CN115090305B - Metal-nonmetal co-modified low-temperature SCR denitration catalyst and preparation method thereof - Google Patents
Metal-nonmetal co-modified low-temperature SCR denitration catalyst and preparation method thereof Download PDFInfo
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- 239000003054 catalyst Substances 0.000 title claims abstract description 157
- 229910052755 nonmetal Inorganic materials 0.000 title claims abstract description 36
- 238000002360 preparation method Methods 0.000 title abstract description 13
- 238000012986 modification Methods 0.000 claims abstract description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 23
- 229910052751 metal Inorganic materials 0.000 claims abstract description 22
- 239000002184 metal Substances 0.000 claims abstract description 22
- 230000004048 modification Effects 0.000 claims abstract description 17
- 239000000758 substrate Substances 0.000 claims abstract description 7
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 33
- OERNJTNJEZOPIA-UHFFFAOYSA-N zirconium nitrate Chemical compound [Zr+4].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O OERNJTNJEZOPIA-UHFFFAOYSA-N 0.000 claims description 18
- 238000006467 substitution reaction Methods 0.000 claims description 15
- 238000010438 heat treatment Methods 0.000 claims description 11
- FYDKNKUEBJQCCN-UHFFFAOYSA-N lanthanum(3+);trinitrate Chemical compound [La+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O FYDKNKUEBJQCCN-UHFFFAOYSA-N 0.000 claims description 11
- MIVBAHRSNUNMPP-UHFFFAOYSA-N manganese(2+);dinitrate Chemical compound [Mn+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O MIVBAHRSNUNMPP-UHFFFAOYSA-N 0.000 claims description 11
- 239000008367 deionised water Substances 0.000 claims description 10
- 229910021641 deionized water Inorganic materials 0.000 claims description 10
- 238000000034 method Methods 0.000 claims description 10
- 239000011259 mixed solution Substances 0.000 claims description 9
- 230000001105 regulatory effect Effects 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 7
- 238000005470 impregnation Methods 0.000 claims description 6
- 150000002500 ions Chemical class 0.000 claims description 6
- 229910021645 metal ion Inorganic materials 0.000 claims description 6
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 5
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 5
- 238000001704 evaporation Methods 0.000 claims description 5
- 238000003756 stirring Methods 0.000 claims description 5
- 238000005303 weighing Methods 0.000 claims description 5
- 238000007873 sieving Methods 0.000 claims description 4
- DDFHBQSCUXNBSA-UHFFFAOYSA-N 5-(5-carboxythiophen-2-yl)thiophene-2-carboxylic acid Chemical compound S1C(C(=O)O)=CC=C1C1=CC=C(C(O)=O)S1 DDFHBQSCUXNBSA-UHFFFAOYSA-N 0.000 claims description 3
- 238000004090 dissolution Methods 0.000 claims description 3
- 238000003760 magnetic stirring Methods 0.000 claims description 3
- 238000003980 solgel method Methods 0.000 claims description 3
- 230000000694 effects Effects 0.000 abstract description 35
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 abstract description 10
- 229910052717 sulfur Inorganic materials 0.000 abstract description 10
- 239000011593 sulfur Substances 0.000 abstract description 10
- 239000013078 crystal Substances 0.000 abstract description 6
- 229910007740 Zr—F Inorganic materials 0.000 description 15
- 239000000243 solution Substances 0.000 description 12
- 229910052760 oxygen Inorganic materials 0.000 description 11
- 238000001179 sorption measurement Methods 0.000 description 10
- 238000003795 desorption Methods 0.000 description 9
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 8
- 239000001301 oxygen Substances 0.000 description 8
- 238000006243 chemical reaction Methods 0.000 description 7
- 239000011572 manganese Substances 0.000 description 7
- 230000004913 activation Effects 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- UGFAIRIUMAVXCW-UHFFFAOYSA-N Carbon monoxide Chemical compound [O+]#[C-] UGFAIRIUMAVXCW-UHFFFAOYSA-N 0.000 description 5
- 239000003546 flue gas Substances 0.000 description 5
- 239000007789 gas Substances 0.000 description 4
- 239000002243 precursor Substances 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 238000003723 Smelting Methods 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 238000000026 X-ray photoelectron spectrum Methods 0.000 description 2
- 239000002253 acid Substances 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000004939 coking Methods 0.000 description 2
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- 230000009467 reduction Effects 0.000 description 2
- 239000000779 smoke Substances 0.000 description 2
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 1
- 239000004480 active ingredient Substances 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000010835 comparative analysis Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000002803 fossil fuel Substances 0.000 description 1
- 230000036541 health Effects 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 229910052748 manganese Inorganic materials 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- 230000033116 oxidation-reduction process Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 239000010453 quartz Substances 0.000 description 1
