CN115585039B - Application of cerium-zirconium oxide carrier material containing pyrochlore structure in diesel vehicle - Google Patents
Application of cerium-zirconium oxide carrier material containing pyrochlore structure in diesel vehicle Download PDFInfo
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- 239000012876 carrier material Substances 0.000 title claims abstract description 21
- QWDUNBOWGVRUCG-UHFFFAOYSA-N n-(4-chloro-2-nitrophenyl)acetamide Chemical compound CC(=O)NC1=CC=C(Cl)C=C1[N+]([O-])=O QWDUNBOWGVRUCG-UHFFFAOYSA-N 0.000 title claims abstract description 7
- 239000003054 catalyst Substances 0.000 claims abstract description 57
- 239000000463 material Substances 0.000 claims abstract description 28
- 230000000694 effects Effects 0.000 claims abstract description 21
- 230000002378 acidificating effect Effects 0.000 claims description 3
- 229910006406 SnO 2 At Inorganic materials 0.000 claims description 2
- MWUXSHHQAYIFBG-UHFFFAOYSA-N nitrogen oxide Inorganic materials O=[N] MWUXSHHQAYIFBG-UHFFFAOYSA-N 0.000 claims 3
- 229910052760 oxygen Inorganic materials 0.000 abstract description 20
- 239000001301 oxygen Substances 0.000 abstract description 18
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 abstract description 17
- 230000009467 reduction Effects 0.000 abstract description 15
- 238000001179 sorption measurement Methods 0.000 abstract description 6
- 239000002253 acid Substances 0.000 abstract description 4
- 238000002474 experimental method Methods 0.000 abstract description 4
- 238000000746 purification Methods 0.000 abstract description 4
- 230000033116 oxidation-reduction process Effects 0.000 abstract description 3
- 229910002651 NO3 Inorganic materials 0.000 abstract description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 abstract description 2
- 230000010718 Oxidation Activity Effects 0.000 abstract description 2
- 238000006722 reduction reaction Methods 0.000 description 14
- 238000006243 chemical reaction Methods 0.000 description 10
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 8
- 239000004202 carbamide Substances 0.000 description 8
- 238000001069 Raman spectroscopy Methods 0.000 description 6
- 239000007789 gas Substances 0.000 description 5
- 238000000034 method Methods 0.000 description 5
- 238000001237 Raman spectrum Methods 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 229910052739 hydrogen Inorganic materials 0.000 description 4
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical group [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 3
- 238000000354 decomposition reaction Methods 0.000 description 3
- 239000001257 hydrogen Substances 0.000 description 3
- 239000006104 solid solution Substances 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 2
- 238000004435 EPR spectroscopy Methods 0.000 description 2
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 2
- 238000010531 catalytic reduction reaction Methods 0.000 description 2
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 230000002035 prolonged effect Effects 0.000 description 2
- 239000010453 quartz Substances 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 239000000758 substrate Substances 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- 229910052684 Cerium Inorganic materials 0.000 description 1
- 229920000877 Melamine resin Polymers 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- 239000002671 adjuvant Substances 0.000 description 1
- 239000003463 adsorbent Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- GWXLDORMOJMVQZ-UHFFFAOYSA-N cerium Chemical compound [Ce] GWXLDORMOJMVQZ-UHFFFAOYSA-N 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 238000001362 electron spin resonance spectrum Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 230000005284 excitation Effects 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 238000005470 impregnation Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000000338 in vitro Methods 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012544 monitoring process Methods 0.000 description 1
- -1 oxygen anions Chemical class 0.000 description 1
- 230000005298 paramagnetic effect Effects 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 231100000572 poisoning Toxicity 0.000 description 1
- 230000000607 poisoning effect Effects 0.000 description 1
- 238000000634 powder X-ray diffraction Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 238000004088 simulation Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
- F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
- F01N3/2066—Selective catalytic reduction [SCR]
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
- F01N3/28—Construction of catalytic reactors
- F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
- F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
- F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
- F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
- F01N3/24—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by constructional aspects of converting apparatus
- F01N3/28—Construction of catalytic reactors
- F01N3/2803—Construction of catalytic reactors characterised by structure, by material or by manufacturing of catalyst support
- F01N3/2807—Metal other than sintered metal
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
- Y02A50/00—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE in human health protection, e.g. against extreme weather
- Y02A50/20—Air quality improvement or preservation, e.g. vehicle emission control or emission reduction by using catalytic converters
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/10—Internal combustion engine [ICE] based vehicles
- Y02T10/12—Improving ICE efficiencies
Abstract
The invention discloses application of a cerium-zirconium oxide carrier material containing a pyrochlore structure in a diesel vehicle. Experiments show that k-CeZrO x The material has excellent oxidation-reduction performance, NO oxidation activity and rich oxygen vacancies, and has excellent NH 3 SCR Activity, for NO x Has strong adsorptivity, rich nitrate species on the surface, and can prolong NO in cold start stage of diesel vehicle x Is improved by "adsorption" + "reduction x The purification efficiency of the diesel engine is greatly reduced in the cold start stage NO x Is arranged in the air. k-CeZrO containing pyrochlore structure x The carrier material is loaded on the acid component to form NH 3 The SCR catalyst has higher SCR activity under the low-temperature condition and can reduce NO of a diesel engine under the low-temperature condition x Is arranged in the air.
