Aromatics and phenols from catalytic pyrolysis of Douglas fir pellets in microwave with ZSM-5 as a catalyst

Microwave assisted catalytic pyrolysis was investigated to convert Douglas fir pellets to bio-oils by a ZSM-5 zeolite catalyst. A central composite experimental design (CCD) was used to optimize the catalytic pyrolysis process. The effects of reaction time, temperature and catalyst to biomass ratio on the bio-oil, syngas, and biochar yields were determined. GC/MS analysis results showed that the bio-oil contained a series of important and useful chemical compounds. Phenols, guaiacols, and aromatic hydrocarbons were the most abundant compounds which were about 50–82% in bio-oil depending on the pyrolysis conditions. Comparison between the bio-oils from microwave pyrolysis with and without catalyst showed that the catalyst increased the content of aromatic hydrocarbons and phenols. A reaction pathway was proposed for microwave assisted catalyst pyrolysis of Douglas fir pellets.

► Phenols, guaiacols, and aromatic hydrocarbons were enriched and about 50–82% in upgraded bio-oils. ► The effects of reaction time, temperature and catalyst to biomass ratio on products yields were determined. ► The volatile and syngas yields by ZSM-5 catalyst were much higher than those without using catalyst. ► A reaction pathway was proposed for microwave assisted catalytic pyrolysis of Douglas fir pellets.