A method for preparing a manganese-based low-temperature SCR catalyst from spent FCC catalyst

Abstract

The application discloses a method for preparing a manganese-based low-temperature SCR catalyst from waste FCC catalyst, and comprises the following steps: using a waste fluidized bed catalytic cracking catalyst as a carrier, carrying out an equal-volume impregnation treatment on the carrier by using a divalent manganese salt precursor solution, then adding a KMnO4 solution drop by drop to carry out a reaction, washing and centrifuging after the reaction is completed to obtain a filter cake, and drying the filter cake to obtain the catalyst. The divalent manganese salt is one of Mn(NO3)2, Mn(AC)2, MnCl2 and MnSO4. Compared with a traditional preparation method of a supported catalyst, the preparation method has the advantages of simple process, no secondary pollutant emission, energy saving in the process, adjustable and controllable structure, good low-temperature SCR denitration activity, wide active temperature window and the like.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of environmental protection, and particularly relates to a method for preparing a manganese-based low-temperature SCR catalyst from waste FCC catalyst. BACKGROUND

[0002] At present, fluid catalytic cracking (FCC) is a main heavy oil lightening method in a refining process, is a core device for determining a product scheme of a refinery, and thus occupies an important position in the refining process. However, after being used for a period of time, the FCC catalyst is abandoned due to poisoning and deactivation of heavy metals (Ni, V, Fe, etc.), particle size refinement, and carbon deposition. Through research, it is known that researchers at home and abroad have methods for treating SFCCC, such as burying, physical regeneration, chemical regeneration, balance agent reuse, refined oil products, recycling of rare earth and heavy metals, and the like. These methods all have corresponding bottleneck problems. At present, the mainstream way of treating accumulated SFCCC in industry is to treat it as solid waste and dispose of it in a chemical landfill, thereby causing environmental hazards, or to supply it to the cement industry. However, in the future, many factors will restrict the development of this method, especially the economic cost of land use rights and the environmental hazards caused by the infiltration of landfill leachate into the soil. Then, how to resourcefully utilize a large amount of SFCCC produced annually becomes a problem to be solved. Nitrogen oxide (NO x ) as a main air pollutant, if not properly treated, can cause a series of environmental problems such as haze, acid rain, greenhouse effect, and the like, and seriously threatens human health and plant growth. The SCR technology has become the most effective method for treating NO xOne of the emission reduction technologies. At present, the selective catalytic reduction technology (NH3-SCR) using ammonia as the reducing agent is considered as the most effective technology for removing nitrogen oxides in stationary sources, and the catalyst is the core element of the technology. Among many catalysts, the V2O5-WO3 / TiO2 catalyst has become the most mature commercial application product due to its stable and reliable catalytic denitration performance. However, it is easy to be poisoned by sulfur in flue gas at low temperature, and is generally used at a flue gas temperature of 300-400 ℃, belonging to a medium-high temperature catalyst, and having a narrow operating temperature window. Although the catalyst has been widely applied in the field of flue gas denitration in coal-fired power plants with high exhaust gas temperature, it is difficult to be directly applied to the control of nitrogen oxide emission in low-temperature flue gas in other industrial fields. Therefore, the SCR catalyst capable of being directly used in the medium-low temperature zone has wide demand and application prospect. The development and application of low-temperature SCR denitration catalysts have become a hot spot in the field of flue gas denitration technology in non-electricity industry in recent years, including improved vanadium-based catalysts, manganese-based catalysts, iron-based catalysts and rare earth metal composite catalyst materials, all of which have successful application cases. At the same time, the development of low-temperature SCR denitration process suitable for low-temperature SCR catalysts is also gradually mature and diversified, which provides reliable technical feasibility for the large-area engineering of low-temperature SCR flue gas denitration. Among the above low-temperature SCR denitration catalysts, the preparation and application technology of supported manganese-based catalysts develop most fully. The preparation methods of supported manganese-based catalysts are also becoming diversified. The traditional methods such as equal-volume impregnation-calcination and liquid deposition-calcination based on the thermal decomposition of manganese salt precursors to prepare manganese-loaded catalysts show problems such as high energy consumption, secondary pollution emission and different degrees of sintering of catalysts leading to low activity. SUMMARY

[0003] The present application aims to provide a method for preparing a manganese-based low-temperature SCR catalyst from waste FCC catalyst, which can not only avoid the environmental hazard risk of heavy metal component leaching pollution of water body or soil caused by the conventional landfill treatment SFCCC method, but also can "turn waste into treasure", prepare an industrial flue gas low-temperature SCR denitration catalyst with excellent performance, and realize the harmless high-value comprehensive utilization of the hazardous waste.

