阅读说明：本技术 一种苯加氢制备环己基苯用双金属催化剂及其制备方法和应用 (Bimetallic catalyst for preparing cyclohexylbenzene by benzene hydrogenation and preparation method and application thereof ) 是由 彭智昆 冯杰 刘仲毅 刘巧云 刘万年 于 2021-08-13 设计创作，主要内容包括：本发明公开了一种苯加氢制备环己基苯用双金属催化剂,该催化剂中金属Pd作为活性组分,Zn(Ni,Co,Cu)为金属助剂,助剂的加入使得催化剂获得较多的中间产物环己烯,提高了目标产物环己基苯的收率。本发明还公开了上述双金属催化剂的制备方法,该方法采用一步还原的方法,得到的催化剂中活性组分与金属助剂呈纳米颗粒状态,均匀分散在载体分子筛上,能够有效提高催化活性,具有步骤简便的优点。本发明还公开了上述双金属催化剂的应用,该双金属催化剂用于苯加氢制备环己基苯中,催化得到的环己基苯的收率可达22.23％,取得了良好的技术效果。(The invention discloses a bimetallic catalyst for preparing cyclohexylbenzene by benzene hydrogenation, wherein metal Pd is used as an active component, Zn (Ni, Co, Cu) is used as a metal auxiliary agent, and the addition of the auxiliary agent enables the catalyst to obtain more intermediate product cyclohexene, so that the yield of the target product cyclohexylbenzene is improved. The invention also discloses a preparation method of the bimetallic catalyst, and the method adopts a one-step reduction method, so that the active components and the metal auxiliary agent in the obtained catalyst are in a nanoparticle state and are uniformly dispersed on the carrier molecular sieve, the catalytic activity can be effectively improved, and the method has the advantage of simple and convenient steps. The invention also discloses the application of the bimetallic catalyst, the bimetallic catalyst is used for preparing the cyclohexylbenzene by the hydrogenation of the benzene, the yield of the cyclohexylbenzene obtained by catalysis can reach 22.23 percent, and a good technical effect is obtained.)

1. The bimetallic catalyst for preparing cyclohexylbenzene by benzene hydrogenation is characterized by comprising an active component, a metal auxiliary agent and a molecular sieve, wherein the active component and the metal auxiliary agent are loaded on the molecular sieve; the active component is metal Pd, and the metal auxiliary agent is one of Zn, Ni, Co and Cu.

2. The bimetallic catalyst for the hydrogenation of benzene to produce cyclohexylbenzene of claim 1, wherein the metal promoter is Zn.

3. The bimetallic catalyst for preparing cyclohexylbenzene by hydrogenating benzene according to claim 1, wherein the mass ratio of the active component to the metal promoter is 40-2: 1.

4. The bimetallic catalyst for the hydrogenation of benzene to produce cyclohexylbenzene of claim 1, wherein the mass ratio of the molecular sieve to the active component is 1: 0.01.

5. The bimetallic catalyst for preparing cyclohexylbenzene by hydrogenating benzene as claimed in claim 1, wherein the molecular sieve is an H-type Beta molecular sieve with a Si/Al ratio of 25-80.

6. The process for preparing the bimetallic catalyst for the hydrogenation of benzene to cyclohexylbenzene according to claim 1, comprising the steps of:

(1) removing a template agent in the Beta molecular sieve by a roasting method, and then carrying out H exchange on the obtained molecular sieve to obtain an H-type Beta molecular sieve which is marked as an HBeta molecular sieve;

(2) mixing the active component precursor solution with the metal auxiliary agent precursor solution, impregnating the HBeta molecular sieve obtained in the step (1), drying the impregnated HBeta molecular sieve, and performing reduction reaction to obtain a final product;

the active component precursor is PdCl₂The precursor of the metal auxiliary agent is ZnCl₂、NiCl₂、CoCl₂、CuCl₂One kind of (1).

7. The method for preparing the bimetallic catalyst for preparing cyclohexylbenzene by hydrogenating benzene according to claim 6, wherein the reduction reaction in the step (2) is carried out in a mixed gas atmosphere with a volume ratio of nitrogen to hydrogen being 9:1, at a reaction temperature of 300-400 ℃ for 2-4 h.

