5-羟甲基糠醛热解机理的PY-GC-MS及原位红外法分析

采用PY-GC-MS（快速热裂解-色质联用）对5-羟甲基糠醛（5-HMF）进行热裂解实验，发现裂解产物中将近86％为呋喃环类物质，同时存在小分子物质，表明其热解主要为侧链降解，但也存在呋喃环的开环断裂．结合原位红外光谱分析，实时监测5-HMF热裂解产物随反应过程的转化规律，发现在130～230℃之间主要生成糠醛、5-甲基糠醛，250qC后主要生成2．糠醇及5-乙酰甲氧基．2．糠醛，这两者的生成持续至反应中后期；作为5．HMF热解最主要产物的2，5-呋喃二甲醛的生成则在整个反应过程持续进行．结合快速热解及原位红外实验结果，推测5-HMF的热解机理如下：侧链羟甲基处连续两次脱氢生成2，5-呋喃二甲醛是最主要的反应，羟甲基去羟基后加氢生成5-甲基糠醛，羟甲基侧链及醛基侧链的整体断裂分别生成糠醛及糠醇，在此基础上还会发生二次裂解反应生成2-甲基呋喃．

中药与食品中共性成分5-羟甲基-2-糠醛的生物活性及其安全性研究进展

5-羟甲基-2-糠醛(5-hydroxymethyl-2-furfural,5-HMF)作为一种生物活性物质,是药品和食品中存在较为广泛的共性成分,对其深入研究有利于阐释药品的作用、食品的功能,对提高药品、食品的安全性具有重要意义。5-HMF在发挥生物活性作用的同时,也存在安全性隐患,且不良反应的显现与其浓度含量相关。本文对5-HMF的生物活性及其安全性研究进展进行综述,整理分析5-HMF的形成及其影响因素、生物活性和安全性等相关文献,总结该共性成分在药品和食品中的作用及其对产品质量的影响,为提高药品与食品的有效性和安全性提供参考。

Realizing efficient electrochemical oxidation of 5-hydroxymethylfurfural on a freestanding Ni(OH)_(2)/nickel foam catalyst

With the continuous improvement of solar energy production capacity,how to effectively use the electricity generated by renewable solar energy for electrochemical conversion of biomass is a hot topic.Electrochemical conversion of 5-hydroxymethylfurfural(HMF)to biofuels and value-added oxygenated commodity chemicals provides a promising and alternative pathway to convert re-newable electricity into chemicals.Although nickel-based eletrocatalysts are well-known for HMF oxidation,their relatively low intrinsic activity,poor conductivity and stability still limit the poten-tial applications.Here,we report the fabrication of a freestanding nickel-based electrode,in which Ni(OH)_(2) species were in-situ constructed on Ni foam(NF)support using a facile ac-id-corrosion-induced strategy.The Ni(OH)2/NF electrocatalyst exhibits stable and efficient electro-chemical HMF oxidation into 2,5-furandicarboxylic acid(FDCA)with HMF conversion close to 100% with high Faraday efficiency.In-situ formation strategy results in a compact interface between Ni(OH)_(2) and NF,which contributes to good conductivity and stability during electrochemical reac-tions.The superior performance benefits from dynamic cyclic evolution of Ni(OH)_(2) to NiOOH,which acts as the reactive species for HMF oxidation to FDCA.A scaled-up device based on a continu-ous-flow electrolytic cell was also established,giving stable operation with a high FDCA production rate of 27 mg h^(-1)cm^(−2).This job offers a straightforward,economical,and scalable design strategy to design efficient and durable catalysts for electrochemical conversion of valuable chemicals.

Efficient production of 5-hydroxymethylfurfural from hexoses using solid acid SO_4^(2-)/In_2O_3-ATP in a biphasic system

A natural attapulgite （ATP）‐based catalyst, sulfated In2O3‐ATP （SO42-/In2O3‐ATP）, was obtained by an impregnation‐calcination method and was used to efficiently and selectively produce the useful platform chemical 5‐hydroxymethylfurfural （HMF） from hexoses. Some important reaction param‐eters were studied, revealing that Lewis and Br-nsted acid sites on SO42-/In2O3‐ATP catalyze glu‐cose isomerization and fructose dehydration. The yields of HMF from glucose and fructose were 40.2%and 46.2%, respectively, using the optimal conditions of 180℃ for 60 min with 10 wt%of solid acid catalyst in a mixture of γ‐valerolactone‐water （9：1）.