[0004] In one aspect of the present application, a method for preparing a manganese-based low-temperature SCR catalyst from waste FCC catalyst is provided. According to the embodiments of the present application, the method comprises the following steps: using a waste fluidized bed catalytic cracking catalyst as a carrier, performing equal-volume impregnation treatment on the carrier with a divalent manganese salt precursor solution, then adding a KMnO4 solution dropwise for reaction, washing and centrifuging to obtain a filter cake after the reaction is completed, and drying the filter cake to obtain the catalyst.

[0005] In addition, the method for preparing a manganese-based low-temperature SCR catalyst from waste FCC catalyst according to the above-mentioned embodiments of the application can further have the following additional technical features.

[0006] In some embodiments of the application, the divalent manganese salt is one of Mn(NO3)2, Mn(AC)2, MnCl2, and MnSO4.

[0007] In some embodiments of the application, the method specifically comprises the following steps:

[0008] (1) Coarsely purifying the waste fluidized bed catalytic cracking catalyst, and taking the powder with a particle size of 200 mesh or more for use;

[0009] (2) Mixing and impregnating the coarsely purified waste fluidized bed catalytic cracking catalyst powder with a divalent manganese salt precursor solution at a volume ratio of 1:0.5, fully stirring for 30-60 min, and then standing for 24 h;

[0010] (3) Adding a potassium permanganate solution to the solution after stirring in step (2), fully stirring for 30-60 min at room temperature and at a pH of 4.5-5.5, and then washing and suction-filtering with deionized water for 3-5 times;

[0011] (4) Drying the product after suction-filtering to obtain a dried catalyst product;

[0012] (5) Grinding and sieving the dried catalyst product to obtain the manganese-based low-temperature SCR catalyst.

[0013] In some embodiments of the application, in step (1), the coarsely purifying is performed by using a sample divider for sieving.

[0014] In some embodiments of the application, in step (3), the molar ratio of the divalent manganese salt precursor to the potassium permanganate is 3:2.

[0015] In some embodiments of the application, in step (4), the drying temperature is 100-115°C, and the drying time is 10-15 h.

[0016] In some embodiments of the application, in step (5), the grinding and sieving is to 20-40 mesh.

[0017] Compared with the prior art, the application has the following beneficial effects:

[0018] (1) The application uses a waste fluidized bed catalytic cracking catalyst (SFCCC) as a carrier, and uses an in-situ chemical deposition method to load an active component MnO x on the SFCCC to prepare a Mn-based catalyst with low-temperature SCR catalytic denitration activity, thereby improving the denitration activity, selectivity, stability, and sulfur poisoning resistance of the manganese-based low-temperature SCR denitration catalyst.

[0019] (2) The preparation method has significant inhibitory effect on the leaching behavior of heavy metal components such as Ni, V and Fe in the raw carrier (SFCCC), can play the synergistic effect of the original deposited heavy metal elements on the carrier and MnO x , so that the harmful metal elements deposited in the SFCCC are harmlessly fixed, and the fixation rate is higher than 90%, thereby reducing the environmental hazards caused by the loss of heavy metal elements in storage, transportation and use.

