A bifunctional catalyst for simultaneously removing NO x and toluene at low temperature, and its preparation method and application

Abstract

The present invention belongs to the fields of environmental protection and environmental catalysis, and particularly relates to a bifunctional catalyst for simultaneously removing NO x and toluene at low temperature, and a preparation method and application thereof. The preparation method of the above catalyst is to prepare a metal salt solution containing a copper source and a cerium source by ultrasonic-ion dispersion method using anhydrous ethanol as a solvent. Under ultrasonic action, Cu ions and Ce ions are loaded onto microporous SAPO-34 molecular sieve, and a supported CuCe / SAPO-34 catalyst is obtained by calcination in an air atmosphere; in the catalyst, [Cu]+[Ce] / [SAPO-34] is 15% to 25% by mass percentage; among them, the molar ratio of Cu to Ce is 0.20 to 0.30:1. The obtained catalyst reduces the accumulation of intermediate species products, resulting in high CO2 selectivity of the catalyst and reducing the problem of excessive oxidation of NH3, thereby realizing a common temperature window for NO x reduction and toluene oxidation, and the selectivities of CO2 and N2 are nearly 100% at 225°C to 350°C.

Description

Technical Field

[0001] The present invention belongs to the fields of environmental protection and environmental catalysis, and particularly relates to a bifunctional catalyst for simultaneously removing NO x and toluene at low temperature, and a preparation method and application thereof. Background Art

[0002] Nitrogen oxides and toluene are important precursors of photochemical smog and ozone pollution, seriously affecting the environment and human health. It is of great significance to simultaneously remove nitrogen oxides and VOCs. The key to the technology of low-temperature denitrification and coordinated control of VOCs lies in the preparation of the catalyst.

[0003] Some research reports indicate that MnCe series catalysts have good activity for simultaneously catalyzing nitrogen oxides and toluene at low temperature, but they have insufficient stability, and due to the variable valence states of Mn, a large number of by-products will be generated. CeTi-based catalysts have relatively high stability, but the catalytic activity for toluene is relatively weak. In addition, the existing low-temperature denitrification and coordinated control of VOCs catalysts in the prior art also have problems such as complex preparation methods and the generation of a large amount of toxic and harmful wastewater during the preparation process, resulting in difficulties in industrializing the catalyst.

[0004] Based on this, it is imperative to propose a catalyst with an easy-to-operate preparation method, environmentally friendly raw materials, and excellent removal activity and removal stability for both nitrogen oxides and toluene. Summary of the Invention

[0005] To solve the shortcomings and deficiencies of the prior art, the first object of the present invention is to provide a preparation method of a bifunctional catalyst for simultaneously removing NO x and toluene at low temperature. The preparation process involved in this method is easy to operate, and the raw materials are environmentally friendly and easily available. The prepared catalyst has excellent removal activity and removal stability for both nitrogen oxides and toluene.

[0006] The second object of the present invention is to provide a bifunctional catalyst for simultaneously removing NO x and toluene at low temperature prepared by the above method. The provided catalyst has excellent removal activity and stability for removing both nitrogen oxides and toluene.

[0007] The third object of the present invention is to provide the application of the above catalyst in a system for simultaneously removing NO x and VOCs. The activity evaluation test shows that the catalyst provided in this application has excellent removal activity and removal stability for both nitrogen oxides and toluene, and can be applied to a system for simultaneously removing NO x and VOCs.

[0008] To achieve the first object, the technical solution provided by the present invention is: a method for simultaneously removing NO xPreparation method of a bifunctional catalyst for and toluene. By means of ultrasonic-ion dispersion method, an anhydrous ethanol is used as a solvent to prepare a metal salt solution containing a copper source and a cerium source. The mixed system of the metal salt solution and molecular sieve SAPO-34 is ultrasonically treated, and Cu ions and Ce ions are loaded onto the microporous SAPO-34 molecular sieve, and a supported CuCe / SAPO-34 catalyst is obtained by calcination in an air atmosphere.

[0009] In the catalyst, [Cu]+[Ce] / [SAPO-34] is 15% - 25% by mass percentage; among them, the molar ratio of Cu to Ce is 0.20 - 0.30:1.

[0010] It should be noted that in [Cu]+[Ce] / [SAPO-34], [Cu] and [Ce] are calculated based on the mass of Cu and Ce elements.