8. The method for preparing the bimetallic catalyst for preparing cyclohexylbenzene by hydrogenating benzene according to claim 6, wherein the specific process of H exchange of the molecular sieve in the step (1) is as follows:

(1.1) mixing the molecular sieve without the template agent, ammonium chloride and secondary water according to the mass ratio of 1:1: 10-30 to obtain a mixed solution, dropwise adding ammonia water to adjust the pH of the solution to 9-10, heating to 70-90 ℃ while stirring, and preserving heat for 1-3 hours; after the heat preservation is finished, carrying out suction filtration, washing and drying to obtain a solid phase substance;

(1.2) replacing the molecular sieve with the solid phase substance obtained in the step (1.1), and repeating the step (1.1) for a plurality of times;

and (1.3) roasting the solid phase obtained in the step (1.2) at 500-600 ℃ for 4-6H to obtain the H-type Beta molecular sieve which is marked as the HBeta molecular sieve.

9. The method for preparing the bimetallic catalyst for preparing cyclohexylbenzene by hydrogenating benzene according to claim 6, wherein the template removing agent in the step (1) is calcined at 500-600 ℃ for 4-6 h.

10. The use of the bimetallic catalyst for the hydrogenation of benzene to produce cyclohexylbenzene according to claim 1, wherein the reaction temperature during the production of cyclohexylbenzene is 100-300 ℃, the reaction hydrogen pressure is 1.0-4.0 MPa, the reaction time is 90-180 min, and the mass ratio of benzene to bimetallic catalyst is 40-50: 1.

Technical Field

The invention belongs to the technical field of catalysis, and relates to a bimetallic catalyst for preparing cyclohexylbenzene by benzene hydrogenation, and a preparation method and application thereof.

Background

Cyclohexylbenzene (CHB) is an important chemical intermediate which is widely applied to various fields. The cyclohexylbenzene can be used for producing benzyl hydroperoxide after oxidation, and the hydrogen peroxide is used as a starting material for preparing phenol and cyclohexanone. Phenol is a raw material for synthesizing phenolic resin, bisphenol A and alkylphenol, and cyclohexanone is an intermediate for producing caprolactam and nylon. Cyclohexylbenzene is also widely used as an electrolyte additive for overcharge protection of Lithium Ion Batteries (LIBs). In addition, the cyclohexylbenzene can also be used as a blending component and a raw material of the cetane number of diesel oil and used for synthesizing a thin film transistor liquid crystal display. Biphenyl is mainly used as a heat transfer fluid and a dye carrier in the textile industry, and the dehydrogenation of cyclohexylbenzene provides an economic and effective way for producing biphenyl.

The main production methods of cyclohexylbenzene are: benzene and cyclohexene alkylation, biphenyl hydrogenation, and benzene hydrogenation alkylation. The former two preparation methods are not focused by researchers because of high cost of raw materials for preparation and the like. The benzene hydroalkylation method for preparing cyclohexylbenzene has the advantages of rich raw materials, low cost, simple process and capability of greatly reducing the experimental cost. The preparation of cyclohexylbenzene by the benzene alkylation method at present comprises two steps: the selective hydrogenation of benzene to cyclohexene, the alkylation of cyclohexene and the preparation of cyclohexylbenzene from benzene. The key of the route for preparing cyclohexene by benzene hydrogenation is to prepare a high-activity and high-selectivity catalyst, the most researched bifunctional catalyst system is currently available, and the metal active site and the acidity of the catalyst are key factors of the route. However, in the current domestic research and production process, the performance of the catalyst used in the process route is not ideal enough, so that the problems of low selectivity, low yield and the like of the cyclohexylbenzene are caused. Therefore, it is important to find a high performance catalyst for improving the process of benzene hydroalkylation of cyclohexylbenzene.

