A method and application of preparing Cu-SSZ-13 molecular sieve catalyst by mechanically pressurized water heat exchange loaded copper

Abstract

The present invention relates to the field of catalyst preparation, and discloses a method for preparing a Cu-SSZ-13 molecular sieve catalyst by mechanical pressure hydrothermal exchange loading of copper and its application. The method includes steps such as preparation of a copper acetate solution, adjustment of acidity and alkalinity, mechanical pressure and hydrothermal exchange, and post-treatment. The present invention uses the method of mechanical pressure hydrothermal exchange to load copper on the SSZ-13 molecular sieve, improving the dispersion degree of copper on the catalyst and inhibiting the formation of Cu + and CuO that is not conducive to the NH3-SCR performance of the catalyst, effectively avoiding the occurrence of ammonia oxidation reaction; the Cu-SSZ-13 molecular sieve catalyst exhibits excellent denitrification activity and good hydrothermal stability in the NH3-SCR reaction; the preparation method is simple and easy to implement, with the advantages of short cycle, low cost, and less energy consumption, being conducive to popularization and application in large-scale production.

Description

Technical Field

[0001] The invention relates to the technical field of catalyst preparation, and in particular to a method for preparing a Cu-SSZ-13 molecular sieve catalyst by mechanically pressurized water heat exchange loaded copper and application thereof. Background Art

[0002] In recent years, with the rapid development of social economy, the use of fossil fuels such as oil and coal has increased, and at the same time, environmental pollution and other problems have become increasingly serious. Among them, nitrogen oxides (NO x ) is the main byproduct of fossil fuel combustion and one of the main air pollutants; NO x Large-scale emissions of NO will lead to increased photochemical smog and ozone concentrations, seriously endangering human health and the living environment. x Emission standards are becoming increasingly stringent. Currently, selective catalytic reduction (SCR) using ammonia (NH3) is one of the most mature and effective technologies for suppressing NO emissions from oxygen-containing exhaust gases (such as diesel exhaust).

[0003] The key to NH3-SCR denitrification technology lies in the selection of denitrification catalysts. Denitrification catalysts directly affect the range of denitrification temperature windows and denitrification efficiency. Therefore, the design and development of denitrification catalysts is the focus of current research. Molecular sieves are widely used in the field of environmental catalysis due to their advantages such as large specific surface area, rich pore structure and strong stability. Among them, SSZ-13, as a silicon-aluminum molecular sieve with a chabazite structure, has a small pore opening, which effectively inhibits the skeleton dealumination products from leaving the pores. Cu-SSZ-13 molecular sieve catalyst has a wider active temperature window, higher N2 selectivity and excellent hydrothermal stability in NH3-SCR, and has been widely used in the denitrification treatment process of diesel vehicle exhaust.

[0004] At present, there are two main methods for preparing Cu-SSZ-13 molecular sieve catalysts. One is a one-step synthesis method. For example, Wang et al. (Chem. Commun., 2021, 57, 4898-4901) used N, N, N-trimethyl-1-adamantane ammonium hydroxide (TMAdaOH) and copper amine complex co-template to synthesize Cu-SSZ-13 molecular sieve catalysts in one step. However, this method has a long synthesis cycle and the copper loading in the catalyst is too high, resulting in ammonia oxidation during the NH3-SCR process. At the same time, the hydrothermal aging resistance is poor. Another method is the ion exchange method. Zhang et al. (CN111408401B) first used NH4 + Ion exchange with Na-SSZ-13 to obtain NH4-SSZ-13 molecular sieve, and then Cu 2+Ion exchange with NH4-SSZ-13 was performed to obtain Cu-SSZ-13 catalyst; the main disadvantage of this method is that CuO and Cu are easily generated during the preparation process. + , reducing the Cu that plays a major role in the reaction process 2+ The content of copper in the SSZ-13 molecular sieve is poorly dispersed, which reduces the utilization of copper, reduces the activity of the catalyst, and introduces NH4 + The process makes the operation steps cumbersome and time-consuming. Summary of the invention

[0005] In order to overcome the defects of the prior art, the present invention provides a method and application of preparing Cu-SSZ-13 molecular sieve catalyst by mechanical pressurized water heat exchange loaded copper, and the technical scheme is as follows:

[0006] A method for preparing a Cu-SSZ-13 molecular sieve catalyst by mechanically pressurized water heat exchange with copper, comprising the following steps:

[0007] (1) Preparation of copper acetate solution: Mix copper acetate monohydrate with deionized water and stir until the copper acetate is completely dissolved to obtain a uniformly dispersed copper acetate solution;

[0008] (2) pH adjustment: slowly adding acetic acid to the copper acetate solution obtained in step (1) to adjust the pH value of the solution;

[0009] (3) Mechanical pressurization and hydrothermal exchange: Add SSZ-13 molecular sieve to the solution adjusted in step (2), stir the solution evenly and transfer it into the Teflon lining of the hydrothermal reactor; then place the hydrothermal reactor in a rotary oven for rotary pressurization;

[0010] (4) Post-treatment: The pressurized solution in step (3) is filtered, washed with deionized water, dried, and then placed in a muffle furnace and calcined under programmed temperature to obtain a Cu-SSZ-13 molecular sieve catalyst.

[0011] Furthermore, the mass ratio of the copper acetate monohydrate in step (1) to the SSZ-13 molecular sieve in step (3) is 4:25.

[0012] Furthermore, the mass concentration of acetic acid in step (2) is 99.5%.

[0013] Furthermore, in step (2), the pH value of the solution is adjusted to 1-5.

[0014] Furthermore, in step (3), the temperature of the rotary oven is 80-200° C., and the rotary pressurizing time is 6 hours.

[0015] Furthermore, the SSZ-13 molecular sieve used in step (3) is a pretreated molecular sieve.

[0016] Furthermore, the pretreatment is to calcine the SSZ-13 molecular sieve in a muffle furnace at 550° C. for 4 hours.

[0017] Furthermore, in step (4), the drying temperature is 100°C; the roasting temperature is 550°C, the heating rate is 5°C / min, and the roasting time is 4h.

[0018] The application of the Cu-SSZ-13 molecular sieve catalyst prepared according to the above method in the NH3-SCR denitration reaction is evaluated under the following reaction conditions: the catalyst with a sieved size of 40 to 60 mesh is loaded in the reaction tube with a filling volume of 1 mL and a space velocity of 60,000 h -1 The composition of the reaction mixture gas is: 500 pm NO, 500 ppm NH3, 5% O2, and N2 is the balance gas. The heating rate during the evaluation is 5°C / min, and the concentration of each component in the exhaust gas is measured at a constant temperature of 30°C for 0.5 h.

[0019] Compared with the prior art, the present invention mainly has the following beneficial technical effects:

[0020] 1. The present invention adopts the method of mechanical pressurized water heat exchange to load copper on SSZ-13 molecular sieve, which improves the dispersion of copper on the catalyst and inhibits the Cu ions that are not conducive to the NH3-SCR performance of the catalyst. + and CuO, effectively avoiding the occurrence of ammonia oxidation reaction.

[0021] 2. The Cu-SSZ-13 molecular sieve catalyst prepared in the present invention exhibits excellent denitration activity and good hydrothermal stability in the NH3-SCR reaction.

[0022] 3. The preparation method of the Cu-SSZ-13 molecular sieve catalyst of the present invention is simple and easy, and has the advantages of short cycle, low cost and low energy consumption, which is conducive to promotion and application in large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The XRD pattern of the Cu-SSZ-13 molecular sieve catalyst provided in Example 7 of the present invention;

[0024] Figure 2 This is a SEM image of the Cu-SSZ-13 molecular sieve catalyst provided in Example 7 of the present invention;

[0025] Figure 3 A comparison chart of NO conversion rates of the Cu-SSZ-13 molecular sieve catalysts provided in Examples 1 to 5 of the present invention;

[0026] Figure 4A comparison chart of NO conversion rates of the Cu-SSZ-13 molecular sieve catalysts provided in Examples 4, 6, 7, and 8 of the present invention;

[0027] Figure 5 The catalytic performance of the Cu-SSZ-13 molecular sieve catalyst prepared in Example 7 of the present invention was evaluated before and after hydrothermal aging at 600° C. for 24 h in a 10% H 2 O air atmosphere. DETAILED DESCRIPTION

[0028] The present invention is described in detail below by specific examples, which are only used to illustrate the present invention and are not intended to limit the present invention. The raw materials, reagents, etc. used in the following examples, unless otherwise specified, are all commercially available from conventional markets. Example 1

[0029] (1) Mix 0.39 g of Cu(CH3COO)2·H20 with 50 mL of deionized water and stir until the copper acetate is completely dissolved to form a uniformly mixed copper acetate solution. Slowly drop 99.5% acetic acid solution into the copper acetate solution and adjust the pH value of the solution to 1. Then add 2.5 g of pretreated SSZ-13 molecular sieve (pretreatment is to calcine the SSZ-13 molecular sieve in a muffle furnace at 550°C for 4 h) to the solution and stir the solution to mix evenly.