Description
Technical Field
The invention belongs to NH treatment of tail gas of diesel vehicles 3 The technical field of SCR, in particular to a pyrochlore structure-containing k-Ce 2 Zr 2 O 8 CeZrO of (A) x Support material at NH 3 -application in SCR.
Background
NH 3 Selective catalytic reduction of NO x (NH 3 -SCR) is considered to be for oxygen-enriched diesel NO x The most promising technique for purification. In a diesel exhaust aftertreatment system, urea decomposition (CO (NH 2 ) 2 +H 2 O=2NH 3 +CO 2 ) Injection into a cavityNH of (C) 3 Is NH 3 -a reducing agent of the SCR reaction. However, NH 3 The SCR catalyst is located at the end of the diesel exhaust aftertreatment system, where the temperature during cold start is very low, even below 180 ℃, where urea cannot be efficiently decomposed into NH3. If the system is injecting urea at this time, first, incomplete decomposition of urea will result in reductant NH at low temperatures 3 Is low in concentration, which may inhibit NO x Is effective in reducing; second, incomplete decomposition of urea can lead to deposition of byproducts, such as melamine and incompletely decomposed urea, on the catalyst surface, potentially poisoning and deactivating the catalyst. Therefore, urea is generally injected in the SCR system at the temperature higher than 180 ℃ and the cold start period is shortened<180 ℃ C.) discharged NO x Is directly leaked. NO discharged by diesel vehicle x Is the primary source of mobile source NOx, where NO is the cold start process x The emission ratio is more than 90%, and NO in the cold start stage of the diesel vehicle is reduced x The emission is of vital importance. Due to the threshold value of urea injection temperature<180 ℃) and the single use of NH3-SCR catalysts has not been satisfactory for purifying NO at low temperatures x Is not limited. Thus, it is imperative to improve the low temperature and even ultra low Wen Tuoxiao activity of the catalyst to meet stringent emissions regulations.
Disclosure of Invention
The invention aims at overcoming the defects of the prior art and providing the application of cerium-zirconium oxide carrier material containing pyrochlore structure in diesel vehicles to improve NH 3 The low-temperature activity of the SCR catalyst, obtaining a catalyst with higher NH at low temperature 3 SCR-active catalyst for reducing NO in diesel engine at low temperature during cold start x Is arranged in the air.
The invention provides a pyrochlore-containing structure (k-Ce 2 Zr 2 O 8 ) Cerium zirconium oxide (k-CeZrO) x ) Support material for NH improvement 3 -low temperature NOx adsorption-storage and NH3-SCR activity of SCR catalysts.
k-Ce 2 Zr 2 O 8 Pyrochlore structure has ordered cation arrangement, 1/8 of oxygen anions are easy to remove, and the utilization rate of cerium can be highUp to 100%, shows excellent oxygen storage capacity and redox performance, which is favorable for heterogeneous catalytic reaction, and oxygen vacancies are easily formed on the surface, which is favorable for the activation of reactants and the oxidation of NO to NO 2 Promoting the SCR reaction. Experiments show that k-CeZrO x Material (containing pyrochlore structure k-Ce) 2 Zr 2 O 8 CeZrO of (A) x Carrier material) has excellent redox performance, NO oxidation activity and abundant oxygen vacancies, and has excellent NH 3 SCR activity capable of prolonging NO in cold start stage of diesel vehicle x Is increased by "adsorption-storage" + "reduction x The conversion rate of NO in the cold start stage of the diesel vehicle is greatly reduced x Is arranged in the air.
