Hierarchical pore molecular sieve loaded Cu-based bifunctional catalyst as well as preparation method and application thereof

Abstract

The invention provides a hierarchical pore molecular sieve loaded Cu-based bifunctional catalyst as well as a preparation method and application thereof, and relates to the technical field of catalyst preparation and application. The preparation method comprises the following steps: firstly, carrying out alkali treatment on a microporous molecular sieve to introduce mesopores, and then carrying out ammonium exchange and roasting to obtain the molecular sieve containing the intracrystalline mesoporous structure. And then introducing intergranular pores by adopting a one-step ball milling method to obtain the hierarchical pore molecular sieve, and simultaneously realizing construction of metal active sites. According to the invention, the hierarchical pore molecular sieve supported metal catalyst with both intracrystalline mesopores and intercrystalline pores is successfully prepared through a ball milling-alkali treatment bridging strategy for the first time. The catalyst has a transparent intergranular pore-intracrystalline mesopore-micropore hierarchical porous structure, and has high catalytic performance in a macromolecular catalytic conversion reaction under the synergistic effect of a Cu-loaded site and a molecular sieve acid site.

Description

Technical Field

[0001] The present invention relates to the technical field of catalyst preparation and application, and in particular to a multi-level pore molecular sieve-supported Cu-based bifunctional catalyst and a preparation method and application thereof. Background Art

[0002] Diphenylmethane is an important fine chemical. At present, diphenylmethane is mainly produced by the reaction of benzene and benzyl chloride. HCl gas is produced during the reaction, which has high processing costs, high requirements for the reaction device, and adverse effects on the environment. In contrast, in the reaction system of synthesizing diphenylmethane from benzyl alcohol, the byproduct is water instead of HCl, which is more environmentally friendly. However, the synthesis efficiency of this method is lower than that of the reaction of benzyl chloride with benzyl chloride, which seriously restricts its application in industry. Therefore, it is urgent to develop an efficient catalyst for the benzylation reaction of benzyl alcohol with benzyl alcohol.

[0003] Zeolite-based catalysts are important catalytic materials in the modern chemical industry. Their large-scale application originated from traditional petrochemical processes and gradually played an important role in the production of basic chemicals and fine chemicals. For traditional microporous molecular sieves, their narrow pore structure limits the catalytic conversion process of macromolecules, and the catalyst is easily deactivated by carbon deposition during rapid carbon deposition. The preparation of multi-level pore molecular sieves can alleviate the above problems. However, the catalytic efficiency of a single molecular sieve acid site is low, and the molecular sieve needs to be metal-modified to further improve its catalytic efficiency. Summary of the invention

[0004] In view of the defects of the above-mentioned prior art, the purpose of the present invention is to provide a method for preparing a multi-level pore molecular sieve-loaded Cu-based bifunctional catalyst, which first uses an alkaline medium to cut the microporous molecular sieve pores, and constructs a transparent multi-level pore molecular sieve as a substrate for loading Cu sites; then ball milling is performed to achieve partial Si-O-Si and Si-O-Al fracture of the molecular sieve under the action of mechanical force, and intercrystalline pores and defect sites are generated. At the same time, a Cu-containing precursor is introduced during the ball milling process, and the effect of the Cu precursor and the molecular sieve defect sites realizes the one-step creation of a multi-level pore molecular sieve-loaded Cu-based catalyst; under the action of mechanical force, it is conducive to the dispersion of the Cu precursor, and the introduced intracrystalline mesopores and intercrystalline pores greatly shorten the distance between the Cu site and the acid site, which can give full play to the synergistic effect of the two, and the transparent multi-level pore channel structure significantly improves the diffusion rate of reactants and products, and the obtained multi-level pore molecular sieve-loaded Cu-based bifunctional catalyst has a high catalytic performance in the catalytic reaction of benzene and benzyl alcohol.

[0005] The catalyst preparation method provided by the invention is simple, has an adjustable pore structure, and is suitable for industrial production.

