CN113617380A - Preparation method of HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst - Google Patents

Preparation method of HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst Download PDF

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CN113617380A
CN113617380A CN202110944233.7A CN202110944233A CN113617380A CN 113617380 A CN113617380 A CN 113617380A CN 202110944233 A CN202110944233 A CN 202110944233A CN 113617380 A CN113617380 A CN 113617380A
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张洪亮
黄�俊
任志祥
陈环
丁龙
龙红明
魏进超
王光应
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Anhui University of Technology AHUT
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    • B01J29/04—Catalysts comprising molecular sieves having base-exchange properties, e.g. crystalline zeolites
    • B01J29/06—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof
    • B01J29/40—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively
    • B01J29/405—Crystalline aluminosilicate zeolites; Isomorphous compounds thereof of the pentasil type, e.g. types ZSM-5, ZSM-8 or ZSM-11, as exemplified by patent documents US3702886, GB1334243 and US3709979, respectively containing rare earth elements, titanium, zirconium, hafnium, zinc, cadmium, mercury, gallium, indium, thallium, tin or lead
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Abstract

The invention discloses a preparation method of a high-performance cerium-based denitration catalyst modified by an HZSM-5 molecular sieve, and relates to the technical field of pollution treatment of atmospheric nitrogen oxides. The preparation method of the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst comprises the steps of mixing the HZSM-5 molecular sieve and cerium nitrate hexahydrate, grinding the mixture until the mixture is free from particle sense, roasting and activating the mixture in a flowing air atmosphere, keeping the cubic fluorite structure of the obtained cerium dioxide unchanged, and simultaneously preparing the HZSM-5 molecular sieve modified cerium-based catalytic material with increased surface lattice defects, wherein a solvent is not used in the preparation process, so that the loss of active species is effectively avoided. Compared with the existing acid auxiliary agent modified cerium-based catalyst, the catalyst has the nitrogen oxide conversion rate of more than 80% within the range of 250-400 ℃, the denitration efficiency is obviously improved, the risk of secondary pollution is reduced, and the application field of the HZSM-5 molecular sieve in the denitration catalyst is expanded.

Description

Preparation method of HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst
Technical Field
The invention relates to the technical field of pollution control of atmospheric nitrogen oxides, in particular to a preparation method of a high-performance cerium-based denitration catalyst modified by an HZSM-5 molecular sieve.
Background
At present, NO in ChinaxThe emissions are carried out with the most stringent emission limits worldwide, ammonia selective catalytic reduction of nitrogen oxides (NH)3SCR) is an effective technology that can meet ultra-low emission limits. The vanadium tungsten titanium catalyst for commercial application has higher operation temperature, vanadium has biotoxicity and SO2The catalyst is easy to be poisoned and inactivated, so that the development of a novel high-efficiency denitration catalyst capable of meeting various complex conditions is urgently needed.
At NH3In the SCR reaction, the redox and surface acidity of the catalyst are decisive factors influencing the catalytic activity. CeO (CeO)2Has excellent oxidation-reduction performance and good Ce3+/Ce4+Conversion capacity, but for pure CeO2The surface acidity of (a) is relatively weak and the thermal stability is poor, so that the denitration efficiency is low. Molecular sieves and modified molecular sieves are considered to be denitration catalysts with practical application prospects due to excellent catalytic activity and selectivity. Among them, a catalyst system in which various transition metals are supported on a ZSM-5 molecular sieve has attracted particular attention. The hydrogen form of HZSM-5 is a derivative of ZSM-5 and is commonly used as a support for industrial solid catalysts due to its relatively suitable pore structure and acid properties. Currently, ion-doped HZSM-5 molecular sieve catalysts are widely used for fixed and mobile source NH3In the SCR reaction system, however, due to the small size of the HZSM-5 molecular sieve pore channel, the doped ions are difficult to be uniformly distributed on the surface of the inner hole in the preparation process,so that the adjustment of the ion doping to the acid performance is not easy to control; in addition, excessive doping of ions can block the pore channels, so that the specific surface area and the pore volume of the modified molecular sieve are reduced, the contact reaction of reactants and an active center and the diffusion of products are not facilitated, and the modification effect by ion doping is limited. NH (NH)3The research on SCR catalysts involves conventional medium-high temperature denitration as well as novel low temperature denitration, and cerium-based catalysts show good denitration activity under laboratory conditions, but are a certain distance away from the level of industrial application.
