CN115090305A - 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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- 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
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- 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
- 238000000034 method Methods 0.000 claims description 9
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Abstract
The invention provides a metal-nonmetal co-modified low-temperature SCR denitration catalyst and a preparation method thereof, and the metal-nonmetal co-modified low-temperature SCR denitration catalyst comprises the following components: the catalyst comprises an original substrate 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 Zr as a metal active component and F as a nonmetal active component. The invention also comprises a preparation method of the denitration catalyst. The catalyst has a perovskite crystal structure, has good thermal stability and uniformity, and effectively solves the problem 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 derived from fossil fuel combustion x Pollution harms human health, NH 3 The SCR technology is one of the most widely and mature flue gas denitration technologies in commercial use at present, and the core of the SCR technology is NH 3 -selection of SCR catalyst. Although the traditional noble metal catalyst has good denitration activity, the price is high, and the sulfur resistance performance is poor; the V-W-Ti catalyst is the most widely commercially applied denitration catalyst at present, has excellent high-temperature activity and sulfur resistance and water resistance, but has narrow temperature window and poor low-temperature activity, is difficult to adapt to the complex conditions of flue gas emission in industries such as coking, smelting and the like, and has limited practical application.
Manganese-based catalysts are of particular interest for their excellent redox performance, multiple valence state and good low temperature activity, but they suffer from the disadvantages of narrow temperature window, poor sulfur resistance, etc. Research shows that the perovskite crystal structure formed by structure regulation in the preparation process of the catalyst can improve the characteristics of the catalyst such as surface adsorption performance, structure stability, uniformity and the like, and the physical and chemical properties and the surface characteristics of the catalyst can be further improved by doping metal and nonmetal, so that the catalyst with high low-temperature NH is constructed 3 SCR activity, wide temperature window, high resistance denitration catalyst provide a feasible 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, the obtained catalyst has a perovskite crystal structure, has good thermal stability and uniformity, and effectively solves the problem 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 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: the catalyst comprises an original substrate catalyst, a metal active component for metal modification and a nonmetal active component for nonmetal modification;
originalThe substrate catalyst is perovskite LaMnO 3 The catalyst comprises Zr as a metal active component and F as a nonmetal active component.
Further, the substitution amount of the metal active component Zr for 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, partially replacing the a site ion La in the original base catalyst.
Further, the non-metal active component F is introduced by an impregnation method and is loaded on the original substrate catalyst.
The preparation method of the metal-nonmetal co-modified low-temperature SCR denitration catalyst comprises the following steps:
(1) respectively weighing lanthanum nitrate, zirconium nitrate and manganese nitrate, then adding citric acid and adding deionized water for dissolving to obtain a mixed solution;
(2) dropwise adding ammonia water into the mixed solution obtained in the step (1) under the stirring condition, adjusting the pH value to 8, then heating the mixed solution in a water bath at 90 ℃ under the magnetic stirring condition, evaporating to dryness to obtain gel, drying the gel, and then carrying out gradient roasting to obtain a catalyst Zr-2;
(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, roasting, and then sequentially tabletting and screening 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 to zirconium nitrate to 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), drying is carried out at a temperature of 120 ℃ for 24 hours.
Further, in the step (2), the sintering is carried out at 500 ℃ and 900 ℃ of 400 and 800 respectively for 2-4h, and the heating rate is 5 ℃/min.
Further, in the step (2), the mixture is respectively roasted for 3h at 450 ℃ and 850 ℃ with the heating rate of 5 ℃/min.
Further, in the step (3), drying is carried out at a temperature of 80 ℃ for 24 hours.
Further, in the step (3), the size is 20-40 meshes during screening.
In summary, the invention has the following advantages:
1. the catalyst Zr-2-F-1.6 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 problem 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 obtained catalyst Zr-2-F-1.6 and unmodified LaMnO 3 Compared with the Zr-2 catalyst modified by single Zr, the specific surface area, the surface adsorbed oxygen content and the surface acidity of the catalyst are obviously enhanced, and the catalyst shows excellent low-temperature NH 3 SCR denitration Activity and Wide temperature Window, Sulfur and Water resistance and N 2 The selectivity is obviously improved. And the preparation process is stable and easy to implement, and has low requirements on instruments and equipment.
