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FtpM from Aspergillus fumigatus was the first carboxyl methyltransferase reported to catalyse the dimethylation of dicarboxylic acids. Here the creation of mutant R166M that can catalyse the quantitative conversion of bio-derived 2,5-furandicarboxylic acid (FDCA) to its dimethyl ester (FDME), a bioplastics precursor, was reported. Wild type FtpM gave low conversion due to its reduced catalytic efficiency for the second methylation step. An AlphaFold 2 model revealed a highly electropositive active site, due to the presence of 4 arginine residues, postulated to favour the binding of the dicarboxylic acid over the intermediate monoester. The R166M mutation improved both binding and turnover of the monoester to permit near quantitative conversion to the target dimethyl ester product. The mutant also had improved activity for other diacids and a range of monoacids. R166M was incorporated into 2 multienzyme cascades for the synthesis of the bioplastics precursor FDME from bioderived 5-hydroxymethylfurfural (HMF) as well as from poly(ethylene furanoate) (PEF) plastic, demonstrating the potential to recycle waste plastic., (© 2023 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

5-Hydroxymethylfurfural (5-HMF) represents a well-known class of lignocellulosic biomass-derived platform molecules. With the presence of many reactive functional groups in the structure, this versatile building block could be valorized into many value-added products. Among well-established catalytic transformations in biorefinery, the reductive amination is of particular interest to provide valuable N-containing compounds. Specifically, the reductive amination of 5-HMF with ammonia (NH 3 ) and molecular hydrogen (H 2 ) offers a straightforward and sustainable access to primary furanic amines [i. e., 5-hydroxymethyl-2-furfuryl amine (HMFA) and 2,5-bis(aminomethyl)furan (BAMF)], which display far-reaching utilities in pharmaceutical, chemical, and polymer industries. In the presence of heterogeneous catalysts contanining monometals (Ni, Co, Ru, Pd, Pt, and Rh) or bimetals (Ni-Cu and Ni-Mn), this elegant pathway enables a high-yielding and chemoselective production of HMFA/BAMF compared to other synthetic routes. This Review aims to present an up-to-date highlight on the supported metal-catalyzed reductive amination of 5-HMF with elaborate studies on the role of metal, solid support, and reaction parameters. Besides, the recyclability/adaptability of catalysts as well as the reaction mechanism are also provided to give valuable insights into this potential 5-HMF valorization strategy., (© 2022 Wiley-VCH GmbH.)

In recent years, electrocatalysis was progressively developed to facilitate the selective oxidation of biomass-derived 5-hydroxymethylfurfural (HMF) towards the value-added chemical 2,5-furandicarboxylic acid (FDCA). Among reported electrocatalysts, alloy materials have demonstrated superior electrocatalytic properties due to their tunable electronic and geometric properties. However, a specific discussion of the potential impacts of alloy structures on the electrocatalytic HMF oxidation performance has not yet been presented in available Reviews. In this regard, this Review introduces the most recent perspectives on the alloy-driven electrocatalysis for HMF oxidation towards FDCA, including oxidation mechanism, alloy nanostructure modulation, and external conditions control. Particularly, modulation strategies for electronic and geometric structures of alloy electrocatalysts have been discussed. Challenges and suggestions are also provided for the rational design of alloy electrocatalysts. The viewpoints presented herein are anticipated to potentially contribute to a further development of alloy-driven electrocatalytic oxidation of HMF towards FDCA and to help boost a more sustainable and efficient biomass refining system., (© 2022 Wiley-VCH GmbH.)

Hydrogenation and hydrogenolysis are two important reactions for electrochemical reductive valorization of biomass-derived oxygenates such as 5-hydroxymethylfurfural (HMF). In general, hydrogenolysis (which combines hydrogenation and deoxygenation) is more challenging than hydrogenation (which does not involve the cleavage of carbon-oxygen bonds). Thus, identifying factors and conditions that can promote hydrogenolysis is of great interest for reductive valorization of biomass-derived oxygenates. For the electrochemical reduction of HMF and its derivatives, it is known that aldehyde hydrogenation is not a part of aldehyde hydrogenolysis but rather a competing reaction; however, no atomic-level understanding is currently available to explain their electrochemical mechanistic differences. In this study, combined experimental and computational investigations were performed using Cu electrodes to elucidate the key mechanistic differences between electrochemical hydrogenation and hydrogenolysis of HMF. The results revealed that hydrogenation and hydrogenolysis of HMF involve the formation of different surface-adsorbed intermediates via different reduction mechanisms and that lowering the pH promoted the formation of the intermediates required for aldehyde and alcohol hydrogenolysis. This study for the first time explains the origins of the experimentally observed pH-dependent selectivities for hydrogenation and hydrogenolysis and offers a new mechanistic foundation upon which rational strategies to control electrochemical hydrogenation and hydrogenolysis can be developed., (© 2022 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

Upgrading furfuralcohols and furfurals to furancarboxylic acids is of great significance for high value-added downstream chemicals synthesis and biomass conversion. Developing an efficient catalyst is the key to acquiring a completely sustainable process. Herein, nitrogen-doped carbon-supported bimetallic AuPd bowl-like catalysts were synthesized. The surface wettability of nitrogen-doped carbon was well adjusted by the nitrification process. Benefiting from the alloying effect of bimetallic AuPd catalyst and the formation of hydroxyl radical initiated by H 2 O dissociation on the hydrophilic surface of nitrated nitrogen-doped carbon, base-free aerobic oxidation of 5-hydroxymethylfurfural (HMF) could produce the highest 2,5-furandicarboxylic acid (FDCA) yield of 93.9 %. In-situ infrared spectroscopy uncovered adsorption configuration of HMF, and the nitrated carbon surface was favorable for HMF and intermediates to enter the active sites, greatly promoting the catalytic oxidation process. Employing other furfuralcohols (furfuryl alcohol, furan-2,5-diyldimethanol, 2,5-bishydroxymethylfuran) as well as furfural and 5-methylfurfural as starting materials, 35.6-95.4 % yield of furancarboxylic acids (FDCA, 2-furoic acid, 5-methyl-2-furoic acid) were also obtained. Moreover, the developed catalysts could maintain excellent stability and activity after four successive runs. This deep insight into the role of bimetallic synergy and surface wettability provides a basis for the rational design of the highly efficient catalysts for the oxidation of furfuralcohols and furfurals and related reactions., (© 2022 Wiley-VCH GmbH.)

The oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-furandicarboxylic acid (FDCA) is highly attractive as FDCA is considered as substitute for the petrochemically derived terephthalic acid. There are only few reports on the direct use of unrefined HMF solutions from biomass resources and the influence of remaining constituents on the catalytic processes. In this work, the oxidation of HMF in a solution as obtained from hydrolysis and dehydration of saccharides in chicory roots was investigated without intermediate purification steps. The amount of base added to the solution was critical to increase the FDCA yield. Catalyst deactivation occurred and was attributed to poisoning by amino acids from the bio-source. A strong influence of amino acids on the catalytic activity was found for all supported Au, Pt, Pd, and Ru catalysts. A supported AuPd(2 : 1)/C alloy catalyst exhibited both superior catalytic activity and higher stability against deactivation by the critical amino acids., (© 2022 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

5-Hydroxymethylfurfural (5-HMF), one of the most important platform molecules in biorefinery, can be directly obtained from a vast diversity of biomass materials. Owing to the reactive functional groups (-CHO and -CH 2 OH) in the structure, this versatile building block undertakes several transformations to provide a wealth of high value-added products. Among numerous well-established paradigms, the catalytic hydrogenation of 5-HMF towards 2,5-bis(hydroxymethyl)tetrahydrofuran (BHMTHF) is of great interest because this downstream diol can be exploited in a wide range of industrial applications. Not surprisingly, incessant endeavors from both academia and industry to upgrade this catalytic process have been established over the years. The main aim of this Review was to provide a comprehensive overview on the development of heterogeneous metal catalysts for the 5-HMF-to-BHMTHF transformation. Herein, the rational design and utility of hydrogenating catalysts were elaborated in many aspects including metal types (Ni, Co, Pd, Ru, Pt, and bimetals), solid supports, preparation method, recyclability, operating conditions, and reaction regime (batch and continuous flow). In addition, the assessment of cooperative catalysts to convert carbohydrates into BHMTHF under one-pot cascade, tentative mechanism, as well as prospects and challenges for the chemo-selective hydrogenation of 5-HMF were also highlighted., (© 2022 Wiley-VCH GmbH.)

5-hydroxymethylfurfural (HMF) is an important bio-derived platform molecule that is generally obtained from hexoses via acid-catalyzed dehydration. It can be effectively transformed into a variety of value-added derivatives, thus being an ideal candidate for fossil replacement. Both HMF oxidation and hydrogenation processes enable the synthesis of numerous chemicals, monomers for polymerization, and biofuel precursors. This Review summarizes the most recent advances in heterogeneous catalytic hydroconversion of HMF into valuable chemicals with strong focus on 2,5-bishydroxymethyl furan (BHMF), 2,5-bishydroxymethyltetrahydrofuran (BHMTHF), and 2,5-dimethyltetrahydrofuran (DMTHF). In addition, multifunctional catalytic systems that enable a tunable production of various HMF derived intermediates are discussed. Within this chemistry, the surprising impact of HMF purity on the catalytic performance, such as selectivity and activity, during its upgrading is highlighted. Lastly, the remaining challenges in the field of HMF hydroconversion to the mentioned chemicals are summarized and discussed, taking into account the knowledge gain of catalyst properties and feedstock purity., (© 2022 Wiley-VCH GmbH.)

Designing highly efficient and low-cost catalysts for conversion of renewable biomass into high value-added chemicals and biofuels is important and challenging. Herein, a non-noble Ni-Mn bifunctional catalyst supported on activated carbon (Ni-Mn/AC) was developed by an incipient wetness impregnation method. The catalyst was found to be economic and efficient for the selective hydrodeoxygenation of biomass-derived 5-hydroxymethylfurfural (5-HMF) to 2,5-dimethylfuran (2,5-DMF). The optimal Ni-Mn/AC (Ni/Mn=3) catalyst achieved 98.5 % 2,5-DMF yield with 100 % conversion of 5-HMF under mild reaction conditions of 180 °C, 2.0 MPa H 2 for 4 h. Furthermore, the catalyst exhibited outstanding reusability and could be recycled eight times without loss of activity. The addition of Mn not only enhanced the reactivity of 5-HMF but also resulted in the dominant reaction pathway shift from the hydrogenation of the C=O bond to the hydrogenolysis of C-OH bond, which was attributed to the synergy of highly dispersed Ni metallic nanoparticles and moderate Lewis acid sites from MnO x as revealed by detailed characterizations., (© 2022 Wiley-VCH GmbH.)

5-hydroxymethylfurfural (HMF) has been successfully valorized into 3-hydroxymethylcyclopentylamine through a one-pot cascade process in aqueous phase by coupling the hydrogenative ring-rearrangement of HMF into 3-hydroxymethylcyclopentanone (HCPN) with a subsequent reductive amination with ammonia. Mono- (Ni@C, Co@C) and bimetallic (NiCo@C) nanoparticles with different Ni/Co ratios partially covered by a thin carbon layer were prepared and characterized. Results showed that a NiCo catalyst, (molar ratio Ni/Co=1, Ni 0.5 Co 0.5 @C), displayed excellent performance in the hydrogenative ring-rearrangement of HMF into HCPN (>90 % yield). The high selectivity of the catalyst was attributed to the formation of NiCo alloy structures as hydrogenating sites that limited competitive reactions such as the hydrogenation of furan ring and the over-reduction of the formed HPCN. The subsequent reductive amination of HPCN with aqueous ammonia was performed giving the target cyclopentylaminoalcohol in 97 % yield. Moreover, the catalyst exhibited high stability maintaining its activity and selectivity for repeated reaction cycles., (© 2022 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

The electrocatalytic reduction of 5-hydroxymethylfurfural (HMF) is highly selective to 2,5-bishydroxymethylfuran (BHMF) at pH=9.2, diluted HMF solutions, and low current densities. In this work, the electrochemical reduction of 0.05 m HMF solutions was investigated in the 5-50 mA cm -2 current density range over an AgCu foam electrocatalyst. The selectivity towards the formation of BHMF or the dimerization depended on the current density, likely due to differences in the electrode potential, and on the reaction time. Operating at current densities of 40-50 mA cm -2 allowed to find a trade-off between HMF and H 2 O activation, achieving 85 % BHMF selectivity and fostering the productivity (0.567 mmol cm -2  h -1 ), though co-producing H 2 . The electrochemical characterization by Tafel slopes and electrochemical impedance spectroscopy indicated that the HMF reduction was kinetically favored in comparison to the hydrogen evolution reaction and that the process was limited by charge transfer., (© 2022 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

The conversion of biomass into a great variety of valuable chemicals, polymers, and fuels gives a sustainable alternative for the insufficiency of non-renewable fossil fuel resources and reduces environmental pollution. 5-Hydroxymethylfurfural (HMF), converted from sustainable carbohydrates, is a significant building block chemical, and the selective oxidation of HMF into 2,5-diformylfuran (DFF) presents an ongoing challenge. DFF is a versatile platform molecule derived from biomass and has promising application in pharmaceuticals and polymers. This Review provides an overview of the latest developments of efficient catalytic systems for the sustainable conversion of HMF to DFF., (© 2022 Wiley-VCH GmbH.)

