A metal / MoO x / Bifunctional Molecular Sieve Catalysts, Their Preparation Methods and Applications

Abstract

This invention relates to the fields of catalytic chemistry and waste plastic resource utilization, and discloses a metal / MoO2 method. x / Molecular sieve bifunctional catalyst, its preparation method, and its application. The preparation method includes the following steps: ion exchange of molecular sieve with ammonium nitrate solution; addition of completely dissolved molybdenum salt, ultrasonic dispersion, filtration, washing, and drying; addition of completely dissolved urea and metal salt, hydrothermal synthesis, and drying; filtration, washing, and drying to obtain metal / MoO x / Molecular sieve precursors, after calcination and reduction, yield metallic / MoO x / Bifunctional molecular sieve catalyst. The bifunctional catalyst of this invention has a simple preparation process, high catalytic activity, excellent selectivity and good stability, convenient reaction operation, mild conditions, and is suitable for industrial application; MoO x It facilitates hydrogenation and deoxygenation, and the metal sites contribute to catalytic hydrogenation; it enables efficient recycling of resources and effectively alleviates environmental pollution problems.

Description

Technical Field

[0001] This invention relates to the fields of catalytic chemistry and waste plastic resource utilization, specifically to a metal / MoO2 compound. x / Bifunctional molecular sieve catalysts, their preparation methods and applications Background Technology

[0002] The recycling and reuse of polycarbonate (PC) plastic waste is mainly achieved through physical and chemical methods. Traditional physical recycling methods, such as landfilling, incineration, and mechanical recycling processes, uncontrollably release bisphenol A (BPA), causing large amounts of BPA to enter the ecosystem. Furthermore, the multiple extrusion granulation processes during mechanical recycling affect the molecular weight of PC, thus reducing the performance of recycled PC plastics. Chemical degradation methods break down PC into monomers or products, thereby achieving the recycling of waste PC. Previous researchers have done extensive work on PC degradation, such as patent CN116239449B, which describes a method for preparing a solid superalkali and using it to catalytically degrade waste PC into bisphenol compounds and carbonate compounds. Patent CN118388305A first uses CuO-ZnO as a catalyst to catalyze the degradation of polycarbonate into the monomer bisphenol A, and then uses Pt / Al2O3 and trifluoromethanesulfonate as catalysts to further hydrodeoxygenate bisphenol A into 2,2-dicyclohexylpropane. Propane-2,2-diyldicyclohexane is a high-demand transportation fuel with higher density and higher volumetric calorific value. Therefore, hydrodeoxygenation (HDO) of polycarbonate (PC) plastics could provide a new route for the production of sustainable aviation fuel (SAF). However, there are few single-catalyst systems for the convenient and direct hydrodeoxygenation-hydrogenation of polycarbonate to 2,2-dicyclohexylpropane under mild conditions, which remains a significant challenge.

[0003] In summary, the existing problems in the conversion of waste plastic polycarbonate, such as reaction step load, harsh reaction conditions, low conversion rate, and low product selectivity, are technical problems that urgently need to be solved. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a metal / MoO x / Bifunctional molecular sieve catalysts, their preparation methods, and applications, with the technical solutions as follows:

[0005] A metal / MoO x The preparation method of the molecular sieve bifunctional catalyst includes the following steps:

[0006] S1. Molecular sieve support is added to ammonium nitrate solution for ion exchange. The solid precipitate is dried to obtain ion-exchanged molecular sieve support. The molecular sieve support is one or more of Y, Beta, ZSM-5, mordenite, and SAPO. The mass-to-volume ratio between molecular sieve support and ammonium nitrate solution is (5-10) g: (200-500) ml.

