WO2022252244A1 - 一种低温降解聚烯烃废塑料制备富氢合成气的方法 - Google Patents

一种低温降解聚烯烃废塑料制备富氢合成气的方法 Download PDF

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WO2022252244A1
WO2022252244A1 PCT/CN2021/098607 CN2021098607W WO2022252244A1 WO 2022252244 A1 WO2022252244 A1 WO 2022252244A1 CN 2021098607 W CN2021098607 W CN 2021098607W WO 2022252244 A1 WO2022252244 A1 WO 2022252244A1
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reaction
hydrogen
hydrogen peroxide
mesoporous carbon
polyolefin
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王树荣
苏红才
李天�
朱玲君
李允超
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Zhejiang University
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Definitions

  • the invention relates to the technical field of plastic degradation, in particular to the technical field of low-temperature degradation of polyolefin waste plastics to prepare hydrogen-rich synthesis gas.
  • plastic occupies an important position in the field of materials. my country is the world's largest producer of plastics. It produces a huge amount of plastic waste every year. Some plastics that are difficult to decompose enter the natural environment on land and the ocean, causing a huge impact on the ecological environment.
  • waste plastics include polyethylene, polypropylene, polyethylene terephthalate, polyvinyl chloride, polycarbonate, polystyrene, and acrylonitrile-butadiene-styrene plastics.
  • polyolefin plastics such as polyethylene and polypropylene are the most widely used, and account for the largest proportion of the total waste plastics.
  • Liquid-phase reforming is a low-temperature and low-pressure hydrogen technology, which can convert liquid oxygen-containing organic matter into hydrogen by using the catalytic action of a catalyst under the hydrothermal conditions of 200-260°C and 1.5-4MPa, and waste polyolefin plastics as a This kind of solid waste does not contain oxygen atoms, so it cannot be directly subjected to liquid phase reforming to produce hydrogen.
  • the method of producing hydrogen from waste plastics is mainly based on high-temperature pyrolysis and gasification (500-800 ° C), which is also accompanied by the production of by-products such as coke and tar.
  • the higher reaction temperature also results in higher cost input.
  • existing studies (Waste management 2020, 102, 520-7, Energy 2020, 191, 116527) have proposed the use of supercritical water gasification (T>374°C, P>22.1MPa) to convert plastics into hydrogen, due to supercritical water gasification
  • the operation has higher requirements on the equipment, so there are certain limitations in industrial application.
  • the hydrogen yield in the synthesis gas obtained by converting polyethylene and polypropylene to hydrogen by supercritical water gasification is currently (2- 5mol/kg plastic) and hydrogen concentration is not high (10-40%).
  • the purpose of the present invention is to solve the problems in the prior art, and propose a method for preparing hydrogen-rich synthesis gas by degrading polyolefin waste plastics at low temperature, using a two-step method combining oxidation pretreatment and reforming reaction.
  • a method for preparing hydrogen-rich synthesis gas by degrading polyolefin waste plastics at low temperature using a two-step method combining oxidation pretreatment and reforming reaction.
  • In the first stage Using dilute H 2 O 2 solution at a reaction temperature lower than 250°C to carry out oxidative pretreatment of polyolefin waste plastics such as polyethylene and polypropylene, in the second stage, for the liquid phase obtained from the pretreatment, in the high-efficiency carbon-based catalyst Hydrogen production by low-temperature reforming under catalysis, and then high-efficiency hydrogen production of polyolefin plastics under mild conditions.
  • the present invention proposes a method for preparing hydrogen-rich synthesis gas by degrading polyolefin waste plastics at low temperature, using a two-step method combining oxidation pretreatment and reforming reaction, including the following steps:
  • the H 2 O 2 in the reaction solution is completely decomposed. After testing, the product does not contain H 2 O 2 , so there will be no residual H 2 O 2 that will have a negative effect on the catalyst of the reforming reaction in the second stage;
  • Step (3) Fill another hydrothermal reactor with a metal-based catalyst supported by mesoporous carbon, and then pass the liquid phase product obtained in step (2) into the hydrothermal reactor for reforming reaction to obtain hydrogen-rich synthesis gas product.
  • Step (1) and step (2) are oxidation pretreatment stages, and step (3) is a reforming reaction stage.
  • the content of H 2 O 2 in the hydrogen peroxide in the step (1) is 0.5-2%;
  • H 2 O 2 As a strong oxidant, high concentration of H 2 O 2 can easily lead to harsh conditions for oxidative cracking of CC bonds, and too low a concentration of H 2 O 2 will lead to insufficient oxidation, so 0.25%-6% H 2 O 2 hydrogen peroxide can be effective
  • the pre-oxidation of polyolefin plastics is realized under low temperature conditions, and the content of H 2 O 2 is 0.5-2%, the yield and concentration of hydrogen obtained by the second stage reforming reaction are optimal.
  • the weight part of the hydrogen peroxide in the described step (1) is 3-80 weight part
  • the weight portion of hydrogen peroxide in the step (1) is 5-10 parts;
  • the residual hydrogen peroxide in the oxidation pretreatment has negative effects such as oxidation on the metal catalyst in the second stage reforming reaction.
  • the reforming reaction process will produce more CO 2 causes the mole fraction of H 2 in the gas product to decrease, and it is optimal when the weight part of hydrogen peroxide is 5-10 parts.
  • the reaction pressure in the step (2) is 0.5-2 MPa, and the reaction time is 30-90 min.
  • the reaction temperature in the step (2) is 190-200° C.
  • the reaction pressure is 1 MPa
  • the reaction time is 30-60 min.
  • the reaction temperature is 200° C., and the reaction time is 60 minutes;
  • the main component of the liquid phase product obtained in the step (2) is acetic acid, and the gas phase product is oxygen and carbon dioxide;
  • the liquid phase product is mainly acetic acid, and the content of other short-chain small molecular acids such as formic acid and propionic acid is very low, which will not adversely affect the activity of the catalyst for the reforming reaction.
  • the reaction temperature of the reforming reaction in the step (3) is 200-240° C.
  • the reaction pressure is 2-4 MPa
  • the reaction time is 120-180 min.
  • the metal-based catalyst supported by mesoporous carbon in the step (3) is Ru single metal supported by mesoporous carbon, Ni single metal supported by mesoporous carbon, Pt single metal supported by mesoporous carbon and single metal supported by mesoporous carbon.
  • Ru-Ni bimetals One or more of Ru-Ni bimetals;
  • the selected mesoporous carbon has a specific surface area of 1400-1500m 2 /g, which can provide more active sites.
  • the metal-based catalyst supported by mesoporous carbon in the step (3) is a Ru-Ni bimetallic catalyst supported by mesoporous carbon, and the mass ratio of Ru and Ni is 4:1, 1:1 or 1:1: 4;
  • Mesoporous carbon-supported Ru monometallic catalysts exhibited the highest H2 selectivity for polyolefin oxidation pretreatment, as well as the highest hydrogen yield and hydrogen concentration under the catalysis of mesoporous carbon-supported Ru monometallic catalysts, but considering Given that Ru metal is expensive, and monometallic catalysts are not stable in hydrothermal environments and are easily deactivated, adding non-noble metals to replace part of the active metal Ru can effectively reduce the cost.
  • the mesoporous carbon-supported Ru-Ni bimetallic catalyst provided by the present invention realizes a multiplied increase in the hydrogen production rate, and the formation of a RuNi alloy during the preparation process greatly improves the stability of the catalyst.
  • the polyolefin plastic is selected from one or more of polypropylene, low-density polyethylene and high-density polyethylene.
  • the preparation steps of the metal-based catalyst supported by mesoporous carbon are as follows: first sieve the mesoporous carbon to 120-150 mesh; The precursor was added to deionized water, stirred uniformly at room temperature and impregnated for 12 hours, then continued to stir at 80°C until the water evaporated to dryness, and dried the obtained sample in an oven at 105°C for 12 hours; finally at 550°C, 10% Reduction in H 2 -90% Ar for 4 hours.
  • the present invention adopts a two-step method combining oxidation pretreatment and reforming reaction to realize the degradation of polyolefin under low temperature conditions and high-efficiency hydrogen production.
  • the synergistic effect of the two stages produces the following beneficial effects:
  • the present invention adopts a two-step hydrogen production method. On the one hand, it realizes efficient hydrogen production by using polyolefin waste plastics at a temperature lower than 250 ° C. The hydrogen production rate is close to 11mol/kg of plastics, which reduces energy consumption and operating costs. On the one hand, the efficient degradation of polyolefin waste plastics has been realized, and it has high utilization value in the treatment of polyolefin plastic waste;
  • H 2 O 2 is a strong oxidizing agent.
  • the raw material will be over-oxidized, and the CC bond will be oxidatively cracked, resulting in the production of by-product carbon dioxide.
