Preparation method and application of copper-modified SAPO-34 composite material

Abstract

The application relates to a preparation method of a catalyst for selective catalytic reduction of NO, and aims to solve the technical problems of existing denitration molecular sieve catalysts Cu- SAPO-34, such as easy agglomeration of active sites, poor low-temperature activity, poor hydrothermal stability, poor water resistance and poor sulfur resistance. The method comprises the following steps: taking pseudo-boehmite, H3PO4, white carbon black, triethylamine, tetraethylenepentamine and a copper organic complex to prepare a sol-gel; the copper organic complex is acetylacetone copper, glycine copper or dihydroxyethylenediamine copper; the sol-gel is subjected to hydrothermal reaction, the obtained precursor is calcined, and a Cu-modified SAPO-34 composite material is obtained. The material has a denitration conversion rate of 90% to 100% at 150 DEG C to 430 DEG C, has N2 selectivity, is resistant to water vapor and sulfur dioxide, and can be used in the field of NH3-SCR denitration.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation method of a catalyst for selective catalytic reduction of NO, and belongs to the field of selective catalytic reduction of NO. BACKGROUND

[0002] With the rapid development of human activities and the continuous improvement of living standards, people pay more and more attention to environmental problems. At present, the main environmental problems we are facing are two types: one is the original environmental problem caused by the evolution of nature and natural disasters, also known as the first environmental problem. One is the environmental problem caused by human activities, also known as the second environmental problem, which is divided into two categories: environmental pollution and ecological destruction. At present, the emission of nitrogen oxides in automobile exhaust, especially the emission of diesel vehicle exhaust, is particularly prominent in air pollution.

[0003] Catalytic selective reduction of ammonia (NH3-SCR) is considered to be an effective technology to eliminate nitrogen oxide pollution. Existing denitration catalysts can be roughly divided into three categories: noble metal catalysts, metal oxide catalysts, and molecular sieve catalysts. CO produced by incomplete combustion of fuel in noble metal catalysts is easy to cause poisoning and deactivation of the active components of noble metal catalysts, and the high cost limits its further development; metal oxide catalysts, such as V2O5-WO3(MoO3) / TiO2, have the disadvantages of high NO complete conversion temperature, limited operating temperature window, and biological toxicity of V species, which are not suitable for eliminating nitrogen oxides in automobile exhaust; the commonly used molecular sieve catalysts are Cu-SAPO-34 and Cu-SSZ-13, but both of them have the problems of easy agglomeration of active species Cu, poor low-temperature activity, poor water resistance, and poor hydrothermal stability. SUMMARY

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

[0005] The preparation method of the Cu-modified SAPO-34 composite material of the present application is carried out in the following steps:

[0006] I. Weighed pseudo-boehmite, H3PO4, white carbon black, triethylamine (TEA), tetraethylenepentamine (TEPA), and copper organic complex;

[0007] The mass ratio of pseudo-boehmite to white carbon black is (1.1-2.7):1;

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

[0009] The copper organic complex is copper acetylacetonate, copper glycinate or copper dihydroxide ethylenediamine;

[0010] Firstly, the pseudo-boehmite is dissolved in deionized water, stirred on a magnetic stirrer at room temperature for 0-4h; then H3PO4 is added, and stirring is continued for 0-4h; then white carbon black is added, and stirring is continued for 2-2.5h; then triethylamine (TEA) is added, and stirring is continued for 0-4h; then tetraethylenepentamine (TEPA) is added and stirred for 2-2.5h; finally, the copper organic complex is added, and stirring is continued for 8-16h to obtain a sol-gel;

[0011] Secondly, the sol-gel obtained in step one is ultrasonically treated and then transferred to a hydrothermal reactor, which is placed in an oven at a temperature of 180-200℃ for 24-48h for hydrothermal reaction. The product is washed with deionized water and ethanol in sequence, centrifuged and dried to obtain a precursor.

