Preparation method for synthesizing denitration catalyst from MTO waste agent

Abstract

The invention discloses a preparation method for synthesizing a denitration catalyst from an MTO waste agent. The method comprises the following steps: 1, mixing MTO waste agent and ammonium salt, roasting, adding water, stirring, filtering, and drying to obtain a solid 1; and 2, mixing and stirring the solid 1, a template agent, an active metal complex and a phosphorus source to prepare initial gel, and carrying out one-step hydrothermal crystallization, filtration, drying and roasting treatment to obtain the Cu / X-SAPO-34 denitration catalyst. The molecular sieve based denitration catalyst is prepared from rich silicon / aluminum / phosphorus sources in the MTO waste catalyst, and the method has the advantages of being simple in technological process, low in cost and safe in process and has industrialization prospects.

Description

Technical Field

[0001] The invention relates to the technical field of comprehensive utilization of industrial solid wastes, and in particular to a method for preparing a denitration catalyst synthesized from MTO waste agent. Background Art

[0002] During the operation of the MTO unit, catalyst fine powder is generated due to thermal collapse, wear and other reasons. Because it does not meet the fluidization conditions of the reactor, it is captured by the cyclone separator and discharged to form MTO waste catalyst. Currently, MTO waste catalyst is treated as solid waste, which affects the economic and environmental performance of the unit operation.

[0003] Currently in the ammonia selective catalytic reduction (NH3-SCR) technology, the copper-based SAPO-34 molecular sieve has become a new generation of molecular sieve low-temperature denitrification catalyst due to its good low-temperature activity, wide active temperature window and good hydrothermal stability, as well as its suitable pore structure and acidity.

[0004] A novel high-efficiency denitration catalyst, preparation method and application thereof, with publication number CN112604710A, is disclosed. The Cu-SAPO-34 molecular sieve catalyst synthesized in one step is modified by introducing fluoride ions. This method can promote the nucleation and crystallization of the molecular sieve, and at the same time has high crystallinity, uniform particle distribution, large specific surface area and pore volume, and suitable acidity. The denitration rate of NO in the range of 150℃ to 450℃ x The conversion rate can reach 60% to 96%. The preparation conditions of this method are harsh, which is not conducive to large-scale industrial production, and the ammonium fluoride used is highly corrosive and highly toxic, which will cause environmental pollution.

[0005] The patent publication number is CN110639609A, which discloses a core-shell structure Cu / SAPO-34@meso-TiO2 catalytic material, a preparation method and an application thereof. The patent first prepares a Cu / SAPO-34 molecular sieve, and then coats the Cu / SAPO-34 molecular sieve with a meso-TiO2 shell layer to obtain the catalytic material. The application of the catalytic material in the NH3-SCR denitration reaction has good denitration performance and good sulfur resistance.

[0006] The raw materials required for the preparation of this method are expensive, the preparation steps are complicated, the conditions are harsh, and it is not conducive to large-scale industrial production.

[0007] It can be seen from the existing literature and patent reports that SAPO-34 molecular sieve has been widely studied in the field of denitrification due to its good pore structure and suitable acidity. In particular, the metal-modified SAPO-34 molecular sieve-based denitrification catalyst exhibits efficient low-temperature denitrification catalytic activity, a wide SCR reaction activity window, and good thermal stability and water and sulfur resistance in the SCR denitrification process. However, due to the high cost of SAPO-34 molecular sieve, its application in the field of flue gas denitrification in fixed-source coal-fired power plants is limited.

[0008] In summary, the copper-based SAPO-34 denitrification catalyst exhibits excellent low-temperature denitrification performance and good water and sulfur resistance. However, the existing preparation technology has the disadvantages of expensive raw materials, harsh preparation conditions, and is not conducive to large-scale industrial production. Summary of the invention

[0009] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a method for preparing a denitration catalyst synthesized from MTO waste agent, which utilizes the abundant silicon / aluminum / phosphorus sources in the MTO waste catalyst to prepare a molecular sieve-based denitration catalyst. The catalyst has small crystals and suitable acid strength and abundant acid on the surface, which is conducive to the adsorption and activation of NH3, thereby promoting the low-temperature SCR reaction and improving the NO conversion rate. The method has the characteristics of simple process flow, low cost and safe process, and has industrial prospects.

