Preparation method and application of SAPO-34 composite material with Cu-Cu active sites

Abstract

The invention discloses a preparation method and application of an SAPO-34 composite material with Cu-Cu active sites, and relates to a preparation method and application of a catalyst for selective catalytic reduction of NOx. The technical problems that active sites of an existing denitration molecular sieve catalyst Cu-SAPO-34 are prone to agglomeration, low-temperature activity is poor, hydrothermal stability is poor, and water resistance and sulfur resistance are poor are solved. The preparation method comprises the following steps: adding an oxalic acid treating agent into a copper source aqueous solution for pretreatment, then adding into a mixed solution of pseudo-boehmite, H3PO4, white carbon black, triethylamine and tetraethylenepentamine, stirring to form sol-gel, then transferring into a hydrothermal reaction kettle for hydrothermal reaction, and then calcining to obtain the SAPO-34 composite material with Cu-Cu active sites. When the catalyst is used for NH3-SCR denitration, 90% conversion can be achieved at the temperature of 130-430 DEG C, and the catalyst has good water resistance and sulfur resistance and can be used in the field of NH3-SCR denitration.

Description

Technical Field

[0001] The present invention relates to a preparation method of a catalyst for selective catalytic reduction of NOx, and belongs to the field of selective catalytic reduction of NOx. Background Art

[0002] With the development of human society and the improvement of living standards, environmental problems have attracted increasing attention. Currently, the main environmental problems can be divided into two categories: one is the primary environmental problems caused by natural evolution and natural disasters; the other is the environmental problems caused by human activities, mainly including environmental pollution and ecological damage. Among the pollutants in vehicle exhaust, nitrogen oxides (NOx) are one of the main pollutants, and the nitrogen oxides emissions from diesel vehicle exhaust are particularly prominent.

[0003] The catalytic selective reduction of ammonia (NH3-SCR) technology is considered to be an effective way to eliminate nitrogen oxides pollution in vehicle exhaust. The existing denitration catalysts can be mainly divided into three categories: noble metal-based catalysts, metal oxide catalysts, and molecular sieve catalysts. When the noble metal-based catalyst is used in incomplete combustion of fuel, CO may cause the inactivation of active components, and the cost is relatively high, which limits its application. Metal oxide catalysts (such as V2O5-WO3 / TiO2) have a relatively high NOx conversion temperature, but the 100% NO conversion window is limited, and V species have biological toxicity, which is not suitable for vehicle exhaust treatment. Molecular sieve catalysts, such as Cu-SAPO-34 and Cu-SSZ-13, have problems such as agglomeration of active Cu, poor low-temperature activity, insufficient water resistance, and poor hydrothermal stability. Summary of the Invention

[0004] The present invention aims to solve the technical problems of the existing denitration molecular sieve catalyst Cu-SAPO-34, such as easy agglomeration of active sites, poor low-temperature activity, poor hydrothermal stability, and poor water and sulfur resistance, and provides a preparation method and application of a SAPO-34 composite material with Cu-Cu active sites.

[0005] The preparation method of the SAPO-34 composite material with Cu-Cu active sites of the present invention is carried out according to the following steps:

[0006] 1. Weigh pseudoboehmite, H3PO4, silica white, triethylamine (TEA), and tetraethylenepentamine (TEPA);

[0007] Wherein the mass ratio of pseudoboehmite to silica white is (1.1 - 2.7):1;

[0008] The volume ratio of H3PO4 to the mass of silica white is (1.3 - 2) mL:1 g;

[0009] First, dissolve pseudo-boehmite in deionized water and stir for 0 - 4 h on a magnetic stirrer at room temperature; then add H3PO4 and continue to stir for 0 - 4 h; next, add silica white and continue to stir for 2 - 2.5 h; then add triethylamine (TEA) and continue to stir for 0 - 4 h; then add tetraethylenepentamine (TEPA) and stir for 2 - 2.5 h to obtain solution A;

[0010] Second, pretreat the copper source: Add the copper source and the acid treatment agent to deionized water and stir until completely dissolved to obtain solution B; where the copper source is copper glycinate (C4H8CuN2O4) or copper acetylacetonate (C 10 H 14 CuO4); the acid treatment agent is oxalic acid (H2C2O4);

[0011] Third, mix solution A and B and stir for 10 - 20 hours to obtain a sol-gel;