- 239000000376 reactant Substances 0.000 description 1
- 238000009877 rendering Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
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- B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01J27/00—Catalysts comprising the elements or compounds of halogens, sulfur, selenium, tellurium, phosphorus or nitrogen; Catalysts comprising carbon compounds
- B01J27/06—Halogens; Compounds thereof
- B01J27/135—Halogens; Compounds thereof with titanium, zirconium, hafnium, germanium, tin or lead
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
- B01D53/34—Chemical or biological purification of waste gases
- B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
- B01D53/86—Catalytic processes
- B01D53/8621—Removing nitrogen compounds
- B01D53/8625—Nitrogen oxides
- B01D53/8628—Processes characterised by a specific catalyst
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2258/00—Sources of waste gases
- B01D2258/02—Other waste gases
- B01D2258/0283—Flue gases
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Abstract
The invention provides a metal-nonmetal co-modified low-temperature SCR denitration catalyst and a preparation method thereof, wherein the metal-nonmetal co-modified low-temperature SCR denitration catalyst comprises the following components: a primary base catalyst, a metal active component for metal modification, and a nonmetal active component for nonmetal modification; the original substrate catalyst is perovskite LaMnO 3 The catalyst has Zr as the active metal component and F as the inactive non-metal component. The invention also comprises a preparation method of the denitration catalyst. The catalyst of the invention has a perovskite crystal structure, has good thermal stability and uniformity, and effectively solves the problems of NH in the prior art 3 The SCR catalyst has the problems of poor low-temperature activity, narrow temperature window, poor sulfur resistance and water resistance, and the like.
Description
Technical Field
The invention belongs to the technical field of catalysts, and particularly relates to a metal-nonmetal co-modified low-temperature SCR denitration catalyst and a preparation method thereof.
Background
NO caused by combustion of fossil fuels x Pollution endangers human health, NH 3 The SCR technology is one of the most widely used and mature flue gas denitration technologies in the current industry, and the core of the SCR technology is NH 3 -selection of SCR catalyst. The traditional noble metal catalyst has good denitration activity, but is high in price and poor in sulfur resistance performance; the V-W-Ti series catalyst is the most widely used denitration catalyst in the current business, has excellent high-temperature activity and sulfur resistance, but has narrow temperature window and poor low-temperature activity, is difficult to adapt to the complex conditions of flue gas emission in the industries of coking, smelting and the like, and has limited practical application.
Manganese-based catalysts have been attracting attention because of their excellent redox performance, polyvalent state and good low-temperature activity, but they have disadvantages of narrow temperature window, poor sulfur resistance, and the like. Researches show that the perovskite crystal structure is formed by structure regulation in the preparation process of the catalyst, so that the surface adsorption performance, the structural stability, the uniformity and the like of the catalyst can be improved, and the physicochemical property and the surface property of the catalyst can be further improved by metal and nonmetal doping, so that the catalyst is constructed to have high low-temperature NH 3 SCR-active, wide temperature window, high resistance denitration catalysts offer a viable idea.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a metal-nonmetal co-modified low-temperature SCR denitration catalyst and a preparation method thereof, and the obtained catalyst has a perovskite crystal structure, has good thermal stability and uniformity, and effectively solves the problems of NH in the prior art 3 The SCR catalyst has the problems of poor low-temperature activity, narrow temperature window, poor sulfur resistance and water resistance, and the like.
In order to achieve the above purpose, the technical scheme adopted by the invention for solving the technical problems is as follows: the metal-nonmetal co-modified low-temperature SCR denitration catalyst comprises the following components: a primary base catalyst, a metal active component for metal modification, and a nonmetal active component for nonmetal modification;
the original substrate catalyst is perovskite LaMnO 3 The catalyst has Zr as the active metal component and F as the inactive non-metal component.
Further, the substitution amount of the metal active component Zr to the A-site ion La in the original substrate catalyst is 20%, and the mass percentage of the nonmetal active component F is 1.6%.