5-hydroxymethylfurfural (HMF) is one of the most valuable biomass platform molecules, enabling the construction of a plethora of high value-added furanic compounds. In particular, in the last decade, HMF has been considered as a starting material for designing biobased surfactants, not only because of its renewability and carbon footprint, but also because of its enhanced biodegradability. This Review presents recent examples of the different approaches to link the hydrophilic and lipophilic moieties into the hydrophobic furan (and tetrahydrofuran) ring, giving a variety of biobased surfactants that have been classified here according to the charge of the head polar group. Moreover, strategies for the synthesis of different non-furanic structures surfactant molecules (such as levulinic acid, cyclopentanols, and aromatics) derived from HMF are described. The new HMF-based amphiphilic molecules presented here cover a wide range of hydrophilic-lipophilic balance values and have suitable surfactant properties such as surface tension activity and critical micelle concentration, to be an important alternative for the replacement of non-sustainable surfactants., (© 2022 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

This Review summarizes recent efforts to capitalize on 5-hydroxymethylfurfural (HMF) and related furans as emerging building blocks for the synthesis of fine chemicals and materials, with a focus on advanced applications within medicinal and polymer chemistry, as well as nanomaterials. As with all chemical industries, these fields have historically relied heavily on petroleum-derived starting materials, an unsustainable and polluting feedstock. Encouragingly, the emergent chemical versatility of biomass-derived furans has been shown to facilitate derivatization towards valuable targets. Continued work on the synthetic manipulation of HMF, and related derivatives, for access to a wide range of target compounds and materials is crucial for further development. Increasingly, biomass-derived furans are being utilized for a wide range of chemical applications, the continuation of which is paramount to accelerate the paradigm shift towards a sustainable chemical industry., (© 2022 Wiley-VCH GmbH.)

The depletion of fossil resources is driving the research towards alternative renewable ones. Under this perspective, 5-hydroxymethylfurfural (HMF) represents a key molecule deriving from biomass characterized by remarkable potential as platform chemical. In this work, for the first time, the hydrogenation of HMF in ethanol was selectively addressed towards 2,5-bis(hydroxymethyl)furan (BHMF) or 2,5-bis(hydroxymethyl)tetrahydrofuran (BHMTHF) by properly tuning the reaction conditions in the presence of the same commercial catalyst (Ru/C), reaching the highest yields of 80 and 93 mol%, respectively. These diols represent not only interesting monomers but strategic precursors for two scarcely investigated ethoxylated biofuels, 2,5-bis(ethoxymethyl)furan (BEMF) and 2,5-bis(ethoxymethyl)tetrahydrofuran (BEMTHF). Therefore, the etherification with ethanol of pure BHMF and BHMTHF and of crude BHMF, as obtained from hydrogenation step, substrates scarcely investigated in the literature, was performed with several commercial heterogeneous acid catalysts. Among them, the zeolite HZSM-5 (Si/Al=25) was the most promising system, achieving the highest BEMF yield of 74 mol%. In particular, for the first time, the synthesis of the fully hydrogenated diether BEMTHF was thoroughly studied, and a novel cascade process for the tailored conversion of HMF to the diethyl ethers BEMF and BEMTHF was proposed., (© 2022 The Authors. ChemSusChem published by Wiley-VCH GmbH.)

Conversion of biomass into biofuels and high value-added chemicals is a promising strategy to solve the increasingly deteriorating environmental problems caused by fossil energy consumption. The development of efficient technologies and methods is the premise and guarantee to realize the high-value conversion of biomass. 5-Hydroxymethylfurfural (HMF), as a versatile biomass platform compound, is generated via dehydration of hexoses (e. g., fructose and glucose) derived from cellulosic biomass. This Review gives an overview of the advances and challenges of electro- and photocatalytic oxidation of biomass-derived HMF to high-value chemicals such as 2,5-formylfuran (DFF) and 2,5-furandicarboxylic acid (FDCA). These strategies and methods for the preparation of high-value chemicals by electro- and photocatalytic oxidation of HMF, coupled with, for example, hydrogen evolution reaction, organic substrate reduction, CO 2 reduction reaction, or N 2 reduction reaction, were summarized and discussed. Moreover, the catalytic efficiency and mechanism of different types of catalysts were also introduced in these conversion systems., (© 2022 Wiley-VCH GmbH.)

2-Hexanol (2-HOL) is a versatile biomass-derived platform molecule for synthesis of liquid transportation fuels, lubricants, or detergents. Herein, a one-step preparation of 2-HOL using 5-hydroxymethylfurfural (HMF) as a substrate was reported for the first time. Several Au-based catalysts supported on different metal oxides were prepared to explore the relationship between carrier and catalytic activity. The results showed that the highest 2-HOL yield of 65.8 % was obtained at complete HMF conversion over the 5 %Au/ZrO 2 catalyst. The 5 %Au/ZrO 2 catalyst exhibited excellent durability after five consecutive recycling runs, while confirming its remarkable ring-opening hydrogenolysis on other biomass-derived furanics, furfural, with a total yield of 1-pentanol and 2-pentanol of 67.4 %. The distinguished ring-opening hydrogenolysis performance of the Au/ZrO 2 catalyst originated from a synergistic effect between the interfacial Au-O-Zr oxygen vacancies-induced Lewis acidic sites (activating C-OH/C=O bonds) and metallic Au (activating H 2 ). This work provides a possibility for producing 2-HOL from HMF with high yield, expanding the sustainable application of lignocellulosic biomass., (© 2022 Wiley-VCH GmbH.)

