Preparation method of metal-loaded molecular sieve catalyst for producing phenol through cyclohexanone dehydrogenation and application thereof

Abstract

The application discloses a preparation method of a metal-loaded molecular sieve catalyst for producing phenol through cyclohexanone dehydrogenation, and comprises the following steps: (1) calcining, tabletting, and sieving a molecular sieve to obtain a catalyst carrier, and loading the catalyst carrier on a bed layer of a fixed bed reactor; (2) dissolving a precursor of a noble metal in water, and ultrasonic treating to obtain a noble metal precursor solution; the noble metal is Pt or Pd; (3) using a liquid high-pressure pump to spray the noble metal precursor solution into the fixed bed at a certain flow rate, setting the bed layer temperature to be 200-400 DEG C, recovering the liquid through condensation, taking out the solid, drying, and then calcining to obtain the metal-loaded molecular sieve catalyst. Meanwhile, the application also discloses application of the catalyst in producing phenol through cyclohexanone dehydrogenation. The catalyst prepared by the application can improve the dispersion degree of metal atoms, and can achieve the same reaction effect under the condition of lower metal loading in the same reaction.

Description

Technical Field

[0001] This invention belongs to the field of phenol preparation technology, specifically relating to a method for preparing a metal-supported molecular sieve catalyst for the dehydrogenation of cyclohexanone to phenol and its application. Background Technology

[0002] The process of oxidative decomposition of cyclohexylbenzene to produce cyclohexanone and phenol consists of two main products, one of which is cyclohexanone, an organic compound with the chemical formula C6H10. 10 O represents a saturated cyclic ketone where the carbonyl carbon atom is enclosed in a six-membered ring. It is a colorless, transparent liquid with an earthy odor; when trace amounts of phenol are present, it develops a minty smell. Industrially, it is primarily used as a raw material and solvent in organic synthesis; for example, it can dissolve nitrocellulose, coatings, and paints. Phenol is an organic compound with the chemical formula C6H5OH. It is a colorless, needle-like crystal with a characteristic odor, and is toxic. It is an important raw material for the production of certain resins, bactericides, preservatives, and pharmaceuticals (such as aspirin), with global demand exceeding 10 million tons per year.

[0003] In the process of oxidative decomposition of cyclohexylbenzene to produce cyclohexanone and phenol, cyclohexylbenzene can be oxidized and decomposed to produce the chemicals phenol and cyclohexanone. The prices of these two chemicals will fluctuate with the corresponding supply and demand in the market. If the interconversion of these two products can be realized and their product distribution can be controlled, higher profits can be obtained from the price fluctuations of cyclohexanone and phenol.

[0004] Platinum and palladium are two noble metals widely used in chemical reactions. Platinum-palladium catalysts exhibit high catalytic activity and selectivity, capable of catalyzing a variety of chemical reactions and improving reaction efficiency and yield, especially in hydrogenation and dehydrogenation reactions. However, since both platinum and palladium catalysts are noble metal catalysts, if the impregnation method, the most widely used method in industrial production, is used to prepare platinum-palladium catalysts, it will result in uneven distribution of many noble metal particles under the same loading conditions, with a smaller specific surface area of ​​exposed active sites, making the metal prone to agglomeration and deactivation.

[0005] Therefore, how to correct these shortcomings, improve the utilization rate of precious metals, and reduce the cost of catalysts is an urgent problem to be solved. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention discloses a method for preparing a metal-supported molecular sieve catalyst for the dehydrogenation of cyclohexanone to phenol and its application. The prepared catalyst exhibits higher metal dispersion on the support.

[0007] A method for preparing a metal-supported molecular sieve catalyst for the dehydrogenation of cyclohexanone to phenol includes the following steps: (1) The molecular sieve is calcined, pressed into tablets, and sieved to obtain a catalyst support, which is then loaded onto the bed of a fixed-bed reactor. (2) Dissolve the precursor of the precious metal in water and sonicate it to obtain a solution of the precursor of the precious metal; the precious metal is Pt or Pd. (3) The noble metal precursor solution is pumped into a fixed bed at a certain flow rate using a liquid high-pressure pump. The bed temperature is set to 200-400℃. The liquid is condensed and recovered, the solid is taken out, dried and calcined to obtain the metal-supported molecular sieve catalyst.

