Catalyst for preparing cyclohexylbenzene by benzene hydroalkylation and preparation method and application thereof
阅读说明：本技术 苯加氢烷基化制备环己基苯的催化剂及其制备方法和应用 (Catalyst for preparing cyclohexylbenzene by benzene hydroalkylation and preparation method and application thereof ) 是由 彭智昆 李剑鹏 刘仲毅 杜康健 马君君 于 2021-09-01 设计创作，主要内容包括：本发明属于苯加氢烷基化制备环己基苯用的双功能催化剂,该催化剂中金属Pd作为活性组分,分子筛作为载体,黏合剂为Al-(2)O-(3),采用金属Pd负载于两种不同位置,第一种负载在Hβ分子筛上,第二种负载在Al-(2)O-(3)黏合剂上,得到催化剂中金属活性位与分子筛酸性位间距离处于不同尺寸接近度。本发明还公开了上述催化剂的应用,该催化剂用于苯加氢烷基化制备环己基苯中,金属Pd负载在Al-(2)O-(3)黏合剂上,负载量0.8％时,制备的催化剂,催化得到的环己基苯收率可达24.1％,取得了良好的技术效果。(The present invention belongs to a bifunctional catalyst for preparing cyclohexylbenzene by benzene hydrogenation alkylation, in said catalyst metal Pd is used as active component, molecular sieve is used as carrier, adhesive is Al 2 O 3 The method adopts metal Pd loaded on two different positions, wherein the first metal Pd is loaded on an H beta molecular sieve, and the second metal Pd is loaded on Al 2 O 3 On the adhesive, the distances between the metal active sites and the acid sites of the molecular sieve in the obtained catalyst are in different size proximity. The invention also discloses application of the catalyst, the catalyst is used for preparing cyclohexylbenzene by benzene hydroalkylation, and metal Pd is loaded on Al 2 O 3 When the loading capacity of the catalyst on the adhesive is 0.8%, the yield of the cyclohexylbenzene catalyzed by the prepared catalyst can reach 24.1%, and a good technical effect is achieved.)
1. A preparation method of a catalyst for preparing cyclohexylbenzene by benzene hydroalkylation is characterized by comprising the following steps:
(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 H Beta molecular sieve;
(2) the metal Pd active component is loaded at two different positions, wherein the first is that the metal Pd is loaded on the H beta molecular sieve; second, metal Pd is loaded on Al2O3On the adhesive.
The first method comprises the following steps: dipping the H beta molecular sieve obtained in the step (1) in a metal precursor solution, drying the dipped H beta molecular sieve, and then mixing with Al2O3Fully grinding the adhesive, and then carrying out reduction reaction to obtain a final product;
and the second method comprises the following steps: metal precursor solution, impregnated with Al2O3A binder, and Al impregnated in the binder2O3Drying, fully grinding with the H beta molecular sieve obtained in the step (1), and carrying out reduction reaction to obtain a final product.
2. The process of claim 1 for the preparation of a catalyst for the hydroalkylation of benzene to cyclohexylbenzene, wherein: the metal active component is noble metal Pd.
3. The process of claim 1 for the preparation of a catalyst for the hydroalkylation of benzene to cyclohexylbenzene, wherein: the molecular sieve is an H-shaped Beta molecular sieve with the silicon-aluminum ratio of 25-150.
4. The process of claim 1 for the preparation of a catalyst for the hydroalkylation of benzene to cyclohexylbenzene, wherein: the adhesive is Al2O3。
5. The process of claim 1 for the preparation of a catalyst for the hydroalkylation of benzene to cyclohexylbenzene, wherein: in the step (2), the metal active component is loaded at two different positions, wherein the first position is that metal Pd is loaded on an H beta molecular sieve; second, metal Pd is loaded on the adhesive Al2O3The above.
6. The process of claim 1 for the preparation of a catalyst for the hydroalkylation of benzene to cyclohexylbenzene, wherein: and (3) carrying out reduction reaction in the step (2) in a mixed gas atmosphere with the volume ratio of nitrogen to hydrogen being 9:1, wherein the reaction temperature is 200-400 ℃, and the reaction time is 2-4 h.
7. The process of claim 1 for the preparation of a catalyst for the hydroalkylation of benzene to cyclohexylbenzene, 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 deionized 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 H Beta molecular sieve.