[0010] In order to achieve the above object, the technical solution adopted by the present invention is:

[0011] A method for preparing a denitration catalyst by synthesizing MTO waste agent comprises the following steps:

[0012] Step 1: Mix the MTO waste agent and ammonium salt, roast, add water, stir, filter, and dry to obtain solid 1;

[0013] Step 2: The solid 1 is mixed with a template, an active metal complex, and a phosphorus source to prepare an initial gel, and then subjected to a step of hydrothermal crystallization, filtration, drying, and calcination to obtain a Cu / X-SAPO-34 denitration catalyst.

[0014] The Cu / X-SAPO-34 denitration catalyst is a small-grain Cu / X-SAPO-34 denitration catalyst with a size of 200nm-500nm.

[0015] In step 1, the ammonium salt is at least one of ammonium chloride, ammonium sulfate, ammonium bisulfate, ammonium carbonate and ammonium fluoride.

[0016] In the step 1, the mass ratio of the MTO waste catalyst to the ammonium salt is 1:(0.1-10), and the preferred mass ratio is 1:(0.3-5). This ratio can fragment the SAPO-34 molecular sieve structure in the MTO waste catalyst to generate a large number of SAPO-34 microcrystalline structures or secondary structural units and other structural fragments. These fragments are equivalent to providing a large number of crystal nuclei during the crystallization process, resulting in an increase in the supersaturated concentration of crystal nuclei in the mother liquor and a slowdown in the growth process of the crystals, thereby being able to synthesize a small-particle molecular sieve.

[0017] The calcination in step 1 is a two-stage calcination, the first stage calcination temperature is 300°C to 450°C, the heating rate is 3 to 8°C / min, and the calcination time is 1 to 4h;

[0018] The second stage calcination temperature is 600°C to 800°C, the heating rate is 10 to 15°C / min, and the calcination time is 2 to 6 hours.

[0019] During the filtration in step 1, the solution temperature should be maintained at 60° C. to 90° C. for hot filtration. At this temperature, precipitation of impurity salts can be prevented, and impurity ions in the filter cake can be effectively removed.

[0020] In step 2, the mass ratio of solid 1, template, active metal complex and phosphorus source is 1: (0.05-0.5): (0.01-0.1): (0.1-0.5). This ratio ensures that the SAPO-34 molecular sieve is generated by hydrothermal crystallization while the denitrification active metal components can enter the molecular sieve framework.

[0021] In step 2, the template agent is at least one of triethylamine, tetraethylammonium hydroxide, hexadecyltrimethylammonium bromide and morpholine.

[0022] In step 2, the phosphorus source is at least one of phosphoric acid and phosphorous acid.

[0023] In step 2, the active metal complex is prepared by mixing and stirring an active metal copper source, a manganese source / cerium source, and a complex;

[0024] The copper active metal source is a soluble copper salt, selected from at least one of copper nitrate, copper acetate and copper sulfate;

[0025] The manganese source is a soluble manganese salt, selected from at least one of manganese sulfate, manganese acetate and manganese nitrate;

[0026] The cerium source is a soluble copper salt, selected from at least one of cerium nitrate and cerium chloride;

[0027] The complexing agent is selected from at least one of diethylenetriamine, tetraethylenepentamine and pentaethylenehexamine;

[0028] The molar ratio of the active metal copper source, manganese source / cerium source and complex is 1:(0.01-1):(0.5-2).

[0029] The hydrothermal crystallization in step 2 is a two-stage crystallization method, wherein the first stage is crystallization at 200-220° C. for 2-4 hours, and the second stage is crystallization at 160-180° C. for 10-20 hours.

[0030] In step 2, a Buchner funnel is used for filtration, and the filtrate is rinsed with deionized water until the pH value of the filtrate is about 7.

[0031] The Cu / X-SAPO-34 denitration catalyst is used for fixed source denitration;

[0032] The prepared Cu / X-SAPO-34 denitrification catalyst was used in a gas composition of 500ppmNH3, 500ppmNO, 5%O2 and a space velocity of 30000h -1 In the atmosphere, the reaction temperature is between 180 and 300 °C. x The conversion rate can reach 60% to 99%;

[0033] During the denitrification reaction, the acidic sites of B acid and L acid on the surface of Cu / X-SAPO-34 catalyst will adsorb some ammonia molecules in the introduced ammonia gas, and then the active substances on the catalyst surface will react with NO in the gas phase to form nitrate or nitrite, and react chemically with the ammonia species adsorbed on the catalyst surface to form intermediate species of ammonium nitrate or ammonium nitrite. The intermediate ammonium salt is unstable and is catalytically reduced and decomposed into N2, H2O and a small amount of NO2 with the B acid provided on the catalyst surface. The generated NO2 can directly undergo self-disproportionation reaction to generate nitrite on the catalyst surface to participate in the SCR reaction.