[0020] (3) Compared with the equal-volume impregnation-calcination method, the liquid-phase precipitation-calcination method and the sol-gel-calcination method, the manganese-based SCR denitration catalyst prepared by the present application through the special disproportionation reaction between high-valence manganese and low-valence manganese at room temperature on the surface of the carrier SFCCC to generate nanoscale and highly dispersed manganese oxide active components in one step, and then through in-situ chemical deposition has more excellent denitration activity and a wider temperature window, and the structure and chemical properties of the catalyst can be adjusted and controlled by changing the reactant ratio, the loading amount of manganese oxide and the calcination temperature. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 The curve of the conversion rate of NO with respect to the reaction temperature of the catalyst prepared in Example 1 and Comparative Examples 1-3;

[0022] Figure 2 The curve of the selectivity of N2 with respect to the reaction temperature of the catalyst prepared in Example 1 and Comparative Example 2;

[0023] Figure 3 The curve of the conversion rate of NO with respect to the reaction time of the catalyst prepared in Example 1 and Comparative Example 2;

[0024] Figure 4 The SEM images of the catalyst prepared in Example 1 and Comparative Examples 1-2, wherein, Figures (A1)-(A3) are the images of Comparative Example 1, wherein (A1) is the morphology image of Comparative Example 1 at 400 nm, (A2) and (A3) are the morphology image and the corresponding Mn element mapping image of Comparative Example 1 at 200 nm, respectively; Figures (B1)-(B3) are the images of Example 1, wherein (B1) is the morphology image of Example 1 at 400 nm, (B2) and (B3) are the morphology image and the corresponding Mn element mapping image of Example 1 at 200 nm, respectively; Figures (C1)-(C3) are the images of Comparative Example 2, wherein (C1) is the morphology image of Example 1 at 400 nm, (C2) and (C3) are the morphology image and the corresponding Mn element mapping image of Example 1 at 200 nm, respectively;

[0025] Figure 5The leaching rate curves of heavy metal elements Ni and V in the preparation of catalysts for Example 1 and Comparative Example 2 are shown in the following table. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the protection scope of the present application.

[0027] Example 1

[0028] A method for preparing a manganese-based low-temperature SCR catalyst from waste FCC catalyst, comprising the following steps:

[0029] 1. 2 g of SFCCC powder with a particle size of 200 mesh after coarse purification and sieving was mixed with a first precursor solution of manganese acetate at a volume ratio of 1:0.5 for impregnation, and then stirred fully for 30 min and left to stand for 24 h;

[0030] 2. Potassium permanganate solution was added to the impregnated product, and the molar ratio of manganese acetate to potassium permanganate was 3:2, then stirred fully for 30 min and left to stand for 24 h, and then washed with deionized water and filtered by suction for 3 times;

[0031] 3. The filtered product was placed in a 110°C blast drying oven for drying for 12 h, to obtain a dried catalyst product;

[0032] 4. The dried catalyst product was ground and sieved to 40 mesh, to obtain a catalyst Mn8 / SFCCC-SP, wherein 8 represents the mass fraction (wt%) of Mn element in the catalyst, and SP represents in-situ chemical deposition method.

[0033] Example 2

[0034] A method for preparing a manganese-based low-temperature SCR catalyst from waste FCC catalyst, comprising the following steps:

[0035] 1. 2 g of SFCCC powder with a particle size of 200 mesh after coarse purification and sieving was mixed with a first precursor solution of manganese nitrate at a volume ratio of 1:0.5 for impregnation, and then stirred fully for 30 min and left to stand for 24 h;

[0036] 2. Potassium permanganate solution was added to the impregnated product, and the molar ratio of manganese nitrate to potassium permanganate was 3:2, then stirred fully for 30 min and left to stand for 24 h, and then washed with deionized water and filtered by suction for 3 times;

[0037] 3. The filtered product was placed in a 110°C blast drying oven for drying for 12 h, to obtain a dried catalyst product;

[0038] 4. Grinding and sieving the dried catalyst product to 40 mesh, to obtain the catalyst Mn8 / SFCCC-SP, 8 represents the mass fraction of Mn element in the catalyst (wt%), and SP represents in-situ chemical deposition method.

