Carbohydrate dehydration using porous catalysts

Sugar dehydration is an effective way to deoxygenate biomass for the production of renewable chemicals and fuels. This chemistry typically happens using inorganic acids that impose major environmental burdens. We review the use of heterogeneous microporous and mesoporous catalysts for this chemistry and the key attributes of such materials, that is, the ratio of Brønsted to Lewis acid sites, mesoporosity, and hydrophobicity. While some of these materials, especially those combining microporosity and mesoporosity, show promising results for biomass processing in aqueous environment, there is a clear lack of fundamental understanding that severely limits their commercial use for these reactions. Potential barriers that need to be overcome for the use of heterogeneous acid catalysts are discussed.

► Microporous and mesoporous materials are promising catalysts for sugar dehydration reactions.
► Acid strength and type, pore size distribution, and hydrophobicity appear to affect catalyst activity and selectivity.
► The relative importance of each of these properties depends strongly on reaction conditions.
► The roles of these properties (and reaction conditions) are difficult to quantify because they are interdependent.
► More studies are needed for a fundamental understanding of these properties.