Desulfurized and Hydrogenated Crude Sulfate Turpentine (HCST): A Biofuel Derived from a Waste of the Pulp and Paper Industries

This study investigates the potential of crude sulfate turpentine (CST), a waste product from the pulp and paper industries, as a source for the production of sustainable biofuels. Direct use of CST as a drop-in biofuel is hindered by its high sulfur content and the presence of double bonds, leading to an increased level of soot formation during combustion. To address these challenges, CST, with a sulfur content of 10563 mg/kg, was desulfurized using peroxiformic acid oxidation, followed by liquid–liquid extraction, resulting in a sulfur content reduction to approximately 2000 mg/kg with a 70% yield. Subsequently, the desulfurized CST underwent repeated passes through an active carbon column, achieving a sulfur content of close to 10 mg/kg. The desulfurized CST was then hydrogenated using a 5% Pd/C catalyst in batch mode, attaining a 92% conversion rate after 4.5 h, with a sulfur content below 10 mg/kg. The hydrogenated CST samples were analyzed for various properties and compared to those of hydrogenated pine turpentine. The hydrogenated CST with 92% conversion exhibits good characteristics to work as a sustainable fuel but falls short in terms of derived cetane number and flash point. However, it could still be blended with JetA1 and diesel up to a maximum volume fraction of 65%. These findings suggest that CST has potential as a sustainable biofuel with further improvements needed to meet specific property requirements.