Disclosure of Invention

In order to overcome the defects of the prior art, one of the purposes of the invention is to provide a bimetallic catalyst for preparing cyclohexylbenzene by benzene hydrogenation, which is used in the preparation of cyclohexylbenzene by benzene hydrogenation and can effectively improve the yield of cyclohexylbenzene.

The second object of the present invention is to provide a method for preparing the bimetallic catalyst.

The invention also aims to provide application of the bimetallic catalyst.

One of the purposes of the invention is realized by adopting the following technical scheme:

a bimetallic catalyst for preparing cyclohexylbenzene by benzene hydrogenation comprises an active component, a metal auxiliary agent and a molecular sieve, wherein the active component and the metal auxiliary agent are loaded on the molecular sieve; the active component is metal Pd, and the metal auxiliary agent is one of Zn, Ni, Co and Cu.

Further, the metal auxiliary agent is Zn.

Further, the mass ratio of the active component to the metal auxiliary agent is 40-2: 1.

Further, the mass ratio of the molecular sieve to the active component is 1: 0.01.

Further, the molecular sieve is an H-shaped Beta molecular sieve with the silicon-aluminum ratio of 25-80.

The second purpose of the invention is realized by adopting the following technical scheme:

the preparation method of the bimetallic catalyst for preparing the cyclohexylbenzene by hydrogenating the benzene comprises the following steps of:

(1) removing a template agent in the Beta molecular sieve by a roasting method, and then carrying out H exchange on the obtained molecular sieve to obtain an H-type Beta molecular sieve which is marked as an HBeta molecular sieve;

(2) mixing the active component precursor solution with the metal auxiliary agent precursor solution, impregnating the HBeta molecular sieve obtained in the step (1), drying the impregnated HBeta molecular sieve, and performing reduction reaction to obtain a final product;

the active component precursor is PdCl₂The precursor of the metal auxiliary agent is ZnCl₂、NiCl₂、CoCl₂、CuCl₂One kind of (1).

Further, the reduction reaction in the step (2) is carried out in a mixed gas atmosphere with a volume ratio of nitrogen to hydrogen being 9:1, the reaction temperature is 300-400 ℃, and the reaction time is 2-4 hours.

Further, the specific process of H exchange of the molecular sieve in the step (1) is as follows:

(1.1) mixing the molecular sieve without the template agent, ammonium chloride and secondary water according to the mass ratio of 1:1: 10-30 to obtain a mixed solution, dropwise adding ammonia water to adjust the pH of the solution to 10, heating to 70-90 ℃ while stirring, and preserving heat for 1-3 hours; after the heat preservation is finished, carrying out suction filtration, washing and drying to obtain a solid phase substance;

(1.2) replacing the molecular sieve with the solid phase substance obtained in the step (1.1), and repeating the step (1.1) for a plurality of times;

and (1.3) roasting the solid phase obtained in the step (1.2) at 500-60 ℃ for 4-6H to obtain the H-type Beta molecular sieve which is marked as the HBeta molecular sieve.

Further, the roasting temperature for removing the template agent in the step (1) is 500-600 ℃, and the time is 4-6 hours.

The third purpose of the invention is realized by adopting the following technical scheme:

the application of the bimetallic catalyst for preparing cyclohexylbenzene by benzene hydrogenation is characterized in that the reaction temperature is 100-300 ℃ in the preparation process of cyclohexylbenzene, the reaction hydrogen pressure is 1.0-4.0 MPa, the reaction time is 90-180 min, and the mass ratio of benzene to the bimetallic catalyst is 40-50: 1.

Compared with the prior art, the invention has the beneficial effects that:

the invention provides a bimetallic catalyst for preparing cyclohexylbenzene by benzene hydrogenation, wherein metal Pd is used as an active component, Zn (Ni, Co, Cu) is used as a metal auxiliary agent, and the addition of the auxiliary agent enables the catalyst to obtain more intermediate product cyclohexene, so that the yield of the target product cyclohexylbenzene is improved. The invention also provides a preparation method of the bimetallic catalyst, and the method adopts a one-step reduction method, so that the active components and the metal auxiliary agent in the obtained catalyst are in a nanoparticle state and are uniformly dispersed on the carrier molecular sieve, the catalytic activity can be effectively improved, and the method has the advantage of simple and convenient steps. The invention also provides the application of the bimetallic catalyst, the bimetallic catalyst is used for preparing the cyclohexylbenzene by benzene hydrogenation, and particularly, the metal auxiliary agent Zn is added, so that the yield of the cyclohexylbenzene obtained by catalysis can reach 22.23%, and a good technical effect is achieved.