8. The method for preparing the bimetallic catalyst for preparing cyclohexylbenzene by benzene hydroalkylation according to claim 7, wherein the roasting temperature for removing the template agent in the step (1) is 500-600 ℃ and the time is 4-6 h.
Technical Field
The invention belongs to the technical field of catalysis, and relates to a catalyst for preparing cyclohexylbenzene by benzene hydroalkylation and a preparation method and application thereof.
Background
The cyclohexylbenzene is a fine chemical with high added value, has a boiling point as high as 240.12 ℃, can be used as a high-boiling-point solvent or one of raw materials for synthesizing TFT liquid crystal materials, and can also be used as an additive to be applied to organic electrolyte of a lithium battery to improve the overcharge resistance of the battery. In addition, the peroxidation can prepare phenol and cyclohexanone, and the product phenol is an important chemical product and can be used as a raw material for synthesizing several important products such as phenolic resin, caprolactam, alkylphenol and the like.
The synthesis method of the cyclohexylbenzene comprises the following steps: (1) benzene and cyclohexene alkylation method (2) biphenyl selective hydrogenation method (3) benzene hydrogenation alkylation method. The first two routes have high yield, but the raw material cost is high, so the method is not suitable for large-scale industrial production. The method for preparing the cyclohexylbenzene by the benzene hydroalkylation method has the advantages of rich benzene source, low cost, simple process, environment-friendly synthesis process and the like, so the method is suitable for large-scale production. However, the production line has the defects of poor catalyst performance and poor selectivity of the cyclohexylbenzene. Therefore, it is necessary to design a high performance catalyst for the hydroalkylation of benzene to produce cyclohexylbenzene.
Disclosure of Invention
The invention aims to provide a catalyst for preparing cyclohexylbenzene by benzene hydroalkylation and a preparation method and application thereof.
The catalyst for preparing cyclohexylbenzene by benzene hydroalkylation is characterized in that noble metal is used as an active component, a molecular sieve is used as a carrier, and Al is used as the carrier2O3Is an adhesive; the active component is one of noble metal simple substances Ru, Pt and Pd, and the molecular sieve is an H-type Beta molecular sieve with the silicon-aluminum ratio of 25-150.
A preparation method of a catalyst for preparing cyclohexylbenzene by benzene hydroalkylation is characterized by comprising the following specific steps:
(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 H Beta molecular sieve;
(2) active ingredient loading
The metal Pd active component is loaded at two different positions, wherein the first is that the metal Pd is loaded on the H beta molecular sieve; second, metal Pd is loaded on Al2O3On the adhesive.
The first method comprises the following steps: dipping the H beta molecular sieve obtained in the step (1) in a metal precursor solution, drying the dipped H beta molecular sieve, and then mixing with Al2O3Fully grinding the adhesive, and then carrying out reduction reaction to obtain a final product;
and the second method comprises the following steps: : metal precursor solution, impregnated with binder Al2O3Then impregnating Al2O3Drying, fully grinding the dried product with the H beta molecular sieve obtained in the step (1), and carrying out reduction reaction to obtain a final product;
further, the reduction reaction in the step (2) is carried out in a mixed gas atmosphere with the volume ratio of nitrogen to hydrogen being 9:1, the reaction temperature is 200-400 ℃, 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 deionized 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 500-600 ℃ for 4-6H to obtain the H-type Beta molecular sieve which is marked as the H Beta 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 invention provides a preparation method of a bifunctional catalyst for preparing cyclohexylbenzene by benzene hydroalkylation, wherein the distance between an active component site and a molecular sieve acidic site in the catalyst obtained by the method is in a nanometer level, the catalytic activity can be improved, and the catalyst has the reaction temperature of 200 ℃ and the hydrogen pressure of 40Mpa, the reaction time is 90min, and the metal Pd is loaded on Al2O3On the adhesive, the loading capacity of metal Pd is 0.8%, the yield of the cyclohexylbenzene obtained by catalysis can reach 24.1%, and a better technical effect is achieved.
Drawings
FIG. 1 is an XRD pattern of a catalyst prepared after loading of metallic Pd;
FIG. 2 is a TEM image of a catalyst prepared by loading metal Pd on H beta molecular sieve;
FIG. 3 is a diagram of metal Pd supported on Al2O3TEM image of the catalyst prepared above;
Detailed Description
The invention is further described with reference to the following examples, but the scope of the invention is not limited thereto.
