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CN-121990869-A - Method for preparing monocyclic aromatic hydrocarbon by polystyrene hydrogenation

CN121990869ACN 121990869 ACN121990869 ACN 121990869ACN-121990869-A

Abstract

The invention relates to the field of plastic degradation, in particular to a method for hydrogenating and degrading polystyrene. The method comprises the steps of adding a metal sulfide catalyst, a hydrogen-supplying solvent and polystyrene into a suspension bed reactor respectively, sealing the suspension bed reactor, and introducing gas with a certain pressure to start the reaction. The method for hydrogenolysis of polystyrene provided by the invention adopts a non-noble metal catalyst, and has more economical efficiency. The method provided by the invention adopts a solvent for hydrogen supply, adopts the coupling of hydrogenation aromatic hydrocarbon dehydrogenation and polystyrene hydrogenation, does not need to introduce hydrogen, has completely reversible hydrogenation-dehydrogenation of the hydrogenation aromatic hydrocarbon, and can be recycled. Low cost and better catalytic activity. Solves the problems that polystyrene is easy to produce hydrogen by self-cyclization and form polycyclic aromatic hydrocarbon, and simultaneously solves the problem that the pressure of hydrogen is high in the reaction process. Can realize complete hydrogenation liquefaction of waste polystyrene, has the yield of monocyclic aromatic hydrocarbon exceeding 90 percent, and has good economic benefit.

Inventors

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

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. The method for preparing the monocyclic aromatic hydrocarbon by hydrogenating the polystyrene is characterized by comprising the following steps of: under the action of a catalyst and a solvent, introducing inert gas with certain pressure to hydrogenolyze the polystyrene; The solvent is a hydrogen-supplying solvent; the catalyst is metal sulfide; The gas is inert gas or hydrogen.
  2. 2. The method for preparing monocyclic aromatic hydrocarbon by hydrogenating polystyrene according to claim 1, wherein the metal element in the metal sulfide catalyst is at least one or more than two of Fe, co, ni, mo and W; Preferably, the metal element in the metal sulfide catalyst is Mo.
  3. 3. The method for preparing monocyclic aromatic hydrocarbon by hydrogenating polystyrene according to claim 1, wherein the metal sulfide is a two-dimensional layered material, the length of the metal sulfide catalyst sheet (the length of the connecting line between the farthest two points of the sheet) is less than 1 micron, and the number of stacked layers is less than 50. The preferred metal sulfide platelet lengths are less than 100 nanometers, the number of stacked layers is less than 20, the more preferred metal sulfide platelet lengths are less than 10 nanometers, and the number of stacked layers is less than 10.
  4. 4. The method for preparing monocyclic aromatic hydrocarbon by hydrogenating polystyrene according to claim 1, characterized in that the mass ratio of the catalyst to polystyrene is 1:19 to 1:10000, preferably the mass ratio of the catalyst to polystyrene is 1:100 to 1:1000, more preferably the mass ratio of the catalyst to polystyrene is 1:250 to 1:500.
  5. 5. The method for preparing monocyclic aromatic hydrocarbon by hydrogenating polystyrene according to claim 1, wherein the hydrogen-donating solvent is at least one or more of hydrogenated aromatic hydrocarbon such as tetrahydronaphthalene, decalin, dihydroanthracene, dihydrophenanthrene, tetrahydroanthracene.
  6. 6. The method for preparing monocyclic aromatic hydrocarbon by hydrogenating polystyrene according to claim 1, characterized in that the mass ratio of the solvent to polystyrene is 100:1 to 1:5, preferably the mass ratio of the solvent to polystyrene is 100:1 to 1:1, more preferably the mass ratio of the solvent to polystyrene is 10:1 to 1:1.
  7. 7. The method for preparing monocyclic aromatic hydrocarbon by hydrogenating polystyrene according to claim 1, wherein the specific process is that a metal sulfide catalyst, a hydrogen-supplying solvent and polystyrene are respectively added into a suspension bed reactor, the suspension bed reactor is sealed, inert gas with certain pressure is introduced into the suspension bed reactor to start the reaction, and the reaction pressure is 0.1 to 20MPa, preferably 0.1 to 10MPa, more preferably 0.1 to 4MPa.
  8. 8. The method for preparing monocyclic aromatic hydrocarbon by hydrogenating polystyrene according to claim 1, wherein the inert gas is at least one or more of nitrogen (N 2 ), helium (He), neon (Ne) and argon (Ar).
  9. 9. The method for preparing monocyclic aromatic hydrocarbon by hydrogenating polystyrene according to any one of claims 1 to 8, wherein the hydrocracking of polystyrene is carried out at a temperature of 300 ℃ to 450 ℃, preferably at a temperature of 380 ℃ to 420 ℃, more preferably at a temperature of 400 ℃, and the hydrocracking of polystyrene is carried out for 0.5h to 12h, preferably for 2h to 12h, more preferably for 4h to 8h.
  10. 10. The method for preparing monocyclic aromatic hydrocarbon by hydrogenating polystyrene according to claim 9, wherein said polystyrene is waste polystyrene plastic.

