Catalytic modification of pyrolysis products of nitrogen-containing polymers over Y zeolites

Abstract

Pyrolysis products of nitrogen-containing polymers have been transformed at 500 °C over NaY and ultra stable HY (HUSY) zeolite on-line and analysed by gas chromatography/mass spectrometry. HUSY was found to be an effective catalyst converting nitrogen-containing compounds into a series of well-defined aromatic hydrocarbons. Almost all nitrogen-content of the pyrolysis oils including amines, amides and nitriles have been successfully eliminated over HUSY; only traces of aliphatic nitriles in the range of 3–8 carbon atoms still remained in some of the pyrolysis oils. The uniform composition of the converted pyrolysis oil offers the possibility to gain pure aromatic feedstock from plastics waste. NaY proved to be an effective catalyst for cracking the heavy oil components of polymer pyrolysates to gases and to compounds of gasoline volatility, nevertheless it was not active for denitrogenation. Thermal treatment of deactivated zeolite has been carried out to study catalysts regeneration. By means of regeneration at 500 °C in air flow for 8 hours the activity of NaY has been completely recovered, while in the case of HUSY a slight decrease of activity was observed after the same treatment.