Biomass is a promising feedstock for the next generation drop-in liquid fuels and renewable chemicals, and hence the development of economically viable technologies for the production of commodity and specialty chemicals from sustainable biomass have received significant attention in recent years.While biomass transformation into drop-in biofuels involves multiple processing steps in which biomass is first depolymerized and converted to furfurals (5hydroxymethylfurfural, furfural), catalytic upgrading of furfurals is the most important step in achieving end products of the desired fuel properties. Several research articles have been published in the past decade reporting homogeneous and heterogeneous catalytic processes for upgrading furfurals to relevant drop-in fuel candidates such as, 2,5-dimethylfuran (DMF), 2methylfuran (2-MF), 5-ethoxymethylfurfural (EMF), γ-valorolactone (GVL), ethyl levulinate and long chain hydrocarbon alkanes. Although process technologies for the production and upgrading of some of these fuel compounds have been reviewed, a concise overview on production methodologies for all relevant furan based fuel compounds, including long chain hydrocarbon alkanes, from furfurals is yet to be published. This review article is aimed atpresenting an up to date analysis of the reported catalytic technologies for upgrading furfurals into long chain hydrocarbons with special emphasis on the condensation reactions for producing high carbon chain precursors and catalytic systems for their subsequent deoxygenation to achieve high yield and selectivity in fuel grade hydrocarbons. The current state-of-the-art on upgrading furfurals to DMF, 2-MF and EMF are also analyzed.

Graphene oxide, decorated with surface oxygen functionalities, has emerged as an alternative to precious-metal catalysts for many reactions. Herein, we report that graphene oxide becomes superactive for C–C coupling upon incorporation of a highly oxidized surface associated with Brønsted acidic oxygen functionality and defect sites along the surface and edges. The resulting improved graphene oxide (IGO) demonstrates significantly higher activity over commonly used framework zeolites for the upgrade of low-carbon biomass furanics to high-carbon fuel precursors. A maximum 95% yield of C15 fuel precursor with high selectivity is obtained at low temperature (60 °C) and neat conditions via hydroxyalkylation/alkylation (HAA) of 2-methylfuran (2-MF) and furfural. Coupling of 2-MF with carbonyl compounds ranging from C3 to C6 produces precursors of carbon numbers 12 to 21 with a high yield. The catalyst regains nearly full activity upon regeneration. Extensive microscopic and spectroscopic characterization of the fresh and reused IGO carbocatalysts indicates that defects and the enhanced oxygen content are strongly correlated with the high activity of IGO. Density functional theory calculations reveal defects at carbonyl sites as suitable Brønsted acidic oxygen functional groups. A plausible reaction mechanism is also hypothesized.

Plastics industry technologies currently source the majority of monomers from crude oil substances. Although we have witnessed a significant companies’ interest towards the utilization of the sustainable feedstock materials for...

Design and synthesis of effective heterogeneous catalysts for the conversion of biomass intermediates into long chain hydrocarbon precursors and their subsequent deoxygenation to hydrocarbons is a viable strategy for upgrading lignocellulose into distillate range drop-in biofuels. Herein, we report a two-step process for upgrading 5-hydroxymethylfurfural (HMF) to C9 and C11 fuels with high yield and selectivity. The first step involves aldol condensation of HMF and acetone with a water tolerant solid base catalyst, zirconium carbonate (Zr(CO3 )x ), which gave 92 % C9 -aldol product with high selectivity at nearly 100 % HMF conversion. The as-synthesised Zr(CO3 )x was analysed by several analytical methods for elucidating its structural properties. Recyclability studies of Zr(CO3 )x revealed a negligible loss of its activity after five consecutive cycles over 120 h of operation. Isolated aldol product from the first step was hydrodeoxygenated with a bifunctional Pd/Zeolite-β catalyst in ethanol, which showed quantitative conversion of the aldol product to n-nonane and 1-ethoxynonane with 40 and 56 % selectivity, respectively. 1-Ethoxynonane, a low oxygenate diesel range fuel, which we report for the first time in this paper, is believed to form through etherification of the hydroxymethyl group of the aldol product with ethanol followed by opening of the furan ring and hydrodeoxygenation of the ether intermediate.

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