CN101992089A - Three-dimensional ordered porous-mesoporous iron-based perovskite oxide catalyst and preparation method thereof - Google Patents
Three-dimensional ordered porous-mesoporous iron-based perovskite oxide catalyst and preparation method thereof Download PDFInfo
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Abstract
The invention provides an iron-based perovskite oxide catalyst for use in purification of carbon smoke particles emitted from diesel vehicles and a preparation method thereof. The catalyst is a three-dimensional ordered porous-mesoporous iron-based perovskite oxide consisting of more than two elements from rear earth metals, transitional metals, alkali metal and/or alkaline earth metals as active components, wherein the pores of the oxide are formed into a uniform and ordered verse opal structure; and the mesopores are formed into a worm-like structure. In the invention, a carbon temperature supporting process is adopted, carboxyl-modified microspheres are used as pore temperatures, a surfactant is a mesoporous template, a firm carbon template can be formed by roasting in an inert gas, the supporting porous-mesoprous structure is free from collapse, and when roasted in the air, a perovskite structure can be formed. The catalyst of the invention can contact with carbon smoke particles effectively and is favorable for the conversion of small particles and gas molecules. Under a condition that the catalyst is in loose contact with the carbon smoke particles, the minimum combustion peak temperature is 396 DEG C, and the activity of the catalyst is equivalent to that of a noble metal catalyst.
Description
Technical field
The present invention relates to emission of diesel engine soot particulate purification techniques, specifically relate to a kind of emission of diesel engine carbon soot particles and purify, belong to catalyst technology and field of environment protection with three-dimensional ordered macroporous-mesoporous iron-based perovskite oxide Catalysts and its preparation method.
Background technology
Diesel engine has distinguishing features such as thermal efficiency height, good economy performance, so current mobility car diesel oil degree improves constantly.But the soot particulate of diesel vehicle (PM) discharge capacity is 30～80 times of gasoline car, wherein the particle diameter of 70% soot particulate is less than 0.3 μ m, and be adsorbed with multiple organic compound, can be after being sucked by human body deeply to alveolar, and be difficult for excreting, and particle is very big to the harm of human body as the carrier of strong carcinogenic substance BaP, nitro condensed-nuclei aromatics.Therefore, reducing the aerial discharge capacity of soot particulate is the top priority of exhaust gas from diesel vehicle emission treatment.
Utilizing particulate supplementary set device is to reduce the topmost exhaust aftertreatment method of emission of diesel engine carbon soot particles, and the principle of its application is to make carbon soot particles be attracted to the surface of filter medium in filter process and play catharsis.Yet, if the particulate that is collected on the filter is not removed in time, will cause the diesel vehicle back pressure to increase, thereby influence the performance of diesel vehicle.Therefore, the difficult point that this filter is actual when using is regeneration, and the soot particulate of accumulation is regularly removed, and makes filter be able to continuous operation.The renovation process of filter adopts catalytic oxidation more, its key is that the oxidation catalyst that is carried on the filter should have good low-temperature burning activity, the feasible carbon soot particles that is deposited in the filter can burn under lower delivery temperature and remove, thereby reduce the discharge capacity of soot in the exhaust gas from diesel vehicle effectively, engine also is unlikely to because the carbon soot particles obstruction causes back pressure to increase and stops working.Diesel engine is in working order the time, and the oxidate temperature of carbon soot particles is up to 550～600 ℃, and the delivery temperature of diesel vehicle is 180～400 ℃.Therefore, improve the catalytic activity of the carbon soot particles catalyst for clarifying of exhaust gas from diesel vehicle discharging, reducing the ignition temperature of carbon soot particles, thereby soot particulate filter (DPF) can be used continuously, is to reduce the most direct effective method of diesel emission soot particulate.
Since the carbon soot particles in the exhaust gas from diesel vehicle is eliminated reaction be a gas (tail gas) Gu-(carbon soot particles) Gu-the deep reaction process of (catalyst) three-phase complexity, therefore activity of such catalysts is not only closely related with the redox property of oxidation catalyst itself, also relevant with the exposure level of catalyst and carbon soot particles simultaneously.Because the diameter of diesel engine carbon black granules is big (usually greater than 25nm) generally, and the aperture of typical catalyst is usually less than 10nm, carbon black granules is difficult to enter the inside, duct of catalyst, can only contact with its outer surface, causes the effective active surface area of catalyst to reduce.Therefore, the catalyst that is used to eliminate the diesel vehicle soot particle at first will have extraordinary redox property, and next has bigger aperture and orderly pore passage structure to improve the utilization rate of the inner duct of catalyst active surface area.
