Direct Production of 2,5-Dimethylfuran with High Yield from Fructose over a Carbon-Based Solid Acid-Coated CuCo Bimetallic Catalyst

2D MOF with Compact Catalytic Sites for the One-pot Synthesis of 2,5-Dimethylfuran from Saccharides via Tandem Catalysis

One pot synthesis of 2,5-dimethylfuran (2,5-DMF) from saccharides under mild conditions is of importance for the production of biofuel and fine chemicals. However, the synthesis requires a multitude of active sites and suffers from slow kinetics due to poor diffusion in most composite catalysts. Herein, a metal-acid functionalized 2D metal-organic framework (MOF; Pd/NUS-SO3 H), as an ultrathin nanosheet of 3-4 nm with Lewis acid, Brønsted acid, and metal active sites, was prepared based on the diazo method for acid modification and subsequent metal loading. This new composite catalyst gives substantially higher yields of DMF than all reported catalysts for different saccharides (fructose, glucose, cellobiose, sucrose, and inulins). Characterization suggests that a cascade of reactions including polysaccharide hydrolysis, isomerization, dehydration, and hydrodeoxygenation takes place with rapid molecular interactions.

Promoted Hydrogenolysis of Furan Aldehydes to 2,5-Dimethylfuran by Defect Engineering on Pd/NiCo2 O4

Catalytic hydrogenolysis of biobased furan aldehydes (i. e., 5-methylfurfural, 5-hydroxymethylfurfural) to 2,5-dimethylfuran has gained extensive interest for biomass-derived fuels and chemicals. Herein, a class of NiCo₂ O₄ -supported palladium with considerable oxygen defects was synthesized by hydrogen plasma etching and phosphating methods. The oxygen defects not only promoted the hydrogenation of the C=O group but also enhanced the accessibility of coordinatively unsaturated metal cations with Lewis acidity for the hydrogenolysis of the C-OH group. Meanwhile, the additional Brønsted acidity in Pd/NiCo₂ O_4-x obtained by phosphating could further strengthen the hydrogenolysis ability by the etherification route of C-OH. Finally, Pd/NiCo₂ O_4-x exhibited the most effective performance with 2,5-dimethylfuran yields of 92.9 and 90.5 % from 5-methylfurfural and 5-hydroxymethylfurfural, respectively. These catalytic mechanisms were confirmed by in-situ infrared spectroscopy and control experiments. Furthermore, the catalyst showed outstanding recycling stability. This work shows powerful synergistic catalysis in the hydrogenolysis reaction by multifunctional active sites.

Advanced Carbon-Based Nanocatalysts and their Application in Catalytic Conversion of Renewable Platform Molecules

The transformation of renewable platform molecules to produce value-added fuels and fine-chemicals is a promising strategy to sustainably meet future demands. Owing to their finely modified electronic and geometric properties, carbon-based nanocatalysts have shown great capability to regulate their catalytic activity and stability. Their well-defined and uniform structures also provide both the opportunity to explore intrinsic reaction mechanisms and the site-requirement for valorization of renewable platform molecules to advanced fuels and chemicals. This Review highlights the progress achieved in carbon-based nanocatalysts, mainly by using effective regulation approaches such as heteroatom anchoring, bimetallic synergistic effects, and carbon encapsulation to enhance catalyst performance and stability, and their applications in renewable platform molecule transformations. The foundation for understanding the structure-performance relationship of carbon-based catalysts has been established by investigating the effect of these regulation methods on catalyst performance. Finally, the opportunities, challenges and potential applications of carbon-based nanocatalysts are discussed.

Emerging heterogeneous catalysts for biomass conversion: studies of the reaction mechanism

The development of efficient catalysts to break down and convert woody biomass will be a paradigm shift in delivering the global target of sustainable economy and environment via the use of cheap, highly abundant, and renewable carbon resources. However, such development is extremely challenging due to the complexity of lignocellulose, and today most biomass is treated simply as waste. The solution lies in the design of multifunctional catalysts that can place effective control on substrate activation and product selectivity. This is, however, severely hindered by the lack of fundamental understanding of (i) the precise role of active sites, and (ii) the catalyst-substrate chemistry that underpins the catalytic activity. Moreover, active sites alone often cannot deliver the desired selectivity of products, and full understanding of the microenvironment of the active sites is urgently needed. Here, we review key recent advances in the study of reaction mechanisms of biomass conversion over emerging heterogeneous catalysts. These insights will inform the design of future catalytic systems showing improved activity and selectivity.

Selective 5-Hydroxymethylfurfural Hydrogenolysis to 2,5-Dimethylfuran over Bimetallic Pt-FeOx/AC Catalysts

The selective hydrogenolysis of 5-hydroxymethylfurfural (HMF) platform molecule to 2,5-dimethylfuran (DMF) has attracted increasing attention due to its broad range of applications. However, HMF, with multiple functional groups, produces various byproducts, hindering its use on an industrial scale. Herein, a bimetallic Pt-FeOx/AC catalyst with low Pt and FeOx loadings for selective HMF hydrogenolysis to DMF was prepared by incipient wetness impregnation. The structures and properties of different catalysts were characterized by XRD, XPS, TEM, ICP-OES and Py-FTIR techniques. The addition of FeOx enhanced Pt dispersion and the Lewis acidic site density of the catalysts, and was found to be able to inhibit C=C hydrogenation, thereby im-proving DMF yield. Moreover, the presence of Pt promoted the reduction of iron oxide, creating a strong interaction between Pt and FeOx. This synergistic effect originated from the activation of the C–O bond over FeOx species followed by hydrogenolysis over the adjacent Pt, and played a critical role in hydrogenolysis of HMF to DMF, achieving a yield of 91% under optimal reaction conditions. However, the leaching of Fe species caused a metal–acid imbalance, which led to an increase in ring hydrogenation products.

Non Noble-Metal Copper-Cobalt Bimetallic Catalyst for Efficient Catalysis of the Hydrogenolysis of 5-Hydroxymethylfurfural to 2,5-Dimethylfuran under Mild Conditions

The efficient catalysis of the hydrogenation of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF) over non noble-metal catalysts has received great attention in recent years. However, the reaction usually requires harsh conditions, such as high reaction temperature and excessively long reaction time, which limits the application of the non noble-metal catalysts. In this work, a bimetallic Co _x -Cu@C catalyst was prepared via the pyrolysis of MOFs, and an 85% DMF yield was achieved under a reaction temperature and time of 160 °C and 3 h, respectively. The results of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDX) mapping, and other characterization techniques showed that the synthesis method in this paper realized the in situ loading of cobalt into the copper catalyst. The reaction mechanism studies revealed that the cobalt doping effectively enhanced the hydrogenation activity of the copper-based catalyst on the C-O bond at a low temperature. Moreover, the bimetallic Co _x -Cu@C catalyst exhibited superior reusability without any loss in the activity when subjected to five testing rounds.