Stability and storage properties of hydrocarbons obtained by pilot scale pyrolysis of real waste HDPE-PVC in tubular reactor

Abstract

In this work the mixtures of real waste high-density polyethylene, low-density polyethylene, polypropylene and polyvinyl-chloride (PVC) were pyrolyzed in a pilot scale horizontal tubular reactor using different synthetic zeolite catalysts. Raw material was fed into the reactor through an electrically heated screw feeder, and then decomposed in the reactor. Products were separated into gases, pyrolysis oil and heavy fraction by atmospheric distillation. The yields of gases and pyrolysis oils can be significantly increased by using catalysts, but the catalyst properties were key parameter. For instance, Ni/ZSM-5 catalyst can increase the hydrogen content in gases and isomerize the carbon framework of hydrocarbons. Pyrolysis oils contained C5-C35 hydrocarbons; however their properties were modified by catalysts. An accelerated aging test was performed to follow the long term behavior of products. Pyrolysis oils were treated at 80 °C for 7 d, and then the stability of pyrolysis oils was assessed by evaluating the density, solid deposition and acid number. Unsaturated hydrocarbons in pyrolysis oils can agglomerate during the aging. On the other hand the catalysts can improve their properties. Pyrolysis oils obtained by thermo-catalytic pyrolysis resulted with less corrosion than in case of without catalysts.