CN110898853B - Catalyst for preparing cyclohexanone by phenol hydrogenation and preparation method thereof - Google Patents

Abstract

The invention discloses a catalyst for preparing cyclohexanone by phenol hydrogenation and a preparation method thereof, wherein the method comprises the following steps: (1) rapidly mixing and refluxing an acid and a Beta molecular sieve, centrifugally filtering after the reaction is finished, then mixing a Zr salt or a Sn salt with a reaction product, filtering, drying and roasting to obtain an activated strong Lewis solid acid material, wherein the material has at least one pore size distribution at 1-10 nm, and in addition, the material contains certain alkalinity; (2) pd salt is prepared into solution and added into the material to obtain the catalyst, and the catalyst simultaneously has high specific surface area, strong L acid and high metal dispersity. The catalyst provided by the invention has the advantages of low cost, simple preparation method, high catalytic activity and conversion frequency (TOF) higher than 100h^‑1The conversion rate of phenol and the selectivity of cyclohexanone can reach more than 99 percent, the product still shows good stability after a cycle test, and the reaction product and the catalyst are easy to be reactedAnd (5) separating.

Description

A kind of catalyst for preparing cyclohexanone by hydrogenation of phenol and preparation method thereof

technical field

The invention relates to a catalyst for preparing cyclohexanone by hydrogenation of phenol and a preparation method thereof, belonging to the technical field of catalyst preparation.

Background technique

Phenol (Phenol, C ₆ H ₅ OH) is a colorless needle-like crystal with a special odor, poisonous, and an important organic chemical raw material. raw material. Phenol is present in coal tar, so coal tar is one of the industrial sources of phenol.

The phenol method is the earliest method for industrial production of cyclohexanone. It has the advantages of less side reactions, simple product separation and purification process, and high product purity. It is divided into two types: gas phase method and liquid phase method. The gas-phase hydrogenation method usually uses 3 to 5 reactors in series with supported Pd as the catalyst. This process requires the vaporization of raw material phenol (heat of vaporization: 69 kJ/mol) and solvent methanol (heat of vaporization: 35.2 kJ/mol). The consumption is high, and the catalyst is also prone to coke deposition during use, resulting in a decrease in activity. The selective hydrogenation of phenol to cyclohexanone is an optional route, including one-step and two-step methods. The two-step process involves hydrogenation of phenol to cyclohexanol, followed by hydrogenation to cyclohexanone. The one-step method can directly hydrogenate phenol to cyclohexanone. Compared with the two-step method, the one-step method is more energy-efficient and lower in operation cost, and at the same time avoids the problem of difficult separation of the cyclohexanone-phenol and cyclohexanol-phenol azeotropes of the series products.

The current one-step phenol hydrogenation catalyst (CN101709027B) usually needs to use a liquid Lewis acid catalyst, and the reaction solvent is often an organic solvent, causing environmental pollution. More importantly, liquid Lewis acid has subsequent problems such as separation of product and catalyst. In contrast, solid Lewis acid can replace liquid Lewis acid as a reaction catalyst for phenol hydrogenation, effectively solving the problem of separation between catalyst and product, but solid Lewis acid catalysts have the disadvantages of low catalytic efficiency, expensive supports, and high consumption of precious metals (active metal palladium). Relatively high proportion of phenol). In addition, the specific surface area of the conventional solid Lewis acid carrier is low, the precious metal is easily lost, and the cycle stability is poor. Catalysis Science & Technology journal Catal. Sci. Technol. , 2014,4, 3555-3569 published a method for preparing cyclohexanone by hydrogenation of phenol, the reaction solvent is water, the palladium/raw material phenol molar ratio is 0.02~0.7, the reaction The conversion rate is around 80%.