[0012] Fourth, after ultrasonic treatment of the sol-gel obtained in the third step, transfer it to a hydrothermal reaction kettle, and then place the hydrothermal reaction kettle in an oven at a temperature of 180 - 200 °C and keep it for 24 - 48 h for hydrothermal reaction. Wash the product with deionized water and ethanol in sequence, centrifuge and dry it to obtain a precursor;

[0013] Fifth, after grinding the precursor into powder, place it in a porcelain boat, put it in a muffle furnace, heat it to 550 - 580 °C and calcine it for 5 - 6 h to remove the template agent therein, and obtain a Cu-Cu active site-containing SAPO-34 composite material, denoted as Cu-Cu@SAPO-34.

[0014] Furthermore, the mass percentage of Al2O3 in the pseudo-boehmite described in the first step is ≥70%.

[0015] Furthermore, the mass percentage of SiO2 in the silica white described in the first step is ≥85%.

[0016] Furthermore, the mass ratio of the silica white described in the first step to the volume of triethylamine (TEA) is 1 g:(3.3 - 6.7) mL.

[0017] Furthermore, the mass ratio of the silica white described in the first step to the volume of tetraethylenepentamine (TEPA) is 1 g:(1.3 - 2) mL.

[0018] Furthermore, the copper source in the second step is copper glycinate, and the acid treatment agent is oxalic acid; the molar ratio of copper glycinate to oxalic acid is (0.3 - 2.3):1.

[0019] Furthermore, the copper source in the second step is copper glycinate, and the acid treatment agent is oxalic acid; the molar ratio of copper glycinate to oxalic acid is (1.8 - 2.2):1.

[0020] Furthermore, the copper source described in step two is copper acetylacetonate, and the acid treatment agent is oxalic acid; the molar ratio of copper acetylacetonate to oxalic acid is (0.3 - 2.3):1.

[0021] Furthermore, the copper source described in step two is copper acetylacetonate, and the acid treatment agent is oxalic acid; the molar ratio of copper acetylacetonate to oxalic acid is (1.8 - 2.2):1.

[0022] Furthermore, the mass ratio of the silica white described in step one to the copper acetylacetonate described in step two is 1:(0.6 - 1.4).

[0023] Furthermore, the mass ratio of the silica white described in step one to the copper glycinate described in step two is 1:(0.5 - 1).

[0024] The application of the SAPO-34 composite material with Cu-Cu active sites prepared by the above method is to use the SAPO-34 composite material with Cu-Cu active sites as a catalyst in the catalytic selective reduction reaction of ammonia.

[0025] The advantages of the present invention are as follows:

[0026] (1) The present invention synthesizes and prepares Cu-Cu@SAPO-34 by a one-step hydrothermal method. This method is simple to operate, time-consuming short, low-cost, high-yield, and can be mass-produced.

[0027] (2) The present invention uses copper complexes such as copper acetylacetonate and copper glycinate as the copper source, and then treats them with oxalic acid. The special structure of oxalic acid enables the formation of Cu-Cu active sites. The organic structure in the copper organic complex is conducive to coordinating with the silicon hydroxyl groups and aluminum hydroxyl groups in the molecular sieve to form Cu-Cu@SAPO-34 with atomically dispersed Cu-Cu active sites. The formed Cu-Cu active sites are neither easily agglomerated nor form sufficient active sites during the reaction, thus improving the low-temperature activity and stability of the reaction. At the same time, the Cu-Cu active sites are anchored in the six-membered ring and eight-membered ring of the molecular sieve, making the Cu more firmly located in the molecular sieve, which is conducive to improving the hydrothermal stability.

[0028] (3) In the present invention, tetraethylenepentamine (TEPA) is used as a dispersant and pore-forming agent, rather than a common template agent. By adding TEPA, the dispersion of copper is promoted; at the same time, a hierarchical pore structure is formed, which is conducive to mass transfer and elimination of internal diffusion limitations, thereby improving the reaction activity.

[0029] (4) The Cu-SAPO-34 catalyst prepared by the present invention exhibits extremely excellent low-temperature SCR activity and N2 selectivity in the NH3-SCR reaction, and can still maintain good reaction activity even when a large amount of water vapor and sulfur dioxide are introduced. It can still maintain excellent reaction activity after high-temperature hydrothermal treatment at 650 °C and low-temperature hydrothermal treatment at 80 °C.

