Advances in upgrading biomass to biofuels and oxygenated fuel additives using metal oxide catalysts

Increasing demand for transportation fuels, awareness of climate change, and dwindling supplies of crude oil has led to the rapid increase in production of biomass derived oxygenated fuel additives as viable drop-in fuels for potential blending with conventional fuels. The biorefinery processes for synthesis of oxygenated fuel additives using metal oxide catalysts in various forms have evolved significantly. Metal oxides exhibit diverse structures and physiochemical properties including acidity, basicity, and redox nature along with the lattice oxygen vacancies, which by careful design and modification can be tuned to optimize high catalytic activity and selectivity in several organic transformations. Metal oxide based catalysts can be designed for use in industries, as individual metal oxides or mixed metal oxides, decorated with noble and non-noble metal nanoparticles, porous metal oxides, and sulfonated metal oxides. In this review, we have attempted to consolidate the progress made with catalytic applications of metal oxides in the synthesis and production of oxygenated fuel additives through several important biorefinery processes.