Biofuel production from catalytic microwave pyrolysis of Douglas fir pellets over ferrum-modified activated carbon catalyst

• First effort using ferrum-modified activated carbon catalyst for bio-oil upgrading.
• Achieved high selectivity of ketones/ethers and phenols by catalytic upgrading.
• Achieved complete organic acids removal in bio-oils.
• Presented the reaction mechanism of the upgrading process.

The presented study aims to improve the quality of bio-oils by catalytic upgrading of bio-oil from microwave pyrolysis of Douglas fir pellet using transition metal modified activated carbon (AC) catalyst. A central composite experimental design (CCD) was used to optimize the reaction conditions for high quality bio-oil production. The effects of reaction temperature and reaction time on product yields were investigated. GC/MS analysis indicated that the main chemical compounds (including furans, phenols, guaiacols, and ketones/ethers) of bio-oils were in the range of 80–87% of bio-oils for most of the samples. The ketones/ethers were mainly composed of 2-cyclopen-1-one; straight chain ethers were increased up to about 38% of bio-oil; and the phenols increased from 2.5% to about 10% of the bio-oils after upgrading accompanying with the decrease of guaiacols in comparison with raw biomass pyrolysis. The reaction mechanism of this process was analyzed.