CN109772346B

CN109772346B - Preparation method of composite material catalyst and application of composite material catalyst in denitrification at low temperature

Info

Publication number: CN109772346B
Application number: CN201910149910.9A
Authority: CN
Inventors: 王振平; 郭宝贵; 路文学; 王登峰; 吴永国; 王振华; 张彦; 张学兰; 尹洪清; 赵梅梅; 于利红; 肖瑞瑞
Original assignee: Yankuang Coal Water Slurry Gasification And Coal Chemical Industry National Engineering Research Center Co ltd; Yankuang Group Corp Ltd; Zaozhuang University
Current assignee: Yankuang Coal Water Slurry Gasification And Coal Chemical Industry National Engineering Research Center Co ltd; Yankuang Group Corp Ltd; Zaozhuang University
Priority date: 2019-02-28
Filing date: 2019-02-28
Publication date: 2022-01-25
Anticipated expiration: 2039-02-28
Also published as: CN109772346A

Abstract

The invention provides a composite material catalyst which is shown as a formula (I) and takes hydrotalcite-like compound as a precursor, and the application also provides a preparation method of the composite material catalyst, which comprises the following steps: A) mixing a cerium source, a copper source and an aluminum source to prepare an aqueous solution; B) mixing the aqueous solution with a precipitant to obtain an initial precipitation solution; C) mixing the initial precipitation solution with a reducing agent under an inert atmosphere, and reacting to obtain a hydrotalcite-like precursor; D) and (3) roasting the hydrotalcite-like precursor to obtain the composite material catalyst. The composite material catalyst provided by the invention has large specific surface area, high low-temperature activity and low possibility of being polluted by dust and SO₂Poisoning and the like; by means of the composite material catalyst, the removal rate of nitrogen oxide at low temperature can reach more than 98 percent; meanwhile, the composite catalyst has high structural stability, is harmless to the surrounding environment and production equipment, and has a high application prospect.

Description

Preparation method of composite material catalyst and application of composite material catalyst in denitrification at low temperature

Technical Field

The invention relates to the technical field of catalyst application, in particular to a composite material catalyst taking hydrotalcite-like compound as a precursor, a preparation method and application thereof.

Background

The civil coal is used for daily cooking and heating in winter, and mainly comprises two main types of civil coal and civil bulk coal. World health organization statistics show that there are approximately 30 million people worldwide per yearDirectly utilizes open fire or a stove to burn fuels such as biomass or coal and the like to heat and cook. About 430 million people die of indoor air pollution caused by the combustion of the fuel every year (Liuhaibiao, Koufei, Wangwei, etc., list of heavy metals in fine particulate matters discharged by the combustion of civil coal in China, environmental science 2016,37(8): 2823-. Particularly, about 14 percent of urban residents and 79 percent of rural residents use the fuel all the time in China. In recent years, the consumption of civil coal in China has been reduced to a certain extent due to the increase of environmental protection, but the consumption is basically maintained to be about 1 hundred million tons from 2008. The civil coal smoke pollution is mainly dispersed non-point source pollution, and Nitrogen Oxide (NO) is a plurality of pollution species_x) Is one of the major atmospheric pollutants. Research shows that about 1.1kg, 1.6kg and 0.8kg of NO can be discharged respectively from each ton of anthracite, bituminous coal and honeycomb briquette_xAnd the long-term emission can cause the harm of acid rain, photochemical smog, greenhouse effect, ozone layer damage and the like (Yan-Mi, Twill, Lu Jialin and the like, the current situation of civil coal in China and the pollutant emission analysis, the processing and comprehensive utilization of Chinese coal, 2017,1: 1-3).

How to effectively reduce NO in civil coal-fired flue gas_xThe emission of the coal is becoming a serious civil and environmental problem to be solved urgently in the sustainable development strategy of China, and is also the development direction of the global coal pollution treatment technology. Studies have shown that the main component of these nitrogen oxides is NO. Currently, the main mature technology for removing NO from coal-fired flue gas is the selective catalytic reduction method, which is abbreviated as SCR. However, this technique requires the action of a noble metal catalyst such as platinum-based, titanium-based, or vanadium-based catalyst to achieve a good removal effect. However, the above catalyst is large in investment and low in catalyst life; furthermore, the technology also needs to be assisted by NH₃As reducing agent, due to NH₃The SCR technology has the defects of toxicity, flammability, explosiveness and the like, and a set of strict transportation, storage, use, emergency treatment and safety precaution measures are inevitably required to be established in the application process of the SCR technology; at the same time, excess NH₃Penetration can also cause secondary pollution. Therefore, despite high purification efficiency of SCR technology, the above disadvantages are difficult to overcome, which makes it impossible to apply to the denitration process of coal flue gas for civil use. Literature reportsCan partially oxidize NO in the flue gas into NO under the action of a catalyst₂Then absorbing the latter by means of wet absorbents (e.g. lime and NaOH), i.e. oxidation-liquid absorption techniques to achieve NO removal_xThe purpose of (1). However, the catalyst needs to have better catalytic activity at a temperature of more than 175 ℃. Considering that the flue gas discharged by the civil coal-fired furnace has low temperature (generally about 100 ℃), and the adsorbent has limited adsorption capacity and needs to be replaced frequently, the application of the oxidation-absorption technology in the denitration of the civil coal flue gas is limited to a certain extent.

