Bing Liu

Selective aerobic oxidation of the biomass-derived precursor 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid under mild conditions over a magnetic palladium nanocatalyst

A new method for the selective aerobic oxidation of 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA) has been developed employing a magnetically separable [γ-Fe2O3@HAP-Pd(0)] catalyst. The catalyst was prepared by the exchange of Pd2+ with Ca2+ in γ-Fe2O3@HAP, followed by reduction of the Pd2+ to Pd(0) nanoparticles, and well characterized by TEM, XRD and XPS. The catalyst showed high activity in the oxidation of HMF to FDCA in water, with 97% HMF conversion and a 92.9% yield of FDCA under optimal reaction conditions. The method developed has demonstrated some advantages, including its sole requirement of a stoichiometric base, and high catalytic performance under atmospheric oxygen, even in air. More importantly, the γ-Fe2O3@HAP-Pd(0) catalyst was readily separated from the reaction solution using an external magnetic field and was successfully reused during five consecutive reaction runs while retaining its catalytic effectiveness. This study provides a green and sustainable method for the production of valuable chemicals from renewable resources.

Aerobic oxidation of 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid in water under mild conditions

In this study, Pd nanoparticles were immobilized on the core–shell structure C@Fe3O4 (carbon is the shell and Fe3O4 is the core) magnetic microspheres via in situ adsorption and reduction to generate the magnetically separable Pd/C@Fe3O4 catalyst. In this method, no excess reductant and capping reagents were required, and it is a clean, simple and green process for the preparation of the magnetic Pd nanocatalyst. The Pd/C@Fe3O4 catalyst showed high activity and extraordinary stability during the oxidation of biomass derived 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA) under mild conditions. A study aimed at optimizing the reaction conditions such as reaction temperature, reaction solvent and base amount has been performed. Under optimal reaction conditions, HMF conversion of 98.4% and FDCA yield of 86.7% were achieved after 6 h at 80 °C. After reaction, the Pd/C@Fe3O4 catalyst could be easily recovered by an external magnet and reused without the loss of its activity.

Efficient conversion of cellulose into biofuel precursor 5-hydroxymethylfurfural in dimethyl sulfoxide-ionic liquid mixtures.

In recent years, cellulose has received increasing attention as a potential material for the production of biofuels and bio-based chemicals. In this study, a new process for the efficient conversion of cellulose into 5-hydroxymethylfurfural (HMF) was developed by the use of AlCl3 as the catalyst in DMSO-ionic liquid ([BMIM]Cl) mixtures. Various reaction parameters such as reaction time, reaction temperature, solvent and catalyst dosage were investigated in detail. A high HMF yield of 54.9% was obtained from cellulose at 150°C after 9h in a mixed solvent of DMSO-[BMIM]Cl (10 wt.%). More importantly, the catalytic system could be reused for several times despite of the slight loss of its catalytic activity.

A novel magnetic palladium catalyst for the mild aerobic oxidation of 5-hydroxymethylfurfural into 2,5-furandicarboxylic acid in water

In this study, magnetically separable, graphene oxide-supported palladium nanoparticles (C–Fe3O4–Pd) were successfully prepared via a one-step solvothermal route. The C–Fe3O4–Pd catalyst showed excellent catalytic performance in the aerobic oxidation of 5-hydroxymethylfurfural (HMF) into 2,5-furandicarboxylic acid (FDCA). The base concentration and reaction temperature significantly affected both HMF conversion and FDCA selectivity. High HMF conversion (98.2%) and FDCA yield (91.8%) were obtained after 4 h at 80 °C with a K2CO3/HMF molar ratio of 0.5. The C–Fe3O4–Pd catalyst was easily collected by an external magnet and reused without significant loss of its catalytic activity. The developed method is a green and sustainable process for the production of valuable FDCA from renewable, bio-based HMF in terms of the use of water as solvent, the use of stoichiometric amount of base, high catalytic activity under atmospheric oxygen pressure, and facile recyclability of the catalyst.

Aerobic oxidation of biomass derived 5-hydroxymethylfurfural into 5-hydroxymethyl-2-furancarboxylic acid catalyzed by a montmorillonite K-10 clay immobilized molybdenum acetylacetonate complex

In this study, we have successfully prepared a heterogeneous catalyst (K-10 clay-Mo) by the immobilization of bis(acetylacetonato) dioxo-molybdenum(VI) [MoO2(acac)2] on montmorillonite K-10 clay. The structure of the resultant catalyst was characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electronic microscopy (TEM), and Fourier transform infrared (FTIR) spectroscopy. The catalytic activity of K-10 clay-Mo was tested in the aerobic oxidation of 5-hydroxymethylfurfural (HMF). Although a molecule of HMF contains one hydroxyl group and one aldehyde group, to our surprise, the catalyst showed high catalytic activity for the oxidation of the aldehyde group of HMF into 5-hydroxymethyl-2-furancarboxylic acid (HMFCA). A variety of important reaction parameters such as the reaction temperature, catalyst amount, and solvent were explored. HMFCA could be obtained in a high yield of 86.9% with a HMF conversion of 100% after a short reaction time of 3 h in toluene. More importantly, the catalyst K-10 clay-Mo could be reused several times without a significant loss of its catalytic activity.