[0006] To achieve the above object, the present invention provides a method for preparing a multi-level pore molecular sieve supported Cu-based bifunctional catalyst, comprising the following steps:

[0007] S1, placing the microporous molecular sieve sample in an alkaline medium solution at a temperature of 60-90°C for 15-90 minutes of alkaline treatment; then, centrifuging or filtering the sample to neutrality, drying it at 80-140°C for 6-48 hours, and then calcining it at 450-700°C for 1-9 hours;

[0008] S2, with NH 4 NO 3 or NH 4 The sample treated in step S1 is subjected to ammonium exchange with a Cl solution, and then calcined to obtain a hierarchical pore size molecular sieve;

[0009] S3, placing the multi-level porous molecular sieve obtained in step S2 in a ball mill, adding deionized water, and ball milling at a speed of 100 to 500 rpm for 3 to 15 hours; then adding a Cu-containing precursor solution, and continuing the ball milling at a speed of 100 to 500 rpm for 2 to 15 hours;

[0010] S4, the sample after ball milling is first subjected to rotary evaporation to remove the solvent, and then dried in an oven at 80-140°C for 6-48h, and then the dried sample is placed in a muffle furnace and calcined at 450-700°C for 1-5h to finally obtain a multi-level porous molecular sieve-supported Cu-based bifunctional catalyst.

[0011] In the embodiments of the present application, the present invention first introduces a mesoporous multi-level molecular sieve as a substrate for loading Cu by alkali treatment, then ball-mills the molecular sieve to introduce an intercrystalline pore structure, and simultaneously adds a copper precursor during the treatment process, and then achieves the preparation of a multi-level molecular sieve loaded with Cu-based catalysts by high-temperature conversion and the like. Under the synergistic effect of the molecular sieve acid sites and the loaded Cu active sites, the alkylation reaction of benzene and benzyl alcohol can be achieved to efficiently synthesize diphenylmethane.

[0012] Furthermore, in step S3, the Cu-containing precursor is one of copper nitrate, cupric chloride, cuprous nitrate, cuprous chloride, and cupric acetate.

[0013] Furthermore, in step S2, the temperature condition of the ammonium exchange is 60-90°C, the exchange time is 15-90min, and the number of exchanges is 1 to 5 times.

[0014] Furthermore, in step S1, the alkaline medium solution is NaOH, KOH, ammonia, Na 2 CO 3A mixed system of one or more of the following; the concentration of the substance amount of the alkaline medium is 0.05-0.5 mol / L, and the mass ratio of the volume of the alkaline medium solution to the microporous molecular sieve is (10-50) ml: 1 g.

[0015] Furthermore, in step S4, the temperature of the rotary evaporation is 40-80°C.

[0016] The present invention also provides a multi-level pore molecular sieve loaded Cu-based bifunctional catalyst, which is prepared by the aforementioned preparation method. The multi-level pore molecular sieve loaded Cu-based bifunctional catalyst comprises a multi-level pore molecular sieve and a loaded Cu component; the main component of the multi-level pore molecular sieve is an aluminosilicate molecular sieve, and the multi-level pore molecular sieve contains micropores, intracrystalline mesopores and intercrystalline pores.

[0017] Furthermore, the topological structure of the multi-level pore molecular sieve supported Cu-based bifunctional catalyst is MFI type or BEA type.

[0018] Furthermore, the silicon-aluminum atomic ratio of the multi-level pore molecular sieve supported Cu-based bifunctional catalyst is Si / Al=15-50.

[0019] The aforementioned multi-level pore molecular sieve-supported Cu-based bifunctional catalyst can be used to prepare diphenylmethane, specifically comprising the following steps: adding benzene and the multi-level pore molecular sieve-supported Cu-based bifunctional catalyst into a reactor, preheating to the reaction temperature and adding benzyl alcohol, and benzyl alcohol undergoes a benzylation reaction to generate diphenylmethane.

[0020] Furthermore, the reaction temperature is 60-100° C., the reaction pressure is 0.1-0.5 MPa, and the ratio of benzene, benzyl alcohol and catalyst is benzene:benzyl alcohol:catalyst=(20-50) ml:(0.5-1) ml:(0.1-0.5) g.