On the other hand, the combustion of anthracite, bituminous coal and honeycomb briquette in a civil stove can produce 69.9, 140.1 and 72.8kg of CO respectively, which is much more than NO_xThe discharge (Yan Mi Lei, Tang Yuan, Lu Jia Lin, etc., the current situation of civil coal and the discharge analysis of pollutants in China, the processing and the comprehensive utilization of Chinese coal, 2017,1: 1-3). Therefore, in the case of improper operation, the indoor CO concentration is easily caused to be high, thereby causing "gas poisoning" of residents. Meanwhile, CO is also a typical reducing agent and can react with NO under the action of a catalyst_XThe main component NO undergoes a chemical reaction as in equation 1:

CO+NO＝N₂+CO₂ (1)；

the technology is implemented in the process of converting NO into harmless N₂At the same time, part of the toxic CO is converted into CO₂The harm of CO is reduced, and the method has a prospect of large-scale popularization and application. Although precious metals including Rh, Pt and Pd can catalyze the reaction of CO and NO, the precious metals are expensive and not suitable for large-scale application of civil coal-fired flue gas denitration. Among a plurality of inexpensive metal denitration catalysts, Cu-based oxides have been the focus of research. Takashi Yamamoto et Al prepared Cu/Al by impregnation₂O₃、Cu/ZrO₂、Cu/ZSM-5、Cu/CeO_x/Al₂O₃、Cu/ZrO₂Cu/ZnO and Cu/SiO₂And the like; wherein, Cu/Al₂O₃Catalytic activity and N₂The selectivity of (a) is the highest, and the conversion rate of NO is 31% at the reaction temperature of 500 ℃. However, at 100 ℃ this catalyst is inactive and the conversion of NO and CO is substantialIs 0(T.Yamamoto, T.tanaka, R.Kuma, et al.NO reduction with CO in the presence of O₂over Al₂O₃-supported and Cu-based catalysts[J]Physical Chemistry Chemical Physics,2002,4: 2449-. Preparation of CuO/Al by sol-gel method₂O₃When the temperature exceeds 400 ℃, the catalyst can show higher denitrification capability (Lianjia, Qiwen, Zhujianhua, CuO/Al for CO reduction of NO₂O₃Preparation of catalyst and evaluation of Performance [ J]Modernization, 2016,36 (2): 83-86); B.Wen and M.He adopt coprecipitation method to prepare CuO-Ce₂O₃-MgO-Al₂O₃Complex oxide, found in SO₂In the presence of the catalyst, can convert NO into N with high selectivity₂(ii) a However, the reaction temperature is as high as 720 ℃ which is much higher than the temperature of the flue gas of a civil burner (Bin Wen, Mingyua He, Study of the Cu-Ce synthesis for NO reduction with CO in the presence of O₂,H₂O and SO₂in FCC operation, Applied Catalysis B: Environmental,2002,37: 75-82). In 2013, Ch.Ge, L.Liu, X.Yao et Al found CuNi/gamma-Al to be obtained by the impregnation method₂O₃Higher catalytic activity can be obtained by activation at 350 ℃ for 1h in a reducing atmosphere (e.g. CO/He atmosphere) (Chengyan Ge, Lianjun Liu, Xiaojiang Yao, Changlin Tang, Fei Gao, Lin Dong, Treatment induced recoverable activity and selectivity of low-temperature activity and selectivity of copper-based catalysts for NO reduction [ J],Catalysis Science&Technology,2013,3: 1547-1557); the great inconvenience of the catalyst in the actual use process is undoubtedly caused, and the popularization of the catalyst in the denitrification of the civil coal-fired flue gas is limited; even after the pretreatment, the optimal catalytic temperature of the catalyst is still above 300 ℃; when the temperature is 200 ℃, the NO conversion rate is less than 90%, and obviously, the requirement of removing NO under the low temperature condition cannot be met. Worse still, the active sites of these catalysts are very susceptible to SO at high temperatures₂The poisoning and inactivation speed are high.