Conversion of Cellulose to 5-Hydroxymethylfurfural in Water- Tetrahydrofuran and Byproducts Identification

Conversion of cellulose into platform chemical 5-hydroxymethylfurfural （HMF） in water-tetrahydrofuran （THF） co-solvents under acidic condition was studied. 38.6% of HMF was obtained with low cellulose concentration of 2.4wt%, but levulinic acid （LA） and solid humins became the main products with high cellulose concentration. The soluble byproducts were analyzed by high performance liquid chromatography/multiple stage tandem mass spec-trometry, and chemicals with formula of C9H16O4、 C10H14O4、 C11H12O4、C12H10O5 and C12H16O8 were detected. THF could participate in the reaction via ring-opening into 1,4-butanediol followed by esterification with LA into C9H16O4 or etherification with HMF into C10H14O4. C11H12O4 was formed by esterification of HMF with LA, C12H10O5 was formed by self-etherification of HMF, while C12H16O8 was formed by acetalization of HMF with glucose. Self-etherification of HMF and etherification of HMF with 1,4-butanediol were identified as two main side reactions.

Preparation of 5-Hydroxymethylfurfural from Cellulose via Fast Depolymerization and Consecutively Catalytic Conversion

The conversion of cellulose to 5-hydroxymethylfurfural （HMF） has been investigated by a one-pot consecutive reaction. At first, cellulose was depolymerised into glucose via a fast degradation of cellulose in molten ZnCI~ in the presence of hydrochloric acid, and the yield of glucose is 75% in 120 s at reaction temperature of 95 ℃. Then, DMSO was used as solvent and different kinds of metal chloride were added as catalysts, and the conversion was carried out continuously at 110-130 ℃ for 0.5-4 h. The yield of HMF was 53% when CrC13 were used as catalyst. The one-pot two steps conversion was carried out at atmosphere pressure, and it is a simple route to prepare HMF from lignocellulosic feedstock on a large scale.

Influence of supports for selective production of 2,5-dimethylfuran via bimetallic copper-cobalt catalyzed 5-hydroxymethylfurfural hydrogenolysis

The hydrogenolysis of carbon–oxygen bonds is an important model reaction in upgrading biomass‐derived furanic compounds to transportation fuels.One of these model reactions,namelyconversion of5‐hydroxymethylfurfural(HMF)to the gasoline additive2,5‐dimethylfuran(DMF),isespecially attractive.In this study,bimetallic Cu‐Co catalysts supported on CeO2,ZrO2,and Al2O3were used for the selective hydrogenolysis of HMF to DMF.The structures of the fresh and usedcatalysts were studied using X‐ray diffraction,the Brunauer‐Emmett‐Teller method,transmissionelectron microscopy,temperature‐programmed reduction by H2,temperature‐programmed desorptionof NH3,and CHNS analysis.The structures were correlated with the catalytic activities.TheCu‐Co/CeO2catalyst produced mainly2,5‐bis(hydroxymethyl)furan via reduction of C=O bonds onlarge Cu particles.The Cu‐Co/Al2O3catalyst gave the best selectivity for DMF,as a result of a combinationof highly dispersed Cu,mixed copper–cobalt oxides,and suitable weak acidic sites.Cu‐Co/ZrO2had low selectivity for DMF and produced a combination of variousover‐hydrogenolysis products,including2,5‐dimethyltetrahydrofuran and5,5‐oxybis(methylene)‐bis(2‐methylfuran),because of the presence of strong acidic sites.The reaction pathways and effectsof various operating parameters,namely temperature,H2pressure,and time,were studied to enableoptimization of the selective conversion of HMF to DMF over the Cu‐Co/Al2O3catalyst.

Enhanced HMF yield from glucose with H-ZSM-5 catalyst in water–tetrahydrofuran/2-butanol/2-methyltetrahydrofuran biphasic systems

With the aim of achieving a high 5-hydroxymethylfurfural(HMF)yield from glucose with H-ZSM-5 catalyst at low cost,three inexpensive biphasic reaction systems,H2O?tetrahydrofuran(THF),H2O?2-methyltetrahydrofuran(MeTHF)and H2O?2-butanol,were discovered and proved to be particularly effective in promoting the formation of HMF from glucose over H-ZSM-5 zeolite.In order to determine the optimal process conditions,the effects of various experimental variables,such as reaction temperature,reaction time,catalyst dosage,volume of organic solvent,as well as inorganic salt type on glucose conversion to HMF in three systems were investigated in detail.It was found that under optimal reaction conditions,H2O?THF,H2O?2-butanol and H2O?MeTHF allowed the glucose dehydration process to achieve HMF yields of up to 61%,59%,and 50%,respectively.Moreover,in the three biphasic systems,the H-ZSM-5 catalyst was also demonstrated to maintain excellent stability.Thus,the catalytic approach proposed in this paper can be believed to have potential prospects for industrially efficient and low-cost production of HMF.

