figure, oxide particle surface is attached with loose structure material, and this loose structure is Zr
4+, PO
4 3-and MO
xlayered porous heteropoly acid material is formed in described mixed aqueous solution.Comparison diagram 2 and Fig. 1 known, after adding promoter, under the effect of promoter, cavernous structure material connects into a slice, form the porous heteropoly acid material of stratiform, thus make the loose structure of heteropoly acid material more stable, be more conducive to improving the stability of catalyst, (the thermal power plant's flue gas as high dirt) dust, sulfate etc. can be reduced in practical service environment further in the deposition of catalyst surface simultaneously.It should be noted that captax O
xexcept the WO for this experimental example
3outward, also can be MoO
3or H
2sO
4in one or more, corresponding the, soluble-salt is H
8n
2o
4w, H
2wO
4, MoO
3h
2o, H
8n
2o
4mo, Na
2moO
42H
2o, Na
2sO
4, (NH
4)
2sO
4or NH
4hSO
4.
The SCR performance of detecting catalyst A-4, and vulcanizing treatment, the SCR performance after hydrothermal treatment consists.Method of testing is identical with experimental example 1, does not repeat at this.Measuring and calculation the results are shown in Table 1.
Experimental example 5: adopt sol-gal process preparation.
1) a certain amount of Ce (NO is got
3)
46H
2o, the amount chosen guarantees metal oxide CeO in final obtained catalyst
2mass fraction be 95%.
2) a certain amount of Zr (NO is got
3)
45H
2o, (NH
4)
2hPO
4, deionized water Homogeneous phase mixing obtains settled solution, the amount chosen guarantees PO in final obtained catalyst
4 3-+ Zr
4+the mass fraction of the heteropoly acid material formed is 5%, by Zr
4+with PO
4 3-2:1 is dissolved in deionized water in molar ratio, forms clear aqueous solution, the Zr in the aqueous solution
4+and PO
4 3-ion concentration sum be 1molL
-1.
3) by step 1) and step 2) in solution mixing, add appropriate complexing agent citric acid, the gram-equivalent number of the citric acid added is 2 times of the gram-equivalent number sum of all metal ions in solution.
4) by step 3) solution 100 DEG C stir 3h namely obtain yellow foam gel.Gel obtains gel solids at 110 DEG C of dry 12h.
5) by gel solids 300 DEG C of heat treatments 1 hour, be warming up to 550 DEG C of roasting 3h and obtain catalyst powder.This catalyst is designated as B-1.
Figure 3 shows that the scanning electron microscope sem figure of catalyst powder B-1, Fig. 3 a and Fig. 3 b represents the SEM figure under different multiples respectively.As we know from the figure, oxide particle surface is attached with loose structure material, and this loose structure is by PO
4 3-and Zr
4+the heteropoly acid material formed.
Metal oxide (CeO in catalyst B-1
2) mass fraction be 95%, the mass fraction of heteropoly acid material is 5%, Zr in heteropoly acid material
4+and PO
4 3-mol ratio be 2.
The SCR performance of detecting catalyst B-1, and vulcanizing treatment, the SCR performance after hydrothermal treatment consists.Method of testing is identical with experimental example 1, does not repeat at this.Measuring and calculation the results are shown in Table 1.
Experimental example 6: identical with the preparation process of experimental example 5, difference is only: the difference of quality, the mass fraction making metal oxide account for obtained whole catalyst is 85%, and the mass fraction of the heteropoly acid material of porous is 15%.Zr in heteropoly acid material
4+and PO
4 3-mol ratio be still 2.Obtained catalyst is designated as B-2.
The SCR performance of detecting catalyst B-2, and vulcanizing treatment, the SCR performance after hydrothermal treatment consists.Method of testing is identical with experimental example 1, does not repeat at this.Measuring and calculation the results are shown in Table 1.
Experimental example 7: identical with the preparation process of experimental example 5, difference is only: the difference of quality, the mass fraction making metal oxide account for obtained whole catalyst is 75%, and the mass fraction of the heteropoly acid material of porous is 25%.Zr in heteropoly acid material
4+and PO
4 3-mol ratio be still 2.Obtained catalyst is designated as B-3.
The SCR performance of detecting catalyst B-3, and vulcanizing treatment, the SCR performance after hydrothermal treatment consists.Method of testing is identical with experimental example 1, does not repeat at this.Measuring and calculation the results are shown in Table 1.
