Anti-sintering catalyst, its preparation method and application

Abstract

The present application relates to the technical field of catalyst preparation, in particular to a sintering-resistant catalyst and a preparation method and application thereof. A Cu-MOF material is used as a raw material precursor, and a catalyst for propylene aldehyde oxidation to prepare propylene acid is prepared by using the organic framework support of the MOF. The catalyst has excellent catalytic activity, high propylene acid selectivity and yield, and also has high sintering resistance and long service life. In addition, the high dispersion of Cu elements in the catalyst is conducive to improving the selectivity of propylene acid.

Description

Technical Field

[0001] This invention relates to the field of catalyst preparation technology, and more specifically to an anti-sintering catalyst, its preparation method, and its application. Background Technology

[0002] Acrylic acid is a crucial raw material for the synthesis of acrylate chemicals, widely used in coatings, textiles, adhesives, and other fields. The efficiency and stability of its production process largely depend on catalyst performance. Currently, molybdenum (Mo)-vanadium (V) oxide is commonly used as the basic catalyst system in industrial applications, with various additives (such as niobium (Nb), tin (Sn), tungsten (W), antimony (Sb), copper (Cu), and nickel (Ni)) introduced to improve catalytic performance. These additives are incorporated through co-precipitation or compounding, followed by molding and calcination to form the final catalyst. For example, Chinese invention patent CN111659408A discloses a molybdenum-vanadium-based catalyst containing Ni and Cu, which enhances catalytic activity through multi-element synergistic effects. Furthermore, controlling the type of additives can specifically optimize catalytic performance. For instance, introducing elements with high electronegativity (such as W and Sb) helps regulate surface acidity and enhance reactant adsorption; while adding elements with redox properties (such as Cu, Ce, and Fe) can promote lattice oxygen migration, improve acrylic acid selectivity, and suppress side reactions. The dissertation, "Study and Pilot-Scale Experiment of Catalyst for Acrolein Oxidation to Acrylic Acid," reveals that the introduction of the auxiliary agent Cu into the catalyst system has the following improving characteristics: 1. It generates a CuMoO4 phase, increases surface acidic sites, and enhances acrolein adsorption and activation; 2. It improves the redox cycle and promotes V... 5+ 3. Regeneration improves overall activity and acrylic acid selectivity; 4. Optimizes surface electron distribution, suppresses side reactions, and significantly improves acrylic acid yield.

[0003] However, in actual industrial applications, the reaction temperature of the catalyst reaches over 260℃, with the hot spot temperature reaching as high as 300℃. Furthermore, as the catalyst is used for a longer period, the reaction temperature and hot spot temperature continuously increase in order to achieve high acrolein conversion and acrylic acid yield, which also increases the temperature burden on the catalyst. In addition, in the later stages of catalyst operation, frequent coking and regeneration (around 310℃) also subject the catalyst to high temperatures, causing irreversible effects: 1. At high temperatures, Cu ions migrate from the bulk phase to the surface, agglomerating and segregating, thereby destroying the original active phase and weakening the synergistic effect; 2. At high temperatures, Cu readily reacts with MoO3 to form Cu2MoO5 and other phases with low activity and poor selectivity for acrolein oxidation, resulting in reduced catalytic activity; 3. It accelerates the growth of Mo-V active phase grains, reducing the catalyst's specific surface area and causing catalyst sintering.

[0004] Improving the sintering resistance of catalysts, especially inhibiting the migration and aggregation of Cu ions, is one of the means to ensure the high-temperature tolerance of catalysts and extend their lifespan. Metal-organic frameworks (MOFs) are a class of crystalline porous materials formed by the self-assembly of metal ions and organic ligands, possessing advantages such as tunable structure, high specific surface area, and good thermal stability. Among them, Cu-MOFs (Cu-BTC, Cu-BDC, Cu-MOF-74, etc.) are abundant, have convenient synthesis methods, and are an important member of the metal-organic framework materials. Due to the supporting role of the organic framework, the metal elements in these materials usually exhibit a monodisperse form after pyrolysis, which is one of the important strategies for synthesizing highly dispersed, low-agglomeration metal composite catalysts.