Decomposition of Cellulose to Produce 5-Hydroxymethyl-Furaldehyde in Subcritical Water

A method for decomposition of cellulose to produce 5-hydroxymethyl-furaldehyde （5- HMF） in subcritical water-carbon dioxide binary system was proposed. A series of experiments were performed in a batch reaction vessel. Main products of the decomposition of cellulose are 5-HMF, furfural, levulinic acid and 1, 2, 4-benzenetrioI.The optimum condition for the preparation of 5-HMF was found as 523.15 K, 5.0% carbon dioxide mole fraction, and 30 min reaction time. The addition of carbon dioxide to water conduced to the decomposition of cellulose to 5-HMF. As can be seen from the distribution of the prod-ucts, the decomposition mechanism of cellulose is similar to the hydrothermal reaction of D-glucose and D-fructose.

Sustainable synthesis of 5-hydroxymethylfurfural from waste cotton stalk catalyzed by solid superacid-SO4^2-/ZrO2

A sustainable process was explored for the preparation of 5-hydroxymethylfurfural(HMF) by catalytic degradation of the waste cotton stalk. Solid super-acid(SO_4^(2-)/ZrO_2) was used as an efficient catalyst for the degradation of cotton stalk. Both decomposition experiments and kinetic study were conducted for the exploration of degradation condition and kinetics mechanism. The optimized experimental conditions are reaction temperature 503 K, reaction time 75 min and dosage of catalyst 30%(mass fraction) based on the decomposition experiments, under which a maximum yield of 27.2% for HMF could be achieved. Kinetic study was then carried out in the presence of SO_4^(2-)/ZrO_2. The theoretical results indicate that the activation energies for reducing sugar and HMF with catalyst are 96.71 k J/mol, 84.21 kJ/mol in the presence of SO_4^(2-)/ZrO_2, and they are 105.96 k J/mol and 119.37 k J/mol in the absence of SO_4^(2-)/ZrO_2.

Dehydration of sugars to 5-hydroxymethylfurfural and non-stoichiometric formic and levulinic acids over mesoporous Ta and Ta-W oxide solid acid catalysts

A series of mesoporous Ta and Ta-W oxides have been prepared and employed as solid acid catalysts for the dehydration of fructose and glucose to 5-hydroxymethylfurfural(HMF).Solid state 31 P MAS NMR spectroscopic results using trimethylphosphine(TMP)as a probe molecule show that the acid strength and the ratio of Br?nsted to Lewis acid sites increase gradually with the addition of tungsten in tantalum oxide.It is found that high sugar conversion and HMF selectivity are achieved over catalyst with relatively high ratios of Br?nsted to Lewis acid sites.Unexpected stoichiometric excess of formic acid relative to levulinic acid can be observed mainly because of direct decomposition of fructose over Lewis acid sites.The addition of 2-butanol leads to the increase of sugars conversion and the HMF selectivity,especially for the catalyst with high ratio of Br?nsted to Lewis acid sites.Among them,Ta7W3 oxide catalyst shows 54%HMF selectivity and good reusability with the addition of 2-butanol by extracting HMF from aqueous phase and removing humins deposed on the surface of the catalyst.

N-doped carbon layer-coated Au nanocatalyst for H_(2)-free conversion of 5-hydroxymethylfurfural to 5-methylfurfural

Deoxygenative upgrading of 5-hydromethylfurfural(HMF)into valuable chemicals has attracted intensive research interest in recent years,with product selectivity control remaining an important topic.Herein,TiO_(2) supported gold catalysts coated with a thin N-doped porous carbon(NPC)layer were developed via a polydopamine-coating-carbonization strategy and utilized for pathway-specific conversion of HMF into 5-methylfurfural(5-MF)with the use of renewable formic acid(FA)as the deoxygenation reagent.The as-fabricated Au/TiO_(2)@NPC exhibited excellent catalytic performance with a high yield of 5-MF(>95%).The catalytic behavior of Au@NPC-based catalysts was shown to be correlated with the suitable combination of highly dispersed Au nanoparticles and favorable interfacial interactions in the Au@NPC core-shell hetero-nanoarchitectures,thereby facilitating the preferential esterification of HMF with FA and suppressing unproductive FA dehydrogenation,which promoted the selective formylation/decarboxylation of hydroxy-methyl group in HMF in a pathway-specific manner.The present NPC/metal interfacial engineering strategy may provide a potential guide for the rational design of advanced catalysts for a wide variety of heterogeneous catalysis processes in terms of the conversion of biomass source.

