Preparation method and application of molecular sieve catalyst for synergistically removing CO and NO under medium and low temperature conditions

Abstract

The invention relates to the technical field of gas pollutant removal and catalyst materials, in particular to a preparation method and application of a molecular sieve catalyst for synergistically removing CO and NO under medium and low temperature conditions. The preparation method comprises the following steps: dissolving copper salt and cerium salt in water to prepare a mixed solution; adding a beta molecular sieve into the mixed solution, uniformly stirring, carrying out dipping treatment under a water bath heating condition, and then drying and calcining to obtain the CuCe / beta molecular sieve catalyst. According to the present invention, the preparation process is simple, the catalyst preparation raw material cost is low, the catalyst has characteristics of good catalytic activity, wide temperature window and high N2 selectivity when the catalyst is used for removing nitrogen oxide (NOx) and CO pollutants in discharged industrial flue gas in steel, cement, petrochemical industry and other industries, and the NO conversion rate can achieve 90%, the CO conversion rate can achieve 99% and the N2 selectivity can achieve 95% within the range of 200-350 DEG C.

Description

Technical Field

[0001] The present invention relates to the technical field of gas pollutant removal and catalyst materials, and in particular to a preparation method and application of a molecular sieve catalyst for synergistically removing CO and NO under medium and low temperature conditions. Background Art

[0002] Nitrogen monoxide (NO) and carbon monoxide (CO) are both major atmospheric pollutants, mainly from tail gas emissions from incomplete combustion of fossil fuels such as coal, oil and natural gas, and chemical production processes. CO is a flammable, explosive and highly toxic gas. Excessive emissions will not only cause great harm to the ecological environment, but also pose a serious threat to the human body. NO is extremely harmful to the human body and the environment, can cause harm to the human respiratory system, form acid rain and photochemical smog, and also destroy the ozone layer.

[0003] Selective catalytic reduction technology can effectively remove NO and is the mainstream technology that has been successfully commercialized in recent years. This method uses NH3 as a reducing agent to selectively reduce NO to N2. The CO catalytic oxidation method is to catalytically convert CO into non-toxic CO2 under the action of a catalyst. This method has the advantages of high removal efficiency, low cost, deep removal, wide application range, and no secondary pollution.

[0004] However, existing commercial vanadium-tungsten-titanium catalysts often have a single function in catalytically removing nitrogen oxides (NO) and CO pollutants in industrial flue gas, are unable to remove CO effectively, and the operating temperature required for the catalytic reaction is too high.

[0005] Therefore, it is necessary to explore a catalyst that can synergistically control CO and NO in industrial flue gas, in order to provide a new idea for the research on the synergistic control of multiple pollutants in industrial flue gas. Summary of the invention

[0006] The purpose of the present invention is to provide a preparation method and application of a molecular sieve catalyst for synergistically removing CO and NO under medium and low temperature conditions, wherein Cu is used as an active ingredient, Ce is used as an auxiliary agent, and β molecular sieve is used as a carrier to prepare a CuCe / β catalyst. 2+ and CuO, the catalytic reduction of NO occurs on Cu 2+ The catalytic oxidation of CO occurs at the CuO active sites. Ce is attached to the CuO nanoclusters in the form of oxides, which promotes the formation of oxygen vacancies on the molecular sieve, thereby improving the low-temperature activity of the catalyst. Compared with other molecular sieves, the higher ion exchange capacity of β molecular sieve is more conducive to Cu 2+The catalyst is used in the steel, cement, petrochemical and other industries to remove nitrogen oxides (NO) and CO pollutants from exhaust gas to solve the problems of the above-mentioned prior art.

[0007] To achieve the above object, the present invention provides the following solutions:

[0008] One of the technical solutions of the present invention is to provide a method for preparing a CuCe / β molecular sieve catalyst, comprising the following steps:

[0009] Dissolving copper salt and cerium salt in water to prepare a mixed solution;

[0010] The beta molecular sieve is added into the mixed solution and stirred evenly, and then impregnated under heating conditions, followed by drying and calcination to obtain a CuCe / beta molecular sieve catalyst.