[0034] Beneficial effects of the present invention:

[0035] The Cu / X-SAPO-34 denitration catalyst prepared by the present invention is a small-grain Cu / X-SAPO-34 denitration catalyst. The smaller crystal size is more conducive to the diffusion of reactants and products from the pores, thereby significantly improving the service life of the catalyst.

[0036] The present invention adopts two-stage calcination to ensure that the MTO waste catalyst and the ammonium salt react fully, and can remove carbon deposits in the pores of the waste catalyst at the same time.

[0037] The present invention adopts a two-stage crystallization method, which helps to further improve the structure of the molecular sieve and improve its crystallinity and purity.

[0038] The present invention aims to prepare a low-cost, low-temperature, high-activity molecular sieve-based denitration catalyst using MTO waste catalyst by mixed calcination of ammonium salts-one-step hydrothermal method. When the reaction temperature rises to 250°C, the NO conversion rate reaches 93.68%. When the temperature rises to 300°C, the NO conversion rate rises to 98.95%, showing good low-temperature SCR performance. The process is simple, low-cost and safe, and has industrial prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is the XRD diagram of the MTO waste catalyst and the SAPO-34 molecular sieve-based denitration catalyst synthesized in Examples 1 and 2.

[0040] Figure 2 The performance evaluation results of the SAPO-34 molecular sieve-based denitration catalyst NH3-SCR synthesized in Example 1 and Comparative Example 1 are shown.

[0041] Figure 3 Schematic diagram of TEM characterization of the catalyst. DETAILED DESCRIPTION

[0042] The present invention will be further described in detail below in conjunction with the accompanying drawings.

[0043] Example 1

[0044] Weigh 20g of MTO waste catalyst, mix it with 20g of ammonium sulfate, heat it to 350℃ at 5℃ / min, roast it for 2h, then heat it to 800℃ at 10℃ / min, roast it for 4h, add water to the obtained solid mixture, stir, filter, and dry to obtain solid 1. Mix 0.2g of copper sulfate, 0.05g of manganese nitrate, and 0.3g of tetraethylenepentamine and stir until they are completely dissolved to form an active metal complex for use. Take 10g of solid 1, 5g of triethylamine, 0.55g of metal complex, and 2g of 85% phosphoric acid solution, mix them, add deionized water, stir at room temperature for 4h, crystallize at 200℃ for 2h, crystallize at 160℃ for 10h, filter, dry, and roast to obtain the denitrification catalyst. The XRD characterization of the catalyst is as follows Figure 1 As shown, a typical CHA structure molecular sieve is presented, with characteristic peaks of SAPO-34 at 2θ = 9.5° (101), 12.8° (110), 16° (021), 20.5° (211), 26° (220) and 31° (401). The NH3-SCR performance evaluation results are shown in Figure 2 As shown in Figure 2, when the reaction temperature is increased to 300°C, the NO conversion rate is 97.05%, showing good denitrification performance. Figure 3 shown.

[0045] Example 2

[0046] Weigh 15g of MTO waste catalyst, mix it with 20g of ammonium sulfate, heat it to 300℃ at 8℃ / min, roast it for 4h, then heat it to 800℃ at 10℃ / min, roast it for 6h, add water to the obtained solid mixture, stir, filter, and dry to obtain solid 1. Mix 0.2g of copper sulfate, 0.03g of cerium nitrate, and 0.3g of tetraethylenepentamine and stir until they are completely dissolved to form an active metal complex for use. Take 10g of solid 1, 4g of triethylamine, 0.53g of metal complex, and 3.7g of 85% phosphoric acid solution, mix them, add deionized water, stir at room temperature for 4h, crystallize at 210℃ for 2h, crystallize at 180℃ for 10h, filter, dry, and roast to obtain the denitrification catalyst. The XRD characterization of the catalyst is as follows Figure 1 As shown, a typical CHA structure molecular sieve is presented, with characteristic peaks of SAPO-34 at 2θ = 9.5° (101), 12.8° (110), 16° (021), 20.5° (211), 26° (220) and 31° (401). The NH3-SCR performance evaluation results are shown in Figure 2 As shown, when the reaction temperature is increased to 300°C, the NO conversion rate is 99.56%, showing good denitration performance.