[0011] According to some preferred embodiments, its preparation method includes the following steps:

[0012] (1) Preparation of the metal salt solution: Dissolve a certain proportion of copper source and cerium source into anhydrous ethanol;

[0013] (2) Dispersion treatment: Add SAPO-34 molecular sieve powder to the metal salt solution obtained in step (1), and successively stir, ultrasonically treat, and stir the mixed system of the metal salt solution and molecular sieve SAPO-34;

[0014] (3) Constant temperature evaporation: Perform constant temperature evaporation on the dispersion obtained in step (2) to remove the solvent in the dispersion;

[0015] (4) Calcination: Dry the sample obtained in step (3), and calcine and activate it in an air atmosphere to obtain a CuCe / SAPO-34 catalyst.

[0016] According to some preferred embodiments, the molar ratio of Cu to Ce in the catalyst is 0.24 - 0.26:1;

[0017] Preferably, the molar ratio of Cu to Ce in the catalyst is 0.25:1.

[0018] According to some preferred embodiments, [Cu]+[Ce] / [SAPO-34] in the catalyst is 19% - 21% by mass percentage;

[0019] Preferably, [Cu]+[Ce] / [SAPO-34] in the catalyst is 20% by mass percentage.

[0020] According to some preferred embodiments, in step (1), the metal salt is prepared in absolute ethanol at a concentration of 0.020 g / ml to 0.030 g / ml; preferably, in step (1), the metal salt is prepared in absolute ethanol at a concentration of 0.025 g / ml;

[0021] and / or, the copper source is copper acetate and the cerium source is cerium nitrate.

[0022] According to some preferred embodiments, in step (2), the specific method of the dispersion treatment is to add the SAPO-34 molecular sieve powder into the metal salt solution obtained in step (1), stir at room temperature for 0.5 h to 1.5 h, perform ultrasonic treatment at an ultrasonic power of 150 W to 300 W for 0.2 h to 1 h, and then stir for 0.5 h to 1.5 h after completion. If necessary, the above ultrasonic-stirring steps can be repeated.

[0023] According to some preferred embodiments, in step (4), the drying is carried out at a temperature of 80 °C to 120 °C for 2 h to 8 h;

[0024] Preferably, the drying is carried out at 100 °C for 6 h.

[0025] According to some preferred embodiments, the method of calcination in step (4) is as follows: under aerobic conditions, at a heating rate of 3 °C / min to 5 °C / min, heat up to 300 °C to 400 °C and keep it for calcination for 2 h to 5 h;

[0026] Preferably, the method of calcination in step (4) is as follows: under aerobic conditions, at a heating rate of 5 °C / min, heat up to 350 °C and keep it for calcination for 3 h.

[0027] To achieve the second object, the technical solution provided by the present invention is: to provide a dual-functional catalyst for simultaneously removing NO x and toluene prepared by the above preparation method. The prepared supported CuCe / SAPO-34 catalyst has a conversion rate of NO x and toluene greater than 90% in the range of 250 °C to 350 °C at a reaction temperature of 200 °C to 325 °C, a conversion rate of toluene greater than 70%, and the CO2 and N2 selectivities of both are nearly 100%.

[0028] To achieve the third object, the technical solution provided by the present invention is: to provide the application of the above dual-functional catalyst in a system for simultaneously removing NO x and VOCs;

[0029] Preferably, the system for simultaneously removing NO x and VOCs is a fixed-bed reactor; and / or, the removal conditions are a gas flow rate of 100 mL∙min -1~300 mL∙min -1 The reaction space velocity is 70,000 mL∙g -1 ∙h -1 ~80,000 mL∙g -1 ∙h -1 。

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. The present invention uses the ultrasonic-ion dispersion method to prepare CuCe / SAPO-34. By optimizing the preparation process and changing the CuCe molar ratio under a certain loading amount, the interaction strength between Cu and Ce is changed, thereby regulating the redox ability of the catalyst. The obtained supported CuCe / SAPO-34 catalyst has the comprehensive performance of simultaneously removing NO x and toluene at low temperature.