[0012] Thirdly, the precursor is ground into powder, placed in a porcelain boat and placed in a muffle furnace, which is heated to 550-580℃ and calcined for 5-6h to obtain a Cu-modified SAPO-34 composite material, which is denoted as Cu-SAPO-34.

[0013] Further, the mass percentage of Al2O3 in the pseudo-boehmite in step one is ≥70%.

[0014] Further, the mass percentage of SiO2 in the white carbon black in step one is ≥85%.

[0015] Further, the mass of the white carbon black in step one to the volume of triethylamine (TEA) is 1g:(3.3-6.7)mL.

[0016] Further, the mass of the white carbon black in step one to the volume of tetraethylenepentamine (TEPA) is 1g:(1.3-2)mL.

[0017] Further, the mass of the white carbon black in step one to the mass of copper acetylacetonate is 1:(0.6-1.4).

[0018] Further, the mass of the white carbon black in step one to the mass of copper glycinate is 1:(0.5-1).

[0019] Further, the mass of the white carbon black in step one to the volume of copper dihydroxide ethylenediamine is 1g:(3.3-6.7)mL.

[0020] The application of the Cu-modified SAPO-34 composite material prepared by the above method is that the Cu-modified SAPO-34 composite material is used as a catalyst in NH3-SCR denitration reaction.

[0021] The advantages of the present application are as follows:

[0022] (1) The present application synthesizes and prepares Cu-SAPO-34 by one-step hydrothermal method, which is simple in operation, short in time consumption, low in cost, large in yield and can be produced in large scale.

[0023] (2) The present application uses copper acetylacetonate, copper glycinate and copper dihydroxide ethylenediamine as copper source, and the organic structure in the copper organic complex is conducive to coordination with silicon hydroxyl and aluminum hydroxyl in the molecular sieve, forming Cu-SAPO-34 with atomic dispersion Cu active sites, so that Cu is not easy to agglomerate in the reaction, thereby improving the low-temperature activity and stability of the reaction. Meanwhile, the active substance copper in the catalyst is more uniformly dispersed, and more copper species is located in the active sites of the molecular sieve six-membered ring and eight-membered ring, and the content of the active copper species can be controlled.

[0024] (3) In the present application, tetraethylene pentamine (TEPA) is used as a dispersant and a pore-forming agent, rather than a common template agent. Through the addition of 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 limitation, thereby improving the reaction activity.

[0025] (4) The Cu-SAPO-34 catalyst prepared in the present application exhibits extremely superior low-temperature SCR activity in the NH3-SCR reaction, and the denitration conversion rate can reach 90% to 100% at 150℃ to 430℃. Meanwhile, the catalyst has N2 selectivity, and can still maintain good reaction activity when a large amount of water vapor and sulfur dioxide is introduced, and can still maintain excellent reaction activity after high-temperature hydrothermal treatment.

[0026] The Cu-modified SAPO-34 composite material of the present application can be used in the field of NH3-SCR denitration, such as elimination of automobile exhaust nitrogen oxides. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 XRD image of Cu-SAPO-34 obtained in Example 1;

[0028] Figure 2 NO conversion rate image of Cu-SAPO-34 obtained in Example 1 at different temperatures;

[0029] Figure 3 XRD image of Cu-SAPO-34 obtained in Example 2;

[0030] Figure 4 NO conversion rate image of Cu-SAPO-34 obtained in Example 2 at different temperatures;

[0031] Figure 5XRD pattern of Cu-SAPO-34 obtained from Example 3;

[0032] Figure 6 NO conversion at different temperatures of Cu-SAPO-34 obtained from Example 3;

[0033] Figure 7 XRD pattern of Cu-SAPO-34 obtained from Example 4;

[0034] Figure 8 NO conversion at different temperatures of Cu-SAPO-34 obtained from Example 4;

[0035] Figure 9 XRD pattern of Cu-SAPO-34 obtained from Example 5;

[0036] Figure 10 NO conversion at different temperatures of Cu-SAPO-34 obtained from Example 5;

