Thermal-catalytic destruction of polyolephin polymers in presence of LnVO₃ and LnVO₄

This paper describes non-catalytic and catalytic pyrolysis of plastic waste materials. Four types of waste plastics were used in study: high density polyethylene (PE), low density polypropylene (PP), polyethylene terephthalate (PET). Plastic waste was decomposed into three fractions under pyrolysis conditions: gas, liquid and solid residual. The use of vanadates MeVO₄ and vanadites MeVO₃ of REM (Me=La, Gd, Lu) as catalysts let to change the yield of the gas fraction and change the composition of the gaseous pyrolysis products. Catalytic decomposition increased the amount of the gaseous products by 15–20 %, reduced the condensate, and changed their composition with regard to the non-catalytic process at the same pyrolysis temperature. The total number of reaction products was determined in each fraction. The quantitative analysis of the composition of the gas fraction was performed by gas-liquid chromatography. The study of non-catalytic pyrolysis of plastics and thermogravimetric analysis let to determine the most favorable temperature conditions for the implementation of the catalytic pyrolysis. The catalytic pyrolysis of plastics was carried out in order to obtain the maximum yield of valuable gaseous products. The synthesized vanadites and vanadates of REM were used as catalysts. When using catalysts based on lanthanum and gadolinium compounds, a regular change in the amount of gaseous substances was observed without significant changes in their composition. The use of lutetium vanadate and lutetium vanadite demonstrated a phenomenal result that is associated with the cardinal change of structure of degradation products of PET. The syngas was obtained instead of acetaldehyde. This result is related to the structure of the used catalyst.