[0008] Preferably, in the metal-supported molecular sieve catalyst, the metal loading is 1-20 wt%, based on the mass fraction of the metal in the catalyst.

[0009] Preferably, the molecular sieve is any one of ZSM-5, ZSM-11, Silicalite-1, or MOR.

[0010] Preferably, the flow rate in step (3) is 0.1-1 mL / min.

[0011] Preferably, the precursor of the noble metal is chloroplatinic acid, ammonium hexachloroplatinate, or palladium chloride.

[0012] Preferably, the drying conditions are drying at 100-110℃ for 12-18 hours; the calcination conditions are calcination at 500-600℃ for 4-6 hours.

[0013] Preferably, the sieving process involves passing through a 40-60 mesh sieve.

[0014] Preferably, the ultrasonic treatment time is 20-30 minutes.

[0015] A method for producing phenol by dehydrogenation of cyclohexanone, characterized in that: a catalyst, cyclohexanone, and a solvent are loaded into a high-pressure reactor and reacted at 180-250°C for 2-2.5 h. After cooling, the solid and liquid are separated; wherein the catalyst is prepared by the above preparation method; and the mass ratio of cyclohexanone to catalyst is 3:1.

[0016] Preferably, the solvent is acetonitrile.

[0017] Advantages of this invention: (1) The preparation method provided by the present invention involves calcining the support and then heating the precursor solution in a fixed bed to allow the hot steam to be used for support treatment and metal loading in the reactor. This allows metal atoms to be loaded on the framework and improves the dispersion of metal atoms. In the same reaction, the catalyst can achieve the same reaction effect under a lower metal loading condition. (2) The catalyst obtained by this invention can be used to produce phenol by dehydrogenation of cyclohexanone, so it can be used to control the ratio of the two products in the oxidative decomposition reaction of cyclohexylbenzene, thus generating greater economic benefits. Implementation

[0018] Example 1 A method for preparing a metal-supported molecular sieve catalyst for the dehydrogenation of cyclohexanone to phenol includes the following steps: (1) Take a certain amount of ZSM-5 molecular sieve, calcine it at 550℃ for 6 hours, press it into tablets, sieve it, and pass it through a 40-60 mesh sieve to obtain a catalyst support. Take 2g of the catalyst support and fill it on the bed of a fixed bed reactor. (2) Dissolve 0.17 g palladium chloride PdCl2 in 20 mL of water and sonicate for 20 min to obtain a noble metal precursor solution; (3) Use a liquid high-pressure pump with Q v The noble metal precursor solution was pumped into a fixed bed at a flow rate of 0.2 mL / min, while the bed temperature was set to 200°C for carrier treatment and metal loading. Simultaneously, the liquid was condensed and recovered. After completion, the solid was removed, dried at 100°C for 18 h, and then calcined at 550°C for 6 h to obtain a metal-supported molecular sieve catalyst, denoted as Pd / ZSM-5 molecular sieve catalyst, with a Pd loading of 5.0% by mass of the catalyst.

[0019] Example 2 A method for preparing a metal-supported molecular sieve catalyst for the dehydrogenation of cyclohexanone to phenol includes the following steps: (1) Take a certain amount of ZSM-5 molecular sieve, calcine it at 550℃ for 6 hours, press it into tablets, sieve it, and pass it through a 40-60 mesh sieve to obtain a catalyst support. Take 2g of the catalyst support and fill it on the bed of a fixed bed reactor. (2) Dissolve 0.13g of chloroplatinic acid H2PtCl6 in 20 mL of water and sonicate for 20 min to obtain a noble metal precursor solution; (3) Use a liquid high-pressure pump with Q v The noble metal precursor solution was pumped into a fixed bed at a flow rate of 0.1 mL / min, while the bed temperature was set to 300 °C for carrier treatment and metal loading. Simultaneously, the liquid was condensed and recovered. After completion, the solid was removed, dried at 100 °C for 18 h, and then calcined at 550 °C for 6 h to obtain a metal-supported molecular sieve catalyst, denoted as Pt / ZSM-5 molecular sieve catalyst, with a Pt loading of 3.0% by mass of the catalyst.