[0030] The SAPO-34 composite material with Cu-Cu active sites of the present invention can be used in the field of NH3-SCR denitration. Description of the Drawings

[0031] Figure 1 XRD image of Cu-Cu@SAPO-34 obtained in Example 1;

[0032] Figure 2 NOx conversion rate images of Cu-Cu@SAPO-34 obtained in Example 1 at different temperatures;

[0033] Figure 3 XRD image of Cu-SAPO-34 obtained in Comparative Example 1;

[0034] Figure 4 NOx conversion rate images of Cu-SAPO-34 obtained in Comparative Example 1 at different temperatures;

[0035] Figure 5 N2-adsorption and desorption image of Cu-Cu@SAPO-34 obtained in Example 1;

[0036] Figure 6 Synchrotron radiation image of Cu-Cu@SAPO-34 obtained in Example 1;

[0037] Figure 7 NOx conversion rate images of Cu-Cu@SAPO-34 obtained in Example 1 after hydrothermal treatment;

[0038] Figure 8 Water and sulfur resistance image of Cu-Cu@SAPO-34 obtained in Example 1.

[0039] Figure 9 XRD image of Cu-Cu@SAPO-34 obtained in Example 2;

[0040] Figure 10 NOx conversion rate images of Cu-Cu@SAPO-34 obtained in Example 2 at different temperatures;

[0041] Figure 11 XRD image of Cu-SAPO-34 obtained in Comparative Example 2;

[0042] Figure 12 The NOx conversion rate image of Cu-SAPO-34 obtained in Comparative Example 2 at different temperatures;

[0043] Figure 13 The XRD image of Cu-Cu@SAPO-34 obtained in Example 3;

[0044] Figure 14 The NOx conversion rate image of Cu-Cu@SAPO-34 obtained in Example 3 at different temperatures;

[0045] Figure 15 The XRD image of Cu-Cu@SAPO-34 obtained in Example 4;

[0046] Figure 16 The NOx conversion rate image of Cu-Cu@SAPO-34 obtained in Example 4 at different temperatures;

[0047] Figure 17 The XRD image of Cu-Cu@SAPO-34 obtained in Example 5;

[0048] Figure 18 The NOx conversion rate image of Cu-Cu@SAPO-34 obtained in Example 5 at different temperatures. Detailed implementation manners

[0049] The beneficial effects of the present invention are verified by the following examples.

[0050] Example 1: The preparation method of the SAPO-34 composite material with Cu-Cu active sites in this example is carried out according to the following steps:

[0051] I. First, dissolve 3.0 g of pseudoboehmite with a mass percentage of Al2O3 of 75% in 30 mL of deionized water, and stir at room temperature on a magnetic stirrer for 1 h; then add 2.5 mL of H3PO4 and continue stirring for 1 h; then add 1.5 g of silica white with a mass percentage of SiO2 of 88% and continue stirring for 2 h; then add 8 mL of triethylamine (TEA) and continue stirring for 1 h; finally, add 3 mL of tetraethylenepentamine (TEPA) and stir for 2 h to obtain solution A;

[0052] II. Dissolve 1.5 g of copper glycinate (C4H8CuN2O4) and 0.45 g of oxalic acid (H2C2O4) in 30 ml of water to make the molar ratio of copper to oxalic acid 2:1, and stir until completely dissolved to obtain solution B;

[0053] III. Mix solution A and solution B and stir for 12 hours to obtain a sol-gel;

[0054] IV. After subjecting the sol-gel obtained in Step III to ultrasonic treatment, transfer it to a hydrothermal reaction kettle, and then place the hydrothermal reaction kettle in an oven at a temperature of 200 °C for 24 h to carry out a hydrothermal reaction. Wash the product successively with deionized water and ethanol three times each, centrifuge it, and place it in an oven at a temperature of 80 °C to dry for 8 h to obtain a precursor;

[0055] III. After grinding the precursor into a powder, place it in a porcelain boat and put it in a high-temperature furnace. Heat it up to 550 °C and calcine it for 5 h to remove the template agents triethylamine and tetraethylenepentamine therein, obtaining a Cu-Cu active site-containing SAPO-34 composite material, denoted as Cu-Cu@SAPO-34.