[0011] Furthermore, the molar ratio of Cu to Ce in the copper salt and the cerium salt is 1:0.25 to 1.25, preferably 1:0.25, 1:0.5, 1:0.75, 1:1 or 1:1.25.

[0012] Furthermore, the copper salt includes at least one of copper nitrate, copper acetate and copper chloride.

[0013] Furthermore, the cerium salt includes cerium nitrate and / or cerous nitrate.

[0014] Furthermore, the β molecular sieve is H-type, and the silicon-aluminum ratio is 10-30.

[0015] Furthermore, the mass ratio of the β molecular sieve to the copper salt is 10:0.1-1.

[0016] Furthermore, the stirring time is 5 to 30 minutes.

[0017] Furthermore, the heating temperature is 60-90°C.

[0018] Furthermore, the immersion treatment time is 1 hour.

[0019] Furthermore, the drying temperature is 80-120° C. and the drying time is 10-20 hours.

[0020] Furthermore, the calcination temperature is 400-500° C., the heating rate is 5-10 min, and the calcination time is 4-6 h.

[0021] The second technical solution of the present invention is to provide a CuCe / β molecular sieve catalyst prepared by the above method.

[0022] The third technical solution of the present invention is to provide an application of the above-mentioned CuCe / β molecular sieve catalyst for catalytically removing NO and CO from industrial flue gas under medium and low temperature conditions.

[0023] Furthermore, the temperature for catalytically removing NO and CO from industrial flue gas is 200-350°C.

[0024] The present invention discloses the following technical effects:

[0025] The present invention adopts Cu as the main active component, Ce as the auxiliary agent, and β molecular sieve as the carrier to prepare CuCe / β catalyst. Thanks to the high specific surface area and good ion exchange capacity of β molecular sieve, Cu 2+ The distribution of CuO and β on the β molecular sieve is more uniform, which further promotes the low-temperature activity of the catalyst. The catalyst has low raw material cost and simple preparation process. It is used in the steel, cement, petrochemical and other industries to remove nitrogen oxides (NO x ) and CO pollutants, the catalytic activity is good, there is a wide temperature window, and the N2 selectivity is high. In the range of 200-350°C, the NO conversion rate can reach 90%, the CO conversion rate can reach 99%, and the N2 selectivity can reach 95%. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 It is a schematic diagram of the device for the performance reaction of the catalyst in the test example;

[0028] Figure 2 is the NO conversion rate of the catalysts of Examples 1 to 5 under the test conditions;

[0029] Figure 3 is the CO conversion rate of the catalysts of Examples 1 to 5 under the test conditions;

[0030] Figure 4 The N2 selectivity results of the catalysts of Examples 1 to 5 under the test conditions;

[0031] Figure 5 It is the X-ray diffraction spectrum of the catalyst of Examples 1 to 5. DETAILED DESCRIPTION

[0032] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0033] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0034] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0035] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0036] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0037] The beta molecular sieve used in the specific embodiment of the present invention is of H type, and the silicon-aluminum ratio ranges from 25 to 30.

[0038] Example 1

[0039] The preparation steps of 8Cu-2Ce / β catalyst are as follows:

[0040] 0.188 g of copper nitrate and 0.062 g of cerium nitrate were added to deionized water (50 mL) and ultrasonically stirred for 20 min to form an impregnation solution; the impregnation solution was mixed with 0.90 g of Beta (β) molecular sieve and stirred for 30 min, and then stirred and impregnated in a water bath (90°C) for 1 h, then stirred in a fume hood until a viscous gel-like substance was obtained, and then transferred to a 110°C drying oven for 12 h. The obtained solid was ground into powder and placed in a muffle furnace and heated to 500°C at a rate of 10°C / min and calcined for 5 h to obtain a 8Cu-2Ce / β catalyst, recorded as Cu8Ce2 / β.