[0021] The beneficial effects of the present invention are:

[0022] 1. The preparation method of the multi-level pore molecular sieve supported Cu-based bifunctional catalyst provided by the present invention, through the alkali treatment and ball milling treatment bridging strategy, constructs intracrystalline mesopores and intercrystalline pore structures in the molecular sieve, and improves the diffusion of reactants, intermediates and products from the dual perspectives of reducing the diffusion path and expanding the diffusion channel, especially conducive to improving the diffusion efficiency of macromolecular organic matter. With the help of ball milling treatment, the synchronous construction of intercrystalline pore structure and Cu active site is achieved; the defect sites generated during the ball milling process provide an ideal landing environment for the loaded metal Cu, and realize the efficient landing and anchoring of the Cu site; at the same time, the introduction of multi-level pore channels shortens the distance between the Cu active site and the molecular sieve acid site, which is conducive to the synergistic effect of the two, and obtains a high-efficiency multi-level pore molecular sieve supported Cu-based bifunctional catalyst for the benzylation reaction of benzene and benzyl alcohol.

[0023] 2. The multi-level pore molecular sieve supported Cu-based bifunctional catalyst prepared by the present invention comprises a multi-level pore molecular sieve support and a supported active metal Cu site, and through an alkali treatment-ball milling treatment bridging strategy, the catalyst is realized to have a structure of a multi-level pore structure of intracrystalline mesopores and intercrystalline pores, and a Cu active site is constructed simultaneously when the intercrystalline pore structure is introduced. The Cu site of the catalyst has a high degree of dispersion and has a high catalytic performance in the benzylation reaction of benzene and benzyl alcohol. The multi-level pore molecular sieve supported Cu-based bifunctional catalyst provided by the present invention has simple operation steps and production equipment, low preparation cost, and is suitable for large-scale industrialization and industrial application. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The performance results of the catalysts prepared in Examples 1-3 and Comparative Examples 1-3 in the benzylation reaction of benzene and benzyl alcohol.

[0025] Figure 2 XRD spectra of the catalysts prepared in Examples 1-2 and Comparative Examples 1-3.

[0026] Figure 3 This is a SEM image of the multi-level pore molecular sieve supported Cu-based bifunctional catalyst prepared in Example 1.

[0027] Figure 4 This is the SEM image of the sample in Comparative Example 1. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] It should also be noted that, in order to avoid obscuring the present invention due to unnecessary details, only structures and / or processing steps closely related to the scheme of the present invention are shown in the drawings, while other details that are not closely related to the present invention are omitted.

[0030] In addition, it should be noted that the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus.

[0031] The narrow pore structure of traditional microporous molecular sieves limits the catalytic conversion process of large molecules, and the catalyst is easily deactivated by carbon deposition during rapid carbon deposition. The catalytic efficiency of a single molecular sieve acid site is also low.

[0032] The invention provides a high-efficiency multi-level pore molecular sieve-loaded Cu-based bifunctional catalyst for the benzylation reaction of benzyl alcohol. The multi-level pore molecular sieve with mesoporous structure is introduced as a substrate for loading Cu active sites through alkali treatment, and then the molecular sieve is subjected to ball milling treatment. A copper precursor is added during the treatment process, and then the multi-level pore molecular sieve-loaded Cu-based bifunctional catalyst is prepared through high-temperature conversion and the like. Under the synergistic effect of the molecular sieve acid site and the loaded Cu active site, the alkylation reaction of benzyl alcohol and benzyl alcohol can be realized to efficiently synthesize diphenylmethane.

[0033] In one aspect, the present invention provides a method for preparing a multi-level pore molecular sieve supported Cu-based bifunctional catalyst, comprising the following steps:

[0034] S1, placing the microporous molecular sieve sample in an alkaline medium solution at a temperature of 60-90°C for 15-90 minutes of alkaline treatment; then, centrifuging or filtering the sample to neutrality, drying it at 80-140°C for 6-48 hours, and then calcining it at 450-700°C for 1-9 hours;

[0035] Among them, the alkaline medium solution is NaOH, KOH, ammonia, Na 2 CO 3 The concentration of the substance in the alkaline medium is 0.05-0.5 mol / L, and the volume ratio of the alkaline medium solution to the mass ratio of the microporous molecular sieve is (10-50) ml: 1 g.

