Overview on catalytic deoxygenation for biofuel synthesis using metal oxide supported catalysts

Catalytic deoxygenation is a biofuel upgrading process to eliminate the high oxygen content which will lead to corrosion, instability and lower heating value problems. Biofuel have a high oxygen content, which deteriorates the biofuel quality. Therefore, the upgrading of biofuels via catalytic deoxygenation is necessary. Metal oxide such as TiO₂, Al₂O₃, SiO₂, ZrO₂ and CeO₂ is known as a promising support for the production of hydrocarbon-graded biofuel via deoxygenation process. The choice of support is significant to provide the maximum acid strength for the hydrogenolysis of C-O bonds. Al₂O₃ supported catalyst has drawn attention due to the high acidity. However, the high acidity leads to coke deposition, unstable and deactivation of the catalyst. Thus, it is important to develop methods to reduce catalyst coking and enhance the lifetime of the catalyst. Recently, Al₂O₃-TiO₂ supported catalyst has drawn increasing attention in deoxygenation process owing to its unique properties which can solve the issues from Al₂O₃. Controlled synthesis method is significant to improve the effectiveness of Al₂O₃-TiO₂ in catalytic reaction since the physicochemical properties of the catalyst are co-related to the processing methodology. Hence, this review describes the use of selected metal oxide supported catalyst for biofuel conversion in deoxygenation process. Moreover, the synthesis method of Al₂O₃-TiO₂ is comprehensively discussed. The physicochemical properties of Al₂O₃-TiO₂, metals and metal oxides supported on Al₂O₃-TiO₂ are further discussed. Finally, future prospective and challenges of deoxygenation process for biofuel synthesis are discussed in order to produce quality hydrocarbon like biofuel using metal oxide supported catalyst.