A dual-metal catalyst for efficiently photocatalytic-thermal catalytic hydrogenolysis of benzene-based plastics and its preparation method

Abstract

A bimetallic catalyst for efficiently photocatalytic-thermal catalytic hydrogenolysis of benzene-based plastics and its preparation method belong to the fields of catalytic chemistry and environmental chemistry. The preparation method is an in-situ high-temperature pyrolysis method under a nitrogen atmosphere. Ruthenium acetylacetonate, lanthanum nitrate hexahydrate, and 1,10-phenanthroline are dissolved in ethanol for treatment, and then they are loaded onto anatase TiO2 support by an impregnation method. The supported catalyst is pyrolyzed by calcination at 800 °C under a nitrogen atmosphere to form a RuLa@NC / TiO2 bimetallic nanocatalyst. The prepared RuLa@NC / TiO2 bimetallic nanocatalyst has a simple preparation process, and Ru and La elements are highly dispersed on the titanium dioxide support, showing good application prospects in the field of recycling treatment of waste plastic polymers.

Description

Technical Field

[0001] The present invention relates to a bimetallic catalyst for efficient selective photo-thermal catalytic hydrogenolysis of polyethylene terephthalate and a preparation method thereof. Specifically, Ru, La precursors and 1,10-phenanthroline are loaded onto TiO2 by an impregnation method, and then the RuLa@NC / TiO2 catalyst is obtained through calcination treatment. This catalyst exhibits good photo-thermal synergistic catalytic activity for the hydrogenolysis of polyethylene terephthalate. It belongs to the fields of catalytic chemistry and environmental chemistry. Background Art

[0002] Polyethylene terephthalate (PET) is a kind of plastic and also the most important one among thermoplastic polyesters. It is prepared by a polycondensation reaction of terephthalic acid and ethylene glycol. At present, PET has become one of the most widely used commodity plastics in the world, with an annual production scale of about 50 million tons. Due to its thermal stability, chemical resistance, transparency, light weight, as well as good tensile and impact strengths, PET is widely used in the manufacture of beverage bottles, fibers and filaments. The hazards of plastic waste are complex and diverse, especially having a serious impact on the environment and human health. In recent years, with the development of the world's scientific and technological level, 380 million tons of plastics are produced annually around the world for people's production and life. However, due to its complex regeneration and recycling, about 78% of the waste plastics are eventually discarded in landfill sites and the natural environment. Like most other types of plastics, PET also has high resistance to biodegradation in nature. Therefore, the degradation and recycling of waste plastics are the key to solving the problem.

[0003] Compared with the common pyrolysis method, catalytic hydrogenolysis can be carried out at a lower temperature and achieve a more selective decomposition of polymers. At the same time, the hydrogenation conversion of waste plastics into various hydrocarbons is also a strategy to reduce the use of petroleum resources for some commodity chemicals. It is known that the effective catalyst required to break the σ bond, appropriate reaction conditions and reaction selectivity are the key to catalytic hydrogenolysis. Generally speaking, the catalyst for catalytic hydrogenolysis needs to have the dual functions of catalytic dehydrogenation and catalytic hydrogenation. Group VIII metal elements, such as Ni, Co, Pd, Pt, Ru, Rh, etc. and the subgroup metal element Cu have been proven to have good catalytic hydrogenolysis activity, including homogeneous catalysts composed of complexes synthesized based on them and heterogeneous catalysts in various forms of metals. In current methods, there are often harsh decomposition conditions, such as a higher decomposition temperature (≥300 °C) and a higher decomposition pressure (≥1 MPa), etc.; at the same time, toluene and p-xylene, as very important industrial raw materials, have very high industrial value, and the catalyst mentioned in this invention has very high toluene and p-xylene selectivity, which helps to convert waste plastics into high-value industrial raw materials. As far as we know, there is no literature and patent reporting the preparation of simultaneously loading the precursors of metal Ru and La onto the anatase TiO2 support by the in-situ pyrolysis method and its research on the selective photo-thermal synergistic catalytic hydrogenolysis of PET into toluene and p-xylene. This invention discloses a controllable preparation method of the RuLa@NC / TiO2 catalyst, and it is found that the RuLa@NC / TiO2 catalyst has excellent catalytic activity and high selectivity for the selective photo-thermal synergistic catalytic hydrogenolysis of PET. Summary of the Invention

[0004] The purpose of this invention is to use the impregnation method to load the precursors of metal Ru and La and 1,10-phenanthroline onto the surface of TiO2, and then form a supported RuLa@NC / TiO2 catalyst with a nitrogen-doped carbon structure through high-temperature roasting pyrolysis, which is used for the selective photo-thermal synergistic catalytic hydrogenolysis of PET into toluene and p-xylene.