[0056] The XRD of the Cu-Cu@SAPO-34 material obtained in this example is as Figure 1 shown. It can be seen through Figure 1 that this material has the unique CHA topological structure of SAPO-34, indicating that the addition of Cu does not destroy the structure of SAPO-34, and no diffraction peak of CuO is found, proving that Cu is highly dispersed.

[0057] Test the NOx conversion rate of the Cu-Cu@SAPO-34 material obtained in Test Example 1 at different temperatures. The specific steps are as follows: First, granulate the Cu-Cu@SAPO-34 material obtained in Example 1 to 60 mesh, put the granulated sample into a quartz tube, fill both ends with quartz wool and quartz sand, and then place it in a fixed-bed reactor. The reaction gas is a mixed gas of NO, NH3, O2, and N2, where the concentration of NO is 1000 ppm, the concentration of NH3 is 1000 ppm, and the volume percentage of O2 is 5%; use nitrogen as the balance gas, control the total flow rate at 200 mL / min, and the volume space velocity is GHSV = 40000 h -1 , test the NOx conversion rate of the Cu-Cu@SAPO-34 material obtained in Test Example 1 at different temperatures. The obtained NOx conversion rate curves at different temperatures are as Figure 2 shown. It can be seen from Figure 2 that the denitrification performance of Cu-Cu@SAPO-34 is good, and a NO conversion of 90% can be achieved in the temperature range of 130 °C to 430 °C.

[0058] Comparative Example 1: This comparative example is to prepare a Cu-modified SAPO-34 composite material. The specific preparation method is carried out according to the following steps:

[0059] 1. First, dissolve 3.0 g of pseudo-boehmite with 75% mass percentage of Al2O3 in 30 mL of deionized water, and stir it on a magnetic stirrer at room temperature for 1 h; then add 2.5 mL of H3PO4 and continue stirring for 1 h; then add 1.5 g of silica white with 88% mass percentage of SiO2 and continue stirring for 2 h; then add 8 mL of triethylamine (TEA) and continue stirring for 1 h; then add 3 mL of tetraethylenepentamine (TEPA) and stir for 2 h; finally, add 1.5 g of copper glycinate (C4H8CuN2O4) and stir for 12 h to obtain a sol-gel;

[0060] 2. After ultrasonic treatment of the sol-gel obtained in step 1, transfer it to a hydrothermal reaction kettle, and then place the hydrothermal reaction kettle in an oven at 200 °C for 24 h for hydrothermal reaction. Wash the product 3 times with deionized water and ethanol respectively, centrifuge and dry it in an oven at 80 °C for 8 h to obtain a precursor;

[0061] 3. After grinding the precursor into powder, place it in a porcelain boat, put it in a high-temperature furnace, heat it up to 550 °C and calcine it for 5 h to remove the template agent therein, and obtain a Cu-modified SAPO-34 composite material, denoted as Cu-SAPO-34;

[0062] The XRD of the Cu-SAPO-34 material obtained in this comparative example is as Figure 3 shown. It can be seen from Figure 3 that this material has the unique CHA topological structure of SAPO-34, indicating that the addition of Cu does not damage the structure of SAPO-34, and no diffraction peak of CuO is found, proving that Cu is highly dispersed.

[0063] Using the same method as in Example 1, test the NOx conversion rate of the Cu-SAPO-34 material obtained in Comparative Example 1 at different temperatures. The NOx conversion rate curve of the Cu-SAPO-34 material in Comparative Example 1 at different temperatures is as Figure 4 shown. It can be seen from Figure 4 that the Cu-SAPO-34 material obtained in Comparative Example 1 reaches 90% conversion at 150 °C to 420 °C. The lowest temperature in the good denitrification performance range is about 20 °C higher than that in Example 1, and the temperature range in the good denitrification performance range is also narrower than that in Example 1.

[0064] Perform nitrogen adsorption-desorption test on the Cu-Cu@SAPO-34 prepared in Example 1, and the obtained nitrogen adsorption-desorption curve is as Figure 5 shown. It can be seen from Figure 5 that this catalyst is a type IV isotherm and an H3-type hysteresis loop, indicating that this catalyst has a mesoporous structure.

[0065] The Cu-Cu@SAPO-34 prepared in Example 1 was subjected to synchrotron radiation testing, and the synchrotron radiation results obtained were as follows Figure 6 As shown, from Figure 6 it can be seen that the Cu-Cu@SAPO-34 obtained in Example 1 has both Cu-O bonds and Cu-Cu bonds. Therefore, the sample obtained in Example 1 is an atomically dispersed Cu-Cu catalyst. The Cu-Cu active sites are neither easily agglomerated nor can form sufficient active sites during the reaction, thus improving the low-temperature activity and stability of the reaction.