Disclosure of Invention
1. Technical problem to be solved by the invention
Aiming at the problems that the denitration efficiency of a cerium oxide catalyst in the prior art is low, large-scale preparation is not easy to realize and the like, the invention provides a preparation method of a high-performance cerium-based denitration catalyst modified by an HZSM-5 molecular sieve, wherein the HZSM-5 molecular sieve and cerium nitrate hexahydrate are mixed and ground until no particle sense exists, and the mixture is roasted and activated in a flowing air atmosphere to obtain a cerium dioxide modified cerium-based catalytic material with the HZSM-5 molecular sieve, wherein the cubic fluorite structure of the cerium dioxide is kept unchanged, and the surface lattice defects are increased; the preparation process does not use solvent, is simple and convenient to operate and can be used for large-scale preparation.
2. Technical scheme
In order to achieve the purpose, the technical scheme provided by the invention is as follows:
a preparation method of a high-performance cerium-based denitration catalyst modified by an HZSM-5 molecular sieve comprises the steps of mixing the HZSM-5 molecular sieve with cerium nitrate hexahydrate, grinding until no particle sense exists, roasting and activating in a flowing air atmosphere, and keeping a cubic fluorite structure of the obtained cerium dioxide unchanged, wherein the surface lattice defects of the obtained HZSM-5 molecular sieve are increased. The preparation process does not use a solvent, can effectively avoid the loss of active species, has the advantages of high yield, environmental friendliness, simple process, low preparation cost and the like, and is suitable for large-scale production; more importantly, the structural order of the mechanically ground catalyst is destroyed, the surface lattice defect of the cerium dioxide is increased, the formation of oxygen vacancy is facilitated, the catalytic activity is improved, and the adhesion and agglomeration of the catalyst are prevented.
According to a further technical scheme, when the HZSM-5 molecular sieve and the cerous nitrate hexahydrate are mixed, the HZSM-5 molecular sieve comprises the following components in percentage by mass: 5 wt% -30 wt%. The results of ammonia temperature programmed desorption experiments show that the cerium oxide is mixed with pure cerium dioxide (CeO)2) Compared with the prior art, the total acid amount on the surface of the modified cerium-based catalyst is also obviously increased along with the increase of the load of the HZSM-5, and the result shows that the HZSM-5 serving as a solid acid can obviously improve the surface acidity of the cerium-based catalyst, so that the reaction activity is improved. Therefore, the HZSM-5 molecular sieve is used as a solid acid auxiliary agent, which can provide more acid sites and acid strength and make up for pure CeO2In the selective catalytic reduction of nitrogen oxides (NH) in ammonia3-SCR) is weak in acidity, and the denitration efficiency of the SCR denitration catalyst in the prior art at 250-400 ℃ is improved, so that the application field of the HZSM-5 molecular sieve in the denitration catalyst is expanded.
According to a further technical scheme, the preparation of the cerium dioxide catalyst powder specifically comprises the following steps:
step one, preparing a powder precursor: weighing 40g of cerium nitrate hexahydrate in an agate mortar, grinding the mixture for 20min, spreading the mixture in a crucible, then putting the crucible into a muffle furnace to roast the mixture in a flowing air atmosphere, wherein the roasting temperature of the muffle furnace is 520-550 ℃, the heating rate is 2 ℃/min, the roasting time is 5-5.5 h, and cooling the mixture to room temperature to obtain CeO2A catalyst powder;
step two, roasting and activating the precursor: uniformly spreading the ground precursor powder in a crucible, and then roasting in a muffle furnace;
step three, powder collection: cooling along with the furnace after the roasting is finished to obtain pure CeO2A catalyst powder.
In a further technical scheme, the preparation of the HZSM-5 molecular sieve modified cerium dioxide catalyst specifically comprises the following steps:
step one, preparing a powder precursor: respectively weighing cerium nitrate hexahydrate and an HZSM-5 molecular sieve in an agate mortar, and grinding into precursor powder without granular sensation;
step two, roasting and activating the precursor: uniformly spreading the ground precursor powder in a crucible, and then roasting in a muffle furnace;
step three, powder collection: cooling along with the furnace after roasting is finished to obtain HZSM-5/CeO2A catalyst powder.