Experimental example 8: identical with the preparation process of experimental example 5, difference is only: be added with promoter.Step 2) in, get a certain amount of (NH
4)
2hPO
4, ZrOCl
28H
2o and Na
2moO
42H
2o (MoO
3soluble-salt), the amount chosen ensures PO
4 3-+ Zr
4++ MO
xthe mass fraction of whole catalyst obtained after the heteropoly acid material formed accounts for is 5%, by Zr
4+with PO
4 3-2:1 in molar ratio, (Zr
4++ PO
4 3-) and MO
xmol ratio be 2:1, be dissolved in deionized water, formed clear aqueous solution, the Zr in the aqueous solution
4+, PO
4 3-and MO
xion concentration sum be 1molL
-1.After adding promoter, obtained catalyst is designated as B-4.
Figure 4 shows that the scanning electron microscope sem figure of catalyst powder B-4, Fig. 4 a and Fig. 4 b represents the SEM figure under different multiples respectively.As we know from the figure, oxide particle surface is attached with loose structure material, and this loose structure is Zr
4+, PO
4 3-and MO
xlayered porous heteropoly acid material is formed in described mixed aqueous solution.Comparison diagram 4 and Fig. 3 known, add after promoter, under the effect of promoter, cavernous structure material connects into a slice, forms the porous heteropoly acid material of stratiform, thus makes the loose structure of heteropoly acid material more stable, is more conducive to the stability improving catalyst.It should be noted that captax O
xexcept the MoO for this experimental example
3outward, also can be WO
3or H
2sO
4in one or more, corresponding the, soluble-salt is H
8n
2o
4w, Na
2wO
42H
2o, H
2wO
4, MoO
3h
2o, H
8n
2o
4mo, Na
2sO
4, (NH
4)
2sO
4or NH
4hSO
4.
The SCR performance of detecting catalyst B-4, and vulcanizing treatment, the SCR performance of hydrothermal treatment consists.Method of testing is identical with experimental example 1, does not repeat at this.Measuring and calculation the results are shown in Table 1.
Table 1
According to the data of table 1, the A group catalyst that infusion process obtains and the B group catalyst that sol-gal process obtains, its initial NO
xconversion ratio/N
2selective all higher in temperature window (250 DEG C ~ 450 DEG C), can more than 90% be reached, even close to 100%.And respectively organize vulcanizing treatment, after hydrothermal treatment consists and heat treatment, although its transformation efficiency and selectively to decrease, but unlikely inactivation is 0, still have close to the transformation efficiency of 70% and the selectivity parameter of 90%, still higher, still have certain use value, effect is still better.Therefore known, the water resistant heat ageing of each group catalyst, the performance of sulfuration resistant is comparatively strong, and heat endurance is also better.
Above content is in conjunction with concrete preferred embodiment further description made for the present invention, can not assert that specific embodiment of the invention is confined to these explanations.For general technical staff of the technical field of the invention, make some substituting or obvious modification without departing from the inventive concept of the premise, and performance or purposes identical, all should be considered as belonging to protection scope of the present invention.
Claims (10)
1. a CeO
2the preparation method of base SCR catalyst, is characterized in that: comprise the following steps:
1) get appropriate metal-oxide powder, described metal oxide at least comprises CeO
2;
2) soluble-salt getting appropriate soluble phosphate and zirconium makes mixed aqueous solution, Zr in described mixed aqueous solution
4+and PO
4 3-mol ratio be 0.5 ~ 2, the Zr in described mixed aqueous solution
4+and PO
4 3-ion concentration sum be 0.1 ~ 5mol/L; Described Zr
4+and PO
4 3-the heteropoly acid material of porous is formed in described mixed aqueous solution;
3) by step 1) in metal-oxide powder and step 2) in mixed aqueous solution adopt infusion process mix, make described heteropoly acid material be attached to described metal oxide surface;
4) by step 3) mixture that obtains at 80 ~ 120 DEG C of dry process 1 ~ 10h, then roasting 1 ~ 5 hour at 450 ~ 700 DEG C, obtained catalyst powder;
Wherein, in the quality of described metal-oxide powder, the quality of the described aqueous solution and the described aqueous solution, the concentration of each ion makes the mass fraction of metal oxide in final obtained catalyst be 60% ~ 95%, and the mass fraction of the heteropoly acid material of described porous is 5% ~ 40%.