SUMMARY OF THE INVENTION

The present invention aims to provide a catalyst for preparing cyclohexanone by hydrogenation of phenol and a preparation method thereof. The present invention adopts Lewis acid/Brønsted acid high heteroatom-containing molecular sieve as a carrier-supported Pd metal catalyst, which can significantly improve the performance of phenol hydrogenation. Intrinsic catalytic activity and conversion of Pd catalysts.

The invention provides a catalyst for preparing cyclohexanone by hydrogenation of phenol. The catalyst is obtained by mixing molecular sieve and salt containing Zr or Sn, filtering and drying to obtain an activated strong solid Lewis acid material. The ratio of Lewis acid content measured by desorption is not higher than 1:0.85, the material has at least one pore size distribution at 1~10nm, and the material contains a certain alkalinity; the material is used as a carrier, and the highly dispersed metal Pd is loaded to prepare phenol Aqueous hydrogenation catalyst, which has high specific surface area, strong L acid and high metal dispersion at the same time. On the basis of a large number of experiments, the present invention unexpectedly finds that the molecular sieve modified with Zr and/or Sn is used to support Pd metal, and can be used as an excellent solid Lewis acid phenol hydrogenation catalyst after washing and atmospheric roasting treatment; the reaction raw materials are water, palladium When the molar ratio of phenol to raw material is 0.005, the reaction conversion rate can reach more than 80%, which greatly improves the reaction efficiency.

The invention provides a preparation method of a catalyst for preparing cyclohexanone by hydrogenation of phenol, comprising the following steps:

(1) Quickly mix technical-grade Beta molecular sieve, acid, and distilled water to obtain a reaction mixture. In this reaction mixture, the mass ratio of technical-grade Beta molecular sieve: acid: distilled water is 1: (20~40): (10~20), and after heating Reflux treatment under conditions, cooling to room temperature after the reaction is finished, and intermediate product A is obtained after washing and drying;

(2) Add the intermediate product A prepared in step (1) into a zirconium salt or tin salt solution containing Zr or Sn with a concentration of 0.01~0.5mol/L, and the mass ratio of the product A and the salt is 1:(0.01~0.5 ), stir evenly at room temperature, then transfer the above mixture to a polytetrafluoroethylene hydrothermal kettle, react at a constant temperature of 80~200 °C for 6~24 hours, isolate the product, and then alternately wash with deionized water and ethanol at 60~120 ℃ drying, and calcining at 400-600 ℃ for 4-10 h in a single gas or mixed atmosphere to obtain a composite carrier;

(3) Preparation of catalyst: dissolving palladium chloride, palladium nitrate, palladium acetate or palladium tetraammine nitrate in deionized water, stirring at room temperature to prepare a solution, then adding the configured solution to the composite carrier obtained in step (2) In the solution, immersion at 20~50°C for 1~5h, then dry at 80~100°C for 2~6h, and calcinate the obtained solid at 400~600°C in an air atmosphere for 4~6h and activate it under a hydrogen atmosphere.

The noble metal Pd is highly dispersed on the catalyst carrier obtained in step (2).

The acid described in the above step (1) is at least one of nitric acid, sulfuric acid, hydrochloric acid or oxalic acid; the molecular sieve is a Beta molecular sieve with a BEA structure, and the silicon to aluminum ratio is between 20 and 200.

The Zr salt described in the above step (2) may be one of zirconium oxychloride, zirconium carbonate, zirconium oxynitrate, zirconium sulfate or zirconium acetate; the Sn salt may be tin tetrachloride or stannous chloride.

The atmosphere described in the above step (3) can be one or more of hydrogen, argon, nitrogen, ammonia or air.

The activation temperature described in the above step (3) is 150-500 °C, and the activation time is 1-5 h.

The invention provides a catalyst prepared by the above method, the specific surface area of the prepared catalyst is not less than 300m ² /g, and the Pd metal loading of the catalyst is 0.1-3% of the catalyst mass, preferably 0.5-1.5%.

The present invention also provides the application of the above catalyst in the aqueous hydrogenation of phenol.