  • the low-concentration hydrogen peroxide in the reaction solution can selectively oxidize and break the carbon-carbon bonds in polyolefin plastics in a low-temperature hydrothermal environment, and form small molecular intermediates such as aldehydes, which are quickly oxidized into organic acids such as acetic acid So as to achieve the degradation of polyolefin plastics under low temperature conditions;
  • the Ru-Ni bimetallic catalyst supported by mesoporous carbon selected by the present invention has realized the multiplied increase of the hydrogen production rate, and forms a RuNi alloy in the preparation process, which greatly improves the stability of the catalyst;
  • the present invention Compared with hydrogen production by supercritical water gasification of polyolefin plastics, the present invention not only greatly reduces the reaction temperature and pressure, realizes hydrogen production under mild hydrothermal conditions of polyolefins, but also obtains hydrogen production rate and hydrogen concentration. higher;
  • the mesoporous carbon-supported Ru monometallic catalyst exhibited the highest H2 selectivity for polyolefin oxidation pretreatment, as well as the highest hydrogen yield and hydrogen concentration under the catalysis of the mesoporous carbon-supported Ru monometallic catalyst , but considering that Ru metal is expensive, and single-metal catalysts are not stable in hydrothermal environment and are easy to deactivate, adding non-noble metals to replace part of the active metal Ru can effectively Reduce catalyst costs.
  • the mesoporous carbon-supported Ru-Ni bimetallic catalyst provided by the present invention realizes a multiplied increase in the hydrogen production rate, and the formation of a RuNi alloy during the preparation process greatly improves the stability of the catalyst.
  • Fig . 1 is H of the present invention O Concentration and each product yield change figure;
  • Fig. 2 is the gas composition figure in the concentration of the present invention H 2 O 2 and syngas product
  • Fig. 3 is the present invention H 2 O 2 Concentration and the relation figure of hydrogen selectivity
  • Fig. 4 is the relationship diagram of hydrogen peroxide-polyolefin mass ratio and synthesis gas production rate of the present invention
  • Fig . 5 is H2O2concentration of the present invention and the carbon dioxide relation figure that preoxidation treatment produces;
  • Fig. 6 is the nitrogen adsorption-desorption isotherm of the synthetic fresh catalyst of the present invention.
  • Fig. 7 is the pore size distribution schematic diagram of the synthetic fresh catalyst of the present invention.
  • Fig. 8 is the XRD schematic diagram of the fresh catalyst synthesized by the present invention.
  • Fig. 9 is a TEM image and a particle size distribution diagram of the mesoporous carbon-supported catalyst of the present invention.
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 6% H2O2 hydrogen peroxide, load 0.16g of low- density polyethylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O
  • the O 2 -plastic ratio is 10:1; the reaction conditions are: reaction temperature 200°C, reaction time 60min, reaction pressure 0.5MPa; the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase product is carbon dioxide and oxygen;
  • Step 2 Pass the liquid-phase product of the first-stage oxidation pretreatment into a reactor filled with a mesoporous carbon-supported Ru monometallic catalyst.
  • the reaction conditions are: reaction temperature 240°C, reaction time 120min, reaction pressure 4MPa.
  • the preparation method of the Ru monometallic catalyst supported by mesoporous carbon is as follows: sieve the mesoporous carbon to 120-150 mesh; according to the total metal loading of 5wt%, a certain amount of mesoporous carbon and ruthenium chloride are added to deionized water , uniformly stirred and impregnated at room temperature for 12 hours, continued to stir at 80°C until the water evaporated to dryness, and dried the obtained sample in an oven at 105 °C for 12 hours; 4 hours.
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 4% H2O2 hydrogen peroxide, load 0.16g of low- density polyethylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O
  • the O 2 -plastic ratio is 10:1; the reaction conditions are: reaction temperature 200°C, reaction time 60min, reaction pressure 0.5MPa; the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase product is carbon dioxide and oxygen;
  • Step 2 is the same as Example 1 Step 2; the catalyst preparation method is the same as Example 1.
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 2% H2O2 hydrogen peroxide, load 0.16g of low - density polyethylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O
  • the O 2 -plastic ratio is 10:1; the reaction conditions are: reaction temperature 200°C, reaction time 60min, reaction pressure 0.5MPa; the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase product is carbon dioxide and oxygen;
  • Step 2 is the same as Example 1 Step 2; the catalyst preparation method is the same as Example 1.
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 1% H2O2 hydrogen peroxide, load 0.16g of low - density polyethylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O
  • the O 2 -plastic ratio is 10:1; the reaction conditions are: reaction temperature 200°C, reaction time 60min, reaction pressure 0.5MPa; the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase product is carbon dioxide and oxygen;
  • Step 2 is the same as Example 1 Step 2; the catalyst preparation method is the same as Example 1.
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 0.5% H2O2 hydrogen peroxide, load 0.16g of low - density polyethylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O
  • the O 2 -plastic ratio is 10:1; the reaction conditions are: reaction temperature 200°C, reaction time 60min, reaction pressure 0.5MPa; the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase product is carbon dioxide and oxygen;
  • Step 2 is the same as Example 1 Step 2; the catalyst preparation method is the same as Example 1.
  • Embodiment 6 is a diagrammatic representation of Embodiment 6
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 0.25% H2O2 hydrogen peroxide, load 0.16g of low-density polyethylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O
  • the O 2 -plastic ratio is 10:1; the reaction conditions are: reaction temperature 200°C, reaction time 60min, reaction pressure 0.5MPa; the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase product is carbon dioxide and oxygen;
  • Step 2 is the same as Example 1 Step 2; the catalyst preparation method is the same as Example 1.
  • Embodiment 7 is a diagrammatic representation of Embodiment 7:
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 0.5% H2O2 hydrogen peroxide, load 0.16g of low - density polyethylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O
  • the O 2 -plastic ratio is 3:1; the reaction conditions are: reaction temperature 200°C, reaction time 60min, reaction pressure 0.5MPa; the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase products are carbon dioxide and oxygen;
  • Step 2 is the same as Example 1 Step 2; the catalyst preparation method is the same as Example 1.
  • Embodiment 8 is a diagrammatic representation of Embodiment 8
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 0.5% H2O2 hydrogen peroxide, load 0.16g of low - density polyethylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O
  • the O 2 -plastic ratio is 5:1; the reaction conditions are: reaction temperature 200°C, reaction time 60min, reaction pressure 0.5MPa; the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase products are carbon dioxide and oxygen;
  • Step 2 is the same as Example 1 Step 2; the catalyst preparation method is the same as Example 1.
  • Embodiment 9 is a diagrammatic representation of Embodiment 9:
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 0.5% H2O2 hydrogen peroxide, load 0.16g of low - density polyethylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O
  • the O 2 -plastic ratio is 20:1; the reaction conditions are: reaction temperature 200°C, reaction time 60min, reaction pressure 0.5MPa; the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase product is carbon dioxide and oxygen;
  • Step 2 is the same as Example 1 Step 2; the catalyst preparation method is the same as Example 1.
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 0.5% H2O2 hydrogen peroxide, load 0.16g of low - density polyethylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O
  • the O 2 -plastic ratio is 40:1; the reaction conditions are: reaction temperature 200°C, reaction time 60min, reaction pressure 0.5MPa; the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase products are carbon dioxide and oxygen;
  • Step 2 is the same as Example 1 Step 2; the catalyst preparation method is the same as Example 1.
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 0.5% H2O2 hydrogen peroxide, load 0.16g of low - density polyethylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O
  • the O 2 -plastic ratio is 80:1; the reaction conditions are: reaction temperature 200°C, reaction time 60min, reaction pressure 0.5MPa; the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase products are carbon dioxide and oxygen;
  • Step 2 is the same as Example 1 Step 2; the catalyst preparation method is the same as Example 1.
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 0.5% H2O2 hydrogen peroxide, load 0.16g of low - density polyethylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O
  • the O 2 -plastic ratio is 10:1; the reaction conditions are: reaction temperature 180°C, reaction time 60min, reaction pressure 0.5MPa; the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase products are carbon dioxide and oxygen;
  • Step 2 is the same as Example 1 Step 2; the catalyst preparation method is the same as Example 1.
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 0.5% H2O2 hydrogen peroxide, load 0.16g of low - density polyethylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O
  • the O 2 -plastic ratio is 10:1;
  • the reaction conditions are: reaction temperature 190°C, reaction time 60min, reaction pressure 0.5MPa;
  • the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase product is carbon dioxide and oxygen;
  • Step 2 is the same as Example 1 Step 2; the catalyst preparation method is the same as Example 1.