[0007] S2. Add molybdenum salt to a mixed solution of water and ethanol at a volume ratio of (1:1) to (1:3). After the molybdenum salt is completely dissolved, add the ion-exchanged molecular sieve support obtained in step S1 to the above solution. The mass ratio of molecular sieve support to molybdenum salt is 2:(0.05-0.1). Then, ultrasonically disperse, filter, and wash the product. Place the product in a vacuum drying oven for vacuum drying. Calcine the dried solid product to obtain MoO. x / Molecular sieve support; the molybdenum salt is one or more of sodium molybdate, ammonium molybdate, molybdenum acetylacetonate, and molybdenum chloride;

[0008] S3. Add the metal salt to a mixed solution of water and ethanol in a volume ratio of (1:1) to (1:3), then add urea. After the urea and metal salt are completely dissolved, add the MoO obtained in step S2. x / Molecular sieve support, the mixture is transferred to a hydrothermal synthesis reactor, and dried in a drying oven to obtain a solid product; MoO x The mass ratio of molecular sieve carrier, metal salt, and urea is 1:(0.1-0.5):(0.3-0.9); the metal salt is one or more of ruthenium chloride, ruthenium acetylacetonate, nickel nitrate, nickel sulfate, nickel chloride, copper nitrate, copper chloride, and copper sulfate.

[0009] S4. Filter, wash, and dry the solid product obtained in step S3 to obtain metal / MoO. x The molecular sieve precursor was calcined under a N2 atmosphere, and then the atmosphere was changed to Ar / H2 for reduction to obtain the metal / MoO. x / Bifunctional molecular sieve catalyst.

[0010] Furthermore, the drying temperature in steps S1 to S4 is 60–100°C; the hydrothermal synthesis temperature in step S3 is 80–100°C; and the Ar / H2 reduction temperature in step S4 is 300–460°C.

[0011] Furthermore, step S2 involves calcining at 550°C for 3 hours; step S4 involves calcining at 500°C for 3 hours.

[0012] Furthermore, the ion exchange in step S1 is performed three times.

[0013] A metal / MoO x / Molecular sieve bifunctional catalyst, composed of a metal / MoO2 as described above x The bifunctional molecular sieve catalyst was prepared by a specific method.

[0014] Based on the above-described metal / MoO x / Application of molecular sieve bifunctional catalyst in the tandem hydrogenation-deoxygenation of polycarbonate to polycyclic alkane chemicals: Under reaction conditions with or without solvent, waste polycarbonate plastic and catalyst are mixed at a mass ratio of (2:1) to (20:1) and reacted at a temperature of 180 to 280°C and a hydrogen pressure of 1 to 5 MPa for 2 to 8 hours; if a solvent is available, the amount of solvent added is 10 to 20 ml, and the solvent is one or more of n-hexane, n-heptane, n-octane, and dodecane.

[0015] Compared with the prior art, the present invention has the following main advantages:

[0016] 1. The catalyst preparation process of this invention is simple, using molecular sieves as a support, and firstly introducing MoO2. x Subsequently, a bifunctional catalyst was prepared by loading metal components. It has high catalytic activity, excellent selectivity and good stability. The reaction is convenient and the conditions are mild, making it suitable for industrial application.

[0017] 2. In the catalyst preparation process of the present invention, MoO x The introduction of metals helps to promote the hydrogenation and deoxygenation of the -OC(=O)-O- groups in polycarbonate (PC), achieving efficient depolymerization of polycarbonate (PC) and significantly reducing the generation of coke; the metal sites catalyze the hydrogenation step in subsequent reactions.

[0018] 3. The catalytic system of the present invention can achieve near-complete conversion of polycarbonate (PC) at 180°C, with a yield of over 90% for the target product propane-2,2-diyldicyclohexane monomer. Propane-2,2-diyldicyclohexane can be used directly as a high-density fuel or as an additive for other aviation kerosene.

[0019] 4. The preparation method of the present invention not only realizes the efficient recycling of resources, but also effectively alleviates environmental pollution problems, and has broad practical application prospects. Attached Figure Description

[0020] Figure 1 A roadmap for the one-step conversion of waste plastic polycarbonate into polycyclic alkane chemicals via a series of hydrogenation deoxygenation-hydrogenation processes;

[0021] Figure 2 The total ion chromatogram of the liquid product and the mass spectrum of the main compounds obtained by GC / MS in Example 1 are shown. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Example 1

