Guangqiang Lv

Direct synthesis of 2,5-diformylfuran from fructose with graphene oxide as a bifunctional and metal-free catalyst

The direct synthesis of 2,5-diformylfuran (DFF) from fructose is a tandem reaction that typically involves two steps catalyzed by two different catalysts, including fructose dehydration to 5-hydroxymethylfurfural (HMF) catalyzed by an acid catalyst and subsequent HMF oxidation to DFF catalyzed by a redox catalyst. In this study, graphene oxide, a metal-free carbon based material, was demonstrated to be an efficient and recyclable bifunctional catalyst in the direct synthesis of DFF from fructose. A DFF yield of 53.0% was achieved in a one pot and one-step reaction (O2, 24 h) and the DFF yield could be further increased to 72.5% in a one pot and two-step reaction (N2, 2 h and O2 22 h).

Aerobic selective oxidation of 5-hydroxymethyl-furfural over nitrogen-doped graphene materials with 2,2,6,6-tetramethylpiperidin-oxyl as co-catalyst

N-doped graphene materials with various types and quantities of N species were prepared via thermal treatment of graphene oxide in flowing NH3, and their catalytic performance was tested in aerobic selective oxidation of 5-hydroxymethyl-furfural (HMF). A full HMF conversion and nearly 100% selectivity to DFF can be obtained under relatively mild reaction conditions (6 h, 100 °C, 1 atm air pressure) with 2,2,6,6-tetramethylpiperidin-oxyl (TEMPO) as co-catalyst. The reduction degree of graphene oxide in NH3 was characterized by visible Raman spectroscopy. The amount and nature of doped nitrogen species were examined by X-ray photoelectron spectroscopy to reveal the genesis of active species by nitrogen doping. The graphitic nitrogen species doped into the graphene lattice were demonstrated to be responsible for the activation of molecular oxygen. In the selective oxidation of HMF, N-doped graphene showed a much lower apparent activation energy (ca. 13.5 kJ mol−1) compared with conventional active carbon supported metal catalysts (Ru/C, Pt/C, Pd/C, Au/C, 51–77 kJ mol−1). Based on current results and previous reports, a possible reaction pathway with the graphitic N species as active sites was proposed. This study examines the origin of the enhanced catalytic activity, which can be linked to the synergistic effect of TEMPO, N-doped graphene and molecular oxygen. This kind of synergistic effect makes the oxidation of HMF run smoothly. The present study demonstrates the potential of functionalized nitrogen-doped graphene materials as an efficient and alternative material to metal-based catalysts for organic synthetic reactions.

Vanadium-oxo immobilized onto Schiff base modified graphene oxide for efficient catalytic oxidation of 5-hydroxymethylfurfural and furfural into maleic anhydride

Graphene oxide (GO) sheets are emerging as a new class of carbocatalyst, and also a perfect platform for molecular engineering. The hydroxyl groups on either side of GO sheets can function as anchors by employing them as scaffolds linking organometallic nodes and vanadium-oxo was homogeneously immobilized on a Schiff base modified GO support via covalent bonding. The developed VO–NH2-GO was shown to be an efficient and recyclable heterogeneous catalyst for the aerobic oxidation of 5-hydroxymethylfurfural (HMF) into maleic anhydride. Up to 95.3% yield of maleic anhydride from HMF and 62.4% from furfural were achieved under optimized reaction conditions. The immobilized vanadium oxo was identified as the active sites, while the residual oxygen-containing groups worked synergistically to adsorb HMF to maintain a high reactant concentration around the catalyst. The STY value was enhanced significantly over VO–NH2-GO, compared with homogeneous or heterogeneous traditional supported V based catalyst.

A selective and economic carbon catalyst from waste for aqueous conversion of fructose into 5-hydroxymethylfurfural

It is of vital importance to design stable and selective heterocatalysts for aqueous production of platforms from biomass-derived sugars. This paper describes a selective aqueous conversion of fructose to HMF using carbon catalysts from pulping waste sodium ligninsulfonate (SLS). The effect of carbonization atmospheres (N2 flow, static air and air flow) on the structure, porosity, compositions and acidic properties of carbon catalysts were investigated by thermogravimetry-mass spectrum analysis, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Boehm titrations, N2 adsorption–desorption isotherms and elemental analysis. The carbonization in air flow favored the formation of more oxygen-containing functional groups and micropores, while more sulfonic groups and meso-/macro-pores were formed during carbonization in a static air atmosphere. Both oxygen- and sulfur-containing groups were acid sites, and their total amount was the largest when carbonized in air flow, followed by static air and N2 flow. The positive correlation between the acid amounts and fructose conversion of carbon catalysts clearly demonstrated the catalytic effect of the acid sites. The steric hindrance of micropores in carbon catalysts restricted the formation of humins and promoted the HMF selectivity compared with meso-/macro-pores.

Obtaining a high value branched bio-alkane from biomass-derived levulinic acid using RANEY® as hydrodeoxygenation catalyst

Compared to 5-HMF (C6H6O3), angelica lactone (C5H6O2) is a platform compound that has more potential for biomass-derived high performance bio-alkane fuel production due to a CC bond in the molecular structure, leading to a C–C coupling intermediate (C10 self-aggregation dimer) and higher C:O ratio (2.5), resulting in lower hydrogen consumption for the subsequent hydrodeoxygenation process. Biomass-derived levulinic acid was used as the only starting raw material to produce C10 branched alkanes. First, carboxyl and carbonyl functional groups of levulinic acid under catalysis via intramolecular esterification and dehydration yielded angelica lactone, which included two isomers of angelica lactone (α-angelica lactone and β-angelica lactone). Secondly, angelica lactone di/trimers would be obtained by angelica lactone self-aggregation: α-angelica lactone and β-angelica lactone connecting via C–C bond coupling. Finally, these intermediate products are selectively hydrodeoxygenated over a RANEY® catalyst to obtain C7–C10 branched alkanes. Nearly a 90% yield can be achieved under 483 K and 5 MPa H2 and the C10 branched alkane product, 3-ethyl-4-methyl heptane, accounts for 75% of the same.

Value-Added Utilization of the Lignin-Derived Phenol Monomer and Bioethanol to Synthesize Ethylphenol and Ethyl Phenyl Ether

This research focuses on high-value utilization of the lignin-derived phenol monomer and bioethanol from biorefining process. Supported-heteropolyacid is easily used as an efficient catalyst for the ethylation of phenol with bioethanol to obtain value-added products. Through adjusting the loading amount, different acidity amount and strength can be obtained, leading to the tunable selectivity to the phenol ethylation route and regioselectivity.