[0066] The Cu-Cu@SAPO-34 prepared in Example 1 was subjected to hydrothermal stability testing. The specific steps were as follows: First, the sample was placed in a quartz tube, and N2 was used as the carrier gas to make GHSV = 40000 h -1 , and 6% water vapor was introduced into the quartz tube. The sample was heat-treated at 80 °C for 12 hours and 650 °C for 12 hours respectively. Then, using the same method as in Example 1, the NO conversion rate of the Cu-Cu@SAPO-34 material obtained in Example 1 after hydrothermal treatment at different temperatures was tested. The NO conversion rate images of the Cu-Cu@SAPO-34 material at different temperatures were as follows Figure 7 As shown, it can be seen from the figure that Cu-Cu@SAPO-34 has excellent hydrothermal stability. Even after hydrothermal treatment at 80 °C, the conversion rate can reach 90% at 180 °C - 390 °C, and after hydrothermal treatment at 650 °C, the conversion rate can reach 90% at 150 °C - 360 °C.

[0067] The Cu-Cu@SAPO-34 prepared in Example 1 was subjected to water and sulfur resistance performance testing. The specific steps were as follows: First, the Cu-Cu@SAPO-34 material obtained in Example 1 was granulated to 60 mesh, and the granulated sample was placed in a quartz tube and then placed in a fixed-bed reactor. The reaction gas was a mixed gas of NO, NH3, and O2, where the concentration of NO was 1000 ppm, the concentration of NH3 was 1000 ppm, and the volume percentage of O2 was 5%; nitrogen was used as the balance gas, and the total flow rate was controlled at 200 mL / min, and the volume space velocity was GHSV = 40000 h -1 . On the basis of this, 6% and 12% H2O and 100 ppm and 200 ppm SO2 were successively introduced into the system, and the measured NO conversion rates were as follows Figure 8 As shown, from Figure 8 it can be seen that even when 100 ppm SO2 and 5% H2O were introduced simultaneously, the conversion rate still remained at 95%, proving that the catalyst has good water and sulfur resistance capabilities.

[0068] Example 2: The difference between this example and Example 1 is that "1.5 g of copper glycinate and 0.45 g of oxalic acid" in Step 2 is replaced with "1.8 g of copper acetylacetonate and 0.53 g of oxalic acid", so that the molar ratio of copper to oxalic acid is 2:1. Other steps and parameters are the same as those in Example 1, and a SAPO-34 composite material with Cu-Cu active sites is obtained, denoted as Cu-Cu@SAPO-34 material.

[0069] The XRD of the Cu-Cu@SAPO-34 material obtained in this Example 2 is as Figure 9 shown. It can be seen through Figure 9 that this material has the unique CHA topological structure of SAPO-34, indicating that the addition of Cu does not destroy the structure of SAPO-34, and no diffraction peak of CuO is found, proving that Cu is highly dispersed.

[0070] Using the same method as in Example 1, the NO conversion rates of the Cu-Cu@SAPO-34 material obtained in Example 2 at different temperatures are tested. The NO conversion rate images of the obtained Cu-Cu@SAPO-34 material at different temperatures are as Figure 10 shown. It can be seen from the figure that the Cu-Cu@SAPO-34 material has good denitrification performance and can reach 90% conversion at 150°C to 380°C.

[0071] Comparative Example 2: The difference between this comparative example and Comparative Example 1 is that "1.5 g of copper glycinate" in Step 1 is replaced with "1.8 g of copper acetylacetonate". Other steps and parameters are the same as those in Comparative Example 1, and a Cu-modified SAPO-34 composite material is obtained, denoted as Cu-SAPO-34 material.

[0072] The XRD of the Cu-SAPO-34 material obtained in this Comparative Example 2 is as Figure 11 shown. It can be seen through Figure 11 that this material has the unique CHA topological structure of SAPO-34, indicating that the addition of Cu does not destroy the structure of SAPO-34, and no diffraction peak of CuO is found, proving that Cu is highly dispersed.

