Simultaneous Catalytic Conversion of Acid-Pretreated Biomass into High-Quality Syngas and Bio-oil at Mild Temperature

An innovative method for the coproduction of high-quality bio-oil and syngas via the integration of in situ acid pretreatment on feedstock and ex situ reforming by activated carbon catalyst was investigated in this study. Dilute acid pretreatment of rice husk was performed in a 10 wt % H₃PO₄ solution between 60 and 140 °C. Then, the catalytic pyrolysis of raw and pretreated samples was conducted using activated carbon catalyst in a two-stage fixed-bed reactor at 500 °C for 15 min. The results indicated that the catalytic process transferred energy from liquid bio-oil to gas products. Water content took up most of the mass in bio-oil (>90 wt %), while the organic part was dominant by phenols and the gas product was a CO-rich syngas. Specifically, the optimal products from catalytic pyrolysis were achieved at a pretreatment temperature of 100 °C. Results of gas chromatography–mass spectrometry (GC–MS) revealed that the phenol occupied a 67.14% relative content of organics. Via quantification, the mass yield of phenol was 2.56 wt % of bio-oil, and this value was 2.02 times that of raw bio-oil and 1.41 times that of non-pretreated samples. The volume yield of CO in syngas was significantly increased to 163.59 mL/g with the CO fraction (63.23 vol %). Further, the mechanism of phenol and CO generation from pretreated samples is proposed and discussed, which provides new insight for the clean and high value-added utilization of biomass.