In the phenol aqueous hydrogenation reaction, the reaction hydrogen pressure is 0.1-0.5MPa, the reaction temperature is 20-80°C, and the reaction time is 1-8h.

Beneficial effects of the invention: the invention uses water as the raw material, the utilization rate of the precious metal of the catalyst is more than doubled, the metal particles are evenly dispersed, the catalytic active sites are many, etc., the active metal can be stably adsorbed on the carrier, and the catalytic intrinsic activity is High, catalytic conversion frequency can reach more than 100h ^-1 , and the conversion rate and selectivity of phenol can reach more than 99%, and complete conversion is achieved.

The catalyst and preparation method provided by the invention have low cost, simple preparation method, catalytic activity TOF is higher than 100h ^-1 , and the reaction product and the catalyst are easy to separate.

Description of drawings

Figure 1: XRD spectrum of the multi-stage porous Beta molecular sieve obtained in Example 1 of the present invention.

Figure 2: N ₂ adsorption and desorption curve and DFT pore size distribution curve of the multi-stage porous Beta molecular sieve obtained in Example 1 of the present invention.

Figure 3: SEM spectrum of the multi-stage porous Beta molecular sieve obtained in Example 1 of the present invention.

Detailed ways

The following embodiments are only preferred technical solutions of the present invention, and are not intended to limit the present invention. Various modifications and variations of the present invention are possible for those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

According to the present invention, the crystal phase diagram of X-ray diffraction (XRD) is obtained by Shimadzu XRD7000 X measurement, and the test conditions are: Cu target, Kα radiation, Ni filter, super energy detector, tube voltage 40KV, tube current 40mA;

According to the present invention, the specific surface area is measured by using a _quantachrome NOVA 1200e pore size distribution analyzer at a liquid nitrogen temperature (77K) to measure the static N adsorption and desorption curve of the sample, and the specific surface area is P/P0 = 0.05~0.35 range. The adsorption curve was fitted.

Example 1

A kind of phenol hydrogenation prepares cyclohexanone catalyst and preparation method thereof, comprises the steps:

Preparation of carrier: under stirring conditions, weigh 15 g of industrial-grade H-Beta molecular sieve, 500 g of concentrated nitric acid, and 150 g of distilled water, and mix them evenly. The product, 0.16 g of ZrOCl ₂ ·8H ₂ O and 15 g of distilled water were mixed uniformly, mixed in a hydrothermal kettle at 80 °C for 24 h, filtered and dried with suction; the obtained product was calcined at 550 °C for 4 h in an air atmosphere to obtain a carrier.

Catalyst preparation:

Dissolve 0.0168 g of PdCl ₂ in the hydrochloric acid solution, add 10 mL of distilled water; weigh 1 g of the above carrier in a 50 mL beaker, and add 20 mL of distilled water. After the two were evenly mixed, they were stirred at room temperature for 2 h. Rotary steam at 50°C, and then put it in a hydrogenation furnace for activation. The activation conditions are: 10% H ₂ /Ar, reduction temperature 350°C, heating rate 5°C/min, reduction time 1 h, and the obtained sample is recorded as Z-1.

The XRD characterization results of Z-1 are shown in Figure 1, and there are strong BEA characteristic diffraction peaks, confirming that it is a Beta crystal structure. The SEM results of Z-1 are shown in Figure 2, from which it can be seen that the catalyst has a regular morphology and a high degree of dispersion. Based on the analysis of the DFT pore size distribution curve in Figure 3, Z-1 molecular sieve has at least two pore size distributions in the range of 1 to 10 nm.

