CN111229212A

CN111229212A - CO-SCR denitration catalyst, preparation method and application

Info

Publication number: CN111229212A
Application number: CN202010196025.9A
Authority: CN
Inventors: 程星星; 李向东; 王志强; 付加鹏; 马春元; 王鹏
Original assignee: Shandong University
Current assignee: Shandong University
Priority date: 2020-03-19
Filing date: 2020-03-19
Publication date: 2020-06-05
Anticipated expiration: 2040-03-19
Also published as: CN111229212B

Abstract

The invention provides a CO-SCR denitration catalyst, a preparation method and application thereof, wherein the preparation method comprises the following steps: adding a precipitant into the solution of the mixed metal salt to obtain a precipitate, performing ball milling treatment on the precipitate to obtain powder, and heating the powder to 450-850 ℃ for calcination; the mixed metal salt is manganese salt and other metal salt, and the other metal salt is one or more of copper salt, iron salt, cerium salt, cobalt salt and nickel salt. The catalyst provided by the invention has good water resistance and can effectively solve the problem of CO + O in the CO-SCR catalytic process₂Solves the problem that the prior material has low catalytic NOx removal efficiency under the double interference condition of water vapor and oxygen.

Description

CO-SCR denitration catalyst, preparation method and application

Technical Field

The invention belongs to the field of industrial catalysis in chemical engineering, and relates to a CO-SCR denitration catalyst, and a preparation method and application thereof.

Background

The information in this background section is only for enhancement of understanding of the general background of the invention and is not necessarily to be construed as an admission or any form of suggestion that this information forms the prior art that is already known to a person of ordinary skill in the art.

Nitrogen oxides and carbon monoxide are two atmospheric pollutants in industrial production and life of modern society, and have great harm to human health and environment. Nitric oxide is the main component of nitrogen oxides and mainly comes from steel plants, thermal power plants, automobile exhaust and the like. Among the various denitration techniques, NH₃The SCR technology is the most widely used and mature denitration technology in the world at present due to high denitration efficiency, strong adaptability and good selectivity. But the reducing agent ammonia water sprayed by the technology can corrode the pipeline; moreover, if the flue gas temperature is low, the ammonia water can react with sulfur oxides in the flue to generate ammonium sulfate, so that the flue is blocked. Moreover, ammonia water is another kind of atmospheric pollutants, and improper control is revealed easily, causes secondary pollution, causes serious problems such as haze.

In the composition of flue gases, exhaust gases and exhaust gases, there is also present an equally inconstant amount of carbon monoxide. The CO-SCR technology using carbon monoxide as a reducing agent can not only effectively compensate the NH₃The defects of SCR technology, such as wide source, convenient acquisition, low price, difficult carbon deposition and blockage of equipment pipelines in the catalytic reaction process, and the like, are attractive and promising denitration technology.

According to the research of the inventor of the invention, at present, in the field of CO-SCR, the catalyst is generally suitable for CO + NO catalytic reaction in an ideal flue gas working condition without oxygen, water and other components, but once one or more of oxygen and water exist in an actual flue gas working condition, the catalytic efficiency of the catalyst is greatly reduced. In high-temperature aerobic environment, CO in the flue gas is firstly mixed with O₂The reaction occurs so that nitrogen oxides cannot be reduced; flue gas conditionsThe steam in the catalyst also generates the poisoning and inactivation phenomena on the catalytic performance of the catalyst, so the existing CO-SCR catalyst has the defects of poor water resistance, low practicability and the like.

Disclosure of Invention

In order to solve the defects of the prior art, the invention aims to provide a CO-SCR denitration catalyst, a preparation method and an application thereof₂Solves the problem that the prior material has low catalytic NOx removal efficiency under the double interference condition of water vapor and oxygen.

In order to achieve the purpose, the technical scheme of the invention is as follows:

on the one hand, the preparation method of the CO-SCR denitration catalyst comprises the steps of adding a precipitator into a solution mixed with metal salts to obtain precipitates, carrying out ball milling treatment on the precipitates to obtain powder, heating the powder to 450-850 ℃ and calcining the powder; the mixed metal salt is manganese salt and other metal salt, and the other metal salt is one or more of copper salt, iron salt, cerium salt, cobalt salt and nickel salt.