2. CeO according to claim 1
2the preparation method of base SCR catalyst, is characterized in that: described step 2) in also comprise and add the step of promoter: in described mixed aqueous solution, add MO
xsoluble-salt, described MO
xfor WO
3, MoO
3in one or more, (Zr in mixed solution
4++ PO
4 3-) and MO
xmol ratio be 2 ~ 10, the Zr in mixed aqueous solution
4+, PO
4 3-and MO
xion concentration sum be 0.1 ~ 5mol/L, by Zr
4+, PO
4 3-and MO
xlayered porous heteropoly acid material is formed in described mixed aqueous solution.
3. CeO according to claim 1
2the preparation method of base SCR catalyst, is characterized in that: described step 1) in, metal-oxide powder also comprises ZrO
2, Al
2o
3in one or more.
4. a CeO
2the preparation method of base SCR catalyst, is characterized in that: comprise the following steps:
1) get appropriate metal salt solution, described metal salt solution at least comprises the soluble salt solutions of Ce, and Ce
4+ion concentration be 0.1 ~ 5mol/L;
2) soluble-salt getting appropriate soluble phosphate and zirconium makes mixed aqueous solution, Zr in described mixed aqueous solution
4+and PO
4 3-mol ratio be 0.5 ~ 2, the Zr of described mixed aqueous solution
4+and PO
4 3-ion concentration sum be 0.1 ~ 5mol/L; Described Zr
4+and PO
4 3-the heteropoly acid material of porous is formed in described mixed aqueous solution;
3) by step 1) in solution and step 2) in aqueous solution, add appropriate complexing agent, make described heteropoly acid material and described Ce
4+complexing together, is stirred, is obtained solution; Wherein, the gram-equivalent number of complexing agent is 1 ~ 5 times of the gram-equivalent number sum of all metal ions in solution;
4) by step 3) solution that obtains carries out continuous heating stirring at 100 ~ 120 DEG C, evaporate to dryness, forms gel; Gel is placed in drying box and dries 12 hours in 80 ~ 150 DEG C;
5) by step 4) gel solids that obtains or powder smash to pieces, grinding, roasting 0.5 ~ 3 hour at 200 ~ 350 DEG C, and then roasting 1 ~ 5 hour at 450 ~ 700 DEG C, obtains catalyst powder;
Wherein, the quality of the soluble salt solutions of described Ce and Ce
4+concentration, Zr in the quality of the described aqueous solution and the described aqueous solution
4+, PO
4 3-concentration make the mass fraction of metal oxide in final obtained catalyst be 60% ~ 95%, the mass fraction of the heteropoly acid material of described porous is 5% ~ 40%.
5. CeO according to claim 4
2the preparation method of base SCR catalyst, is characterized in that: described step 2) in also comprise and add the step of promoter: in described mixed aqueous solution, add MO
xsoluble-salt, described MO
xfor WO
3, MoO
3, H
2sO
4in one or more, (Zr in mixed solution
4++ PO
4 3-) and MO
xmol ratio be 2 ~ 10, by Zr
4+, PO
4 3-and MO
xlayered porous heteropoly acid material is formed in described mixed aqueous solution.
6. CeO according to claim 4
2the preparation method of base SCR catalyst, is characterized in that: described step 3) complexing agent is citric acid.
7. a CeO
2base SCR catalyst, is characterized in that: comprise metal oxide and be attached to metal oxide surface by Zr
4+-and PO
4 3the heteropoly acid material of the porous formed; Wherein, described metal oxide comprises CeO
2, the quality of metal oxide accounts for 60% ~ 95% of whole catalyst quality; Zr in described heteropoly acid material
4+and PO
4 3-mol ratio be 0.5 ~ 2, the quality of described heteropoly acid material accounts for 5% ~ 40% of whole catalyst quality.
8. CeO according to claim 7
2base SCR catalyst, is characterized in that: also comprise promoter in described heteropoly acid material, and described promoter is WO
3, MoO
3in one or more.
9. CeO according to claim 7
2base SCR catalyst, is characterized in that: Zr in described heteropoly acid material
4+and PO
4 3-mol ratio be 1:1.
10. CeO according to claim 7
2base SCR catalyst, is characterized in that: described metal oxide also comprises ZrO
2, Al
2o
3in one or more.
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