[0020] Example 3 A method for preparing a metal-supported molecular sieve catalyst for the dehydrogenation of cyclohexanone to phenol includes the following steps: (1) Take a certain amount of MOR molecular sieve, calcine it at 550℃ for 6 hours, press it into tablets, sieve it, and pass it through a 40-60 mesh sieve to obtain a catalyst support. Take 2g of the catalyst support and fill it on the bed of a fixed bed reactor. (2) Dissolve 0.40 g of ammonium hexachloroplatinate in 20 mL of water and sonicate for 20 min to obtain a noble metal precursor solution; (3) Use a liquid high-pressure pump with Q v The noble metal precursor solution was pumped into a fixed bed at a flow rate of 1.0 mL / min, while the bed temperature was set to 400°C for carrier treatment and metal loading. Simultaneously, the liquid was condensed and recovered. After completion, the solid was removed, dried at 100°C for 18 h, and then calcined at 550°C for 6 h to obtain a metal-supported molecular sieve catalyst, denoted as Pt / MOR molecular sieve catalyst, with Pt loading of 9.5% by mass of the catalyst.

[0021] Example 4 A method for preparing a metal-supported molecular sieve catalyst for the dehydrogenation of cyclohexanone to phenol includes the following steps: (1) Take a certain amount of Silicalite-1 molecular sieve, calcine it at 550℃ for 6 hours, press it into tablets, sieve it, and pass it through a 40-60 mesh sieve to obtain a catalyst support. Take 2g of the catalyst support and fill it on the bed of a fixed bed reactor. (2) Dissolve 0.04 g palladium chloride PdCl2 in 20 mL of water and sonicate for 20 min to obtain a noble metal precursor solution; (3) Use a liquid high-pressure pump with Q v The noble metal precursor solution was pumped into a fixed bed at a flow rate of 0.3 mL / min, while the bed temperature was set to 200 °C for carrier treatment and metal loading. Simultaneously, the liquid was condensed and recovered. After completion, the solid was removed, dried at 100 °C for 18 h, and then calcined at 550 °C for 6 h to obtain a metal-supported molecular sieve catalyst, denoted as Pb / Silicalite-1 molecular sieve catalyst, with a Pb loading of 1.2% by mass of the catalyst.

[0022] Example 5 A method for preparing a metal-supported molecular sieve catalyst for the dehydrogenation of cyclohexanone to phenol includes the following steps: (1) Take a certain amount of ZSM-11 molecular sieve, calcine it at 500℃ for 6 hours, press it into tablets, sieve it, and pass it through a 40-60 mesh sieve to obtain a catalyst support. Take 2g of the catalyst support and fill it on the bed of a fixed bed reactor. (2) Dissolve 0.67 g palladium chloride PdCl2 in 20 mL of water and sonicate for 30 min to obtain a noble metal precursor solution; (3) Use a liquid high-pressure pump with Q v The noble metal precursor solution was pumped into a fixed bed at a flow rate of 0.6 mL / min, while the bed temperature was set to 270 °C for carrier treatment and metal loading. Simultaneously, the liquid was condensed and recovered. After completion, the solid was removed, dried at 100 °C for 12 h, and then calcined at 500 °C for 6 h to obtain a metal-supported molecular sieve catalyst, denoted as Pd / ZSM-5 molecular sieve catalyst, with Pd loading of 20% by mass of the catalyst.

[0023] Comparative Example 1 A certain amount of ZSM-5 molecular sieve was calcined at 550℃ for 6 hours, pressed into tablets, sieved, and passed through a 40-60 mesh sieve to obtain the catalyst support. Then, the conventional impregnation and loading method was used, as follows: Weigh 0.21 g of chloroplatinic acid hexahydrate (H2PtCl6·6H2O) and dissolve it in 20 mL of water. Sonicate for 20 min, then add it dropwise to 2 g of the carrier. Stir at room temperature for 12 h, then dry at 100 °C for 18 h, and then calcine at 550 °C for 6 h to obtain a molecular sieve, denoted as Pt / ZSM-5-B molecular sieve catalyst, with a Pt loading of 5%.