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 0.5% H2O2 hydrogen peroxide, load 0.16g of low- density polyethylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O
  • the O 2 -plastic ratio is 10:1; the reaction conditions are: reaction temperature 210°C, reaction time 60min, reaction pressure 2MPa; the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase products are carbon dioxide and oxygen;
  • Step 2 is the same as Example 1 Step 2; the catalyst preparation method is the same as Example 1.
  • Step 1 is the same as Step 1 in Example 1.
  • Step 2 Pass the liquid-phase product of the first-stage oxidation pretreatment into a reactor filled with a Ni monometallic catalyst supported by mesoporous carbon.
  • the reaction conditions are: reaction temperature 240°C, reaction time 120min, reaction pressure 4MPa.
  • the preparation method of the Ni single metal catalyst supported by mesoporous carbon is as follows: sieve the mesoporous carbon to 120-150 mesh; After soaking in deionized water with uniform stirring at room temperature for 12 hours, continue stirring at 80°C until the water evaporates to dryness, and dry the obtained sample in an oven at 105°C for 12 hours; at 550°C, 10% H 2 -90% Reduction in Ar for 4 hours.
  • Step 1 is the same as Step 1 in Example 1.
  • Step 2 Pass the liquid-phase product of the first-stage oxidation pretreatment into a reactor filled with a mesoporous carbon-supported Pt monometallic catalyst.
  • the reaction conditions are: reaction temperature 240°C, reaction time 120min, reaction pressure 4MPa.
  • the preparation method of the Pt monometallic catalyst supported by mesoporous carbon is as follows: sieve the mesoporous carbon to 120-150 mesh; add a certain amount of mesoporous carbon and chloroplatinic acid into deionized water according to the total metal loading of 5wt% , uniformly stirred and impregnated at room temperature for 12 hours, continued to stir at 80°C until the water evaporated to dryness, and dried the obtained sample in an oven at 105 °C for 12 hours; 4 hours.
  • Step 1 is the same as Step 1 in Example 1.
  • Step 2 Pass the liquid phase product of the first stage oxidation pretreatment into the reactor filled with the Ru-Ni bimetallic catalyst supported by mesoporous carbon, the Ru and Ni in the Ru-Ni bimetallic catalyst supported by mesoporous carbon
  • the load-to-mass ratio is 4:1.
  • the reaction conditions are: reaction temperature 240°C, reaction time 120min, reaction pressure 4MPa.
  • the preparation method of the Ru-Ni bimetallic catalyst supported by mesoporous carbon is as follows: sieve the mesoporous carbon to 120-150 mesh; Hydrate and ruthenium chloride were added to deionized water in proportion, stirred uniformly at room temperature and impregnated for 12 hours, then continued to stir at 80°C until the water evaporated to dryness, and dried the obtained sample in an oven at 105°C for 12 hours; Reduction in 10% H 2 -90% Ar for 4 hours at °C.
  • Step 1 is the same as Step 1 in Example 1.
  • Step 2 Pass the liquid phase product of the first stage oxidation pretreatment into the reactor filled with the Ru-Ni bimetallic catalyst supported by mesoporous carbon, the Ru and Ni in the Ru-Ni bimetallic catalyst supported by mesoporous carbon
  • the load-to-mass ratio is 1:1.
  • the reaction conditions are: reaction temperature 240°C, reaction time 120min, reaction pressure 4MPa.
  • the preparation method of the Ru-Ni bimetallic catalyst supported by mesoporous carbon is as follows: sieve the mesoporous carbon to 120-150 mesh; Hydrate and ruthenium chloride were added to deionized water in proportion, stirred uniformly at room temperature and impregnated for 12 hours, then continued to stir at 80°C until the water evaporated to dryness, and dried the obtained sample in an oven at 105°C for 12 hours; Reduction in 10% H 2 -90% Ar for 4 hours at °C.
  • Step 1 is the same as Step 1 in Example 1.
  • Step 2 Pass the liquid phase product of the first stage oxidation pretreatment into the reactor filled with the Ru-Ni bimetallic catalyst supported by mesoporous carbon, the Ru and Ni in the Ru-Ni bimetallic catalyst supported by mesoporous carbon
  • the load-to-mass ratio is 1:4.
  • the reaction conditions are: reaction temperature 240°C, reaction time 120min, reaction pressure 4MPa.
  • the preparation method of the Ru-Ni bimetallic catalyst supported by mesoporous carbon is as follows: sieve the mesoporous carbon to 120-150 mesh; Hydrate and ruthenium chloride were added to deionized water in proportion, stirred uniformly at room temperature and impregnated for 12 hours, then continued to stir at 80°C until the water evaporated to dryness, and dried the obtained sample in an oven at 105°C for 12 hours; Reduction in 10% H 2 -90% Ar for 4 hours at °C.
  • Step 1 is the same as Step 1 in Example 1.
  • Step 2 Pass the liquid phase product of the first stage oxidation pretreatment into the reactor filled with the Ru-Ni bimetallic catalyst supported by mesoporous carbon, the Ru-Ni bimetallic catalyst supported by mesoporous carbon is the Mesoporous carbon-supported Ru-Ni bimetallic catalyst recovered after use.
  • the reaction conditions are: reaction temperature 240°C, reaction time 120min, reaction pressure 4MPa.
  • Step 1 is the same as Step 1 in Example 1.
  • Step 2 Pass the liquid phase product of the first stage oxidation pretreatment into the reactor filled with the Ru-Ni bimetallic catalyst supported by mesoporous carbon, the Ru-Ni bimetallic catalyst supported by mesoporous carbon is the Mesoporous carbon-supported Ru-Ni bimetallic catalyst recovered after use.
  • the reaction conditions are: reaction temperature 240°C, reaction time 120min, reaction pressure 4MPa.
  • Step 1 is the same as Step 1 in Example 1.
  • Step 2 Pass the liquid phase product of the first stage oxidation pretreatment into the reactor filled with the Ru-Ni bimetallic catalyst supported by mesoporous carbon, the Ru-Ni bimetallic catalyst supported by mesoporous carbon is the one in Example 21 Mesoporous carbon-supported Ru-Ni bimetallic catalyst recovered after use.
  • the reaction conditions are: reaction temperature 240°C, reaction time 120min, reaction pressure 4MPa.
  • Step 1 is the same as Step 1 in Example 1.
  • Step 2 Pass the liquid-phase product of the first-stage oxidation pretreatment into a reactor filled with a mesoporous carbon-supported Ru monometallic catalyst, and the Ru monometallic catalyst is the Ru monometallic catalyst recovered in Example 5.
  • the reaction conditions are: reaction temperature 240°C, reaction time 120min, reaction pressure 4MPa.
  • Step 1 is the same as Step 1 in Example 1.
  • Step 2 Pass the liquid phase product of the first stage oxidation pretreatment into the reactor filled with the Ru-Ni bimetallic catalyst supported by mesoporous carbon, the Ru-Ni bimetallic catalyst supported by mesoporous carbon is the Mesoporous carbon-supported Ru-Ni bimetallic catalyst recovered after use.
  • the reaction conditions are: reaction temperature 240°C, reaction time 120min, reaction pressure 4MPa.
  • Step 1 is the same as Step 1 in Example 1.
  • Step 2 Pass the liquid phase product of the first stage oxidation pretreatment into the reactor filled with the Ru-Ni bimetallic catalyst supported by mesoporous carbon, the Ru-Ni bimetallic catalyst supported by mesoporous carbon is the Mesoporous carbon-supported Ru-Ni bimetallic catalyst recovered after use.
  • the reaction conditions are: reaction temperature 240°C, reaction time 120min, reaction pressure 4MPa.
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 0.5% H2O2 hydrogen peroxide, load 0.16g of high - density polyethylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O
  • the O 2 -plastic ratio is 10:1; the reaction conditions are: reaction temperature 200°C, reaction time 60min, reaction pressure 0.5MPa; the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase product is carbon dioxide and oxygen;
  • Step 2 is the same as step 2 of Example 17; the preparation method of the catalyst is the same as that of Example 17.
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 2% H2O2 hydrogen peroxide, load 0.16g of polypropylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O2 -
  • the plastic ratio is 10:1; the reaction conditions are: reaction temperature 200°C, reaction time 60min, reaction pressure 0.5MPa; the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase product is carbon dioxide and oxygen;
  • Step 2 is the same as Example 1 Step 2; the catalyst preparation method is the same as Example 1.
  • Step 1 Dilute commercial 30 % H2O2 hydrogen peroxide with deionized water , prepare 80ml 1% H2O2 hydrogen peroxide, load 0.16g polypropylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that H2O2 -
  • the plastic ratio is 10:1; the reaction conditions are: reaction temperature 200°C, reaction time 60min, reaction pressure 0.5MPa; the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase product is carbon dioxide and oxygen;
  • Step 2 is the same as Example 1 Step 2; the catalyst preparation method is the same as Example 1.