Example 1
The metal loading was determined to be 1%, i.e., 1g of catalyst corresponded to 0.01g of Pd, and the mass of the palladium tetraammine chloride monohydrate corresponded to 1g of catalyst was 0.0248g, based on the Pd content in the palladium tetraammine chloride monohydrate being 40.4%.
A method for preparing a catalyst for preparing cyclohexylbenzene by benzene hydroalkylation comprises the following steps:
(1) pretreatment of
1.1 roasting the H beta molecular sieve with the silicon-aluminum ratio of 25 at 550 ℃ for 5 hours to remove a template agent in the molecular sieve;
1.2 Water absorption: continuously dripping secondary water into 1g of the H beta molecular sieve obtained in the step S1.1 until the molecular sieve is just in a saturated and wet state, and determining that the water absorption capacity corresponding to the 1g H beta molecular sieve is 1 mL;
1.3, 0.0248g Pd (NH)3)4Cl2·H2Adding O into 1mL of secondary water to prepare a metal precursor salt solution;
(2) loading of metal active components:
the metal Pd active component is loaded at two different positions, wherein the first is that the metal Pd is loaded on the H beta molecular sieve; second, metal Pd is loaded on Al2O3On the adhesive.
2.1 first:
2.1.1 adding 0.5g of the H beta molecular sieve obtained in the step 1.1 into a crucible;
2.1.2 absorbing 0.5mL of the metal precursor salt solution obtained in the step 1.3 by using a liquid-transferring gun, slowly dripping the solution into a crucible, stirring by using a glass rod, and placing the crucible on an oscillator for oscillation so that the metal precursor salt solution is uniformly dispersed in the molecular sieve;
2.1.3 repeating the step 2.1.2 until 1mL of the precursor salt solution obtained in the step 1.3 is completely dripped, and uniformly loading the metal precursor salt solution on the molecular sieve through stirring and oscillating for multiple times;
2.1.4 placing the loaded sample in a vacuum drying oven at 80 ℃ for drying and grinding;
2.1.5 mixing the powder obtained in step 2.1.4 with 0.5gAl2O3Fully grinding in an agate mortar, placing in a tubular furnace, and reducing for 3 hours at 315 ℃ in a nitrogen-hydrogen mixed gas (nitrogen and hydrogen, the volume ratio is 9: 1) atmosphere to obtain the target catalyst.
2.2 second:
2.2.1 mixing 0.5g of adhesive Al2O3Adding into a crucible;
2.2.2 absorbing 0.5mL of the metal precursor salt solution obtained in the step 1.3 by using a liquid-transferring gun, slowly dropping the solution into a crucible, stirring by a glass rod, and placing the crucible on an oscillator for oscillation, so that the metal precursor salt solution is in the adhesive Al2O3Uniformly dispersing;
2.2.3 repeating the step 2.2.2 until the 1mL of the metal precursor salt solution obtained in the step 1.3 is dripped, and stirring and oscillating for multiple times to enable the metal precursor salt solution to be uniformly loaded on Al2O3The above step (1);
2.2.4 placing the loaded sample in a vacuum drying oven at 80 ℃ for drying and grinding;
2.2.5 grinding the powder obtained in the step 2.2.4 and 0.5g H beta molecular sieve in an agate mortar fully, placing the powder in a tubular furnace, and reducing the powder for 3 hours at 315 ℃ in an atmosphere of nitrogen-hydrogen mixed gas (nitrogen and hydrogen, the volume ratio is 9: 1) to obtain the target catalyst.
Example 2
The difference from the first load of embodiment 1 is that: the metal loading was 0.8%, otherwise the same as in the first loading mode of example 1.
Example 3
The difference from the first load of embodiment 1 is that: the metal loading was 0.5%, otherwise the same as in the first loading mode of example 1.
Example 4
The difference from the first load of embodiment 1 is that: the metal loading was 0.2%, otherwise the same as in the first loading mode of example 1.
Comparative example 1
The difference from example 1 is that: and (3) directly loading the active component of the metal Pd on the H beta molecular sieve, putting the powder obtained in the step (2.1.4) into a tubular furnace, and reducing for 3 hours at 315 ℃ in the atmosphere of nitrogen-hydrogen mixed gas (nitrogen and hydrogen, the volume ratio is 9: 1) to obtain the target catalyst. The rest of the procedure was the same as in the first loading method of example 1.