US 2003/01004932 discloses a kind of catalyst that is used for diesel vehicle exhaust carbon-smoke particle catalytic combustion, and this catalyst comprises attached to Pt on the Zr-W oxide and Pd noble metal.CN1554859A discloses and has a kind ofly removed the method for soot particulate with filter and cleaning catalyst, and that uses is Pt-V
2O
5/ Al
2O
3Noble metal catalyst.Therefore these noble metal catalysts have extraordinary catalytic activity to carbon soot particles, but it involves great expense, and have limited its industrial application, develop cheap non-precious metal catalyst and purify carbon soot particles and have very important significance.
Perovskite oxide is a kind of ABO of having
3The composite oxides of type perovskite structure have good redox property.CN 1139428C discloses a kind of perovskite series catalyst that can be used for the burning of catalyzed diesel tail gas carbon soot particles, adopt this type of catalyst that combustion temperature of soot is obviously reduced, but the ignition temperature of carbon soot particles is still more than 400 ℃, so its catalytic performance can't satisfy the requirement of diesel car tail gas refining fully.
CN1743067A discloses the application of a kind of perovskite series nano superfine micro oxide catalyst in catalyzed diesel exhaust carbon-smoke particle burning.Cobalt-based, manganese base and iron-based perovskite oxide are to use three kinds of maximum catalyst, and wherein the redox property of cobalt-based is the strongest, therefore the cobalt-based perovskite catalyst are used for the carbon soot particles burning and have best catalytic effect.In addition, the redox active of perovskite oxide has substantial connection with the element, the replacement amount that replace A position ion.The cobalt-based perovskite series nano superfine micro oxide catalyst that in the document K is partly mixed is used for the carbon soot particles burning, has obtained catalytic effect preferably.But because the aperture of these catalyst is all below 10nm, the soot particulate average grain diameter is difficult to enter in the catalyst duct and reacts greater than 25nm, causes a large amount of active surface area in the inner duct of catalyst to utilize, thereby catalytic activity is reduced.
Three-dimensional ordered macroporous-mesoporous (3DOM/m) material, have the diversity characteristics such as (simple oxide, composite oxides and solid solution etc.) that uniform sequential macropore duct (more than the 50nm), the mesopore orbit structure of enriching and skeleton are formed as a class new material, thereby paid close attention to widely.The catalyst combustion reaction that the 3DOM/m catalyst is used for carbon soot particles, on the one hand uniform sequential macropore duct helps carbon soot particles and enters in the catalyst duct and react, thereby the raising catalyst contacts with carbon soot particles, Feng Fu mesopore orbit can improve the specific area of catalyst on the other hand, and helps the catalyzed conversion of granule and gas molecule.
At present, colloidal crystal template (CCT) method is to prepare the most frequently used method of 3DOM/m oxide.Generally comprise following steps: at first, prepare monodispersed colloid micro ball and pile up and be assembled into orderly colloidal crystal template, mesoporous template surface activating agent is mixed in the precursor solution; Then, presoma is filled into the microsphere template gap, and it is carried out processing such as thermal transition, make it in the die clearance, be converted into solid skeletal; At last, remove template, obtain corresponding 3DOM/m oxide by methods such as roasting or dissolvings.
Present a large amount of simple oxide such as SiO
2, Al
2O
3, TiO
2Deng all successfully having prepared three-dimensional ordered macroporous-meso-hole structure, and technology of preparing is all very ripe.But because the perovskite composite oxide complex structure, can cause caving in of duct during according to traditional CCT method roasting, be difficult to obtain having the composite oxides of foramen magnum-mesoporous pore passage structure.