Drawings

FIG. 1 is a flow chart illustrating the preparation of bimetallic catalyst for the hydrogenation of benzene to produce cyclohexylbenzene according to examples 1 to 4 of the present invention;

FIG. 2 is XRD spectra of samples No. 1-6 obtained in example 1 of the present invention and samples obtained in comparative example 1 and comparative example 2;

FIG. 3 is an XRD spectrum of samples obtained in examples 1 to 4 of the present invention;

FIG. 4 shows Pd in example 1 of the present invention₃₀TEM representation of Zn/HBeta, wherein FIGS. 4a, 4b, 4c are three different magnification scale images, and FIGS. 4c, 1-3, are HAADF-STEM images;

FIG. 5 shows Pd in example 1 of the present invention₃₀EDX characterization of Zn/HBeta, where fig. 5a is an EDX plot and fig. 5b is a Pd-Zn nanoparticle size distribution plot;

FIG. 6 is a TEM characterization of the samples of inventive examples 2 to 4 and comparative example 1, wherein FIG. 6a is the sample obtained in comparative example 1 and FIGS. 6b to 6d correspond to the samples obtained in examples 2 to 4, respectively;

FIG. 7 is a graph showing the distribution of the particle diameters of Pd-M nanoparticles in the samples of examples 2 to 4 according to the present invention and comparative example 1, and FIGS. 7a to 7d correspond to the samples of examples 2 to 4 and comparative example 1, respectively;

FIG. 8 is an XPS spectrum of samples No. 1 to 6 obtained in example 1 of the present invention and a sample of comparative example 1;

FIG. 9 shows Pd in example 1 of the present invention₃₀XPS spectra of samples of Zn/HBeta, examples 2 to 4, comparative example 1.

Detailed Description

The present invention will be further described with reference to the accompanying drawings and the detailed description, and it should be noted that any combination of the embodiments or technical features described below can be used to form a new embodiment without conflict.

FIG. 1 is a flow diagram illustrating the preparation of bimetallic catalyst for the hydrogenation of benzene to cyclohexylbenzene in examples 1 to 4.

Example 1

A bimetallic catalyst for preparing cyclohexylbenzene by benzene hydrogenation comprises an active component metal Pd, a metal assistant metal Zn and an HBeta molecular sieve, wherein the metal Pd and the metal Zn are loaded on the HBeta molecular sieve.

The preparation method of the bimetallic catalyst for preparing the cyclohexylbenzene by hydrogenating the benzene comprises the following steps of:

(1) roasting the Beta molecular sieve with the silicon-aluminum ratio of 30 at 500 ℃ for 6h to remove a template agent of the molecular sieve; then mixing the Beta molecular sieve without the template agent, ammonium chloride and secondary water according to the mass ratio of 1:1:20 to obtain a mixed solution, dropwise adding ammonia water into the mixed solution to adjust the pH of the solution to 10, controlling the water bath temperature to be 80 ℃ and the rotating speed to be 350r/min, stirring and preserving heat for 2 hours; after the heat preservation is finished, carrying out suction filtration, carrying out water system for three times, and drying to obtain a solid phase substance; and (3) repeating the steps twice by replacing the Beta molecular sieve without the template agent with the solid phase substance, and finally roasting the solid phase substance at 550 ℃ for 6 hours to obtain the H-shaped Beta molecular sieve which is marked as the HBeta molecular sieve.