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 0.5% H2O2 hydrogen peroxide, load 0.16g of high - density polyethylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O
  • the O 2 -plastic ratio is 10:1;
  • the reaction conditions are: reaction temperature 200°C, reaction time 30min, reaction pressure 1MPa;
  • the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase product is carbon dioxide and oxygen;
  • Step 2 Pass the liquid phase product of the first stage oxidation pretreatment into the reactor filled with the Ru-Ni bimetallic catalyst supported by mesoporous carbon, the Ru and Ni in the Ru-Ni bimetallic catalyst supported by mesoporous carbon
  • the load-to-mass ratio is 4:1.
  • the reaction conditions are: reaction temperature 200°C, reaction time 180min, reaction pressure 2MPa.
  • the catalyst preparation method is the same as in Example 16.
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 0.5% H2O2 hydrogen peroxide, load 0.16g of high - density polyethylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O
  • the O 2 -plastic ratio is 10:1; the reaction conditions are: reaction temperature 200°C, reaction time 90min, reaction pressure 1MPa; the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase product is carbon dioxide and oxygen;
  • Step 2 is the same as step 2 of Example 29; the preparation method of the catalyst is the same as that of Example 17.
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 0.5% H2O2 hydrogen peroxide, load 0.16g of low - density polyethylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O
  • the O 2 -plastic ratio is 10:1;
  • the reaction conditions are: reaction temperature 150°C, reaction time 60min, reaction pressure 2MPa;
  • the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase product is carbon dioxide and oxygen;
  • Step 2 is the same as Example 1 Step 2; the catalyst preparation method is the same as Example 1.
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 0.5% H2O2 hydrogen peroxide, load 0.16g of low - density polyethylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O
  • the O 2 -plastic ratio is 10:1;
  • the reaction conditions are: reaction temperature 220°C, reaction time 60min, reaction pressure 2MPa;
  • the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase product is carbon dioxide and oxygen;
  • Step 2 is the same as Example 1 Step 2; the catalyst preparation method is the same as Example 1.
  • Step 1 Dilute commercial 30% H2O2 hydrogen peroxide with deionized water to prepare 80ml of 0.5% H2O2 hydrogen peroxide, load 0.16g of low- density polyethylene and the prepared dilute hydrogen peroxide into the hydrothermal reactor so that the H2O
  • the O 2 -plastic ratio is 10:1;
  • the reaction conditions are: reaction temperature 230°C, reaction time 60min, reaction pressure 2MPa;
  • the main liquid phase product obtained by oxidation pretreatment is acetic acid, and the gas phase products are carbon dioxide and oxygen;
  • Step 2 is the same as Example 1 Step 2; the catalyst preparation method is the same as Example 1.
  • MEC is mesoporous carbon
  • Ru/MEC is Ru monometallic catalyst supported on mesoporous carbon
  • Ni/MEC is Ni monometallic catalyst supported on mesoporous carbon
  • Pt/MEC is Pt monometallic catalyst supported on mesoporous carbon
  • 4Ru-1Ni/MEC is a Ru-Ni bimetallic catalyst supported by mesoporous carbon, the mass ratio of Ru and Ni is 4:1
  • 1Ru-1Ni/MEC is a Ru-Ni bimetallic catalyst supported by mesoporous carbon, Ru and Ni
  • the loading mass ratio of Ni is 1:1
  • 1Ru-4Ni/MEC is a Ru-Ni bimetallic catalyst supported by mesoporous carbon, and the loading mass ratio of Ru and Ni is 1:4
  • H 2 O 2 -plastic ratio is hydrogen peroxide- The mass ratio of polyolefin.
  • the H2O2 concentration was further reduced to 0.25%, the H2 production decreased by 4.5% from 10.83 mol/kg to 10.34 mol/kg, which was caused by the insufficient oxidation caused by the lower H2O2 concentration.
  • the CO2 production was 3.65 mol/kg. This is because CO2 is not only produced by the peroxidation of carboxylic acids during oxidative pretreatment, but also directly formed during the oxidative cleavage of CC bonds.
  • the high concentration of carbon dioxide produced by the oxidation pretreatment process has the potential to be used for further carbon capture, utilization and storage.
  • H 2 O 2 is a strong oxidizing agent.
  • the raw material will be over-oxidized, which will cause oxidative cracking of the CC bond, resulting in a higher yield of by-product carbon dioxide and lower H 2 O 2 Concentration, carbon dioxide production rate is significantly reduced, which can effectively weaken the overoxidation of carboxylic acid produced in the pre-oxidation stage, so as to ensure that more carboxylic acid participates in the reaction in the second hydrogen production process and promote hydrogen production.
  • Example 5 when the pretreatment temperature in the first section was 200°C, the hydrogen production rate and concentration in the synthesis gas obtained in the second section process were the highest;
  • the ranking of Ru, Ni, Pt monometallic catalysts supported by mesoporous carbon and Ru-Ni bimetallic catalysts for the catalytic performance of the second stage of the present invention is Ru/MEC >4Ru-1Ni/MEC>1Ru-1Ni/MEC>Pt/MEC>1Ru-4Ni/MEC>Ni/MEC, the pore structure of the fresh catalyst in embodiment 5 and embodiment 14-17 is characterized, and its result is as follows Table 2 shows:
  • the XRD patterns of Ni/MEC, Ru/MEC and bimetallic catalysts with different molar ratios are shown in Fig. 8 .
  • Ni/MEC there are larger peaks at 44.5° and 51.5°, corresponding to Ni (111) and (200) planes, respectively.
  • the weak diffraction peaks of metallic Ru in Ru/MEC and Ru-Ni bimetallic catalysts indicate that Ru nanoparticles are small and highly dispersed on the surface of MEC [38,45,49,50], which is consistent with the scanning electron microscopy results, and the small nanoparticle Particles can provide more surface atoms, thus improving their catalytic activity.
  • Example 5 Example 17 and Examples 20-25, the Ru-Ni bimetallic catalyst supported by mesoporous carbon exhibits higher stability than Ru single metal under the operating conditions of the present invention.
  • a is the TEM and particle size distribution image of Ni/MEC
  • b is the TEM and particle size distribution image of Ru/MEC
  • c is the TEM and particle size distribution images of 4Ru-1Ni/MEC
  • the average particle size of Ru-Ni is 14.1nm, which is larger than that of monometallic Ru/MEC (average particle size is 7.2nm).
  • This phenomenon may be due to the synergistic effect of Ru and Ni. It was observed that Ru and Ni atoms were almost at the same position, and each atom was not separated in the entire imaging area, indicating that a uniform Ru-Ni alloy structure was formed.