Further, the metal active component Zr is introduced by a citric acid-sol gel method to partially replace the A-site ion La in the original substrate catalyst.
Further, the nonmetallic active ingredient F is introduced by an impregnation method, supported on the original base catalyst.
The preparation method of the metal-nonmetal co-modified low-temperature SCR denitration catalyst comprises the following steps of:
(1) Respectively weighing lanthanum nitrate, zirconium nitrate and manganese nitrate, then adding citric acid and adding deionized water for dissolution to obtain a mixed solution;
(2) Dropwise adding ammonia water into the mixed solution obtained in the step (1) under the stirring condition, regulating the pH value to 8, then heating in a water bath under the conditions of 90 ℃ and magnetic stirring, evaporating to dryness to obtain gel, and then roasting the gel in a gradient manner after the gel is dried to obtain a catalyst Zr-2;
(3) Dissolving ammonium fluoride with deionized water, then placing the catalyst Zr-2 obtained in the step (2) into the deionized water for ultrasonic impregnation for 2 hours, drying, roasting, and then sequentially tabletting and sieving to obtain the metal-nonmetal co-modified low-temperature SCR denitration catalyst.
Further, in the step (1), the molar ratio of lanthanum nitrate, zirconium nitrate and manganese nitrate is 0.6-1:0.1-0.3:1.
Further, in the step (1), the molar ratio of lanthanum nitrate, zirconium nitrate and manganese nitrate is 0.8:0.2:1.
Further, in the step (1), the molar ratio of the metal ions to the citric acid in the mixed solution is 1:1-3.
Further, in the step (1), the molar ratio of the metal ions to the citric acid in the mixed solution is 1:2.
Further, in the step (2), the mixture was dried at 120℃for 24 hours.
Further, in the step (2), the materials are respectively roasted for 2 to 4 hours at 400 to 500 ℃ and 800 to 900 ℃ with the heating rate of 5 ℃/min.
Further, in the step (2), the mixture is baked for 3 hours at 450 ℃ and 850 ℃ respectively, and the heating rate is 5 ℃/min.
Further, in the step (3), drying is performed at 80℃for 24 hours.
Further, in the step (3), the size of the sieve is 20-40 meshes.
In summary, the invention has the following advantages:
1. the catalyst Zr-2-F-1.6 of the invention has a perovskite crystal structure, has good thermal stability and uniformity, is beneficial to improving the reaction activity and stability of the catalyst, and effectively solves the problems of NH in the prior art 3 The SCR catalyst has the problems of poor low-temperature activity, narrow temperature window, poor sulfur resistance and water resistance, and the like.
2. The catalyst Zr-2-F-1.6 and unmodified LaMnO 3 Compared with the catalyst and the Zr-2 catalyst modified by Zr alone, the specific surface area, the surface adsorption oxygen content and the surface acidity of the catalyst are all obviously enhanced, and the catalyst shows excellent low-temperature NH 3 SCR denitration activity and broad temperature window, sulfur resistance and N 2 The selectivity is also improved obviously. And the preparation process is stable and easy to implement, and has lower requirements on instruments and equipment.
3. According to the invention, the target catalyst is synthesized by two steps of a citric acid-sol gel method and an impregnation method, and the obtained catalyst has an excellent perovskite crystal structure, excellent texture performance and surface activity, a preparation process is stable and feasible, and has a good application prospect in the field of complex flue gas denitration and purification treatment in industries such as coking, smelting and the like. Wherein the Zr-F co-modified catalyst Zr-2-F-1.6 shows very excellent NH 3 SCR denitration activity, NO up to 100% in the temperature range 140-220 DEG C x The removal rate can reach more than 80 percent of NO in the temperature range of 100-300 DEG C x The removal rate is high, and more than 97% of NO can be realized under the low temperature condition of 100 DEG C x The removal rate; in addition, zr-F co-modified catalyst Zr-2-F-1.6 also shows very excellent SO 2 /H 2 O resistance at 100ppm SO 2 And 10vol% H 2 In the presence of O, 99% of NO can be maintained x The removal rate.