[0032] 2. The characteristics of the CuCe / SAPO-34 catalyst are as follows: 1) There is a strong interaction between Cu and Ce in the catalyst, which has excellent activities for simultaneously removing NO x and toluene and relatively good anti-deactivation characteristics. 2) The CuCe / SAPO-34 catalyst after the CuCe ratio is regulated appropriately slows down the inhibitory effect of toluene and intermediate species on the adsorption of reactants on the catalyst surface, and at the same time reduces the over-oxidation of NH3, and the adverse secondary intermediate by-products formed by toluene and its by-products on the removal reaction, effectively improving the selectivity of CO2, making it have good anti-deactivation performance and high selectivity.

[0033] 3. The preparation method of the CuCe / SAPO-34 catalyst provided in the present application involves simple and easy preparation steps, environmentally friendly raw materials, and low cost and easy availability. The prepared catalyst has excellent removal activities and stability for removing nitrogen oxides and toluene, and has very good industrial application and popularization value. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is the activity evaluation test chart of NO x and toluene conversion rates in Example 1 and Comparative Examples 1-4 of the present invention; the left figure is the comparison chart of different preparation methods of Cu 0.2 Ce 0.8 / SAPO-34 under the same ratio condition; the right figure is the comparison chart of different molar ratios under the preferred preparation method;

[0035] Among them, Cu 0.1 Ce 0.9 / SAPO-34, Cu 0.2 Ce 0.8 / SAPO-34, Cu0.4 Ce 0.6 Ce / SAPO-34 represents the catalysts of Comparative Example 3, Example 1, and Comparative Example 4 in sequence;

[0036] Figure 2 It is the CO2 and N2 selectivity and the common temperature activity window diagram between 225 - 350 °C of Example 1 and Comparative Example 4 of the present invention;

[0037] Figure 3 It is the XRD pattern of the catalysts in Example 1 and Comparative Examples 3 - 4 of the present invention;

[0038] Among them, Cu 0.1 Ce 0.9 Ce / SAPO-34, Cu 0.2 Ce 0.8 Ce / SAPO-34, Cu 0.4 Ce 0.6 Ce / SAPO-34 represents the catalysts of Comparative Example 3, Example 1, and Comparative Example 4 in sequence;

[0039] Figure 4 It is the nitrogen adsorption - desorption isotherm diagram of the catalysts in Example 1 and Comparative Examples 3 - 4 of the present invention;

[0040] Among them, Cu 0.1 Ce 0.9 Ce / SAPO-34, Cu 0.2 Ce 0.8 Ce / SAPO-34, Cu 0.4 Ce 0.6 Ce / SAPO-34 represents the catalysts of Comparative Example 3, Example 1, and Comparative Example 4 in sequence;

[0041] Figure 5 It is the pore size distribution diagram of Example 1 and Comparative Examples 3 - 4 of the present invention;

[0042] Among them, Cu 0.1 Ce 0.9 Ce / SAPO-34, Cu 0.2 Ce 0.8 Ce / SAPO-34, Cu 0.4 Ce 0.6 Ce / SAPO-34 represents the catalysts of Comparative Example 3, Example 1, and Comparative Example 4 in sequence;

[0043] The present invention will be further described below in conjunction with the accompanying drawings and embodiments. Specific Embodiments

[0044] The present invention provides a method for simultaneously removing NO at low temperature xBifunctional catalyst with toluene and its preparation method and application. The following further describes the present invention in conjunction with specific embodiments. However, the embodiments of the present invention are not limited thereto. If there are process parameters not specifically noted, conventional techniques can be referred to.

[0045] Example 1

[0046] Cu 0.2 Ce 0.8 / SAPO-34 Preparation: Using the ultrasonic-ion dispersion method, ethanol as the solvent to synthesize Cu x Ce 1-x / SAPO-34 catalyst. During the preparation process, first dissolve 0.128 g of Cu(CH3COO)2·H2O and 1.1133 g of Ce(NO3)3·6H2O completely in 50 ml of absolute ethanol, denoted as solution A. Then take 2 g of the SAPO-34 support (purchased from the Catalyst Factory of Nankai University, silicon-aluminum ratio = 0.5, the same below), where [Cu]+[Ce] / [SAPO-34]=20%, n (Cu) :n (Ce) =2:8 and add it to solution A. Stir magnetically for 1 h, under ultrasonic conditions for 40 min, ultrasonic input power 200 W, output total power 600 W. Take out the solution and stir magnetically for 1 h again, and repeat the operation once. Then place it in a water bath at 80 °C to stir dry. The obtained solid is placed in an oven at 100 °C for 6 h and calcined at 350 °C under aerobic conditions for 3 h, with a heating rate of 5 °C / min.