According to the invention, manganese salt and other metal salts such as copper salt, iron salt, cerium salt, cobalt salt and nickel salt are used as raw materials to prepare the CO-SCR denitration catalyst by adopting a precipitation method, wherein manganese is used as an active ingredient and can catalyze CO to reduce nitrogen oxides. Experiments show that when copper, iron, cerium, cobalt or nickel is added into the manganese active component, the poisoning effect of water vapor on the catalyst can be improved, the competition of oxygen and nitrogen oxides on carbon monoxide is improved, and the carbon monoxide and the nitrogen oxides are subjected to catalytic reduction reaction preferentially. Meanwhile, the catalyst is subjected to ball milling treatment after precipitation, so that the microstructure of the catalyst is uniformly distributed, the surface of the catalyst presents a porous structure, the surface area of the catalyst is increased, more surface active sites and larger reaction sites are provided for catalytic reaction, the poisoning effect of water vapor on the catalyst can be further improved, and the catalytic reduction efficiency can be improved.

In another aspect, a CO-SCR denitration catalyst is obtained by the preparation method.

In a third aspect, the CO-SCR denitration catalyst is applied to flue gas treatment.

The invention has the beneficial effects that:

(1) the manganese is used as the main active component of the catalyst, and has the capability of catalyzing the reduction of carbon monoxide to nitrogen oxides.

(2) The active component of the catalyst of the invention is added with at least one of copper, iron, cerium, cobalt or nickel, which can cooperate with manganese, improve the poisoning effect of water vapor on the catalyst, improve the competition of oxygen and nitrogen oxide on carbon monoxide, and lead the carbon monoxide to preferentially perform catalytic reduction reaction with the nitrogen oxide, and the content of the carbon monoxide is 10 percent H₂O and 5% of O₂Still has stronger denitration performance under the condition.

(3) The invention carries out ball milling treatment in the preparation process, so that the microstructure of the catalyst is uniformly distributed, the surface of the catalyst presents a porous structure, the microscopic surface area of the catalyst is increased, more surface active sites and larger reaction sites are provided for catalytic reaction, the toxic action of water vapor on the catalyst is further improved, and the denitration catalytic reduction efficiency is improved.

(4) The preparation method of the CO-SCR denitration catalyst is simple, high in catalysis efficiency, strong in practicability and easy to popularize.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 shows denitration catalysts prepared in examples 1, 2 and 3 of the present invention and comparative example, in which the denitration catalysts contain 10% of H₂O and 5% of O₂Comparative figure for the catalytic effect on NO removal under the conditions of (1).

Detailed Description

It is to be understood that the following detailed description is exemplary and is intended to provide further explanation of the invention as claimed. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

In view of the poor water resistance and O existing in the prior CO-SCR catalyst₂The invention provides a CO-SCR denitration catalyst, a preparation method and application thereof, and solves the problems of influencing the reduction of nitrogen oxides and the like.

The invention provides a preparation method of a CO-SCR denitration catalyst, which comprises the steps of adding a precipitator into a solution mixed with metal salts to obtain precipitates, carrying out ball milling treatment on the precipitates to obtain powder, heating the powder to 450-850 ℃ and calcining the powder; the mixed metal salt is manganese salt and other metal salt, and the other metal salt is one or more of copper salt, iron salt, cerium salt, cobalt salt and nickel salt.

The manganese salt in the invention refers to a compound of which the cation is manganese ion and the anion is acid radical anion, such as manganese nitrate, manganese acetate, manganese chloride and the like.

The other metal salt in the present invention refers to a compound in which the cation is other metal ion and the anion is acid anion, such as nitrate, acetate, chloride, and the like.

The precipitant is a soluble compound capable of precipitating manganese ions and other metal ions, such as carbonate, alkali (a compound whose anion is hydroxide, such as sodium hydroxide, ammonia water, and the like), and carbamide (urea).

