Acid catalysts polyolefin cracking

D. P. Serrano, J. Aguado, and J. M. Escola, Catalytic Cracking of a Polyolefin Mixture over Different Acid Solid Catalysts, Ind. Eng. Chem. Res., 39, 1177-1184... 

Figure 3.4 Mechanism of catalytic cracking of polyolefins over acid solid catalysts [28]. (Reproduced by permission of the American Chemical Society)...

D. Serrano, J. Agudo and J. Escola. Catalytic cracking of a polyolefin mixture over different acid solid catalysts. Industrial and Engineering Chemistry Research, 39, 1177-1184 (2000). 

The acid cracking catalysts produce carbonium ions by the addition of protons to polyolefin chains or by abstraction of hydride ions from hydrocarbon molecules. This is followed by chain scission, which yields C30-C50 oligomeric hydrocarbons. Secondary cracking by P-scission of the C30-C50 hydrocarbons yields liquid (C10-C25) hydrocarbon fuel. Specific advantages of the Polymer-Engineering Process include ... 

Various kinds of Zeolites are engaged in the catalytic cracking of hydrocarbon feedstocks, such as ZSM-5, Beta, Y, in addition to other known acid solids such as silica-alumina, alumina and clays. Various combinations of these catalysts such as SAHAyZSM-5 and MCM-41/ZSM-5 have been also employed for the recycling of polyolefins [30]. 

Catalysts play an important role in the synthesis of fuels and chemicals as well as on the reaction systems hence, the catalytic cracking of polyolefins over solid acids needs to be explored. In this method a suitable catalyst is used to carry out the cracking reaction. The addition of a catalyst enhances the conversion and fuel quality, and lowers the reaction temperature and time. Reuse of catalysts and the use of effective catalysts in lesser quantities can optimise this option. It also enables an increased level of the cracking of plastics and a lower concentration of solid residue in the product. The cost should be further reduced to make the process more attractive from an economic perspective in order to solve the acute environmental problem of plastic waste disposal [2]. 

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