[0047] Comparative Example 1

[0048] Cu 0.2 Ce 0.8 / SAPO-34 (ethanol - non-ultrasonic) Preparation: Using the ethanol dispersion method, ethanol as the solvent to synthesize Cu x Ce 1-x / SAPO-34 catalyst. During the preparation process, first dissolve 0.128 g of Cu(CH3COO)2·H2O and 1.1133 g of Ce(NO3)3·6H2O completely in 50 ml of absolute ethanol, denoted as solution A. Then take 2 g of the SAPO-34 support (SAPO-34 purchased from the Catalyst Factory of Nankai University), where [Cu]+[Ce] / [SAPO-34]=20%, n (Cu) :n (Ce) =2:8 and add it to solution A. Stir directly magnetically for 2 h, then place it in a water bath at 80 °C to stir dry. The obtained solid is placed in an oven at 100 °C for 6 h and calcined at 350 °C under aerobic conditions for 3 h, with a heating rate of 5 °C / min.

[0049] Comparative Example 2

[0050] Cu 0.2 Ce 0.8 / SAPO-34 (water - ultrasound) preparation: Using the ultrasound - ion dispersion method, water was used as the solvent to synthesize the Cu x Ce 1-x / SAPO-34 catalyst. During the preparation process, first, 0.128 g of Cu(CH3COO)2·H2O and 1.1133 g of Ce(NO3)3·6H2O were completely dissolved in 50 ml of water, denoted as solution A. Then, 2 g of the SAPO-34 support (SAPO-34 was purchased from the Catalyst Factory of Nankai University), where [Cu]+[Ce] / [SAPO-34]=20%, n (Cu) :n (Ce) =2:8 was added to solution A, magnetically stirred for 1 h, and ultrasonically treated for 40 min under ultrasonic conditions with an ultrasonic input power of 200 W and an output total power of 600 W. The taken - out solution was magnetically stirred for 1 h again, and the operation was repeated once. Then, it was placed in a water bath at 80 °C to stir - dry, and the obtained solid was placed in an oven at 100 °C for 6 h and calcined at 350 °C under aerobic conditions for 3 h with a heating rate of 5 °C / min.

[0051] Comparative Example 3

[0052] Cu 0.1 Ce 0.9 / SAPO-34 preparation: Using the ultrasound - ion dispersion method, ethanol was used as the solvent to synthesize the Cu x Ce 1-x / SAPO-34 catalyst. During the preparation process, first, 0.0603 g of Cu(CH3COO)2·H2O and 1.18 g of Ce(NO3)3·6H2O were completely dissolved in 50 ml of absolute ethanol, denoted as solution A. Then, 2 g of the SAPO-34 support (SAPO-34 was purchased from the Catalyst Factory of Nankai University), where [Cu]+[Ce] / [SAPO-34]=20%, n (Cu) :n (Ce) =1:9 was added to solution A, magnetically stirred for 1 h, and ultrasonically treated for 40 min under ultrasonic conditions with an ultrasonic input power of 200 W and an output total power of 600 W. The taken - out solution was magnetically stirred for 1 h again, and the operation was repeated once. Then, it was placed in a water bath at 80 °C to stir - dry, and the obtained solid was placed in an oven at 100 °C for 6 h and calcined at 350 °C under aerobic conditions for 3 h with a heating rate of 5 °C / min.

[0053] Comparative Example 4

[0054] Cu 0.4 Ce 0.6 / SAPO-34 preparation: Using the ultrasound - ion dispersion method, ethanol was used as the solvent to synthesize the Cu x Ce1-x / SAPO-34 catalyst. During the preparation process, first, 0.29 g of Cu(CH3COO)2·H2O and 0.95 g of Ce(NO3)3·6H2O were completely dissolved in 50 ml of absolute ethanol, denoted as solution A. Then, 2 g of SAPO-34 support (SAPO-34 was purchased from the Catalyst Factory of Nankai University) was taken, where [Cu]+[Ce] / [SAPO-34]=20%, and n (Cu) :n (Ce) =1:9 was added to solution A, and it was magnetically stirred for 1 h and then ultrasonically treated for 40 min under ultrasonic conditions with an ultrasonic input power of 200 W and an output total power of 600 W. The taken-out solution was magnetically stirred for another 1 h, and the operation was repeated once. Then, it was placed in a water bath at 80 °C and stirred dry. The obtained solid was placed in an oven at 100 °C for 6 h and calcined at 350 °C under aerobic conditions for 3 h with a heating rate of 5 °C / min.