In one or more embodiments of the present disclosure, the molar ratio of manganese to other metal elements in the mixed metal salt solution is 1-12: 1-2. Experiments show that when the molar ratio of the manganese element to the cerium element is 4: 0.9-1.1, the catalytic effect of the catalyst is better.

In one or more embodiments of the present disclosure, the concentration of the manganese salt in the mixed metal salt solution is 1-10 mol/L.

In one or more embodiments of the present disclosure, the concentration of the other metal salt in the mixed metal salt solution is 0.1 to 5 mol/L.

In one or more embodiments of the present disclosure, a precipitant is added to adjust the pH of the solution to 8 to 9. Can ensure the complete precipitation of metal ions.

In one or more embodiments of this embodiment, the precipitation agent is added and then a standing aging treatment is performed, and the solution after the standing aging is filtered to obtain a precipitate.

In the series of embodiments, the standing and aging time is 0.5-2 h. The filtration times are 3-5 times, and the pH of the filtrate is 7-7.5.

In one or more embodiments of the present disclosure, the rotation speed of the ball mill is 350 to 420r/min, and the ball milling time is 45 to 120 min.

In one or more examples of this embodiment, the powder is dried and then calcined. The influence of water evaporation on the microstructure of the catalyst is avoided, so that the catalytic effect is further improved.

In the series of embodiments, the drying temperature is 105-115 ℃.

In one or more embodiments of this embodiment, the calcination temperature is 500 to 550 ℃.

In another embodiment of the invention, a CO-SCR denitration catalyst is provided, which is obtained by the preparation method.

In a third embodiment of the invention, the application of the CO-SCR denitration catalyst in flue gas treatment is provided.

In one or more embodiments of this embodiment, the flue gas comprises water vapor and oxygen.

In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the technical solution of the present invention will be described in detail below with reference to specific examples and comparative examples.

Example 1

Weighing cerium ammonium nitrate (Ce (NH)₄)₂(NO₃)₆)15.81g of a 50 wt% aqueous manganese nitrate solution (Mn (NO)₃)₂·50wt％H₂O)41.3g, as Mn: adding Ce (4: 1) into deionized water for dissolving, and then stirring for 60min at the temperature of 70 ℃ to obtain a mixed salt solution A. Weighing a certain amount of Na₂CO₃Dissolving in deionized water to prepare alkaline precipitant Na₂CO₃And (3) solution. Adding Na dropwise into the mixed solution B under the condition of stirring at 40 DEG C₂CO₃Basic precipitant and stirring until the pH of the mixed solution is 8, to give mixture C. The mixture C was left to age for 2h at room temperature, then filtered and washed repeatedly with deionized water until the filtrate pH was 7 to give filter cake D. And (4) placing the filter cake D in a ball mill to perform ball milling treatment for 120min at the rotating speed of 420r/min to obtain powder E. And (3) putting the powder E into a drying oven to be dried for 12 hours at the temperature of 110 ℃, and finally calcining and activating for 5 hours in a muffle furnace at the temperature of 500 ℃ to prepare the denitration catalyst.

Example 2

Weighing copper nitrate trihydrate (Cu (NO)₃)₂·3H₂O)9.462g, 50 wt% aqueous manganese nitrate solution (Mn (NO)₃)₂·50wt％H₂O)126.152g, as Mn: adding Cu in a ratio of 9:1 into deionized water for dissolving, and then stirring for 60min at the temperature of 70 ℃ to obtain a mixed salt solution A. WeighingA certain amount of Na₂CO₃Dissolving in deionized water to prepare alkaline precipitant Na₂CO₃And (3) solution. Adding Na dropwise into the mixed solution B under the condition of stirring at 40 DEG C₂CO₃Basic precipitant and stirring until the pH of the mixed solution is 8, to give mixture C. The mixture C was left to age for 2h at room temperature, then filtered and washed repeatedly with deionized water until the filtrate pH was 7 to give filter cake D. And (4) placing the filter cake D in a ball mill to perform ball milling treatment for 120min at the rotating speed of 420r/min to obtain powder E. And (3) putting the powder E into a drying oven to be dried for 12 hours at the temperature of 110 ℃, and finally calcining and activating for 5 hours in a muffle furnace at the temperature of 500 ℃ to prepare the denitration catalyst.