Drawings
FIG. 1 is a schematic representation of NH for a series of catalysts modified with Zr substitution alone in different ratios 3 -SCR activity map;
FIG. 2 is a graph of NH for Zr-F co-modified series catalysts with different F doping ratios 3 -SCR activity map;
FIG. 3 is NH of a different modified catalyst 3 -SCR activity longitudinal comparison plot;
FIG. 4 is a graph of N2 selectivity for different modified catalysts;
FIG. 5 is a graph of long-cycle sulfur resistance versus water resistance for various modified catalysts;
FIG. 6 is an XRD pattern for different modified catalysts;
FIG. 7 is an XPS plot of different modified catalysts;
FIG. 8 is a TPR/TPD graph for various modified catalysts.
Detailed Description
Example 1
Base catalyst LaMnO 3 Is prepared from
Weighing a certain amount of precursor lanthanum nitrate and manganese nitrate, adding a certain amount of citric acid, and dissolving into a solution of 0.2-0.4mol/L by using a proper amount of deionized water; the molar ratio of the precursors was lanthanum nitrate to manganese nitrate=1:1, and the molar ratio of total metal ions to citric acid in the solution was 1:2. Ammonia water is used as a pH regulator, and is slowly added into the solution dropwise, and the solution is continuously stirred and is regulated to a pH value of about 8; heating the solution with the pH value regulated in a water bath kettle at 90 ℃ and magnetically stirring, and evaporating the water to dryness to form gel; drying the gel at 120deg.C for 24 hr, and gradient roasting at air atmosphere of 450 deg.C for 3 hr and 750 deg.C for 3 hr at a heating rate of 5 deg.C/min to obtain preliminary LaMnO 3 A powder catalyst; tabletting and sieving the powdery catalyst to obtain the final 20-40 mesh granuleThe target catalyst was designated LM-1.
By LaMnO 3 Preparation of A-site Zr-substituted individual metal modified catalyst based on catalyst
Weighing a certain amount of precursor lanthanum nitrate, zirconium nitrate and manganese nitrate, adding a certain amount of citric acid, and dissolving into a solution of 0.2-0.4mol/L by using a proper amount of deionized water; the molar ratio of each precursor, (lanthanum nitrate+zirconium nitrate): manganese nitrate=1:1, and the molar ratio of total metal ions to citric acid in the solution is 1:2, wherein the substitution amount of Zr to La ions at A position is 0.1, 0.2, 0.3, 0.5 and 0.5 respectively. Ammonia water is used as a pH regulator, and is slowly added into the solution dropwise, and the solution is continuously stirred and is regulated to a pH value of about 8; heating the solution with the pH value regulated in a water bath kettle at 90 ℃ and magnetically stirring, and evaporating the water to dryness to form gel; drying the gel at 120 ℃ for 24 hours, and then carrying out gradient roasting under the conditions of 450 ℃ and 850 ℃ for 3 hours in an air atmosphere, wherein the heating rate is 5 ℃/min, thus obtaining the preliminary Zr-substituted modified LaMnO 3 A powder catalyst; the powdery catalyst is pressed into tablets and sieved to obtain the final 20-40-mesh granular target catalyst, and the obtained catalysts are named as Zr-1, zr-2, zr-3, zr-4 and Zr-5 according to different Zr substitution amounts.
Zr is used for replacing and modifying LaMnO 3 The preparation method of the F-doped Zr-F co-modified catalyst, which is based on the catalyst, is a metal-nonmetal co-modified low-temperature SCR denitration catalyst and comprises the following steps:
(1) Respectively weighing lanthanum nitrate, zirconium nitrate and manganese nitrate, then adding citric acid and adding deionized water for dissolution to obtain a mixed solution; lanthanum nitrate and zirconium nitrate, wherein manganese nitrate=0.8:0.2:1, and the molar ratio of total metal ions to citric acid in the solution is 1:2, wherein the substitution amount of Zr to La ions at A position is 0.2;
(2) Dropwise adding ammonia water into the mixed solution obtained in the step (1) under the stirring condition, regulating the pH value to 8, heating in a water bath under the conditions of 90 ℃ and magnetic stirring, evaporating to dryness to obtain gel, drying the gel at 120 ℃ for 24 hours, roasting at 450 ℃ for 3 hours and at 850 ℃ for 3 hours, and obtaining a catalyst Zr-2 at a heating rate of 5 ℃/min; based on a certain amount of Zr-2, the required mass percentages of F are respectively 0.8%, 1.2%, 1.6% and 2.0%;
(3) Dissolving ammonium fluoride with deionized water, then placing the catalyst Zr-2 obtained in the step (2) in the solution for ultrasonic impregnation for 2 hours, drying at 80 ℃ for 24 hours, roasting at 360 ℃ for 2 hours, and then tabletting and sieving (20-40 meshes) in sequence to obtain the metal-nonmetal co-modified low-temperature SCR denitration catalyst. The catalysts obtained were designated Zr-2-F-0.8, zr-2-F-1.2, zr-2-F-1.6 and Zr-2-F-2.0, respectively, according to the amount of F doping.