In summary, as the flue gas temperature of civil burners is generally lower than 150 ℃, at such low temperature, the flue gas temperature is generally lower than 150 ℃The catalyst is difficult to realize the high-efficiency catalytic conversion of CO and NO; in addition, a certain amount of SO is also present in the coal-fired flue gas₂And dust, which easily covers the active sites of the catalyst, causing "poisoning" of the catalyst. Therefore, it is necessary to develop and design a high-efficiency catalyst capable of stably removing nitrogen oxides in flue gas at low temperature for civil combustion furnaces.

Disclosure of Invention

The invention aims to provide a composite material catalyst taking hydrotalcite-like compound as a precursor and a preparation method thereof, and the composite material catalyst prepared by the method can realize high-efficiency catalysis of CO and NO conversion in civil coal-fired flue gas at a low temperature of 60-120 ℃.

In view of the above, the present application provides a composite catalyst represented by formula (I),

Cu_xCe_yAl_zO_m (Ⅰ)；

wherein x is 0.1-0.8, y is 0.01-0.3, and z is 0.01-0.5;

m is the atomic number required to satisfy the valence of the other three elements.

Preferably, x is 0.2 to 0.7, y is 0.03 to 0.1, and z is 0.02 to 0.4.

The application also provides a preparation method of the composite material catalyst, which comprises the following steps:

A) preparing a cerium source, a copper source and an aluminum source according to the atomic number ratio of each element in the composite material catalyst shown in the formula (I), and mixing the cerium source, the copper source and the aluminum source to prepare an aqueous solution;

B) mixing the aqueous solution with a precipitant to obtain an initial precipitation solution; the precipitant is sodium acetate and sodium carbonate;

C) mixing the initial precipitation solution with a reducing agent under an inert atmosphere, and reacting to obtain a hydrotalcite-like precursor;

D) and (3) roasting the hydrotalcite-like precursor to obtain the composite material catalyst.

Preferably, the reducing agent is selected from one or more of formaldehyde, acetaldehyde, vitamin C, glucose and hydrazine hydrate.

Preferably, the cerium source is cerium nitrate, the copper source is copper nitrate, and the aluminum source is aluminum nitrate; the ratio of the total mole number of the copper source and the cerium source to the mole number of the reducing agent is 1 (2-5).

6. The method according to claim 3, wherein the ratio of the total number of moles of the cerium source, the copper source and the aluminum source to the number of moles of the sodium acetate is 1 (1.5 to 3), and the ratio of the total number of moles of the cerium source, the copper source and the aluminum source to the number of moles of the sodium carbonate is 2: 1.

Preferably, step C) is specifically:

and blowing out air in the initial precipitation solution by using inert gas, adding a reducing agent, aging at 60 ℃ for 2-4 h, carrying out vacuum filtration, and carrying out vacuum drying on the obtained filter cake at 80 ℃ for 10-12 h to obtain the hydrotalcite-like precursor.

Preferably, the calcining temperature is 400-800 ℃, and the time is 4-8 h.

The application also provides a method for removing nitrogen oxides in civil combustion coal smoke, which comprises the following steps:

and reacting nitric oxide and carbon monoxide under the action of the composite material catalyst or the composite material catalyst prepared by the preparation method to obtain nitrogen and carbon dioxide.

Preferably, the reaction temperature is 60-120 ℃, the reaction pressure is 0.5-3 MPa, and the space velocity is 1000-8000 h^-1And the initial molar ratio of the carbon monoxide to the nitric oxide is 1-5: 1.

The application provides a composite material catalyst taking hydrotalcite-like compound as a precursor, which is a copper-based catalyst in a high-activity reduction state, wherein the addition of metal Ce provides a second variable valence metal except Cu, a new active center is introduced, and simultaneously, the mesoporous structure of the composite material enables the composite material to have a larger specific surface, so that the high dispersion of active components is facilitated.

The application also provides a preparation method of the composite material catalyst, in the preparation process of the hydrotalcite-like precursor, fresh variable valence active metal species are subjected to liquid phase in-situ reduction by a reducing agent, so that a copper-based catalyst in a high-activity reduction state can be obtained; meanwhile, in the process of calcining the hydrotalcite-like precursor, gases such as carbon dioxide, water vapor and the like generated by decomposition are beneficial to forming a mesoporous structure of the composite material, so that the composite material has a large specific surface area, and further, the high dispersion of active components is beneficial, and finally, the activation and catalytic conversion of CO and NO are realized under the low-temperature condition, and the aim of efficiently removing the flue gas of the civil combustion furnace is fulfilled.

