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CN-121988350-A - Method for catalyzing polypropylene hydrogenation degradation by molybdenum sulfide

CN121988350ACN 121988350 ACN121988350 ACN 121988350ACN-121988350-A

Abstract

The catalyst synthesized by the method reaches the level of 50nm, has high dispersivity, can convert polypropylene waste plastics into oil products with distillation ranges from 20 ℃ to 500 ℃, has the oil product yield reaching 90 percent, has the conversion rate reaching 100 percent, and has the selectivity of 95 percent for gasoline and diesel components.

Inventors

  • MA HUAIJUN
  • Gong shuxin
  • SONG HUAN
  • TIAN ZHIJIAN
  • QU WEI
  • HAN JIANQIANG
  • CHEN XIN
  • QIU WENLONG

Assignees

  • 中国科学院大连化学物理研究所

Dates

Publication Date
20260508
Application Date
20241105

Claims (10)

  1. 1. A method for catalyzing the hydrogenation degradation of polypropylene by molybdenum sulfide, which is characterized by comprising the following steps: (1) Synthesizing a molybdenum sulfide catalyst: (1.1) adding a molybdenum precursor, an aqueous solution of L-cysteine or L-cysteine and water into a hydrothermal kettle; (1.2) the hydrothermal kettle is subjected to constant temperature reaction for 4-24 hours (preferably 6-16 hours, more preferably 8-12 hours) at a specified temperature, and naturally cooled to room temperature; (1.3) taking out the materials in the hydrothermal kettle, carrying out solid-liquid separation, and drying the solid to obtain a molybdenum sulfide catalyst; (2) Hydrogenation of polypropylene waste plastics using a molybdenum sulphide catalyst: (2.1) adding polyolefin waste plastics into a high-pressure reaction kettle; (2.2) weighing a molybdenum sulfide catalyst, and adding the molybdenum sulfide catalyst into a high-pressure reaction kettle; (2.3) replacing the internal atmosphere of the reaction kettle with hydrogen, and then filling hydrogen; (2.4) heating the reaction kettle to a specified temperature, stirring at a constant temperature for reaction, and naturally cooling to room temperature (20-30 ℃) to obtain the product.
  2. 2. The method according to claim 1, wherein the molar ratio of molybdenum to sulfur in the molybdenum precursor and L-cysteine of step (1.1) is 1:2-6, preferably 1:4-6, more preferably 1:5-6.
  3. 3. The method according to claim 1 or 2, wherein the molybdenum precursor in step (1.1) comprises one or more of ammonium paramolybdate tetrahydrate, molybdenum trioxide and phosphomolybdic acid, and the mass ratio of L-cysteine to water is 1:12-15, preferably 1:13-15, more preferably 1:14-15.
  4. 4. The method according to claim 1, wherein the specified temperature in step (1.2) is between 160-200 ℃, preferably 160-180 ℃, more preferably 170-180 ℃.
  5. 5. The process according to claim 1, wherein the reactor charge in step (2.1) is defined as 20-30g waste plastic per 100ml reactor volume, and the reactor catalyst concentration in step (2.2) is 1000-10000ppm, preferably 3000-10000ppm, more preferably 8000-10000ppm.
  6. 6. The method according to claim 1, wherein the amount of hydrogen gas in step (2.3) is at a pressure of between 2 and 10MPa, preferably 8 to 10MPa, more preferably 9 to 10MPa.
  7. 7. The method according to claim 1, characterized in that the specified temperature in step (2.4) is between 390-420 ℃, preferably 390-400 ℃.
  8. 8. The method according to claim 1, wherein the specified time in step (2.4) is between 0.5 and 4 hours, preferably 1 to 4 hours, more preferably 2 to 3 hours.
  9. 9. The method according to claim 1, wherein after the reaction kettle is heated to a specified temperature at a temperature rising rate of 5-10 ℃ per minute, stirring and reacting for a certain time at constant temperature, and naturally cooling to room temperature (below 20-30 ℃); The high-pressure reaction kettle is a slurry bed reactor.
  10. 10. The method according to claim 1, wherein the stirring rate in step (2.4) is 100 to 160rpm at 200 ℃ and below, and 300 to 400rpm at 200 ℃ and above.