Experimental example
Evaluation of catalyst NH Using fixed bed reactor 3 -SCR activity. The reactor is a quartz tube with the inner diameter of 14mm, and the temperature is regulated and controlled by using a thermocouple and a tubular electric furnace; the test temperature range is 80-300 ℃, the temperature rising rate is 5 ℃/min, each 20 ℃ is used as a temperature point, each temperature point stays for 30min, and data are recorded. The simulated flue gas was 500ppm NO,500ppm NH 3 ，5％O 2 N 2 As balance gas, the total gas flow was 500ml/min and the space velocity was 30000h -1 The catalyst loading volume was 1mL; the concentration of NO before and after the reaction is detected in real time by a smoke analyzer (Gasbard-3000), and the NO is detected in real time by an online infrared smoke analyzer (Antaris IGS) 2 、N 2 O、NH 3 Is a concentration of (3). NO (NO) x The conversion was calculated according to the following formula:
wherein [ NO ] x ]＝[NO]+[NO 2 ]。
SO 2 /H 2 O resistance test catalyst was tested for SO using a fixed bed reactor 2 And H 2 O resistance. Long-period SO resistance 2 /H 2 In the O-test, the temperature was 200deg.C and the simulated flue gas included 500ppm NO,500ppm NH 3 ，100ppmSO 2 ，5％O 2 ，10vol％H 2 O and N 2 As a balance gas, the total gas flow was 500ml/min and the reaction space velocity was 30000h -1 。
For different proportions of singleSingle Zr substituted modified series catalyst for NH 3 SCR activity test shows that the catalyst Zr-2 with Zr substitution amount of 0.2 has the best denitration activity, as shown in figure 1.
As can be seen from FIG. 1, the catalyst Zr-2 can reach 100% NO in the temperature range of 140-220 DEG C x Removal rate and 80% NO x The temperature range corresponding to the removal rate is widened to 100-300 ℃, and the low-temperature denitration activity and the temperature window of the catalyst are greatly improved.
Based on the single metal modified catalyst Zr-2, the catalyst Zr-2-F-1.6 with F doping amount of 1.6% can be found to have the optimal denitration activity by doping the nonmetallic component F with different proportions, as shown in figure 2.
As can be seen from FIG. 2, the catalyst Zr-2-F-1.6 can reach 100% NO at the temperature of 140-220 DEG C x The removal rate can maintain the NOx removal rate of more than 80% in the temperature range of 100-300 ℃, and the excellent NO of 97.7% can be realized at the temperature of 100 DEG C x The removal rate is further improved compared with the Zr-2 catalyst in the activity of the low temperature section.
NH with different modified catalysts 3 SCR activity longitudinal comparison, the results of which are shown in figure 3.
As can be seen from FIG. 3, it can be seen from a longitudinal comparison that Zr is substituted for the metal modification alone to LaMnO 3 NH of catalyst 3 The activity of the catalyst is obviously improved in the middle and high temperature after the Zr is substituted and modified, and the improvement effect of the low temperature section is relatively weaker; the denitration efficiency of the catalyst is remarkably improved after Zr-F co-modification, and the activity of the catalyst at low temperature and medium and high temperature is superior to that of the catalyst Zr-2.
N for different modified catalysts 2 The selectivity test is shown in fig. 4.
As can be seen from FIG. 4, compared with LaMnO 3 Catalyst, and N of catalyst Zr-2 after A-site Zr substitution modification 2 The selectivity is obviously reduced in<Can maintain more than 65% of N at 200 DEG C 2 Selectivity is worse after temperature rise, and Zr-F co-modified Zr-2-F-1.6 catalyst to N 2 Selectivity ofAnd is lifted. This illustrates that Zr replaces the metal modification alone on catalyst N 2 Selectivity has an adverse effect, while Zr-F co-modification is specific to N of the catalyst 2 The selectivity has a lifting effect.