Example 2

A kind of phenol hydrogenation prepares cyclohexanone catalyst and preparation method thereof, comprises the steps:

Preparation of the vector:

Under stirring conditions, 15 g of industrial grade H-Beta molecular sieve, 500 g of concentrated sulfuric acid, and 50 g of distilled water were weighed and mixed uniformly. Reflux for 15 h in an oil bath at 105 °C, and then cool to room temperature to obtain the product; mix the above product, 0.16 g of ZrOCl ₂ ·8H ₂ O and 15 g of distilled water, and mix them in a hydrothermal kettle at 80 °C for 6 h. The obtained product was calcined in an oxygen atmosphere at 550 °C for 4 h to obtain a carrier.

Catalyst preparation:

Dissolve 0.0168 g of PdCl ₂ in the hydrochloric acid solution, add 10 mL of distilled water; weigh 1 g of the above carrier in a 50 mL beaker, and add 20 mL of distilled water. After the two were evenly mixed, they were stirred at room temperature for 2 h. Rotary steam at 50°C, and then put it in a hydrogenation furnace for activation. The activation conditions are: 10% H ₂ /Ar, reduction temperature 350°C, heating rate 5°C/min, reduction time 1 h, and the obtained sample is recorded as Z-2.

Example 3

A kind of phenol hydrogenation prepares cyclohexanone catalyst and preparation method thereof, comprises the steps:

Preparation of the vector:

Under stirring conditions, 15 g of industrial-grade H-Beta molecular sieve, 500 g of concentrated sulfuric acid, and 150 g of distilled water were weighed and mixed uniformly. Reflux for 15 h under the condition of 105 ℃ oil bath, cool to room temperature to obtain the product; mix the above product with ZrOCl ₂ ·8H ₂ O 0.16 g and 15 g of distilled water, mix evenly, treat in a 180 ℃ hydrothermal kettle for 24 h, and filter with suction Drying; the obtained product was calcined at 550 °C for 4 h in a nitrogen atmosphere to obtain a carrier.

Catalyst preparation:

Dissolve 0.0168 g of PdCl ₂ in the hydrochloric acid solution, add 20 mL of distilled water; weigh 1 g of the above carrier in a 50 mL beaker, and add 20 mL of distilled water. After the two were evenly mixed, they were stirred at room temperature for 2 h. Rotary steam at 50 °C, and then put it in a hydrogenation furnace for activation. The activation conditions are: 20% H ₂ /Ar, reduction temperature of 350 °C, heating rate of 5 °C/min, reduction time of 1 h, and the obtained sample is recorded as Z-3.

Example 4

A kind of phenol hydrogenation prepares cyclohexanone catalyst and preparation method thereof, comprises the steps:

Preparation of the vector:

Under stirring conditions, 15 g of industrial grade H-Beta molecular sieve, 500 g of 36wt.% hydrochloric acid, and 300 g of distilled water were weighed and mixed uniformly. Reflux for 15 h in an oil bath at 125 °C, and then cool to room temperature to obtain the product; mix the above product with ZrOCl ₂ ·8H ₂ O 0.16 g and 15 g of distilled water, and heat them at 200 °C for 24 h with suction, filter and dry. Dry; the obtained product was calcined at 550 °C in an ammonia atmosphere for 4 h to obtain a carrier.

Catalyst preparation:

Dissolve 0.0168 g of PdCl ₂ in the hydrochloric acid solution, add 10 mL of distilled water; weigh 1 g of the above carrier in a 50 mL beaker, and add 20 mL of distilled water. After the two were evenly mixed, they were stirred at room temperature for 2 h. Rotary steam at 50°C, and then put it in a hydrogenation furnace for reduction. The reduction conditions are: 10% H ₂ /Ar, reduction temperature of 350°C, heating rate of 5°C/min, reduction time of 1 h, and the obtained sample is recorded as Z-4.

Example 5

A kind of phenol hydrogenation prepares cyclohexanone catalyst and preparation method thereof, comprises the steps:

Preparation of the vector:

Under stirring conditions, 15 g of industrial-grade H-Beta molecular sieve, 500 g of concentrated sulfuric acid, and 150 g of distilled water were weighed and mixed uniformly. Reflux for 15 h in an oil bath at 105 °C, and cool to room temperature to obtain the product; mix the above product, 0.16 g of ZrOCl ₂ ·8H ₂ O and 15 g of distilled water, and treat them in a hydrothermal kettle at 120 °C for 24 h, and filter them with suction. Drying; the obtained product was calcined at 550 °C for 4 h in an air atmosphere to obtain a carrier.