(2) Continuously dripping secondary water into 1g of the HBeta molecular sieve obtained in the step (1) until the molecular sieve is just in a saturated and wet state, and determining that the water absorption capacity corresponding to 1g of the HBeta molecular sieve is 1100 mu L;

0.017g of PdCl₂Respectively and 0.53X 10^-3g、0.71×10^-3g、0.11×10^-2g、0.21×10^-2g、0.64×10^-2g、0.0106g ZnCl₂(wherein the mass ratio of the HBeta molecular sieve to the metal Pd is 1:0.01, and the mass ratios of the Pd to the Zn are 40:1, 30:1, 20:1, 10:1, 3.3:1 and 2:1 respectively), adding the mixture into 1100 mu L of secondary water, and preparing a No. 1-6 precursor salt mixed solution; adding the No. 1-6 precursor salt mixed solution into the HBeta molecular sieve obtained in the step (1) by a liquid transfer gun for multiple times at room temperature, matching an oscillator and stirring while oscillating to uniformly load the precursor salt mixed solution on the molecular sieve to obtain a No. 1-6 sample, and placing the sample in a vacuum drying oven for drying at room temperature;

after grinding sample Nos. 1 to 6, 10 vol% H was added₂-N₂Reducing the mixed gas for 3h at 315 ℃ to obtain the target catalyst, which is respectively named as: pd₄₀Zn/HBeta、Pd₃₀Zn/HBeta、Pd₂₀Zn/HBeta、Pd₁₀Zn/HBeta、Pd_3.3Zn/HBeta、Pd₂Zn/HBeta, which are respectively marked as 1-1, 1-2, 1-3, 1-4, 1-5 and 1-6.

Example 2

A bimetallic catalyst for preparing cyclohexylbenzene by benzene hydrogenation comprises an active component metal Pd, a metal auxiliary agent metal Ni and an HBeta molecular sieve, wherein the metal Pd and the metal Ni are loaded on the HBeta molecular sieve.

The preparation method of the bimetallic catalyst for preparing the cyclohexylbenzene by hydrogenating the benzene comprises the following steps of:

(1) roasting the Beta molecular sieve with the silicon-aluminum ratio of 25 at 550 ℃ for 5h to remove a template agent of the molecular sieve; then mixing the Beta molecular sieve without the template agent, ammonium chloride and secondary water according to the mass ratio of 1:1:10 to obtain a mixed solution, dropwise adding ammonia water into the mixed solution to adjust the pH of the solution to 9, adjusting the water bath temperature to 70 ℃, keeping the rotating speed at 350r/min, stirring and preserving the temperature for 3 hours; after the heat preservation is finished, carrying out suction filtration, carrying out water system for three times, and drying to obtain a solid phase substance; and (3) repeating the steps twice by replacing the Beta molecular sieve without the template agent with the solid phase substance, and finally roasting the solid phase substance at 500 ℃ for 6 hours to obtain the H-type Beta molecular sieve which is marked as the HBeta molecular sieve.

(2) Continuously dripping secondary water into 1g of the HBeta molecular sieve obtained in the step (1) until the molecular sieve is just in a saturated and wet state, and determining that the water absorption capacity corresponding to 1g of the HBeta molecular sieve is 1100 mu L;

0.017g of PdCl₂Respectively with 0.0014g of NiCl₂(wherein the mass ratio of the HBeta molecular sieve to the metal Pd is 1:0.01, and the mass ratio of the Pd to the Ni is 30:1 respectively) is put into 1100 mu L of secondary water to prepare a precursor salt mixed solution; adding the precursor salt mixed solution into the HBeta molecular sieve obtained in the step (1) by a liquid transfer gun for multiple times at room temperature, and stirring while oscillating by matching with an oscillator to uniformly load the precursor salt mixed solution on the molecular sieve to obtain a sample, and placing the sample in a vacuum drying oven for drying at room temperature;

after grinding the above sample, 10 vol% H was used₂-N₂Reducing the mixed gas for 4 hours at 300 ℃ to obtain the target catalyst which is named as Pd₃₀Ni/HBeta。

Example 3

A bimetallic catalyst for preparing cyclohexylbenzene by hydrogenating benzene comprises an active component metal Pd, a metal assistant metal Co and an HBeta molecular sieve, wherein the metal Pd and the metal Co are loaded on the HBeta molecular sieve.