[0005] Therefore, it is of practical value to provide a catalyst with high Cu element dispersion, strong anti-sintering properties of active centers, and long lifespan. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing catalysts for the oxidation of acrolein to acrylic acid, and to provide a catalyst for the oxidation of acrolein to acrylic acid using Cu-MOFs as a precursor and leveraging the organic framework support of MOFs. This catalyst exhibits excellent catalytic activity, high selectivity and yield for acrylic acid, while also possessing high resistance to sintering and a long lifespan. Furthermore, the high dispersion of Cu in the catalyst is beneficial for improving the selectivity for acrylic acid.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing an anti-sintering catalyst, comprising the following steps:

[0009] (1) Cu-MOFs were subjected to preliminary pyrolysis to obtain Cu precursors;

[0010] (2) Dissolve water-soluble metal salts containing Mo, V, and W in water to obtain a mixed solution;

[0011] (3) Add dispersant, Cu precursor and Sb salt to the mixed solution in sequence, and react continuously at 85~95℃ for 4~6 hours to obtain catalyst slurry;

[0012] (4) After the reaction is complete, the catalyst slurry is spray-granulated to obtain a solid precursor;

[0013] (5) The solid precursor is calcined in a tube furnace under an air atmosphere to obtain the catalyst.

[0014] In some preferred embodiments, the Cu-MOFs are one or more of Cu-BTC, Cu-BDC, and Cu-MOF-74.

[0015] In some preferred embodiments, the initial pyrolysis temperature is 150~260°C.

[0016] In some preferred embodiments, the raw material for Mo is selected from one or two of ammonium molybdate and ammonium paramolybdate; the raw material for V is selected from one or two of vanadium oxalate and ammonium metavanadate; and the raw material for W is selected from one or more of ammonium tungstate, ammonium paratungstate, and ammonium metatungstate.

[0017] In some preferred embodiments, the dispersing agent is selected from one or more of carboxymethyl cellulose, P123, F127, and polyethylene glycol; the raw material for Sb salt is selected from one or two of antimony acetate and antimony oxide.

[0018] In some preferred embodiments, P123 is a poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer.

[0019] In some preferred embodiments, F127 is poloxamer 407, a triblock copolymer composed of polyethylene glycol and polypropylene glycol, which is a nonionic surfactant.

[0020] In some preferred embodiments, the spray granulation processing conditions are: inlet temperature 120~180℃, outlet temperature 70~100℃.

[0021] In some preferred embodiments, the air feed rate of the tubular furnace is 20 mL / min, and the heating rate is 1~2℃ / min.

[0022] In some preferred embodiments, the calcination temperature is 300~400℃ and the time is 8~12 hours.

[0023] Secondly, the present invention provides an anti-sintering catalyst, obtained by the above preparation method, having the general formula Mo. 12 V a W b Cu c Sb d O x In the formula, a, b, c, and d represent the atomic ratios of each element, where a = 1~5, b = 0.5~2.5, c = 0.5~3, and d = 0~1.5. The amount of Cu-MOFs added is calculated based on the actual Cu element content.

[0024] Thirdly, the present invention provides an application of an anti-sintering catalyst for the catalytic oxidation of acrolein to prepare acrylic acid.

[0025] Compared with the prior art, the present invention has the following advantages:

[0026] 1. This invention uses Cu-MOFs as Cu raw material. By utilizing the highly ordered pore structure, large specific surface area, and organic framework support of MOFs, the Cu element in the prepared acrolein oxidation to acrylic acid catalyst exhibits a highly dispersed state, which gives the catalyst excellent anti-sintering ability and extends the catalyst service life.

[0027] 2. This invention demonstrates that the catalyst maintains excellent catalytic performance even after different high-temperature calcinations and multiple high-temperature calcinations, verifying its superior anti-sintering properties. This method extends the catalyst's lifespan and reduces the production cost of acrylic acid. Furthermore, the high dispersion of Cu in the catalyst is beneficial for improving the selectivity of acrylic acid. Attached Figure Description

[0028] Figure 1 The XRD pattern of Cu-BDC prepared in this invention;

[0029] Figure 2 The XRD pattern of Cu-BTC prepared in this invention;

[0030] Figure 3 The XRD pattern of Cu-MOF-74 prepared in this invention;

[0031] Figure 4 The XRD patterns of Example 1 of the present invention after calcination at different temperatures are shown.