Further, the pyrochlore-containing structure (k-Ce 2 Zr 2 O 8 ) k-CeZrO of (C) x The carrier material is prepared by the following method: ceZrO is treated with x Material at H 2 Roasting at 900-1500 ℃ under atmosphere for 1-10 h to obtain the pyrochlore structure-containing k-Ce 2 Zr 2 O 8 k-CeZrO of (C) x A carrier material.
Further, the CeZrO x The molar ratio of Ce to Zr is (0.2-0.95): 0.05-0.8.
The invention also provides NH with high low-temperature activity 3 -SCR catalyst, said catalyst being a pyrochlore structure-containing k-Ce 2 Zr 2 O 8 k-CeZrO of (C) x A carrier material.
The invention also provides NH with high low-temperature activity 3 SCR catalyst consisting of a pyrochlore-containing k-CeZrO x k-CeZrO of (C) x Support material and support on k-CeZrO x The acidic component of the carrier material consists of WO 3 、MoO 3 、Nb 2 O 5 、SnO 2 At least one of HPAs.
Preferably, the NH having high low temperature activity 3 The SCR catalyst is WO 3 /k-CeZrO x 、MoO 3 /k-CeZrO x 、WO 3 -MoO 3 /k-CeZrO x One of the following
The invention also provides NH with high low-temperature activity 3 The SCR catalyst can be prepared by conventional impregnation methods.
Compared with the prior art, the invention has the following beneficial effects:
the invention uses k-CeZrO with pyrochlore structure x The material being NH 3 -SCR catalyst carrier material for purifying NO in diesel vehicle exhaust x The k-CeZrO containing pyrochlore structure x The carrier material is used as the carrier material of the diesel vehicle tail gas purifying catalyst, and can lead the NO generated by the diesel vehicle in the cold start stage x Adsorption and reduction, and greatly reduces NO in cold start stage x Is discharged to solve the problems of the prior NH 3 SCR catalysts have failed to meet low-temperature purification of NO x Is required to make NO x The problem of leaking emissions can be met with strict emissions regulations.
Drawings
FIG. 1 shows the Raman spectra (a) and XRD diffraction patterns (b) of the materials prepared in the examples and comparative examples;
FIG. 2 shows EPR spectra (a) and H prepared in examples and comparative examples 2 -TPR curve (b);
FIG. 3 simulation of NO of catalyst at Cold Start x Storage Property (a) and NH of catalyst 3 -SCR activity (b);
Detailed Description
The invention is further illustrated by the following examples. It is to be noted that the following examples are given solely for the purpose of illustration and are not to be construed as limitations on the scope of the invention, since numerous insubstantial modifications and variations of the invention will become apparent to those skilled in the art in light of the above disclosure, and yet remain within the scope of the invention.
Example 1
CeZrO is treated with x The carrier (Ce: zr molar ratio 0.68:0.32) was in H 2 Treating 1-10 h under 950 deg.C to obtain a composition containing k-Ce 2 Zr 2 O 8 k-CeZrO of pyrochlore structure x A material.
Example 2
CeZrO x The carrier (Ce: zr molar ratio 0.68:0.32) was in H 2 Treating 1-10 h under 950 deg.C to obtain a composition containing k-Ce 2 Zr 2 O 8 k-CeZrO of pyrochlore structure x The material is further impregnated with 1.1071g of ammonium metatungstate to 10g k-CeZrO x Drying the sample at 80deg.C for 10 hr, and roasting at 550deg.C in air atmosphere for 3 hr to obtain WO 3 /k-CeZrO x A catalyst.
Comparative example 1
CeZrO is treated with x The carrier (Ce: zr molar ratio 0.68:0.32) was treated at 950℃in an air atmosphere for 1-10 h to give A-CeZrO x A material.
Comparative example 2
CeZrO x The carrier (Ce: zr molar ratio 0.68:0.32) was treated at 950℃in an air atmosphere for 1-10 h to give A-CeZrO x The material was further impregnated with 1.1071g of ammonium meta-tungstate to 10g of CeZrO x The sample was dried at 80℃for 10 hours and then calcined at 550℃for 3 hours in an air atmosphere to give WO 3 /A-CeZrO x A catalyst.