[0055] Test Example

[0056] (1) Activity evaluation test: Simultaneous removal of NO x and the activity evaluation test of the toluene catalyst were carried out in a fixed-bed reactor with an inner diameter of 10 mm. After improving the denitration device of this experimental apparatus, the toluene atmosphere was introduced into the denitration system by the liquid-phase stripping method, and the addition amount of toluene was controlled by adjusting the flow rate of stripping N2 and the temperature of the constant-temperature bath. The solid catalyst bed was 0.16 g (40 - 60 mesh). In the experiment, the simulated atmosphere composition was 500 ppm NH3, 500 ppm NO, 5 vol.% O2, 100 ppm C7H8, with N2 as the balance gas, and the gas flow rate was 200 mL∙min -1 −1, and the reaction space velocity was 75,000 mL∙g -1 −1∙h -1 −1. Before and after the reaction, NO, N2O, and NO2 in the gas were analyzed by a GASMET DX4000 flue gas analyzer, and C7H8 and CO2 were detected by a hydrogen flame ionization detector (FID Ⅱ) and a thermal conductivity detector (TCD) in a gas chromatograph (GC9790Ⅱ), respectively. The results are shown in Table 1-2 below, and Figure 1 as follows:

[0057] Table 1 Denitration activity evaluation results of examples and comparative examples

[0058]

[0059] Table 2 Toluene removal activity evaluation results of examples and comparative examples

[0060]

[0061] Combined with Tables 1 and 2, Figure 1It can be seen that compared with the other four groups of catalysts, the catalyst in Example 1 has both good low-temperature denitration and toluene removal activities, and has good stability at medium and high temperatures. This shows that during the preparation process of the CuCe / SAPO-34 catalyst, the ultrasonic process and the choice of solvent have a significant impact on the activity of the catalyst; the regulation of the CuCe ratio weakens the mutual influence between denitration and toluene removal, thus having better simultaneous removal activity.

[0062] (2)NO x Anti-deactivation performance test of NO conversion rate in the presence of toluene atmosphere: To further study the influence of toluene in the removal reaction, a toluene on-off experiment was carried out at 250 °C. In the experiment, the simulated atmosphere composition was 500 ppm NH3, 500 ppm NO, 5 vol.% O2, 100 ppm C7H8, with N2 as the balance gas, and the total gas flow rate was 200 mL∙min -1 , and the reaction space velocity was 75,000 mL∙g -1 ∙h -1 . At 275 °C, first, the reaction stability of the single denitration atmosphere was tested, then the toluene atmosphere was added and the experimental data were continuously recorded, and finally the toluene was cut off to observe the reaction. The reaction stability of each stage lasted for several hours to observe the denitration stability of the catalyst in the presence of nitrogen oxides and toluene simultaneously. The reaction data at each time were continuously recorded. The data in the stage of nitrogen oxides and toluene simultaneously are as follows. The specific data are shown in Table 3. Before and after the reaction, NO, N2O, and NO2 in the gas were detected by a NO-NO2-NO x flue gas analyzer.

[0063] Table 3 Anti-deactivation performance test

[0064]

[0065] As can be seen from Table 3, during the single SCR reaction, both the Cu 0.2 Ce 0.8 / S-34 and Cu 0.4 Ce 0.6 / S-34 catalysts had a 100% NO x conversion rate. However, when the toluene atmosphere was added, the conversion rate of the Cu 0.4 Ce 0.6 / S-34 catalyst decreased rapidly under the influence of the toluene atmosphere. And after the toluene was cut off, although the NO x conversion rate recovered in a short time, but then there was a more obvious downward trend. Although its toluene T 90 was lower, the CO2 selectivity for catalytic oxidation of toluene was low and the over-oxidation of NH3 significantly limited its application. For the catalyst after regulation, Cu 0.2 Ce0.8 While taking into account the high catalytic oxidation activity of toluene, / S-34 also has relatively high denitration stability.

