Catalytic biomass conversion and upgrading into platform chemicals and liquid fuels

Abstract

The development of novel, efficient catalytic processes for plant biomass conversion and upgrading into versatile platform chemicals as well as oxygenated biodiesel and premium hydrocarbon kerosene/jet fuels is described in this dissertation. The chief motivation of using annually renewable biomass as the source of chemical building blocks and transportation fuels is to reduce societal dependence on depleting fossil fuels. Towards this goal, 5-hydroxymethylfurfural (HMF), the dehydration product from C6 (poly)sugars, has been intensively investigated as it has been identified as a versatile C6 intermediate or platform for value-added chemicals and biofuels. This work has developed several highly efficient and cost-effective catalyst systems for C6 (poly)sugars conversion to HMF under mild conditions, including ubiquitous and inexpensive aluminum alkyl or alkoxy compounds, recyclable polymeric ionic liquid (PIL)-supported metal (Cr, Al) catalysts, and thiazolium chloride, a recyclable Vitamine B1 analog. An integrated, semi-continuous process for the HMF production from fructose has also been developed, affording the high-purity HMF as needle crystals. Towards HMF upgrading into higher-energy-density fuel intermediates, developing new strategies of C-C bond formation or chain extension is of particular interest. In this context, this study has discovered that N-heterocyclic carbenes (NHCs) are highly effective organic catalysts for HMF self-condensation to 5,5'-dihydroxymethylfuroin (DHMF), a new C12 biorefining building block. This new upgrading process has 100% atom economy, can be carried out under solvent-free conditions, and produces the C12 DHMF with quantitative selectivity and yield, the hallmarks of a "green" process. More significantly, the C12 DHMF has been transformed catalytically into oxygenated biodiesels, high-quality alkane jet fuels, and sustainable polymers, thereby establishing DHMF as a new C12 biomass platform chemical.