A high performance copper-based denitrification catalyst and its preparation method and application

Abstract

The invention discloses a high-performance copper-based denitration catalyst, which is prepared by fully grinding a copper-based catalyst CuO-SBA doped with a molecular sieve ZSM-5; the copper-based catalyst CuO-SBA is prepared by mixing Cu(NO3)2·3H2O and SBA-15 and grinding and then roasting. The invention adopts a solid phase grinding method to dope the copper-based catalyst with a molecular sieve, and the preparation method is simple and fast. No solvent is used in the preparation process to effectively avoid the loss of active species. The prepared catalyst has high thermal stability and excellent catalytic performance.

Description

Technical Field

[0001] The invention relates to the technical field of nitrogen oxide pollution control in the atmosphere, and more specifically to a method for preparing a high-performance copper-based denitration catalyst by a solid phase grinding method. Background Art

[0002] Nitrogen oxides (NO x ) is one of the main pollutants in the atmosphere, causing a series of severe climate problems such as acid rain and greenhouse effect, having a huge impact on soil and buildings, and posing a serious threat to the entire ecological environment and human health. Ammonia selective catalytic reduction (NH3-SCR) of nitrogen oxides is recognized as the most effective and widely used NO x Emission reduction technology, which has the characteristics of mature process, high removal efficiency and stable system operation, is the preferred NO x One of the emission control measures. The core of its denitrification efficiency is the development of catalysts. In the process of catalytic oxidation of NO, the temperature exceeding 200°C will cause the stability of the oxidized NO2 to decrease. However, many catalysts need to be at a high temperature of over 300°C to maintain good catalytic activity, while the emission temperature of industrial coal-fired flue gas is generally 150-250°C. Therefore, it is necessary to develop catalysts suitable for low-temperature catalytic oxidation of NO.

[0003] Metal molecular sieve catalysts have received extensive attention in the field of denitrification in recent years, especially copper-based catalysts, which are one of the most promising catalysts for low-temperature NH3-SCR processes. However, the catalytic activity of copper-based catalysts such as Cu-SSZ-13, Cu-SPAO-34, and Cu-MCM-41 reported so far is not ideal in the low-temperature range. In addition, according to previous research results, the type of porous structure and the silicon-aluminum ratio can affect the catalytic activity of zeolite molecular sieves in NH3-SCR to a certain extent. Summary of the invention

[0004] The purpose of the present invention is to provide a denitration catalyst having high performance in a low temperature region.

[0005] The hexagonal SBA-15 mesoporous molecular sieve has thicker pore walls and better thermal stability, which can effectively improve the dispersion of the catalytic active components of the catalyst. The ZSM-5 molecular sieve has a unique cross-channel structure, high hydrothermal stability, large specific surface area, strong acid stability, and selective catalytic performance.

[0006] The present invention adopts a simple solid phase method and combines the advantages of SBA-15 mesoporous molecular sieve and ZSM-5 molecular sieve to prepare a high-performance CuO-SBA-15 / ZSM-5 catalyst, which exhibits excellent catalytic performance in industrial coal-fired flue gas denitrification.

[0007] In order to achieve the above-mentioned purpose, the present invention provides a high-performance copper-based denitration catalyst. The high-performance copper-based denitration catalyst is prepared by fully grinding a copper-based catalyst CuO-SBA doped with a molecular sieve ZSM-5; the copper-based catalyst CuO-SBA is prepared by mixing Cu(NO3)2·3H2O and SBA-15 and grinding and then roasting; the copper element in the copper-based catalyst CuO-SBA accounts for 40% by mass in terms of CuO; the mass ratio of the copper-based catalyst CuO-SBA to the molecular sieve ZSM-5 is 0.5:1 to 1:1; the molecular sieve ZSM-5 uses a molecular sieve ZSM-5 with a silicon-aluminum ratio of 25 to 35.

[0008] Preferably, the copper element in the copper-based catalyst CuO-SBA accounts for 40% by mass as CuO. Preferably, the mass ratio of the copper-based catalyst CuO-SBA to the molecular sieve ZSM-5 is 1:1

[0009] The present invention also provides a method for preparing the above-mentioned high-performance copper-based denitration catalyst, comprising the following steps:

[0010] (1) Preparation of copper-based catalysts:

[0011] 0.168 g of Cu(NO3)2·3H2O and 0.12 g of molecular sieve SBA-15 were fully ground until there was no particle feeling, and the temperature was raised to 450°C±5°C at a heating rate of 3°C / min, and then kept warm and calcined for 4±0.2 hours to prepare a copper-based catalyst CuO-SBA;

[0012] (2) Composite doped molecular sieve:

[0013] The prepared copper-based catalyst CuO-SBA is fully ground with molecular sieve ZSM-5 according to a mass ratio until there is no particle feeling, so as to obtain the high-performance copper-based denitration catalyst.