Drawings

FIG. 1 is an SEM photograph of a hydrotalcite-like precursor prepared in example 1 of the present invention;

fig. 2 is an SEM photograph of the composite catalyst obtained after the hydrotalcite-like precursor prepared in example 1 of the present invention was calcined.

Detailed Description

For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.

Aiming at the defects that the dust and SO are not easily sealed under the condition of low temperature (60-120 ℃) in the prior art₂The application provides a composite material catalyst taking hydrotalcite-like compound as a precursor, the composite material catalyst is shown as a formula (I),

Cu_xCe_yAl_zO_m (Ⅰ)；

wherein x is 0.1-0.8, y is 0.01-0.3, and z is 0.01-0.5;

m is the number of oxygen atoms required to satisfy the valences of the other three elements.

The composite material catalyst is a composite oxide taking layered hydrotalcite as a precursor, has good and regular sheet crystal morphology, does not have an agglomeration phenomenon, and is beneficial to improving the low-temperature catalytic capability of the catalyst by exposing the reduction metal active sites.

In a specific embodiment, in the composite catalyst, x is 0.2 to 0.7, y is 0.03 to 0.1, and z is 0.02 to 0.4.

The application also provides a preparation method of the composite material catalyst, which specifically comprises the following steps:

In the preparation of the composite catalyst according to the present invention, the present application first prepares raw materials of a cerium source, a copper source and an aluminum source, which are well known to those skilled in the art and may be chlorides, sulfates or nitrates of the above-mentioned metal elements; for example, the cerium source is cerium nitrate, the copper source is copper nitrate, and the aluminum source is aluminum nitrate. The cerium source, the copper source and the aluminum source are added according to the atomic number ratio of each element in the composite material catalyst shown in the formula (I). The raw materials are mixed and then mixed with water to prepare a mixed aqueous solution, wherein the concentration of the aqueous solution is 0.2-2 mol/L.

The aqueous solution is then mixed with a precipitating agent, in this case selected from sodium acetate and sodium carbonate, both strong bases and weak acid salts, to obtain an initial precipitate, the metal salts forming a hydroxide precipitate having a hydrotalcite-like layered structure after the aqueous solution is mixed with the precipitating agent. In the application, the ratio of the total mole number of the cerium source, the copper source and the aluminum source to the mole number of the sodium acetate is 1 (1.5-3), and the ratio of the total mole number of the cerium source, the copper source and the aluminum source to the mole number of the sodium carbonate is 2: 1; the proportion relation of the raw materials is used for ensuring that hydroxide precipitate with hydrotalcite-like layered structure can be formed.

Mixing the initial precipitator and a reducing agent in an inert atmosphere, and reacting to obtain a hydrotalcite-like precursor; in this process, the reducing agent is a reducing agent for reducing the metal element, and is a reducing agent well known to those skilled in the art, and is exemplified by one or more selected from the group consisting of formaldehyde, acetaldehyde, sodium borohydride, vitamin C, glucose, and hydrazine hydrate. The ratio of the total mole number of the copper source and the cerium source to the mole number of the reducing agent is 1: 2-1: 5. The inert atmosphere is high-purity nitrogen or argon. After addition of the reducing agent, Cu²⁺、Ce⁴⁺Reduction of isoreactive metals to make part of Cu²⁺Conversion to Cu⁺Or Cu⁰，Ce⁴⁺Conversion to Ce³⁺Thereby increasing the reducing species. Studies have shown that more Cu is present⁺The generation is beneficial to the adsorption of CO; CO in Cu⁺With O radicals, resulting in the desorption of NO from the oxygen vacancies and the formation of CO₂And an N radical; at the same time, N free radical can react with NO or CO to generate N₂O or NCO, or two N radicals combined to form N₂. In addition, in this process, Cu⁺Can be reduced to Cu⁰，N₂O can be reduced to N₂And, furthermore, Cu⁰Is considered to be N₂Reduction of O to N₂The active site of (3). Thus, Cu⁺/Cu⁰The cycle of the reduction pair is to realize N₂Reduction of O to N₂Is critical. Under the action of the reducing agent in the scheme, N₂O may be changed to N₂And O, which can combine with adjacent CO to form N₂And completing the cycle. It is easy to find that there are enough oxygen vacancies (holes) and Cu⁺The ions favor the reduction of NO by CO. Therefore, the in-situ addition of the reducing agent can realize the Cu with catalytic activity⁺And Cu⁰And further improves the low-temperature activity of the catalyst.