Description

Method for catalyzing polypropylene hydrogenation degradation by molybdenum sulfide Technical Field The invention belongs to the technical field of catalyst synthesis, and particularly relates to a preparation method of a molybdenum sulfide catalyst used for degrading waste plastics in a slurry bed. Background In 2022, china produces 6000 ten thousand tons of waste plastics, most of which are disposed of in an incineration or landfill mode, and only 1800 ten thousand tons of waste plastics are recovered. In order to make efficient use of hydrocarbon resources in waste plastics, chemical recovery is becoming the recovery method of most application prospect and potential for industrial scale. The main chemical composition and chemical nature of waste plastics are close to those of heavy oil, so it is feasible to use slurry beds as recycling treatment devices. However, the waste plastics have high decomposition temperature and complex components, and the waste plastics are easy to poison and coke when treated by using the noble metal hydrogenation catalyst, so that the slurry bed hydrogenation catalyst with high dispersibility and toxicity resistance and coking resistance needs to be prepared. Disclosure of Invention The invention aims to provide a preparation method of one or more molybdenum sulfide catalysts for the hydrogenation degradation of polyolefin waste plastics on a slurry bed. The catalyst synthesized by the invention reaches the level of 50nm, has high dispersibility, can convert the polypropylene waste plastics into oil products with the distillation range of 20-500 ℃, has the oil product yield of 90 percent, has the conversion rate of 100 percent, and has the selectivity of 95 percent for gasoline and diesel components. The invention provides a preparation method of a molybdenum sulfide catalyst for the hydrogenation degradation of a polypropylene waste plastic slurry state bed, which comprises the following steps: (1) Preparation of molybdenum sulfide catalyst: (1.1) weighing L-cysteine with a certain molybdenum/sulfur molar ratio by taking 3mmol of molybdenum precursor as a standard, putting the L-cysteine into a 100ml beaker, adding 25g of water, stirring for 10min, and transferring the mixture into a 100ml stainless steel water heating kettle with a polytetrafluoroethylene lining; (1.2) weighing 3mmol of molybdenum precursor, putting into a hydrothermal kettle, and screwing a cover of the hydrothermal kettle by using a wrench; (1.3) putting the hydrothermal kettle into an oven with a specified temperature, and taking out after 8 hours; (1.4) after the hydrothermal kettle is opened, the mixture is filtered under reduced pressure through a buchner funnel; (1.5) washing the solid materials on the Buchner funnel three times with water and absolute ethyl alcohol, filtering again under reduced pressure, and pumping out the liquid in the solid materials; (1.6) taking out the solid on the Buchner funnel, transferring the solid to a 9cm culture dish, drying the solid in a vacuum drying oven at 70 ℃ for 12 hours, and taking out the solid to obtain the molybdenum sulfide catalyst; (2) The catalyst prepared by the method is applied to the hydrogenation degradation of polypropylene on a slurry bed: (2.1) weighing 20-30g of 1mm polypropylene particles with the average molecular weight of 44000Da, and adding the polypropylene particles into a 100ml Parr high-pressure reaction kettle; (2.2) weighing 0.03-0.1g of the molybdenum sulfide catalyst prepared above, and adding the molybdenum sulfide catalyst into a 100ml Parr high-pressure reaction kettle; (2.3) after the reaction kettle is assembled, replacing 3 times by 1-1.5MPa of hydrogen, and then filling hydrogen with certain pressure; (2.4) heating the reaction kettle to 200 ℃ at a heating rate of 10 ℃ per minute for 15 minutes, heating to a certain temperature, stirring at a constant temperature for reacting for a certain time, and naturally cooling to room temperature (below 30 ℃); (2.5) collecting the tail gas by using an air bag, taking out the mixture in the reaction kettle, sampling, filtering by using a Buchner funnel under reduced pressure, washing the solid by using ethanol for three times, naturally airing and weighing. The indication that the molybdenum/sulfur ratio in (1.1) may be 1:2-6; the indication that the molybdenum precursor in (1.2) may be phosphomolybdic acid, molybdenum trioxide and ammonium paramolybdate; The designation temperature in (1.3) is 160-200 ℃; The point out that (1.3) the oven needs to be warmed to the specified temperature in advance; the teaching is that (1.4) buchner funnel filtration uses qualitative filter paper; The molybdenum sulfide catalyst is obtained after drying (1.6), and is required to be ground into powder by a mortar for use; The hydrogen pressure in (2.3) was from 4MPa to 10MPa; the reaction temperature in (2.4) was in the range of 390-420 ℃; The stirring rate in (2.4) was 100rpm at 200℃or less and 300rpm