[0032] Figure 5 The XRD patterns of Comparative Example 1 of this invention after calcination at different temperatures are shown below.

[0033] Figure 6 The images shown are scanning electron microscope (SEM) images and surface scan distribution maps of copper element after calcination at different temperatures in Example 1.

[0034] Figure 7 The images shown are scanning electron microscope (SEM) images and surface scan distribution maps of copper element after calcination at different temperatures, representing Comparative Example 1. Detailed Implementation

[0035] The present invention can be better understood through the following examples.

[0036] The MOF materials Cu-BDC, Cu-BTC, and Cu-MOF-74 in each embodiment were synthesized according to the methods described in the literature [Journal of Membrane Science, 2018, 549, 312-320; Materials Chemistry and Physics, 2018, 213, 343-351; Chemical Engineering and Processing - Process Intensification, 2024, 204, 109949.]. The specific methods are as follows:

[0037] Preparation of Cu-BDC materials

[0038] First, terephthalic acid (39.87 g, 0.24 mol) and triethylamine (60 mL) were dissolved in 800 mL of N,N-dimethylformamide (DMF) and stirred continuously at room temperature for 30 min to obtain solution A. Then, Cu(NO3)2⋅3H2O (70.06 g, 0.29 mol) was dissolved in 200 mL of DMF to obtain solution B. Solution B was slowly added dropwise to solution A, and the mixture was stirred at 80 °C for 6 hours until a precipitate formed. Finally, after centrifugation and washing with water, the resulting sample was placed in an oven and dried at 100 °C for 12 hours to obtain the MOF porous material Cu-BDC, which was stored at room temperature for later use. XRD is shown in [reference needed]. Figure 1 .

[0039] Preparation of Cu-BTC materials

[0040] First, Cu(NO3)3·3H2O (14.50 g, 0.06 mol) was dissolved in 200 mL of deionized water, and 1,3,5-benzenetricarboxylic acid (8.41 g, 0.04 mol) was dissolved in 200 mL of anhydrous ethanol. Then, the two solutions were repeatedly mixed at room temperature and transferred to a polytetrafluoroethylene-lined high-pressure reactor, where the reaction was carried out continuously at 120 °C for 24 h. After the reaction, the mixture was cooled, centrifuged (3000 rpm, 5 min), washed with alcohol, and a blue precipitate was obtained. Finally, the sample was placed in a vacuum drying oven and dried under vacuum at 60 °C for 12 h to obtain the MOF porous material Cu-BTC powder, which was stored at room temperature for later use. XRD is shown in [reference needed]. Figure 2 .

[0041] Preparation of Cu-MOF-74 materials

[0042] First, 2,5-dihydroxyterephthalic acid (1.98 g, 0.01 mol) was dissolved in 100 mL of methanol to obtain solution A, and Cu(OAc)₂·H₂O (3.99 g, 0.02 mol) was dissolved in 50 mL of methanol to obtain solution B. Then, solution A was slowly added dropwise to solution B over 30 minutes to obtain a mixed solution. After stirring continuously at room temperature for 20 hours, the mixture was centrifuged and washed with alcohol to obtain a solid powder. Finally, the powder was placed in an oven and dried overnight at 100 °C to obtain the MOF porous material Cu-MOF-74, which was stored at room temperature for later use. XRD is shown in [reference needed]. Figure 3 .

[0043] Example 1: Mo 12 V2W 1.8 Cu 1.2 Sb 0.8 Preparation of -BDC (STL-Cu 1.2 -BDC)

[0044] (1) First, 7.09 g of Cu-BDC was placed in a muffle furnace and heated to 200 °C for 5 h at a rate of 1.5 °C / min to obtain Cu precursor;

[0045] (2) Then, 55.0 g ammonium molybdate, 6.07 g ammonium metavanadate and 11.51 g ammonium tungstate were dissolved in 500 mL deionized water and stirred continuously at 60°C for 30 min to obtain a homogeneous solution.

