Bifunctional Materials for the Catalytic Conversion of Cellulose into Soluble Renewable Biorefinery Feedstocks

Abstract

The combination of Bronsted acidity with metallic functionality in a mesoporous catalyst offers a potential pathway for the conversion of cellulose into sugar alcohols that may be used as a sustainable source of renewable biorefinery feedstock. Supported Ru catalysts were prepared by evaporative deposition on various ordered mesoporous silicas (SBA-15) with different functionalities and characterized using multiple experimental techniques. The catalytic performance of the supported Ru catalysts was compared to that of the corresponding supports and of Ru/C. We studied the effects of functional group loading, reaction time and temperature on the activity and products yield of the bifunctional catalysts by monitoring the cellulose conversion and the production of sugars and sugar alcohols in a high-pressure batch reactor. Sorbitol is the main product obtained by the hydrolysis of cellulose to glucose followed by the corresponding reduction. Secondary products include sugars, ethylene glycol and glycerol. The activity of mesoporous silica catalysts increases with an increase in acid loading and the addition of Ru allows control of the selectivity towards sugar alcohols. Ruthenium supported on arenesulfonic acid-functionalized mesoporous silica (Ru/SBA-15S) displays the best catalytic performance. Ru/SBA-15S is more hydrothermally stable than SBA-15, but loses a significant fraction of its surface area, crystallinity, acidity and activity after prolonged exposure to water at 483 K.