[0047] Weigh 15g of MTO waste catalyst, mix it with 15g of ammonium sulfate, heat it to 300℃ at 8℃ / min, roast it for 4h, then heat it to 800℃ at 10℃ / min, roast it for 6h, add water to the obtained solid mixture, stir, filter, and dry to obtain solid 1. Mix 0.2g of copper sulfate, 0.03g of manganese nitrate, and 0.3g of tetraethylenepentamine and stir until they are completely dissolved to form an active metal complex for use. Take 10g of solid 1, 4g of triethylamine, 0.5g of metal complex, and 3.7g of 85% phosphoric acid solution, mix them, add deionized water, stir at room temperature for 4h, crystallize at 210℃ for 2h, crystallize at 180℃ for 10h, filter, dry, and roast to obtain the denitrification catalyst. The XRD characterization of the catalyst is as follows Figure 1 As shown, a typical CHA structure molecular sieve is presented, with characteristic peaks of SAPO-34 at 2θ = 9.5° (101), 12.8° (110), 16° (021), 20.5° (211), 26° (220) and 31° (401). The NH3-SCR performance evaluation results are shown in Figure 2 As shown, when the reaction temperature is increased to 300°C, the NO conversion rate is 99.33%, showing good denitrification performance.

[0048] Example 4

[0049] Weigh 25g of MTO waste catalyst, mix it with 15g of ammonium sulfate, heat it to 300℃ at 5℃ / min, roast it for 4h, then heat it to 800℃ at 15℃ / min, roast it for 6h, add water to the obtained solid mixture, stir, filter, and dry to obtain solid 1. Mix 0.2g of copper sulfate, 0.05g of cerium nitrate, and 0.3g of tetraethylenepentamine and stir until they are completely dissolved to form an active metal complex for use. Take 10g of solid 1, 4g of triethylamine, 0.53g of metal complex, and 3.2g of 85% phosphoric acid solution, mix them, add deionized water, stir at room temperature for 4h, crystallize at 210℃ for 2h, crystallize at 180℃ for 10h, filter, dry, and roast to obtain the denitrification catalyst. The XRD characterization of the catalyst is as follows Figure 1 As shown, a typical CHA structure molecular sieve is presented, with characteristic peaks of SAPO-34 at 2θ = 9.5° (101), 12.8° (110), 16° (021), 20.5° (211), 26° (220) and 31° (401). The NH3-SCR performance evaluation results are shown in Figure 2 As shown, when the reaction temperature is increased to 300°C, the NO conversion rate is 98.1%, showing good denitrification performance.

[0050] Example 5

[0051] Weigh 15g of MTO waste catalyst, mix it with 10g of ammonium sulfate, heat it to 300℃ at 5℃ / min, roast it for 4h, then heat it to 800℃ at 15℃ / min, roast it for 6h, add water to the obtained solid mixture, stir, filter, and dry to obtain solid 1. Mix 0.2g of copper sulfate, 0.05g of manganese nitrate, and 0.3g of tetraethylenepentamine and stir until they are completely dissolved to form an active metal complex for use. Take 10g of solid 1, 4g of triethylamine, 0.51g of metal complex, and 3.5g of 85% phosphoric acid solution, mix them, add deionized water, stir at room temperature for 4h, crystallize at 210℃ for 2h, crystallize at 180℃ for 10h, filter, dry, and roast to obtain the denitrification catalyst. The XRD characterization of the catalyst is as follows Figure 1 As shown, a typical CHA structure molecular sieve is presented, with characteristic peaks of SAPO-34 at 2θ = 9.5° (101), 12.8° (110), 16° (021), 20.5° (211), 26° (220) and 31° (401). The NH3-SCR performance evaluation results are shown in Figure 2 As shown, when the reaction temperature is increased to 300°C, the NO conversion rate is 88.4%, showing good denitrification performance.

[0052] Comparative Example 1

[0053] This comparative example provides a Cu-Mn-SAPO-34 denitration catalyst prepared by an equal volume impregnation method using a purchased commercial SAPO-34 molecular sieve as a carrier. 0.2g of copper sulfate and 0.05g of manganese nitrate were weighed and dissolved in 4g of deionized water to form a solution 1. 10g of commercial SAPO-34 molecular sieve was immersed in the solution 1 for 24h, then dried at 110℃ and calcined in a muffle furnace at 550℃ for 4h to obtain a catalyst. The NH3-SCR performance evaluation results are shown in Figure 1. Figure 2 As shown, when the reaction temperature was increased to 300°C, the NO conversion rate was 84.09%.