Each catalyst prepared as outlined above was subjected to the structure-activity performance test.
(1) Visible Raman (Vis-Raman)
Raman spectra of the samples were collected using a LabRAM HR laser raman spectrometer (Horiba Jobin Yvon, france). YAG laser using diode pump, excitation wavelength 532 nm, power 73.5 mw, detection range 50-2000 cm -1 。
(2) X-ray diffraction (XRD)
Powder X-ray diffraction experiments were performed using a Rigaku DX-2500 diffractometer (Rigaku, japan) with Cu kα (λ= 0.15406 nm) as the radiation source. The tube voltage was 40 kV and the current was 25 mA. XRD diffraction patterns were recorded at 0.2 deg. per second intervals over the range of 10-80 deg..
(3) Electron paramagnetic spin resonance (ERP)
The concentration of oxygen vacancies on the catalyst was measured using an electron paramagnetic resonance spectrometer (JEOL JES-FA200, japan) at a temperature of 77K.
(4) Hydrogen programmed temperature reduction (H) 2 -TPR）
H 2 Temperature programmed reduction experiments were tested on a TP-5076TPD/TPR dynamic adsorber (Advance, tianjin) with TCD as detector. The mass of the sample in the quartz tube microreactor was 100 mg, and the sample was cooled to 30 ℃ after pretreatment of 1 h at 450 ℃ in He atmosphere. At 5 vol.% H 2 -95 vol.%N 2 The temperature was increased from 30℃to 800℃in the atmosphere at a rate of 10℃per minute, and a curve was recorded. CuO as a standard sample for calculating H of a catalyst 2 Consumption amount.
(5) Catalyst NO x Evaluation of purification Performance
The AdSCR performance of the catalyst was evaluated in an autonomously installed fixed bed quartz tube flow reactor. Simulating cold start phase NO in a reactor at a temperature below 180 °c x To evaluate the NO of the monolithic catalyst x Adsorption storage performance. The simulated reaction atmosphere is: 500 ppm NO,5 vol.% O 2 Balance gas N 2 The temperature rise from 50℃at 20℃per minute was monitored by FT-IR Antaris IGS (Nicolet, USA) and the NO was recorded x Concentration as a function of reaction temperature and time. At a temperature above 180 ℃, 550 ppm NH will be 3 Continuous NH introduction into reactor 3 SCR reaction, monitoring N in tail gas by FT-IR Antaris IGS x O y And NH 3 Is a concentration change of (c).
The above test results are shown in fig. 1 to 3:
the Raman spectrum of the sample is shown in FIG. 1a, 475 cm -1 The Raman vibration peak at the position is attributed to F of O-Ce-O with cubic fluorite structure 2g A symmetrical vibration peak; 615 cm -1 The vibration peak at the position is attributed to a defect structure; 432 cm -1 And 527 cm -1 The raman peak at the site is attributed to the pyrochlore structurek-Ce 2 Zr 2 O 8 Characteristic vibration peaks of (2) [226-228] . O-Ce-O and defective structure were detected in all samples, but only in k-CeZrO x And WO 3 /k-CeZrO x All observed in the Raman spectrum of (a) to belong to pyrochloreCharacteristic peaks of the structure.
The XRD pattern of the sample is shown in FIG. 1b, and A-CeZrO obtained by air treatment at 950 DEG C x Only Ce of cubic fluorite structure was detected in the sample 0.6 Zr 0.4 O 2 Solid solutions, however, k-CeZrO x In the X-ray diffraction pattern of (2), except for the presence of Ce 0.6 Zr 0.4 O 2 In vitro, a pyrochlore structure was observed at 2q=14° with solid solutionsk-Ce 2 Zr 2 O 8 Is a characteristic diffraction peak of (2). Furthermore, WO 3 The loading of the catalyst and the calcination at 550 ℃ for 3 hours in the air atmosphere can not influence the structure of the corresponding carrier, and the cubic fluorite structure Ce can be detected on all catalysts 0.6 Zr 0.4 O 2 Diffraction peaks of solid solution, and pyrochlorek-Ce 2 Zr 2 O 8 The structure still exists in W/k-CeZrO x In the catalyst, this is consistent with Raman results. Thus, ceZrO x The pyrochlore structure k-Ce is not formed when the material is treated in an air atmosphere at high temperature 2 Zr 2 O 8 。CeZrO x H at high temperature 2 Treatment in atmosphere promotes the pyrochlore structure k-Ce 2 Zr 2 O 8 And has better stability.