The further technical scheme is that in the step one, HZSM-5/CeO is prepared2The catalyst is prepared from HZSM-5 and CeO2The mass ratio is 1: 19-3: 7, preparing cerium nitrate hexahydrate according to a cerium element molar ratio of 1: 1, accurately weighing.
According to a further technical scheme, in the second step, the roasting atmosphere is flowing air, the temperature is increased from room temperature to 520-550 ℃ at the temperature increase speed of 2 ℃/min, and then the temperature is kept within the temperature range for 5-5.5 h and then the temperature is naturally reduced.
A preparation method of an HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst relates to a chemical reaction equation as follows:
Figure BDA0003216063500000031
Figure BDA0003216063500000032
Figure BDA0003216063500000033
Figure BDA0003216063500000034
3. advantageous effects
Compared with the prior art, the technical scheme provided by the invention has the following beneficial effects:
(1) the invention relates to a preparation method of a high-performance cerium-based denitration catalyst modified by an HZSM-5 molecular sieve, which is characterized in that the HZSM-5 molecular sieve and cerium nitrate hexahydrate are mixed and ground to have no granular sensation, and are roasted and activated in a flowing air atmosphere to obtain a cerium dioxide which keeps a cubic fluorite structure unchanged and is a HZSM-5 molecular sieve modified cerium-based catalytic material with increased surface lattice defects; the preparation process does not use a solvent, can effectively avoid the loss of active species, has the advantages of high yield, environmental friendliness, simple process, low preparation cost and the like, and is suitable for large-scale production; more importantly, the structural order of the mechanically ground catalyst is destroyed, the surface lattice defect of the cerium dioxide is increased, the formation of oxygen vacancy is facilitated, the catalytic activity is improved, and the adhesion and agglomeration of the catalyst are prevented;
(2) the invention discloses a preparation method of a high-performance cerium-based denitration catalyst modified by an HZSM-5 molecular sieve, wherein the HZSM-5 molecular sieve comprises the following components in percentage by mass: 5 wt% -30 wt%, compared with pure cerium dioxide, the total acid content of the modified cerium-based catalyst surface is also increased along with the increase of the HZSM-5 load capacity, and the result shows that the HZSM-5 serving as a solid acid can obviously improve the surface acidity of the cerium-based catalyst, so that the reaction activity is improved, and the reaction rate and the denitration efficiency are improved;
(3) compared with the existing acid auxiliary agent modified cerium-based catalyst, the preparation method of the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst disclosed by the invention has the advantages that the conversion rate of nitrogen oxides in the range of 250-400 ℃ reaches more than 80%, the denitration efficiency is obviously improved, the risk of secondary pollution is reduced, and the application field of the HZSM-5 molecular sieve in the denitration catalyst is expanded.
Drawings
FIG. 1 shows different HZSM-5 and CeO in the present invention2XRD result pattern of high performance cerium based catalyst modified by HZSM-5 molecular sieve in proportion;
FIG. 2 shows different HZSM-5 and CeO in the present invention2A NO conversion result graph of the proportional HZSM-5 molecular sieve modified high-performance cerium-based catalyst;
FIG. 3 shows different HZSM-5 and CeO in the present invention2NH of high performance cerium based catalyst modified with HZSM-5 molecular sieve in proportion3-a TPD results graph;
FIG. 4 shows NH in the present invention3-SCR reaction cycleSchematic diagram of E-R mechanism (2).
Detailed Description
For a further understanding of the invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings.
Example 1
The preparation method of the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst of the embodiment includes mixing the HZSM-5 molecular sieve and cerium nitrate hexahydrate, grinding until no particle sense exists, and then calcining and activating in a flowing air atmosphere to obtain the HZSM-5 molecular sieve modified cerium-based catalytic material with the cerium dioxide maintaining a cubic fluorite structure and increased surface lattice defects. The preparation process does not use a solvent, can effectively avoid the loss of active species, has the advantages of high yield, environmental friendliness, simple process, low preparation cost and the like, and is suitable for large-scale production; more importantly, the structural order of the mechanically ground catalyst is destroyed, the surface lattice defect of the cerium dioxide is increased, the formation of oxygen vacancy is facilitated, the catalytic activity is improved, and the adhesion and agglomeration of the catalyst are prevented.