[0014] Preferably, the molecular sieve ZSM-5 uses a molecular sieve ZSM-5 with a silicon-aluminum ratio of 25 to 35, and the mass ratio of the copper-based catalyst CuO-SBA to the molecular sieve ZSM-5 is 1:1.

[0015] Preferably, the molecular sieve SBA-15 is prepared by the following method: 4.0 g of P123, 130 ml of H2O, and 20 ml of concentrated HCl are weighed in a beaker, and stirred in an oil bath until the solution is clear; then 9.6 ml of TEOS is added, and stirred in a constant temperature oil bath at 40°C for 24 hours, and the resulting white gel is transferred to a stainless steel hydrothermal kettle lined with polytetrafluoroethylene, and after hydrothermal reaction in an oven at 100°C for 24 hours, it is taken out and cooled, washed with water 3 times, washed with ethanol 3 times, and then dried in an oven at 100°C for 10 hours to obtain an ordered mesoporous molecular sieve SBA-15.

[0016] The present invention also provides the use of the high-performance copper-based denitration catalyst in denitration catalysis at a temperature of 150°C to 200°C.

[0017] Compared with the prior art, the present invention has the following advantages:

[0018] 1. The present invention adopts a solid phase grinding method to dope the copper-based catalyst with a molecular sieve. The preparation method is simple and fast, and no solvent is used in the preparation process to effectively avoid the loss of active species. The prepared catalyst has high thermal stability and excellent catalytic performance.

[0019] 2. The present invention obtains a catalyst suitable for low-temperature catalytic oxidation of NO by optimizing and screening process conditions such as the selection and ratio of raw materials for preparation and the composite mode of molecular sieves, and has potential industrial application prospects.

[0020] 3. The raw materials used are cheap, easily available and abundant in resources.

[0021] 4. The catalyst is prepared by solid phase grinding method, which has low energy consumption, low pollution and is environmentally friendly; BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is the XRD pattern of the molecular sieve SBA-15 prepared by the present invention;

[0023] Figure 2 This is a comparison chart of NO conversion rates of different copper-based catalysts CuO-SBA-15 obtained in Screening Example 1;

[0024] Figure 3 It is a comparison chart of NO conversion rates of different copper-based catalysts CuO-SBA-15 and CuO-SBA-15 / ZSM-5 obtained in Screening Example 2 and Screening Example 3;

[0025] Figure 4 A comparison chart of NO conversion rates of different copper-based denitration catalysts obtained in Screening Example 4;

[0026] Figure 5 This is a comparison chart of the NO conversion rates of different copper-based denitration catalysts CuO-SBA-15 / ZSM-5 obtained in screening Example 5. DETAILED DESCRIPTION

[0027] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] The molecular sieve catalyst ZSM-5 used in this example was purchased from Zhuoran Environmental Technology Dalian Co., Ltd.

[0029] The catalytic performance test conditions of each catalyst material obtained in this example are as follows: the catalytic reaction test is carried out in a fixed bed continuous flow quartz reactor. The catalyst particle size is 20-40 mesh, and the dosage is 100 mg. The reaction gas composition is: 500ppm NO, 500ppm NH3, 100ppm SO2, 5% H2O, 5% O2, N2 as the balance gas, and the gas space velocity in the reaction is 60000mL·mg -1 ·h -1 Before the reaction, the catalyst needs to be purged with high-purity N2 at 150°C for 0.5h. The catalytic reaction is carried out at 150-200°C, and the activity data is collected after the reaction reaches equilibrium. The NO conversion rate is calculated by the following formula:

[0030]

[0031] Molecular sieve SBA-15 is prepared by the following method:

[0032] Weigh 4.0g of P123, 130ml of H2O, and 20ml of concentrated HCl in a beaker, and stir in an oil bath until the solution is clear. Then add 9.6ml of TEOS, stir in a 40℃ constant temperature oil bath for 24h, transfer the resulting white gel to a stainless steel hydrothermal kettle lined with polytetrafluoroethylene, and after hydrothermal reaction in a 100℃ oven for 24h, take it out and cool it, wash it with water 3 times, wash it with ethanol 3 times, and then put it in an oven at 100℃ to dry for 10h to obtain the ordered mesoporous molecular sieve SBA-15. Its XRD is shown in the attached Figure 1 As can be seen from the figure, there is a strong diffraction peak and two weaker diffraction peaks, which is the typical hexagonal mesoporous structure of SBA-15. This shows that the prepared SBA-15 sample is successful.