Catalytic transfer hydrogenation (CTH) with alcohols has been increasingly employed as effective tool for biomass upgrading, however, relying predominantly on secondary alcohols. Herein, for the first time skeletal CuZnAl catalysts were employed for the activation of a primary alcohol, ethanol, for the hydrogenation 5-hydroxymethylfurfual (HMF) to 2,5-bis(hydroxymethyl)furan (BHMF) under a mild condition. The catalysts were extensively characterized to reveal the structure characteristics and surface compositions. Over 90 % yield of BHMF were obtained over the optimal CuZnAl-0.5 catalyst at the reaction temperatures of 100-120 °C. Reaction kinetics indicated a competitive adsorption between HMF and ethanol on the catalyst surface, with the activation of ethanol being the rate-determining step (apparent activation energy E a =70.9 kJ mol -1 ). Preliminary adsorption investigation using combined attenuated total reflectance infrared spectroscopy and density functional theory calculation proposed a η 2 -(O,O)-aldehyde, furoxy perpendicular configuration of HMF on catalyst surface. The catalyst was further applied to the CTH of various aldehydes to the corresponding alcohols with high yields, demonstrating the broad applicability of the current system., (© 2022 Wiley-VCH GmbH.)

The selective conversion of 5-hydroxymethyfurfural (HMF), a biomass-derived platform molecule, to value added chemicals can ease the burden on petroleum-based fine chemical synthesis. The active contribution of renewable energy sources along with low cost, environmental friendliness, and a simple reaction system must be adopted for better sustainability. In this context, photocatalytic selective hydrogenation of HMF to 2,5-bis(hydroxymethyl)furan (BHMF) was achieved over P25 titania nanoparticles without chemical squander. Simultaneously the photo-oxidation of p-methoxybenzyl alcohol (MeOBA) to p-methoxybenzaldehyde (MeOBaL), similar to biomass-derived vanillin, was carried out, abolishing the need of additional redox reagents. This system put forward the competent employment of photogenerated excitons for the valorization of lignocellulosic biomass to fine chemicals, which is an urgent requirement for sustainable chemical synthesis., (© 2022 Wiley-VCH GmbH.)

The selective hydrogenation of 5-hydroxymethylfurfural (HMF) has been of great interest to many scientists and researchers. However, conventional hydrogenation inevitably requires the use of gaseous hydrogen as a reducing agent, which is detrimental to its storage and transport. In this regard, other economical and environmentally friendly strategies, such as catalytic transfer hydrogenation/hydrogenolysis without external molecular H 2 , become more and more attractive. This Review provides the status and insight into the current research of hydrogenating HMF to high-value chemicals, using formic acid, alcohols, polymethylhydrosiloxane, water, and sodium borohydride as hydrogen donors and explains the hydrogenation mechanisms and the related hydrogenation characteristics of different hydrogen donors in the catalytic systems., (© 2022 Wiley-VCH GmbH.)

With increasing concern for reducing CO 2 emission and alleviating fossil resource dependence, catalytic transformation of 5-hydroxymethylfurfural (HMF), a vital platform compound derived from C 6 sugars, holds great promise for producing value-added chemicals. Among several well-established catalytic systems, hydrogenation and oxidation processes have been efficiently adopted for upgrading HMF. This Review covers recent advances in the development of thermocatalytic conversion of HMF into value-added chemicals. The advances of metal-catalyzed hydrogenation, hydrogenolysis, ring-opening, decarbonylation, and oxidation involving selective activation of C-O, C=O, and C=C groups are described. The roles played by nature of metals, supports, additives, synergy of metal-acid sites, and metal-support interaction are also discussed at the molecular level. Finally, an outlook is provided to highlight major challenges associated with this huge research area., (© 2022 Wiley-VCH GmbH.)

Mono- and bimetallic Ni-based catalysts were prepared by screening 6 supports and 14 secondary metals for reductive amination of 5-hydroxymethylfurfural (5-HMF) into 2,5-bis(aminomethyl)furan (BAMF), among which γ-Al 2 O 3 and Mn were the best candidates. By further optimization of the reaction conditions at 0.4 g catalyst loading for 0.5 g substrate of 5-HMF and 160 °C of reaction temperature, 10Ni/γ-Al 2 O 3 and 10NiMn(4 : 1)/γ-Al 2 O 3 achieved the highest BAMF yields of 86.3 and 82.1 %, respectively. Although the BAMF yield values were comparable with that over Raney Ni, the turnover frequencies based on the initial BAMF yield and unit weight of Ni for 10NiMn(4 : 1)/γ-Al 2 O 3 , 10Ni/γ-Al 2 O 3 , and Raney Ni were calculated as 0.41, 0.09, and 0.04 h -1 , respectively. X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy showed that the existence of MnO x well dispersed on the γ-Al 2 O 3 support and its electron transfer effect with Ni particles on the surface of the support contributed to the high efficiency and better recyclability for the five-time reused 10NiMn(4 : 1)/γ-Al 2 O 3 catalyst., (© 2022 Wiley-VCH GmbH.)

5-Hydroxymethylfurfural (HMF) is a promising bio-derived platform chemical with a broad scope of application, for example, in the production of solvents, fuels, polymers, or adhesives. The wood and foundry industries are among the largest adhesive users and currently both rely to a large extent on the use of fossil-based binders, such as by using formaldehyde as a crosslinker in many commercial adhesive systems. The industry is thus looking for suitable alternatives to replace fossil-based chemicals. HMF and its derivatives are considered to be key renewable reactants in adhesive systems. The core of this Review is the critical evaluation of the potential of HMF and its derivatives in adhesive systems. The technological performance was assessed in the fields of wood-based materials, sand casting and composites. As an overall conclusion, HMF and its derivatives have a high application potential in alternative adhesives. Clearly, further research is needed to improve the performance and produce economically competitive adhesives., (© 2020 The Authors. Published by Wiley-VCH GmbH.)

Catalytic strategies were developed to synthesize and release chemicals for applications in fine chemicals, such as drugs and polymers, from a biomass-derived chemical, 5-hydroxymethyl furfural (HMF). The combination of the diene and aldehyde functionalities in HMF enabled catalytic production of acetalized HMF derivatives with diol or epoxy reactants to allow reversible synthesis of norcantharimide derivatives upon Diels-Alder reaction with maleimides. Reverse-conversion of the acetal group to an aldehyde yielded mismatches of the molecular orbitals in norcantharimides to trigger retro Diels-Alder reaction at ambient temperatures and released reactants from the coupled molecules under acidic conditions. These strategies provide for the facile synthesis and controlled release of high-value chemicals., (© 2020 Wiley-VCH GmbH.)