In view of above prior art situation; manufacture perovskite composite oxides catalyst with three-dimensional ordered macroporous-meso-hole structure; and use it for the catalytic combustion of emission of diesel engine soot particulate; for improving contacting of catalyst and carbon soot particles; reduce the ignition temperature of carbon soot particles; thereby reduce the discharging of diesel vehicle exhaust carbon-smoke particle, have very important basic research meaning and environmental protection meaning.
Summary of the invention
Technical problem underlying solved by the invention is to provide a kind of 3DOM/m iron-based perovskite composite oxides catalyst, this catalyst has extraordinary effect to carbon soot particles catalytic combustion in the diesel emission, the ignition temperature of carbon soot particles is significantly reduced, and this catalyst does not contain noble metal, reduces the catalyst cost when improving catalytic activity.
The present invention also provides above-mentioned 3DOM/m iron-based perovskite composite oxides Preparation of catalysts method, utilize the carbon template to prop up staying, prepare have higher catalytic activity, the perovskite composite oxides catalyst with three-dimensional ordered macroporous-meso-hole structure of low production cost.
The present invention at first provides a kind of emission of diesel engine carbon soot particles to purify with iron-based perovskite oxide catalyst, it is as active component and have the Ca-Ti ore type composite metal oxide of three-dimensional ordered macroporous-meso-hole structure by the two or more element in rare earth metal, transition metal, alkali metal and/or the alkaline-earth metal, the macropore of this composite metal oxide is uniform sequential counter opal structure, and mesoporous is vermicular texture.More particularly, the macropore diameter of this composite metal oxide is more than 200nm, and the duct is uniform sequential, and mesoporous is vermicular texture, and the aperture is between 2-10nm.
The present invention is to provide a kind of 3DOM/m iron-based perovskite composite oxides catalyst, has three-dimensional ordered macroporous-meso-hole structure, its unique pore passage structure helps carbon soot particles and enters in the hole from all directions, reduced the diffusional resistance of carbon soot particles, contact with the effective of carbon soot particles thereby improved catalyst, catalytic activity improves greatly.
According to preferred specific embodiments of the present invention, the chemical composition of perovskite oxide catalyst of the present invention is Ln
1-xA
xBO
3, and x=0～0.3, wherein Ln is a rare-earth metal La; A is alkaline-earth metal Ca; B is a transition-metal Fe.
According to specific embodiments of the present invention, iron-based perovskite oxide catalyst of the present invention is that the precursor solution that will contain active component floods, obtains through after the high-temperature roasting then colloidal crystal template.
The present invention also provides above-mentioned iron-based perovskite composite oxides Preparation of catalysts method, this method mainly is that a kind of carbon template is propped up staying, with carboxy-modified microballoon is the macropore template, with surfactant is mesoporous template, roasting under inert gas, and the group that contains sp2 hydridization carbon atom can change into a kind of firm carbon structure, supporting macropore and meso-hole structure does not cave in when high-temperature roasting, in air, during roasting, agraphitic carbon can be removed then, and form perovskite structure.Particularly, iron-based perovskite composite oxides Preparation of catalysts method of the present invention may further comprise the steps:
The nitrate that will contain active component is according to stoichiometric proportion La: Ca: Fe=1-x: x: 1 ratio is mixed and is dissolved in the organic complex agent solution, is mixed with the precursor solution of catalyst, and wherein organic complexing agent is ethylene glycol or citric acid;
Mesoporous template surface activating agent is dissolved in hydrochloric acid or the salpeter solution, join after mixing in the precursor solution of catalyst, wherein surfactant is three block non-ionic surface active agent Brij-56 or P123, the consumption of this surfactant in precursor solution is 0.1～2wt%, preferred 0.1～1wt%;
Flood colloidal crystal template with precursor solution, after the suction filtration drying, after for example template is removed in high-temperature roasting under the different atmosphere of air etc. at inert gas, oxygen-containing gas, obtain three-dimensional ordered macroporous-mesoporous iron-based perovskite composite metal oxide.
According to specific embodiments of the present invention, in the complex catalyst precursor liquid solution of described nitrate, organic complexing agent and the surfactant that contains active component and hydrochloric acid or salpeter solution, the total concentration of metal ion is 1～5mol/L.