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Abstract

本发明公开了一种低温降解聚烯烃废塑料制备富氢合成气的方法，包括：称取聚烯烃塑料1重量份，含有0.25％-6％H2O2的双氧水3-80重量份；将称取的聚烯烃塑料和双氧水装填至水热反应器，进行氧化预处理反应，反应温度为150-230℃，反应压力为0.5-2MPa，反应时间30-90min，反应结束后得到液相产物和气相产物；在另一个水热反应器中装填介孔碳负载的金属基催化剂，再将得到的液相产物通入水热反应器中，进行重整反应，得到富氢合成气产物。整个过程氢气产率接近11mol/kg塑料，富氢合成气中氢气浓度接近55％。本发明通过联合低温氧化预处理和重整过程解决了在低温下(<250℃)聚烯烃废塑料难以转化为氢气的瓶颈问题。

Description

一种低温降解聚烯烃废塑料制备富氢合成气的方法 【技术领域】
本发明涉及塑料降解的技术领域，特别是低温降解聚烯烃废塑料制备富氢合成气的技术领域。
【背景技术】
塑料作为主要的合成材料之一，在材料领域占据着重要的位置。我国是世界上第一大塑料生产国，每年产生巨大数量的塑料垃圾，一部分难以分解的塑料进入陆地自然环境以及海洋中，对生态环境造成巨大影响。目前比较典型的几种废旧塑料包括聚乙烯、聚丙烯、聚对苯二甲酸乙二醇酯、聚氯乙烯、聚碳酸酯、聚苯乙烯以及丙烯腈-丁二烯-苯乙烯塑料等。其中聚乙烯和聚丙烯等聚烯烃塑料用途最广，且在废旧塑料总量中占比最大。另外，作为医用口罩的主要材质，在COVID-19期间，聚丙烯原材料以及其废弃物的产量急剧增长，而目前常用的处理生活塑料垃圾的主要方法是填埋、焚烧等，这两种处理方法在很大程度上会造成二次污染以及资源的浪费。因此，将塑料高效地转化为氢能等清洁能源成为热点。
液相重整是一种低温低压制氢技术，可以在200-260℃，1.5-4MPa的水热条件下，利用催化剂的催化作用将液态含氧有机物转化为氢气，而废旧聚烯烃塑料作为一种固废，且不含氧原子，不能直接进行液相重整制氢。
目前废旧塑料制备氢气的方法主要以高温热解气化(500-800℃)为主，同时也伴随焦炭和焦油等副产物的产生，较高的反应温度也造成较高成本的投入。另外已有研究(Waste management 2020,102,520-7,Energy 2020，191，116527)提出利用超临界水气化(T>374℃,P>22.1MPa)将塑料转化为氢气，由于超临界水气化的运行对设备的要求较高，所以在工业应用中存在一定的局限性，另外目前使用超临界水气化对聚乙烯和聚丙烯进行转化制氢得到的合成气中的氢气产率(2-5mol/kg塑料)和氢气浓度并不高(10-40％)。
【发明内容】
本发明的目的就是解决现有技术中的问题，提出一种低温降解聚烯烃废塑料制备富氢合成气的方法，采用氧化预处理与重整反应相结合的两步法，在第一阶段，使用稀H 2O 2溶液在低于250℃的反应温度下对 聚乙烯和聚丙烯等聚烯烃废塑料进行氧化预处理，在第二阶段，针对预处理得到的液相在高效碳基催化剂的催化下进行低温重整制氢，进而实现聚烯烃塑料在温和条件下的高效产氢。
为实现上述目的，本发明提出了一种低温降解聚烯烃废塑料制备富氢合成气的方法，采用氧化预处理与重整反应相结合的两步法，包括如下步骤：
(1)称取聚烯烃塑料1重量份，双氧水3重量份以上，所述双氧水含有H 2O 2的浓度为0.25％-6％；
(2)将称取的聚烯烃塑料和双氧水装填至水热反应器，进行氧化预处理反应，反应温度为150-230℃，反应结束后得到液相产物和气相产物；
反应液中的H 2O 2完全分解，经检测，产物中不含H 2O 2，所以不会有残留的H 2O 2对第二段的重整反应的催化剂产生负面作用；
(3)在另一个水热反应器中装填介孔碳负载的金属基催化剂，再将步骤(2)得到的液相产物通入水热反应器中，进行重整反应，得到富氢合成气产物。步骤(1)、步骤(2)为氧化预处理阶段，步骤(3)为重整反应阶段。
作为优选，所述步骤(1)中的双氧水中的H 2O 2的含量为0.5-2％；
作为一种强氧化剂，高浓度的H 2O 2容易导致C-C键氧化裂解的恶劣条件，H 2O 2浓度太低又会导致氧化不足，所以0.25％-6％H 2O 2的双氧水能够有效实现在低温条件下对聚烯烃塑料的预氧化，且H 2O 2的含量为0.5-2％时，第二段重整反应得到的氢气产率和浓度最佳。
作为优选，所述步骤(1)中的双氧水的重量份为3-80重量份；
作为优选，所述步骤(1)中双氧水的重量份为5-10份；
氧化预处理中残留的双氧水对第二段重整反应中的金属催化剂产生氧化等负面影响，在较高的H 2O 2-聚烯烃塑料的重量比下，重整反应工艺会产生更多的CO 2，导致气体产物中H 2的摩尔分数降低，当双氧水的重量份为5-10份最佳。
作为优选，所述步骤(2)中反应压力为0.5-2MPa，反应时间30-90min。
作为优选，所述步骤(2)中反应温度为190-200℃，反应压力为1MPa，反应时间为30-60min。
作为优选，所述步骤(2)中，反应温度为200℃，反应时间为60min；
温度过低时，聚烯烃塑料氧化反应减弱，温度过高时，有机物可能发生脱羧反应，即长链羧酸的热裂解，氧化时间过长，对聚烯烃塑料氧化反应和重整反应都不利。
作为优选，所述步骤(2)中得到的液相产物的主要成分是乙酸，气相产物是氧气和二氧化碳；
液相产物以乙酸为主，甲酸，丙酸等其他短链小分子酸含量很低，不会对重整反应的催化剂的活性造成不利影响。
作为优选，所述步骤(3)中重整反应的反应温度为200-240℃，反应压力为2-4MPa，反应时间为120-180min。
作为优选，所述步骤(3)中的介孔碳负载的金属基催化剂为介孔碳负载的Ru单金属、介孔碳负载的Ni单金属、介孔碳负载Pt单金属和介孔碳负载Ru-Ni双金属中的一种或多种；
选用的介孔碳的比表面积为1400-1500m 2/g，可提供更多的活性位点。
作为优选，所述步骤(3)中的介孔碳负载的金属基催化剂为介孔碳负载的Ru-Ni双金属催化剂，Ru和Ni的负载质量比为4:1、1:1或1:4；
介孔碳负载的Ru单金属催化剂对聚烯烃氧化预处理表现出最高的H 2选择性，以及在介孔碳负载的Ru单金属催化剂的催化下得到最高的氢气产率和氢气浓度，但考虑到Ru金属价格昂贵，且单金属催化剂在水热环境中稳定性不高，易失活，在保证负载金属总量不变的情况下添加非贵金属来取代部分活性金属Ru可以有效地降低催化剂的成本。并且本发明提供的介孔碳负载的Ru-Ni双金属催化剂实现了氢气产率成倍数的增加，且在制备过程中形成RuNi合金大大提高了催化剂的稳定性。
作为优选，所述聚烯烃塑料选自聚丙烯、低密度聚乙烯和高密度聚乙烯的一种或多种。
作为优选，所述的介孔碳负载的金属基催化剂的制备步骤为：先将介孔碳筛分至120-150目；按照5wt％总金属负载量，将一定量的介孔碳和可溶性金属前驱物加入到去离子水中，在室温下均匀搅拌浸渍12小时后，在80℃下继续搅拌至水分蒸干，将得到的样品在105℃烘箱中干燥12小时；最后在550℃下，10％H 2-90％Ar中还原4个小时。
本发明采用氧化预处理与重整反应相结合的两步法，实现在低温条件下对聚烯烃进行降解，并高效制氢，两个阶段协同作用，产生如下有益效果：
(1)本发明采用两步法制氢，一方面实现了低于250℃的温度下利用聚烯烃废塑料高效产氢，氢气产率接近11mol/kg塑料，降低了能耗和运行成本，另一方面实现了聚烯烃废塑料的高效降解，在处理聚烯烃塑料垃圾方面具有较高的利用价值；
(2)在氧化预处理阶段，H 2O 2作为一种强氧化剂，在浓度较高(6-8％)的情况下，原料会过度氧化，使C-C键发生氧化裂解，导致副产物二氧化碳产率较高，控制H 2O 2浓度为0.25％-6％，二氧化碳产率在明显下降，可以有效地减弱预氧化阶段所产生的羧酸的过氧化，从而保证第二段制氢过程中有更多的羧酸参与反应，促进氢气生产；
(3)控制双氧水和聚烯烃的重量份比为5：1-10:1，使氧化预处理阶段产生的产物不含双氧水，不会有残留的双氧水对第二段重整反应中的金属催化剂产生氧化等负面影响；
(4)反应液中的低浓度双氧水在低温水热环境下，可以对聚烯烃塑料中的碳碳键进行选择性氧化断裂，形成醛类等小分子中间产物后被快速氧化成乙酸等有机酸从而实现在低温条件下对聚烯烃塑料的降解；
(5)本发明在第一段的氧化预处理反应中，得到以乙酸为主的产物，甲酸，丙酸等其他短链小分子酸含量很低，乙酸的产率为1.5-2mol/kg塑料，乙酸的反应活性低于甲酸，不会对碳基催化剂的活性造成不利影响，有利于第二段的重整反应制氢的进行；
(6)本发明选择的介孔碳负载的Ru-Ni双金属催化剂实现了氢气产率成倍数的增加，且在制备过程中形成RuNi合金，大大提高了催化剂的稳定性；
(7)与聚烯烃塑料超临界水气化制氢相比，本发明不仅大大降低了反应温度和压力，实现了聚烯烃温和水热条件下制氢，而且得到的氢气产率及氢气浓度也更高；
(8)介孔碳负载的Ru单金属催化剂对聚烯烃氧化预处理表现出最高的H 2选择性，以及在介孔碳负载的Ru单金属催化剂的催化下得到最高的氢气产率和氢气浓度，但考虑到Ru金属价格昂贵，且单金属催化剂在水热环境中稳定性不高，易失活，在保证负载金属总量不变的情况下添加非贵金属来取代部分活性金属Ru可以有效地降低催化剂的成本。并且本发明提供的介孔碳负载的Ru-Ni双金属催化剂实现了氢气产率成倍数的增加，且在制备过程中形成RuNi合金大大提高了催化剂的稳定性。
【附图说明】
图1是本发明H 2O 2的浓度与各产物产量的变化图；
图2是本发明H 2O 2的浓度与合成气产物中气体组成图；
图3是本发明H 2O 2的浓度与氢气选择性的关系图；
图4是本发明双氧水-聚烯烃质量比与合成气产率的关系图；
图5是本发明H 2O 2浓度与预氧化处理产生的二氧化碳关系图；
图6是本发明合成的新鲜催化剂的氮气吸附-脱附等温线；
图7是本发明合成的新鲜催化剂的孔径分布示意图；
图8是本发明合成的新鲜催化剂的XRD示意图；
图9是本发明的介孔碳负载催化剂的TEM图像和粒径分布图。
【具体实施方式】
实施例1:
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 6％H 2O 2双氧水，将0.16g低密度聚乙烯和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为10：1；反应条件为：反应温度200℃，反应时间60min,反应压力0.5MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2：将第一段氧化预处理的液相产物通入装填介孔碳负载的Ru单金属催化剂的反应器。反应条件为：反应温度240℃，反应时间120min,反应压力4MPa。
介孔碳负载的Ru单金属催化剂的制备方法为：将介孔碳筛分至120-150目；按照5wt％总金属负载量，将一定量的介孔碳和氯化钌加入到去离子水中，在室温下均匀搅拌浸渍12小时后，在80℃下继续搅拌至水分蒸干，将得到的样品在105℃烘箱中干燥12小时；在550℃下，10％H 2-90％Ar中还原4个小时。
实施例2:
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 4％H 2O 2双氧水，将0.16g低密度聚乙烯和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为10：1；反应条件为：反应温度200℃，反应时间60min,反应压力0.5MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2同实施例1步骤2；催化剂制备方法同实施例1。
实施例3：
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 2％H 2O 2双氧水，将0.16g低密度聚乙烯和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为10：1；反应条件为：反应温度200℃，反应时间60min,反应压力0.5MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2同实施例1步骤2；催化剂制备方法同实施例1。
实施例4：
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 1％H 2O 2双氧水，将0.16g低密度聚乙烯和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为10：1；反应条件为：反应温度200℃，反应时间60min,反应压力0.5MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2同实施例1步骤2；催化剂制备方法同实施例1。
实施例5：
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 0.5％H 2O 2双氧水，将0.16g低密度聚乙烯和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为10：1；反应条件为：反应温度200℃，反应时间60min,反应压力0.5MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2同实施例1步骤2；催化剂制备方法同实施例1。
实施例6：
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 0.25％H 2O 2双氧水，将0.16g低密度聚乙烯和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为10：1；反应条件为：反应温度200℃，反应时间60min,反应压力0.5MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2同实施例1步骤2；催化剂制备方法同实施例1。
实施例7：
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 0.5％H 2O 2双氧水，将0.16g低密度聚乙烯和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为3：1；反应条件为：反应温度200℃，反应时 间60min,反应压力0.5MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2同实施例1步骤2；催化剂制备方法同实施例1。
实施例8：
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 0.5％H 2O 2双氧水，将0.16g低密度聚乙烯和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为5：1；反应条件为：反应温度200℃，反应时间60min,反应压力0.5MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2同实施例1步骤2；催化剂制备方法同实施例1。
实施例9：
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 0.5％H 2O 2双氧水，将0.16g低密度聚乙烯和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为20：1；反应条件为：反应温度200℃，反应时间60min,反应压力0.5MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2同实施例1步骤2；催化剂制备方法同实施例1。
实施例10：
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 0.5％H 2O 2双氧水，将0.16g低密度聚乙烯和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为40：1；反应条件为：反应温度200℃，反应时间60min,反应压力0.5MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2同实施例1步骤2；催化剂制备方法同实施例1。
实施例11：
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 0.5％H 2O 2双氧水，将0.16g低密度聚乙烯和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为80：1；反应条件为：反应温度200℃，反应时间60min,反应压力0.5MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2同实施例1步骤2；催化剂制备方法同实施例1。
实施例12：
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 0.5％H 2O 2双氧水，将0.16g低密度聚乙烯 和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为10：1；反应条件为：反应温度180℃，反应时间60min,反应压力0.5MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2同实施例1步骤2；催化剂制备方法同实施例1。
实施例13：
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 0.5％H 2O 2双氧水，将0.16g低密度聚乙烯和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为10：1；反应条件为：反应温度190℃，反应时间60min,反应压力0.5MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2同实施例1步骤2；催化剂制备方法同实施例1。
实施例14：
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 0.5％H 2O 2双氧水，将0.16g低密度聚乙烯和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为10：1；反应条件为：反应温度210℃，反应时间60min,反应压力2MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2同实施例1步骤2；催化剂制备方法同实施例1。
实施例15：
步骤1同实施例1步骤1。
步骤2：将第一段氧化预处理的液相产物通入装填介孔碳负载的Ni单金属催化剂的反应器。反应条件为：反应温度240℃，反应时间120min,反应压力4MPa。
介孔碳负载的Ni单金属催化剂的制备方法为：将介孔碳筛分至120-150目；按照5wt％总金属负载量，将一定量的介孔碳和氯化镍六水合物加入到去离子水中，在室温下均匀搅拌浸渍12小时后，在80℃下继续搅拌至水分蒸干，将得到的样品在105℃烘箱中干燥12小时；在550℃下，10％H 2-90％Ar中还原4个小时。
实施例16：
步骤1同实施例1步骤1。
步骤2：将第一段氧化预处理的液相产物通入装填介孔碳负载的Pt单金属催化剂的反应器。反应条 件为：反应温度240℃，反应时间120min,反应压力4MPa。
介孔碳负载的Pt单金属催化剂的制备方法为：将介孔碳筛分至120-150目；按照5wt％总金属负载量，将一定量的介孔碳和氯铂酸加入到去离子水中，在室温下均匀搅拌浸渍12小时后，在80℃下继续搅拌至水分蒸干，将得到的样品在105℃烘箱中干燥12小时；在550℃下，10％H 2-90％Ar中还原4个小时。
实施例17：
步骤1同实施例1步骤1。
步骤2：将第一段氧化预处理的液相产物通入装填介孔碳负载的Ru-Ni双金属催化剂的反应器，所述介孔碳负载的Ru-Ni双金属催化剂中Ru和Ni的负载质量比为4:1。反应条件为：反应温度240℃，反应时间120min,反应压力4MPa。