[0046] (3) After that, 5 g of carboxymethyl cellulose was dissolved in the above solution to form a homogeneous solution. Then, the Cu precursor obtained in step (1) was dispersed into the system and stirred continuously for 2 h. Then, 6.21 g of antimony acetate was added and reacted continuously at 85°C for 5 h.

[0047] (4) After the reaction is complete, the above mixed solution is cooled to room temperature and spray dried. The inlet air temperature is controlled at 150°C, and the feeding speed is adjusted to keep the outlet temperature at 90°C. The product in the cyclone separator is collected.

[0048] (5) Finally, in a tube furnace, the temperature was increased to 390°C at an air feed rate of 200 mL / min and a rate of 1.5°C / min, and calcined for 8 hours to obtain catalyst powder, denoted as STL-Cu. 1.2 -BDC.

[0049] Example 2: Mo 12 V2W 1.8 Cu 0.5 Sb 0.8 Preparation of -BDC (STL-Cu 0.5 -BDC)

[0050] (1) First, 2.96 g of Cu-BDC was placed in a muffle furnace and heated to 200 °C for 3 h at a rate of 1.5 °C / min to obtain Cu precursor;

[0051] (2) Then, 55.0 g ammonium molybdate, 6.07 g ammonium metavanadate and 11.51 g ammonium tungstate were dissolved in 500 mL deionized water and stirred continuously at 60°C for 30 min to obtain a homogeneous solution.

[0052] (3) After that, 5 g of P123 was dissolved in the above solution to form a homogeneous solution. Then, the Cu precursor obtained in step (1) was dispersed into the system and stirred continuously for 2 h. Then, 6.21 g of antimony acetate was added and reacted continuously at 85°C for 5 h.

[0053] (4) After the reaction is complete, the above mixed solution is cooled to room temperature and spray dried. The inlet air temperature is controlled at 150°C, and the feeding speed is adjusted to keep the outlet temperature at 85°C. The product in the cyclone separator is collected.

[0054] (5) Finally, in a tube furnace, the temperature was increased to 390°C at an air feed rate of 150 mL / min and a rate of 1.5°C / min, and calcined for 8 hours to obtain catalyst powder, denoted as STL-Cu. 0.5 -BDC.

[0055] Example 3: Mo 12 V2W 1.8 Cu 1.5 Sb 0.8 Preparation of -BDC (STL-Cu 1.5 -BDC)

[0056] (1) First, 8.87 g of Cu-BDC was placed in a muffle furnace and heated to 200 °C for 6 h at a rate of 1.0 °C / min to obtain Cu precursor;

[0057] (2) Then, 55.0 g ammonium molybdate, 6.07 g ammonium metavanadate and 11.51 g ammonium tungstate were dissolved in 500 mL deionized water and stirred continuously at 60°C for 30 min to obtain a homogeneous solution.

[0058] (3) After that, 5 g of F127 was dissolved in the above solution to form a homogeneous solution. Then, the Cu precursor obtained in step (1) was dispersed into the system and stirred continuously for 2 h. Then, 6.21 g of antimony acetate was added and reacted continuously at 85°C for 5 h.

[0059] (4) After the reaction is complete, the above mixed solution is cooled to room temperature and spray dried. The inlet air temperature is controlled at 150°C, and the feeding speed is adjusted to keep the outlet temperature at 90°C. The product in the cyclone separator is collected.

[0060] (5) Finally, in a tube furnace, the temperature was increased to 390°C at an air feed rate of 220 mL / min and a rate of 1.5°C / min, and calcined for 8 hours to obtain catalyst powder, denoted as STL-Cu. 1.5 -BDC.

[0061] Example 4: Mo 12 V2W 1.8 Cu 1.2 Sb 0.8 Preparation of BTC (STL-Cu) 1.2 -BTC)

[0062] (1) First, 20.53 g of Cu-BTC was placed in a muffle furnace and heated to 220 °C at a rate of 1.5 °C / min for 8 h to obtain Cu precursor;

[0063] (2) Then, 55.0 g ammonium molybdate, 6.07 g ammonium metavanadate and 11.51 g ammonium tungstate were dissolved in 500 mL deionized water and stirred continuously at 60°C for 30 min to obtain a homogeneous solution.