The preparation method of the bimetallic catalyst for preparing the cyclohexylbenzene by hydrogenating the benzene comprises the following steps of:

(1) roasting the Beta molecular sieve with the silicon-aluminum ratio of 30 at 600 ℃ for 4h to remove a template agent of the molecular sieve; then mixing the Beta molecular sieve without the template agent, ammonium chloride and secondary water according to the mass ratio of 1:1:30 to obtain a mixed solution, dropwise adding ammonia water into the mixed solution to adjust the pH of the solution to 10, controlling the water bath temperature to be 90 ℃ and the rotating speed to be 350r/min, stirring and preserving the temperature for 1 h; after the heat preservation is finished, carrying out suction filtration, carrying out water system for three times, and drying to obtain a solid phase substance; and (3) repeating the steps twice by replacing the Beta molecular sieve without the template agent with the solid phase substance, and finally roasting the solid phase substance at 600 ℃ for 4H to obtain the H-type Beta molecular sieve which is marked as the HBeta molecular sieve.

(2) Continuously dripping secondary water into 1g of the HBeta molecular sieve obtained in the step (1) until the molecular sieve is just in a saturated and wet state, and determining that the water absorption capacity corresponding to 1g of the HBeta molecular sieve is 1100 mu L;

0.017g of PdCl₂Respectively with 0.0014g CoCl₂(wherein the mass ratio of the HBeta molecular sieve to the metal Pd is 1:0.01, and the mass ratio of the Pd to the Co is 30:1 respectively) is put into 1100 mu L of secondary water to prepare a precursor salt mixed solution; adding the precursor salt mixed solution into the HBeta molecular sieve obtained in the step (1) by a liquid transfer gun for multiple times at room temperature, and stirring while oscillating by matching with an oscillator to uniformly load the precursor salt mixed solution on the molecular sieve to obtain a sample, and placing the sample in a vacuum drying oven for drying at room temperature;

after grinding the above sample, 10 vol% H was used₂-N₂Reducing the mixed gas for 2 hours at 400 ℃ to obtain the target catalyst which is named as Pd₃₀ Co/HBeta。

Example 4

A bimetallic catalyst for preparing cyclohexylbenzene by benzene hydrogenation comprises an active component metal Pd, a metal auxiliary agent metal Cu and an HBeta molecular sieve, wherein the metal Pd and the metal Cu are loaded on the HBeta molecular sieve.

The preparation method of the bimetallic catalyst for preparing the cyclohexylbenzene by hydrogenating the benzene comprises the following steps of:

(1) roasting the Beta molecular sieve with the silicon-aluminum ratio of 80 at 500 ℃ for 6h to remove a template agent of the molecular sieve; then mixing the Beta molecular sieve without the template agent, ammonium chloride and secondary water according to the mass ratio of 1:1:20 to obtain a mixed solution, dropwise adding ammonia water into the mixed solution to adjust the pH of the solution to 10, controlling the water bath temperature to be 80 ℃ and the rotating speed to be 350r/min, stirring and preserving heat for 2 hours; after the heat preservation is finished, carrying out suction filtration, carrying out water system for three times, and drying to obtain a solid phase substance; and (3) repeating the steps twice by replacing the Beta molecular sieve without the template agent with the solid phase substance, and finally roasting the solid phase substance at 550 ℃ for 6 hours to obtain the H-shaped Beta molecular sieve which is marked as the HBeta molecular sieve.