[0030] (2) The mixed solution was transferred into a Teflon liner, and the hydrothermal autoclave was placed in a rotary oven, and rotated and pressurized at 120 °C for 6 h.

[0031] (3) The obtained solution was filtered, washed with deionized water, and dried in a constant temperature drying oven at 100°C for 8 h. The dried product was placed in a muffle furnace and calcined at 550°C for 4 h at a heating rate of 5°C / min. The obtained catalyst was recorded as Cu-SSZ-13-1. Example 2

[0032] (1) Mix 0.39 g of Cu(CH3COO)2·H20 with 50 mL of deionized water and stir until the copper acetate is completely dissolved to form a uniformly mixed copper acetate solution. Slowly drop 99.5% acetic acid solution into the copper acetate solution and adjust the pH value of the solution to 2. Then add 2.5 g of pretreated SSZ-13 molecular sieve (pretreatment is to calcine the SSZ-13 molecular sieve in a muffle furnace at 550°C for 4 h) to the solution and stir the solution to mix evenly.

[0033] (2) The mixed solution was transferred into a Teflon liner, and the hydrothermal autoclave was placed in a rotary oven, and rotated and pressurized at 120 °C for 6 h.

[0034] (3) The obtained solution was filtered, washed with deionized water, and dried in a constant temperature drying oven at 100°C for 8 h. The dried product was placed in a muffle furnace and calcined at 550°C for 4 h at a heating rate of 5°C / min. The obtained catalyst was recorded as Cu-SSZ-13-2. Example 3

[0035] (1) Mix 0.39 g of Cu(CH3COO)2·H20 with 50 mL of deionized water and stir until the copper acetate is completely dissolved to form a uniformly mixed copper acetate solution. Slowly drop 99.5% acetic acid solution into the copper acetate solution and adjust the pH value of the solution to 3. Then add 2.5 g of pretreated SSZ-13 molecular sieve (pretreatment is to calcine the SSZ-13 molecular sieve in a muffle furnace at 550°C for 4 h) to the solution and stir the solution to mix evenly.

[0036] (2) The mixed solution was transferred into a Teflon liner, and the hydrothermal autoclave was placed in a rotary oven, and rotated and pressurized at 120 °C for 6 h.

[0037] (3) The obtained solution was filtered, washed with deionized water, and dried in a constant temperature drying oven at 100°C for 8 h. The dried product was placed in a muffle furnace and calcined at 550°C for 4 h at a heating rate of 5°C / min. The obtained catalyst was recorded as Cu-SSZ-13-3. Example 4

[0038] (1) Mix 0.39 g of Cu(CH3COO)2·H20 with 50 mL of deionized water and stir until the copper acetate is completely dissolved to form a uniformly mixed copper acetate solution. Slowly drop 99.5% acetic acid solution into the copper acetate solution and adjust the pH value of the solution to 4. Then add 2.5 g of pretreated SSZ-13 molecular sieve (pretreatment is to calcine the SSZ-13 molecular sieve in a muffle furnace at 550°C for 4 h) to the solution and stir the solution to mix evenly.

[0039] (2) The mixed solution was transferred into a Teflon liner, and the hydrothermal autoclave was placed in a rotary oven, and rotated and pressurized at 120 °C for 6 h.

[0040] (3) The obtained solution was filtered, washed with deionized water, and dried in a constant temperature drying oven at 100°C for 8 h. The dried product was placed in a muffle furnace and calcined at 550°C for 4 h at a heating rate of 5°C / min. The obtained catalyst was recorded as Cu-SSZ-13-4. Example 5

[0041] (1) Mix 0.39 g of Cu(CH3COO)2·H20 with 50 mL of deionized water and stir until the copper acetate is completely dissolved to form a uniformly mixed copper acetate solution. Slowly drop 99.5% acetic acid solution into the copper acetate solution and adjust the pH value of the solution to 5. Then add 2.5 g of pretreated SSZ-13 molecular sieve (pretreatment is to calcine the SSZ-13 molecular sieve in a muffle furnace at 550°C for 4 h) to the solution and stir the solution to mix evenly.