Biobased plasticizers, as substitutes for phthalates, have been synthesized from 5-hydroxymethylfurfural (HMF) and carboxylic acids (or esters) through a chemoenzymatic cascade process that involves as its first step the reduction of 5-hydroxymethylfurfural into 2,5-bis(hydroxymethyl)furan (BHMF), followed by the esterification of BHMF with carboxylic acids (or esters) by using a supported lipase (Novozym 435). The reduction of HMF into BHMF is performed by using monodisperse metallic Co nanoparticles with a thin carbon shell (Co@C) with high activity and selectivity. After optimization of reaction conditions (temperature, hydrogen pressure, and solvent), it is possible to achieve 97 % conversion of HMF with 99 % selectivity to BHMF after 2 h reaction time. The reduction of HMF and esterification of BHMF using carboxylic acids or vinyl esters as acyl donors by lipase are optimized separately in batch and in fixed-bed continuous reactors. The coupling of two flow reactors (for reduction and subsequent esterification) working under optimized reaction conditions affords the diesters of BHMF in roughly 90 % yield with no loss of activity during 60 h of operation., (© 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Furancarboxylic acids are promising biobased building blocks in pharmaceutical and polymer industries. In this work, dual-enzyme cascade systems composed of galactose oxidase (GOase) and alcohol dehydrogenases (ADHs) are constructed for controlled synthesis of 5-formyl-2-furancarboxylic acid (FFCA) and 2,5-furandicarboxylic acid (FDCA) from 5-hydroxymethylfurfural (HMF), based on the catalytic promiscuity of ADHs. The byproduct H 2 O 2 , which is produced in GOase-catalyzed oxidation of HMF to 2,5-diformylfuran (DFF), is used for horseradish peroxidase (HRP)-mediated regeneration of the oxidized nicotinamide cofactors for subsequent oxidation of DFF promoted by an ADH, thus implementing H 2 O 2 internal recycling. The desired products FFCA and FDCA are obtained with yields of more than 95 %., (© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The complete transformation of lignocellulosic biomass into valuable platform chemicals is of great significance. Herein, a catalytic process for the upgrading of lignocellulose to arenes, 5-hydroxymethylfurfural (HMF), and furfural is reported. Firstly, the lignin fraction in lignocellulosic biomass is selectively converted into lignin oil (82.9 mol % yield of lignin monomers from birch wood) over a Pd/C catalyst and then further hydrodeoxygenated to arenes in catalytic hydrogen-transfer reactions over a Ru/Nb 2 O 5 catalyst. High yields of C 7 -C 9 hydrocarbons (95.6 mol %) with 85.6 wt % selectivity to arenes based on lignin oil are achieved owing to the synergistic effect between Ru and Nb 2 O 5 , which enables direct hydrogenolysis of the C aromatic -OH bond in phenolics. Secondly, the cellulose and hemicellulose fractions in the Pd/C-containing solid residue, as well as methylated C 5 sugars produced during the stripping of lignin, are converted into HMF and furfural with a total yield of up to 24.5 wt % (based on the amount of birch wood) in a THF/concentrated seawater (ca. 30 wt % salts) biphasic reaction system. Here, seawater played a key role in the conversion of cellulose and hemicellulose into HMF and furfural, respectively; more importantly, it made the separation and reuse of the Pd/C catalyst easier. With this catalytic process, the complete and efficient transformation of lignocellulose into highly value-added products with recycling of each catalyst and solvent has been realized., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Maleic anhydride (MAnh) and its acids are critical intermediates in chemical industry. The synthesis of maleic anhydride from renewable furfural is one of the most sought after processes in the field of sustainable chemistry. In this study, a plate vanadium phosphorus oxide (VPO) catalyst synthesized by a hydrothermal method with glucose as a green reducing agent catalyzes furfural oxidation to MAnh in the gas phase. The plate catalyst-denoted as VPO HT -has a preferentially exposed (200) crystal plane and exhibited dramatically enhanced activity, selectivity and stability as compared to conventional VPO catalysts and other state-of-the-art catalytic systems. At 360 °C reaction temperature with air as an oxidant, about 90 % yield of MAnh was obtained at 10 vol % of furfural in the feed, a furfural concentration value that is much higher than those (<2 vol %) reported for other catalytic systems. The catalyst showed good long-term stability and there was no decrease in activity or selectivity for MAnh during the time-on-stream of 25 h. The high efficiency and catalyst stability indicate the great potential of this system for the synthesis of maleic anhydride from renewable furfural., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The dissolution of cellulose from biomass is a crucial but complicated issue for maximizing the utilization of biomass resources to produce valuable chemicals, because of the extreme insolubility of cellulose. A biphasic NaCl-H 2 O-tetrahydrofuran (THF) system was studied, in which most of the pure microcrystalline cellulose (M-cellulose, 96.6 % conversion at 220 °C) and that contained in actual biomass were converted. Nearly half of the O6-H⋅⋅⋅O3 intermolecular hydrogen bonds could be broken by THF in the H 2 O-THF co-solvent system, whereas the cleavage of O2-H⋅⋅⋅O6 intramolecular hydrogen bonds by H 2 O was significantly inhibited. In the NaCl-H 2 O-THF system, THF could significantly promote the effects of both H 2 O and NaCl on the disruption of O2-H⋅⋅⋅O6 and O3-H⋅⋅⋅O5 intramolecular hydrogen bonds, respectively. In addition, THF could protect and transfer the cellulose-derived products to the organic phase by forming hydrogen bonds between the oxygen atom in THF and the hydrogen atom of C4-OH in the glucose or aldehyde group in 5-hydroxymethylfurfural (HMF), which can lead more NaCl to combine with the -OH of M-cellulose and further disrupt hydrogen bonding in M-cellulose, thereby improving the yield of small molecular weight products (especially HMF) and further promoting the dissolution of cellulose. As a cheap and reusable system, NaCl-H 2 O-THF system may be a promising approach for the dissolution and further conversion of cellulose in lignocellulosic biomass without any enzymes, ionic liquids, or conventional catalysts., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

