Catalytic degradation of oxygenates in Fischer-Tropsch aqueous phase effluents to fuel gas via hydrodeoxygenation over Ru/AC catalyst

BACKGROUND: Aqueous phase FischerTropsch (FT) effluents co-produced with hydrocarbons in the FT process contain various water-soluble oxygenates, e.g. carboxylic acids, alcohols. Purification of the FT aqueous phase is important from the viewpoint of effective resource utilization and environmental stewardship. In this work, an aqueous-phase hydrodeoxygenation process was investigated for the degradation of FT aqueous phases. RESULTS: The Ru/AC catalyst was determined to be the most active catalyst. The key parameters, i.e. temperature, pressure, weight hourly space velocity and Ru loading, were comprehensively optimized. Under optimal conditions, ca 98% of the oxygenates were converted to C-1 similar to C-6 alkanes. The degraded water had no odour, a neutral pH, and as low as 1000 mg L-1 chemical oxygen demand. The Ru/AC catalyst exhibited long-term stability ( 1300 h) and no ruthenium leaching. A reaction pathway is proposed for this process in which the carboxylic acids are hydrogenated to alcohols via the formation of aldehydes. Alcohols and aldehydes are then converted to methane and alkanes of one carbon atom less than the substrate through C-C bond cleavage. CONCLUSIONS: This process is effective for treating FT aqueous phase effluent, and holds great promise for industrial applications due to its high efficiency, simplicity and stability. (C) 2011 Society of Chemical Industry