Pyrolysis is a process which involves thermochemical decomposition of organic matter at high temperature (>370◦C) in the absence of oxygen. Products of this process are Pyrolysis Oil, Carbon Black, and Hydrocarbons. This process can be thermal or catalytic and is an alternative that allows the conversion of polymers into gas and liquid hydrocarbons. The plastic waste is processed to produce petrochemical compound.

  • Thermal pyrolysis

The temperature of pyrolysis ranges from 350°C to 900°C.Thermal pyrolysis involves the decomposition of polymeric materials by means of temperature when it is applied under inert atmospheric conditions. This process is usually conducted at temperatures between 350 and 900 °C. In the case of polyolefins, which make up much of urban waste plastics, the process proceeds through random cleavage mechanism that generates a heterogeneous mixture of linear paraffins and olefins in a wide range of molar masses. Generally following products are derived.

  • Non condensable gases
  • Liquid fraction (paraffin, olefins, naphthenes, and
  • aromatics)
  • From liquid fraction following range products are obtained,
  • Gasoline range (C4-C12)
  • Diesel Range (C12-C23)
  • Kerosene Range (C10-C18)
  • Motor Oil Range (C23-C40)
  • Solid waste

Catalytic pyrolysis

The catalyzed pyrolysis promotes these decomposition reactions at lower temperatures and shorter times, because of the presence of catalysts that assist in the process. Thus, the catalytic pyrolysis presents a number of advantages over thermal, such as lower energy consumption and product formation with narrower distribution of the number of carbon atoms, which may be directed to aromatic hydrocarbons with light and high market value. The homogeneous catalysts used are Lewis acids, as AlCl3, fused metal tetrachloro-aluminatos (M (AlCl4) n), where the metal may be lithium, sodium, potassium, magnesium, calcium or barium and n can be 1 or 2). Heterogeneous catalysts used are conventional solids like zeolites, silica alumina, alumina and catalysts for fluid bed and fluidized bed Catalytic Cracking, mesostructured catalysts (such as MCM-41 etc.), and Nano crystalline zeolites (such as nHZSM-5)

Information collected by : Sanjay Kumar Lodh


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