High-yield production of 2,5-dimethylfuran from 5-hydroxymethylfurfural over carbon supported Ni–Co bimetallic catalyst

The catalytic conversion of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF) has attracted extensive research interests because DMF can be used as potential and competitive renewable transportation fuel or additives. Here we report a non-noble bimetallic catalyst with improved activity for hydrogenation and hydrogenolysis by introducing active carbon as support into a nickel–cobalt catalyst. The characterizations of the catalyst indicate that the Ni and Co species are uniformly dispersed on the active carbon through the wetness impregnation method. The influences of reaction temperature and hydrogen pressure are systematically investigated and an excellent yield (up to 95%) of DMF can be obtained at relatively mild conditions, 130 °C and 1 MPa H2, over the carbon supported Ni–Co bimetallic catalyst. The high catalytic activity originates from the synergistic effect between Ni and CoOxspecies, the high BET surface area of the catalyst, and the uniform dispersion of Ni and Co species on the active carbon. The catalyst could be reused for 5 times without loss of activity in a batch reactor. Futhermore, the conversion of HMF to DMF on a fixed-bed reactor was also investigated and the 2%Ni–20%Co/C catalyst exhibited an excellent yield to DMF (>90%) for 71 h time on stream, indicating the high activity and stability of the catalyst. © 2016 Science Press

Improving the performance of metal-organic frameworks for thermo-catalytic CO_(2)conversion:Strategies and perspectives

Climate change caused by the increasing emission of CO_(2)to the atmosphere has become a global concern.To ameliorate this issue,converting CO_(2)into valuable chemicals is highly desirable,enabling a sustainable low-carbon future.To this end,developing efficient catalytic systems for CO_(2)conversion has sparked intense interests from both academia and industry.Taking advantage of their highly porous structures and unique properties,metal−organic frameworks(MOFs)have shown great potential as heterogeneous catalysts for CO_(2)conversion.Various transformations involving CO_(2)have been accomplished over MOFs-based materials.Here we provide a comprehensive and up-to-date review on recent advances of heterogeneous CO_(2)thermocatalysis using MOFs,highlighting relationships between structures and properties.Special attention is given to the design strategies for improving the catalytic performance of MOFs.Avenues available to enrich the catalytic active sites in MOF structures are stressed and their respective impacts on CO_(2)conversion efficiency are presented.The synergistic effects between each active site within the structure of MOFs and derivatives are discussed.In the end,future perspectives and challenges in CO_(2)conversion by heterogeneous catalysis with MOFs are described.

Catalytic hydrotreatment of humins into cyclic hydrocarbons over solid acid supported metal catalysts in cyclohexane

Humins are common undesirable sideproducts during many acid-catalyzed reactions in renewable biomass platform conversion. However, few studies have been reported to the efficient utilization of humins.For the first time, the selective catalytic conversion of biomass-derived humins into cyclic hydrocarbons with high conversion rate and selectivity is presented using a home-made Ru/W-P-Si-O bifunctional catalyst. The multistage polymerization structure of humins was studied through controlled experiments.Results show that the CAC bond network can be efficiently depolymerized at a mild reaction temperature of 340–380 °C, catalyzed by the cooperative catalysis of nano-Ru particles and porous strong Lewis solid acid. Particularly, 95.4% conversion of humins was achieved under the optimal condition with up to 88.3%yield of cyclic hydrocarbons. The detailed composition after liquefaction was also analyzed. This study paves the way for the efficient production of cyclic and aromatic hydrocarbons from furan-derived humin polymer through Lewis acid-catalyzed Diels–Alder reactions between furan rings.

Honeycomb-like g-C_(3)N_(4)/CeO_(2)-x nanosheets obtained via one step hydrothermal-roasting for efficient and stable Cr(Ⅵ) photo-reduction

Graphitic carbon nitride(g-C_(3)N_(4))-based materials are regarded as one of the most potential photocatalysts for utilizing solar energy.In this work,we reported a facile one step in-situ hydrothermal-roasting method for preparing honeycomb-like g-C_(3)N_(4)/CeO_(2) nanosheets with abundant oxygen vacancies(g-C_(3)N_(4)/CeO_(2)-x).The hydrothermal-roasting and incomplete-sealed state can(i)generate an in-situ reducing atmosphere(CO,N2,NH3) to tune the concentration of oxygen vacancies in CeO_(2);(ii) beneficial to prevent continuous growth of g-C_(3)N_(4) and results in honeycomb-like g-C_(3)N_(4)/CeO_(2)-x hybrid nanosheets.What is more,the g-C_(3)N_(4)/CeO_(2)-x photocatalyst exhibited extended photoresponse range,increased specific surface area and obviously enhanced separation efficiency of photogenerated electron-hole pairs.As a proof-of-concept application,the optimized g-C_(3)N_(4)/CeO_(2)-xnanosheets could achieve 98% removal efficiency for Cr(Ⅵ) under visible light irradiation(λ≥420 nm)within 2.5 h,which is significantly better than those of pure g-C_(3)N_(4) and CeO_(2).This work provides a new idea for more rationally designing and constructing g-C_(3)N_(4)-based catalysts for efficient extended photochemical application.

Recent advances in heterogeneous catalytic conversion of glucose to 5-hydroxymethylfurfural via green routes

With concerns of diminishing fossil fuel reserves and environmental deterioration, great efforts have been made to explore novel approaches of efficiently utilizing bio-renewable feedstocks to produce chemicals and fuels. 5-Hydroxymethylfurfural(HMF),generated from dehydration of six-carbon ketose, is regarded as a primary and versatile renewable building block to realize the goal of production of these high valued products from renewable biomass resources transformation. In this review, we summarize the recent advances via green routes in the heterogeneous reaction system for the catalytic production of HMF from glucose conversion, and emphasize reaction pathways of these reaction approaches based on the fundamental mechanistic chemistry as well as highlight the challenges(such as separation and purification of products, reusing and regeneration of catalyst, recycling solvent) in this field.