[0041] Example 2

[0042] The preparation steps of 8Cu-4Ce / β catalyst are as follows:

[0043] 0.188 g of copper nitrate and 0.124 g of cerium nitrate were added to deionized water (50 mL) and ultrasonically stirred for 20 min to form an impregnation solution; the impregnation solution was mixed with 0.88 g of Beta (β) molecular sieve and stirred for 20 min, and then stirred and impregnated in a water bath (80°C) for 1 h, then stirred in a fume hood until a viscous gel-like substance was obtained, and then transferred to a 110°C drying oven for drying for 12 h. The obtained solid was ground into powder and placed in a muffle furnace for heating at a rate of 10°C / min, and calcined at 500°C for 5 h to obtain a 8Cu-4Ce / β catalyst, recorded as Cu8Ce4 / β.

[0044] Example 3

[0045] The preparation steps of 8Cu-6Ce / β catalyst are as follows:

[0046] 0.188 g of copper nitrate and 0.186 g of cerium nitrate were added to deionized water (50 mL) and ultrasonically stirred for 20 min to form an impregnation solution; the impregnation solution was mixed with 0.86 g of Beta (β) molecular sieve and stirred for 30 min, and then sealed and stirred for 1 h in a water bath (80°C), and then opened in a fume hood and stirred until a viscous gel-like substance was obtained, and then transferred to a 110°C drying oven for drying for 12 h; the obtained solid was ground into powder and placed in a muffle furnace for heating at a rate of 10°C / min, and calcined at 500°C for 5 h to obtain a 8Cu-6Ce / β catalyst, recorded as Cu8Ce6 / β.

[0047] Example 4

[0048] The preparation steps of 8Cu-8Ce / β catalyst are as follows:

[0049] 0.188 g of copper nitrate and 0.248 g of cerium nitrate were added to deionized water (50 mL) and ultrasonically stirred for 20 min to form an impregnation solution; the impregnation solution was mixed with 0.84 g of Beta (β) molecular sieve and stirred for 20 min, and then sealed and stirred for 1 h in a water bath (90°C) and then stirred in a fume hood until a viscous gel-like substance was obtained, and then dried in a 110°C drying oven for 12 h; the obtained solid was ground into powder and placed in a muffle furnace for heating at a rate of 10°C / min, and calcined at 500°C for 5 h to obtain a 8Cu-8Ce / β catalyst, recorded as Cu8Ce8 / β.

[0050] Example 5

[0051] The preparation steps of 8Cu-10Ce / β catalyst are as follows:

[0052] 0.188g of copper nitrate and 0.310g of cerium nitrate were added to deionized water (50mL) and ultrasonically stirred for 20min to form an impregnation solution; the impregnation solution was mixed with 0.82g of Beta (β) molecular sieve and stirred for 30min, and then sealed and stirred for 1h in a water bath (90°C), and then stirred in a fume hood until a viscous gel-like substance was formed, and then dried in a 110°C drying oven for 12h; the obtained solid was ground into powder and placed in a muffle furnace for heating at a rate of 10°C / min, and calcined at 500°C for 5h to obtain 8Cu-10Ce / β catalyst, denoted as Cu8Ce 10 / β.

[0053] The catalysts prepared in Examples 1 to 5 were subjected to catalyst performance evaluation in a fixed bed apparatus. Figure 1 As shown, the specific operations are as follows:

[0054] The catalysts prepared in Examples 1 to 5 were placed in the isothermal zone of a reaction tube, and the flue gas entered the reaction tube, where a selective catalytic reduction denitration reaction was carried out (inner diameter 6 mm, sample amount: 100 mg).

[0055] Steel gas cylinders are used to simulate the flue gas composition. Gases from various pipelines enter the gas mixer through mass flow meters for balanced mixing before entering the reactor.

