A method for preparing a Pt / WO3-ZrO2 catalyst based on a supercritical crystallization method and applications thereof

Abstract

The application provides a method for preparing a Pt / WO3-ZrO2 catalyst based on a supercritical crystallization method and application, and comprises the following steps: adding a composite solid acid of WO3-ZrO2 into a platinum source solution and mixing, placing the obtained mixture into a supercritical reaction kettle, introducing carbon dioxide gas, and performing a supercritical crystallization reaction; after naturally cooling to room temperature, drying and calcining, the Pt / WO3-ZrO2 catalyst is obtained. The Pt / WO3-ZrO2 catalyst is prepared by using a supercritical fluid technology for the first time, compared with a traditional impregnation method, the method is simple in operation, short in reaction time, good in dispersion performance of active components, high in catalytic activity, the prepared catalyst has high glycerol conversion rate and 1,3-propanediol selectivity, the loss of the active components is delayed, and the catalyst has high repeated use performance.

Description

Technical Field

[0001] This invention relates to the field of 1,3-propanediol preparation technology, and in particular to a method and application for preparing Pt / WO3-ZrO2 catalyst based on supercritical crystallization. Background Technology

[0002] Glycerin is a byproduct of biodiesel production; for every ton of biodiesel produced, 0.1 tons of glycerin can be co-produced, and there is currently an overcapacity of glycerin. The purification and further processing of crude glycerin are costly and difficult to dispose of, with uncontrolled emissions in many areas easily causing environmental pollution. 1,3-Propanediol has a wide range of applications, including the preparation of solvents, antifreeze, and daily chemical and pharmaceutical products. It is also used as a monomer in the synthesis of polyurethane, polypropylene terephthalate, and polypropylene naphthaleneacetic acid (PPD), among other polymer materials.

[0003] Currently, the main methods for producing 1,3-propanediol include microbial fermentation, ethylene oxide synthesis, and acrolein synthesis. Microbial fermentation, using glycerol and glucose as raw materials and relying on recombinant *E. coli* to produce 1,3-propanediol, is a green and mild process, but its yield is low, product separation costs are high, and it is difficult to scale up. The two-step synthesis route of ethylene oxide requires harsh high-pressure reactions and large equipment investments. The two-step hydrogenation process of acrolein involves highly toxic and explosive raw materials, making storage and transportation difficult, and resulting in high production costs. Each of the existing processes has its shortcomings. The production of 1,3-propanediol using the catalytic hydrogenolysis of surplus glycerol offers both environmental and economic advantages. The research focus for this route is the development of highly active and selective catalysts. Researchers have conducted extensive studies on Pt-W systems supported on different supports, finding that Pt-W-Zr catalysts have good activity and selectivity for 1,3-propanediol. However, these catalysts still suffer from low conversion rates and low selectivity.

[0004] Supercritical fluids exhibit rapid diffusion, strong dissolving power, and excellent wettability, making them widely used in extraction and separation, biomedicine, and materials preparation. However, no technology currently exists to utilize supercritical fluid technology in the preparation of Pt-W-Zr catalysts to address their low conversion and selectivity issues. Summary of the Invention

[0005] Based on the technical problems existing in the background technology, this invention proposes a method and application for preparing Pt / WO3-ZrO2 catalyst based on supercritical crystallization. For the first time, supercritical fluid technology is used to prepare Pt / WO3-ZrO2 catalyst. Compared with the traditional impregnation method, the method of this invention is simple to operate, has a short reaction time, good dispersion performance of active components, and high catalytic activity. The prepared catalyst has a high glycerol conversion rate and 1,3-propanediol selectivity, delays the loss of active components, and has high reusability.

[0006] This invention proposes a method for preparing Pt / WO3-ZrO2 catalyst based on supercritical crystallization, comprising: adding a WO3-ZrO2 composite solid acid to a platinum source solution and mixing it; placing the resulting mixture in a supercritical reactor; introducing carbon dioxide gas to carry out a supercritical crystallization reaction; naturally cooling to room temperature; drying; and calcining to obtain the Pt / WO3-ZrO2 catalyst.

[0007] Preferably, the WO3-ZrO2 composite solid acid is obtained by dissolving tungsten source and zirconium source in water, stirring and mixing, pre-drying, and pre-calcining.

[0008] Preferably, the tungsten source is at least one of ammonium metatungstate or sodium tungstate; the zirconium source is at least one of zirconium chloride, zirconium oxychloride, or zirconium oxynitrate. Preferably, the W / Zr molar ratio in the tungsten source and zirconium source is 0.1-0.5.