[0042] (2) The mixed solution was transferred into a Teflon liner, and the hydrothermal autoclave was placed in a rotary oven, and rotated and pressurized at 120 °C for 6 h.

[0043] (3) The obtained solution was filtered, washed with deionized water, and dried in a constant temperature drying oven at 100°C for 8 h. The dried product was placed in a muffle furnace and calcined at 550°C for 4 h at a heating rate of 5°C / min. The obtained catalyst was recorded as Cu-SSZ-13-5. Example 6

[0044] (1) Mix 0.39 g of Cu(CH3COO)2·H20 with 50 mL of deionized water and stir until the copper acetate is completely dissolved to form a uniformly mixed copper acetate solution. Slowly drop 99.5% acetic acid solution into the copper acetate solution and adjust the pH value of the solution to 4. Then add 2.5 g of pretreated SSZ-13 molecular sieve (pretreatment is to calcine the SSZ-13 molecular sieve in a muffle furnace at 550°C for 4 h) to the solution and stir the solution to mix evenly.

[0045] (2) The mixed solution was transferred into a Teflon liner, the hydrothermal autoclave was placed in a rotary oven, and the mixture was rotated and pressurized at 80 °C for 6 h.

[0046] (3) The obtained solution was filtered, washed with deionized water, and dried in a constant temperature drying oven at 100°C for 8 h. The dried product was placed in a muffle furnace and calcined at 550°C for 4 h at a heating rate of 5°C / min. The obtained catalyst was recorded as Cu-SSZ-13-6. Example 7

[0047] (1) Mix 0.39 g of Cu(CH3COO)2·H20 with 50 mL of deionized water and stir until the copper acetate is completely dissolved to form a uniformly mixed copper acetate solution. Slowly drop 99.5% acetic acid solution into the copper acetate solution and adjust the pH value of the solution to 4. Then add 2.5 g of pretreated SSZ-13 molecular sieve (pretreatment is to calcine the SSZ-13 molecular sieve in a muffle furnace at 550°C for 4 h) to the solution and stir the solution to mix evenly.

[0048] (2) The mixed solution was transferred into a Teflon liner, the hydrothermal autoclave was placed in a rotary oven, and the mixture was rotated and pressurized at 160 °C for 6 h.

[0049] (3) The obtained solution was filtered, washed with deionized water, and dried in a constant temperature drying oven at 100°C for 8 h. The dried product was placed in a muffle furnace and calcined at 550°C for 4 h at a heating rate of 5°C / min. The obtained catalyst was recorded as Cu-SSZ-13-7. Example 8

[0050] (1) Mix 0.39 g of Cu(CH3COO)2·H20 with 50 mL of deionized water and stir until the copper acetate is completely dissolved to form a uniformly mixed copper acetate solution. Slowly drop 99.5% acetic acid solution into the copper acetate solution and adjust the pH value of the solution to 4. Then add 2.5 g of pretreated SSZ-13 molecular sieve (pretreatment is to calcine the SSZ-13 molecular sieve in a muffle furnace at 550°C for 4 h) to the solution and stir the solution to mix evenly.

[0051] (2) The mixed solution was transferred into a Teflon liner, the hydrothermal autoclave was placed in a rotary oven, and the mixture was rotated and pressurized at 200 °C for 6 h.

[0052] (3) The obtained solution was filtered, washed with deionized water, and dried in a constant temperature drying oven at 100°C for 8 h. The dried product was placed in a muffle furnace and calcined at 550°C for 4 h at a heating rate of 5°C / min. The obtained catalyst was recorded as Cu-SSZ-13-8.

[0053] The Cu-SSZ-13 molecular sieve catalyst prepared by the present invention is used for NH3-SCR denitration reaction. The catalysts prepared in Examples 1 to 8 are tableted and sieved. The sieved 40-60 mesh catalyst is taken and filled in a reaction tube in an amount of 1 mL. The composition of the reaction mixed gas is: 500 pm NO, 500 ppm NH3, 5% O2, N2 is the balance gas, and the air velocity is 60000 h -1 The test temperature range is 100-550℃. The concentration of each component in the tail gas is measured every 0.5h at 30℃. The results are shown in Figure 3 and Figure 4 .