[0066] Figure 2 Shows Cu 0.2 Ce 0.8 / S-34 and Cu 0.4 Ce 0.6 The selectivities of N2 and CO2 of the Cu 0.4 Ce 0.6 / S-34 catalyst in the temperature range of 225 - 350 °C. Although the N2 selectivities of both are close to 100%, when the temperature > 275 °C, the conversion rate of NO of Cu x rapidly decreases, indicating that the selectivity of Cu 0.4 Ce 0.6 / S-34 is significantly worse than that of Cu 0.2 Ce 0.8 / S-34. Therefore, by regulating the ratio of Cu and Ce in the catalyst, the preferred Cu 0.2 Ce 0.8 / S-34 has the optimal selectivity, stability and wide reaction temperature window.

[0067] (3) The phase structures of the catalysts obtained in Example 1 and Comparative Examples 3 - 4 were determined by XRD technology. By comparing with the JCPDS cards, the crystal compositions and crystallinities of the catalyst phases and surface elements were discriminated. The XRD technology test was carried out using a D8 Advance (Bruker, Germany) X-ray diffractometer. The test conditions for diffraction were CuKβ rays, the operating voltage was 40 KV, the operating current was 30 mA, and the scanning range 2θ was 5 - 90°. The XRD patterns of the catalysts are shown in Figure 3 .

[0068] As can be seen from Figure 3 , the catalysts of Example 1 and Comparative Examples 3 - 4 have typical CHA structure characteristic peaks. The peaks at 2θ = 9 - 32° are attributed to the SAPO-34 molecular sieve (JCPDS 47 - 0617), indicating that the loading of CuCe does not destroy the original structure of the molecular sieve. CeO2 representing the cubic fluorite structure (JCPDS-34 04 - 0593) was observed at 2θ = 28.54°, 33.07°, 47.48° and 56.32°. While in Cu 0.1 Ce 0.9 / S-34, Cu 0.2 Ce 0.8 / S-34, Cu 0.4 Ce 0.6No peaks of CuO were observed on the / S-34 sample, indicating that CuO exists in a highly dispersed or amorphous state on the support. It is worth noting that Cu 0.2 Ce 0.8 The diffraction peaks of SAPO-34 on the / S-34 sample showed the maximum intensity, which was particularly obvious at 2θ = 9.49°. According to the research, the change in the diffraction peak intensity was due to the covering or destruction of the crystal structure. Thus, it can be inferred that Cu 0.2 Ce 0.8 In the / S-34 sample, the CuCe doping in an appropriate proportion formed smaller grain sizes and was more dispersed on the support surface compared to other samples. Therefore, the influence on the SAPO-34 molecular sieve was relatively small.

[0069] (4) The BET and pore structures of the catalysts obtained in Example 1 and Comparative Examples 3-4 were measured by a Micromeritics ASAP 2020 analyzer in the United States at -196 °C for N2 physical adsorption and desorption. Before the test, the catalyst was pretreated at 250 °C for 1 h to remove surface moisture and impurities. The BET specific surface area and pore volume of the Cu 0.1 Ce 0.9 / S-34, Cu 0.2 Ce 0.8 / S-34, and Cu 0.4 Ce 0.6 / S-34 catalysts were calculated. The data results are shown in Table 4 below. The N2 adsorption-desorption isotherms and pore size distribution results of the three catalysts are as Figure 4 、 Figure 5 。

[0070] Table 4 Textural properties of CuCe catalysts with different CuCe ratios

[0071]

[0072] Figure 4 According to the classification of the International Union of Pure and Applied Chemistry (IUPAC), the isotherms of the CuCe / S-34 catalysts all exhibited type I mesoporous isotherms with H4-type hysteresis loops, indicating that the samples were mainly microporous. The specific results are shown in Table 4.