[0009] Preferably, the stirring and mixing time is 2-10 hours; the pre-drying temperature is 70-140°C and the time is 8-24 hours; the pre-calcination temperature is 450-700°C and the time is 2-8 hours.

[0010] Preferably, the platinum source is at least one of platinum nitrate or chloroplatinic acid.

[0011] Preferably, the supercritical crystallization reaction temperature is 30-120℃, the pressure is 6-12MPa, and the time is 8-16h.

[0012] Preferably, the drying temperature is 80-140℃ and the time is 8-24h; the calcination temperature is 250-450℃ and the time is 2-8h, which is carried out under a reducing atmosphere.

[0013] Preferably, the Pt loading in the Pt / WO3-ZrO2 catalyst is 0.2-3.0 wt%.

[0014] The present invention also proposes a Pt / WO3-ZrO2 catalyst prepared by the above method.

[0015] This invention also proposes an application of the above-mentioned Pt / WO3-ZrO2 catalyst in the hydrogenolysis of glycerol to 1,3-propanediol.

[0016] Compared with the prior art, the present invention has the following beneficial effects: Compared to traditional impregnation processes, the preparation of Pt / WO3-ZrO2 catalysts based on supercritical fluid technology offers significant advantages: Leveraging the excellent diffusion, dissolution, and wetting properties of supercritical fluids, the active component Pt can be uniformly distributed on the WO3-ZrO2 support, effectively enhancing the metal-support interaction. This preparation process is simple, has a short reaction cycle, and is easy to recover the catalyst. The catalyst exhibits high dispersibility, high catalytic activity, low active component loss rate, and good cycle stability. When used in the glycerol hydrogenolysis to 1,3-propanediol system, it significantly improves glycerol conversion and 1,3-propanediol selectivity, while mitigating the active component loss problem and enhancing catalyst reusability. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0018] This invention provides a catalyst for the hydrogenolysis of glycerol to 1,3-propanediol and its preparation method, comprising the following steps: Step (1): The zirconium source and tungsten source are mixed and dissolved in water, stirred, dried and calcined to obtain a composite solid acid of WO3-ZrO2; The zirconium source is any one of zirconium chloride, zirconium oxychloride, or zirconium oxynitrate; the tungsten source is any one of ammonium metatungstate or sodium tungstate; the W / Zr molar ratio is 0.1-0.5.

[0019] In a preferred embodiment of the present invention, the stirring method is to stir at room temperature for 2-10 hours. If the stirring time is too short, the raw materials will not dissolve and mix evenly, the W / Zr ratio will be unbalanced in some areas, the WO3 will be poorly dispersed after calcination, and the acidity and reaction activity of the catalyst will be reduced.

[0020] In a preferred embodiment of the present invention, the drying method is to dry at 70-140°C for 8-24 hours; if the temperature is too low or the time is too short, residual solution will remain in the catalyst, which will affect the actual quality and catalytic performance of the catalyst.

[0021] In a preferred embodiment of the present invention, the calcination conditions are maintained at 450-700℃ for 2-8 hours; if the temperature is too low, the precursor will not decompose completely and the acidity will be weak; if the temperature is too high, the grains will sinter, ZrO2 will undergo phase transformation, and WO3 will agglomerate and become deactivated.

[0022] Step (2): Add the WO3-ZrO2 composite solid acid to the platinum source solution to obtain a reaction mixture, place it in a supercritical crystallization reactor, introduce carbon dioxide gas, raise the temperature to carry out the crystallization reaction, cool to room temperature after completion, and finally dry and calcine to obtain the Pt / WO3-ZrO2 catalyst.

[0023] In a preferred embodiment of the present invention, the platinum solution is either platinum nitrate or chloroplatinic acid; the platinum loading in the Pt / WO3-ZrO2 catalyst is 0.2-3.0 wt%; too low a Pt loading results in insufficient active sites; too high a Pt loading leads to agglomeration and sintering, and a decrease in metal utilization.

[0024] In a preferred embodiment of the present invention, the supercritical conditions are a temperature of 30-120°C and a pressure of 6-12 MPa, and the crystallization reaction conditions are a reaction at 30-120°C for 8-16 hours.

[0025] In a preferred embodiment of the present invention, the drying method is to dry at 80-140°C for 8-24 hours; if the temperature is low and the time is short, the solvent and salt will not be completely removed, and the calcination will easily cause bubbling and clumping, uneven Pt dispersion, and easy collapse of the pores.

