Directed glycerol conversion to 2,5-hexanedione and more advanced poly-oxygenates as platform chemicals and high energy–density fuel additives

Bioenergy and biochemicals play a central and critical role to establish energy security and enable the required green and low carbon transition of the gigantic chemical industry amid the great concerns over climate change and sustainable development. Here, we describe the selective catalytic conversion of glycerol to 2,5-hexanedione and other more advanced C6-C12 poly-oxygenates by making use of water hydrogen under relatively mild conditions, using an effective copper metal–organic framework (Cu-MOF) derived catalyst. 2,5-hexanedione is a versatile platform chemical and a key intermediate for producing high energy–density aviation fuels from biomass resources. The catalyst was found to exhibit rarely seen catalytic activities both for the desirable glycerol conversion and for the aqueous reforming reactions for in-situ hydrogen generation, which is essential to drive the conversion to polyoxygenates consisting primarily of polyketones and polyalcohols. The selectivity could reach 43.4% for 2,5-hexanedione formation and over 70% for total C8-C12 poly-oxygenates. Characterizations show that the remarkable catalytic capability of MOF derived catalyst for the formation of novel advanced chemicals arose not only from the highly dispersion of copper in the substrate but also from the unique chemical states of the copper species, which together lead to the formation of greatly enhanced active surface sites with novel catalytic activities that cannot be achieved with similar catalysts prepared with conventional methodologies. Based on the results, the reaction mechanisms responsible for the desirable formation of 2,5-hexanedione were proposed. It is believed that the investigation opens up the possibility of recycling the crude glycerol from biodiesel production to produce novel advanced chemicals and/or high energy density transport fuels or fuel additives.