所述介孔碳负载的Ru-Ni双金属催化剂的制备方法为：将介孔碳筛分至120-150目；按照5wt％总金属负载量，将一定量的介孔碳、氯化镍六水合物和氯化钌按比例加入到去离子水中，在室温下均匀搅拌浸渍12小时后，在80℃下继续搅拌至水分蒸干，将得到的样品在105℃烘箱中干燥12小时；在550℃下，10％H 2-90％Ar中还原4个小时。
实施例18：
步骤1同实施例1步骤1。
步骤2：将第一段氧化预处理的液相产物通入装填介孔碳负载的Ru-Ni双金属催化剂的反应器，所述介孔碳负载的Ru-Ni双金属催化剂中Ru和Ni的负载质量比为1:1。反应条件为：反应温度240℃，反应时间120min,反应压力4MPa。
所述介孔碳负载的Ru-Ni双金属催化剂的制备方法为：将介孔碳筛分至120-150目；按照5wt％总金属负载量，将一定量的介孔碳、氯化镍六水合物和氯化钌按比例加入到去离子水中，在室温下均匀搅拌浸渍12小时后，在80℃下继续搅拌至水分蒸干，将得到的样品在105℃烘箱中干燥12小时；在550℃下，10％H 2-90％Ar中还原4个小时。
实施例19：
步骤1同实施例1步骤1。
步骤2：将第一段氧化预处理的液相产物通入装填介孔碳负载的Ru-Ni双金属催化剂的反应器，所述介孔碳负载的Ru-Ni双金属催化剂中Ru和Ni的负载质量比为1:4。反应条件为：反应温度240℃，反应时间120min,反应压力4MPa。
所述介孔碳负载的Ru-Ni双金属催化剂的制备方法为：将介孔碳筛分至120-150目；按照5wt％总金属负载量，将一定量的介孔碳、氯化镍六水合物和氯化钌按比例加入到去离子水中，在室温下均匀搅拌浸渍12小时后，在80℃下继续搅拌至水分蒸干，将得到的样品在105℃烘箱中干燥12小时；在550℃下，10％H 2-90％Ar中还原4个小时。
实施例20：
步骤1同实施例1步骤1。
步骤2：将第一段氧化预处理的液相产物通入装填介孔碳负载的Ru-Ni双金属催化剂的反应器，所述介孔碳负载的Ru-Ni双金属催化剂为实施例17中使用后回收的介孔碳负载的Ru-Ni双金属催化剂。反应条件为：反应温度240℃，反应时间120min,反应压力4MPa。
实施例21：
步骤1同实施例1步骤1。
步骤2：将第一段氧化预处理的液相产物通入装填介孔碳负载的Ru-Ni双金属催化剂的反应器，所述介孔碳负载的Ru-Ni双金属催化剂为实施例20中使用后回收的介孔碳负载的Ru-Ni双金属催化剂。反应条件为：反应温度240℃，反应时间120min,反应压力4MPa。
实施例22：
步骤1同实施例1步骤1。
步骤2：将第一段氧化预处理的液相产物通入装填介孔碳负载的Ru-Ni双金属催化剂的反应器，所述介孔碳负载的Ru-Ni双金属催化剂为实施例21中使用后回收的介孔碳负载的Ru-Ni双金属催化剂。反应条件为：反应温度240℃，反应时间120min,反应压力4MPa。
实施例23：
步骤1同实施例1步骤1。
步骤2：将第一段氧化预处理的液相产物通入装填介孔碳负载的Ru单金属催化剂的反应器，所述Ru单金属催化剂为实施例5回收的Ru单金属催化剂。反应条件为：反应温度240℃，反应时间120min,反应压力4MPa。
实施例24：
步骤1同实施例1步骤1。
步骤2：将第一段氧化预处理的液相产物通入装填介孔碳负载的Ru-Ni双金属催化剂的反应器，所述介孔碳负载的Ru-Ni双金属催化剂为实施例23中使用后回收的介孔碳负载的Ru-Ni双金属催化剂。反应条件为：反应温度240℃，反应时间120min,反应压力4MPa。
实施例25：
步骤1同实施例1步骤1。
步骤2：将第一段氧化预处理的液相产物通入装填介孔碳负载的Ru-Ni双金属催化剂的反应器，所述介孔碳负载的Ru-Ni双金属催化剂为实施例24中使用后回收的介孔碳负载的Ru-Ni双金属催化剂。反应条件为：反应温度240℃，反应时间120min,反应压力4MPa。
实施例26：
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 0.5％H 2O 2双氧水，将0.16g高密度聚乙烯和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为10：1；反应条件为：反应温度200℃，反应时间60min,反应压力0.5MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2同实施例17步骤2；催化剂制备方法同实施例17。
实施例27：
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 2％H 2O 2双氧水，将0.16g聚丙烯和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为10：1；反应条件为：反应温度200℃，反应时间60min,反应压力0.5MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2同实施例1步骤2；催化剂制备方法同实施例1。
实施例28：
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 1％H 2O 2双氧水，将0.16g聚丙烯和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为10：1；反应条件为：反应温度200℃，反应时间60min,反应压力0.5MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2同实施例1步骤2；催化剂制备方法同实施例1。
实施例29：
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 0.5％H 2O 2双氧水，将0.16g高密度聚乙烯和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为10：1；反应条件为：反应温度200℃，反应时间30min,反应压力1MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2：将第一段氧化预处理的液相产物通入装填介孔碳负载的Ru-Ni双金属催化剂的反应器，所述介孔碳负载的Ru-Ni双金属催化剂中Ru和Ni的负载质量比为4:1。反应条件为：反应温度200℃，反应时间180min,反应压力2MPa。
催化剂制备方法同实施例16。
实施例30：
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 0.5％H 2O 2双氧水，将0.16g高密度聚乙烯和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为10：1；反应条件为：反应温度200℃，反应时间90min,反应压力1MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2同实施例29步骤2；催化剂制备方法同实施例17。
实施例31：
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 0.5％H 2O 2双氧水，将0.16g低密度聚乙烯和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为10：1；反应条件为：反应温度150℃，反应时间60min,反应压力2MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2同实施例1步骤2；催化剂制备方法同实施例1。
实施例32：
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 0.5％H 2O 2双氧水，将0.16g低密度聚乙烯 和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为10：1；反应条件为：反应温度220℃，反应时间60min,反应压力2MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2同实施例1步骤2；催化剂制备方法同实施例1。
实施例33：
步骤1：用去离子水稀释商用30％H 2O 2双氧水，制备80ml 0.5％H 2O 2双氧水，将0.16g低密度聚乙烯和制备的稀双氧水加载至水热反应器中，使得H 2O 2-塑料比为10：1；反应条件为：反应温度230℃，反应时间60min,反应压力2MPa；氧化预处理得到的主要液相产物为乙酸，气相产物为二氧化碳和氧气；
步骤2同实施例1步骤2；催化剂制备方法同实施例1。
将实施例1-33经过催化重整后得到的气相产物通过气相色谱进行测试，并计算得到相关指标，实验数据如表1所示：
表1
Figure PCTCN2021098607-appb-000001
Figure PCTCN2021098607-appb-000002
注：MEC为介孔碳；Ru/MEC为介孔碳负载的Ru单金属催化剂；Ni/MEC为介孔碳负载的Ni单金属催化剂；Pt/MEC为介孔碳负载的Pt单金属催化剂；4Ru-1Ni/MEC为介孔碳负载的Ru-Ni双金属催化剂，Ru和Ni的负载质量比为4:1；1Ru-1Ni/MEC为介孔碳负载的Ru-Ni双金属催化剂，Ru和Ni的负载质量比为1:1；1Ru-4Ni/MEC为介孔碳负载的Ru-Ni双金属催化剂，Ru和Ni的负载质量比为1:4；H 2O 2-塑料比即双氧水-聚烯烃的质量比。
由实施例1-6可得，第一段反应中双氧水中H 2O 2的浓度为0.25-1％时，第二段过程得到的氢气产率和浓度较好，且H 2O 2的浓度为0.5％时，制氢效果最佳；