Oxidation of 2,5‐bis(hydroxymethyl)furan to 2,5‐furandicarboxylic acid catalyzed by carbon nanotube‐supported Pd catalysts

The selective oxidation of 2,5‐bis(hydroxymethyl)furan(BHMF)in this work was proven as a promising route to produce 2,5‐furandicarboxylic acid(FDCA),an emerging bio‐based building‐block with wide application.Under ambient pressure,the modified carbon nanotube‐supported Pd‐based catalysts demonstrate the maximum FDCA yield of 93.0%with a full conversion of BHMF after 60 min at 60°C,much superior to that of the traditional route using 5‐hydroxymethylfurfural(HMF)as substrates(only a yield of 35.7%).The participation of PdH_(x) active species with metallic Pd can be responsible for the encouraging performance.Meanwhile,a possible reaction pathway proceeding through 2,5‐diformylfuran(DFF)and 5‐formyl‐2‐furancarboxylic acid(FFCA)as process intermediates is suggested for BHMF route.The present work may provide new opportunities to synthesize other high value‐added oxygenates by using BHMF as an alternative feedstock.

Effect of 5-HMF on protection of hydrogen peroxide-induced injury in human umbilical vein endothelial cells

The protective effect of 5-hydroxymethylfurfural（5-HMF） against hydrogen peroxide（H2O2）-induced injured in human umbilical vein endothelial cells（HUVECs） was examined. Treatment of HUVECs with 5-HMF significantly increased their viability, decreased cell apoptosis induced by H2O2, accompanied by the decreased nitric oxide level. Western blotting analysis demonstrated that Bcl-2 expression was increased whereas Caspase-3 and NF-κB expression was decreased in 5-HMF groups. In conclusion, the results showed that 5-HMF could prevent endothelial dysfunction and related complications caused by oxidative stress.

BMP/Smad信号途径相关基因在5-HMF诱导骨髓间充质干细胞成骨分化中表达

目的研究5-羟甲基-2-糠醛(5-HMF)诱导大鼠骨髓间充质干细胞(BMSCs)成骨分化时骨形成蛋白(BMP)/Smads信号途径相关基因的表达变化。方法体外培养大鼠BMSCs,用5-HMF10μmol/L诱导BMSCs成骨分化0、10、24、48h(诱导早期)和7d(诱导晚期)。采用荧光定量PCR检测BMP2、骨形成蛋白受体1A(BMPR1A)、BMPR1B、BMPR2、Smad1、Smad4、Smad5、Smad9、Osx和Runx2的表达。结果与0h组相比,诱导早期的BMPR1A、BMPR1B、Smad1、Smad4、Smad5表达均未发生明显变化(P>0.05),BMP2、Smad9和Runx2表达下降(P<0.01),BMPR2和Osx表达升高(P<0.05或P<0.01);而诱导晚期的BMP2、BMPR1A、Smad1、Smad4、Smad5、Smad9和Runx2均急剧升高(P<0.01),BMPR1B表达降低(P<0.01)。结论 BMP/Smad信号途径介导了5-HMF诱导BMSCs成骨分化的过程;其基因表达变化主要发生在诱导48h之后。

5-HMF对早期2型糖尿病合并肝损伤小鼠糖脂代谢和肝功能影响的研究

目的研究5-羟甲基-2-糠醛(5-HMF)对早期2型糖尿病(T2DM)合并肝损伤小鼠糖脂代谢和肝功能的影响。方法设5-HMF低、中、高剂量组,模型对照组和正常对照组,每组10只雌性ICR小鼠。低、中、高剂量组每天按10 mL/kg体重分别给予0.27、0.80、2.67 mg/kg 5-HMF灌胃,模型对照组和正常对照组给予同体积去离子水,连续12周。各剂量组和模型对照组喂饲36%高脂高糖饲料,实验第10、11周腹腔注射四氧嘧啶60 mg/kg体重;正常对照组喂饲维持饲料。定期测定体重、血糖、血脂和肝功能。留取肝组织,肝糖原高碘酸-希夫染色,观察组织病理学变化。结果模型对照组小鼠血糖(GLU)、低密度脂蛋白胆固醇(LDL-C)、高密度脂蛋白胆固醇(HDL-C)、谷丙转氨酶(ALT)、谷草转氨酶(AST)和乳酸脱氢酶(LDH)水平均高于正常对照组(P<0.05)。低、高剂量组小鼠AST水平,低、中、高剂量组小鼠LDH水平均低于模型对照组(P<0.05)。低、中、高剂量组小鼠GLU、总胆固醇(TC)、三酰甘油(TG)、LDL-C、HDL-C和ALT水平与模型对照组比较差异均无统计学意义(P>0.05)。模型对照组小鼠肝组织可见中至重度肝细胞空泡变性,高剂量组小鼠仅见轻微至轻度空泡变性;高剂量组和模型对照组小鼠均有中等或大量肝糖原颗粒。结论本实验条件下尚不能判断5-HMF对T2DM合并肝损伤小鼠有降血糖和降血脂作用,但可证明其对小鼠肝组织及功能有保护作用。