Description

Method for preparing monocyclic aromatic hydrocarbon by polystyrene hydrogenation Technical Field The invention relates to the field of plastic degradation, in particular to a method for hydrogenating and degrading polystyrene. Background With the rapid development of society and economy, the demand for various plastic products such as polystyrene is rapidly increased, and a large amount of plastic wastes cause great pollution to the environment. In thermoplastics, the polystyrene yield is only after polyethylene, polypropylene, polyvinyl chloride, and is located at position 4. As can be seen from the related data, the 2023 global yield is about 2000 ten thousand tons, and the method is widely applied to the fields of electronic appliances, building materials, packaging materials, daily necessities and the like, but only less than 1% of polystyrene is recycled at present. Polystyrene is an olefin polymer containing a large amount of hydrocarbon elements, and can be used for producing fuel or as a raw material of chemicals after proper treatment. Therefore, research on recycling of waste polystyrene has profound significance for energy and environmental problems. The current treatment modes of the recycled waste polystyrene mainly comprise mechanical recovery, energy recovery and landfill treatment. The above disposal of waste polystyrene has great economic and environmental negative effects. In the developed route, the conventional pyrolysis and catalytic pyrolysis processes of polystyrene are simple, but catalyst carbon deposition is serious, and light gases and solid residues are generated. In addition, there are plasma-assisted fast hydrogenolysis of polystyrene, photocatalytic oxidation of polystyrene, and azide-assisted polystyrene cleavage routes which, although possible at lower temperatures, have low yields of high value oil products and poor practical availability. Polystyrene hydrogenolysis can be almost completely converted into aromatics and alkanes. At present, polystyrene hydrogenolysis is reported to be less. Patent 202311617793.7 discloses a route for the hydrogenolysis of polystyrene to monocyclic aromatic and monocyclic alkane under the action of a metal sulphide catalyst. However, this process requires a large amount of hydrogen gas at a reaction pressure of up to 10MPa. Patent 202310316107.6 discloses a route for cracking polystyrene into monocyclic aromatic hydrocarbon and monocyclic alkane under the action of supported ruthenium catalyst and methanol. The polystyrene hydrogenolysis mainly uses noble metals such as Pt, ru and the like as catalysts, and has excellent catalytic performance, but the noble metal catalysts are extremely easy to poison. The waste plastics contain a large amount of impurities and are extremely easy to poison noble metals. There is therefore an urgent need to develop a practical process for recycling waste polystyrene, with a focus on finding suitable hydrogenolysis catalysts and hydrogen-donating solvents, which can thoroughly upgrade waste polystyrene to valuable aromatics under severe conditions. Metal sulfides are two-dimensional layered materials that have been used in various processes such as catalytic hydrogenation, hydrodesulfurization, hydrodenitrogenation, hydrodeoxygenation, hydrocracking, hydrodemetallization, hydrodealkylation, hydro-ring opening, and the like in the coal chemical and oil refining industries. In addition to having strong dissolving, swelling and dispersing capabilities, the hydrogen donating solvent is more critical to have good hydrogen transfer and donating capabilities. From the structural point of view, the hydrogen-supplying solvent is rich in polycyclic aromatic hydrocarbon, especially hydrogenated aromatic hydrocarbon (such as tetrahydronaphthalene, dihydroanthracene, dihydrophenanthrene and tetrahydroanthracene) with strong hydrogen-supplying performance, and various solvents are widely applied in the hydrogenation degradation process of heavy carbon resources in coal chemical industry, oil refining industry and the like. At present, no report of producing light aromatic hydrocarbon by catalyzing polystyrene hydrogenation degradation by using a hydrogen supply solvent as a hydrogen source through a one-pot method exists. Disclosure of Invention The invention provides a method for producing light aromatic hydrocarbon by using hydrogen-supplying solvent as hydrogen source and catalyzing polystyrene hydrocracking by a one-pot method, which has low cost, improves aromatic hydrocarbon selectivity and has better economic benefit. Can effectively solve the problems of low solubility of H 2, heat transfer, slow mass transfer rate of polystyrene, coking, reactor bed blockage and catalyst deactivation. And the catalyst has low cost, improves the selectivity of monoaromatic hydrocarbon and has better economic benefit. The invention provides a method for preparing monocyclic aromatic hydrocarbon by polystyrene hydrogenation, which com