3. The target catalyst is synthesized by two steps of a citric acid-sol-gel method and an impregnation method, the obtained catalyst has an excellent perovskite crystal structure, excellent texture performance and surface activity, the preparation process is stable and easy to implement, and the catalyst 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, 100% NO in the temperature range of 140 ℃ and 220 ℃ x The removal rate can reach more than 80 percent of NO within the temperature range of 100-300 DEG C x The removal rate is high, and more than 97 percent of NO can be realized under the low-temperature condition of 100 DEG C x The removal rate; in addition, the 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 10 vol% H 2 The NO can still maintain 99 percent under the condition of the simultaneous existence of O x And (4) removing rate.
Drawings
FIG. 1 shows NH of Zr-substituted modified series catalysts alone in different ratios 3 -SCR activity map;
FIG. 2 shows NH of Zr-F co-modified series catalysts with different F doping ratios 3 -SCR activity map;
FIG. 3 shows NH of various modified catalysts 3 -a longitudinal map of SCR activity;
FIG. 4 is a graph of the N2 selectivity for different modified catalysts;
FIG. 5 is a graph of long-term sulfur resistance versus water resistance for various modified catalysts;
FIG. 6 is an XRD pattern of different modified catalysts;
FIG. 7 is an XPS plot of different modified catalysts;
FIG. 8 is a TPR/TPD plot of different modified catalysts.
Detailed Description
Example 1
Substrate catalyst LaMnO 3 Preparation of
Weighing a certain amount of precursor lanthanum nitrate and manganese nitrate, adding a certain amount of citric acid, and dissolving the mixture 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 to manganese nitrate, was 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 gradually and gradually added into the solution and continuously stirred until the pH value of the solution is about 8; heating the solution with the adjusted pH value in a water bath kettle at 90 ℃, magnetically stirring, and evaporating to remove water to form gel; drying the gel at 120 ℃ for 24h, and then performing gradient roasting under the conditions of roasting at 450 ℃ for 3h and roasting at 750 ℃ for 3h in air atmosphere at the heating rate of 5 ℃/min to obtain primary LaMnO 3 A powdered catalyst; tabletting and screening the powdery catalyst to obtain the final 20-40 mesh granular target catalyst named as LM-1.
With LaMnO 3 Catalyst-based preparation of A-site Zr substituted single metal modified catalyst
Weighing a certain amount of precursors of lanthanum nitrate, zirconium nitrate and manganese nitrate, adding a certain amount of citric acid, and dissolving with a proper amount of deionized water to obtain a solution of 0.2-0.4 mol/L; molar ratio of each precursor, (lanthanum nitrate + zirconium nitrate): manganese nitrate 1:1, and molar ratio of total metal ions in the solution to citric acid 1:2, wherein the substitution amounts of Zr for La ions at a position are 0.1, 0.2, 0.3, 0.5, respectively. Ammonia water is used as a pH regulator, and is gradually and gradually added into the solution and continuously stirred until the pH value of the solution is about 8; heating the solution with the adjusted pH value in a water bath kettle at 90 ℃, magnetically stirring, and evaporating water to form gel; drying the gel at 120 ℃ for 24h, and then performing gradient roasting under the conditions of roasting at 450 ℃ for 3h and roasting at 850 ℃ for 3h in air atmosphere at the heating rate of 5 ℃/min to obtain primary Zr substituted modified LaMnO 3 A powdered catalyst; the powdery catalyst is tabletted 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 substituted modified LaMnO 3 The preparation method of the metal-nonmetal co-modified low-temperature SCR denitration catalyst is used for preparing the F-doped Zr-F co-modified catalyst on the basis of the 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 dissolving to obtain a mixed solution; lanthanum nitrate, zirconium nitrate and manganese nitrate are 0.8:0.2:1, the molar ratio of total metal ions to citric acid in the solution is 1:2, and the substitution amount of Zr for La ions at the A position is 0.2;
(2) dropwise adding ammonia water into the mixed solution obtained in the step (1) under the stirring condition, adjusting the pH value to 8, then heating the mixed solution in a water bath at 90 ℃ under the magnetic stirring condition, drying the mixed solution by evaporation to obtain gel, drying the gel at 120 ℃ for 24 hours, roasting the gel at 450 ℃ for 3 hours and roasting the gel at 850 ℃ for 3 hours, wherein the heating rate is 5 ℃/min, and obtaining a catalyst Zr-2; 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 2h, drying for 24h at 80 ℃, roasting for 2h at 360 ℃, and then sequentially tabletting and screening (20-40 meshes) to obtain the metal-nonmetal co-modified low-temperature SCR denitration catalyst. According to the different doping amount of F, the obtained catalysts are respectively named as Zr-2-F-0.8, Zr-2-F-1.2, Zr-2-F-1.6 and Zr-2-F-2.0.