Claims

1. A method for preparing a denitration catalyst by synthesizing MTO waste agent, characterized in that: The steps include: Step 1: Mix the MTO waste agent and ammonium salt, roast, add water, stir, filter, and dry to obtain solid 1; Step 2: The solid 1 is mixed with a template, an active metal complex, and a phosphorus source to prepare an initial gel, and then subjected to a step of hydrothermal crystallization, filtration, drying, and calcination to obtain a Cu / X-SAPO-34 denitration catalyst.

2. The method for preparing a denitration catalyst synthesized from MTO waste agent according to claim 1, characterized in that: The Cu / X-SAPO-34 denitration catalyst is a small-grain Cu / X-SAPO-34 denitration catalyst with a size of 200nm-500nm.

3. The method for preparing a denitration catalyst synthesized from MTO waste agent according to claim 1, characterized in that: In step 1, the ammonium salt is at least one of ammonium chloride, ammonium sulfate, ammonium bisulfate, ammonium carbonate and ammonium fluoride.

4. The method for preparing a denitration catalyst synthesized from MTO waste agent according to claim 1, characterized in that: In the step 1, the mass ratio of the MTO waste agent to the ammonium salt is 1:(0.1-10).

5. The method for preparing a denitration catalyst synthesized from MTO waste agent according to claim 1, characterized in that: The calcination in step 1 is a two-stage calcination, the first stage calcination temperature is 300°C to 450°C, the heating rate is 3 to 8°C / min, and the calcination time is 1 to 4h; The second stage of calcination temperature is 600℃~800℃, the heating rate is 10~15℃ / min, and the calcination time is 2~6h; During the filtration in step 1, the solution temperature should be maintained at 60° C. to 90° C. for hot filtration.

6. The method for preparing a denitration catalyst synthesized from MTO waste agent according to claim 1, characterized in that: In the step 2, the mass ratio of the solid 1, the template, the active metal complex and the phosphorus source is 1: (0.05-0.5): (0.01-0.1): (0.1-0.5).

7. The method for preparing a denitration catalyst synthesized from MTO waste agent according to claim 1, characterized in that: In step 2, the template agent is at least one of triethylamine, tetraethylammonium hydroxide, hexadecyltrimethylammonium bromide and morpholine; In step 2, the phosphorus source is at least one of phosphoric acid and phosphorous acid; In step 2, the active metal complex is prepared by mixing and stirring an active metal copper source, a manganese source / cerium source, and a complex; The copper active metal source is a soluble copper salt, selected from at least one of copper nitrate, copper acetate and copper sulfate; The manganese source is a soluble manganese salt, selected from at least one of manganese sulfate, manganese acetate and manganese nitrate; The cerium source is a soluble copper salt, selected from at least one of cerium nitrate and cerium chloride; The complexing agent is selected from at least one of diethylenetriamine, tetraethylenepentamine and pentaethylenehexamine; The molar ratio of the active metal copper source, manganese source / cerium source and complex is 1:(0.01-1):(0.5-2).

8. The method for preparing a denitration catalyst synthesized from MTO waste agent according to claim 1, characterized in that: The hydrothermal crystallization in step 2 is a two-stage crystallization method, wherein the first stage is crystallization at 200-220° C. for 2-4 hours, and the second stage is crystallization at 160-180° C. for 10-20 hours.

9. The method for preparing a denitration catalyst synthesized from MTO waste agent according to claim 1, characterized in that: In step 2, a Buchner funnel is used for filtration, and the filtrate is rinsed with deionized water until the pH value of the filtrate is about 7.

10. The Cu / X-SAPO-34 denitration catalyst prepared by the method for preparing a denitration catalyst synthesized from MTO waste agent according to any one of claims 1 to 9, characterized in that: The Cu / X-SAPO-34 denitration catalyst is used for fixed source denitration; During the denitrification reaction, the acidic sites of B acid and L acid on the surface of Cu / X-SAPO-34 molecular sieve catalyst will adsorb some ammonia molecules in the introduced ammonia gas, and then the active substances on the catalyst surface will react with NO in the gas phase to form nitrate or nitrite, and react chemically with the ammonia species adsorbed on the catalyst surface to form intermediate species of ammonium nitrate or ammonium nitrite. The intermediate ammonium salt is catalytically reduced and decomposed into N2 and H2O and a small amount of NO2 by B acid provided on the catalyst surface. The generated NO2 directly undergoes self-disproportionation reaction to generate nitrite on the catalyst surface to participate in the SCR reaction.

Images