[0036] S2, with NH 4 NO 3 or NH 4 The sample treated in step S1 is subjected to ammonium exchange with a Cl solution, and then calcined to obtain a hierarchical pore size molecular sieve;

[0037] The temperature condition of ammonium exchange is 60-90°C, the exchange time is 15-90min, and the exchange times are 1-5 times.

[0038] S3, placing the multi-level porous molecular sieve obtained in step S2 in a ball mill, adding deionized water, and ball milling at a speed of 100 to 500 rpm for 3 to 15 hours; then adding a Cu-containing precursor solution, and continuing the ball milling at a speed of 100 to 500 rpm for 2 to 15 hours;

[0039] Wherein, the Cu-containing precursor is one of copper nitrate, cupric chloride, cuprous nitrate, cuprous chloride and cupric acetate.

[0040] S4, the sample after ball milling is first subjected to rotary evaporation to remove the solvent, and then dried in an oven at 80-140°C for 6-48h, and then the dried sample is placed in a muffle furnace and calcined at 450-700°C for 1-5h to finally obtain a multi-level porous molecular sieve-supported Cu-based bifunctional catalyst.

[0041] Wherein, the temperature of rotary evaporation is 40-80°C.

[0042] In the examples of the present application, the microporous molecular sieve is first treated with alkali to introduce mesopores, and then ammonium exchange and calcination are performed to obtain a molecular sieve containing an intracrystalline mesoporous structure. Then, a one-step ball milling method is used to introduce intercrystalline pores to obtain a multi-level pore molecular sieve, and the construction of the intercrystalline pore structure and the construction of the metal Cu active site are achieved at the same time.

[0043] In the second aspect, the present invention also provides a multi-level pore molecular sieve loaded Cu-based bifunctional catalyst, which is prepared by the aforementioned preparation method. The multi-level pore molecular sieve loaded Cu-based bifunctional catalyst includes a multi-level pore molecular sieve and loaded Cu active sites; the main component of the multi-level pore molecular sieve is aluminosilicate molecular sieve, and the multi-level pore molecular sieve contains micropores, intracrystalline mesopores and intercrystalline pores.

[0044] Among them, the topological structure of the multi-level pore molecular sieve supported Cu-based bifunctional catalyst is MFI type or BEA type.

[0045] The silicon-aluminum atomic ratio of the multi-level pore molecular sieve supported Cu-based bifunctional catalyst is Si / Al=15-50.

[0046] The present invention successfully prepared a multi-level pore molecular sieve-supported metal catalyst with both intracrystalline mesopores and intercrystalline pores for the first time through a ball milling-alkali treatment bridging strategy. The catalyst is characterized by a transparent multi-level pore structure of intercrystalline pores-intracrystalline mesopores-micropores, and at the same time, under the synergistic effect of the loaded Cu active sites and the molecular sieve acid sites, it has a high catalytic performance in the macromolecular catalytic conversion reaction.

[0047] The aforementioned multi-level pore molecular sieve-supported Cu-based bifunctional catalyst can be used to prepare diphenylmethane, specifically comprising the following steps: adding benzene and the multi-level pore molecular sieve-supported Cu-based bifunctional catalyst into a reactor, preheating to the reaction temperature and adding benzyl alcohol, and benzyl alcohol undergoes a benzylation reaction to generate diphenylmethane.

[0048] The reaction temperature is 60-100°C and the reaction pressure is 0.1-0.5MPa.

[0049] The ratio of benzene, benzyl alcohol and catalyst is benzene:benzyl alcohol:catalyst=(20-50)ml:(0.5-1)ml:(0.1-0.5)g.