[0024] 1. Catalytic performance testing 3 g of cyclohexanone, 1 g of catalyst, and 4 mL of acetonitrile were weighed and placed into a high-pressure reactor. The reactor was then sealed and mechanically stirred at 200 °C (300 rpm) for 2 h. After cooling, the solid and liquid were separated. The solid catalyst was recovered, and the liquid product was analyzed by liquid chromatography. The results are shown in Table 1. Table 1 Reaction Results

[0025] 2. Metal dispersion detection The dispersion of metal is obtained by the ratio of the total number of metal atoms on the edge surface to the total number of metal atoms on the catalyst. The specific calculation formula is as follows, and the calculation results are shown in Table 2.

[0026] Where D represents the dispersion of the metal, V represents the volume of gas consumed by the sample, which can be calculated by a TCD detector, m represents the mass of the catalyst, w is the mass fraction (i.e., loading amount) of the loaded metal in the catalyst, and M is the relative atomic mass of the loaded metal. Table 2. Dispersion of metals in catalysts .

Claims

1. The application of a metal-supported molecular sieve catalyst in the dehydrogenation of cyclohexanone to phenol, characterized in that: Specifically, the catalyst, cyclohexanone, and solvent are loaded into a high-pressure reactor and reacted at 180-250℃ for 2-2.5 hours. After cooling, the solid and liquid phases are separated, and the liquid product is collected. The mass ratio of cyclohexanone to catalyst is 3:

1. The catalyst is prepared by the following method: (1) The molecular sieve is calcined, pressed into tablets, and sieved to obtain a catalyst support, which is then loaded onto the bed of a fixed-bed reactor. (2) Dissolve the precursor of the precious metal in water and sonicate it to obtain a solution of the precursor of the precious metal; the precious metal is Pt or Pd. (3) The noble metal precursor solution is pumped into a fixed bed at a certain flow rate using a liquid high-pressure pump, while the bed temperature is set to 200-400℃. The liquid is condensed and recovered, the solid is taken out, dried and calcined to obtain the metal-supported molecular sieve catalyst. The precursor of the noble metal is chloroplatinic acid, ammonium hexachloroplatinate, or palladium chloride.

2. The application of the metal-supported molecular sieve catalyst according to claim 1 in the dehydrogenation of cyclohexanone to phenol, characterized in that: In the metal-supported molecular sieve catalyst, the metal loading is 1-20% based on the mass fraction of the metal in the catalyst.

3. The application of the metal-supported molecular sieve catalyst according to claim 2 in the dehydrogenation of cyclohexanone to phenol, characterized in that: The molecular sieve is any one of ZSM-5, ZSM-11, Silicalite-1, or MOR.

4. The application of the metal-supported molecular sieve catalyst according to claim 3 in the dehydrogenation of cyclohexanone to phenol, characterized in that: The flow rate in step (3) is 0.1-1 mL / min.

5. The application of the metal-supported molecular sieve catalyst according to claim 4 in the dehydrogenation of cyclohexanone to phenol, characterized in that: The drying conditions are drying at 100-110℃ for 12-18 hours; the calcination conditions are calcination at 500-600℃ for 4-6 hours.

6. The application of the metal-supported molecular sieve catalyst according to claim 5 in the dehydrogenation of cyclohexanone to phenol, characterized in that: The sieving process involves passing through a 40-60 mesh sieve.

7. The application of the metal-supported molecular sieve catalyst according to claim 6 in the dehydrogenation of cyclohexanone to phenol, characterized in that: The ultrasonic treatment time is 20-30 minutes.

8. The application of the metal-supported molecular sieve catalyst according to claim 1 in the dehydrogenation of cyclohexanone to phenol, characterized in that: The solvent is acetonitrile.

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