Production high yields of aromatic hydrocarbons through catalytic fast pyrolysis of torrefied wood and polystyrene

• Pyrolysis of torrefied wood and polystyrene was used to produce aromatic hydrocarbons.
• Presence of polystyrene introduced more than twenty aromatic hydrocarbon compounds.
• Higher temperatures (600 °C) and zeolite catalyst improved the yield of aromatic hydrocarbons.
• Aromatic hydrocarbons were formed through a free radical reaction mechanism.

Catalytic fast pyrolysis of torrefied wood has been shown to improve the yields of aromatic hydrocarbons in the bio-oil. In this study, Py-GC/MS was employed on torrefied wood (TW), polystyrene (PS) and torrefied wood/polystyrene (TW/PS) with and without zeolite catalyst (HZSM-5) to produce a wide range of aromatic hydrocarbons. The effects of pyrolysis temperature, presence of polystyrene and catalyst on the yields and nature of aromatic hydrocarbons were investigated. Experimental results showed that the chemical composition of TW pyrolysis products was significantly different than that produced from TW/PS and TW/PS/catalyst. Presence of PS significantly reduced the yield of oxygenated phenolic compounds and produced more aromatic hydrocarbons compared to TW. More than twenty aromatic hydrocarbons were introduced during the co-pyrolysis of TW/PS and TW/PS/catalyst due to the presence of PS. The highest yields of aromatic hydrocarbons in co-pyrolysis samples were obtained at 600 °C, but higher temperatures slightly decreased the yield of most hydrocarbons. The major aromatic hydrocarbons were found to have high influence on the yields of pyrolysis products are: Styrene; α-methylstyrene; 2-phenyl-1,2,3,4-tetrahydronaphthalene; diphenylpropane and diphenylbutane derivatives. Most of aromatic hydrocarbons identified in this study were proposed to be formed through free radical reaction mechanism.