An efficient strategy for the conversion of biomass derived 5-hydroxymethylfurfural (HMF) into 2-hydroxy-3-methylcyclopent-2-enone (MCP) by an intramolecular aldol condensation of 1-hydroxyhexane-2,5-dione (HHD) has been developed. Further transformations of MCP towards the diol, enol acetate, levulinic acid and N-heterocyclic compounds are also reported., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A series of highly crystalline, porous, hafnium-based metal-organic frameworks (Hf-MOFs) have been shown to catalyze the transfer hydrogenation reaction of levulinic ester to produce γ-valerolactone by using isopropanol as a hydrogen donor. The results are compared with their zirconium-based counterparts. The role of the metal center in Hf-MOFs has been identified and reaction parameters optimized. NMR studies using isotopically labeled isopropanol provide evidence that the transfer hydrogenation occurs through a direct intermolecular hydrogen transfer route. The catalyst, Hf-MOF-808, can be recycled several times with only a minor decrease in catalytic activity. The generality of the procedure has been demonstrated by accomplishing the transformation with aldehydes, ketones, and α,β-unsaturated carbonyl compounds. The combination of Hf-MOF-808 with the Brønsted-acidic Al-Beta zeolite gives the four-step one-pot transformation of furfural to γ-valerolactone in good yield of 75 %., (© 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

An efficient one-pot catalytic cascade sequence has been developed for the production of value-added ethers from bioderived aldehydes. Etherification of 5-(hydroxymethyl)furfural with different aliphatic alcohols over acidic Zr-montmorillonite (Zr-Mont) catalyst produced a mixture of 5-(alkoxymethyl)furfural and 2-(dialkoxymethyl)-5-(alkoxymethyl)furan. The latter was selectively converted back into 5-(alkoxymethyl)furfural by treating it with water over the same catalyst. The synthesis of 2,5-bis(alkoxymethyl)furan was achieved through a cascade sequence involving etherification, transfer hydrogenation, and re-etherification over a combination of acidic Zr-Mont and the charge-transfer hydrogenation catalyst [ZrO(OH) 2 ]. This catalyst combination was further explored for the cascade conversion of 2-furfuraldehyde into 2-(alkoxymethyl)furan. The scope of this strategy was then extended for the reductive etherification of lignin-derived arylaldehydes to obtain the respective benzyl ethers in >80 % yield. Additionally, the mixture of Zr-Mont and ZrO(OH) 2 does not undergo mutual destruction, which was proved by recycling experiments and XRD analysis. Both the catalysts were thoroughly characterized using BET, temperature-programmed desorption of NH 3 and CO 2 , pyridine-FTIR, XRD, inductively coupled plasma optical emission spectroscopy, and X-ray photoelectron spectroscopy techniques., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The catalytic synthesis of liquid alkanes from renewable biomass has received tremendous attention in recent years. However, bio-based platform chemicals have not to date been exploited for the synthesis of highly branched lubricant alkanes, which are currently produced by hydrocracking and hydroisomerization of long-chain n-paraffins. A selective catalytic synthetic route has been developed for the production of highly branched C 23 alkanes as lubricant base oil components from biomass-derived furfural and acetone through a sequential four-step process, including aldol condensation of furfural with acetone to produce a C 13 double adduct, selective hydrogenation of the adduct to a C 13 ketone, followed by a second condensation of the C 13 ketone with furfural to generate a C 23 aldol adduct, and finally hydrodeoxygenation to give highly branched C 23 alkanes in 50.6 % overall yield from furfural. This work opens a general strategy for the synthesis of high-quality lubricant alkanes from renewable biomass., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Glucose labeled with 13 C or 18 O was used to investigate the mechanism of its conversion into furfural by microwaveassisted pyrolysis. The isotopic content and location in furfural were determined from GC-MS and 13 C NMR spectroscopic measurements and data analysis. The results suggest that the carbon skeleton in furfural is mainly derived from C1 to C5 of glucose, whereas the C of the aldehyde group and the O of the furan ring in furfural primarily originate from C1 and O5 of glucose, respectively. For the first time, the source of O in the furan ring of furfural was elucidated directly by experiment, providing results that are consistent with predictions from recent quantum chemical calculations. Moreover, further theoretical calculations indicate substantially lower energy barriers than previous predictions by considering the potential catalytic effect of formic acid, which is one of the pyrolysis products. The catalytic role of formic acid is further confirmed by experimental evidence., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

In the catalytic conversion of lignocellulose to valuable products, the first entry point is to break down these biopolymers to sugar units or aromatic monomers, which is conventionally achieved by hydrolysis in water medium. Recent years have seen tremendous progress in the alcoholysis process, which has remarkable advantages, such as the avoidance of treating waste water, suppression of humins or chars, and enhancement of reaction rate and product yield. Advances have been focused on the alcoholysis of cellulose, hemicellulose, and lignin to alkyl glucosides, xylosides, and aromatic monomers, respectively. Alcoholysis of the platform molecule furfuryl alcohol (FAL) to alkyl levulinate (AL) and integrated alcoholysis of cellulose and furfural into AL are also summarized. This Minireview highlights the comparisons between alcoholysis and hydrolysis, the reaction mechanism of alcoholysis, and future challenges for industrial applications., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Zeolite L was synthesized by the hydrothermal method and post-treated by NH 4 exchange to adjust its acidity. The samples were systematic characterized by various techniques including XRD, X-ray fluorescence spectroscopy, N 2 adsorption-desorption, scanning electron microscopy, pyridine IR spectroscopy, and NH 3 temperature-programmed desorption. The results demonstrated that the NH 4 -exchange post-treatment increased the surface area, micropore volume, and acidity of zeolite L. The catalytic performance of the samples was tested in the dehydration of fructose to 5-hydroxymethylfurfural (HMF) in ionic liquid (1-butyl-3-methylimidazolium bromide, [bmim]Br). 99.1 % yield of HMF was obtained when the KL-80 °C-1 h sample (KL zeolite treated with 1 m NH 4 NO 3 solution at 80 °C for 1 h) was used. The high efficiency could be attributed to the appropriate acid properties of the catalyst. The zeolite catalyst could be reused four times without significant decrease in activity., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The simultaneous conversion of cyclopentanone and m-cresol has been investigated on a series of solid-acid catalysts. Both compounds are representative of biomass-derived streams. Cyclopentanone can be readily obtained from sugar-derived furfurals through Piancatelli rearrangement under reducing conditions. Cresol represents a family of phenolic compounds, typically obtained from the depolymerization of lignin. In the first biomass conversion strategy proposed here, furfural is converted in high yields and selectivity to cyclopentanone (CPO) over metal catalysts such as Pd-Fe/SiO 2 at 600 psi (∼4.14 MPa) H 2 and 150 °C. Subsequently, CPO and cresol are further converted through acid-catalyzed hydroxyalkylation. This C-C coupling reaction may be used to generate products in the molecular weight range that is appropriate for transportation fuels. As molecules beyond this range may be undesirable for fuel production, a catalyst with a suitable porous structure may be advantageous for controlling the product distribution in the desirable range. If Amberlyst resins were used as a catalyst, C 12 -C 24 products were obtained whereas when zeolites with smaller pore sizes were used, they selectively produced C 10 products. Alternatively, CPO can undergo the acid-catalyzed self-aldol condensation to form C 10 bicyclic adducts. As an illustration of the potential for practical implementation of this strategy for biofuel production, the long-chain oxygenates obtained from hydroxyalkylation/aldol condensation were successfully upgraded through hydrodeoxygenation to a mixture of linear alkanes and saturated cyclic hydrocarbons, which in practice would be direct drop-in components for transportation fuels. Aqueous acidic environments, which are typically encountered during the liquid-phase upgrading of bio-oils, would inhibit the efficiency of base-catalyzed processes. Therefore, the proposed acid-catalyzed upgrading strategy is advantageous for biomass conversion in terms of process simplicity., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

