Aromatic hydrocarbons production from packed-bed catalysis coupled with microwave pyrolysis of Douglas fir sawdust pellets

Abstract

The direct catalytic cracking of biomass pyrolysis vapour into aromatics derived from Douglas fir sawdust pellets was tested using an upfront microwave pyrolysis process coupled with a packed-bed catalysis process using a ZSM-5 Zeolite catalyst. A central composite experimental design (CCD) was used to optimize the bio-oil and syngas yields. The effects of temperature and inverse weight hourly space velocity (WHSV)⁻¹ on the bio-oil composition were determined. The gas chromatography–mass spectrometry (GC-MS) analysis results showed that the bio-oil contained aromatic hydrocarbons. The aromatic hydrocarbons were enriched and became the most abundant compounds accounting for about 15–92.6% in upgraded bio-oils, depending on the catalytic pyrolysis conditions. The aromatic hydrocarbons were mainly composed of benzene, toluene, xylene, naphthalene, and their derivatives. When the effect of the reaction temperature on the bio-oil chemical compositions was analysed with a fixed (WHSV)⁻¹ (0.048 h), we found that the aromatic hydrocarbons increased from 0.72% in raw bio-oil (no catalyst added) to around 92.6% when the catalysis temperature was 500 °C, clearly demonstrating that a high temperature with the ZSM-5 Zeolite catalyst favoured the production of aromatic hydrocarbons. At a lower temperature fixed at 375 °C, the aromatic hydrocarbon content was increased from 0.72% to 78.1% with a (WHSV)⁻¹ increase from 0 to 0.075.