According to specific embodiments of the present invention, among the present invention, described roasting mode is as follows:
At first in inert gas, be warming up to 500～800 ℃, and constant temperature 3～6h, reduce to room temperature after, in air atmosphere, be warming up to 500～800 ℃, and constant temperature 3～6h.Wherein, the flow velocity of inert gas, air is 50～100ml/min, and heating rate is 1～5 ℃/min.Using earlier the inert gas roasting, is that carboxyl and the surfactant in the presoma with microsphere surface is converted into hard agraphitic carbon, supports macroporous structure and does not cave in when high-temperature roasting.Air roasting is used in the back, is that the agraphitic carbon that will generate is removed, and active component is formed perovskite structure.
According to specific embodiments of the present invention, colloidal crystal template of the present invention is carboxy-modified polymethyl methacrylate (PMMA) microsphere template, both can be the finished product that is purchased, and also can prepare voluntarily.Preferably, the preparation of colloidal crystal template can comprise following step:
Under nitrogen protection and condensed water circulation cooling, acetone and redistilled water are mixed, and be preheated to 60～90 ℃ with water-bath, add main monomer methyl methacrylate and function monomer acrylic acid, continue to be heated to 60～90 ℃ with water-bath;
Under nitrogen protection and condensed water circulation cooling, adding has been preheating to 60～90 ℃ initiator solution, continues to stir, and behind reaction 1～5h, obtains monodispersed carboxy-modified polymethyl methacrylate (c-PMMA), and its surface has carboxyl functional group;
With the rotating speed centrifugal treating 2～10h of microballoon emulsion with 1000～5000r/min, drying obtains closelypacked colloidal crystal template under the room temperature.
The present invention also provides a kind of reduction diesel vehicle exhaust carbon-smoke particle burning method of temperature, and this method comprises that the carbon soot particles that makes in the exhaust gas from diesel vehicle reacts under the loose condition that contacts with catalyst of the present invention.
The present invention also provides a kind of method of purification of diesel car emission of carbon smoke particle, and it comprises that employing oxide catalyst of the present invention carries out catalytic combustion to the soot particulate of emission of diesel engine, thereby reaches the purpose of purifying tail gas of diesel vehicles.
Perovskite oxide catalyst provided by the invention has three-dimensional ordered macroporous-meso-hole structure, its uniform sequential macropore pore passage structure can promote carbon soot particles to enter into inside, duct and spread smoothly, carbon soot particles is fully contacted with the inner surface of catalyst, abundant mesopore orbit has improved the specific area of catalyst, help effective conversion of granule and gas molecule, thereby improve the catalytic activity of catalyst.3DOM/m iron-based perovskite composite oxides catalyst of the present invention is used for the purification of emission of diesel engine soot particulate, the combustion temperature of soot of emission of diesel engine is lowered greatly.Experimental result shows, under the loose condition that contacts of catalyst and carbon soot particles, the burning peak temperature of carbon soot particles can be reduced to below 400 ℃, reached the temperature range of diesel engine truck exhaust, suitable with noble metal catalyst, and the highest active catalyst makes the burning peak temperature of carbon soot particles be reduced to 396 ℃ especially.The present invention further provides a kind of method that reduces the soot particulate ignition temperature of emission of diesel engine, this method comprises soot particulate and 3DOM/m iron-based perovskite composite oxides of the present invention, for example La that makes emission of diesel engine
0.8Ca
0.2FeO
3Catalytic combustion carbon soot particles under the condition of loose contact, thus make ignition temperature reach the temperature range of exhaust gas from diesel vehicle discharging.
In a word, the invention provides a kind of new method and successfully prepared 3DOM/m iron-based perovskite composite oxides catalyst, and the catalytic combustion that is used for the emission of diesel engine carbon soot particles has very high activity, do not contain any noble metal composition in this catalyst, greatly reduce the cost of catalyst, and method for preparing catalyst provided by the present invention is simple, is fit to large-scale industrial production.Enforcement of the present invention has very important basic research meaning and actual environment protection significance for the improvement of exhaust gas from diesel vehicle.
Description of drawings
Fig. 1 is the SEM photo of the c-PMMA colloidal crystal template of the present invention's preparation.