In this embodiment, the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst uses ceria as a carrier, and the HZSM-5 molecular sieve supported on the surface thereof as an auxiliary. The material is prepared by mechanical grinding and roasting, and the specific steps are as follows:
(1) preparation of CeO2Catalyst and process for preparing same
Weighing 40g of cerium nitrate hexahydrate, grinding the cerium nitrate hexahydrate in an agate mortar for 20 minutes until no particle sense exists, spreading the cerium nitrate hexahydrate in a crucible, then putting the crucible into a muffle furnace to roast in a flowing air atmosphere, wherein the roasting temperature of the muffle furnace is 520-550 ℃, the heating rate is 2 ℃/min, the roasting time is 5-5.5 hours, and cooling the mixture to room temperature to obtain CeO2A catalyst powder. And tabletting the prepared catalyst by a press machine, and screening to a screen of 40-60 meshes to be reserved for testing.
(2) Preparation of 5 wt% HZSM-5/CeO2Catalyst and process for preparing same
0.1g of HZSM-5 molecular sieve and 4.75g of cerium nitrate hexahydrate are weighed, the mixture is ground in an agate mortar for 20 minutes until no particle sense exists, the mixture is laid in a crucible, and then the crucible is placed in a muffle furnaceRoasting in a flowing air atmosphere, wherein the roasting temperature of a muffle furnace is 520-550 ℃, the heating rate is 2 ℃/min, the roasting time is 5-5.5 h, and cooling to room temperature to obtain 5 wt% of HZSM-5/CeO2A catalyst powder. And tabletting the prepared catalyst by a press machine, and screening to a screen of 40-60 meshes to be reserved for testing.
(3) Catalyst Activity test
NH at steady state3The reaction gas component involved in the SCR reaction is NH3＝500ppm，NO＝500ppm，O2＝5vol％，N2As the balance gas, the total gas flow rate was 100mL/min (NH)310mL/min, 10mL/min NO, O 280 mL/min). The main process is as follows: first, 100mg of a sample was accurately weighed and loaded into a quartz tube having an inner diameter of 5mm, and placed in a heating furnace connected to a temperature-programmed apparatus, and purged in a high-purity nitrogen gas flow at 200 ℃ for 1 hour. Then, the reaction mixture was opened, and the reaction mixture was heated at 120000mL · g at different temperatures-1·h-1The space velocity ratio of (A) is 15min, tail gas is collected, and the concentration of nitrogen oxides is measured by an ECOM J2KN type flue gas analyzer. Finally, the conversion of nitrogen oxides is calculated by the following formula:
Figure BDA0003216063500000051
in the formula [ NO ]x]inIndicates the concentration of nitrogen oxides in the feed gas before reaction, [ NO ]x]outRepresenting the concentration of nitrogen oxide tail gas after reaction.
(4) Catalyst acid content test
Ammonia temperature programmed desorption experiment (NH)3TPD) is carried out in a fixed bed reactor of U-shaped quartz tubes connected to a thermal conductivity cell detector (TCD). First, 50mg of a sample was accurately weighed and purged with high-purity nitrogen gas at 100 ℃ for 1 hour. Then, the sample was NH at 100 ℃3Adsorbing for 30min, then N at the same temperature2Purging for 30 min. Finally, the sample was heated from 100 ℃ to 500 ℃ under pure helium at a heating rate of 10 ℃/min.
Example 2
The basic structure of the preparation method of the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst of this embodiment is the same as that of embodiment 1, and the differences and improvements are as follows: the HZSM-5 mass percent in the catalyst is 10wt percent, namely 0.2g of HZSM-5 molecular sieve and 4.5g of cerous nitrate hexahydrate are accurately weighed in the step (2).
The catalytic activity test data of the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst of this example are shown in table 1.
Example 3
The basic structure of the preparation method of the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst of this embodiment is the same as that of embodiment 2, and the differences and improvements are as follows: the weight percentage of HZSM-5 in the catalyst is 15 wt%, namely 0.3g of HZSM-5 molecular sieve and 4.25g of cerous nitrate hexahydrate are accurately weighed in the step (2).
The catalytic activity test data of the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst of this example are shown in table 1.
Example 4
The basic structure of the preparation method of the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst of this embodiment is the same as that of embodiment 3, and the differences and improvements are as follows: the HZSM-5 mass percent in the catalyst is 20wt percent, namely 0.4g of HZSM-5 molecular sieve and 4.0g of cerous nitrate hexahydrate are accurately weighed in the step (2).