Examples of the experiments
Evaluation of NH of catalyst by fixed bed reactor 3 -SCR activity. The reactor is a quartz tube with the inner diameter of 14mm, and a thermocouple and a tubular electric furnace are used for regulating and controlling the temperature; the test temperature range is 80-300 ℃, the heating rate is 5 ℃/min, every 20 ℃ is taken as a temperature point, each temperature point stays for 30min, and data are recorded. The simulated smoke gas is 500ppmNO and 500ppmNH 3 ，5％O 2 And N 2 As balance gas, the total gas flow is 500ml/min, and the space velocity is 30000h -1 The filling volume of the catalyst is 1 mL; the concentration of NO before and after reaction is detected in real time by a flue gas analyzer (Gasboard-3000), and NO are detected in real time by an on-line infrared flue gas analyzer (Antaris IGS) 2 、N 2 O、NH 3 The concentration of (2). 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 pair SO was tested using a fixed bed reactor 2 And H 2 And (4) resistance to O. Long period anti-SO 2 /H 2 In the O-test, the temperature is 200 ℃, and the simulated smoke comprises 500ppmNO and 500ppmNH 3 ，100ppmSO 2 ，5％O 2 ，10vol％H 2 O and N 2 As balance gas, the total gas flow is 500ml/min, and the reaction space velocity is 30000h -1 。
NH is carried out on single Zr substituted modified series catalysts with different proportions 3 SCR activity test found that Zr-2 catalyst with a Zr substitution of 0.2 had the best denitration activity, as shown in FIG. 1.
As can be seen from FIG. 1, the Zr-2 catalyst can reach 100% NO at the temperature range of 140 ℃ and 220 DEG C x Removal rate, and 80% NO thereof x The temperature interval corresponding to the removal rate is also 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 the F doping amount of 1.6 percent has the best denitration activity by doping the non-metal component F with different proportions for modification, as shown in figure 2.
As can be seen from FIG. 2, the catalyst Zr-2-F-1.6 can reach 100% NO within the temperature range of 140 ℃ and 220 DEG C x The removal rate can maintain more than 80 percent of NOx removal rate in the temperature range of 100-300 ℃, and 97.7 percent of excellent NO can be realized at the temperature of 100 DEG C x The removal rate is further improved compared with the activity of the Zr-2 catalyst at a low temperature section.
By modification of NH of the catalyst 3 SCR activity longitudinal comparison, the results of which are shown in FIG. 3.
As can be seen from FIG. 3, the longitudinal comparison shows that Zr replaces the single metal modification pair LaMnO 3 NH of the catalyst 3 The SCR activity is obviously improved, the medium and high temperature activity of the catalyst is obviously improved after Zr replaces and is modified, and the improvement effect of a low-temperature section is relatively weaker; the denitration efficiency of the Zr-F co-modified catalyst is improved more remarkably, and the low-temperature and medium-high temperature activity of the Zr-F co-modified catalyst is superior to that of the Zr-2 catalyst.
N on different modified catalysts 2 Selectivity test, as shown in figure 4.