[0037] Figure 11 N2adsorption-desorption of Cu-SAPO-34 obtained from Example 3;

[0038] Figure 12 Water and sulfur resistance test of Cu-SAPO-34 obtained from Example 3;

[0039] Figure 13 Synchrotron results of Cu / SAPO-34 obtained from Example 3;

[0040] Figure 14 XRD pattern of Cu-SAPO-34 obtained from Example 6;

[0041] Figure 15 NO conversion at different temperatures of Cu-SAPO-34 obtained from Example 6;

[0042] Figure 16 XRD pattern of Cu-SAPO-34 obtained from Example 7;

[0043] Figure 17 NO conversion at different temperatures of Cu-SAPO-34 obtained from Example 7;

[0044] Figure 18 NO conversion at different temperatures of Cu-SAPO-34 obtained from different copper sources. DETAILED DESCRIPTION

[0045] The advantageous effects of the present application are verified by the following examples.

[0046] Example 1: The preparation method of Cu-modified SAPO-34 composite material in this example is carried out according to the following steps:

[0047] I. First, 3.0 g of pseudoboehmite (mass percentage of Al2O3 is 75%) is dissolved in 30 mL of deionized water, and stirred at room temperature on a magnetic stirrer for 1 h; then 2.5 mL of H3PO4 is added, and stirring is continued for 1 h; then 1.5 g of white carbon black (mass percentage of SiO2 is 88%) is added, and stirring is continued for 2 h; then 8 mL of triethylamine (TEA) is added, and stirring is continued for 1 h; then 3 mL of tetraethylenepentamine (TEPA) is added and stirring is continued for 2 h; finally, 1.0 g of copper acetylacetonate is added, and stirring is continued for 12 h to obtain a sol-gel;

[0048] II. The sol-gel obtained in step I is ultrasonically treated, and then transferred to a hydrothermal reaction kettle, which is placed in an oven at a temperature of 180℃ for 24 h for hydrothermal reaction. The product is sequentially washed with deionized water and ethanol for 3 times respectively, centrifuged and dried in an oven at a temperature of 30℃ for 8 h to obtain a precursor;

[0049] III. The precursor is ground into a powder, which is placed in a porcelain boat and placed in a high-temperature furnace, and heated to 550℃ for calcination for 5 h to remove the template agent therein, to obtain a Cu-modified SAPO-34 composite material, which is denoted as Cu-SAPO-34;

[0050] The XRD of the Cu-SAPO-34 material obtained in this example is shown in Figure 1 It can be seen from Figure 1 that the material has a CHA topology structure specific to 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.

[0051] The NO conversion rate of the Cu-SAPO-34 material obtained in Example 1 at different temperatures is tested, and the specific steps are as follows:

[0052] First, the Cu-SAPO-34 material obtained in Example 1 is granulated to 40-60 mesh, and the granulated sample is placed in a quartz tube, and then placed in a fixed bed reactor. The reaction gas is a mixed gas of NO, NH3 and O2, wherein the concentration of NO is 1000 ppm, the concentration of NH3 is 1000 ppm, and the volume percentage of O2 is 5%. Nitrogen is used as the balance gas, and the total flow rate is controlled at 200 mL / min, and the volume space velocity is GHSV = 40000 h -1 The NO conversion rate of the Cu-SAPO-34 material obtained in Example 1 at different temperatures is tested, and the NO conversion rate curve at different temperatures is shown in Figure 2 From Figure 2It can be seen from the figure that the Cu-SAPO-34 material obtained in Example 1 has good denitration performance, and the conversion rate is above 95% at 160-400°C.

[0053] Example 2: The difference between this example and Example 1 is that "1.0 g of copper acetylacetonate" in Step 1 is replaced with "1.2 g of copper acetylacetonate", and other steps and parameters are the same as those in Example 1, to obtain a Cu-modified SAPO-34 composite material, which is denoted as Cu-SAPO-34 material.