[0073] Using the same test method as in Example 1, the NO conversion rates of the Cu-SAPO-34 material obtained in Comparative Example 2 at different temperatures are tested. The NO conversion rate images of the obtained Cu-SAPO-34 material at different temperatures are as Figure 12 shown. It can be seen from the figure that the denitrification performance of Cu-SAPO-34 can reach 90% conversion at 170°C to 390°C. The lowest temperature in the good denitrification performance range is about 20°C higher than that in Example 2, indicating that the reaction activity of Cu-Cu@SAPO-34 with atomically dispersed Cu-Cu active sites is higher.

[0074] Example 3: The difference between this example and Example 1 is that "1.5 g of copper glycinate and 0.45 g of oxalic acid" in Step 1 is replaced with "1.5 g of copper glycinate and 0.89 g of oxalic acid" to make the molar ratio of copper to oxalic acid 1:1. Other steps and parameters are the same as those in Example 1, and a SAPO-34 composite material with Cu-Cu active sites is obtained.

[0075] The XRD pattern of the SAPO-34 composite material with Cu-Cu active sites prepared in Example 3 is as Figure 13 shown. From Figure 13 it can be seen that this material belongs to the CHA structure.

[0076] Using the same test method as in Example 1, the NO conversion rates of the SAPO-34 composite material with Cu-Cu active sites prepared in Example 3 at different temperatures were tested, and the obtained conversion rate curve is as Figure 14 shown. From Figure 14 it can be seen that the Cu-Cu@SAPO-34 material has good denitrification performance and can reach 90% conversion at 175 °C to 400 °C.

[0077] Example 4: The difference between this example and Example 1 is that "1.5 g of copper glycinate and 0.45 g of oxalic acid" in Step 1 is replaced with "1.5 g of copper glycinate and 1.78 g of oxalic acid" to make the molar ratio of copper to oxalic acid 1:2. Other steps and parameters are the same as those in Example 1, and a SAPO-34 composite material with Cu-Cu active sites is obtained.

[0078] The XRD pattern of the SAPO-34 composite material with Cu-Cu active sites prepared in Example 4 is as Figure 15 shown. From Figure 15 it can be seen that this material belongs to the CHA structure.

[0079] Using the same test method as in Example 1, the NO conversion rates of the SAPO-34 composite material with Cu-Cu active sites prepared in Example 4 at different temperatures were tested, and the obtained conversion rate curve is as Figure 16 shown. From Figure 16 it can be seen that the Cu-Cu@SAPO-34 material has good denitrification performance and can reach 90% conversion at 175 °C to 370 °C.

[0080] Example 5: The difference between this example and Example 1 is that "1.5 g of copper glycinate and 0.45 g of oxalic acid" in Step 1 is replaced with "1.5 g of copper glycinate and 2.67 g of oxalic acid" to make the molar ratio of copper to oxalic acid 1:3. Other steps and parameters are the same as those in Example 1, and a SAPO-34 composite material with Cu-Cu active sites is obtained.

[0081] The XRD pattern of the SAPO-34 composite material with Cu-Cu active sites prepared in Example 5 is as follows Figure 17 shown. From Figure 17 it can be seen that this material belongs to the CHA structure.

[0082] Using the same test method as in Example 1, the NO conversion rate of the SAPO-34 composite material with Cu-Cu active sites prepared in Example 5 at different temperatures was tested, and the obtained conversion rate curve is as follows Figure 18 shown. From Figure 18 it can be seen that the Cu-Cu@SAPO-34 material has good denitrification performance and can reach 90% conversion at 190 °C to 380 °C.

[0083] Compared with Examples 1, 3, and 5, the molar ratio of copper glycinate to oxalic acid is different. Under the conditions of Example 1, copper glycinate and oxalic acid are completely complexed, enabling the two to fully combine, and the effect of regulating the distribution of Cu is the best, enabling more copper to form Cu-Cu bimetallic active sites, thereby improving the catalytic effect.

[0084] In the present invention, inexpensive silica, pseudoboehmite, and phosphoric acid are used as Si, Al, and P sources, and the organic copper source treated with oxalic acid is used as the copper source. By adding this copper source, the distribution of Cu is regulated, a catalyst with atomically dispersed Cu-Cu dual active sites is formed, and the stability of the molecular sieve structure is significantly improved, thereby improving the low-temperature activity and hydrothermal stability. The preparation method is simple and low-cost, and can be synthesized on a large scale. At the same time, this catalyst exhibits high low-temperature SCR activity, N2 selectivity, excellent hydrothermal stability, and water and sulfur resistance in the NH3-SCR denitrification reaction.