[0023] Weigh 7g of Beta molecular sieve and add it to 200ml of 1M ammonium nitrate solution for three ion exchanges. Filter and dry for later use. Weigh 0.05g of ammonium molybdate solution and add it to 50ml of a 1 / 1 mixture of water and ethanol. Stir to dissolve, then add 2g of ion-exchanged Beta, followed by ultrasonic dispersion for 3h. Filter, wash, and vacuum dry. Calcine the dried solid product at 550℃ for 3h to obtain MoO. x / Beta. Next, weigh 0.1g of ruthenium chloride and 0.3g of urea and add them to 50ml of a mixture of water and ethanol (volume ratio 1:1). Stir to dissolve, then add 1g of MoO. x The mixture was then transferred to a stainless steel hydrothermal synthesis reactor (80–100°C) and placed in a drying oven at a constant temperature (60–100°C) for 8–10 h. The resulting solid was then filtered, washed, and dried to obtain Ru / MoO₂. x The / Beta precursor was calcined at 500°C in a N2 atmosphere for 3 hours, followed by reduction at 300-460°C using Ar / H2 for 2 hours to obtain Ru / MoO. x / Beta bifunctional catalyst. Example 2

[0024] The difference from Example 1 is that the added molecular sieve is ZSM-5 type molecular sieve, resulting in a metal / MoO₂ x / A bifunctional molecular sieve catalyst is denoted as Ru / MoO x / ZSM-5. Example 3

[0025] The difference from Example 1 is that 0.5 g of nickel nitrate was added, resulting in a metal / MoO₂ x / A bifunctional molecular sieve catalyst is denoted as Ni / MoO x / Beta. Example 4

[0026] The difference from Example 1 is that 0.1 g of ruthenium chloride and 0.05 g of nickel nitrate were added to obtain the metal / MoO x / A bifunctional molecular sieve catalyst is denoted as RuNi / MoO x / Beta. Example 5

[0027] The difference from Example 1 is that 0.1 g of ammonium molybdate was added, resulting in a metal / MoO₂ x / A bifunctional molecular sieve catalyst is denoted as RuNi / 1MoO x / Beta. Example 6

[0028] The difference from Example 1 is that ammonium molybdate is not added, resulting in a metal / MoO₂ x / A bifunctional molecular sieve catalyst is denoted as Ru / Beta.

[0029] The catalysts prepared in Examples 1 to 6 were used in the hydrogenation reaction of polycarbonate (PC):

[0030] Reaction conditions: First, weigh 0.1 g of catalyst and place it in a high-pressure reactor. Then, add 0.2 g of polycarbonate (PC) and 15 g of n-heptane to the reactor. Replace the air in the apparatus with N2, and inject hydrogen gas until the reaction pressure reaches 4 MPa. The reaction temperature is 180°C. o C, reaction time 4 h, liquid phase products were analyzed by Bruck 450-GC gas chromatograph and Agilent 7890 / 5973 quadrupole gas chromatograph / mass spectrometer.

[0031] Under the same reaction conditions, the conversion rates and products of the highly active dehydrogenation catalysts for the hydrogenation of polycarbonate (PC) prepared in Examples 1 to 6 are shown in Table 1.

[0032] Table 1. Overview of Catalytic Effects of Catalysts in Each Example

[0033] ;

[0034] As shown in Table 1, this catalytic system can achieve near-complete conversion of PC at 180℃, with a yield of over 90% for the target product, propane-2,2-diyldicyclohexane monomer. Propane-2,2-diyldicyclohexane can be directly used as a high-density fuel or as an additive in other aviation kerosene. The catalyst preparation process of this invention is simple, exhibiting high catalytic activity, excellent selectivity, and good stability. The reaction operation is convenient and the conditions are mild, making it suitable for industrial application. This method not only achieves efficient resource recycling but also effectively alleviates environmental pollution problems, demonstrating broad practical application prospects.

[0035] Additionally: the reaction pathway of PC is as follows Figure 1As shown, firstly, H2 is activated at the Ru sites of the catalyst, thereby generating active hydrogen ( ) in MoO x / Attacks the CO bond of the ester bond in the PC structure with the assistance of the acid sites of the molecular sieve. In Ru and MoO x With the synergistic effect of the molecular sieve support, the ester bond is cleaved to form bisphenol A monomer. Subsequently, H2 dissociates at the Ru site on the metal, and the dissociated hydrogen is transferred to the aromatic ring through the metal-support interface, causing the aromatic ring of bisphenol A to be attacked and undergo a series of hydrogenation reactions. The resulting alcohol undergoes a hydrogenation-deoxygenation reaction at the metal-acid dual site, resulting in the sequential removal of OH groups on the ring and their conversion to C15.