根据实施例1-6研究H 2O 2的浓度与各产物产量的变化关系，结果如图1所示，图中，横坐标表示H 2O 2的浓度，单位为wt％，纵坐标表示各产物的产量，单位为mol/kg，图中C 1-C 3表示C 1-C 3烷烯烃，CO表示一氧化碳，CO 2表示二氧化碳，H 2表示氢气；由图1可得，随着H 2O 2浓度从8％(H 2产量3.05mol/kg)降低到0.5％(H 2产量10.83mol/kg)，H 2产量呈现出明显的增加趋势。但是当H 2O 2浓度进一步降低到0.25％时，H 2产量从10.83mol/kg下降到10.34mol/kg，下降了4.5％，这是由于H 2O 2浓度较低导致氧化不足所致。当H 2O 2浓度为0.25％时，CO 2产量为3.65mol/kg。这是因为在氧化预处理过程中CO 2不仅是由羧酸的过氧化产生，而且是在C-C键的氧化裂解过程中直接形成的。氧化预处理过程产生的高浓度二氧化碳有可能用于进 一步的碳捕获、利用和存储。
根据实施例1-6研究H 2O 2的浓度与合成气产物中气体组分的组成关系，结果如图2所示，图中，横坐标表示各气体组分的摩尔分数，纵坐标表示H 2O 2的浓度，单位为wt％，对于重整反应，产物合成气中H 2的摩尔分数大于40％，在所有H 2O 2浓度下，当H 2O 2浓度为0.5％时达到最大值(51.52％)。
H 2O 2作为一种强氧化剂，在浓度较高(6-8％)的情况下，原料会过度氧化，使C-C键发生氧化裂解，导致副产物二氧化碳产率较高，降低H 2O 2浓度，二氧化碳产率在明显下降，可以有效地减弱预氧化阶段所产生的羧酸的过氧化，从而保证第二段制氢过程中有更多的羧酸参与反应，促进氢气生产。
根据实施例1-6研究H 2O 2的浓度与氢气选择性的关系，结果如图3所示，图中，横坐标表示H 2O 2的浓度，单位为wt％，纵坐标表示二氧化碳在合成气中的摩尔分数和氢气选择性；由图3可得，重整反应过程中，随着H 2O 2浓度的降低，碳向CO 2的转化增加。
根据实施例5和实施例7-11研究双氧水-聚烯烃比例对合成气产率的影响，结果如图4所示，图中，横坐标表示双氧水-聚烯烃的质量比，纵坐标表示合成气的产量以及合成气中氢气的摩尔分数和合成气中二氧化碳的摩尔分数。由图4可得，双氧水-聚烯烃的质量比为10:1时，第二段过程得到的合成气中氢气浓度和合成气产量最佳。
根据实施例1-6研究H 2O 2浓度对预氧化处理产生的二氧化碳的影响，结果如图5所示，图中，左边横坐标表示H 2O 2的浓度，单位为wt％，右边横坐标表示双氧水-聚烯烃的质量比，纵坐标表示二氧化碳的产量，单位为mol/kg。由图5可得，氧化预处理过程产生的CO 2量随着塑料量的减少而增加。这可能是由于在C-C键的裂解过程中，更多的H 2O 2促进了CO 2的生成，而不是过度氧化。然而，在较高的双氧水-聚烯烃质量比下，重整反应工艺产生更多的CO 2，导致气体产物中H 2的摩尔分数降低。
综上，可以得出,第一段反应中双氧水中H 2O 2的浓度为0.25-1％时，第二段过程得到的氢气产率和浓度较好，且H 2O 2的浓度为0.5％时，制氢效果最佳。
根据实施例5和实施例12-14得出，第一段中预处理温度为200℃时，第二段过程得到的合成气中氢气产率和浓度最高；
根据实施例5和实施例15-19得出，介孔碳负载的Ru、Ni、Pt单金属催化剂以及Ru-Ni双金属催化 剂对于本发明中第二段催化性能的优劣排序为Ru/MEC>4Ru-1Ni/MEC>1Ru-1Ni/MEC>Pt/MEC>1Ru-4Ni/MEC>Ni/MEC，将实施例5和实施例14-17中的新鲜催化剂的孔隙结构进行表征，其结果如表2所示：
表2
催化剂 比表面积(m 2/g) 孔隙体积(cm 3/g) 平均孔隙大小(nm)
MEC 1321.95 1.71 5.17
Ru/MEC 1211.57 1.42 4.7
4Ru-1Ni/MEC 1301.93 1.67 5.12
1Ru-1Ni/MEC 1288.99 1.63 5.07
1Ru-4Ni/MEC 1206.17 1.54 5.09
Ni/MEC 1203.87 1.58 5.23
实施例5和实施例15-19中的合成的新鲜催化剂的氮气吸附-脱附等温线如图6所示，图6中横坐标表示相对压力P/P 0,P 0表示气体在吸附温度时的饱和蒸汽压,P表示吸附平衡时气相的压力，纵坐标表示标准状态下测得的吸附量(单位：cm 3/g)；新鲜催化剂的孔径分布如图7所示，图7中横坐标表示孔径(单位：nm)，纵坐标表示孔容(cm 3/g)。由图6和图7可得，所有催化剂均为IV型等温线，孔径分布较窄，中心位于5nm左右，这是由于这些催化剂具有发达的介孔结构，这些催化剂具有1000-1400m 2/g的比表面积，与介孔碳相比，所有介孔碳负载的金属基催化剂的比表面积和孔容都更低，这是由于介孔碳孔隙中金属颗粒的引入，导致比表面积和空隙体积的减小；与Ru/MEC相比，4Ru-1Ni/MEC的比表面积和孔容更高，而1Ru-1Ni/MEC和1Ru-4Ni/MEC的比表面积和孔容更低。这些结果表明，少量第二金属的加入改善了单金属催化剂的织构性能。
不同摩尔比例的的Ni/MEC、Ru/MEC和双金属催化剂的XRD谱图如图8所示。对于Ni/MEC，在44.5°和51.5°有较大的峰，分别对应Ni(111)面和(200)面。Ru/MEC和Ru基双金属催化剂的XRD谱图中分别在38.5°和42.3°处有两个弱峰，分别代表Ru物种的100和002晶面。Ru/MEC和Ru-Ni双金属催化剂中金属Ru的弱衍射峰表明，Ru纳米粒子体积小且高度分散在MEC表面[38,45,49,50]，这与电镜扫描结果一致， 小的纳米颗粒可以提供更多的表面原子，从而提高其催化活性。
根据实施例5、实施例17和实施例20-25得出，介孔碳负载的Ru-Ni双金属催化剂在本发明的运行条件下表现出比Ru单金属更高的稳定性。
单金属和双金属碳负载催化剂的TEM图像和金属粒径分布如图9所示，图9中a为Ni/MEC的TEM和粒径分布图像,b为Ru/MEC的TEM和粒径分布图像，c为4Ru-1Ni/MEC的TEM和粒径分布图像，Ru-Ni的平均粒径为14.1nm，大于单金属Ru/MEC(平均粒径为7.2nm)。这种现象可能是由于Ru和Ni的协同作用。经观察，Ru和Ni原子几乎在同一位置，整个成像区域内每个原子没有分离，表明形成了均匀的Ru-Ni合金结构。
进一步研究氧化预处理反应的操作参数对第一段氧化预处理和第二段重整反应性能的影响实验结果如表3：
表3
Figure PCTCN2021098607-appb-000003
由表3得，在较低的水热温度下聚烯烃的氧化反应减弱，在220℃以上的水热环境中，有机物可能发生脱羧反应，即长链羧酸的热裂解，预氧化反应时间过长会对重整反应产生不利影响。当氧化预处理的 时间为60min，温度为200℃时，乙酸产量最高，对后续的重整反应进行最有利。
新鲜双金属4Ru-1Ni/MEC催化剂与单金属Ru催化剂的制氢催化活性最相似，因此选择4Ru-1Ni/MEC和Ru/MEC催化剂进行稳定性测试和比较。每次使用后，催化剂被回收并在105℃的烘箱中干燥一夜。与第一次运行相比，第二次运行的H 2产率和H 2摩尔分数明显下降，第三次和第四次运行变化平稳。催化剂性能的下降是由于积炭和活性金属烧结导致催化剂失活。
实施例20-25结果表明，4Ru-1Ni/MEC和Ru/MEC催化剂在使用后比表面积都降低了，虽然两种催化剂的平均孔径在使用后有所减小，但催化剂的孔径分布仍较窄，中心位置在5nm左右。此外，在介孔碳负载Ru-Ni双金属催化剂的XRD谱图中没有观察到NiO峰，这可能是由于金属Ru对Ni的氧化有抑制作用。与第二次运行相比，第三次和第四次运行的产氢量变化不大，但H 2摩尔分数呈不断降低的趋势。介孔碳负载Ru-Ni双金属催化剂重整反应工艺的H 2产率和H 2摩尔分数均高于介孔碳负载Ru单金属催化剂。这说明由于两种金属之间的相互作用，Ru-Ni双金属催化剂比单金属Ru催化剂具有更高的稳定性。
上述实施例是对本发明的说明，不是对本发明的限定，任何对本发明简单变换后的方案均属于本发明的保护范围。

Claims (10)

  1. 一种低温降解聚烯烃废塑料制备富氢合成气的方法，其特征在于，包括如下步骤：
    (1)称取聚烯烃塑料1重量份，双氧水3重量份以上，所述双氧水含有H 2O 2的浓度为0.25％-6％；
    (2)将称取的聚烯烃塑料和双氧水装填至水热反应器，进行氧化预处理反应，反应温度为150-230℃，反应结束后得到液相产物和气相产物；
    (3)在另一个水热反应器中装填介孔碳负载的金属基催化剂，再将步骤(2)得到的液相产物通入水热反应器中，进行重整反应，得到富氢合成气产物。
  2. 如权利要求1所述的低温降解聚烯烃废塑料制备富氢合成气的方法，其特征在于：所述步骤(1)中的双氧水中的H 2O 2的含量为0.5-2％。
  3. 如权利要求1所述的低温降解聚烯烃废塑料制备富氢合成气的方法，其特征在于：所述步骤(1)中的双氧水的重量份为3-80重量份。
  4. 如权利要求3所述的低温降解聚烯烃废塑料制备富氢合成气的方法，其特征在于：所述步骤(1)中双氧水的重量份为5-10份，步骤(2)中反应压力为0.5-2MPa，反应时间30-90min。
  5. 如权利要求4所述的低温降解聚烯烃废塑料制备富氢合成气的方法，其特征在于：所述步骤(2)中，反应温度为190-200℃，反应压力为1MPa，反应时间为30-60min。
  6. 如权利要求1所述的低温降解聚烯烃废塑料制备富氢合成气的方法，其特征在于：所述步骤(2)中得到的液相产物的主要成分是乙酸，气相产物是氧气和二氧化碳。
  7. 如权利要求1所述的低温降解聚烯烃废塑料制备富氢合成气的方法，其特征在于：所述步骤(3)中重整反应的反应温度为200-240℃，反应压力为2-4MPa，反应时间为120-180min。
  8. 如权利要求1所述的低温降解聚烯烃废塑料制备富氢合成气的方法，其特征在于：所述步骤(3)中的介孔碳负载的金属基催化剂为介孔碳负载的Ru单金属、介孔碳负载的Ni单金属、介孔碳负载Pt单金属和介孔碳负载Ru-Ni双金属中的一种或多种。
  9. 如权利要求8所述的低温降解聚烯烃废塑料制备富氢合成气的方法，其特征在于：所述步骤(3)中的介孔碳负载的金属基催化剂为介孔碳负载的Ru-Ni双金属催化剂，Ru和Ni的负载质量比为4:1、1:1或1:4。
  10. 如权利要求1所述的低温降解聚烯烃废塑料制备富氢合成气的方法，其特征在于：所述聚烯烃塑料选自聚丙烯、低密度聚乙烯和高密度聚乙烯的一种或多种。
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