[0033] Screening Example 1

[0034] Preparation of CuO-SBA-15 catalysts with different contents

[0035] Weigh 0.042g Cu(NO3)2·3H2O and 0.18g SBA-15 into an agate mortar and grind them for 0.5h. After grinding until there is no particle feeling, put them into a crucible and place them in a muffle furnace. Heat the temperature to 450℃ at a heating rate of 3℃ / min and keep the calcination time for 4h to obtain 0.18g of copper-based catalyst, in which the Cu element content is about 10% by mass based on CuO. The copper-based catalyst is recorded as 10CuO-SBA-15 (SSI).

[0036] Weigh 0.084 g Cu(NO3)2·3H2O and 0.16 g SBA-15 into an agate mortar and grind them for 0.5 h. After grinding until there is no particle feeling, put them into a crucible and place them in a muffle furnace. The temperature is increased to 450°C at a heating rate of 3°C / min and the calcination time is retained for 4 h to obtain 0.18 g of a copper-based catalyst, in which the Cu element content is about 20% by mass based on CuO. The copper-based catalyst is recorded as 20CuO-SBA-15 (SSI).

[0037] Weigh 0.126g Cu(NO3)2·3H2O and 0.14g SBA-15 into an agate mortar and grind them for 0.5h. After grinding until there is no granularity, put them into a crucible and place them in a muffle furnace. The temperature is increased to 450℃ at a heating rate of 3℃ / min. The calcination time is retained for 4h to obtain 0.18g of copper-based catalyst, in which the Cu element content is about 30% by mass based on CuO. The copper-based catalyst is recorded as 20CuO-SBA-15 (SSI).

[0038] Weigh 0.168g Cu(NO3)2·3H2O and 0.12g SBA-15 into an agate mortar and grind them for 0.5h. After grinding until there is no particle feeling, put them into a crucible and place them in a muffle furnace. The temperature is increased to 450℃ at a heating rate of 3℃ / min. The calcination time is retained for 4h to obtain 0.18g of copper-based catalyst, in which the Cu element content is about 40% by mass based on CuO. The copper-based catalyst is recorded as 40CuO-SBA-15 (SSI).

[0039] The NH3-SCR activity results of the four copper-based catalysts CuO-SBA-15 prepared above are shown in Figure 2 ,It can be seen from the figure that 40CuO-SBA-15(SSI) has the best catalytic performance.

[0040] Screening Example 2

[0041] Preparation of Copper-based Catalyst 40CuO-SBA-15(WI)

[0042] Weigh 0.168g Cu(NO3)2·3H2O and 0.12g SBA-15Cu(NO3)2·3H2O, add 20ml water, mix and impregnate for 2h, then heat in an oil bath at 100℃ to evaporate water, then dry in an oven at 110℃ overnight, finally put into a crucible and place in a muffle furnace, heat to 450℃ at a heating rate of 3℃ / min, and keep the calcination time for 4h to obtain 40CuO-SBA-15(WI) copper-based catalyst. The comparison of its NH3-SCR activity results with those of 40CuO-SBA-15(SSI) prepared in Screening Example 2 is shown in Figure 3As can be seen from the figure, 40CuO-SBA-15 (SSI) has significant superiority in catalytic performance at low temperature range of 150℃~200℃.

[0043] Screening Example 3

[0044] Preparation of copper-based denitrification catalyst 40CuO-SBA-15 / ZSM-5 (SSI)

[0045] Take the 40CuO-SBA-15 (SSI) copper-based catalyst prepared in the screening example 1, add molecular sieve ZSM-5 with a silicon-aluminum ratio of 25-35, 45-55, 65-75, 80-90 at a mass ratio of 1:1, grind thoroughly, and prepare 40CuO-SBA-15 / ZSM-5 copper-based catalysts, which are respectively recorded as 40CuO-SBA-15 (ZSM5-25-35) SSI, 40CuO-SBA-15 (ZSM5-45-55) SSI, 40CuO-SBA-15 (ZSM5-65-75) SSI, and 40CuO-SBA-15 (ZSM5-80-90) SSI. The NH3-SCR activity results of each copper-based catalyst are shown in Figure 3 .

[0046] It can be seen from the figure that when the molecular sieve adopts ZSM-5 with a silicon-aluminum ratio of 25 to 35, the prepared 40CuO-SBA-15 (ZSM5-25-35) SSI catalyst has the best catalytic performance.

[0047] Screening Example 4

[0048] Preparation of copper-based catalyst SBA-15-ZSM5-25-35-CuO SSI

[0049] Take 0.12g molecular sieve SBA and 0.18g molecular sieve ZSM with a silicon-aluminum ratio of 25-35 and grind them thoroughly, then add 0.168g Cu(NO3)2·3H2O, grind them in an agate mortar for 0.5h, grind until there is no granularity, put them into a crucible and place them in a muffle furnace, heat them to 450℃ at a heating rate of 3℃ / min, and retain the calcination time for 4h to obtain 0.32g of copper-based catalyst SBA-15-ZSM5-25-35-CuO SSI, and compare its NH3-SCR activity with that of the copper-based denitration catalyst 40CuO-SBA-15 (ZSM5-25-35) SSI prepared in Screening Example 3. Figure 4 shown.