The low temperature Electron Paramagnetic Resonance (EPR) results are shown in figure 2 a. The symmetrical peak at g=2.003 is assigned to the characteristic peak of unpaired electrons in oxygen vacancies, the intensity of which is closely related to the concentration of oxygen vacancies. Has the following characteristics ofk-Ce 2 Zr 2 O 8 Structural k-CeZrOx and WO 3 /k-CeZrO x The peak intensity of the catalyst is obviously higher than that of A-CeZrO x And WO 3 /A-CeZrO x Indicating that the presence of pyrochlore structure does increase k-CeZrO x And WO 3 /k-CeZrO xConcentration of surface oxygen vacancies. Thus, the first and second substrates are bonded together,k-Ce 2 Zr 2 O 8 the presence of the structure promotes the formation of oxygen vacancies on the catalyst, probably becausek-Ce 2 Zr 2 O 8 The structure has a lower average oxygen vacancy forming energy.
H 2 The TPR results are shown in FIG. 2b, A-CeZrO x Exhibiting a unimodal shape curve at 543 °cThe method comprises the steps of carrying out a first treatment on the surface of the And k-CeZrO x At 566 ℃, but there is a shoulder at 486 ℃. Although A-CeZrO x The reduction peak temperature is lower thankCZ-6, but importantly, A-CeZrO x The reduction peak intensity of (C) is significantly lower than that of k-CeZrO x Is a peak intensity of (c). k-CeZrO x The catalyst consumed hydrogen in an amount of 1208. Mu. Mol/g, at least A-CeZrO x (549. Mu. Mol/g), it is apparent that k-CeZrO x Ratio A-CeZrO x Has stronger oxidation-reduction performance. Load WO 3 After that, the reduction peak of the catalyst shifts to high temperature, WO 3 /A-CeZrO x And WO 3 /k-CeZrO x Has a similar shape of the reduction peak; peaks below 600 ℃ are attributed to reduction of surface and subsurface oxygen, while peaks above 600 ℃ are attributed to reduction of bulk oxygen. Although WO 3 /k-CeZrO x Reduction peak temperature (706 ℃) ratio WO 3 /A-CeZrO x (674 ℃ C.) at 32 ℃ but over the entire reaction temperature range, WO 3 /A-CeZrO x The reduction peak intensity of (C) is far lower than that of WO 3 /k-CeZrO x And WO 3 /k-CeZrO x The hydrogen consumption of (C) is 1354 mmol/g, WO 3 /A-CeZrO x (641 mmol/g) 2 times, WO 3 /k-CeZrO x Ratio W/A-CeZrO x With more reducible oxygen species.k-Ce 2 Zr 2 O 8 The presence of (C) promotes W/k-CeZrO x The reduction of oxygen species on the surface of the catalyst enhances the redox performance of the catalyst, thereby improving the adsorption-selective catalytic reduction performance of the catalyst. This is mainly because the presence of pyrochlore structure increases the availability and diffusivity of oxygen species, thereby increasing the redox performance of the catalyst.
FIG. 3a shows a simulated cold start phase<180. DEG C) catalyst pair NO x Is to be 500 ppm NO and 5 vol.% O 2 Introducing into a reactor, heating at 20 ℃ per min, and detecting NO at the outlet x Concentration to measure NO x Complete storage time on catalyst, i.e. NO x Store NO in reaction x The duration of zero emissions is achieved. k-CeZrO x NO of (2) x When fully stored115 s, i.e. NO during this period x Completely adsorbed on the surface of the sample; A-CeZrO x NO of (2) x The total storage time is 91 s, which is obviously shorter than k-CeZrO x Is set to 115 s of (2). In the presence of acid adjuvants WO 3 NO of the catalyst x The complete storage time is shortened, mainly due to the introduction of acid assistants, which are disadvantageous for the acid gas NO x Is adsorbed by the adsorbent. However, WO 3 /k-CeZrO x NO of (2) x Complete storage time (75 s) is still WO 3 /A-CeZrO x 1.5 times the catalyst. Thus, pyrochlore structurek-Ce 2 Zr 2 O 8 The presence of (C) significantly increases k-CeZrO x And WO 3 /k-CeZrO x NO of catalyst x Adsorption storage performance.