[0039] Example 3

[0040] A method for preparing a manganese-based low-temperature SCR catalyst from waste FCC catalyst, comprising the following steps:

[0041] 1. 2 g of SFCCC powder with a particle size of 200 mesh after rough purification by sample separation screen was mixed with a first precursor solution manganese chloride at a volume ratio of 1:0.5 for impregnation, and after sufficient stirring for 30 min, it was left to stand for 24 h;

[0042] 2. Potassium permanganate solution was added to the impregnated product, and the molar ratio of manganese sulfate to potassium permanganate was 3:2, and after sufficient stirring for 30 min, it was left to stand for 24 h, and then it was washed and filtered with deionized water for 3 times;

[0043] 3. The filtered product was placed in a 110°C air drying oven for drying for 12 h, to obtain the dried catalyst product;

[0044] 4. Grinding and sieving the dried catalyst product to 40 mesh, to obtain the catalyst Mn8 / SFCCC-SP, 8 represents the mass fraction of Mn element in the catalyst (wt%), and SP represents in-situ chemical deposition method.

[0045] Example 4

[0046] A method for preparing a manganese-based low-temperature SCR catalyst from waste FCC catalyst, comprising the following steps:

[0047] 1. 2 g of SFCCC powder with a particle size of 200 mesh after rough purification by sample separation screen was mixed with a first precursor solution manganese sulfate at a volume ratio of 1:0.5 for impregnation, and after sufficient stirring for 30 min, it was left to stand for 24 h;

[0048] 2. Potassium permanganate solution was added to the impregnated product, and the molar ratio of manganese sulfate to potassium permanganate was 3:2, and after sufficient stirring for 30 min, it was left to stand for 24 h, and then it was washed and filtered with deionized water for 3 times;

[0049] 3. The filtered product was placed in a 110°C air drying oven for drying for 12 h, to obtain the dried catalyst product;

[0050] 4. Grinding and sieving the dried catalyst product to 40 mesh, to obtain the catalyst Mn8 / SFCCC-SP, 8 represents the mass fraction of Mn element in the catalyst (wt%), and SP represents in-situ chemical deposition method.

[0051] Comparative Example 1

[0052] Carrier SFCCC: SFCCC powder was sieved to 200 mesh particle size by a sample sieve.

[0053] Comparative Example 2

[0054] A method for preparing catalyst MnOx / SFCCC-IP from waste FCC catalyst, comprising the following steps:

[0055] 1. Sieving SFCCC powder to 200 mesh particle size by a sample sieve;

[0056] 2. Dissolving the first precursor manganese acetate into deionized water, and stirring for 6 hours;

[0057] 3. Mixing 2 g of SFCCC powder with the first precursor solution manganese acetate at a volume ratio of 1:0.5, and stirring for 6 hours;

[0058] 4. Adjusting the PH value of the solution in step 3 to 5.0, and continuing to stir for 6 hours, and then immersing the product after stirring into room temperature for 24 hours;

[0059] 5. Placing the product after immersion in step 4 into a 110°C air drying oven for drying for 12 hours, to obtain a dried catalyst product;

[0060] 6. Grinding and sieving the dried catalyst product to 40 mesh, and then placing it into a tube furnace, and then passing oxygen atmosphere, and then heating at a rate of 10°C / min, and then calcining at 300°C for 3 hours, to obtain catalyst Mn8 / SFCCC-IP, wherein 8 represents the mass fraction (wt%) of Mn element in the catalyst, and IP represents an equal-volume impregnation-calcination method.

[0061] Comparative Example 3

[0062] A method for preparing catalyst MnOx / SFCCC-CP from waste FCC catalyst, comprising the following steps:

[0063] 1. Sieving SFCCC powder to 200 mesh particle size by a sample sieve;

[0064] 2. Mixing 2 g of SFCCC powder with the first precursor solution manganese nitrate at a volume ratio of 1:1, and stirring for 6 hours, and then immersing into room temperature for 24 hours;

[0065] 3. Adding the second precursor solution ammonium carbonate into the product after immersion, adjusting the PH value, and stirring for 24 hours, to make it fully precipitate;

[0066] 4. Washing the precipitate obtained in step 3 with deionized water, and stopping washing and suction filtration when the PH value of the filtrate approaches neutral.

[0067] 5. The product obtained in step 4 was dried in a 110℃ forced air drying oven for 12h to obtain the dried catalyst product;

[0068] 6. The dried catalyst product obtained in step 5 was ground and sieved to 40 mesh, and then placed in a tube furnace, and calcined in an oxygen atmosphere at a heating rate of 10℃ / min at 300℃ for 3h to obtain the catalyst Mn8 / SFCCC-CP, 8 represents the mass fraction (wt%) of Mn element in the catalyst, and CP represents the liquid phase precipitation-calcination method.