The catalytic activity test data of the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst of this example are shown in table 1.
Example 5
The basic structure of the preparation method of the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst of this embodiment is the same as that of embodiment 4, and the differences and improvements are as follows: the HZSM-5 mass percent in the catalyst is 25wt percent, namely 0.5g of HZSM-5 molecular sieve and 3.75g of cerous nitrate hexahydrate are accurately weighed in the step (2).
The catalytic activity test data of the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst of this example are shown in table 1.
Example 6
The basic structure of the preparation method of the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst of this embodiment is the same as that of embodiment 5, and the differences and improvements are as follows: the HZSM-5 mass percent in the catalyst is 30wt percent, namely 0.6g of HZSM-5 molecular sieve and 3.5g of cerous nitrate hexahydrate are accurately weighed in the step (2).
The catalytic activity test data of the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst of this example are shown in table 1.
Comparative example
The catalyst of this comparative example was a pure CeO2 catalyst prepared in step (1) of example 1, and was different from example 1 in that: the catalyst of the comparative example is not modified by the HZSM-5 molecular sieve in the step (2), and the HZSM-5 molecular sieve is not added in the step (2), namely the HZSM-5 acidic auxiliary agent is not added.
The HZSM-5 molecular sieve modified cerium-based denitration catalyst of the present comparative example was subjected to catalytic activity tests at 200 ℃, 250 ℃, 300 ℃, 350 ℃ and 400 ℃, respectively, and the comparative example was used as a blank control to compare the test data of examples 1 to 6, as shown in table 1.
TABLE 1 HZSM-5/CeO at different temperatures2Denitration efficiency of catalyst and blank group catalyst
Figure BDA0003216063500000061
By performing comparative analysis on the experimental data, the following conclusions can be obtained:
it can be found through experiments of examples 1-6 and blank groups that all catalysts have NOxThe conversion rate shows a tendency to increase as the temperature increases from 200 ℃ to 400 ℃; this enhances the redox properties of the catalyst due to the increased temperature, shown as NH in FIG. 43SCR reaction cycle, ammonia gas is first adsorbed on the acid sites on the surface of the cerium-based catalyst, forming NH in the adsorbed state3A species; subsequently, NH in the adsorbed state3The species is oxidized at the catalyst surface to form a surface oxygen vacancy which binds adsorbed NH more strongly than a typical oxidation site3And to assist in its decomposition,simultaneously, tetravalent cerium ions are reduced into trivalent cerium ions; oxidizing trivalent cerium ions into tetravalent cerium ions by gas-phase oxygen of reaction species, and simultaneously supplementing lattice oxygen in oxygen vacancies to complete a redox cycle; this indicates that the enhancement of the redox performance contributes to the enhancement of the denitration reaction rate, thereby enhancing the denitration efficiency.
As shown in FIG. 1, for HZSM-5/CeO2Catalyst which retains the original CeO after introduction of different loadings of HZSM-52The cubic fluorite structure is not changed, and the (111) plane diffraction peak intensity is gradually weakened along with the increase of the addition amount of HZSM-5, which is caused by the introduction of HZSM-52The crystallinity is reduced, the structural order is damaged, and CeO is added2Surface lattice defects, leading to an increase in oxygen vacancies. By NH3Determination of HZSM-5/CeO by SCR Activity test2The NO conversion rate of the catalyst in HZSM-5 with different addition amounts. NO conversion increases with increasing temperature; pure CeO without HZSM-5 addition2The catalytic SCR catalytic activity is relatively low. NO after blank group catalyst is heated to 400 DEG CxThe conversion of (A) is only 65%, which is mainly pure CeO2Weak surface acidity, adverse NH3Resulting in low denitration efficiency.