As can be seen from FIG. 4, the phase ratio of LaMnO is higher than that of LaMnO 3 Catalyst, N of Zr-2 after the substitution of Zr at A site 2 The selectivity is obviously reduced in<Can maintain more than 65% of N at the temperature of 200 DEG C 2 Selectivity, which is worse after temperature increase, and Zr-2-F-1.6 catalyst after Zr-F co-modification to N 2 The selectivity is also improved. This demonstrates Zr substitution for the sole metal modification of catalyst N 2 The selectivity has an adverse effect, while the Zr-F co-modification has an adverse effect on the N of the catalyst 2 Selectivity isHas the function of lifting.
Sulfur resistance water resistance tests were performed on the different modified catalysts as shown in fig. 5.
As can be seen from FIG. 5, the phase ratio of LaMnO is higher than that of LaMnO 3 The sulfur resistance and water resistance of the catalyst Zr-2 after the substitution and modification of the Zr at the A position are very excellent and the SO content is 100ppm 2 And 10 vol% H 2 The NO can still maintain 99 percent under the condition of the simultaneous existence of O x The removal rate is high, and the activity performance is stable as time goes on; the Zr-F co-modified catalyst still shows very excellent SO 2 /H 2 And (4) resistance to O.
XRD analysis was performed on the different modified catalysts as shown in fig. 6.
As can be seen from FIG. 6, LaMnO 3 After the catalyst is subjected to Zr substitution modification and Zr-F co-modification, the catalyst still shows LaMnO 3 (PDF #54-1257), which indicates that the catalysts all formed perovskite crystal structures, and also indicates that the catalyst prepared by the citric acid-sol gel method has good structural stability.
XPS analysis was performed on the different modified catalysts as shown in figure 7.
As can be seen from FIG. 7, Mn 2p 3/2 XPS spectrum of the orbit can find that the active component Mn in the catalyst is Mn 2+ ，Mn 3+ And Mn 4+ In a multi-valent state and each catalyst Mn 4+ The relative content of (a) is closely related to its catalytic activity; from XPS spectrum of O1s orbital, active oxygen species on the surface of the catalyst can be found to include lattice oxygen (O) latt ) And adsorbing oxygen (O) ads ) Which together are NH 3 The SCR reaction continues to supply reactive 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 of FIG. 8, Zr-2-F-1.6, Zr-2 and LM-1 are sequentially arranged from top to bottom.
From FIG. 8, the diagram shows the formula H 2 TPR can find that the reduction peak area of the Zr-2 catalyst after Zr substitution modification is increased, which shows that the oxidation-reduction capability of the catalyst is obviously enhanced; catalyst performance after Zr-F co-modificationThe reduction behavior similar to that of Zr-2 was exhibited but the temperature was shifted toward a low temperature, indicating that the redox performance of the catalyst was enhanced after F doping, which is also the main reason why the catalyst Zr-2-F-1.6 had excellent denitration activity. By NH 3 TPD it was found that Zr replaces NH of the modified catalyst Zr-2 3 The desorption peak area is obviously increased, especially the low-temperature NH 3 The desorption amount of (a) is obviously improved, which shows that the Zr doping enables the adsorption activation capacity of the catalyst surface to NH3 to be improved. The catalyst shows good surface acidity after being subjected to Zr-F co-modification, and significant NH still appears in the catalyst Zr-2-F-1.6 at different temperature ranges 3 Desorption peak. By O 2 TPD it was found that Zr substituted the O of the modified catalyst Zr-2 2 The desorption peak area is obviously reduced, especially the O of a low-temperature section 2 The desorption peak was very small, indicating that the adsorption activation capacity of the Zr doped modified catalyst surface for oxygen species was reduced. 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 the Zr modification alone, and O of the corresponding two temperature sections 2 The desorption peak areas are increased, which shows that the F doping is favorable for promoting the adsorption and activation of the catalyst on oxygen, so that the catalyst shows excellent denitration activity 2 And (4) selectivity. The NO-TPD can find that the NO desorption peak area of the Zr-2 catalyst after Zr substitution and modification is reduced to a certain extent, and the desorption temperature shifts towards the high temperature direction, which shows that the NO adsorption and activation capacity of the Zr-doped catalyst surface is reduced; the NO desorption peak areas of Zr-2-F-1.6 of the Zr-F co-modified catalyst in the low-temperature and high-temperature sections are increased compared with those of single Zr modification, which shows that the F doping can effectively improve the surface adsorption performance of the catalyst so as to be beneficial to the processes of adsorption, activation and the like of reactant molecules in the reaction, and the process is also the NH of the Zr-F co-modified series catalyst 3 The reason for the excellent performance in the SCR reaction is.