This work provided the first example of selective hydrodeoxygenation of 5-hydroxymethylfurfural (HMF) to 2,5-dimethylfuran (DMF) over heterogeneous Fe catalysts. A catalyst prepared by the pyrolysis of an Fe-phenanthroline complex on activated carbon at 800 °C was demonstrated to be the most active heterogeneous Fe catalyst. Under the optimal reaction conditions, complete conversion of HMF was achieved with 86.2 % selectivity to DMF. The reaction pathway was investigated thoroughly, and the hydrogenation of the C=O bond in HMF was demonstrated to be the rate-determining step during the hydrodeoxygenation, which could be accelerated greatly by using alcohol solvents as additional H-donors. The excellent stability of the Fe catalyst, which was probably a result of the well-preserved active species and the pore structure of the Fe catalyst in the presence of H 2 , was demonstrated in batch and continuous flow fixed-bed reactors., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A process for the synthesis of 1,5-pentanediol (1,5-PD) with 84 % yield from furfural is developed, utilizing dehydration/hydration, ring-opening tautomerization, and hydrogenation reactions. Although this process has more reaction steps than the traditional direct hydrogenolysis of tetrahydrofurfuryl alcohol (THFA), techno-economic analyses demonstrate that this process is the economically preferred route for the synthesis of biorenewable 1,5-PD. 2-Hydroxytetrahydropyran (2-HY-THP) is the key reaction pathway intermediate that allows for a decrease in the minimum selling price of 1,5-PD. The reactivity of 2-HY-THP is 80 times greater than that of THFA over a bimetallic hydrogenolysis catalyst. This enhanced reactivity is a result of the ring-opening tautomerization to 5-hydoxyvaleraldehyde and subsequent hydrogenation to 1,5-PD., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Copper species have been incorporated in mesoporous silica (MS) through complexation with the amine groups of dodecylamine, which was used as a structure-directing agent in the synthesis. A series of Cu/SiO 2 catalysts (xCu-MS) with copper loadings (x) from 2.5 to 20 wt % was synthesized and evaluated in the gas-phase hydrogenation of furfural (FUR). The most suitable catalytic performance in terms of 2-methylfuran yield was obtained with an intermediate copper content (10 wt %). This 10Cu-MS catalyst exhibits a 2-methylfuran yield higher than 95 mol % after 5 h time-on-stream (TOS) at a reaction temperature of 210 °C with a H 2 /FUR molar ratio of 11.5 and a weight hourly space velocity (WHSV) of 1.5 h -1 . After 14 h TOS, this catalyst still showed a yield of 80 mol %. In all cases, carbonaceous deposits on the external surface were the cause of the catalyst deactivation, although sintering of the copper particles was observed for higher copper loadings. This intermediate copper loading (10 wt %) offered a suitable balance between resistance to sintering and tendency to form carbonaceous deposits., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A simple non-precious-metal catalyst system based on costeffective and ubiquitously available MnO 2 , NaHCO 3 , and molecular oxygen was used to convert 5-hydroxymethylfurfural (HMF) to 2,5-difurandicarboxylic acid (FDCA) as a bioplastics precursor in 91 % yield. The MnO 2 catalyst could be recovered by simple filtration and reused several times. The present system was also applicable to the aerobic oxidation of other biomass-derived substrates and the gram-scale oxidation of HMF to FDCA, in which 2.36 g (86 % yield) of the analytically pure FDCA could be isolated., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A one-pot method for the selective production of high-grade diesel-range alkanes from biomass-derived furfural and 2-methylfuran (2-MF) was developed by combining the hydroxyalkylation/alkylation (HAA) condensation of furfural with 2-MF and the subsequent hydrodeoxygenation (HDO) over a multifunctional Pd/NbOPO 4 catalyst. The effects of various reaction conditions as well as a variety of solid-acid catalysts and metal-loaded NbOPO 4 catalysts were systematically investigated to optimize the reaction conditions for both reactions. Under the optimal reaction conditions up to 89.1 % total yield of diesel-range alkanes was obtained from furfural and 2-MF by this one-pot method., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

