A high 5-hydroxymethylfurfural (HMF) yield of 53 mol% was obtained by direct degradation of cellulose in a biphasic system with concentrated NaHSO 4 and ZnSO 4 as co-catalysts, with 96% of cellulose conversion in 60 min. The high concentration of catalysts in the aqueous solution and the high volume ratio of organic phase to aqueous phase were responsible for the excellent performance. The depolymerization of cellulose is the rate-determine step, and the formed glucose could be efficiently converted by concentrated catalysts in the aqueous solution, leading to low concentration of glucose in the solution and thus suppressing the side reactions such as humin and char formation. † Electronic supplementary information (ESI) available. See

The rapid development of materials science now enables tailoring of metal and metal oxide particles with tunable size and shape at the nanometre level. As a result, nanocatalysis is undergoing an explosive growth, and it has been seen that the size and shape of a catalyst particle tremendously affects the reaction performance. The size effect of metal nanoparticles has been interpreted in terms of the variation in geometric and electronic properties that governs the adsorption and activation of the reactants as well as the desorption of the products. At the same time, it has been verified that the morphology of a catalyst particle, determined by the exposed crystal planes, also considerably affects the catalytic behavior. This is termed as morphology-dependent nanocatalysis: a catalyst particle with an anisotropic shape alters the reaction performance by selectively exposing specific crystal facets. This perspective article initially surveys the recent progress on morphology-dependent nanocatalysis of precious metal particles to emphasise the chemical nature of the morphology effect. Then, the fabrication of transition metal particles with controllable size/morphology is examined, and their shape is correlated with their catalytic properties, with the aim to clarify the structure-reactivity relationship. Finally, the future outlook presents our personal perspectives on the concept of morphology-dependent nanocatalysis of metal particles, which is a rapidly growing topic in heterogeneous catalysis.

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Catalytic hydrodeoxygenation (HDO) of vegetable oils to renewable alkane-type biofuels has attracted more and more concern in recent years. However, the presently used catalysts were mainly focused on the sulfided CoMo and NiMo catalysts, which inevitably posed sulfur contamination in final products. Therefore, exploring nonsulfured catalyst for this processing is of fundamental importance, but it is still an open challenge. In this paper, we prepared the sulfur free Ni supported on SiO 2 , γ-Al 2 O 3 , SAPO-11, HZSM-5, and HY by incipient wetness impregnation and tested the catalytic performance in HDO of methyl palmitate. Alkanes with long carbon chains were mainly produced with two possibly parallel approaches: hydrogenation of hexadecanal to hexadecanol, followed by dehydration/hydrogenation to C 16 alkane and decarbonylaton/ decarboxylation of hexadecanoic acid to C 15 alkane. The acidity of catalysts significantly influenced their catalytic performance, and the Ni/SAPO-11 catalysts with weak and medium acidity showed superior properties to the other catalysts due to the synergistic effect of metal Ni and acidic support. The maximum yield of 93% for C 15+ alkanes was observed over 7 wt % Ni/ SAPO-11 under the mild reaction conditions of 493 K and 2 MPa, indicating its promising application in this reaction.

Catalytic hydrothermal conversion of carbohydrates could provide a series of versatile valuable platform chemicals, but the formation of solid humins greatly decreased the efficiency of the process. Herein, by studying the hydrothermal degradation behavior and analyzing the degradation paths of kinds of model compounds including carbohydrates, furan compounds, cyclic ketone derivatives, and some simple short carbon-chain oxy-organics, we demonstrate that α-carbonyl aldehydes and α-carbonyl acids are the key primary precursors for humin formation during the hydrothermal conversion process. Then, we analyzed the hydrothermal degradation paths of two simple α-carbonyl aldehydes including glyoxal and pyruvaldehyde and found that the α-carbonyl aldehydes could undergo aldol condensation followed by acetal cyclization and dehydration to form solid humins rich of furan ring structure or undergo Cannizaro route (hydration followed by 1,2-hydride shift) to form corresponding α-hydroxy acids. On the basis of the hydrothermal behavior of the α-carbonyl aldehydes, we mapped the hydrothermal degradation routes of carbohydrates (glucose, fructose, and xylose) and illuminated the formation details of α-carbonyl aldehydes, α-hydroxy acids, γ-lactones, furfural derivatives, and humins. Finally, we deduced the typical structure fragments of humins from three α-carbonyl aldehydes of pyruvaldehyde, 2,5-dioxo-6-hydroxy-hexanal, and 3-deoxyglucosone, all of which could be formed during the hydrothermal degradation of hexose.

