Catalytic hydroprocessing of microalgae-derived biofuels: a review

The algal biofuel technology has been accelerated greatly during the last decade. Microalgae can be processed into a broad spectrum of biofuel precursors, which mainly include crude algal oil recovered by extraction and bio-crude oils produced from hydrothermal liquefaction and pyrolysis processes. Due to the high protein content in algal species and the limitations of conversion technologies, these biofuel precursors require the further catalytic removal of heteroatoms such as oxygen, nitrogen, and sulfur, being upgraded to biofuels like green diesel and aviation fuel. This article reviews the state-of-the-art in the hydroprocessing of microalgae-based biofuels, as well as the catalyst development and the effect of process parameters on hydrotreated algal fuels. Hydroprocessing of algal fuels is a new and challenging task, and still underdeveloped. For the long term, an ideal catalyst for this process should possess the following characteristics: high activities towards deoxygenation and denitrogenation, strong resistance to poisons, minimized leaching problems and coke formation, and an economically sound preparation process.