[0069] The samples obtained in Example 1 and Comparative Examples 1-3 were subjected to denitration performance testing, and the testing method was as follows:

[0070] The NH3-SCR denitration activity of the SCR denitration catalyst was evaluated in an atmospheric fixed-bed quartz flow reactor with an inner diameter of 15mm and a height of 80mm, and the heating was controlled by an energy-saving experimental resistance furnace system. The reaction conditions were as follows: 1000mg·m - 3 NO, 1000mg·m -3 NH3, 3% O2, 350mL·min -1 N2 (balance gas) was mixed. The reaction space velocity was 52,500h -1 , and the reaction temperature was 100-300℃. A German testo 340 flue gas analyzer was used to measure the reactant and product gas.

[0071] The denitration performance of the catalyst was evaluated by the NO conversion rate (X NO ), and the calculation method was as follows:

[0072]

[0073] In the formula, [NO] in , [NO] out are the concentrations of the NO reactant and product gas, respectively.

[0074] The curve of the NO conversion rate of the catalyst product prepared in the above example with respect to the reaction temperature is shown in Figure 1 , and it can be known from Figure 1 that:

[0075] (1) The manganese-based low-temperature SCR catalyst prepared by the in-situ chemical deposition method in Example 1 has better overall activity than the equal-volume impregnation-calcination method (IP) and the liquid phase precipitation-calcination method (CP), and the conversion rate of the catalyst prepared by the in-situ chemical deposition method for catalyzing NO-SCR is almost close to 100% at a space velocity of >42000h -1 and a temperature range of 150-275℃.

[0076] (2) The SFCCC catalyst support for SCR denitration in Comparative Example 1 had no denitration activity.

[0077] The N2 selectivity of the catalyst products prepared in Example 1 and Comparative Example 2 as a function of reaction temperature are shown in the following curves. Figure 3 As shown.

[0078] Within the temperature range of 100–250°C, Comparative Example 2 exhibited a selectivity of >95% for N2. When the reaction temperature was further increased to 275 or 300°C, the selectivity for N2 decreased by 89.4% and 74.2%, respectively. Within the temperature range of 100–300°C, Example 1 showed a selectivity of 96.0% for N2. Therefore, Example 1 demonstrated superior N2 selectivity.

[0079] The NO conversion rate of the catalysts prepared in Example 1 and Comparative Example 2 as a function of reaction time is shown in the following curves. Figure 4 As shown.

[0080] At T = 200℃, GHSV = 52500h -1 Under the operating conditions, an initial stability experiment was conducted with a continuous reaction time of 100 h, and the results are as follows: Figure 4 As shown, the NO conversion rate of Example 1 was close to 100% throughout the 100-hour test period, indicating good stability. The NO conversion rate of Comparative Example 2 remained above 95% for 70 hours, but slightly decreased to 93.0% at 100 hours. The results indicate that the catalyst product prepared in Example 1 has better stability than that prepared in Comparative Example 2.

[0081] SEM data of the products prepared in Example 1 and Comparative Examples 1-3 are as follows: Figure 4 As shown, in the low-load manganese-based catalyst prepared by in-situ chemical deposition in Example 1, the generated nano-sized MnO x The particles can be well dispersed on the support SFCCC, which is one of the reasons why the catalyst has high activity at low temperatures and a wide temperature window.

[0082] The BET data of the products prepared in Example 1 and Comparative Examples 1-3 are shown in Table 1. Compared with the equal-volume impregnation-calcination method in Comparative Example 2 and the liquid-phase precipitation-calcination method in Comparative Example 3, the catalyst prepared by in-situ chemical deposition in Example 1 has a significantly increased specific surface area, a significantly improved pore structure, and a tunable and controllable surface chemical environment. Therefore, it has broad application prospects in the field of catalysis. Figure 1 The activity test data are consistent.