[0026] In a preferred embodiment of the present invention, the calcination method is to maintain the temperature at 250-450℃ for 2-8 hours; if the temperature is too low, the precursor decomposes incompletely and the Pt dispersion is poor; if the temperature is too high, the Pt particles sinter and grow, the number of metal active sites decreases, and the catalytic performance declines.

[0027] This invention proposes an application of the above-mentioned Pt / WO3-ZrO2 catalyst in the hydrogenolysis of glycerol to produce 1,3-propanediol.

[0028] A method for selective hydrogenolysis of glycerol to produce 1,3-propanediol using glycerol aqueous solution as raw material and Pt / WO3-ZrO2 as catalyst, wherein the catalytic reaction is carried out under certain reaction temperature and hydrogen pressure conditions.

[0029] The technical solution of the present invention will be described in detail below through specific embodiments. However, it should be clearly stated that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present invention.

[0030] Example 1 A method for preparing Pt / WO3-ZrO2 catalyst based on supercritical crystallization, comprising: 53.71 g of zirconium oxychloride and 5.46 g of ammonium metatungstate were mixed and dissolved in deionized water, stirred at room temperature for 5 h, dried at 100 °C for 12 h, and calcined at 600 °C in air for 6 h to obtain a WO3-ZrO2 composite solid acid. 10.7 g of the WO3-ZrO2 composite solid acid and 0.46 g of chloroplatinic acid were added to 10 mL of deionized water to obtain a reaction mixture, which was placed in a supercritical reactor. The temperature inside the reactor was raised to 60 °C, carbon dioxide gas was introduced, and the pressure inside the reactor reached 9 MPa. A supercritical crystallization reaction was carried out for 8 h. After the reaction was completed, the mixture was cooled to room temperature, dried at 100 °C for 12 h, and then calcined at 350 °C in hydrogen atmosphere for 3 h to obtain the Pt / WO3-ZrO2 catalyst.

[0031] Example 2 A method for preparing Pt / WO3-ZrO2 catalyst based on supercritical crystallization, comprising: 40.50 g of zirconium oxychloride and 5.39 g of ammonium metatungstate were mixed and dissolved in deionized water, stirred at room temperature for 6 h, dried at 110 °C for 12 h, and calcined at 650 °C in air for 6 h to obtain a WO3-ZrO2 composite solid acid. 8.52 g of the WO3-ZrO2 composite solid acid and 0.36 g of chloroplatinic acid were added to 8 mL of deionized water to obtain a reaction mixture, which was placed in a supercritical reactor. The temperature inside the reactor was raised to 65 °C, carbon dioxide gas was introduced, and the pressure inside the reactor reached 10 MPa. A supercritical crystallization reaction was carried out for 10 h. After the reaction, the mixture was cooled to room temperature, dried at 120 °C for 16 h, and then calcined at 350 °C in hydrogen atmosphere for 4 h to obtain the Pt / WO3-ZrO2 catalyst.

[0032] Example 3 A method for preparing Pt / WO3-ZrO2 catalyst based on supercritical crystallization, comprising: 32.46 g of zirconium oxychloride and 4.32 g of ammonium metatungstate were mixed and dissolved in deionized water, stirred at room temperature for 8 h, dried at 120 °C for 16 h, and calcined at 700 °C in air for 5 h to obtain a WO3-ZrO2 composite solid acid. 9.23 g of the WO3-ZrO2 composite solid acid and 0.39 g of chloroplatinic acid were added to 8 mL of deionized water to obtain a reaction mixture, which was placed in a supercritical reactor. The temperature inside the reactor was raised to 70 °C, carbon dioxide gas was introduced, and the pressure inside the reactor reached 11 MPa. A supercritical crystallization reaction was carried out for 8 h. After the reaction was completed, the mixture was cooled to room temperature, dried at 120 °C for 12 h, and then calcined at 300 °C in hydrogen atmosphere for 3 h to obtain the Pt / WO3-ZrO2 catalyst.