[0056] The concentrations of NO, NO2, NH3, N2O, CO, and CO2 were measured at 100-400°C using a Bruker Fourier transform infrared spectrometer. The NO and CO conversion efficiencies and N2 selectivity were calculated based on this. To ensure the stability and accuracy of the data, each 25°C condition was considered as one operating condition, and each condition was stable for at least 30 minutes.

[0057] Test conditions: NO 500ppm, NH3 500ppm, CO 5000ppm, O2 5%, N2 as balance gas, gas hourly space velocity (GHSV) 60000mL·g -1 ·h -1 , the total gas flow rate is 200mL / min.

[0058] Figure 2 The NO conversion rates of the catalysts of Examples 1 to 5 under the test conditions are shown in the figure. As can be seen from the figure, with the increase of temperature, the denitration efficiency of the catalysts first increases and then slightly decreases and tends to be stable. The denitration efficiency of the catalyst reaches a maximum at 175°C. Among them, the molecular sieve catalyst doped with copper and cerium has an average NO removal efficiency of more than 80% within the range of 175°C to 350°C, and has a wide temperature window and high stability.

[0059] Figure 3 The CO conversion rates of the catalysts of Examples 1 to 5 under the test conditions are shown in the figure. As can be seen from the figure, with the increase of temperature, the CO removal efficiency of the catalysts first increases and then tends to be stable. Among them, the CO removal efficiency of the catalyst of Example 4 is close to 100% within the range of 200°C to 400°C, and it largely overlaps with the temperature window of the denitrification efficiency, indicating excellent synergistic removal performance.

[0060] Figure 4 The N2 selectivity results of the catalysts of Examples 1 to 5 under the test conditions are shown in the figure. It can be seen from the figure that the catalysts have good N2 selectivity.

[0061] Figure 5 3 are X-ray diffraction spectra of the catalysts of Examples 1 to 5. It can be seen from the figure that the catalysts prepared in Examples 1 to 5 show characteristic peaks belonging to β molecular sieves, and the positions of the diffraction peaks of β molecular sieves are not changed by loading the active components Cu and Ce, indicating that the loaded components do not change the skeleton structure of the molecular sieve.

[0062] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing a CuCe / β molecular sieve catalyst, characterized in that the steps include: Dissolving copper salt and cerium salt in water to prepare a mixed solution; The beta molecular sieve is added into the mixed solution and stirred evenly, and then impregnated under heating conditions, followed by drying and calcination to obtain a CuCe / beta molecular sieve catalyst.

2. The preparation method according to claim 1, characterized in that The copper salt includes at least one of copper nitrate, copper acetate and copper chloride; the cerium salt includes cerium nitrate and / or cerous nitrate; the beta molecular sieve is H type, and the silicon-aluminum ratio is 10-30.

3. The preparation method according to claim 1, characterized in that: The molar ratio of Cu to Ce in the copper salt and the cerium salt is 1:0.25-1.

25.

4. The preparation method according to claim 1, characterized in that: The mass ratio of the beta molecular sieve to the copper salt is 10:0.1-1.

5. The preparation method according to claim 1, characterized in that: The stirring time is 5 to 30 minutes.

6. The preparation method according to claim 1, characterized in that: The heating temperature is 60-90° C.; the immersion treatment time is 1 hour.

7. The preparation method according to claim 1, characterized in that: The drying temperature is 80-120° C. and the drying time is 10-20 hours.

8. The preparation method according to claim 1, characterized in that: The calcination temperature is 400-500° C., the heating rate is 5-10 min, and the calcination time is 4-6 h.

9. The CuCe / β molecular sieve catalyst prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the CuCe / β molecular sieve catalyst according to claim 9 for catalytic removal of NO and CO from industrial flue gas under medium and low temperature conditions, characterized in that: The temperature for catalytically removing NO and CO from industrial flue gas is 200-350°C.

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