Catalytic transformations of cellulose and its derived carbohydrates into 5-hydroxymethylfurfural, levulinic acid, and lactic acid

The catalytic transformation of cellulose into key building-block or platform chemicals such as 5-hydoxymethylfurfural(HMF),levulinic acid,and lactic acid under mild conditions,has attracted much attention in recent years,as these conversions can be operated without consumption of hydrogen or oxygen and thus are more economical compared to the hydrogenolysis or oxidation of cellulose.This review article highlights recent advances in the development of novel catalysts or catalytic processes for the conversion of cellulose and its derived carbohydrates into HMF,levulinic acid,and lactic acid or their esters under inert atmosphere.We also analyze efficient catalytic systems for HMF production,in particular Lewis acids combined with ionic liquid or biphasic systems.For the formations of levulinic and lactic acids or their esters,we focus on the reactions in aqueous and alcohol media catalyzed by multifunctional catalysts that combine the functions of hydrolysis,isomerization,and dehydration-rehydration or retro-aldol reactions.The reaction mechanism for each process will also be discussed to gain insights into the activation of C–O and C–C bonds in the absence of hydrogen or oxygen.

Correlation between 5-hydroxymethylfurfural content and color of Rehmanniae Radix and Rehmanniae Radix Praeparata

In the present study,we explored the correlation between 5-hydroxymethylfurfural(5-HMF)and color of Rehmanniae Radix(RR)and Rehmanniae Radix Praeparata(RRP).The color was observed by human eyes under sunlight.The chromatic value and color difference were detected by a colorimeter.The water content was determined by an oven-drying method.The 5-HMF content was determined by an HPLC method.The correlation between the 5-HMF content and the color was analyzed by bivariate correlation analysis.The results showed that the color was greyish-brown and dark brown for RR,and it was black for RRP.The deepening color of RRP was reflected in the decrease of L^*,a^*and b^*values.The water content was in accord with the requirement of Chinese Pharmacopoeia.The 5-HMF contents of RR and RRP were 0.9711–25.71μg/g and 213.4–4010μg/g,respectively.The average 5-HMF contents of RR and RRP were 8.059μg/g and 1433μg/g,respectively.The 5-HMF content in RRP was higher than that in RR.The correlations between 5-HMF content and L^*,a^*and b^*values were significant.The color of RRP was deeper than that of RR.The 5-HMF content of RRP was higher than 0.02%,while it was less than 0.02%of RR,which could be used as a marker component for judging RR and RRP.

Efficient aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid on Ru/C catalysts

2,5-Furandicarboxylic(FDCA) is a potential substitute for petroleum-derived terephthalic acid, and aerobic oxidation of5-hydroxymethylfurfural(HMF) provides an efficient route to synthesis of FDCA. On an activated carbon supported ruthenium(Ru/C) catalyst(with 5 wt% Ru loading), HMF was readily oxidized to FDCA in a high yield of 97.3% at 383 K and 1.0 MPa O_2 in the presence of Mg(OH)_2 as base additive. Ru/C was superior to Pt/C and Pd/C and also other supported Ru catalysts with similar sizes of metal nanoparticles(1–2 nm). The Ru/C catalysts were stable and recyclable, and their efficiency in the formation of FDCA increased with Ru loadings examined in the range of 0.5 wt%–5.0 wt%. Based on the kinetic studies including the effects of reaction time, reaction temperature, O_2 pressure, on the oxidation of HMF to FDCA on Ru/C, it was confirmed that the oxidation of HMF to FDCA proceeds involving the primary oxidation of HMF to 2,5-diformylfuran(DFF) intermediate, and its sequential oxidation to 5-formyl-2-furancarboxylic acid(FFCA) and ultimately to FDCA, in which the oxidation of FFCA to FDCA is the rate-determining step and dictates the overall formation rate of FDCA. This study provides directions towards efficient synthesis of FDCA from HMF, for example, by designing novel catalysts more efficient for the involved oxidation step of FFCA to FDCA.