Cellulose sulfuric acid as a bio-supported and recyclable solid acid catalyst for the synthesis of 5-hydroxymethylfurfural and 5-ethoxymethylfurfural from fructose

In this study, we have developed a new and green method for the synthesis of 5-hydroxymethylfurfural (HMF) and 5-ethoxymethylfurfural (EMF) from fructose using cellulose sulfuric acid as catalyst. Firstly, HMF was synthesized from fructose, and a high yield of 93.6xa0% was obtained in DMSO for 45xa0min in the presence of cellulose sulfuric acid. Cellulose sulfuric acid also showed high catalytic activity for the synthesis of EMF. EMF was obtained in a high yield of 84.4xa0% by the etherification of HMF under the optimal reaction conditions. More importantly, a high EMF yield of 72.5xa0% was also obtained from fructose through one-pot reaction strategy, which integrated the dehydration of fructose into HMF and the followed etherification of HMF into EMF. The reaction work-up was very simple and the catalyst could be reused several times without the loss of its catalytic activity.

Magnetic material grafted cross-linked imidazolium based polyionic liquids: an efficient acid catalyst for the synthesis of promising liquid fuel 5-ethoxymethylfurfural from carbohydrates

Magnetic material grafted with acid polyionic liquids was successfully prepared by the radical oligomerization of bis-vinylimidazolium salts on the surface of mercaptopropyl-modified silica-coated Fe3O4, and well characterized by several model technologies. The as-prepared magnetic catalyst (Fe3O4@SiO2–SH–Im–HSO4) showed high catalytic activity for the synthesis of 5-ethoxymethylfurfural (EMF) from 5-hydroxymethylfurfural (HMF) and fructose-based carbohydrates. The reaction temperature showed a remarkable effect on EMF yield. High EMF yield of 89.6% was obtained at 100 °C by the etherification of HMF. The one-pot conversion of fructose, sucrose and inulin catalyzed by Fe3O4@SiO2–SH–Im–HSO4 generated EMF with yields of 60.4%, 34.4% and 56.1%, respectively. The catalyst could be readily separated from the reaction mixture by a permanent magnet, and showed high stability in recycling experiments. This study shows a green and sustainable method for the synthesis of value-added liquid fuel from renewable resources.

Nitrogen-doped reduced graphene oxide-supported Mn3O4: An efficient heterogeneous catalyst for the oxidation of vanillyl alcohol to vanillin

Nitrogen-doped reduced graphene oxide-supported Mn3O4 nanoparticles (N-RGO/Mn3O4) were prepared by solvothermal method and characterized by several physical techniques such as TEM images, XRD, XPS, and N2 adsorption–desorption techniques. The as-made N-RGO/Mn3O4 catalyst was used for the oxidation of vanillyl alcohol to vanillin. Several important reaction parameters were investigated such as reaction solvent, oxygen concentration, reaction temperature, and catalyst loading. N,N-Dimethylformamide was found to be the best solvent, affording both high conversion and vanillin selectivity. 92.5xa0% conversion of vanillyl alcohol and 91.4xa0% selectivity of vanillin were achieved after 12xa0h at 120xa0°C under oxygen balloon by the use of 40xa0mg of the N-GO/Mn3O4 catalyst. Kinetic studies revealed that the active energy for the oxidation of vanillyl alcohol to vanillin over N-GO/Mn3O4 catalyst was 39.67xa0kJ.mol−1. More importantly, the catalyst was stable and could be reused for 6 times without the significant loss of its catalytic activity.

Temperature-Programmed Surface Reaction Study of Adsorption and Reaction of H2S on Ceria

H2S adsorption and reaction on CeO2, TiO2, and ?-Al2O3 were studied by temperature programmed surface reaction (TPSR). Ceria had the best desulfidation ability. The pretreatment atmosphere affected H2S adsorption and reaction on ceria, and desulfidation efficiency increased in the order of inert atmosphere, reducing atmosphere, oxidizing atmosphere. H2S was first adsorbed on pretreated ceria at room temperature. On increasing the temperature in an Ar (99.99%) atmosphere, part of the H2S desorbed below 673 K, and another part reacted with the surface oxygen on ceria to produce sulfur and water below 473 K, and SO2 between 473 and 673 K, which further reacted with lattice oxygen and was transformed into sulfate above 673 K. The sulfate decomposed into SO2 again at 873 K. To avoid the complex regeneration, it is advisable to carry out desulfidation below 673 K when using ceria as adsorbent.

Aerobic oxidation of biomass-derived 5-hydroxymethylfurfural to 2,5-diformylfuran with cesium-doped manganese dioxide

The selective oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) has attracted much attention in recent years. Cesium-doped manganese dioxide (Cs/MnOx) was prepared by a soft template method, and was found to be active for the selective oxidation of HMF to DFF with molecular oxygen. Various reaction conditions have been investigated, and DFF was attained with a high yield of 94.7% at a HMF conversion of 98.4% at 100 °C and 10 bar O2 in N,N-dimethylformamide. Cs/MnOx demonstrated much higher catalytic activity than un-doped MnOx, suggesting that the introduction of Cs into MnOx plays a crucial role in the oxidation of HMF to DFF. Kinetic studies demonstrated that the oxidation of HMF to DFF depends on both the HMF and oxygen concentration, with the reaction order being 0.44 and 0.53, respectively. Compared with other heterogeneous non-noble metal catalysts, Cs/MnOx demonstrated a much lower activation energy for the oxidation of HMF to DFF. The catalyst can be reused without much loss of catalytic activity, suggesting that the catalyst is highly stable. Furthermore, the direct production of HMF from fructose was also successfully realized by a one-pot reaction strategy via two consecutive steps.