[0064] (3) After that, 5 g of P123 was dissolved in the above solution to form a homogeneous solution. Then, the Cu precursor obtained in step (1) was dispersed into the system and stirred continuously for 3 h. Then, 6.21 g of antimony acetate was added and reacted continuously at 85°C for 5 h.

[0065] (4) After the reaction is complete, the above mixed solution is cooled to room temperature and spray dried. The inlet air temperature is controlled at 150°C, and the feeding speed is adjusted to keep the outlet temperature at 95°C. The product in the cyclone separator is collected.

[0066] (5) Finally, in a tube furnace, the temperature was increased to 390°C at an air feed rate of 280 mL / min and a rate of 1.5°C / min, and calcined for 8 hours to obtain catalyst powder, denoted as STL-Cu. 1.2 -BTC.

[0067] Example 5: Mo 12 V2W 1.8 Cu 1.2 Sb 0.8 Preparation of MOF-47 (STL-Cu) 1.2 -MOF-47)

[0068] (1) First, 14.67 g of Cu-MOF-74 was placed in a muffle furnace and heated to 200 °C for 6 h at a rate of 1.2 °C / min to obtain Cu precursor;

[0069] (2) Then, 55.0 g ammonium molybdate, 6.07 g ammonium metavanadate and 11.51 g ammonium tungstate were dissolved in 500 mL deionized water and stirred continuously at 60°C for 30 min to obtain a homogeneous solution.

[0070] (3) After that, 5 g of P123 was dissolved in the above solution to form a homogeneous solution. Then, the Cu precursor obtained in step (1) was dispersed into the system and stirred continuously for 2 h. Then, 6.21 g of antimony acetate was added and reacted continuously at 90 °C for 5 h.

[0071] (4) After the reaction is complete, the above mixed solution is cooled to room temperature and spray dried. The inlet air temperature is controlled at 150°C, and the feeding speed is adjusted to keep the outlet temperature at 95°C. The product in the cyclone separator is collected.

[0072] (5) Finally, in a tube furnace, the temperature was increased to 390°C at an air feed rate of 200 mL / min and a rate of 1.5°C / min, and calcined for 8 hours to obtain catalyst powder, denoted as STL-Cu. 1.2 -MOF-47.

[0073] Comparative Example 1: Mo 12 V2W 1.8 Cu 1.2 Sb 0.8 Preparation of STL-Cu 1.2 *)

[0074] (1) First, 55.0 g ammonium molybdate, 6.07 g ammonium metavanadate and 11.51 g ammonium tungstate were dissolved in 500 mL deionized water and stirred continuously at 60°C for 30 min to obtain a homogeneous solution.

[0075] (2) Then, 7.53 g of copper nitrate was dissolved in the above solution, and 6.21 g of antimony acetate was added. The reaction was carried out continuously at 85°C for 5 hours.

[0076] (3) After the reaction is completed, the above mixed solution is cooled to room temperature and spray dried. The inlet air temperature is controlled at 150°C, and the feeding speed is adjusted to keep the outlet temperature at 90°C. The product in the cyclone separator is collected.

[0077] (4) Finally, in a tube furnace, the temperature was increased to 390°C at an air feed rate of 200 mL / min and a rate of 1.5°C / min, and calcined for 8 hours to obtain catalyst powder, denoted as STL-Cu. 1.2 *

[0078] Comparative Example 2: Mo 12 V2W 1.8 Cu 1.2 Sb 0.8 Preparation of -BDC* (STL-Cu) 1.2 -BDC-one pot*)

[0079] (1) First, 55.0 g ammonium molybdate, 6.07 g ammonium metavanadate and 11.51 g ammonium tungstate were dissolved in 500 mL deionized water and stirred continuously at 60°C for 30 min to obtain a homogeneous solution.

[0080] (2) Then, 7.09 g Cu-BDC and 6.21 g antimony acetate were added to the above solution in sequence and reacted continuously at 85°C for 5 hours.

