What Is The Product Of The Decomposition Of Plastic Wrap?
Aug 07, 2022
Recycling of paraffin and olefins in fresh-keeping bags: Many fresh-keeping bags can produce paraffin or olefin hydrocarbon gases after high temperature decomposition, and the amount produced varies greatly depending on the type of plastic. A large amount of this gas is produced in the thermal decomposition of plastics such as polyethylene and polystyrene, and with the increase of the reaction temperature, the gaseous products increase and the liquid products decrease.
The plastic bag decomposes the oil. Low-density polyethylene is thermally decomposed at 4200C for 2h, and the resulting product contains 60% paraffin and 40% olefin. If high-density polyethylene is continuously introduced into the reaction system with a melter, and thermally decomposed at 400-4500C, 94.5% of the decomposed oil and 5.5% of the decomposed gas can be obtained. The order of recovery is: propylene>ethylene, propane>methane>n-butane.
In order to improve the yield of decomposed oil, an autoclave can be used to thermally decompose polyethylene in an atmosphere of carbon dioxide, carbon monoxide, helium and hydrogen. The addition of water to control local overheating during decomposition can also increase the rate of oiling. Using lacquer nickel or Pt-C as a catalyst to hydrogenate and decompose polyethylene, the oilification rate is as high as 85% to 90%.
The polypropylene of the fresh-keeping bag is thermally decomposed at about 4000C, and the recovered decomposed oil is as high as 95%. If zinc chloride is used as a catalyst, and polypropylene is hydrogenated and decomposed in an autoclave, 64% of the decomposed oil with an octane number of 83 can be obtained. The quality of this oil can be used as gasoline; if water is added for hydrolysis, a decomposed oil with an octane number of 86 can be obtained, but the olefin content is 40%. Methane is the most decomposed gas, followed by ethane and propane.
The fresh-keeping bag decomposes the gas. Thermal decomposition gasification is mostly used to recover olefin gas, ethylene can be recovered from polyethylene, and propylene can be recovered mainly from polypropylene.
The fresh-keeping bag uses a melting furnace to continuously introduce polyethylene into the reaction system, and thermally decomposes it at 590-8000C. The gasification rate is 75%. At about 7000C, 32% ethylene can be obtained, plus propylene and butene-l, etc. A total of 58%. If a molten salt thermal decomposition furnace is used and the decomposition temperature is raised to 850 °C, ethylene can be obtained by 30%, propylene can be obtained by 17%, and olefin can be obtained by 60% in total; times. At 4800C, the order of catalyst activity to gasification rate is (from large to small). SiO2·AL2O3, CaX, NaX, NaY, CaA, NaA.
The polypropylene of the fresh-keeping bag is decomposed at 500-6000C, and the gasification rate increases with the increase of the reaction temperature. At 6000C, 26% of propylene can be obtained, followed by ethylene and methane. When the molten salt thermal decomposition furnace is used, the decomposition temperature reaches about 9000C, from which 20% of ethylene, 20% of methane and only 10% of propylene can be obtained. Similarly, polypropylene can be catalytically decomposed with solid acidic catalysts, that is, silica and alumina are used as catalysts, and a fluidized bed atmospheric reaction device is used to produce methane at 4500C, followed by propylene and ethane. The production of liquid paraffin is more than that without catalyst.