In addition, the amount of HZSM-5 added was adjusted to HZSM-5/CeO2The catalytic activity of the catalyst has a major influence. As shown in FIG. 2, after HZSM-5 was added, NO in the examplesxBoth the conversions showed different increases, comparing example 1 and example 4, i.e. the loading of HZSM-5 was increased from 5 wt% to 20 wt%, HZSM-5/CeO2The catalytic activity of the catalyst is obviously improved between 200 ℃ and 350 ℃, and NO is reduced at 250 DEG CxThe conversion rate of the cerium-based catalyst is increased from 52.29% to 81.65%, which is mainly due to the fact that HZSM-5, as a solid acid promoter, not only enhances the acidity of the cerium-based catalyst, but also enables the number of acid sites on the surface of the cerium-based catalyst to be remarkably increased (which is from NH)3The TPD results were verified, as shown in FIG. 3), promoting NH3The catalytic efficiency is further remarkably improved by the adsorption; when the HZSM-5 loading was increased from 20 wt% to 30 wt%, i.e., comparing the conversion data of examples 4, 5 and 6 at different temperatures, it was found that200-400 ℃ NOxThe conversion of (a) is kept substantially constant; thus, the denitration efficiency of the HZSM-5 modified cerium-based catalyst is related to the load of HZSM-5, and the load of 20 wt% belongs to the NO of the catalyst at various temperaturesxThe optimum addition amount for conversion.
The present invention and its embodiments have been described above schematically, without limitation, and what is shown in the drawings is only one of the embodiments of the present invention, and the actual structure is not limited thereto. Therefore, if the person skilled in the art receives the teaching, without departing from the spirit of the invention, the person skilled in the art shall not inventively design the similar structural modes and embodiments to the technical solution, but shall fall within the scope of the invention.

Claims (8)

1. A preparation method of a HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst is characterized by comprising the following steps of: firstly, mixing an HZSM-5 molecular sieve and cerium nitrate hexahydrate, then grinding until no granular sensation exists, and then roasting and activating in a flowing air atmosphere to obtain cerium dioxide catalyst powder and an HZSM-5 molecular sieve modified cerium-based catalytic material with increased surface lattice defects.
2. The preparation method of the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst as claimed in claim 1, wherein the preparation method comprises the following steps: when the HZSM-5 molecular sieve and the cerous nitrate hexahydrate are mixed, the weight ratio of the HZSM-5 molecular sieve is as follows: 5 wt% -30 wt%.
3. The preparation method of the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst as claimed in claim 1, wherein the preparation method comprises the following steps: the preparation of the cerium oxide catalyst powder specifically includes the steps of:
step one, preparing a powder precursor: weighing cerium nitrate hexahydrate in an agate mortar, and grinding into precursor powder without granular sensation;
step two, roasting and activating the precursor: uniformly spreading the ground precursor powder in a crucible, and then roasting in a muffle furnace;
step three, powder collection: and cooling along with the furnace after the roasting is finished to obtain pure cerium dioxide catalyst powder.
4. The preparation method of the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst as claimed in claim 1, wherein the preparation method comprises the following steps: the preparation method of the HZSM-5 molecular sieve modified cerium dioxide catalyst specifically comprises the following steps:
step one, preparing a powder precursor: respectively weighing cerium nitrate hexahydrate and an HZSM-5 molecular sieve in an agate mortar, and grinding into precursor powder without granular sensation;
step two, roasting and activating the precursor: uniformly spreading the ground precursor powder in a crucible, and then roasting in a muffle furnace;
step three, powder collection: cooling along with the furnace after roasting is finished to obtain HZSM-5/CeO2A catalyst powder.
5. The preparation method of the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst as claimed in claim 3, wherein the preparation method comprises the following steps: in the first step, 40g of cerous nitrate hexahydrate is weighed and ground for 20min, and no granular sensation exists.
6. The preparation method of the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst as claimed in claim 3, wherein the preparation method comprises the following steps: in the second step, the precursor roasting condition is increased from room temperature to 520-550 ℃ at the temperature rising speed of 2 ℃/min in a flowing air atmosphere, and then the temperature is kept within the temperature range for 5-5.5 h and then the temperature is naturally reduced.
7. The preparation method of the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst according to claim 4, wherein the preparation method comprises the following steps: in the first step, the prepared HZSM-5/CeO2The catalyst is prepared from HZSM-5 and CeO2The mass ratio is 1: 19-3: 7, preparing cerium nitrate hexahydrate according to a cerium element molar ratio of 1: 1, accurately weighing.
8. The preparation method of the HZSM-5 molecular sieve modified high-performance cerium-based denitration catalyst according to claim 4, wherein the preparation method comprises the following steps: and in the second step, the roasting atmosphere is flowing air, the temperature is increased from room temperature to 520-550 ℃ at the temperature increase speed of 2 ℃/min, and then the temperature is kept in the temperature range for 5-5.5 h and then the temperature is naturally reduced.
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