As can be seen from the above process for preparing hydrotalcite-like precursor, the reduction reaction of the present application isIn the liquid phase. Therefore, an inert gas is required to be introduced into the reaction system before the reduction reaction is carried out, so as to avoid other chemical reactions. More importantly, the reduction reaction in the liquid phase can avoid the pretreatment of the composite material in a reducing atmosphere before use; if the hydrotalcite-like precursor is not subjected to liquid phase in-situ reduction and calcined, most of the obtained active metal Cu is positive 2 valence, the catalytic process cannot be realized, so that the catalyst needs to be subjected to H before use₂Or the reducing agent such as CO is pretreated at the temperature of 200-400 ℃. Thus, it is greatly inconvenient in denitrification of a domestic furnace. Meanwhile, in each home, it is impossible to prepare such a reducing atmosphere condition for safety reasons. Therefore, the in-situ liquid phase reduction method has the advantages of simple technical operation, short time consumption, low temperature, less energy consumption, easy control of reduction conditions and no potential safety hazard.

Finally, roasting the talc-like precursor to obtain the composite catalyst; the calcination is a technique known to those skilled in the art, and is not particularly limited herein. The roasting temperature is 400-800 ℃, and the roasting time is 4-8 h.

The method for obtaining the composite material catalyst comprises the following steps:

1) preparing a cerium source, a copper source and an aluminum source into 0.2-2 mol/L aqueous solution according to the metal molar ratio, and simultaneously dissolving sodium acetate and sodium carbonate into deionized water to obtain a precipitator;

2) dropwise adding the obtained mixed salt solution and a precipitator into 200mL of deionized water by means of water bath while keeping vigorous stirring at 30-60 ℃, wherein the pH of the mixed system is kept at 6-11 within 1-2 h;

3) after the dropwise addition is finished, blowing out and exhausting air in the obtained mixed system by using high-purity inert gas, maintaining the atmosphere of the inert gas, and dropwise adding a solution containing a proper amount of reducing agent into the mixed solution for 1-2 hours;

4) after the addition of the reducing agent solution is finished, stirring and aging at 60 ℃ for 2-4 h, carrying out vacuum filtration, and repeatedly washing with deionized water until no sodium ions are detected in the filtrate; then placing the filter cake in an oven, and carrying out vacuum drying for 10-12 h at 80 ℃ to obtain a hydrotalcite-like precursor; and finally, roasting for 4-8 h at 400-800 ℃ in an inert atmosphere to obtain the composite material.

The application also provides an application of the composite material catalyst, which is specifically applied to low-temperature conversion of nitrogen oxides in coal-fired civil furnaces, and specifically comprises the following steps:

and reacting the nitric oxide and the carbon monoxide under the action of the composite material catalyst to obtain nitrogen and carbon dioxide.

In the above reaction, the specific conditions of the reaction are: the reaction temperature is 60-120 ℃, the pressure is 0.5-3 MPa, and the airspeed is 1000-8000 h^-1And the initial molar ratio of CO to NO is (1-5): 1.

the addition of two valence-variable metals of Cu and Ce in the composite material catalyst ensures the increase of active sites; the precursor hydrotalcite-like structure is beneficial to the improvement of the specific surface of the catalyst and the dispersion of active sites.

In the preparation process of the composite material catalyst, the liquid-phase in-situ reduction is carried out on the catalyst by virtue of a liquid reducing agent, so that the modulation of the valence of the active metal is realized, the pretreatment of the catalyst in a reducing atmosphere before use is avoided, and the technology has the advantages of simple operation, short time consumption, low temperature, low energy consumption, easy control of reducing conditions and no potential safety hazard; meanwhile, the hydrotalcite-like precursor obtained by coprecipitation can release water vapor and carbon dioxide gas in a high-temperature calcination process, so that the catalyst has a regular mesoporous structure and a large specific surface, high dispersion and exposure of an active site of the catalyst are facilitated, and activation of CO and NO under a low-temperature condition is finally facilitated. The catalyst provided by the invention has two metal active sites, the active sites are highly dispersed, the proportion of active species is high, and the NO conversion rate of more than 98% can be realized under the low-temperature condition. Meanwhile, the catalyst is not easy to be polluted by dust and SO in the flue gas₂Pollution and good catalytic stability.

For further understanding of the present invention, the composite catalyst, the preparation method and the application thereof provided by the present invention will be described in detail with reference to the following examples, and the scope of the present invention is not limited by the following examples.