[0033] Example 4 A method for preparing Pt / WO3-ZrO2 catalyst based on supercritical crystallization, comprising: 20.92 g of zirconium oxychloride and 4.84 g of ammonium metatungstate were mixed and dissolved in deionized water, stirred at room temperature for 8 h, dried at 120 °C for 24 h, and calcined at 700 °C in air for 6 h to obtain a WO3-ZrO2 composite solid acid. 8.56 g of the WO3-ZrO2 composite solid acid and 0.36 g of chloroplatinic acid were added to 8 mL of deionized water to obtain a reaction mixture, which was placed in a supercritical reactor. The temperature inside the reactor was raised to 75 °C, carbon dioxide gas was introduced, and the pressure inside the reactor reached 12 MPa. A supercritical crystallization reaction was carried out for 9 h. After the reaction was completed, the mixture was cooled to room temperature, dried at 120 °C for 16 h, and then calcined at 300 °C in hydrogen atmosphere for 4 h to obtain the Pt / WO3-ZrO2 catalyst.

[0034] Example 5 A method for preparing Pt / WO3-ZrO2 catalyst based on supercritical crystallization, comprising: 45.36 g of zirconium oxychloride and 4.53 g of ammonium metatungstate were mixed and dissolved in deionized water, stirred at room temperature for 6 h, dried at 120 °C for 18 h, and calcined at 650 °C in air for 5 h to obtain a WO3-ZrO2 composite solid acid. 7.47 g of the WO3-ZrO2 composite solid acid and 0.31 g of chloroplatinic acid were added to 7 mL of deionized water to obtain a reaction mixture, which was placed in a supercritical reactor. The temperature inside the reactor was raised to 65 °C, carbon dioxide gas was introduced, and the pressure inside the reactor reached 9 MPa. A supercritical crystallization reaction was carried out for 12 h. After the reaction was completed, the mixture was cooled to room temperature, dried at 100 °C for 24 h, and then calcined at 400 °C in hydrogen atmosphere for 5 h to obtain the Pt / WO3-ZrO2 catalyst.

[0035] Comparative Example 1 A method for preparing Pt / WO3-ZrO2 catalyst based on conventional impregnation method, comprising: 53.71 g of zirconium oxychloride and 5.46 g of ammonium metatungstate were mixed and dissolved in deionized water, stirred at room temperature for 5 h, dried at 100 °C for 12 h, and calcined at 600 °C in air for 6 h to obtain a WO3-ZrO2 composite solid acid. 10.7 g of the WO3-ZrO2 composite solid acid and 0.46 g of chloroplatinic acid were added to 10 mL of deionized water to obtain a reaction mixture. After stirring at room temperature for 8 h, the mixture was dried at 100 °C for 12 h and then calcined at 350 °C in hydrogen atmosphere for 3 h to obtain the Pt / WO3-ZrO2 catalyst.

[0036] Comparative Example 2 A method for preparing Pt / WO3-ZrO2 catalyst based on conventional impregnation method, comprising: 32.46 g of zirconium oxychloride and 4.32 g of ammonium metatungstate were mixed and dissolved in deionized water, stirred at room temperature for 8 h, dried at 120 °C for 16 h, and calcined at 700 °C in air for 5 h to obtain a WO3-ZrO2 composite solid acid. 9.23 g of the WO3-ZrO2 composite solid acid and 0.39 g of chloroplatinic acid were added to 8 mL of deionized water to obtain a reaction mixture, stirred at room temperature for 6 h, dried at 120 °C for 12 h, and then calcined at 300 °C in hydrogen atmosphere for 3 h to obtain the Pt / WO3-ZrO2 catalyst.

[0037] Comparative Example 3 A method for preparing Pt / WO3-ZrO2 catalyst based on conventional impregnation method, comprising: 20.92 g of zirconium oxychloride and 4.84 g of ammonium metatungstate were mixed and dissolved in deionized water, stirred at room temperature for 8 h, dried at 120 °C for 24 h, and calcined at 700 °C in air for 6 h to obtain a WO3-ZrO2 composite solid acid. 8.56 g of the WO3-ZrO2 composite solid acid and 0.36 g of chloroplatinic acid were added to 8 mL of deionized water to obtain a reaction mixture, stirred at room temperature for 6 h, dried at 120 °C for 16 h, and then calcined at 300 °C in hydrogen atmosphere for 4 h to obtain the Pt / WO3-ZrO2 catalyst.

[0038] Application examples The Pt / WO3-ZrO2 catalyst described in the examples and comparative examples was used for the hydrogenolysis of glycerol to 1,3-propanediol: 1 g of the above catalyst and 15 wt% glycerol solution were added to a 50 mL stainless steel high-temperature and high-pressure reactor and reacted at 160 °C and 6 MPa hydrogen pressure for 14 h. After the reaction, the mixture was centrifuged, and the supernatant was collected for gas chromatography analysis. The test results are shown in Table 1.