[0050] The preparation method of the multi-level pore molecular sieve supported Cu-based bifunctional catalyst provided by the present invention is described below in conjunction with specific examples. Unless otherwise specified, the raw materials and reagents in the examples of the present application are purchased through commercial channels.

[0051] Example 1

[0052] This embodiment provides a method for preparing diphenylmethane by benzylating benzene with benzyl alcohol, comprising the following steps:

[0053] 1) Prepare 0.2M sodium hydroxide, take 450 ml into a polypropylene flask, place it in a water bath and heat it to 70°C, then add 15g HZSM-5 molecular sieve (Si / Al=35), stir for 30min, and the solid-liquid ratio is 1 / 30; wash the reaction product with deionized water until neutral, dry it at 110°C for 12h, and calcine it at 550°C for 3h.

[0054] 2) The obtained molecular sieve was then added to a 0.6M ammonium chloride solution with a solid-liquid ratio of 1 / 20, magnetically stirred at 80°C for 2 hours, and the exchange was repeated 3 times. The reaction product was then filtered and washed with deionized water, dried at 120°C for 8 hours, and calcined at 550°C for 3 hours, and recorded as a multi-level pore molecular sieve.

[0055] 3) 10 g of multi-level pore molecular sieve, 15 ml of deionized water and 50 g of zirconium oxide balls were placed in a ball mill and treated at 250 rpm for 6 h. Then 15 ml of an aqueous solution containing 4.18 g of copper nitrate was added and the treatment was continued at 250 rpm for 12 h.

[0056] 4) The sample was transferred to a rotary evaporator to evaporate the solvent, and then dried in an oven at 120° C. for 8 h, and then calcined in a muffle furnace at 550° C. for 3 h to obtain catalyst A (multi-level pore molecular sieve supported Cu-based bifunctional catalyst).

[0057] 5) The multi-level porous molecular sieve catalyst (0.15 g) was placed in a reaction device, and then 35 ml of benzene was added. The mixture was stirred at 80°C for 1 h. 0.5 ml of benzyl alcohol was added to the reaction device to start the reaction. After 2 h of reaction, a sample was taken for gas chromatography analysis. The product was separated using an HP-5 capillary column and detected using an FID detector. The reaction performance results are shown in Figure 1 .

[0058] Example 2

[0059] Example 2 provides a method for preparing diphenylmethane by benzylating benzene with benzyl alcohol, comprising the following steps:

[0060] 1) Prepare 0.3M sodium hydroxide, take 450 ml into a polypropylene flask, place it in a water bath and heat it to 70°C, then add 15g HZSM-5 molecular sieve (Si / Al=35), stir for 30min, and the solid-liquid ratio is 1 / 30; wash the reaction product with deionized water until neutral, dry it at 110°C for 12h, and calcine it at 550°C for 3h.

[0061] 2) The obtained molecular sieve was then added to a 0.8M ammonium chloride solution with a solid-liquid ratio of 1 / 20, and magnetically stirred at 80°C for 2 hours, and the exchange was repeated twice. The reaction product was then filtered and washed with deionized water, dried at 120°C for 8 hours, and calcined at 550°C for 3 hours, and recorded as a multi-level pore molecular sieve.

[0062] 3) 10 g of multi-level pore molecular sieve, 15 ml of deionized water and 50 g of zirconium oxide balls were placed in a ball mill and treated at 230 rpm for 5 h. Then 15 ml of an aqueous solution containing 4.18 g of copper nitrate was added and the treatment was continued at 230 rpm for 15 h.

[0063] 4) The sample was transferred to a rotary evaporator to evaporate the solvent, and then dried in an oven at 110° C. for 8 h, and then calcined in a muffle furnace at 550° C. for 3 h to obtain catalyst B.

[0064] 5) The multi-level porous molecular sieve catalyst (0.15 g) was placed in a reaction device, and then 35 ml of benzene was added. The mixture was stirred at 80°C for 1 h. 0.5 ml of benzyl alcohol was added to the reaction device to start the reaction. After 2 h of reaction, a sample was taken for gas chromatography analysis. The product was separated using an HP-5 capillary column and detected using an FID detector. The reaction performance results are shown in Figure 1 .

