Xiaojing Cui

Graphene oxide as a facile acid catalyst for the one-pot conversion of carbohydrates into 5-ethoxymethylfurfural

Graphene oxide obtained by the Hummers method was discovered to be an efficient and recyclable acid catalyst for the conversion of fructose-based biopolymers into 5-ethoxymethylfurfural (EMF). EMF yields of 92%, 71%, 34% and 66% were achieved when 5-hydroxymethylfurfural (HMF), fructose, sucrose and inulin were used as starting materials, respectively.

Water‐Promoted Hydrogenation of Levulinic Acid to γ‐Valerolactone on Supported Ruthenium Catalyst

A highly efficient and green process for the hydrogenation of biomass‐derived levulinic acid (LA) to γ‐valerolactone (GVL) has been developed. GVL was obtained in a yield of 99.9 mol % with a turnover frequency as high as 7676 h−1 in aqueous medium by using a Ru/TiO2 catalyst under mild reaction conditions (70 °C). The strong interaction between Ru and TiO2 facilitated both the dispersion of Ru nanoparticles and the stability of the catalyst. In addition, as solvent, water participated in the hydrogenation of LA, which was confirmed by an isotope‐ labeling experiment with D (D2O). Specifically, the H atom(s) in water took part in the hydrogenation of the CO group of LA, which promoted the catalytic activity and GVL yield remarkably.

Conversion of carbohydrates to furfural via selective cleavage of the carbon–carbon bond: the cooperative effects of zeolite and solvent

Furfural is one of the most valuable biomass-derived platform molecules which is primarily produced from hemicellulose. It is of significant importance but still highly challenging to produce furfural from hexoses, which are extensively distributed in nature. In this paper, carbohydrates (cellulose, starch, inulin, maltose, sucrose, glucose and fructose) were transformed into furfural efficiently over Hβ zeolite in a γ-butyrolactone–water solvent. The key process for converting hexoses into furfural is the selective cleavage of the C–C bond in hexoses to pentoses. The Hβ zeolite was discovered to induce the formation of acyclic hexoses, and the synergy between Hβ and solvent enables the selective C–C bond cleavage of acyclic hexoses into pentoses and promotes the subsequent dehydration of pentoses into furfural. Furfural yields for converting fructose and glucose reached 63.5% and 56.5% under milder conditions (150 °C), respectively. Moreover, a favorable yield of 38.5% for furfural can be achieved by direct conversion of cellulose.

Direct conversion of carbohydrates to γ-valerolactone facilitated by a solvent effect

The carbohydrates (cellulose, starch, inulin, maltose, sucrose, glucose and fructose) were converted efficiently into γ-valerolactone (GVL) over combined H3PW12O40 and Ru/TiO2 catalysts under mild conditions. The basicity of oxygen-containing solvents had a remarkable effect on the acid strength of H3PW12O40, which resulted in great variation in the yield of GVL. H3PW12O40 was more effective in 20 vol% water/γ-butyrolactone than in pure water and other water/organic solvents (methanol, ethanol and 1,4-dioxane). GVL yields for inulin and fructose reached 70.5 mol% and 67.6 mol% respectively. Meanwhile, a GVL yield of 40.5 mol% was achieved for cellulose. In addition, a practical method for catalyst recycling and GVL separation was developed by adding sugar into the reaction mixture. H3PW12O40 and Ru/TiO2 maintained their activity after three recycling runs.

Conversion of Xylose to Furfuryl Alcohol and 2-Methylfuran in a Continuous Fixed-Bed Reactor

An efficient process was designed for the synthesis of furfuryl alcohol and 2-methylfuran from xylose using a continuous fixed-bed reactor over a catalyst combining Hβ zeolite and Cu/ZnO/Al2 O3 in γ-butyrolactone (GBL)/water as solvent. The cooperative effect of Hβ zeolite and GBL facilitated the dehydration of xylose and enhanced largely the furfural yield. The production of furfuryl alcohol and 2-methylfuran can be simply tuned by changing the hydrogenation temperature for furfural over the Cu/ZnO/Al2 O3 catalyst. The yield for furfuryl alcohol reached 87.2 % at 150 °C whereas a yield of 86.8 % was achieved for 2-methylfuran at 190 °C.

Cleavage of C–N bonds in carbon fiber/epoxy resin composites

The incompletely coordinated zinc ions in water enable the cleavage of R2C(secondary carbon)–N bonds without breaking the C–O (aromatic ether) and C–C bonds in carbon fiber/epoxy resin composites. This selective cleavage of C–N bonds favors the recovery of valuable carbon fiber and the basic carbon unit of epoxy resin from their waste composites.

Chemical recycling of unsaturated polyester resin and its composites via selective cleavage of the ester bond

An efficient strategy has been developed for chemical recycling of unsaturated polyester resin (UPR) and its glass fibre reinforced polymer composites (GFRP) by selectively cleaving C–O bonds using the AlCl3/CH3COOH system. AlCl3 promotes acyl exchange reaction between CH3COOH and UPR. This process facilitates recovery of valuable oligomers and monomers from UPR, and glass fibres from GFRP.

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.

The origin of Mo promotion during H2 pretreatment on an Fe catalyst for Fischer–Tropsch synthesis

It is of vital importance but remains a grand challenge to understand comprehensively the effect of promoter elements on the active sites. Here, we report the experimental evidence of the origin of the promotion of molybdenum (Mo) during H2 pretreatment on iron (Fe) catalysts for Fischer–Tropsch synthesis (FTS). By combing in situ laser Raman spectroscopy, Mossbauer spectroscopy, electron microscopy and in situ infrared spectroscopy, the promotion is related to the dispersion of Mo on the Fe surface during H2 pretreatment, which inhibits the agglomeration of Fe and favors the formation of small Fe nanoparticles (NPs). The Mo coverage showed a strong dependency on the pretreatment temperature and the Mo amount in the FeMo catalyst. The strong Fe–Mo interaction caused by the Mo coverage weakened the activation of CO molecules on active Fe sites, which primarily accounts for the decline in the intrinsic activity (TOFCO) of active Fe sites.