[0039] The W and Pt contents (A) of the Pt / WO3-ZrO2 catalyst before the reaction were measured using ICP. After the reaction, the W and Pt contents (B) of the Pt / WO3-ZrO2 catalyst were determined using ICP. Then, the loss rate of the active component of the catalyst was calculated using the following formula: Loss rate of active component = .

[0040] Table 1. Results of using the Pt / WO3-ZrO2 catalyst described in the examples and comparative examples to produce 1,3-propanediol.

[0041] As can be seen from Table 1 above, the Pt / WO3-ZrO2 catalysts prepared by the methods described in Examples 1-5 of this invention exhibit superior catalytic performance compared to the Pt / WO3-ZrO2 catalysts prepared by the conventional impregnation method (Comparative Examples 1-3). Specifically, in the selective hydrogenolysis of glycerol to 1,3-propanediol, the Pt / WO3-ZrO2 catalysts provided in Examples 1-5 of this invention show significantly better glycerol conversion and 1,3-propanediol selectivity than the catalysts prepared by the conventional impregnation method (Comparative Examples 1-3).

[0042] By measuring the loss rate of active components of the Pt / WO3-ZrO2 catalyst after the reaction, the inventors found that the Pt / WO3-ZrO2 catalyst provided in the examples had a low loss rate of active components, which enabled the catalyst to maintain its catalytic activity for the selective hydrogenolysis of glycerol to produce 1,3-propanediol for a long time.

[0043] In summary, the Pt / WO3-ZrO2 catalyst prepared by supercritical fluid provided by this invention exhibits excellent activity in the selective hydrogenolysis of glycerol to produce 1,3-propanediol, with low loss rate of active components and high stability. In particular, the method for preparing the catalyst under supercritical fluid conditions is simple to operate, has a short reaction time, and produces uniformly dispersed active components; this lays the foundation for the industrialization of this method.

[0044] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing Pt / WO3-ZrO2 catalyst based on supercritical crystallization, characterized in that, include: The composite solid acid of WO3-ZrO2 was added to a platinum source solution and mixed. The resulting mixture was placed in a supercritical reactor, and carbon dioxide gas was introduced to carry out a supercritical crystallization reaction. After naturally cooling to room temperature, it was dried and calcined to obtain the Pt / WO3-ZrO2 catalyst.

2. The method for preparing Pt / WO3-ZrO2 catalyst based on supercritical crystallization according to claim 1, characterized in that, The WO3-ZrO2 composite solid acid is obtained by dissolving tungsten and zirconium sources in water, stirring and mixing, pre-drying, and pre-calcining.

3. The method for preparing Pt / WO3-ZrO2 catalyst based on supercritical crystallization according to claim 2, characterized in that, The tungsten source is at least one of ammonium metatungstate or sodium tungstate; the zirconium source is at least one of zirconium chloride, zirconium oxychloride or zirconium oxynitrate. The W / Zr molar ratio in the tungsten source and zirconium source is 0.1-0.

5.

4. The method for preparing Pt / WO3-ZrO2 catalyst based on supercritical crystallization according to claim 2, characterized in that, The mixing time is 2-10 hours; the pre-drying temperature is 70-140℃ and the time is 8-24 hours; the pre-calcination temperature is 450-700℃ and the time is 2-8 hours.

5. The method for preparing Pt / WO3-ZrO2 catalyst based on supercritical crystallization according to any one of claims 1-4, characterized in that, The platinum source is at least one of platinum nitrate or chloroplatinic acid.

6. The method for preparing Pt / WO3-ZrO2 catalyst based on supercritical crystallization according to any one of claims 1-4, characterized in that, The supercritical crystallization reaction temperature is 30-120℃, the pressure is 6-12MPa, and the time is 8-16h.

7. The method for preparing Pt / WO3-ZrO2 catalyst based on supercritical crystallization according to any one of claims 1-4, characterized in that, The drying temperature is 80-140℃ and the time is 8-24h; the calcination temperature is 250-450℃ and the time is 2-8h, which is carried out under a reducing atmosphere.

8. The method for preparing Pt / WO3-ZrO2 catalyst based on supercritical crystallization according to any one of claims 1-4, characterized in that, In the Pt / WO3-ZrO2 catalyst, the Pt loading is 0.2-3.0 wt%.

9. A Pt / WO3-ZrO2 catalyst prepared by the method according to any one of claims 1-8.

10. The use of the Pt / WO3-ZrO2 catalyst of claim 9 in the hydrogenolysis of glycerol to 1,3-propanediol.

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