[0081] (3) After the reaction is completed, the above mixed solution is cooled to room temperature and spray dried. The inlet air temperature is controlled at 130°C, and the feeding speed is adjusted to keep the outlet temperature at 90°C. The product in the cyclone separator is collected.

[0082] (4) Finally, in a tube furnace, the temperature was increased to 390°C at an air feed rate of 200 mL / min and a rate of 1.5°C / min, and calcined for 8 hours to obtain catalyst powder, denoted as STL-Cu. 1.2 -BDC-one pot*.

[0083] Comparative Example 3: Mo 12 V2W 1.8 Cu 1.2 Sb 0.8 Preparation of -BTC* (STL-Cu 1.2 -BTC-one pot*)

[0084] (1) First, 55.0 g ammonium molybdate, 6.07 g ammonium metavanadate and 11.51 g ammonium tungstate were dissolved in 500 mL deionized water and stirred continuously at 60°C for 30 min to obtain a homogeneous solution.

[0085] (2) Then, 20.53 g Cu-BTC and 6.21 g antimony acetate were added to the above solution in sequence, and the reaction was carried out continuously at 85°C for 5 hours;

[0086] (3) After the reaction is completed, the above mixed solution is cooled to room temperature and spray dried. The inlet air temperature is controlled at 150°C, and the feeding speed is adjusted to keep the outlet temperature at 95°C. The product in the cyclone separator is collected.

[0087] (4) Finally, in a tube furnace, the temperature was increased to 390°C at an air feed rate of 280 mL / min and a rate of 1.5°C / min, and calcined for 8 hours to obtain catalyst powder, denoted as STL-Cu. 1.2 -BTC-one pot*.

[0088] Comparative Example 4: Mo 12 V2W 1.8 Cu 1.2 Sb 0.8 Preparation of -MOF-47* (STL-Cu) 1.2 -MOF-47-one pot*)

[0089] (1) First, 55.0 g ammonium molybdate, 6.07 g ammonium metavanadate and 11.51 g ammonium tungstate were dissolved in 500 mL deionized water and stirred continuously at 60 °C for 30 min to obtain a homogeneous solution; the solution was placed in a muffle furnace and heated to 200 °C at a rate of 1.2 °C / min for 6 h to obtain Cu precursor;

[0090] (2) Then, 14.67 g Cu-MOF-74 and 6.21 g antimony acetate were added to the above solution in sequence, and the reaction was carried out continuously at 90°C for 5 hours.

[0091] (3) After the reaction is completed, the above mixed solution is cooled to room temperature and spray dried. The inlet air temperature is controlled at 110°C, and the feeding speed is adjusted to keep the outlet temperature at 90°C. The product in the cyclone separator is collected.

[0092] (4) Finally, in a tube furnace, the temperature was increased to 390°C at an air feed rate of 200 mL / min and a rate of 1.5°C / min, and calcined for 8 hours to obtain catalyst powder, denoted as STL-Cu. 1.2 -MOF-74-one pot*.

[0093] Performance testing

[0094] 1. Catalyst performance evaluation experiment:

[0095] Catalyst performance evaluation experiments were conducted in 25 mL reaction tubes containing two fixed beds. The first fixed bed was used for in-situ generation of acrolein, and the second fixed bed was used to test the catalysts prepared in Examples 1-5 and Comparative Example 1.

[0096] The specific reaction conditions were as follows: the catalysts prepared in Examples 1-5 and Comparative Examples 1-4 were pressed into tablets and pulverized to obtain 20-40 mesh catalyst powder. 10 g of the catalyst was weighed and mixed with an equal volume of 20-40 mesh quartz sand, then loaded into a fixed-bed reactor. The molar ratio of propylene / water / air 1 / nitrogen / air 2 was 1 / 1.00 / 7.45 / 2.40 / 2.39, and the propylene space velocity in the first stage of the fixed bed was 76 h⁻¹. -1 The reaction was conducted at a propylene concentration of 8.5%, a temperature of 330℃, an outlet pressure of 20 kPa in the second-stage fixed bed, and a reaction temperature of 260℃. Gas chromatography was used to analyze the reaction performance of the catalyst in the second-stage fixed bed. The sampling time was 24 h. The specific results are shown in Table 1 below.