Fig. 2 is the 3DOM/m La of the present invention's preparation
1-xCa
xFeO
3The SEM photo of composite oxides.Wherein, figure A.LaFeO
3Figure B.La
0.95Ca
0.05FeO
3Figure C.La
0.9Ca
0.1FeO
3Figure D.La
0.85Ca
0.15FeO
3
Fig. 3 a and Fig. 3 b are the 3DOM/m LaFeO of the present invention's preparation
3The TEM photo.
Fig. 4 a～Fig. 4 d is the 3DOM/m LaFeO of the present invention with different additive and the preparation of different impregnation method
3The SEM photo.Wherein, Fig. 4 a. additive is a methyl alcohol; Fig. 4 b. additive is a hydrochloric acid; Fig. 4 c. additive is a nitric acid; Fig. 4 d. two steps dipping.
Fig. 5 is the 3DOM/m La of the present invention's preparation
1-xCa
xFeO
3XRD diffraction pattern (x=0,0.05,0.1,0.15,0.2,0.25,0.3).
Fig. 6 is the 3DOM/m La of the present invention's preparation
1-xCa
xFeO
3FT-IR figure (x=0,0.05,0.1,0.15,0.2,0.25,0.3).
Fig. 7 is the 3DOM La of carbon black granules in the present invention's preparation
1-xCa
xFeO
3Generate CO when burning on the catalyst
2Concentration curve (x=0,0.05,0.1,0.15,0.2,0.25,0.3).
The specific embodiment
Further specify realization of the present invention and the beneficial effect that is had below in conjunction with accompanying drawing, but therefore the present invention is not subjected to any restriction.
The evaluation method of catalyst activity
Adopt atmospheric fixed bed microreactor apparatus evaluate catalysts to eliminate the catalytic combustion activity of carbon black pellet in the diesel engine vent gas.Reactor is the quartz ampoule of internal diameter 6mm, the temperature reaction of automatic temperature control instrument control program, and programming rate is 2 ℃/min.Test the carbon black pellet in the simulation diesel engine vent gas of selecting the production of Degussa company for use.The biased sample that takes by weighing 110mg catalyst and carbon black pellet (mass ratio 10: 1) is in ethanol, and ultrasonic dispersion 3min is filled in the constant temperature zone of reaction tube after the drying, and both contacts are between between loose contact and tight the contact.Reacting gas consists of: 0.2%NO, 5%O
2(volume ratio), all the other are He, total gas flow rate is 50ml/min.Reaction end gas is analyzed on the SP-3420 type gas chromatograph that Beijing Analytical Instrument Factory produces.Catalyst performance adopts T
10, T
50, T
90And S
m CO2Estimate, promptly represent respectively the carbon black burning transform 10%, 50% and 90% o'clock temperature and reaction temperature be T
m(CO in the reaction end gas
2Reaction temperature when concentration reaches maximum) generates CO the time
2Selectivity, S wherein
m CO2=[CO
2]
Out/ ([CO
2]
Out+ [CO]
Out) * 100% is in the formula: [CO
2]
Out[CO]
OutBe that reaction temperature is T
mThe time reaction end gas in CO
2With CO concentration.
The preparation method of embodiment 1 colloidal crystal template
In the present embodiment, prepare colloidal crystal template in accordance with the following methods:
(1) adopt improved emulsifier-free emulsion polymerization method to prepare monodispersed c-PMMA microballoon
50ml acetone and 150ml deionized water be added to agitator, reflux condensing tube, temperature are housed take into account N
2In the 1000ml four-hole boiling flask of tracheae, logical N
2Vacuumize, adding volume ratio is 25: 1 MMA and AA (two kinds of monomers are all refining through decompression distillation), and is heated to 70 ℃.Take by weighing initator 0.27g KPS and 0.45gAIBN simultaneously and be dissolved in the 150ml water, and add in the four-hole boiling flask after being heated to 70 ℃.N
2Protection naturally cools to room temperature after reacting 2h down under stirring, ultrasonic processing 0.5h, suction filtration obtain the c-PMMA polymer microballoon.
