Evaluating strategies for catalytic upgrading of pyrolysis oil in liquid phase

Upgrading of pyrolysis oil from biomass offers great potential economic and environmental benefits for the production of sustainable and renewable energy sources. Meanwhile, challenges remain in the development of technical- and cost-effective catalysts and operating processes. One promising approach is liquid phase upgrading, which exhibits numerous benefits. This paper reviews recent progress and future possibilities for obtaining fuels from biomass using this approach. Key upgrading reactions for different oxygenated compounds in pyrolysis oil, including ketonization, aldol condensation, alkylation, hydrodeoxygenation, and oxygenation are discussed. Development of effective catalysts and efficient integration of multiple consecutive reaction steps in one single reactor make liquid phase upgrading competitively advantageous.

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► Bio-oil upgrading in the liquid phase offers numerous benefits.
► Liquid phase condensation reactions include ketonization, aldol condensation, and alkylation.
► Hydrodeoxygenation in the liquid phase under moderate conditions is an important goal.
► Sugars can be oxygenated to acids, which in turn can be ketonized.