Example 1

Taking 0.08mol of Cu (NO)₃)₂·3H₂O、0.005mol Ce(NO₃)₃·6H₂O and 0.04mol Al (NO)₃)₃·9H₂O was prepared as a 1.45mol/L salt solution (100mL) with CH₃COONa·3H₂O and Na₂CO₃Dissolving in 100mL deionized water to obtain a precipitant, wherein CH₃COONa·3H₂The concentration of O is 2.5mol/L, Na₂CO₃The concentration of the two solutions is 0.225mol/L, the temperature of the water bath is controlled at 50 ℃, the two solutions are dripped into 100mL of deionized water in a cocurrent way under the condition of violent stirring, the pH value of the solution is kept to be 9, and the dripping is finished within 1 hour; after the precipitation is completed, dropwise adding a fresh 100mL sodium borohydride (1.7mol/L) solution in a nitrogen atmosphere for 1.2 h; after the liquid phase in-situ reduction is finished, keeping the temperature of 50 ℃ under an inert atmosphere for aging for 3h, carrying out vacuum filtration, washing the filtrate by using deionized water until no sodium ion is detected, and drying the filter cake at 80 ℃ to obtain a precursor of the catalyst; finally in N₂Roasting at 500 deg.C for 5h in atmosphere to obtain composite oxide containing Cu in terms of metal mol_0.8Ce_0.05Al_0.4O_1.475The catalyst of (1). Fig. 1 is an SEM photograph of the catalyst precursor prepared in this example, and fig. 2 is an SEM photograph of the catalyst prepared in this example.

The performance experiment of the catalyst for catalyzing the reaction of NO and CO is carried out in a stainless steel reactor with the inner diameter of 10mm, and the evaluation conditions are as follows: p is 3.0MPa, T is 90 deg.C, GHSV is 5000h^-1N (co)/n (no) ═ 3. The product composition was analyzed by gas chromatography and the reaction results obtained are shown in table 1:

TABLE 1 data Table of the catalytic NO and CO reactions of the catalyst

NO conversion (%)	N₂Selectivity (%)
		98.7	99.8

Example 2

Taking 0.05mol of Cu (NO)₃)₂·3H₂O、0.01mol Ce(NO₃)₃·6H₂O and 0.02mol Al (NO)₃)₃·9H₂O was prepared as a 0.8mol/L salt solution (100mL) with 0.016mol of CH₃COONa·3H₂O and 0.015mol of Na₂CO₃Dissolving the two solutions in 100mL of deionized water to prepare a precipitator, and dropping the two solutions into 100mL of deionized water by cocurrent flow under vigorous stirring at 60 ℃ while keeping the pH value of the solution at 8, wherein the dropping is finished within 1 hour; after the precipitation is completed, under the argon atmosphere, dropwise adding a fresh 100mL formaldehyde (1.8mol/L) solution for 1.5 h; after the liquid phase in-situ reduction is finished, keeping the temperature of 60 ℃ under an inert atmosphere for aging for 3h, carrying out vacuum filtration, washing the filtrate with deionized water until the filtrate is neutral, and drying the filter cake at 80 ℃ to obtain a precursor of the catalyst; finally in N₂Roasting at 450 deg.C for 5h in atmosphere to obtain composite oxide containing Cu in terms of metal mol_0.1Ce_0.01Al_0.02O_0.145The catalyst of (1).

The reaction of NO and CO catalyzed by the catalyst is carried out in a stainless steel reactor with the inner diameter of 10mm, and the evaluation conditions are as follows: 4.0Mpa, 110 deg.C and 58000h GHSV^-1N (co)/n (no) ═ 5. The product composition was analyzed by gas chromatography and the reaction results obtained are shown in table 2:

TABLE 2 data Table of the catalytic NO and CO reactions of the catalyst

NO conversion (%)	N₂Selectivity (%)
		99.4	99.2

Example 3

Taking 0.04mol of Cu (NO)₃)₂·3H₂O、0.004mol Ce(NO₃)₃·6H₂O and 0.01mol Al (NO)₃)₃·9H₂O was prepared as a 0.54mol/L salt solution (100mL) with 0.108mol CH₃COONa·3H₂O and 0.0025mol of Na₂CO₃Dissolving the two solutions in 100mL of deionized water to prepare a precipitator, violently stirring the two solutions at 60 ℃ to enable the two solutions to be dripped into 100mL of deionized water in a parallel flow manner, keeping the pH value of the solution at 10, and finishing dripping within 1 hour; after the precipitation is completed, under the argon atmosphere, 100mL of newly prepared hydrazine hydrate (0.9mol/L) solution is added dropwise, and the use time is 1.5 h; after the liquid phase in-situ reduction is finished, keeping the temperature of 40 ℃ under an inert atmosphere for aging for 3h, carrying out vacuum filtration, washing the filtrate with deionized water until the filtrate is neutral, and drying the filter cake at 80 ℃ to obtain a precursor of the catalyst; finally in N₂Roasting at 600 deg.C for 5h in atmosphere to obtain composite oxide containing Cu in terms of metal mol_0.1Ce_0.01Al_0.02O_0.145The catalyst of (1).