[0073] Figure 5 Figure 41 shows the pore size distribution diagrams of the three catalysts. It can be seen that the differences among the three catalysts within the pore size range of 0 - 2.0 nm are not significant, indicating that the pore distribution of the catalysts is uniform, which is conducive to the adsorption of reactant molecules and mainly consists of micropores. When the pore size is >2.0 nm, Cu 0.2 Ce 0.8The / S-34 catalyst has more mesopores and macropores than the catalyst in the control group. It is speculated that a certain proportion of mesopores is beneficial to improving the oxidation of toluene, thereby enhancing the catalytic activity. At the same time, the mesoporous structure increases the diffusion limitation of reactants in the pores, increases the pore adsorption capacity, and alleviates the deposition of reactants and reaction intermediates on the catalyst surface.

[0074] The above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A preparation method of a bifunctional catalyst for simultaneously removing NO x and toluene at low temperature, characterized in that By the ultrasonic-ion dispersion method, an anhydrous ethanol solvent was used to prepare a metal salt solution containing a copper source and a cerium source. The mixed system of the metal salt solution and the molecular sieve SAPO-34 was ultrasonically treated to load Cu ions and Ce ions onto the microporous SAPO-34 molecular sieve, and a supported CuCe / SAPO-34 catalyst was obtained by calcination in an air atmosphere. In the catalyst, [Cu]+[Ce] / [SAPO-34] is 19% - 21% by mass percentage; among them, the molar ratio of Cu to Ce is 0.24 - 0.26:

1. Its preparation method includes the following steps: (1) Preparation of the metal salt solution: Dissolve a certain proportion of the copper source and the cerium source in anhydrous ethanol. (2) Dispersion treatment: Add the SAPO-34 molecular sieve powder to the metal salt solution obtained in step (1), and successively stir, ultrasonically treat, and stir the mixed system of the metal salt solution and the molecular sieve SAPO-34. (3) Constant temperature evaporation: Carry out constant temperature evaporation on the dispersion obtained in step (2) to remove the solvent in the dispersion. (4) Calcination: Dry the sample obtained in step (3) and calcine and activate it in an air atmosphere to obtain the CuCe / SAPO-34 catalyst. The copper source is copper acetate, and the cerium source is cerium nitrate. In step (2), the specific method of the dispersion treatment is to add the SAPO-34 molecular sieve powder to the metal salt solution obtained in step (1), stir at room temperature for 0.5 h - 1.5 h, ultrasonically treat at an ultrasonic power of 150 W - 300 W for 0.2 h - 1 h, and then stir for 0.5 h - 1.5 h after completion. The calcination method in step (4) is to heat up to 350 °C at a heating rate of 5 °C / min under aerobic conditions and keep it calcined for 3 h.

2. Preparation method of bifunctional catalyst for simultaneous removal of NO x and toluene at low temperature, characterized in that The molar ratio of Cu to Ce in the catalyst is 0.25:

1.

3. Preparation method of bifunctional catalyst for simultaneously removing NO x and toluene at low temperature, characterized in that In the catalyst, [Cu]+[Ce] / [SAPO-34] is 20% by mass percentage.

4. Preparation method of bifunctional catalyst for simultaneous removal of NO x and toluene at low temperature, characterized in that In step (1), the concentration of the metal salt prepared in anhydrous ethanol is 0.020 g / ml - 0.030 g / ml.

5. Preparation method of bifunctional catalyst for simultaneous removal of NO x and toluene at low temperature, characterized in that In step (1), the concentration of the metal salt prepared in anhydrous ethanol is 0.025 g / ml.

6. Preparation method of bifunctional catalyst for simultaneous removal of NO x and toluene at low temperature, characterized in that In step (4), the drying is carried out at a temperature of 80 °C - 120 °C for 2 h - 8 h.

7. Preparation method of bifunctional catalyst for simultaneous removal of NO x and toluene at low temperature, characterized in that In step (4), the drying is carried out at 100 °C for 6 h.

8. A bifunctional catalyst for simultaneously removing NO and toluene at low temperature, prepared by the preparation method according to any one of claims 1 to 7. x ​ 9. Use of the bifunctional catalyst according to claim 8 in a system for simultaneously removing NO x and VOCs, wherein the system for simultaneously removing NO x and VOCs is a fixed-bed reactor; and / or, the removal conditions are that the gas flow rate is 100 mL∙min -1 to 300 mL∙min -1 , the reaction space velocity is 70,000 mL∙g -1 ∙h -1 to 80,000 mL∙g -1 ∙h -1 .

Images