Example 3

Weighing ferric nitrate nonahydrate (FeN)₃O₉·9H₂O)386.97g, 2.5 hydrated copper nitrate (Cu)₂H₁₀N₄O₁₇)22.28g of a 50 wt% aqueous manganese nitrate solution (Mn (NO)₃)₂·50wt％H₂O)308.53g, as Mn: cu: adding Fe in a ratio of 9:1:10 into deionized water for dissolving, and then stirring for 60min at the temperature of 70 ℃ to obtain a mixed salt solution A. Weighing a certain amount of Na₂CO₃Dissolving in deionized water to prepare alkaline precipitant Na₂CO₃And (3) solution. Adding Na dropwise into the mixed solution B under the condition of stirring at 40 DEG C₂CO₃Basic precipitant and stirring until the pH of the mixed solution is 8, to give mixture C. The mixture C was left to age for 2h at room temperature, then filtered and washed repeatedly with deionized water until the filtrate pH was 7 to give filter cake D. And (4) placing the filter cake D in a ball mill to perform ball milling treatment for 120min at the rotating speed of 420r/min to obtain powder E. And (3) putting the powder E into a drying oven to be dried for 12 hours at the temperature of 110 ℃, and finally calcining and activating for 5 hours in a muffle furnace at the temperature of 500 ℃ to prepare the denitration catalyst.

Example 4

Weighing 2.5 hydrated copper nitrate (Cu)₂H₁₀N₄O₁₇)100.20g, 4 g manganese acetate hydrate (Mn (CH)₃COO)₂·4H₂O)950.32g, as Mn: dissolving Cu in deionized water at a ratio of 9:1, and stirring at 70 deg.C for 40min to obtainThe salt solution a was mixed. Weighing a certain amount of Na₂CO₃Dissolving in deionized water to prepare alkaline precipitant Na₂CO₃And (3) solution. Adding Na dropwise into the mixed solution B under the condition of stirring at 40 DEG C₂CO₃Basic precipitant and stirring until the pH of the mixed solution is 8, to give mixture C. The mixture C was left to age for 2h at room temperature, then filtered and washed repeatedly with deionized water until the filtrate pH was 7 to give filter cake D. And (4) placing the filter cake D in a ball mill to perform ball milling treatment for 120min at the rotating speed of 420r/min to obtain powder E. And (3) putting the powder E into a drying oven to be dried for 12 hours at the temperature of 110 ℃, and finally calcining and activating for 5 hours in a muffle furnace at the temperature of 500 ℃ to prepare the denitration catalyst.

Comparative example 1

Weighing 4 parts of manganese acetate hydrate (Mn (CH)₃COO)₂·4H₂O)100g, adding the mixture into deionized water for dissolving, and then stirring for 60min at the temperature of 70 ℃ to obtain a mixed salt solution A. Weighing a certain amount of Na₂CO₃Dissolving in deionized water to prepare alkaline precipitant Na₂CO₃And (3) solution. Adding Na dropwise into the mixed solution B under the condition of stirring at 40 DEG C₂CO₃Basic precipitant and stirring until the pH of the mixed solution is 8, to give mixture C. The mixture C was left to age for 2h at room temperature, then filtered and washed repeatedly with deionized water until the filtrate pH was 7 to give filter cake D. And (4) placing the filter cake D in a ball mill to perform ball milling treatment for 120min at the rotating speed of 420r/min to obtain powder E. And (3) putting the powder E into a drying oven to be dried for 12 hours at the temperature of 110 ℃, and finally calcining and activating for 5 hours in a muffle furnace at the temperature of 500 ℃ to prepare the single manganese element denitration catalyst.