The reaction of NO and CO catalyzed by the catalyst is carried out in a stainless steel reactor with the inner diameter of 10mm, and the evaluation conditions are as follows: p2.0 MPa, T60 deg.C, GHSV 3000h^-1N (co)/n (no) ═ 2. The product composition was analyzed by gas chromatography and the reaction results obtained are shown in table 3:

TABLE 3 data Table of the catalytic NO and CO reactions of the catalyst

NO conversion (%)	N₂Selectivity (%)
		95.3	100

Example 4

0.07mol of Cu (NO)₃)₂·3H₂O、0.007mol Ce(NO₃)₃·6H₂O and 0.03mol Al (NO)₃)₃·9H₂O was prepared as a 0.107mol/L salt solution (100mL) while 0.0214mol CH was added₃COONa·3H₂O and 0.007mol of Na₂CO₃Dissolving the two solutions in 100mL of deionized water to prepare a precipitator, violently stirring the two solutions at 60 ℃ to enable the two solutions to be dripped into 100mL of deionized water in a parallel flow manner, keeping the pH value of the solution at 10, and finishing dripping within 1 hour; after the precipitation is completed, under the argon atmosphere, 100mL of glucose (1.54mol/L) solution which is newly prepared is added dropwise, and the time for use is 1.5 h; after the liquid phase in-situ reduction is finished, keeping the temperature of 50 ℃ under an inert atmosphere for aging for 2h, carrying out vacuum filtration, washing the filtrate with deionized water until the filtrate is neutral, and drying the filter cake at 80 ℃ to obtain a precursor of the catalyst; finally in N₂Roasting at 400 deg.C for 5h in atmosphere to obtain composite oxide containing Cu in terms of metal mol_0.7Ce_0.07Al_0.3O_1.255The catalyst of (1).

The reaction of NO and CO catalyzed by the catalyst is carried out in a stainless steel reactor with the inner diameter of 10mm, and the evaluation conditions are as follows: p4.0 Mpa, T110 deg.C, GHSV 7000h^-1N (co)/n (no) ═ 4. The product composition was analyzed by gas chromatography and the reaction results obtained are shown in table 4:

TABLE 4 data table of the catalytic NO and CO reactions of the catalyst

Example 5

0.02mol of Cu (NO)₃)₂·3H₂O、0.003mol Ce(NO₃)₃·6H₂O and 0.01mol Al (NO)₃)₃·9H₂O was prepared as a 0.33mol/L salt solution (100mL) while 0.066mol CH was added₃COONa·3H₂O and 0.0065mol of Na₂CO₃Dissolving the two solutions in 100mL of deionized water to prepare a precipitator, violently stirring the two solutions at 60 ℃ to enable the two solutions to be dripped into 100mL of deionized water in a parallel flow manner, keeping the pH value of the solution at 10, and finishing dripping within 1 hour; after the precipitation is completed, under the argon atmosphere, 100mL of newly prepared acetaldehyde (0.92mol/L) solution is added dropwise for 1.5 h; after the liquid phase in-situ reduction is finished, keeping the temperature of 50 ℃ under an inert atmosphere for aging for 2h, carrying out vacuum filtration, washing the filtrate with deionized water until the filtrate is neutral, and drying the filter cake at 80 ℃ to obtain a precursor of the catalyst; finally in N₂Roasting at 400 deg.C for 5h in atmosphere to obtain composite oxide containing Cu in terms of metal mol_0.2Ce_0.03Al_0.1O_0.395The catalyst of (1).

The reaction of NO and CO catalyzed by the catalyst is carried out in a stainless steel reactor with the inner diameter of 10mm, and the evaluation conditions are as follows: p4.0 Mpa, T80 deg.C, GHSV 7000h^-1N (co)/n (no) ═ 5. The product composition was analyzed by gas chromatography and the reaction results obtained are shown in table 5:

TABLE 5 Performance data Table for catalysis of the NO and CO reaction by the catalyst