[0054] The XRD of the Cu-SAPO-34 material obtained in this example 2 is shown in Figure 3 It can be seen from the figure that the Cu-SAPO-34 material obtained in Example 1 has good denitration performance, and the conversion rate is above 95% at 160-400°C. Figure 3 It can be seen from the figure that the Cu-SAPO-34 material obtained in Example 1 has good denitration performance, and the conversion rate is above 95% at 160-400°C.

[0055] Figure 4 The XRD of the Cu-SAPO-34 material obtained in this example 3 is shown in It can be seen from the figure that the Cu-SAPO-34 material obtained in Example 1 has good denitration performance, and the conversion rate is above 95% at 160-400°C.

[0056] It can be seen from the figure that the Cu-SAPO-34 material obtained in Example 1 has good denitration performance, and the conversion rate is above 95% at 160-400°C.

[0057] Figure 5 It can be seen from the figure that the Cu-SAPO-34 material obtained in Example 1 has good denitration performance, and the conversion rate is above 95% at 160-400°C. Figure 5 It can be seen from the figure that the Cu-SAPO-34 material obtained in Example 1 has good denitration performance, and the conversion rate is above 95% at 160-400°C.

[0058] Figure 6 It can be seen from the figure that the Cu-SAPO-34 material obtained in Example 1 has good denitration performance, and the conversion rate is above 95% at 160-400°C.

[0059] ​​Example 4: The difference between this example and Example 1 is that "1.0 g of copper acetylacetonate" in Step 1 is replaced by "1.4 g of copper acetylacetonate", and other steps and parameters are the same as those in Example 1, to obtain a Cu-modified SAPO-34 composite material, which is denoted as Cu-SAPO-34 material.

[0060] The XRD of the Cu-SAPO-34 material obtained in this example 4 is shown in Figure 7 Figure 7 It can be seen that the material has the CHA topology structure specific to 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.

[0061] The Cu-SAPO-34 material obtained in Example 4 is tested for NO conversion rate at different temperatures by using the same method as that in Example 1, and the NO conversion rate image of the Cu-SAPO-34 material at different temperatures is shown in Figure 8 It can be seen from the figure that the denitration performance of Cu-SAPO-34 is good, and can reach more than 95% conversion at 150℃-400℃.

[0062] Example 5: The difference between this example and Example 1 is that "1.0 g of copper acetylacetonate" in Step 1 is replaced by "1.6 g of copper acetylacetonate", and other steps and parameters are the same as those in Example 1, to obtain a Cu-modified SAPO-34 composite material, which is denoted as Cu-SAPO-34 material.

[0063] The XRD of the Cu-SAPO-34 material obtained in this example 5 is shown in Figure 9 Figure 9 It can be seen that the material has the CHA topology structure specific to 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.

[0064] The Cu-SAPO-34 material obtained in Example 5 is tested for NO conversion rate at different temperatures by using the same method as that in Example 1, and the NO conversion rate image of the Cu-SAPO-34 material at different temperatures is shown in Figure 10 It can be seen from the figure that the denitration performance of Cu-SAPO-34 is good, and can reach more than 95% conversion at 160℃-400℃.

[0065] The Cu-SAPO-34 materials prepared in Examples 1-5 all have good denitration performance. Among them, the denitration performance of the Cu-SAPO-34 prepared in Example 3 is the best, and the nitrogen adsorption-desorption test of the Cu-SAPO-34 prepared in Example 3 is carried out, and the nitrogen adsorption-desorption curve obtained is as follows​​Figure 11 As shown, from Figure 11 It can be seen that the catalyst has a type IV isotherm and an H3 type hysteresis ring, indicating that the catalyst has a mesoporous structure.