[0005] A catalyst for the selective catalytic hydrogenolysis of PET and its preparation method. This invention specifically includes the following steps:

[0006] (1) Dissolve the lanthanum precursor in deionized water, add ruthenium acetylacetonate and 1,10-phenanthroline to anhydrous ethanol for dissolution, and stir the obtained aqueous solution of the lanthanum precursor, the ethanol solution of ruthenium acetylacetonate and 1,10-phenanthroline at room temperature until completely mixed and dissolved;

[0007] (2) Isolate the solution in step (1) from air, stir it at 60 °C for 1 h, add anatase TiO2 to the above solution, and stir and impregnate it for 8 - 10 h while isolating air.

[0008] (3) The impregnated liquid was subjected to rotary evaporation, and the obtained solid was placed in a porcelain boat. In a tube furnace, the temperature was raised to 300°C at 5°C / min under a nitrogen atmosphere, and then raised to 800°C at 2°C / min, maintained for 10-12 hours, and then cooled to obtain the RuLa@NC / TiO2 catalyst.

[0009] In step (1), the lanthanum precursor is selected from one or more of lanthanum nitrate hexahydrate and lanthanum chloride heptahydrate. The materials are added according to the molar ratio of metal ruthenium: lanthanum of 1:1.5 and the molar ratio of metal: 1,10-phenanthroline of 1:10-20.

[0010] Every 30 mg of lanthanum precursor corresponds to 3-10 mL of deionized water to prepare a solution, and every 20 mg of ruthenium acetylacetonate corresponds to 15 mL-30 mL of anhydrous ethanol.

[0011] In step (3), the precursors of metal Ru and La are loaded on an anatase TiO2 carrier, wherein the loading amount of Ru on the anatase TiO2 carrier is 0.8 wt%-1.5 wt%.

[0012] The catalyst obtained by the invention is used for the selective catalytic hydrogenolysis of PET, and the catalytic products are toluene and p-xylene.

[0013] Catalyst performance evaluation:

[0014] The catalyst performance was evaluated using the yields of toluene and p-xylene as activity evaluation criteria. A 0.1g PET sample, 0.1g catalyst, and 10mL water reaction were performed at 180°C, 0.4MPa hydrogen pressure, and xenon lamp illumination for 8 hours. The product composition was determined by gas chromatography-mass spectrometry. The RuLa@NC / TiO2 catalyst achieved a toluene yield of 19.61% and a p-xylene yield of 71.25%. The RuLa@NC / TiO2 catalyst exhibited not only excellent catalytic activity but also high selectivity for toluene and p-xylene.

[0015] The catalyst preparation process of the present invention is simple, exhibits good catalytic activity and high selectivity to PET, and has good application prospects in the degradation and recycling of waste plastics. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 are the XRD spectra of the prepared catalyst samples, where curves (a) and (b) are the XRD spectra of the comparative samples Ru / TiO2 and RuLa@NC / TiO2 prepared by the impregnation method, respectively.

[0017] Figure 2 (a)-(b) are HAADF-STEM images of RuLa@NC / TiO2 and EDS element scanning images of Ru, La, N, and Ti.

[0018] Figure 3 This is the GC-MS spectrum of the product after the reaction of the prepared catalyst sample. Among them, curves (a) and (b) are the GC-MS spectra of the comparative samples Ru / TiO2 and RuLa@NC / TiO2, respectively. 1 corresponds to the peak of toluene, and 2 corresponds to the peak of p-xylene.

[0019] Table 1 shows the toluene and p-xylene yields corresponding to the prepared catalyst samples. Detailed implementation manners

[0020] To further illustrate the present invention, the following will be described in detail with examples, but the present invention is not limited to the following examples.

[0021] Example 1

[0022] (1) According to the molar ratio of ruthenium metal to lanthanum metal being 1:1.5, and the molar ratio of all metals to 1,10-phenanthroline being 1:20 for feeding materials, weigh 19.7 mg of ruthenium acetylacetonate and 445 mg of 1,10-phenanthroline and add them to 20 mL of absolute ethanol. Dissolve 25 mg of lanthanum nitrate hexahydrate in 5 mL of water, and after mixing the two, stir at room temperature for 20 min until completely dissolved.

[0023] (2) Isolate the solution in (1) from air, stir at 60 °C for 1 h, add 0.5 g of anatase TiO2 to the above solution, and isolate air and stir for impregnation for 12 h.