[0083] Table 1. BET data for Example 1 and Comparative Examples 1-3

[0084] Sample name Specific surface area (m 2 / g) Pore volume (cm 3 / g) Pore size Dp / nm Example 1 138 0.16 4.57 Comparative Example 1 95 0.10 4.02 Comparative Example 2 82 0.01 4.76 Comparative Example 3 100 0.14 5.54

[0085] The XRF data of the product prepared in Example 1 above and that of Comparative Example 1 are shown in Table 2, from which it can be found that the MnO x A large amount of heavy metals are loaded on SFCCC. The manganese-based SCR denitration catalyst is prepared by a special process of in-situ chemical deposition, and nano-sized active species can be obtained on the carrier without calcination. The method not only has mild conditions, but also can significantly inhibit the leaching behavior of heavy metal components such as Ni, V and Fe in the above raw carrier (SFCCC), thereby realizing harmless fixation of the above harmful substances and eliminating environmental pollution hazards in the later use or disposal process.

[0086] Table 2 XRF data table of Example 1 and Comparative Example 1 (unit: wt%)

[0087] Sample Al2O3 SiO2 CO2 Fe2O3 La2O3 NiO [P2O5] MnO [V2O5] Example 1 40.99 28.57 4.32 1.69 1.63 1.37 0.67 18.26 0.59 Comparative Example 1 48.07 37.88 4.44 2.03 1.99 1.31 0.82 0.06 0.70

[0088] The element content data of the products prepared in Example 1 and Comparative Examples 1-3 are shown in Table 3, and the leaching rate data of heavy metal elements Ni and V during the catalyst preparation process are shown in Table 4. Figure 5 As can be seen from Table 4, after SFCCC is loaded with MnOx to prepare a manganese-based denitration catalyst by in-situ chemical deposition method, the contents of heavy metal elements Ni and V contained in SFCCC all reach the national emission standard (GB5085.3-2007, GB26452-2011), which indicates that the in-situ chemical deposition preparation process is environmentally friendly and has no secondary pollution.

[0089] Table 3 Element content table (ICP-MS) of Example 1 and Comparative Examples 1-2 (unit: ug / g)

[0090]

[0091]

[0092] The above is only an example and description of the structure of the present application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace, as long as they do not deviate from the structure of the present application or exceed the scope defined by the present claims, which shall belong to the protection scope of the present application.

Claims

1. A method for preparing a manganese-based low-temperature SCR catalyst from waste FCC catalyst, characterized in that, Includes the following steps: (1) The waste fluidized bed catalytic cracking catalyst was crudely purified, and powder with a particle size of 200 mesh or larger was used for later use; (2) The waste fluidized bed catalytic cracking catalyst powder after crude purification is mixed with the divalent manganese salt precursor solution at a volume ratio of 1:0.5 and impregnated. After stirring thoroughly for 30-60 minutes, it is left to stand for 24 hours. (3) Add potassium permanganate solution to the solution after stirring in step (2), stir thoroughly for 30-60 minutes at room temperature and pH = 4.5-5.5, and then wash and filter with deionized water 3-5 times. (4) The filtered product is dried to obtain the dried catalyst product. (5) Grind and sieve the dried catalyst product to obtain the manganese-based low-temperature SCR catalyst.

2. The method for preparing a manganese-based low-temperature SCR catalyst from waste FCC catalyst according to claim 1, characterized in that: In step (2), the divalent manganese salt is one of Mn(NO3)2, Mn(AC)2, MnCl2, and MnSO4.

3. The method for preparing a manganese-based low-temperature SCR catalyst from waste FCC catalyst according to claim 1, characterized in that: In step (1), the crude purification is carried out by sieving using a sieve.

4. The method for preparing a manganese-based low-temperature SCR catalyst from waste FCC catalyst according to claim 1, characterized in that: In step (3), the molar ratio of the divalent manganese salt precursor to potassium permanganate is 3:

2.

5. The method for preparing a manganese-based low-temperature SCR catalyst from waste FCC catalyst according to claim 1, characterized in that: In step (4), the drying temperature is 100-115℃ and the drying time is 10-15h.

6. The method for preparing a manganese-based low-temperature SCR catalyst from waste FCC catalyst according to claim 1, characterized in that: In step (5), the grinding and sieving are performed to a mesh size of 20-40.

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