And (3) respectively taking the catalyst tablets obtained in the examples 1, 2 and 3 and the comparative example, screening, and taking 4ml of catalyst particles with 40-60 meshes to be filled into a fixed bed reactor for catalyst activity test. The activity test conditions were as follows: the temperature of the reaction system is 100-350 ℃, the reaction pressure is normal pressure, and the airspeed of the mixed gas is 15000h < -1 > mixed gas volume content:

800ppm of NO, 1600ppm of CO, 5% of O2, 10% of H2O, balance gas: n2. The total flow rate of gas was 1000 ml/min. Mixing all the gases by a mass flow meter and finally entering a reactor; the reactor is a stainless steel pipe with the inner diameter of 10mm, and is placed in a three-section heating vertical tubular furnace for heating; the exhaust GAs was collected at the sampling port with a MADUR-GA-60 portable flue GAs analyzer for analysis.

The activity of the catalyst was evaluated by the conversion of NO:

wherein NO_in、NO_outThe concentrations of NO at the inlet and outlet of the fixed bed reactor were indicated, respectively, and therefore the data were read after the denitration reaction was stabilized. The results of the activity test are shown in FIG. 1, and it can be seen from FIG. 1 that NO conversion increases first and then decreases; under the temperature of 100-350 ℃, the NO conversion rate of the manganese bimetallic or multi-metal catalyst containing Ce, Cu and Fe is higher than that of the single manganese denitration catalyst in the comparative example, so that the addition of at least one of other metal elements Cu, Fe and Ce improves the CO-SCR denitration performance of the manganese denitration catalyst under the conditions of 5% of O2 and 10% of H2O, namely the steam and oxygen interference resistance of the manganese denitration catalyst. Wherein the denitration performance of the catalyst is improved most obviously by adding the single-component element Ce, and the ratio of Mn: the NO conversion efficiency of the Ce-4: 1 denitration catalyst can reach over 84 percent at the temperature of 250-300 ℃; in comparison with examples 2 and 3, the Mn: cu: the denitration catalyst with the Fe ratio of 9:1:10 can improve the NO conversion rate from 35% to more than 65%, and the addition of the single-component element Fe can enable the CO-SCR denitration reaction to be carried out at a lower temperature, so that the low-temperature catalytic performance of the catalyst is improved. Experimental research shows that the addition of at least one of other metal elements Co and Ni can also improve the performance of the manganese denitration catalyst in O₂:5％,H₂And (3) the denitration performance of the CO-SCR is 10 percent.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of a CO-SCR denitration catalyst is characterized by comprising the steps of adding a precipitator into a solution mixed with metal salts to obtain precipitates, carrying out ball milling treatment on the precipitates to obtain powder, heating the powder to 450-850 ℃ and calcining the powder; the mixed metal salt is manganese salt and other metal salt, and the other metal salt is one or more of copper salt, iron salt, cerium salt, cobalt salt and nickel salt.

2. The method according to claim 1, wherein the molar ratio of manganese to other metal elements in the mixed metal salt solution is 1-12: 1-2; preferably, the molar ratio of the manganese element to the cerium element is 4: 0.9-1.1.

3. The method of claim 1, wherein the concentration of manganese salt in the mixed metal salt solution is 1 to 10 mol/L.

4. The method of claim 1, wherein the concentration of the other metal salt in the mixed metal salt solution is 0.1 to 5 mol/L.

5. The method for preparing a CO-SCR denitration catalyst according to claim 1, wherein a precipitant is added to adjust the pH of the solution to 8 to 9.

6. The method for preparing a CO-SCR denitration catalyst according to claim 1, wherein a precipitant is added to the solution, followed by aging treatment, and the aged solution is filtered to obtain a precipitate;

preferably, the standing and aging time is 0.5-2 h.

7. The method for preparing the CO-SCR denitration catalyst according to claim 1, wherein the rotation speed of the ball mill is 350 to 420r/min, and the ball mill treatment time is 45 to 120 min.

8. The method of preparing a CO-SCR denitration catalyst according to claim 1, wherein the powder is dried and then calcined;

preferably, the drying temperature is 105-115 ℃;

or the calcining temperature is 500-550 ℃.

9. A CO-SCR denitration catalyst, which is obtained by the preparation method of claim 1 to 8.

10. Use of the CO-SCR denitration catalyst of claim 9 in flue gas treatment.