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In the last 20 years, it has become apparent that waste produced from plastics was becoming an envi- ronmental problem because of their low biodegradability. Though several methods have been proposed for recycling waste plastics, it is generally accepted that material recovery is not a long-term solution to the present problem, and that energy or chemical recovery is a more attractive alternative, including cracking into the monomer constituents, combus- tion to produce energy, and thermal or catalytic conversion to produce useful intermediate chemicals. This paper is a contribution in the area of the last option for energy recovery. There have been a number of publications reporting the use of molecular sieves and amorphous silica-alumina catalysts for the cracking of polymers into a range of hydrocarbons. The research work reported here demonstrates the ability of mesoporous catalysts in cracking polyethyl- ene into gasoline range products. It was found that for mesoporous MCM-41 catalysts, its cracking activity increases with its crystallinity, displaying higher activity with smaller pore diameters. The hydrocarbon product distribution strongly indicates a carbenium ion cracking mechanism. The product distribution was also compared with those obtained from thermal cracking tests.
In the last 20 years, it has become apparent that waste produced from plastics was becoming an envi- ronmental problem because of their low biodegradability. Though several methods have been proposed for recycling waste plastics, it is generally accepted that material recovery is not a long -term solution to the present problem, and that energy or chemical recovery is a more attractive alternative, including cracking into the monomer constituents, combus- tion to produce energy, and thermal or catalytic conversion to produce useful intermediate chemicals. This paper is a contribution in the area of the last option for energy recovery. There have been a number of publications reporting the use of molecular sieves and amorphous silica-alumina catalysts for the cracking of polymers into a range of hydrocarbons. mesoporous catalysts in cracking polyethyl- ene into gasoline range products. It was found that for mesoporous MCM-41 cat alysts, its cracking activity increases with its crystallinity, displaying higher activity with smaller pore diameters. The product distribution was also compared with those obtained from thermal cracking tests.