[0054] The catalytic performance of the Cu-SSZ-13 molecular sieve catalyst prepared in Example 7 was evaluated before and after hydrothermal aging at 600°C for 24 hours in a 10% H2O air atmosphere. Figure 5 ;

[0055] The XRD and SEM images of the Cu-SSZ-13 molecular sieve catalyst provided in Example 7 are shown in Figure 1 and Figure 2 .

[0056] In order to enable those skilled in the art to better understand the present invention, a brief analysis of the figures is now provided:

[0057] Depend on Figure 1 It can be seen that the Cu-SSZ-13 molecular sieve catalyst provided in Example 7 exhibits a typical CHA crystal structure, and no obvious Cu diffraction peak is detected, indicating that Cu exists in the form of ions or is highly dispersed on the zeolite crystals.

[0058] Depend on Figure 2 It can be seen that the morphology of the Cu-SSZ-13 molecular sieve catalyst provided in Example 7 is relatively regular square block crystals.

[0059] Depend on Figure 3 It can be seen that when the pH of the copper acetate solution is adjusted to 4 by acetic acid, the NO conversion rate of Cu-SSZ-13 is the highest.

[0060] Depend on Figure 4 It can be seen that when the mechanical pressurized water heat exchange temperature is 160°C, the NO conversion rate of Cu-SSZ-13 is the highest.

[0061] Depend on Figure 5 It can be seen that after hydrothermal aging treatment, the high temperature performance of Cu-SSZ-13 decreased, but the NO conversion rate was still greater than 90% at 490°C.

[0062] The above embodiments describe the present invention in detail, but the present invention is not limited to the embodiments. Equivalent substitutions or similar improvements that can be made by ordinary technicians in the field based on the technology disclosed in the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing Cu-SSZ-13 molecular sieve catalyst by mechanically pressurized water heat exchange loaded copper, characterized in that: The steps include: (1) Preparation of copper acetate solution: Mix copper acetate monohydrate with deionized water and stir until the copper acetate is completely dissolved to obtain a uniformly dispersed copper acetate solution; (2) pH adjustment: slowly adding acetic acid to the copper acetate solution obtained in step (1) to adjust the pH value of the solution; (3) Mechanical pressurization and hydrothermal exchange: Add SSZ-13 molecular sieve to the solution adjusted in step (2), stir the solution evenly and transfer it into the Teflon lining of the hydrothermal reactor; The hydrothermal reactor is then placed in a rotary oven for rotation and pressurization; The temperature of the rotary oven is 80-200°C, and the rotary pressurization time is 6 hours; the SSZ-13 molecular sieve is a pretreated molecular sieve, and the pretreatment is to calcine the SSZ-13 molecular sieve at 550°C in a muffle furnace for 4 hours; (4) Post-treatment: The pressurized solution in step (3) is filtered, washed with deionized water, dried, and then placed in a muffle furnace and calcined under programmed temperature to obtain a Cu-SSZ-13 molecular sieve catalyst.

2. The method for preparing Cu-SSZ-13 molecular sieve catalyst by mechanical pressurized water heat exchange loading copper according to claim 1, characterized in that: The mass ratio of the copper acetate monohydrate in step (1) to the SSZ-13 molecular sieve in step (3) is 4:

25.

3. The method for preparing Cu-SSZ-13 molecular sieve catalyst by mechanical pressurized water heat exchange loading copper according to claim 1, characterized in that: The mass concentration of acetic acid in step (2) is 99.5%.

4. The method for preparing Cu-SSZ-13 molecular sieve catalyst by mechanical pressurized water heat exchange loading copper according to claim 1, characterized in that: In the step (2), the pH value of the solution is adjusted to 1-5.

5. The method for preparing Cu-SSZ-13 molecular sieve catalyst by mechanical pressurized water heat exchange loading copper according to claim 1, characterized in that: The drying temperature in step (4) is 100° C.; the roasting temperature is 550° C., the heating rate is 5° C. / min, and the roasting time is 4 hours.

6. Application of the Cu-SSZ-13 molecular sieve catalyst prepared by the method according to any one of claims 1 to 5 in NH3-SCR denitration reaction, wherein the reaction evaluation conditions are as follows: taking a sieved 40-60 mesh catalyst, the loading amount in the reaction tube is 1 mL, and the space velocity is 60000 h -1 The composition of the reaction mixture gas is: 500ppmNO, 500ppmNH3, 5%O2, and N2 is the balance gas; the heating rate during evaluation is 5℃ / min, and the concentration of each component in the exhaust gas is measured at a constant temperature of 30℃ for 0.5h.

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