The sulfur resistance and water resistance tests were performed on different modified catalysts as shown in fig. 5.
As can be seen from FIG. 5, compared with LaMnO 3 The catalyst, namely the catalyst Zr-2 after A-site Zr substitution modification, has excellent sulfur resistance and water resistance, and is 100ppm SO 2 And 10vol% H 2 In the presence of O, 99% of NO can be maintained x The removal rate is increased, and the activity performance is still stable with the time; the catalyst still shows very excellent SO after Zr-F co-modification 2 /H 2 O resistance.
XRD analysis was performed on the different modified catalysts as shown in figure 6.
As can be seen from FIG. 6, laMnO 3 After the catalyst is modified by Zr substitution and Zr-F co-modified, the catalyst still shows LaMnO 3 Diffraction peaks of (PDF # 54-1257), which indicate that the catalysts all formed perovskite crystal structures, also indicate that the catalysts obtained by the citric acid-sol gel preparation process have good structural stability.
XPS analysis was performed on different modified catalysts as shown in FIG. 7.
As can be seen from FIG. 7, mn 2p 3/2 The XPS spectrum of the orbit can find that the active component Mn in the catalyst is Mn 2+ ，Mn 3+ And Mn of 4+ In the form of polyvalent states and the catalysts Mn 4+ The relative content of (2) is closely related to the catalytic activity thereof; from the XPS spectrum of the O1s orbital, it was found that the active oxygen species on the catalyst surface include lattice oxygen (O latt ) And oxygen (O) adsorption ads ) They are together NH 3 The SCR reaction continues to supply active oxygen species.
H for different modified catalysts 2 -TPR、NH 3 -TPD、O 2 TPD, NO-TPD analysis, as shown in FIG. 8. Wherein, in the abcd diagram in FIG. 8, zr-2-F-1.6, zr-2 and LM-1 are sequentially arranged from top to bottom.
As can be seen from fig. 8, by H 2 TPR can find that the reduction peak area of the catalyst Zr-2 after Zr substitution modification is increased, which shows that the oxidation-reduction capability is obviously enhanced; the catalyst after co-modification with Zr-F showed similar reduction behavior to Zr-2 but shifted its temperature to low temperature, which suggests that the redox performance of the catalyst after F doping was enhanced, which is also the main reason that the catalyst Zr-2-F-1.6 had excellent denitration activity. By NH 3 TPD can be found that Zr is substituted for NH of the modified catalyst Zr-2 3 The desorption peak area is obviously increased, especially the NH at the low temperature section 3 The desorption amount of (2) is obviously improved, which indicates that Zr doping improves the adsorption activation capability of the catalyst surface to NH 3. The catalyst also shows good surface acidity after Zr-F co-modification, and the catalyst Zr-2-F-1.6 still has obvious NH in different temperature sections 3 Desorption peak. Through O 2 TPD can be found that Zr is substituted for O of the modified catalyst Zr-2 2 The desorption peak area is obviously reduced, especially O in the low-temperature section 2 The desorption peak is very small, which indicates that the adsorption activation capability of the surface of the catalyst to oxygen species is weakened after Zr doping modification. The adsorption activation capability of the Zr-F co-modified catalyst Zr-2-F-1.6 to oxygen species is enhanced compared with that of single Zr modification, and O of two corresponding temperature sections 2 The desorption peak area is increased, which indicates that F doping is favorable for improving the adsorption and activation of the catalyst to oxygen, thereby leading the catalyst to show excellent N with denitration activity 2 Selectivity. The NO desorption peak area of the catalyst Zr-2 after Zr substitution modification is reduced to a certain extent, and the desorption temperature of the catalyst shifts towards a high Wen Fangxiang, so that the adsorption activation capability of the surface of the catalyst after Zr doping to NO is reduced; the NO desorption peak areas of the Zr-2-F-1.6 catalyst in the low temperature and high temperature sections after Zr-F co-modification are increased compared with that of the single Zr modification, which shows that F doping can effectively improve the adsorption performance of the catalyst surface so as to be beneficial to the processes of adsorption, activation and the like of reactant molecules in the reaction, and is also just that the Zr-F co-modification series catalyst is in NH 3 The reason for the excellent performance in SCR reactions.