[0097] Table 1. Comparison of catalytic performance between Examples 1-5 and Comparative Examples 1-4

[0098]

[0099] As shown in Table 1, Examples 1-3 and Comparative Example 1, replacing copper nitrate with Cu-based MOF material Cu-BDC in the Mo-VW-Cu-Sb pentagonal metal oxide catalyst increased the acrylic acid conversion rate from 98.02% to a maximum of 99.98%, and the acrylic acid yield from 91% to over 92.9%. The increased acrylic acid yield was mainly due to the decreased selectivity of the byproducts acetic acid and COx, and the increased selectivity of acrylic acid. Furthermore, replacing Cu-BDC with Cu-BTC or Cu-MOF-74 did not significantly reduce the acrolein conversion rate and acrylic acid yield (Examples 4 and 5), indicating that Cu-based MOF materials have a certain degree of versatility as Cu precursors. Furthermore, as shown in Comparative Examples 2-4, the catalysts prepared by directly introducing Cu-based MOFs materials as Cu sources into the catalyst preparation reaction solution have increased byproducts (acetic acid, COx), and the conversion rate of acrolein and the yield of acrylic acid are lower than those in Comparative Example 1 and Examples 1, 4, and 5. This indicates that directly adding Cu-based MOFs to the catalyst reaction solution will reduce the activity of the catalyst, further verifying the necessity of pretreatment of Cu-based MOFs.

[0100] 2. Anti-sintering performance evaluation experiment:

[0101] The catalyst anti-sintering performance evaluation experiment was also conducted in a fixed bed. First, the catalysts (Examples 1, 4, 5, and Comparative Example 1) were loaded into the reactor according to the performance evaluation experiment method. Then, under nitrogen and air atmospheres (nitrogen:air = 1:2), the two-stage reactors were raised to the target temperatures (300, 350, 390, 420, and 450 °C) and maintained for 6 h. Afterward, the temperature was lowered to the reaction temperature (260 °C) for the performance evaluation experiment. The reaction performance of the catalyst in the second-stage fixed bed was analyzed by gas chromatography, with a sampling time of 24 h. The specific results are shown in Table 2 below. Meanwhile, the crystal phase structure and surface morphology of Example 1 and Comparative Example 1 after calcination at different temperatures are shown in Table 2. Figures 4-7 .

[0102] Table 2 Comparison of anti-sintering properties of Examples 1, 4, 5 and Comparative Example 1

[0103]

[0104] As shown in Table 2, in Example 1 and Comparative Example 1, after replacing the copper salt with Cu-BDC, the acrolein conversion rate remained above 98.5% and the acrylic acid yield above 89.8% during the sintering temperature increase from 300℃ to 420℃. Upon further increasing the temperature to 450℃, the catalyst activity decreased, with the acrolein conversion rate dropping to 95.67% and the acrylic acid yield decreasing to 82.8%. For the catalyst prepared by the conventional method (Comparative Example 1), after reaching a sintering temperature of 420℃, the acrolein conversion rate decreased to 96.73%, and the acrylic acid yield decreased from 91.0% to 88.8%. Further increasing the sintering temperature to 380℃ resulted in a significant drop in acrolein conversion rate to 75.23%, and the acrylic acid yield was less than 60%. This phenomenon fully verifies that replacing the copper salt with Cu-BDC significantly improves the catalyst's anti-sintering performance in the acrolein oxidation to acrylic acid catalyst. Figures 4-7 This also corroborates that using Cu-based MOFs as raw materials can effectively improve the sintering resistance of catalysts. Examples 3 and 4 are comparative experiments on the sintering resistance of catalysts with different Cu-based MOFs. When the sintering temperature is below 390℃, the catalysts can still maintain high activity (acrylonitrile conversion rate >98.5%, acrylic acid yield >91%).