Claims

1. A method for preparing a SAPO-34 composite material having Cu-Cu active sites, characterized in that: The method proceeds as follows:

1. Weigh pseudo-boehmite, H3PO4, white carbon black, triethylamine, and tetraethylenepentamine; the mass ratio of pseudo-boehmite to white carbon black is (1.1-2.7):1; the volume ratio of H3PO4 to the mass of white carbon black is (1.3-2) mL:1 g; First, dissolve pseudo-boehmite in deionized water and stir on a magnetic stirrer at room temperature for 0 to 4 hours; then add H3PO4 and continue stirring for 0 to 4 hours; then add white carbon black and continue stirring for 2 to 2.5 hours; then add triethylamine and continue stirring for 0 to 4 hours; then add tetraethylenepentamine and stir for 2 to 2.5 hours to obtain solution A; 2. Pre-treat the copper source: add the copper source and the acid treatment agent into deionized water, stir until completely dissolved, and obtain solution B; wherein the copper source is copper glycinate or copper acetylacetonate; and the acid treatment agent is oxalic acid; 3. Mixing solutions A and B, stirring for 10 to 20 hours to obtain a sol-gel; 4. After ultrasonic treatment, the sol-gel obtained in step 3 is transferred to a hydrothermal reactor, and then the hydrothermal reactor is placed in an oven at a temperature of 180-200° C. for 24-48 hours for hydrothermal reaction, and the product is washed with deionized water and ethanol in turn, centrifuged and dried to obtain a precursor; 5. After the precursor is ground into powder, it is placed in a porcelain boat, placed in a muffle furnace, and heated to 550-580° C. and calcined for 5-6 hours to remove the template therein, thereby obtaining a SAPO-34 composite material with Cu-Cu active sites, which is recorded as Cu-Cu@SAPO-34.

2. The method for preparing a SAPO-34 composite material having Cu-Cu active sites according to claim 1, characterized in that: The ratio of the mass of the white carbon black described in step 1 to the volume of triethylamine is 1 g: (3.3-6.7) mL.

3. The method for preparing a SAPO-34 composite material having Cu-Cu active sites according to claim 1 or 2, characterized in that: The ratio of the mass of the white carbon black described in step 1 to the volume of tetraethylenepentamine is 1 g: (1.3-2) mL.

4. The method for preparing a SAPO-34 composite material having Cu-Cu active sites according to claim 1 or 2, characterized in that: The copper source described in step 2 is copper glycinate, and the acid treatment agent is oxalic acid; the molar ratio of copper glycinate to oxalic acid is (0.3-2.3):

1.

5. The method for preparing a SAPO-34 composite material having Cu-Cu active sites according to claim 1 or 2, characterized in that: The copper source described in step 2 is copper glycinate, and the acid treatment agent is oxalic acid; the molar ratio of copper glycinate to oxalic acid is (1.8-2.2):

1.

6. The method for preparing a SAPO-34 composite material having Cu-Cu active sites according to claim 1 or 2, characterized in that: The copper source described in step 2 is copper acetylacetonate, and the acid treatment agent is oxalic acid; the molar ratio of copper acetylacetonate to oxalic acid is (0.3-2.3):

1.

7. The method for preparing a SAPO-34 composite material having Cu-Cu active sites according to claim 1 or 2, characterized in that: The copper source described in step 2 is copper acetylacetonate, and the acid treatment agent is oxalic acid; the molar ratio of copper acetylacetonate to oxalic acid is (1.8-2.2):

1.

8. The method for preparing a SAPO-34 composite material having Cu-Cu active sites according to claim 1 or 2, characterized in that: The mass ratio of the white carbon black described in step one to the copper acetylacetonate described in step two is 1:(0.6-1.4).

9. The method for preparing a SAPO-34 composite material having Cu-Cu active sites according to claim 1 or 2, characterized in that: The mass ratio of the white carbon black described in step one to the copper glycinate described in step two is 1:(0.5-1).

10. Use of the SAPO-34 composite material having Cu-Cu active sites prepared by the method of claim 1, characterized in that: The application is to use the SAPO-34 composite material with Cu-Cu active sites as a catalyst in the catalytic selective reduction reaction of ammonia.

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