[0050] As can be seen from the figure, when the method of the present invention is used to first prepare CuO-SBA-15 and then solid-phase grind it with ZSM-5 to obtain a catalyst, the catalytic performance in the low temperature range of 150°C to 200°C is significantly superior to the catalyst obtained by directly mixing the molecular sieve and then solid-phase grinding and calcining it with a copper catalyst.

[0051] Screening Example 5

[0052] Effect of different ratios of copper-based catalyst CuO-SBA-15 and molecular sieve ZSM-5 on catalytic performance

[0053] Take the 40CuO-SBA-15 (SSI) copper-based catalyst prepared in the screening example 1, and then add the molecular sieve ZSM-5 with a silicon-aluminum ratio of 25 to 35 at a mass ratio of 1:1, 0.5:1, and 2:1, respectively, and grind it fully to obtain the 40CuO-SBA-15 / ZSM-5 copper-based catalyst, which are respectively recorded as 40CuO-SBA-15 (ZSM5-25-351:1), 40CuO-SBA-15 (ZSM5-25-350.5:1), and 40CuO-SBA-15 (ZSM5-25-352:1). The NH3-SCR activity results of each copper-based catalyst are shown in Figure 5 .

[0054] It can be seen from the figure that the 40CuO-SBA-15 (ZSM5-25-351:1) catalyst prepared by mixing the 40CuO-SBA-15 (SSI) copper-based catalyst with the molecular sieve ZSM-5 in a mass ratio of 1:1 has better catalytic performance.

Claims

1. A high performance copper-based denitration catalyst, characterized in that: The high-performance copper-based denitration catalyst is prepared by fully grinding a copper-based catalyst CuO-SBA doped with a molecular sieve ZSM-5; the copper-based catalyst CuO-SBA is prepared by mixing and grinding Cu(NO3)2·3H2O and SBA-15 and then calcining; the copper element in the copper-based catalyst CuO-SBA accounts for 40% by mass in terms of CuO; the mass ratio of the copper-based catalyst CuO-SBA to the molecular sieve ZSM-5 is 0.5:1 to 1:1; the molecular sieve ZSM-5 uses a molecular sieve ZSM-5 with a silicon-aluminum ratio of 25 to 35; after the Cu(NO3)2·3H2O and SBA-15 are mixed and ground, the temperature is increased to 450°C±5°C at a heating rate of 3°C / min, and the mixture is kept warm and calcined for 4±0.2 hours to prepare the copper-based catalyst CuO-SBA.

2. The high performance copper-based denitration catalyst according to claim 1, characterized in that: The mass ratio of the copper-based catalyst CuO-SBA to the molecular sieve ZSM-5 is 1:

1.

3. The method for preparing the high-performance copper-based denitration catalyst according to claim 1, characterized in that: The following steps are involved: Preparation of copper-based catalysts: 0.168 g of Cu(NO3)2·3H2O and 0.12 g of molecular sieve SBA-15 were fully ground until there was no particle feeling, and the temperature was raised to 450°C±5°C at a heating rate of 3°C / min, and then kept at this temperature for 4±0.2 hours to prepare a copper-based catalyst CuO-SBA; Composite doped molecular sieve: The prepared copper-based catalyst CuO-SBA is fully ground with molecular sieve ZSM-5 according to a mass ratio until there is no particle feeling, so as to obtain the high-performance copper-based denitration catalyst.

4. The preparation method according to claim 3, characterized in that: The molecular sieve ZSM-5 uses a molecular sieve ZSM-5 with a silicon-aluminum ratio of 25 to 35, and the mass ratio of the copper-based catalyst CuO-SBA to the molecular sieve ZSM-5 is 1:

1.

5. The preparation method according to claim 3, characterized in that: The molecular sieve SBA-15 is prepared by the following method: 4.0 g of P123, 130 ml of H2O, and 20 ml of concentrated HCl are weighed in a beaker, and the mixture is placed in an oil bath and stirred until the solution becomes clear; then 9.6 ml of TEOS is added, and the mixture is stirred in a constant temperature oil bath at 40° C. for 24 hours, and the obtained white gel is transferred to a stainless steel hydrothermal kettle lined with polytetrafluoroethylene, and after hydrothermal reaction in an oven at 100° C. for 24 hours, the gel is taken out and cooled, washed with water 3 times, washed with ethanol 3 times, and then placed in an oven at 100° C. for 10 hours to obtain an ordered mesoporous molecular sieve SBA-15.

6. Use of the high-performance copper-based denitration catalyst according to any one of claims 1 to 2 in denitration catalysis at a temperature of 150°C to 200°C.

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