(2) adopt the centrifugal deposition legal system to be equipped with colloidal crystal template
The c-PMMA microballoon is placed centrifuge tube, and the centrifugal 10h of 3000r/min rotating speed discards supernatant liquor, obtains closelypacked modified PMMA colloidal crystal template after the drying at room temperature.Fig. 1 is the SEM photo of this colloidal crystal template.
Embodiment 23DOM/m LaFeO
3Oxide catalyst
Take by weighing 16.24g La (NO by stoichiometric proportion
3)
36H
2O and 15.15g Fe (NO
3)
29H
2O is dissolved in the 10ml ethylene glycol, and magnetic agitation 2h gets transparent and homogeneous solution, promptly obtains the precursor solution of catalyst.Simultaneously 0.25g Brij-56 is dissolved in the 5ml hydrochloric acid solution, joins in the precursor solution behind the magnetic agitation 2h, and go in the 25ml volumetric flask, it is 25ml that the spent glycol constant volume makes overall solution volume.With the dried c-PMMA colloidal crystal template of this solution impregnation 3g 10h, to be impregnated fully after, unnecessary precursor solution suction filtration is removed, then template is placed the vacuum drying chamber dried overnight.At last it earlier is warming up to 700 ℃ of roastings in argon gas atmosphere, and constant temperature 4h, reduce to room temperature after, in air atmosphere, be warming up to 700 ℃, and constant temperature 4h carries out roasting, obtain 3DOM LaFeO
3Oxide catalyst.Wherein the flow velocity of argon gas, air is 80ml/min, and heating rate is 1 ℃/min.
Picture A among Fig. 2 is the 3DOM/m LaFeO of this examples preparation
3The SEM photo of oxide catalyst, Fig. 3 a and Fig. 3 b are 3DOM/m LaFeO
3The TEM photo of oxide catalyst.As can be seen from Figure, be the macropore template with c-PMMA in the present embodiment, with Brij-56 the 3DOM/m LaFeO of mesoporous template preparation
3Have regular three-dimensional ordered macroporous structure, average pore size is about 300nm, and the duct is uniform sequential; Mesoporous is vermicular texture, and average pore size is about 5nm.The 3DOM/m LaFeO of present embodiment preparation
3X ray diffracting spectrum and infrared spectrum please respectively referring to Fig. 5, shown in Figure 6, its result shows the 3DOM/m LaFeO of present embodiment preparation
3Has perovskite structure.
Surfactant is dissolved in respectively in methyl alcohol, hydrochloric acid and the nitric acid, and other preparation conditions and preparation procedure prepare 3DOM/m LaFeO with embodiment 2
3Three kinds of catalyst of embodiment preparation are denoted as S-methyl alcohol respectively, and S-hydrochloric acid and S-nitric acid, its SEM photo is respectively as Fig. 4 a, Fig. 4 b, and shown in Fig. 4 c, the BET specific area is as shown in table 1.As seen from the figure, when three kinds of solvents are additive, can form regular macroporous structure.But the specific area minimum (35.56m of S-methyl alcohol as shown in Table 1,
2/ g), mainly be because methyl alcohol is unfavorable for the self assembly of surfactant, therefore can cause unordered mesoporous generation, thereby cause specific area to diminish.Wherein, the specific area maximum (44.63m of S-hydrochloric acid
2/ g), more help the self assembly of surfactant.
The 3DOM/m LaFeO of table 1 different additive preparation
3The BET specific area
| Additive | BET specific area/m 2/g |
| Methyl alcohol | 35.56 |
| Hydrochloric acid | 44.63 |
| Nitric acid | 42.21 |
Embodiment 4 investigates the influence of different impregnation methods
Adopt a step infusion process and two step infusion processes presoma to be impregnated in the space of micro polymer ball template respectively, other preparation conditions prepare 3DOM/m LaFeO with embodiment 2
3One step infusion process is dipping method among the embodiment 2, join surfactant B rij-56 in the precursor solution after, impregnated polymer template together again.Two step infusion processes are elder generation with surfactant B rij-56 impregnated polymer template, form mixture, flood the mixture of surfactant and polymer template then with precursor solution.Two kinds of catalyst of embodiment preparation are denoted as one step and two steps of S-of S-respectively.Fig. 4 b and Fig. 4 d SEM picture that S-one goes on foot and S-two goes on foot respectively.As seen from the figure, the macroporous structure that adopts a step infusion process to form is regular in order, and does not have obvious defects.Obvious defects can appear in the macroporous structure that adopts two step infusion processes to form, and the phenomenon of caving in occurs.This mainly is because when adopting two to go on foot infusion process, surfactant can stop up the outer surface of polymer template, makes precursor solution can't enter its internal voids fully, causes filling rate to reduce, thereby causes the phenomenon of caving in.