(2) Continuously dripping secondary water into 1g of the HBeta molecular sieve obtained in the step (1) until the molecular sieve is just in a saturated and wet state, and determining that the water absorption capacity corresponding to 1g of the HBeta molecular sieve is 1100 mu L;

0.017g of PdCl₂Respectively with 0.0014g of CuCl₂(wherein the mass ratio of the HBeta molecular sieve to the metal Pd is 1:0.01, and the mass ratio of the Pd to the Cu is 30:1 respectively) is put into 1100 mu L of secondary water to prepare a precursor salt mixed solution; adding the precursor salt mixed solution into the HBeta molecular sieve obtained in the step (1) by a liquid transfer gun for multiple times at room temperature, and stirring while oscillating by matching with an oscillator to uniformly load the precursor salt mixed solution on the molecular sieve to obtain a sample, and placing the sample in a vacuum drying oven for drying at room temperature;

after grinding the above sample, 10 vol% H was used₂-N₂Reducing the mixed gas for 3 hours at 315 ℃ to obtain the target catalyst which is named as Pd₃₀Cu/HBeta。

Comparative example 1

Comparative example 1 differs from example 1 in that: in comparative example 1, the metallic Zn precursor in step (2) of example 1 was omitted, and the same procedure as in example 1 was repeated to obtain a monometallic catalyst for the hydrogenation of benzene to produce cyclohexyl, which was designated as Pd/HBeta.

Comparative example 2

Comparative example 2 differs from example 1 in that: comparative example 2 PdCl in step (2) of example 1₂Omitted, only add 0.11X 10^-2g ZnCl₂Otherwise, the same procedure as in example 1 gave the final product, designated Zn/HBeta.

Experimental example 1

The catalysts obtained in examples 1 to 4 were characterized by physicochemical properties, with the following results:

XRD analyses were performed on samples nos. 1 to 6 obtained in example 1 and samples obtained in comparative examples 1 and 2, and the structures were as shown in fig. 2, and the samples were substantially represented by zeolite Beta diffraction peaks except that a small peak (belonging to Pd (111) crystal plane) appeared at 2 θ ═ 40.1 °. The XRD patterns of the samples obtained in examples 2 to 4 were compared with HBeta (fig. 3), and all of the samples showed zeolite Beta diffraction peaks.

Pd in example 1₃₀Zn/HBeta is subjected to TEM characterization (FIG. 4 and FIG. 5), FIGS. 4a, 4b and 4c are graphs with three different magnification ratios, and FIGS. 1 to 3 in FIG. 4c are HAADF-STEM images, which show clear grating stripes, the grating spacing is 0.221nm, and the grating stripes correspond to Pd (111) crystal planes. The atom resolved energy dispersive x-ray (EDX) plot (fig. 5) shows that the Pd and Zn elements are uniformly distributed. Randomly counting at least 100 nanoparticles in each sample by surface-area-weighted surface area weighting methodThe average particle size of the Pd nanoparticles in the image was calculated (fig. 5 b). The result shows that the Pd-Zn nano particles are uniformly dispersed and have the average particle size of about 2.5 nm.

When TEM characterization was performed on the samples of examples 2, 3, 4 and comparative example 1 (fig. 6), the Pd and Pd-M (Ni, Co, Cu) nanoparticles were uniformly distributed, the average diameter of the Pd-M nanoparticles was about 3nm (fig. 7, calculated as described in the above paragraph), the Pd nanoparticles were slightly smaller than Pd/HBeta, and the nano-sized active component had a larger specific surface area, which contributed to the improvement of catalytic activity.

XPS analysis (FIG. 8) was performed on samples No. 1 to No. 6 obtained in example 1 and comparative example 1, and it was found that the peak of Pd 3d was shifted to a lower binding energy when different Zn loadings were added. This result indicates that there is an electronic interaction between the Pd and Zn atoms in the Pd-Zn nanocluster, resulting in the Pd being negatively charged or forming a Pd-Zn alloy.

Pd in example 1₃₀XPS analysis (FIG. 9) was carried out on samples of Zn/HBeta, examples 2 to 4, comparative example 1, Pd in comparison to Pd/HBeta (FIG. 9)₃₀The Pd 3d electron binding energy of the M (Zn, Ni, Co, Cu)/HBeta catalyst shows obvious red shift (0.48-0.91 eV), and the doping of M (Zn, Ni, Co, Cu) influences the electron performance of Pd.