[0105] 3. Catalyst lifetime evaluation experiment:

[0106] Catalyst lifetime evaluation experiments were also conducted in a fixed bed, and the propylene space velocity was increased to 150 h⁻¹ to accelerate the catalyst deactivation process. -1The experiment was conducted as follows: First, the catalysts from Example 1 and Comparative Example 1 were loaded into the reactors according to the performance evaluation experiment method; the molar ratios of propylene / water / air 1 / nitrogen / air 2 were 1 / 1.0 / 7.45 / 2.40 / 2.39, and the propylene space velocity in a single-stage fixed bed was 150 h⁻¹. -1 Catalytic performance was tested under the following conditions: propylene concentration 8.5%, temperature 350℃; two-stage fixed bed outlet pressure 20 kPa, reaction temperature 250-280℃. The experimental results are shown in Table 3.

[0107] Table 3 Catalyst lifetime experiments in Example 1 and Comparative Example 1

[0108]

[0109] As shown in Table 3, the catalyst synthesized in Example 1 showed a growth rate of 150 h. -1 Under the specified conditions, the acrolein conversion rate remained above 93% and the acrylic acid yield was greater than 84% for 3000 h of continuous reaction. In contrast, the catalyst in Comparative Example 1 showed a decrease in acrolein conversion rate to 93% and acrylic acid yield to 80.4% after 1500 h of operation; after a further 2000 h of operation, the acrolein conversion rate fell below 85%, and the acrylic acid yield plummeted to 68.4%. This experiment demonstrates that replacing the copper salt with Cu-BDC significantly improves the catalyst lifetime.

[0110] The above embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit it. Within the principles of the present invention, any person skilled in the art can modify or make equivalent substitutions to the described embodiments, and such modifications and variations should be considered to fall within the protection scope of the present invention.

Claims

1. A method for preparing an anti-sintering catalyst, characterized in that, Includes the following steps: (1) Cu-MOFs were subjected to preliminary pyrolysis to obtain Cu precursors; (2) Dissolve water-soluble metal salts containing Mo, V, and W in water to obtain a mixed solution; (3) Add dispersant, Cu precursor and Sb salt to the mixed solution in sequence, and react continuously at 85~95℃ for 4~6 hours to obtain catalyst slurry; (4) After the reaction is complete, the catalyst slurry is spray-granulated to obtain a solid precursor; (5) The solid precursor is calcined in a tube furnace under an air atmosphere to obtain the catalyst.

2. The preparation method according to claim 1, characterized in that, The Cu-MOFs are one or more of Cu-BTC, Cu-BDC, and Cu-MOF-74.

3. The preparation method according to claim 1, characterized in that, The initial pyrolysis temperature is 150~260℃.

4. The preparation method according to claim 1, characterized in that, The raw material for Mo is selected from one or two of ammonium molybdate and ammonium paramolybdate; the raw material for V is selected from one or two of vanadium oxalate and ammonium metavanadate; and the raw material for W is selected from one or more of ammonium tungstate, ammonium paratungstate, and ammonium metatungstate.

5. The preparation method according to claim 1, characterized in that, The dispersing agent is selected from one or more of carboxymethyl cellulose, P123, F127, and polyethylene glycol; the raw material for Sb salt is selected from one or two of antimony acetate and antimony oxide.

6. The preparation method according to claim 1, characterized in that, The spray granulation process conditions are: inlet temperature 120~180℃, outlet temperature 70~100℃.

7. The preparation method according to claim 1, characterized in that, The air feed rate of the tubular furnace is 20 mL / min, and the heating rate is 1~2℃ / min.

8. The preparation method according to claim 1, characterized in that, The roasting temperature is 300~400℃ and the time is 8~12 hours.

9. A catalyst resistant to sintering, characterized in that, The preparation method according to any one of claims 1-8 yields a product with the general formula Mo. 12 V a W b Cu c Sb d O x In the formula, a, b, c, and d represent the atomic ratios of each element, where a = 1~5, b = 0.5~2.5, c = 0.5~3, and d = 0~1.

5. The amount of Cu-MOFs added is calculated based on the actual Cu element content.

10. The application of the anti-sintering catalyst according to claim 9, characterized in that, It is used in the catalytic oxidation of acrolein to prepare acrylic acid.

Images