[0024] (3) Perform rotary evaporation on the impregnated liquid, place the remaining solid in a porcelain boat, in a tubular furnace, heat it to 300 °C at a rate of 5 °C / min under a nitrogen atmosphere, then heat it to 800 °C at a rate of 2 °C / min, hold for 10 h, and cool down to obtain the RuLa@NC / TiO2-1 catalyst. The loading amount of ruthenium metal after loading is 1%.

[0025] Weigh 0.1 g of PET sample, 0.1 g of catalyst, and 10 mL of water, react at 180 °C, hydrogen pressure of 0.4 MPa, and xenon lamp irradiation conditions for 8 h, and use a gas chromatography-mass spectrometry instrument to determine the product composition. Finally, a toluene yield of 19.61% and a p-xylene yield of 71.25% are obtained.

[0026] Example 2

[0027] (1) According to the molar ratio of ruthenium metal to lanthanum metal being 1:1.5, and the molar ratio of all metals to 1,10-phenanthroline being 1:20 for feeding materials, weigh 19.7 mg of ruthenium acetylacetonate and 445 mg of 1,10-phenanthroline and add them to 20 mL of absolute ethanol. Dissolve 28 mg of lanthanum chloride heptahydrate in 5 mL of water, and after mixing the two, stir at room temperature for 20 min until completely dissolved.

[0028] (2) Isolate the solution in (1) from air, stir it at 60 °C for 1 h, add 0.5 g of anatase TiO₂ to the above solution, and stir and impregnate it for 12 h while isolating air.

[0029] (3) Rotate and evaporate the impregnated liquid, place the remaining solid in a porcelain boat, in a tube furnace, heat it to 300 °C at a rate of 5 °C / min under a nitrogen atmosphere, then heat it to 800 °C at a rate of 2 °C / min, hold for 10 h, and cool down to obtain the RuLa@NC / TiO₂-2 catalyst. The loading amount of ruthenium after loading is 1%.

[0030] Weigh 0.1 g of the PET sample, 0.1 g of the catalyst, and 10 mL of water, react at 180 °C, a hydrogen pressure of 0.4 MPa, and under xenon lamp irradiation for 8 h, and use a gas chromatography-mass spectrometry instrument to determine the product composition. Finally, a toluene yield of 19.61% and a p-xylene yield of 71.25% are obtained.

[0031] Table 1

[0032]

Claims

1. A method for preparing a bimetallic catalyst for efficient photo-thermal synergistic catalytic hydrogenolysis of benzene-based plastics, characterized in that: The following steps are involved: (1) dissolving a lanthanum precursor in deionized water, adding ruthenium acetylacetonate and 1,10-phenanthroline into anhydrous ethanol and dissolving them, and stirring the obtained lanthanum precursor aqueous solution, ruthenium acetylacetonate and 1,10-phenanthroline ethanol solution at room temperature until they are completely mixed and dissolved; (2) isolating the solution in step (1) from air, stirring at 60°C for 1 hour, adding anatase TiO2 to the above solution, isolating from air, stirring and impregnating for 8-10 hours; (3) The impregnated turbid liquid was separated on a rotary evaporator, and the obtained solid was placed in a porcelain boat. In a tube furnace, the temperature was raised to 300°C at 5°C / min under a nitrogen atmosphere, and then raised to 800°C at 2°C / min, maintained for 10-12 hours, and then cooled to obtain the RuLa@NC / TiO2 catalyst; Step (1) adding materials according to the molar ratio of metal ruthenium: lanthanum of 1:1.5 and the molar ratio of metal: 1,10-phenanthroline of 1:10-20; The loading amount of Ru on the anatase TiO2 carrier in step (3) is 0.8 wt%-1.5 wt%.

2. The preparation method according to claim 1, characterized in that: In step (1), the lanthanum precursor is selected from one or more of lanthanum nitrate hexahydrate and lanthanum chloride heptahydrate.

3. The preparation method according to claim 1, characterized in that Every 30 mg of lanthanum precursor corresponds to 3-10 mL of deionized water to prepare a solution, and every 20 mg of ruthenium acetylacetonate corresponds to 15 mL-30 mL of anhydrous ethanol.

4. A catalyst prepared according to the method according to any one of claims 1 to 3.

5. Use of the catalyst prepared by the method according to any one of claims 1 to 3, characterized in that: Used for selective catalytic hydrogenation of polyethylene terephthalate (PET) to toluene and p-xylene.

6. Use according to claim 5, characterized in that Weigh 0.1 g of PET sample, 0.1 g of catalyst and 10 mL of water, and react at 180°C, a hydrogen pressure of 0.4 MPa and xenon lamp irradiation for 8 h.

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