Catalyst preparation:

Dissolve 0.0232 g of PdCl ₂ in the hydrochloric acid solution, add 10 mL of distilled water; weigh 1 g of the above carrier in a 50 mL beaker, and add 20 mL of distilled water. After the two were evenly mixed, they were stirred at room temperature for 2 h. Rotary steam at 50°C, and then put it in a hydrogenation furnace for reduction. The reduction conditions are: 10% H ₂ /Ar, reduction temperature of 350°C, heating rate of 5°C/min, reduction time of 1 h, and the obtained sample is recorded as Z-5.

Example 6

A kind of phenol hydrogenation prepares cyclohexanone catalyst and preparation method thereof, comprises the steps:

Preparation of the vector:

Under stirring conditions, 15 g of industrial-grade H-Beta molecular sieve, 500 g of concentrated sulfuric acid, and 150 g of distilled water were weighed and mixed uniformly. Reflux for 15 h in an oil bath at 105 °C, and cool to room temperature to obtain the product; mix the above product, 0.16 g of tin tetrachloride and 15 g of distilled water, and treat in a hydrothermal kettle at 100 °C for 24 h, then filter and dry. ; The obtained product was calcined at 550 °C for 4 h in an air atmosphere to obtain a carrier.

Catalyst preparation:

Dissolve 0.0168 g of PdCl ₂ in the hydrochloric acid solution, add 10 mL of distilled water; weigh 1 g of the above carrier in a 50 mL beaker, and add 20 mL of distilled water. After the two were evenly mixed, they were stirred at room temperature for 2 h. Rotary steam at 50°C, and then put it in a hydrogenation furnace for reduction. The reduction conditions are: 10% H ₂ /Ar, reduction temperature of 350°C, heating rate of 5°C/min, reduction time of 1 h, and the obtained sample is recorded as Z-6.

Example 7

Application example:

The catalysts prepared in Examples 1 to 6 were used in the reaction of phenol hydrogenation to prepare cyclohexanone, and their catalytic performance was measured.

The test method is as follows: add 0.5g phenol, 20mL deionized water and 0.5g catalyst into a 100mL hydrogenation reaction kettle, and after complete sealing, use high-purity nitrogen for degassing for 5 min, and keep 0.5MPa high-purity hydrogen during the reaction. The stirring speed was 800 rpm, heating to 80° C., and the reaction time was 5 h. After the reaction finishes, cool to room temperature with ice-water bath, centrifuge, filter, and the reaction solution is detected by Agilent gas chromatography to measure the transformation efficiency of phenol and the selectivity of cyclohexanone, the results are shown in Table 1.

Table 1 List of catalytic reaction results of the catalysts of Examples 1 to 6

It will be apparent to those skilled in the art that the present invention is not limited to the details of the above-described exemplary embodiments, but that the present invention may be embodied in other specific forms without departing from the spirit or essential characteristics of the invention. Therefore, the embodiments are to be regarded in all respects as illustrative and not restrictive, and the scope of the invention is to be defined by the appended claims rather than the foregoing description, which are therefore intended to fall within the scope of the claims. All changes within the meaning and scope of the equivalents of , are included in the present invention.

In addition, it should be understood that although this specification is described in terms of embodiments, not each embodiment only includes an independent technical solution, and this description in the specification is only for the sake of clarity, and those skilled in the art should take the specification as a whole , the technical solutions in each embodiment can also be appropriately combined to form other implementations that can be understood by those skilled in the art.