Experimental example 2

Application of bimetallic catalyst for preparing cyclohexylbenzene by benzene hydrogenation

0.5g of the catalyst prepared in each of reaction examples 1 to 4 and comparative example 1 was accurately weighed and placed in a reaction vessel, 25mL of benzene (mass ratio of benzene to catalyst: 44:1) was accurately weighed using a 50mL measuring cylinder and rapidly transferred to the reaction vessel, and the reaction vessel was covered with a high-pressure reaction vessel lid. After the high-pressure reaction kettle buckle is screwed down by using the alignment method, the hydrogen main valve is opened, the pressure of the pressure reducing valve is controlled to be 1.0MPa, and simultaneously, soapy water is used for checking whether the gas supply system leaks. And after ensuring that the kettle body has no bubble blowing phenomenon, discharging gas for three times, discharging air from the reaction kettle body, slowly raising the pressure in the high-pressure reaction kettle to 1.0MPa, closing a hydrogen gas inlet valve, and setting the temperature of the reaction kettle to be 200 ℃. When the temperature in the reaction kettle rises to 200 ℃, starting stirring, and setting the rotating speed to be 500rpm min^-1And meanwhile, after the hydrogen pressure is slowly increased to 4.0MPa, the reaction is started for 90 min.

After the reaction is finished, closing the hydrogen feeding valve, closing the stirring, and slowly reducing the pressure in the reaction kettle to normal pressure after the temperature in the reaction kettle is reduced to room temperature. Opening the high-pressure reaction kettle, taking out all reaction products in the kettle into a centrifugal tube at 8000rpm for min^-1And (4) performing centrifugal separation, and taking the supernatant clear liquid for qualitative and quantitative analysis of the reaction product. Qualitative analysis of the reaction products is carried out on a gas chromatography-mass spectrometry (GCMS) instrument, and the positions of the products in the chromatogram are recorded in sequence for further quantitative analysis. The results are shown in tables 1 and 2.

TABLE 1

	Benzene conversion (%)	Cyclohexane yield (%)	Cyclohexylbenzene yield (%)	Cyclohexylbenzene selectivity (%)
					Examples 1 to 1	59.13	36.02	17.05	28.83
Examples 1 to 2	78.05	43.97	22.23	28.48
					Examples 1 to 3	68.47	49.52	13.05	19.06
Examples 1 to 4	68.21	46.93	9.59	14.06
					Practice ofExamples 1 to 5	25.86	13.23	11.38	44.02
Examples 1 to 6	9.60	4.01	6.45	67.18

TABLE 2

The activity data of the catalysts of examples 1-1 to 1-6 for 90min of reaction are shown in Table 1, and the performance is most excellent when the Zn supporting amount is 1/30 wt%, and the yield of cyclohexylbenzene is 22.23%. The results of activity data of examples 2-4 and comparative example 1 in 90min are shown in Table 2, the cyclohexylbenzene yield of the single metal catalyst is only 9.58%, and the product obtained by adding only the metal promoter Zn has no catalytic activity. The addition of the metal auxiliary agents (Zn, Ni, Co and Cu) enables the yield of the cyclohexylbenzene of the bimetallic catalyst to be better than that of a single metal catalyst, and results show that the bimetallic catalyst obtained after the metal auxiliary agents are added has stronger catalytic activity.

In summary, the bimetallic catalyst for preparing cyclohexylbenzene by benzene hydrogenation provided by the invention has the advantages that metal Pd is an active component, Zn (Ni, Co, Cu) is a metal assistant, and the addition of the metal assistant enables the catalyst to obtain more intermediate product cyclohexene, so that the yield of the target product cyclohexylbenzene is improved. The active component and the metal auxiliary agent in the prepared bimetallic catalyst are in a nano-particle state and are uniformly dispersed on the carrier molecular sieve, so that the catalytic activity can be effectively improved. The catalyst is used in the catalysis process, and particularly, the metal auxiliary agent Zn is added, so that the yield of the cyclohexylbenzene obtained by catalysis can reach 22.23 percent, and a good technical effect is achieved.

The above embodiments are only preferred embodiments of the present invention, and the protection scope of the present invention is not limited thereby, and any insubstantial changes and substitutions made by those skilled in the art based on the present invention are within the protection scope of the present invention.