Comparative Examples 1 nano particle LaFeO
3Oxide catalyst
Adopt the citric acid complex firing method to prepare nanometer LaFeO
3Perovskite oxide (is called for short Nano-LaFeO
3) sample as a comparison.Concrete grammar comprises: press stoichiometric proportion La: Fe: citric acid=1: 1: 2 takes by weighing La (NO
3)
36H
2O, Fe (NO
3)
26H
2O and complexing agent citric acid are dissolved in them in the deionized water, mix.Mixed solution is moved into porcelain evaporating dishes, and heating is also constantly stirred, and makes its drying and burning obtain catalyst precursor, places 120 ℃ of dried overnight of drying box, places porcelain crucible at 800 ℃ of roasting 6h then, promptly obtains Nano-LaFeO
3Catalyst.
The 3DOM/m LaFeO of evaluation method according to above-mentioned catalyst activity to preparing in embodiment 2, the Comparative Examples 1
3And Nano-LaFeO
3Estimate, wherein 3DOM LaFeO
3The activity rating result (wherein ordinate is CO as shown in Figure 7
2Concentration, abscissa are reaction temperature), above-mentioned activity of such catalysts evaluating data sees Table 2.
With the loose condition that contacts of carbon soot particles under, 3DOM/m LaFeO
3Peak temperature (the T of catalyzed carbon smoke particle burning
50) be 417 ℃, with Nano-LaFeO
3Compare its T
50108 ℃ have been reduced, CO
2Selectivity also increase.Therefore, for the catalytic combustion of carbon soot particles, 3DOM/m LaFeO
3Catalytic activity be higher than Nano-LaFeO
3
Table 23DOM/m LaFeO
3And Nano-LaFeO
3The activity of such catalysts evaluation result
| Catalyst | T 10/℃ | T 50/℃ | T 90/℃ | S CO2 m/％ |
| Nano-LaFeO 3 | 378 | 525 | 579 | 80.0 |
| 3DOM/m?LaFeO 3 | 332 | 417 | 455 | 90.8 |
Embodiment 53DOM/m La
1-xCa
xFeO
3(x=0.05-0.3) oxide catalyst
Preparation condition and preparation procedure just change the doping of Ca with embodiment 2, make Ca and the atomic molar ratio of Fe be respectively 0.05,0.1,0.15,0.2,0.25,0.3.
The 3DOM/m La of embodiment preparation
1-xCa
xFeO
3X ray diffracting spectrum as shown in Figure 5, its result shows the 3DOM/m La of present embodiment preparation
1-xCa
xFeO
3Has perovskite structure; Picture C among Fig. 2 is the 3DOM/m La of this examples preparation
0.9Ca
0.1FeO
3The SEM photo of oxide catalyst.By in the photo as can be seen, the 3DOM/m La for preparing in the present embodiment
0.9Ca
0.1FeO
3Oxide catalyst has regular three-dimensional ordered macroporous structure, and average pore size is about 300nm, and the duct is uniform sequential.
Fig. 6 is 3DOM/m La
1-xCa
xFeO
3FT-IR result.As seen from the figure, all products are belonging to ABO
3600 and 400cm of thing phase
-1Near infrared absorption peak appears, show to have formed perovskite structure that this is consistent with XRD result.
The 3DOM/m La of evaluation method according to above-mentioned catalyst activity to the present invention is prepared
1-xCa
xFeO
3Catalyst carries out activity rating, and the gained activity the results are shown in Table 3 and Fig. 7.