NO conversion (%)	N₂Selectivity (%)
		99.2	98.5

Comparative example 1

Taking 0.08mol of Cu (NO)₃)₂·3H₂O、0.005mol Ce(NO₃)₃·6H₂O and 0.04mol Al (NO)₃)₃·9H₂O was prepared as a 1.45mol/L salt solution (100mL) with CH₃COONa·3H₂O and Na₂CO₃Dissolving in 100mL deionized water to obtain a precipitant, wherein CH₃COONa·3H₂The concentration of O is 2.5mol/L, Na₂CO₃The concentration of the catalyst is 0.225mol/L, the temperature of a water bath is controlled to be 50 ℃, the two solutions are dripped into 100mL of deionized water in a cocurrent manner under the condition of vigorous stirring, the pH value of the solution is kept to be 9, the solution is aged for 3 hours under the condition of stirring after dripping for 1 hour, vacuum filtration is carried out, deionized water is used for washing until no sodium ion is detected in the filtrate, and then a filter cake is dried at 80 ℃ to obtain a precursor of the catalyst; finally in N₂Roasting at 500 deg.C for 5h in atmosphere to obtain composite oxide containing Cu in terms of metal mol_0.8Ce_0.05Al_0.4O_1.475The catalyst of (1).

The performance experiment of the catalyst for catalyzing the reaction of NO and CO is carried out in a stainless steel reactor with the inner diameter of 10mm, and the evaluation conditions are as follows: p is 3.0MPa, T is 120 deg.C, GHSV is 5000h^-1N (co)/n (no) ═ 3. The product composition was analyzed by gas chromatography and the reaction results obtained are shown in table 6:

TABLE 6 data Table of the catalytic NO and CO reactions of the catalyst

NO conversion (%)	N₂Selectivity (%)
		38.7	87.3

As can be seen from Table 6, the liquid phase in situ reduction is weaker in the ability of the catalyst to catalyze the reaction of NO and CO at low temperature, indicating the importance of the low temperature liquid phase reduction.

Comparative example 2

Before the catalyst evaluation, the catalyst was activated by reduction at 400 ℃ for 2 hours in a CO atmosphere, and then subjected to a catalytic evaluation test in a stainless steel reactor having an inner diameter of 10mm under the following conditions: p is 3.0MPa, T is 120 deg.C, GHSV is 5000h^-1N (co)/n (no) ═ 3. The product composition was analyzed by means of gas chromatography and the reaction results obtained are shown in table 7:

TABLE 7 data Table for the catalytic NO and CO reactions of the catalysts

NO conversion (%)	N₂Selectivity (%)
		55.6	90.5

As can be seen from table 7, when the high-temperature reduction was performed in a CO atmosphere before the use of the catalyst, the catalytic activity was slightly improved as compared with that without the pretreatment (table 6), but the catalytic activity was low and the low-temperature denitrification ability was weak as compared with the results shown in table 1. Thus, the importance of liquid phase in situ reduction is again illustrated.

The above description of the embodiments is only intended to facilitate the understanding of the method of the invention and its core idea. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A preparation method of a composite material catalyst for removing nitrogen oxides in civil combustion coal flue gas is characterized by comprising the following steps:

D) roasting the hydrotalcite-like precursor in an inert atmosphere to obtain a composite material catalyst;

the composite catalyst is shown as a formula (I):

Cu_xCe_yAl_zO_m （Ⅰ）；

wherein x = 0.1-0.8, y = 0.01-0.3, and z = 0.01-0.5;

m is the atom number required by the valence of other three elements;

the reducing agent is selected from one or more of formaldehyde, acetaldehyde, vitamin C, glucose and hydrazine hydrate.

2. The method according to claim 1, wherein x =0.2 to 0.7, y =0.03 to 0.1, and z =0.02 to 0.4.

3. The method according to claim 1, wherein the cerium source is cerium nitrate, the copper source is copper nitrate, and the aluminum source is aluminum nitrate; the ratio of the total mole number of the copper source and the cerium source to the mole number of the reducing agent is 1 (2-5).

4. The method according to claim 1, wherein the ratio of the total number of moles of the cerium source, the copper source and the aluminum source to the number of moles of the sodium acetate is 1 (1.5 to 3), and the ratio of the total number of moles of the cerium source, the copper source and the aluminum source to the number of moles of the sodium carbonate is 2: 1.

5. The method according to claim 1, wherein step C) is in particular:

6. The preparation method according to claim 1, wherein the calcining temperature is 400-800 ℃ and the calcining time is 4-8 h.

7. A method for removing nitrogen oxides from flue gas of domestic combustion, comprising:

reacting nitric oxide and carbon monoxide under the action of the composite material catalyst prepared by the preparation method of any one of claims 1 to 6 to obtain nitrogen and carbon dioxide.

8. The method according to claim 7, wherein the reaction temperature is 60-120 ℃, the reaction pressure is 0.5-3 MPa, and the space velocity is 1000-8000 h^-1And the initial molar ratio of the carbon monoxide to the nitric oxide is 1-5: 1.