[0066] The Cu-SAPO-34 prepared in Example 3 was tested for its water and sulfur resistance. The specific steps were as follows: First, the Cu-SAPO-34 material obtained in Example 1 was granulated to 40-60 mesh. The granulated sample was placed in a quartz tube and then placed in a fixed-bed reactor. The reaction gas was a mixture of NO, NH3, and O2, with NO concentration of 1000 ppm, NH3 concentration of 1000 ppm, and O2 volume percentage of 5%. Nitrogen was used as the balance gas, the total flow rate was controlled at 200 mL / min, and the volume hourly space velocity (GHSV) was 40000 h⁻¹. -1 Based on this, the NO conversion rate was measured when 5% H2O, 10% H2O, 100ppm SO2, 200ppm SO2, and simultaneously 100ppm SO2 and 5% H2O were introduced into the system, as follows: Figure 12 As shown, from Figure 12 It can be seen that even when 100ppm SO2 and 5% H2O are introduced simultaneously, the conversion rate is still maintained at 100%, proving that the catalyst has good resistance to water and sulfur.

[0067] The Cu-SAPO-34 prepared in Example 3 was subjected to synchrotron radiation testing, and the synchrotron radiation results are as follows: Figure 13 As shown, from Figure 13 It can be seen that Cu / SAPO-34 has Cu-O bonds, not Cu-Cu bonds. Therefore, the Cu / SAPO-34 obtained in Example 3 is an atomically dispersed catalyst.

[0068] Example 6: This example differs from Example 1 in that "1.0g of copper acetylacetone" in step one is replaced with "1.0g of copper glycine". The other steps and parameters are the same as in Example 1, and Cu-modified SAPO-34 composite material is obtained, which is denoted as Cu-SAPO-34 material.

[0069] The XRD pattern of the Cu-SAPO-34 material obtained in Example 6 is as follows: Figure 14 As shown, through Figure 14 It can be seen that the material has the unique CHA topology of SAPO-34, indicating that the addition of Cu did not destroy the structure of SAPO-34. No diffraction peaks of CuO were found, proving that Cu is highly dispersed.

[0070] The Cu-SAPO-34 material obtained in Example 6 was tested for NO conversion at different temperatures using the same method as in Example 1, and the image of the NO conversion of the Cu-SAPO-34 material at different temperatures is shown in Figure 15 From the graph, it can be seen that the Cu-SAPO-34 has good denitration performance, and the conversion can reach more than 90% at 150°C to 350°C.

[0071] Example 7: In this example, the "1.0 g of copper acetylacetonate" in step one was replaced with "8 mL of copper dihydroxide ethylenediamine", and the other steps and parameters were the same as in Example 1, to obtain a Cu-modified SAPO-34 composite material, which was denoted as Cu-SAPO-34 material.

[0072] The XRD of the Cu-SAPO-34 material obtained in this example 7 is shown in Figure 16 From the Figure 16 It can be seen that the material has the CHA topology structure specific to 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] The Cu-SAPO-34 material obtained in Example 7 was tested for NO conversion at different temperatures using the same method as in Example 1, and the image of the NO conversion of the Cu-SAPO-34 material at different temperatures is shown in Figure 17 From the graph, it can be seen that the Cu-SAPO-34 has good denitration performance, and the conversion can reach more than 90% at 160°C to 400°C.

[0074] Comparative Example 1: In this example, the "1.0 g of copper acetylacetonate" in step one was replaced with "0.7 g of copper citrate", and the other steps and parameters were the same as in Example 1, to obtain a Cu-modified SAPO-34 composite material, which was denoted as Cu-SAPO-34 material.

[0075] Comparative Example 2: In this example, the "1.0 g of copper acetylacetonate" in step one was replaced with "1.0 g of copper sodium chlorophyllin", and the other steps and parameters were the same as in Example 1, to obtain a Cu-modified SAPO-34 composite material, which was denoted as Cu-SAPO-34 material.

[0076] Comparative Example 3: In this example, the "1.0 g of copper acetylacetonate" in step one was replaced with "1.5 g of copper quinoline", and the other steps and parameters were the same as in Example 1, to obtain a Cu-modified SAPO-34 composite material, which was denoted as Cu-SAPO-34 material.

