Catalytic Upgrading of Biomass and its Model Compounds for Fuel Production

Abstract

The heavy dependence on fossil fuels raises many concerns on unsustainability and negative environmental impact. Biomass valorization to sustainable chemicals and fuels is an attractive strategy to reduce the reliance on fossil fuel sources. Gasification, liquefaction and pyrolysis are the main thermochemical technologies for biomass conversion. Gasification occurs at high temperature and yields the gas (syngas) as the main product. Liquefaction is conducted at low temperature but high pressure, which mainly produces liquid product with high quality. Biomass pyrolysis is performed at a moderate temperature and gives a primarily liquid product (bio-oil). However, the liquid product from biomass conversion is not advantageous for direct use as a fuel. Compared to liquefaction, pyrolysis is favorable when the aim is to produce the maximum amount of the liquid product from the biomass. Hydrotreating for bio-oil upgrading requires a large amount of expensive hydrogen, making this process costly. Catalytic cracking of bio-oil to reduce the oxygen content leads to a low H/C ratio. Methanolysis is a novel process that utilizes methane instead of hydrogen for biomass conversion. The feasibility studies show that this approach is quite promising. The original complexity of biomass and variation in composition make the composition of the product from biomass conversion unpredictable. Model compounds are employed to better understand the reaction mechanism and develop an optimal catalyst for obtaining the desired product. The major thermochemical technologies and the mechanism based on model compound investigations are reviewed in the article.