Selective hydrogenation of 5-hydroxymethylfurfural (HMF) has potential application in high quality biofuels.Herein, the catalytic hydrodeoxygenation (HDO) of HMF to 2,5-dimethylfuran (DMF) was investigated using bi-functional Ru-MoO x /C catalyst prepared by initial wetness impregnation. The high dispersion and electronic transfer between Ru and MoO x were demonstrated by a series of characterization techniques.During this HDO process, the synergy effect between metallic Ru and acidic MoO x species in the RuMoO x /C catalyst plays an essential role in obtaining maximized target product DMF (79.4%) via effective aldehyde group hydrogenation by Ru followed by dehydration over MoO x . This work also elucidated that DMF production proceeded through two distinct pathways: the 2,5-hydroxymethyl furan intermediate was preferable by the aldehyde group hydrogenation of HMF over the Ru-MoO x /C catalyst. Over MoO x / C catalyst, comparatively, 5-methyl furfural was the key intermediate by direct hydrogenolysis of the hydroxyl group in HMF. This kind of catalyst is stable for the first two runs by maintaining the target product yield. After the third run, the catalyst showed deactivation gradually but could be almost completely recovered after regeneration by H 2 reduction.

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Hydrochars are solid byproducts formed during the liquid-phase biorefinery process and could be used to generate functional carbonaceous materials, but the detailed molecular structure and the formation mechanism are still unclear. Herein, the formation of hydrochars from liquid-phase carbonization of biomass-derived compounds including glucose, fructose, xylose, ribose, dihydroxyacetone (DHA), 5-hydroxymethylfurfural (HMF), furfural (FF), and pyruvaldehyde (PRV) in water and inert polar organic solvents ethyl acetate (EAC) and tetrahydrofuran (THF) was studied. The carbohydrates were found to generate hydrochars in both water and the organic solvents, while the HMF and FF could generate hydrochars only in water. The α-carbonyl aldehydes, including PRV, 3-deoxyglucosone, and 2,5-dioxo-6-hydroxyhexanal (DHH), formed during the decomposition of carbohydrates were proposed to be the key primary precursors for hydrochar formation. The molecular structures of the hydrochars were characterized by elemental analysis, Fourier transform infrared analysis, and solid-state 13C NMR analysis to confirm that the molecular formula of the hydrochars all could be approximately expressed as (C3H2O) n , and the molecular structures of the hydrochars all consisted of polyaromatic hydrocarbon, phenolic, furanic, and aliphatic framents and a small amount of carbonyl/carboxyl groups. The presence of the polyaromatic hydrocarbon and phenolic fragments in the hydrochars suggested that aldol condensation played a critical role for hydrochar formation. By regarding the aldol condensation of α-carbonyl aldehydes as the initial step for hydrochar formation, we deduced the polymerization routes of these α-carbonyl aldehydes and found that the α-carbonyl aldehydes all could undergo aldol condensation followed by acetal cyclization and etherification to form polymers (C3H2O) n rich in furanic framework or undergo aldol condensation followed by a 1,2-hydride shift, intramolecular aldol condensation, and dehydration to generate polymers (C3H2O) n rich in the phenolic framework. One molecular structure containing polyaromatic hydrocarbon, phenolic, furanic, and aliphatic fragments is proposed for the hydrochars.