A series of renewable C 9 -C 12 triketones with repeating [COCH 2 CH 2 ] units were synthesized in high carbon yields (ca. 90 %) by the aqueous-phase hydrogenation of the aldol-condensation products of 5-hydroxylmethylfurfural (HMF) and ketones over an Au/TiO 2 catalyst. Compared with the reported routes, this new route has many advantages such as being environmentally friendly, having fewer steps, using a cheaper and reusable catalyst, etc. The triketones as obtained can be used as feedstocks in the production of conducting or semi-conducting polymers. Through a solvent-free intramolecular aldol condensation over solid-base catalysts, the triketones were selectively converted to diketones, which can be used as intermediates in the synthesis of useful chemicals or polymers. As another application, the tri- and diketones can also be utilized as precursors for the synthesis of jet-fuel range branched cycloalkanes with low freezing points (224-248 K) and high densities (ca. 0.81 g mL -1 )., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The selective transformation of 5-hydroxymethylfurfural (HMF) to valuable 2,5-diformylfuran (DFF) and 2,5-dihydroxymethylfuran (DHMF) is highly desirable but remains a great challenge owing to its tendency to over-oxidation and over-reduction. In this work, HMF is directly converted into DFF and DHMF without external oxidant or reductant through a Meerwein-Ponndorf-Verley-Oppenauer (MPVO) reaction. In such a MPVO process, HMF is used as both oxidant and reductant and DFF and DHMF are simultaneously produced with a 1:1 molar ratio in the presence of a Lewis acid catalyst. Under high initial HMF concentration, a HMF conversion of up to 44.7 % can be reached within 1 h. Moreover, this atom-efficient transformation route for HMF also provides a promising protocol for the crude separation of DHMF products from DFF products, owing to the lower solubility of DHMF compared to DFF in acetonitrile., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Catalytic oxidation of alcohols often requires the presence of expensive transition metals. Herein, it is shown that earth-abundant Fe atoms dispersed throughout a nitrogen-containing carbon matrix catalyze the oxidation of benzyl alcohol and 5-hydroxymethylfurfural by O 2 in the aqueous phase. The activity of the catalyst can be regenerated by a mild treatment in H 2 . An observed kinetic isotope effect indicates that β-H elimination from the alcohol is the kinetically relevant step in the mechanism, which can be accelerated by substituting Fe with Cu. Dispersed Cr, Co, and Ni also convert alcohols, demonstrating the general utility of metal-nitrogen-carbon materials for alcohol oxidation catalysis. Oxidation of aliphatic alcohols is substantially slower than that of aromatic alcohols, but addition of 2,2,6,6-tetramethyl-1-piperidinyloxy as a co-catalyst with Fe can significantly improve the reaction rate., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We studied the acid-catalyzed isomerization of levoglucosenone (LGO) to 5-hydroxymethylfurfural (HMF) and developed a reaction kinetics model that describes the experimental data across a range of conditions (100-150 °C, 50-100 mm H 2 SO 4 , 50-150 mm LGO). LGO and its hydrated derivative exist in equilibrium under these reaction conditions. Thermal and catalytic degradation of HMF are the major sources of carbon loss. Within the range of conditions studied, higher temperatures and shorter reaction times favor the production of HMF. The yields of HMF and levulinic acid decrease monotonically as tetrahydrofuran is added to the aqueous solvent system, indicating that water plays a role in the LGO isomerization reaction. Initial-rate analyses show that HMF is produced solely from LGO rather than from the hydrated derivative of LGO. The results of this study are consistent with a mechanism for LGO isomerization that proceeds through hydration of the anhydro bridge, followed by ring rearrangement analogous to the isomerization of glucose to fructose., (© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Decarbonylation of furfural to furan was efficiently catalyzed by ZrO 2 -supported Pd clusters in the liquid phase under a N 2 atmosphere without additives. Although Pd/C and Pd/Al 2 O 3 have frequently been used for decarbonylation, Pd/ZrO 2 exhibited superior catalytic performance compared with these conventional catalysts. Transmission electron microscopy and X-ray absorption fine structure measurements revealed that the size of the Pd particles decreased with an increase in the specific surface area of ZrO 2 . ZrO 2 with a high surface area immobilized Pd as clusters consisting of several (three to five) Pd atoms, whereas Pd aggregated to form nanoparticles on other supports such as carbon and Al 2 O 3 despite their high surface areas. The catalytic activity of Pd/ZrO 2 was enhanced with a decrease in particle size, and the smallest Pd/ZrO 2 was the most active catalyst for decarbonylation. When CeO 2 was used as the support, a decrease in Pd particle size with an increase in surface area was also observed. Single Pd atoms were deposited on CeO 2 with a high surface area, with a strong interaction through the formation of a Pd-O-Ce bond, which led to a lower catalytic activity than that of Pd/ZrO 2 . This result suggests that zero-valent small Pd clusters consisting of more than one Pd atom are the active species for the decarbonylation reaction. Recycling tests proved that Pd/ZrO 2 maintained its catalytic activity until its sixth use., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Green, inexpensive, and robust copper-based heterogeneous catalysts achieve 100 % conversion and 99 % selectivity in the conversion of furfural to furfuryl alcohol when using cyclopentyl-methyl ether as green solvent and microwave reactors at low H 2 pressures and mild temperatures. The utilization of pressurized microwave reactors produces a 3-4 fold increase in conversion and an unexpected enhancement in selectivity as compared to the reaction carried out at the same conditions using conventional autoclave reactors. The enhancement in catalytic rate produced by microwave irradiation is temperature dependent. This work highlights that using microwave irradiation in the catalytic hydrogenation of biomass-derived compounds is a very strong tool for biomass upgrade that offers immense potential in a large number of transformations where it could be a determining factor for commercial exploitation., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The catalytic transfer hydrogenation of furfural to the fuel additives 2-methylfuran (2-MF) and 2-methyltetrahydrofuran (2-MTHF) was investigated over various bimetallic catalysts in the presence of the hydrogen donor 2-propanol. Of all the as-prepared catalysts, bimetallic Cu-Pd catalysts showed the highest catalytic activities towards the formation of 2-MF and 2-MTHF with a total yield of up to 83.9 % yield at 220 °C in 4 h. By modifying the Pd ratios in the Cu-Pd catalyst, 2-MF or 2-MTHF could be obtained selectively as the prevailing product. The other reaction conditions also had a great influence on the product distribution. Mechanistic studies by reaction monitoring and intermediate conversion revealed that the reaction proceeded mainly through the hydrogenation of furfural to furfuryl alcohol, which was followed by deoxygenation to 2-MF in parallel to deoxygenation/ring hydrogenation to 2-MTHF. Finally, the catalyst showed a high reactivity and stability in five catalyst recycling runs, which represents a significant step forward toward the catalytic transfer hydrogenation of furfural., (© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Dehydration of glucose to 5-hydroxymethylfurfural (HMF) remains a significant problem in the context of the valorization of lignocellulosic biomass. Hydrolysis of WCl6 and NbCl5 leads to precipitation of Nb-containing tungstite (WO3 ⋅H2 O) at low Nb content and mixtures of tungstite and niobic acid at higher Nb content. Tungstite is a promising catalyst for the dehydration of glucose to HMF. Compared with Nb2 O5 , fewer by-products are formed because of the low Brønsted acidity of the (mixed) oxides. In water, an optimum yield of HMF was obtained for Nb-W oxides with low Nb content owing to balanced Lewis and Brønsted acidity. In THF/water, the strong Lewis acidity and weak Brønsted acidity caused the reaction to proceed through isomerization to fructose and dehydration of fructose to a partially dehydrated intermediate, which was identified by LC-ESI-MS. The addition of HCl to the reaction mixture resulted in rapid dehydration of this intermediate to HMF. The HMF yield obtained in this way was approximately 56 % for all tungstite catalysts. Density functional theory calculations show that the Lewis acid centers on the tungstite surface can isomerize glucose into fructose. Substitution of W by Nb lowers the overall activation barrier for glucose isomerization by stabilizing the deprotonated glucose adsorbate., (© 2016 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)