[0065] Example 3

[0066] Example 3 provides a method for preparing diphenylmethane by benzylating benzene with benzyl alcohol, comprising the following steps:

[0067] 1) Prepare 0.2M sodium hydroxide, take 450 ml into a polypropylene flask, place it in a water bath and heat it to 70°C, then add 15g HZSM-5 molecular sieve (Si / Al=27.5), stir for 30min, and the solid-liquid ratio is 1 / 30; wash the reaction product with deionized water until neutral, dry it at 110°C for 12h, and calcine it at 550°C for 3h.

[0068] 2) The obtained molecular sieve was then added to a 0.6M ammonium chloride solution with a solid-liquid ratio of 1 / 20, magnetically stirred at 80°C for 2 hours, and the exchange was repeated twice. The reaction product was then filtered and washed with deionized water, dried at 100°C for 8 hours, and calcined at 550°C for 3 hours, and recorded as a multi-level pore molecular sieve.

[0069] 3) 10 g of multi-level porous molecular sieve, 15 ml of deionized water and 50 g of zirconium oxide balls were placed in a ball mill and treated at 200 rpm for 5 h, then 15 ml of an aqueous solution containing 4.18 g of copper nitrate was added and the treatment was continued at 200 rpm for 5 h.

[0070] 4) The sample was transferred to a rotary evaporator to evaporate the solvent, and then dried in an oven at 100° C. for 8 h, and then calcined in a muffle furnace at 550° C. for 3 h to obtain catalyst C.

[0071] 5) The multi-level porous molecular sieve catalyst (0.15 g) was placed in a reaction device, and then 35 ml of benzene was added. The mixture was stirred at 80°C for 1 h. 0.5 ml of benzyl alcohol was added to the reaction device to start the reaction. After 2 h of reaction, a sample was taken for gas chromatography analysis. The product was separated using an HP-5 capillary column and detected using an FID detector. The reaction performance results are shown in Figure 1 .

[0072] Comparative Example 1

[0073] Comparative Example 1 provides a method for preparing diphenylmethane by benzylating benzyl alcohol with benzyl alcohol. The main difference from Example 1 is that a microporous HZSM-5 molecular sieve (Si / Al=35) is used. The specific process is as follows:

[0074] 0.15 g of microporous HZSM-5 molecular sieve (Si / Al=35) was placed in a reaction device, and then 35 ml of benzene was added. The mixture was stirred at 80°C for 1 h. 0.5 ml of benzyl alcohol was added to the reaction device to start the reaction. After 2 h of reaction, samples were taken for gas chromatography analysis. The products were separated using an HP-5 capillary column and detected using an FID detector. The reaction performance results are shown in Figure 1 .

[0075] Comparative Example 2

[0076] Comparative Example 2 provides a method for preparing diphenylmethane by benzylating benzene with benzyl alcohol, which is different from Example 1 mainly in that step 3) Cu loading is not performed. The specific process is as follows:

[0077] 1) Prepare 0.2M sodium hydroxide, take 450ml in a polypropylene flask, place it in a water bath and heat it to 70°C, then add 15g HZSM-5 molecular sieve (Si / Al=35), stir for 30min, the solid-liquid ratio is 1 / 30; wash the reaction product with deionized water until neutral, dry at 110°C for 12h, and roast at 550°C for 2h. Then add the obtained molecular sieve to 0.6M ammonium chloride solution, the solid-liquid ratio is 1 / 20, stir magnetically at 80°C for 2 hours, repeat the exchange 3 times, then filter and wash the reaction product with deionized water, dry at 120°C for 8h, and roast at 550°C for 3h.

[0078] 2) 15g of the multi-level pore molecular sieve, 30g of deionized water and 75g of zirconium oxide balls were placed in a ball mill and treated at 300rpm for 18h. The treated sample was dried in an oven at 100°C for 8h, and then calcined in a muffle furnace at 550°C for 3h, which was recorded as multi-level pore molecular sieve catalyst A2.