Above 180 ℃, NO x With NH 3 Is gradually reduced by introduction of NH of the catalyst 3 The SCR activity results are shown in FIG. 3b, which shows that the catalyst is in low-medium temperature stage< 250 °C），WO 3 /k-CeZrO x NO of (2) x Conversion is about higher than WO 3 /A-CeZrO x 10% higher than that of WO 3 /k-CeZrO x NH of (C) 3 SCR Activity is superior to WO 3 /A-CeZrO x . Thus, the first and second substrates are bonded together,k-Ce 2 Zr 2 O 8 the presence of the structure not only promotes NO x Is adsorbed and stored, and the NO is prolonged x Complete shelf life on catalyst and also increase NH 3 Medium-low temperature activity of SCR reaction.
The above results indicate that: containing k-Ce 2 Zr 2 O 8 k-CeZrO of (C) x The carrier material has excellent oxidation-reduction performance, NO oxidation performance and rich oxygen vacancies; containing k-Ce 2 Zr 2 O 8 k-CeZrO of (C) x The support material has excellent NH 3 -SCR activity, in particular medium-low temperature activity; containing k-Ce 2 Zr 2 O 8 k-CeZrO of (C) x The material has strong NO x Adsorption performance, rich nitrate species are generated on the surface of the catalyst, and NO in cold start is prolonged x Is a complete storage time of the container. Thus, the pyrochlore structure k-Ce is contained 2 Zr 2 O 8 k-CeZrO of (C) x The carrier material can improve NO of the catalyst x Adsorption-storage and reduction properties.
Claims (5)
1. Cerium zirconium oxide support material containing pyrochlore structure for improving NH 3 Low temperature NO of SCR catalyst x Adsorption-storage and NH 3 Use of the pyrochlore-containing structure kappa-Ce in SCR Activity 2 Zr 2 O 8 kappa-CeZrO of (C) x The carrier material is prepared by mixing CeZrO x Material at H 2 Roasting at 900-1500 ℃ for 1-10 h under atmosphere to obtain the product; the CeZrO x The molar ratio of Ce to Zr in the material is (0.2-0.95): 0.05-0.8.
2. Cerium-zirconium oxide carrier material containing pyrochlore structure as NH in purifying nitrogen oxides in cold start stage of diesel vehicle 3 Use of a support material for SCR catalysts, said support material containing pyrochlore structures kappa-Ce 2 Zr 2 O 8 kappa-CeZrO of (C) x The carrier material is prepared by mixing CeZrO x Material at H 2 Roasting at 900-1500 ℃ for 1-10 h under atmosphere to obtain the product; the CeZrO x The molar ratio of Ce to Zr in the material is (0.2-0.95): 0.05-0.8.
3. NH with high low temperature activity 3 -SCR catalyst, characterized in that the catalyst is a pyrochlore structure containing kappa-Ce 2 Zr 2 O 8 kappa-CeZrO of (C) x A carrier material; the pyrochlore structure-containing kappa-Ce 2 Zr 2 O 8 kappa-CeZrO of (C) x The carrier material is prepared by mixing CeZrO x Material at H 2 Roasting at 900-1500 ℃ for 1-10 h under atmosphere to obtain the product; the CeZrO x The molar ratio of Ce to Zr in the material is (0.2-0.95): 0.05-0.8.
4. NH with high low temperature activity 3 SCR catalyst, characterized in that the catalyst consists of a pyrochlore-containing structure kappa-Ce 2 Zr 2 O 8 kappa-CeZrO of (C) x Support material and support on kappa-CeZrO x An acidic component on a support material, said acidic component being WO 3 、MoO 3 、Nb 2 O 5 、SnO 2 At least one of HPAs; the pyrochlore structure-containing kappa-Ce 2 Zr 2 O 8 kappa-CeZrO of (C) x The carrier material is prepared by mixing CeZrO x Material at H 2 Roasting at 900-1500 ℃ for 1-10 h under atmosphere to obtain the product; the CeZrO x The molar ratio of Ce to Zr in the material is (0.2-0.95): 0.05-0.8.
5. NH having high Low temperature Activity according to claim 4 3 -SCR catalyst, characterized in that the catalyst is WO 3 /κ-CeZrO x 、MoO 3 /κ-CeZrO x 、WO 3 -MoO 3 /κ-CeZrO x At least one of them.
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