From the above, it was found by longitudinal comparative analysis that Zr was substituted and modifiedF Co-modification of LaMnO 3 NH of catalyst 3 The SCR activity has a certain effect of increasing. NH of catalyst after Zr substitution modification 3 SCR activity and SO 2 /H 2 Excellent O resistance, N 2 The selectivity was significantly reduced, indicating that for LaMnO 3 The catalyst can effectively improve NH by carrying out A-site metal substitution 3 SCR activity, however for N 2 Selectivity is not promoting. Zr and F metal nonmetal co-modified LaMnO 3 NH of catalyst 3 -SCR activity, N 2 Selectivity and SO 2 /H 2 The O resistance is significantly enhanced, which suggests that metal and nonmetal co-modification is feasible for increasing perovskite-type denitration activity. The A-site Zr substitution enhances the surface acid amount and redox capacity but reduces the surface Mn 4+ The Zr-F co-modified catalyst enhances the surface acid amount and redox capacity, thereby rendering the Zr-F co-modified catalyst superior to the A or Zr doped catalyst.
Although specific embodiments of the invention have been described in detail with reference to the accompanying drawings, it should not be construed as limiting the scope of protection of the present patent. Various modifications and variations which may be made by those skilled in the art without the creative effort are within the scope of the patent described in the claims.
Claims (8)
1. The metal-nonmetal co-modified low-temperature SCR denitration catalyst is characterized by comprising the following components: a primary base catalyst, a metal active component for metal modification, and a nonmetal active component for nonmetal modification;
the original substrate catalyst is perovskite LaMnO 3 The catalyst comprises a metal active component, a nonmetal active component and a catalyst, wherein the metal active component is Zr, and the nonmetal active component is F;
the substitution amount of the metal active component Zr to the A-site ion La in the original substrate catalyst is 20%, and the mass percentage of the nonmetal active component F is 1.6%; the metal active component Zr is introduced through a citric acid-sol gel method to partially replace A-site ions La in the original substrate catalyst.
2. The metal-nonmetal co-modified low temperature SCR denitration catalyst as claimed in claim 1, wherein the nonmetal active component F is introduced by an impregnation method, and is supported on the original base catalyst.
3. The method for preparing the metal-nonmetal co-modified low-temperature SCR denitration catalyst as claimed in any one of claims 1 to 2, which is characterized by comprising the following steps:
(1) Respectively weighing lanthanum nitrate, zirconium nitrate and manganese nitrate, then adding citric acid and adding deionized water for dissolution to obtain a mixed solution;
(2) Dropwise adding ammonia water into the mixed solution obtained in the step (1) under the stirring condition, regulating the pH value to 8, then heating in a water bath under the conditions of 90 ℃ and magnetic stirring, evaporating to dryness to obtain gel, and then roasting the gel in a gradient manner after the gel is dried to obtain a catalyst Zr-2;
(3) Dissolving ammonium fluoride with deionized water, then placing the catalyst Zr-2 obtained in the step (2) into the deionized water for ultrasonic impregnation for 2 hours, drying, roasting, and then sequentially tabletting and sieving to obtain the metal-nonmetal co-modified low-temperature SCR denitration catalyst.
4. The method for preparing a metal-nonmetal co-modified low-temperature SCR denitration catalyst as claimed in claim 3, wherein in the step (1), the molar ratio of lanthanum nitrate, zirconium nitrate and manganese nitrate is 0.6-1:0.1-0.3:1.
5. The method for preparing a metal-nonmetal co-modified low-temperature SCR denitration catalyst as claimed in claim 3, wherein in the step (1), the molar ratio of metal ions to citric acid in the mixed solution is 1:1-3.
6. The method for preparing a metal-nonmetal co-modified low temperature SCR denitration catalyst as claimed in claim 3, wherein in the step (2), the catalyst is dried at 120 ℃ for 24 hours.
7. The method for preparing a metal-nonmetal co-modified low-temperature SCR denitration catalyst as claimed in claim 3, wherein in the step (2), the catalyst is baked at 400-500 ℃ and 800-900 ℃ for 2-4 hours respectively, and the heating rate is 5 ℃/min.
8. The method for preparing a metal-nonmetal co-modified low temperature SCR denitration catalyst as claimed in claim 3, wherein in step (3), the catalyst is dried at 80 ℃ for 24 hours.
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