Claims (10)

1. a preparation method of the catalyzer of phenol hydrogenation to prepare cyclohexanone, is characterized in that comprising the following steps: (1) The reaction mixture is obtained by rapidly mixing technical grade molecular sieve, acid and distilled water. In this reaction mixture, the mass ratio of technical grade molecular sieve: acid: distilled water is 1: (20~40): (10~20), under heating conditions Reflux treatment, cooling to room temperature after the reaction, washing and drying to obtain intermediate product A; The molecular sieve is a Beta molecular sieve with a BEA structure, and the silicon-to-aluminum ratio is between 20 and 200; (2) Add the intermediate product A prepared in step (1) into a zirconium salt or tin salt solution containing Zr or Sn with a concentration of 0.01 to 0.5 mol/L, stir evenly at room temperature, and then transfer the above mixture to polytetrafluoroethylene In the ethylene hydrothermal kettle, 80~200℃ constant temperature reaction for 6~24h, the product is separated, then washed alternately with deionized water and ethanol, dried at 60~120℃, and roasted at 400~600℃ in single gas or mixed atmosphere atmosphere 4~10 h, a composite carrier is obtained, and the mass ratio of product A and salt is 1:(0.01~0.5); (3) Preparation of catalyst: dissolving palladium chloride, palladium nitrate, palladium acetate or palladium tetraammine nitrate in deionized water, stirring at room temperature to prepare a solution, then adding the configured solution to the composite carrier obtained in step (2) , immersion at 20~50°C for 1~5h, then dry at 80~100°C for 2~6h, the obtained solid was calcined at 400~600°C in an air atmosphere for 4~6h and activated under a hydrogen atmosphere to obtain cyclohexanone by hydrogenation of phenol. catalyst. 2 . The method for preparing a catalyst for preparing cyclohexanone by hydrogenation of phenol according to claim 1 , wherein the acid described in step (1) is at least one of nitric acid, sulfuric acid, hydrochloric acid or oxalic acid. 3 . 3. The preparation method of a catalyst for preparing cyclohexanone by hydrogenation of phenol according to claim 1, wherein the Zr salt described in step (2) is zirconium oxychloride, zirconium carbonate, zirconium oxynitrate, and zirconium sulfate Or one of zirconium acetate; Sn salt is tin tetrachloride or stannous chloride. 4. The preparation method of the catalyst for preparing cyclohexanone by hydrogenation of phenol according to claim 1, wherein the atmosphere described in the step (2) is one of argon, nitrogen, ammonia or air or several. 5. The preparation method of the catalyst for preparing cyclohexanone by hydrogenation of phenol according to claim 1, characterized in that: the concentration of the Pd salt described in the step (3) after being dissolved in deionized water is 0.001 to 0.1 mol/ L. 6. The preparation method of the catalyst for preparing cyclohexanone by hydrogenation of phenol according to claim 1, wherein the reduction temperature in the activation process in the step (3) is 150～500°C, and the reduction time is 1～5 h . 7. a catalyst for preparing cyclohexanone by hydrogenation of phenol obtained by the preparation method described in any one of claims 1 to 6, is characterized in that: the specific surface area of the prepared catalyst is not less than 300 m ² /g, The Pd metal loading of the catalyst is 0.1~3% of the catalyst mass; the catalyst has strong L acid and high metal dispersion. 8. The catalyst for preparing cyclohexanone by hydrogenation of phenol according to claim 7, wherein the Pd metal loading of the catalyst is 0.5 to 1.5% of the catalyst mass. 9. the application of a catalyst according to any one of claims 7 to 8 for the aqueous hydrogenation of phenol. 10. application according to claim 9, is characterized in that: in described phenol water-phase hydrogenation reaction, reaction hydrogen pressure is 0.1～0.5MPa, reaction temperature is 20～80 ℃, and reaction time is 1～8h; The catalytic conversion frequency is higher than 100h ^-1 , and it still shows good stability after the cycle test, and the reaction product and the catalyst are easy to separate.

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