[0079] 3) The multi-level porous molecular sieve catalyst A2 (0.15 g) was placed in a reaction device, and then 35 ml of benzene was added. The mixture was stirred at 80°C for 1 h. 0.5 ml of benzyl alcohol was added to the reaction device to start the reaction. After 2 h of reaction, a sample was taken for gas chromatography analysis. The product was separated using an HP-5 capillary column and detected using an FID detector. The reaction performance results are shown in Figure 1 .

[0080] Comparative Example 3

[0081] Comparative Example 3 provides a method for preparing diphenylmethane by benzylating benzene with benzyl alcohol, which is different from Example 1 mainly in that step 1) and step 2) are not performed. The specific process is as follows:

[0082] 1) Add 30 ml of an aqueous solution containing 4.18 g of copper nitrate to 10 g of HZSM-5 molecular sieve (Si / Al=35), stir at room temperature for 12 h at 250 rpm, transfer the sample to a rotary evaporator to evaporate the solvent, dry it in an oven at 120° C. for 8 h, and then calcine it in a muffle furnace at 550° C. for 3 h to obtain catalyst A3.

[0083] 2) The above catalyst A3 (0.15 g) was placed in a reaction apparatus, and then 35 ml of benzene was added. The mixture was stirred at 80° C. for 1 h. 0.5 ml of benzyl alcohol was added to the reaction apparatus to start the reaction. After 2 h of reaction, a sample was taken for gas chromatography analysis. The product was separated using an HP-5 capillary column and detected using an FID detector. The reaction performance results are shown in Figure 1 .

[0084] like Figure 1 As shown, by comparing Example 1 with Comparative Examples 1 and 2, it can be seen that the multi-level porous molecular sieve supported Cu-based catalyst has higher catalytic performance, which is significantly higher than the catalyst without metal Cu in Comparative Examples 1-2, proving that the supported metal Cu site is the active center for catalyzing the benzylation reaction of benzene and benzyl alcohol.

[0085] By comparing Example 1 and Comparative Example 3, it can be seen that in the absence of alkali treatment and ball milling steps, the catalytic performance of the prepared catalyst is significantly reduced, proving that intracrystalline mesopores and intercrystalline pores are beneficial to improving the diffusion of organic matter and promoting the synergistic effect of Cu sites and molecular sieve acid sites.

[0086] Figure 2The XRD spectra of the catalysts prepared in Examples 1-2 and Comparative Examples 1-3 show that after alkali treatment, ball milling and introduction of Cu active sites, the intensity of the molecular sieve diffraction peak does not change significantly, indicating that the molecular sieve maintains the crystalline structure.

[0087] Figure 3 This is a SEM image of the catalyst prepared in Example 1. It can be seen that after alkali treatment and ball milling, the catalyst has a rough surface and a smaller particle size, proving that after alkali etching and ball milling, obvious intracrystalline mesopores and intercrystalline pore structures formed by the accumulation of small particles are formed.

[0088] Figure 4 This is a SEM image of the catalyst prepared in Comparative Example 1. It can be seen that the microporous molecular sieve has a smooth surface and a larger particle size, and no obvious pore structure is observed, which further proves that the intracrystalline mesopores and intercrystalline pore structures in the catalyst sample in Example 1 are constructed through the alkali treatment-ball milling treatment bridging strategy.

[0089] Experiments show that the Cu-containing precursor can also be one of cupric chloride, cuprous nitrate, cuprous chloride, and cupric acetate.

[0090] The above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solution of the present invention.

