Reaction Pathways and Mechanisms in Thermocatalytic Biomass Conversion II

Abstract

Although less studied than acid-catalyzed reactions, mainly because of their marginal interest in petrochemical processes, base-catalyzed reactions (either homogeneous or heterogeneous) play a key role in the upgrading of biomass- derived platform molecules. As in most of the chemical processes, the replacement of homogeneous catalysts by heterogeneous catalysts is of key interest. This article reviews the state of the art in the most important base-catalyzed reactions in the biofuel manufacture (biodiesel from triglycerides) and the upgrading of biomass-derived platform molecules (such as acetone, ethanol, furfural, 5-hydroxymethylfurfural, or acetic acid). Transesterification reactions, aldol condensation (alone or in combination with other reactions), and ketonization are the main reactions involved in these biorefinery processes. Reviewed are the most common catalysts proposed for these reactions (mainly heterogeneous), as well as the proposed mechanisms for these reactions, and the main factors governing catalyst deactivation when used in each of these reactions.