[0077] Using the same test method as in Example 1, the NO conversion rates of the Cu-SAPO-34 materials prepared in Example 6, Example 7, and Comparative Examples 1-3 at different temperatures were tested, and the conversion rate curves obtained are shown in Figure 18 The conversion rate of the Cu-SAPO-34 material prepared in Example 3 is also plotted in Figure 18 From Figure 18 it can be seen that the NO conversion rates of the Cu-SAPO-34 materials prepared from the six different copper sources at different temperatures are not the same, and the Cu-SAPO-34 prepared in Example 3 using copper acetylacetonate as the copper source has the best denitration performance, achieving more than 95% conversion at 140-430°C, and the Cu-SAPO-34 prepared using copper glycinate and copper dihydroxyl ethylenediamine as the copper source has better denitration performance, achieving more than 90% conversion at 150-350°C and 160-400°C, respectively, and the Cu-SAPO-34 materials prepared using copper citrate, copper sodium chlorophyllin, and copper quinoline as the copper source have relatively poor performance.

[0078] The present application uses white carbon black, pseudo-boehmite, and phosphoric acid as Si, Al, and P sources, respectively, and uses a copper organic complex with a special structure as a copper source. The addition of the copper source adjusts the distribution of Cu, forms a catalyst with atomic-level dispersed active sites, and significantly improves the stability of the molecular sieve structure, thereby improving the low-temperature activity and hydrothermal stability. The preparation method is simple, the cost is low, and the catalyst can be synthesized on a large scale. At the same time, the catalyst exhibits high low-temperature SCR activity, N2 selectivity, excellent water and sulfur resistance, and good hydrothermal stability in the NH3-SCR denitration reaction.

Claims

1. A method for preparing a Cu-modified SAPO-34 composite material, characterized in that The method is carried out according to the following steps: I. Take pseudo-boehmite, H3PO4, white carbon black, triethylamine, tetraethylenepentamine and copper organic complex; 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; the copper organic complex is acetylacetone copper; the mass ratio of white carbon black to acetylacetone copper is 1:(0.6-1.4); First, dissolve the pseudo-boehmite in deionized water, stir at room temperature on a magnetic stirrer for 0-4 h; then add H3PO4 and continue to stir for 0-4 h; then add white carbon black and continue to stir for 2-2.5 h; then add triethylamine and continue to stir for 0-4 h; then add tetraethylenepentamine and stir for 2-2.5 h; finally add copper organic complex and stir for 8-16 h to obtain a sol-gel; II. After ultrasonic treatment of the sol-gel obtained in step I, transfer it to a hydrothermal reaction kettle, and then place the hydrothermal reaction kettle in an oven at a temperature of 180-200 DEG C for 24-48 h for hydrothermal reaction. Wash the product with deionized water and ethanol, centrifuge and dry to obtain a precursor; III. Grind the precursor into powder, place it in a porcelain boat, and then place the porcelain boat in a muffle furnace, heat to 550-580 DEG C and calcine for 5-6 h to obtain a Cu-modified SAPO-34 composite material.

2. The method for preparing Cu-modified SAPO-34 composite material according to claim 1, characterized in that, The mass percentage of Al2O3 in the pseudo-boehmite in step I is ≥70%.

3. The method for preparing the Cu-modified SAPO-34 composite material according to claim 1 or 2, characterized in that, The mass percentage of SiO2 in the white carbon black in step I is ≥85%.

4. The method for preparing the Cu-modified SAPO-34 composite material according to claim 1 or 2, characterized in that, The mass of white carbon black to the volume of triethylamine in step I is 1 g:(3.3-6.7) mL.

5. The method for preparing the Cu-modified SAPO-34 composite material according to claim 1 or 2, characterized in that, The mass of white carbon black to the volume of tetraethylenepentamine in step I is 1 g:(1.3-2) mL.

6. The use of Cu-modified SAPO-34 composite prepared by the method of claim 1, characterized in that, The application is to use Cu-modified SAPO-34 composite material as a catalyst in NH3-SCR denitration reaction.

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