Table 33DOM/m La
1-xCa
xFeO
3The activity of such catalysts evaluation result
By table 3 and Fig. 7 data as can be seen, when not using catalyst, the ignition temperature height of carbon soot particles, its T
50Be 585 ℃, generate CO
2High selectivity be 65.2%.When with 3DOM/m LaFeO
3During for catalyst, T
50Reduce by 168 ℃, generated CO
2Selectivity is increased to 90.8%.And after partly replacing La with Ca, activity of such catalysts further improves.Wherein active best 3DOM/m La
0.9Ca
0.2FeO
3The carbon-smoke combustion temperature T of catalyst
50Further be reduced to 396 ℃, generate CO
2High selectivity be 95.4%.
Claims (10)
1. an emission of diesel engine carbon soot particles purifies with iron-based perovskite oxide catalyst, it is as active component and have the Ca-Ti ore type composite metal oxide of three-dimensional ordered macroporous-meso-hole structure by the two or more element in rare earth metal, transition metal, alkali metal and/or the alkaline-earth metal, the macropore of this composite metal oxide is uniform sequential counter opal structure, and mesoporous is vermicular texture.
2. perovskite oxide catalyst according to claim 1, the chemical composition of this perovskite oxide catalyst are Ln
1-xA
xBO
3, and x=0～0.3, wherein, Ln is a rare-earth metal La; A is alkaline-earth metal Ca; B is a transition-metal Fe.
3. perovskite oxide catalyst according to claim 1, this catalyst are that the precursor solution that will contain active component floods, obtains through after the high-temperature roasting then colloidal crystal template.
4. each described perovskite oxide Preparation of catalysts method of claim 1～3, the method comprising the steps of:
The nitrate that will contain active component is according to Ln
1-xA
xBO
3Stoichiometric proportion mix and to be dissolved in the organic complex agent solution, obtain the precursor solution of catalyst, wherein organic complexing agent is ethylene glycol or citric acid;
Mesoporous template surface activating agent is dissolved in hydrochloric acid or the salpeter solution, after mixing, joins in the precursor solution of catalyst, wherein surfactant is three block non-ionic surface active agent Brij-56 or P123;
Flood colloidal crystal template with precursor solution, after the suction filtration drying, after removing template, obtain three-dimensional ordered macroporous-mesoporous perovskite composite metal oxide in high-temperature roasting under the different atmosphere of inert gas and oxygen-containing gas.
5. preparation method according to claim 4, wherein, in the complex catalyst precursor liquid solution of described nitrate, organic complexing agent and the surfactant that contains active component and hydrochloric acid or salpeter solution, the total concentration of metal ion is 1～5mol/L.
6. preparation method according to claim 4, wherein, described roasting mode is as follows:
At first in inert atmosphere, be warming up to 500～800 ℃, and constant temperature 3～6h, reduce to room temperature after, in air atmosphere, be warming up to 500～800 ℃, and constant temperature 3～6h; Wherein, inert gas is argon gas or helium, and the flow velocity of inert gas, air is 50～100ml/min, and heating rate is 1～5 ℃/min.
7. preparation method according to claim 4, wherein, the dipping method of complex catalyst precursor liquid solution is the original position infusion process, relies on capillary force to flood.
8. preparation method according to claim 4, wherein, the preparation of described colloidal crystal template comprises step:
Under nitrogen protection and condensed water circulation cooling, acetone and redistilled water are mixed, and be preheated to 60～90 ℃ with water-bath, add main monomer methyl methacrylate and function monomer acrylic acid, continue to be heated to 60～90 ℃ with water-bath;
Under nitrogen protection and condensed water circulation cooling, adding has been preheating to 60～90 ℃ initiator solution, continues to stir, and behind reaction 1～5h, obtains monodispersed carboxy-modified polymethyl methacrylate, and its surface has carboxyl functional group;
With the rotating speed centrifugal treating 2～10h of microballoon emulsion with 1000～5000r/min, drying obtains closelypacked colloidal crystal template under the room temperature.
9. one kind is reduced diesel vehicle exhaust carbon-smoke particle burning method of temperature, and this method comprises that each the described catalyst of carbon soot particles and claim 1～3 that makes in the exhaust gas from diesel vehicle reacts under the loose condition that contacts.
10. the method for a purification of diesel car emission of carbon smoke particle, this method comprise and adopt each described catalyst of claim 1～3 that the soot particulate of emission of diesel engine is carried out catalytic combustion.
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