Claims

1. A method for preparing a multi-level pore molecular sieve supported Cu-based bifunctional catalyst, characterized in that: The steps include: S1, placing the microporous molecular sieve sample in an alkaline medium solution at a temperature of 60-90°C for 15-90 minutes of alkaline treatment; then, centrifuging or filtering the sample to neutrality, drying it at 80-140°C for 6-48 hours, and then calcining it at 450-700°C for 1-9 hours; S2, exchanging the sample treated in step S1 with NH4NO3 or NH4Cl solution, and then calcining to obtain a hierarchical pore size molecular sieve; S3, placing the multi-level porous molecular sieve obtained in step S2 in a ball mill, adding deionized water, and ball milling at a speed of 100 to 500 rpm for 3 to 15 hours; then adding a Cu-containing precursor solution, and continuing the ball milling at a speed of 100 to 500 rpm for 2 to 15 hours; S4, the sample after ball milling is first subjected to rotary evaporation to remove the solvent, and then dried in an oven at 80-140°C for 6-48h, and then the dried sample is placed in a muffle furnace and calcined at 450-700°C for 1-5h to finally obtain a multi-level porous molecular sieve-supported Cu-based bifunctional catalyst.

2. The method for preparing a multi-level porous molecular sieve supported Cu-based bifunctional catalyst according to claim 1, characterized in that: In step S3, the Cu-containing precursor is one of cupric nitrate, cupric chloride, cuprous nitrate, cuprous chloride, and cupric acetate.

3. The method for preparing a multi-level porous molecular sieve supported Cu-based bifunctional catalyst according to claim 1, characterized in that: In step S2, the temperature condition of the ammonium exchange is 60-90°C, the exchange time is 15-90min, and the number of exchanges is 1 to 5 times.

4. The method for preparing a multi-level porous molecular sieve supported Cu-based bifunctional catalyst according to claim 1, characterized in that: In step S1, the alkaline medium solution is a mixed system of one or more of NaOH, KOH, ammonia water, and Na2CO3; the concentration of the alkaline medium substance is 0.05-0.5 mol / L, and the volume ratio of the alkaline medium solution to the mass ratio of the microporous molecular sieve is (10-50) ml:1 g.

5. The method for preparing a multi-level porous molecular sieve supported Cu-based bifunctional catalyst according to claim 1, characterized in that: In step S4, the temperature of the rotary evaporation is 40 to 80°C.

6. A multi-level pore molecular sieve supported Cu-based bifunctional catalyst, prepared by the preparation method of the multi-level pore molecular sieve supported Cu-based bifunctional catalyst according to any one of claims 1 to 5, characterized in that: The multi-level pore molecular sieve loaded Cu-based bifunctional catalyst comprises a multi-level pore molecular sieve and a loaded Cu component; the main component of the multi-level pore molecular sieve is aluminosilicate molecular sieve, and the multi-level pore molecular sieve contains micropores, intracrystalline mesopores and intercrystalline pores.

7. The multi-level pore molecular sieve supported Cu-based bifunctional catalyst according to claim 6, characterized in that: The topological structure of the multi-level pore molecular sieve supported Cu-based bifunctional catalyst is MFI type or BEA type.

8. The multi-level pore molecular sieve supported Cu-based bifunctional catalyst according to claim 6, characterized in that: The silicon-aluminum atomic ratio of the multi-level pore molecular sieve-supported Cu-based bifunctional catalyst is Si / Al=15-50.

9. An application of a multi-level pore molecular sieve supported Cu-based bifunctional catalyst, characterized in that: The multi-level pore molecular sieve-supported Cu-based bifunctional catalyst is prepared according to the preparation method described in any one of claims 1 to 5 or is the multi-level pore molecular sieve-supported Cu-based bifunctional catalyst described in any one of claims 6 to 8; the multi-level pore molecular sieve-supported Cu-based bifunctional catalyst is used to prepare diphenylmethane, specifically comprising the following steps: adding benzene and the multi-level pore molecular sieve-supported Cu-based bifunctional catalyst into a reactor, preheating to the reaction temperature and then adding benzyl alcohol, and benzyl alcohol undergoes a benzylation reaction to generate diphenylmethane.

10. The use of the multi-level pore molecular sieve supported Cu-based bifunctional catalyst according to claim 9, characterized in that: The reaction temperature is 60-100° C., the reaction pressure is 0.1-0.5 MPa, and the ratio of benzene, benzyl alcohol and catalyst is benzene:benzyl alcohol:catalyst=(20-50) ml:(0.5-1) ml:(0.1-0.5) g.

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