In summary, it can be seen from the longitudinal comparative analysis that the Zr substitution modification and the Zr-F co-modification are applied to LaMnO 3 NH of the catalyst 3 SCR activity has certain promotion effect. Zr substituted NH of modified catalyst 3 SCR activity and SO 2 /H 2 Excellent in O resistance, N 2 The selectivity is obviously reduced, which shows that the target value is to LaMnO 3 The catalyst can effectively improve NH by substituting metal at A position 3 SCR activity, however on N 2 Selectivity is not promoting. LaMnO obtained after Zr and F metal nonmetal co-modification 3 NH of catalyst 3 -SCR activity, N 2 Selectivity and SO 2 /H 2 The O resistance is obviously enhanced, which shows that the co-modification of metal and nonmetal is feasible for improving the perovskite denitration activity. Zr substitution at the A site enhances surface acid content and redox capability but reduces surface Mn 4+ The Zr-F co-modified catalyst enhances the surface acid amount and the oxidation reduction capability, so that the Zr-F co-modified catalyst is better than the A or Zr doped catalyst.
While the embodiments of the invention have been described in detail in connection with the drawings, the invention should not be construed as limited to the scope of the patent. Various modifications and changes may be made by those skilled in the art without inventive step within the scope of the appended claims.
Claims (10)
1. The metal-nonmetal co-modified low-temperature SCR denitration catalyst is characterized by comprising the following components: the catalyst comprises an original substrate 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 Zr and a nonmetal active component F.
2. The metal-nonmetal co-modified low-temperature SCR denitration catalyst of claim 1, wherein the substitution amount of the metal active component Zr for 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%.
3. The metal-nonmetal co-modified low-temperature SCR denitration catalyst of claim 1, wherein the metal active component Zr is introduced by a citric acid-sol gel method to partially replace a-site ion La in the original base catalyst.
4. The metal-nonmetal co-modified low-temperature SCR denitration catalyst of claim 1, wherein the nonmetal active component F is introduced by an impregnation method and supported on the original base catalyst.
5. The preparation method of the metal-nonmetal co-modified low-temperature SCR denitration catalyst of any one of claims 1 to 4, 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 dissolving to obtain a mixed solution;
(2) dropwise adding ammonia water into the mixed solution obtained in the step (1) under the stirring condition, adjusting the pH value to 8, then heating the mixed solution in a water bath at 90 ℃ under the magnetic stirring condition, evaporating to obtain gel, drying the gel, and then carrying out gradient roasting to obtain a catalyst Zr-2;
(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, roasting, and then sequentially tabletting and screening to obtain the metal-nonmetal co-modified low-temperature SCR denitration catalyst.
6. The preparation method of the metal-nonmetal co-modified low-temperature SCR denitration catalyst of claim 5, 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.
7. The method for preparing the metal-nonmetal co-modified low-temperature SCR denitration catalyst of claim 5, wherein in the step (1), the molar ratio of the metal ions to the citric acid in the mixed solution is 1: 1-3.
8. The method for preparing a metal-nonmetal co-modified low-temperature SCR denitration catalyst according to claim 5, wherein the drying is performed at 120 ℃ for 24 hours in the step (2).
9. The method for preparing the metal-nonmetal co-modified low-temperature SCR denitration catalyst as defined in claim 5, wherein in the step (2), the catalyst is calcined at 500 ℃ and 900 ℃ respectively for 2-4h at a temperature rising rate of 5 ℃/min.
10. The method for preparing the metal-nonmetal co-modified low-temperature SCR denitration catalyst of claim 5, wherein in the step (3), the drying is performed at a temperature of 80 ℃ for 24 hours.
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