Dried chitosan-gels as organocatalysts for the production of biomass-derived platform chemicals

Aldol condensations between sugar-derived dehydrated aldehydes (e.g. furfural) and acetone have been proposed as a route to provide useful biomass-derived chemicals. In the quest of sustainable catalytic ways for such aldol condensations, this paper assesses the use of dried chitosan-gels as naturally-immobilized, readily available and non-hazardous amino-based organocatalysts. At room temperature chitosan dried gels are not suitable catalysts for the desired reaction. However, at higher temperatures (>90 °C) reaction proceeds efficiently either in solvent-free systems (with addition of catalytic amounts of water) or in water. The set-up of closed reactor set-ups (thermoshakers or microwave reactions) proved highly beneficial for the reaction outcome. Furthermore, chitosan dried gels were successfully re-used for a number of cycles. An efficient catalyst drying method (either lyophilization or scCO2 drying) was crucial to achieve virtually full conversions in 4 h. After pertinent further process optimization, dried chitosan-gels may become very useful catalysts for their use in biomass-based reactions in biorefineries.

.Figure optionsDownload high-quality image (173 K)Download as PowerPoint slideHighlights
► Aldol condensation of furfural and acetone provides useful platform chemicals.
► Chitosan (presently a waste), catalyzes aldol condensation of furfural and acetone.
► Dried chitosan-gels lead to full conversions in 4 h under non-optimized conditions.
► As heterogeneous catalyst, recovery and reuse are straightforward.
► Worldwide available catalysts will be privileged in biorefineries.