Example 5
The second load is different from the second load of embodiment 1 in that: the metal loading was 0.8%, otherwise the same as in the second loading mode of example 1.
Example 6
The second load is different from the second load of embodiment 1 in that: the metal loading was 0.5%, otherwise the same as in the second loading mode of example 1.
Example 7
The second load is different from the second load of embodiment 1 in that: the metal loading was 0.2%, otherwise the same as in the second loading mode of example 1.
Comparative example 2
The difference from example 1 is that: the active component of metal Pd is directly loaded on Al2O3And (3) placing the powder obtained in the step (2.2.4) into a tubular furnace, and reducing for 3 hours at 315 ℃ in the atmosphere of nitrogen-hydrogen mixed gas (nitrogen and hydrogen, the volume ratio is 9: 1) to obtain the target catalyst. Otherwise, the second loading method of example 1 was the same.
Product structural characterization
From the left diagram of fig. 1, XRD patterns of catalysts prepared by supporting metallic Pd on H β molecular sieve (i.e., examples 1-4) show that the rest of samples basically show Beta zeolite diffraction peaks except a small peak (belonging to Pd (111) crystal plane) appearing at 2 θ ═ 40.1 °. Meanwhile, the Pd peak at 40.1 ° becomes sharper and sharper as the metal loading increases.
FIG. 1 shows the right diagram, metal Pd supported on Al2O3The XRD patterns of the catalysts prepared above (i.e., example 1, examples 5 to 8) show that the remaining samples substantially exhibit zeolite Beta diffraction peaks, except for the occurrence of a small peak (belonging to Pd (111) crystal plane) at 2 θ of 40.1 °. Meanwhile, the Pd peak at 40.1 ° becomes sharper and sharper as the metal loading increases.
From the TEM image of the catalyst prepared by loading metallic Pd on H β molecular sieve in fig. 2, it can be seen that: the metal particles in the catalyst are small and are relatively uniformly distributed on the H beta molecular sieve; the metal Pd is loaded on Al from figure 32O3The TEM image of the catalyst prepared above shows that: the metal particles in the catalyst are small and relatively uniformly distributed in Al2O3The above step (1);
TABLE 1
TABLE 2
Activity evaluation
25mL of benzene and 0.5g of catalyst are put into a 100mL high-pressure reaction kettle, and the mixture is continuously stirred and reacted for 90min under the conditions of stirring speed of 500r/min, 200 ℃ and hydrogen pressure of 4 Mpa. Analyzing the product composition by a gas chromatograph, calculating the relative content of cyclohexane, cyclohexylbenzene and benzene by peak area ratio correction by an FID detector, comparing with a standard curve, and calculating the conversion rate of benzene, the selectivity of cyclohexylbenzene and the yield.
The data of the reactivity of the catalyst prepared by supporting metallic Pd on H β molecular sieve are shown in table 1. As can be seen from Table 1: the data results of example 1 (first loading) -4 and comparative example 1 show that the better the performance, the higher the cyclohexylbenzene yield, with increasing loading of metallic Pd; wherein the direct metal is directly loaded on the molecular sieve and the comparison example 1, the performance is poor, and when the loading amount of the metal Pd is 1%, the performance is best, the conversion rate of benzene is 33.1%, and the yield of the cyclohexylbenzene is as high as 18.2%.
Metal Pd supported on Al2O3The reactivity data of the catalysts prepared on the binder are shown in table 2. As can be seen from Table 2: the results of the data for example 1 (second loading), and examples 5-8, and comparative example 2 show that the cyclohexylbenzene yield increases with increasing loading of metallic Pd, wherein the catalyst performs best with 0.8% metallic Pd loading, with 83.5% benzene conversion and 24.1% cyclohexylbenzene yield. In contrast, metal Pd is directly supported on Al2O3The catalyst prepared on the binder has poor performance.
From tables 1 and 2, it can be obtained that metallic Pd is supported on Al2O3The catalyst prepared on the adhesive (second load mode) has the best performance when the load of the metal Pd reaches 0.8 percent, and the yield of the cyclohexylbenzene reaches 24.1 percent.