[0036] The analytical results of gas chromatography-mass spectrometry (GC / MS) are as follows: Figure 2 As shown, this further proves Ru / MoO x The high efficiency of the / Beta catalyst is demonstrated. The figure shows that three main products are generated, all cycloalkanes: isopropylcyclohexane (C9) 6.4%, tert-butylcyclohexane (C10) 3.1%, and propane-2,2-diyldicyclohexane (C15) 90.5%, with almost no other impurities. Propane-2,2-diyldicyclohexane (C15) has great potential as a high-density fuel; therefore, the catalyst developed in this study can effectively upgrade PC to jet fuel-based cycloalkanes, providing an efficient pathway for the effective utilization of PC.

[0037] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the protection scope of the present invention.

Claims

1. A metal / MoO x process for the preparation of a metal / MoO The method comprises the following steps: S1. Ion exchange is carried out by adding a molecular sieve carrier into an ammonium nitrate solution, and solid precipitates are dried to obtain an ion-exchanged molecular sieve carrier; The molecular sieve carrier is one or more of Y, Beta, ZSM-5, mordenite and SAPO; the mass-to-volume ratio between the molecular sieve carrier and the ammonium nitrate solution is (5-10) g:(200-500) ml; S2. The molybdenum salt is added to a mixed solution of water and ethanol with a volume ratio of (1:1) to (1:3). After the molybdenum salt is completely dissolved, the ion-exchanged molecular sieve carrier obtained in step S1 is added to the above solution, and the mass ratio between the molecular sieve carrier and the molybdenum salt is 2:(0.05-0.1). Then, ultrasonic dispersion, suction filtration, and washing are performed, and the product is placed in a vacuum drying box for vacuum drying. After the dried solid product is calcined, MoO x / molecular sieve carrier is obtained. The molybdenum salt is one or more of sodium molybdate, ammonium molybdate, molybdenum acetylacetate, and molybdenum chloride. S3. The metal salt is added to a mixed solution of water and ethanol in a volume ratio of (1:1) to (1:3), then urea is added, and after the urea and the metal salt are completely dissolved, the MoO x / molecular sieve carrier, the mixture is transferred to a hydrothermal synthesis kettle, dried in a drying box to obtain a solid product; MoO x / molecular sieve carrier, the mass ratio between the metal salt, urea is 1:(0.1-0.5):(0.3-0.9); the metal salt is one or more of ruthenium chloride, ruthenium acetylacetone, nickel nitrate, nickel sulfate, nickel chloride, copper nitrate, copper chloride, copper sulfate; S4. The solid product obtained in step S3 is filtered, washed, and dried to obtain a metal / MoOx / molecular sieve precursor. The precursor is then calcined under a N2 atmosphere and reduced by converting the atmosphere to Ar / H2 to obtain the metal / MoOx / molecular sieve precursor. x / Bifunctional molecular sieve catalyst.

2. A metal / MoO x A process for the preparation of a metal / MoO The drying temperature of the steps S1 to S4 is 60-100℃; the hydrothermal synthesis temperature of the step S3 is 80-100℃; and the Ar / H2 reduction temperature of the step S4 is 300-460℃.

3. A metal / MoO x A method for preparing a metal / MoO The step S2 is calcined at 550℃ for 3 hours; and the step S4 is calcined at 500℃ for 3 hours.

4. A metal / MoO x A method for preparing a bifunctional catalyst of metal / MoO The ion exchange of the step S1 is performed for 3 times.

5. A metal / MoO x bifunctional catalyst comprising a metal and a molecular sieve, characterized in that, A metal / MoO x / zeolite bifunctional catalyst prepared by the method of any of claims 1-4.

6. A metal / MoO x The use of a bifunctional catalyst of metal / MoO Under the reaction condition with or without a solvent, polycarbonate waste plastics and a catalyst are mixed in a mass ratio of (2:1) to (20:1), and are reacted at a temperature of 180-280℃ and a hydrogen pressure of 1-5 MPa for 2-8 hours; if the solvent is used, the solvent is added in an amount of 10-20 ml, and the solvent is one or more of n-hexane, n-heptane, n-octane and dodecane.

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