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An efficient catalytic system for producing 5-hydroxymethylfurfural from high-concentration fructose has been built by creating micro-reactors with cetyltrimethylammonium bromide in a mixed solvent of 1,4-dioxane and water.

A universal understanding on the concentration-aggravated evolution of humins during fructose dehydration has been demonstrated, wherein difructose anhydrides act as the key intermediates for both 5-hydroxymethylfurfural and humin formations.

The high-efficiency conversion of fructose to 5-hydroxymethylfurfural (HMF) with approving yields is challenging in biorefinery. In this work, we develop an efficient method of preparing HMF from f...

The degradative condensation of hexose, which originates from the C-C cleavage of hexose and condensation of degraded hexose fragment, is one of the possible reaction pathways for the formation of humins in hexose dehydration to 5-hydroxymethylfurfural (HMF). Herein, the impacts of several polar aprotic solvents on the degradative condensation of fructose to small-molecule carboxylic acids and oligomers (possible precursors of humins) are reported. In particular, a close relationship between the tautomeric distribution of fructose in solvents and the mechanism of degradative condensation is demonstrated. Typically, α-fructofuranose in 1,4-dioxane and acyclic open-chain fructose in THF favor the conversion of fructose to formic acid and oligomers; α-fructopyranose in γ-valerolactone or N-methylpyrrolidone favors levulinic acid and oligomers, whereas β-fructopyranose in 4-methyl-2-pentanone favors acetic acid and corresponding oligomers. This close correlation highlights a general understanding of the solvent-controlled formation of oligomers, which represents an important step toward the rational design of effective solvent systems for HMF production.

We report a novel solid organocatalyst, a double-hydrogen-bonded sulfonated polymer catalyst (D-SPC), for the cascade conversion of fructose to 5-ethoxymethylfurfural (EMF) with a highest yield of 68.8 mol% and good catalyst recyclability. We demonstrate that the treatment of a sulfonated nitrogen-containing polymer catalyst (SPC) with dihydroxy acetone (DHA) molecules generates new double hydrogen-bonds (H-bonds) between the ring-attached sulfonic acid groups and DHA by deconstructing the existing H-bonds between the sulfonic acid groups and imine/amine nitrogens of the SPC, which is confirmed by FT-IR spectroscopy, elemental analysis, 1H MAS and 13C cross-polarization MAS NMR, X-ray photoelectron spectroscopy (XPS), and quantum chemical calculations. The 31P MAS NMR, pHsurface, and NH3-TPD of the catalysts reveal the weakening of acidity strength due to the stronger double H-bonding on the D-SPC. Notably, we figure out the inverse relationship between the acidity strength of the catalysts and the EMF yield in the one-pot fructose-to-EMF conversion, wherein the use of weaker acid catalysts accelerates the fructose dehydration while decelerating the side-reaction of furan ring opening, therefore avoiding the negative influence of water on the tandem reactions. Moreover, the existence of stable double H-bonds contributes to the good catalyst recyclability due to the stabilization of sulfonic acid groups. The acidic property of the solid catalysts could be adjusted by varying the DHA dosage and the preparation conditions of the SPC (i.e., monomer ratio and oxidant dosage), respectively. We show that the solid acid catalyst with weaker acidity strength and suitable acidity density (ca. 2.5 mmol g−1) is favorable for the one-pot synthesis of EMF directly from fructose. This work highlights the application of novel sulfonated polymer catalysts with adjustable acidic property for the highly selective production of EMF, a liquid biofuel candidate, from biomass-derived carbohydrates.

Biomass-derived hexose constitutes the main component of lignocellulosic biomass for producing value-added chemicals and biofuels. However, the reaction network of hexose is complicated, which makes the highly selective synthesis of one particular product challenging in biorefinery. This Review focuses on the selective production of 5-hydroxymethylfurfural (HMF) from glucose on account of its potential significance as an important platform molecule. The complex reaction network involved in glucose-to-HMF transformations is briefly summarized. Special emphasis is placed on analyzing the complexities of feedstocks, intermediates, (side-) products, catalysts, solvents, and their impacts on the reaction network. The strategies and representative examples for adjusting the reaction pathway toward HMF by developing multifunctional catalysts and promoters, taking advantage of solvent effects and process intensification, and synergizing all measures are comprehensively discussed. An outlook is provided to highlight the challenges and opportunities faced in this promising field. It is expected to provide guidance to design practical catalytic processes for advancing HMF biorefinery.

Novel polymeric solid catalysts, Au@(polythiophene–polythiophene oxides) (Au@PTh–PThOx, x=1–2), are prepared by chemical over-oxidative polymerization of thiophene in the presence of Au nanoparticles. These organocatalysts show significantly higher activity than their liquid analogs (i.e., DMSO, a frequently-used solvent and catalyst) for the catalytic dehydration of fructose into 5-hydroxymethylfurfural (HMF) and exhibit a complete inhibiting effect on HMF rehydration to undesired levulinic acid in low-boiling solvents. We demonstrate that the sulfoxide (-SO) group in Au@PTh–PThOx is more active than the sulfone (-SO2) group, although the formation of the former could be maximized by lowering the concentration of surfactant or improving the concentration of oxidant used in catalyst preparation. The highest HMF yields of 72.6 % and 39.7 % are achieved over Au@PTh–PThO catalyst in 1,4-dioxane and water, respectively. This catalyst could be completely recycled for use in water without activity loss.

The performance of DMSO for the dehydration of fructose to 5-hydroxymethylfurfural (HMF) in the presence and absence of Bronsted acid has been theoretically investigated at G4 level in DMSO solution. The most stable form of fructose is β-D-fructofuranoses in DMSO solution. When Bronsted acid is present in the reaction system, H+ prefers to interact with DMSO other than fructose, forming [DMSOH]+ as the catalytically active species. For the dehydration of fructose to HMF, the catalytic performance of DMSO stems from the valence unsaturation of both S and O atoms and the unsaturated double bond of S═O, and the catalytic role of [DMSOH]+ originates from the valence unsaturation of both S and O atoms, as well as the H-mediated effect of −SOH group. For the initial and third water molecule release steps from fructose, both DMSO and [DMSOH]+ exhibit catalytic activity. Nevertheless, for the second water molecule release step from fructose, [DMSOH]+ displays catalytic activity, but DMSO does not. The active spec...

The transformation of readily available cellulosic biomass to small-molecule products is important in biorefining. To improve the economic viability, the formation of humins should be limited. Herein, we report the effective suppression of humin precursor (i.e., oligomer) formation in glucose-to-5-hydroxymethylfurfural (HMF) dehydration by the synergetic action of tetrahydrofuran (THF) and low-pressure CO2 (1.0 MPa). We show that four kinds of oligomers are formed in water, wherein the cross-condensation of HMF and levulinic acid (LA) generates oligomers (I) and (II), and the self-condensation of HMF generates oligomer (III), while the degradation of glucose/fructose generates oligomer (IV). In CO2-splitted triphasic H2O/THF (VH2O/VTHF = 1 : 1), the formation of oligomers (I) and (IV) is suppressed by CO2, while the formation of oligomers (I), (II), and (III) is inhibited by THF. This work highlights a strategy for increasing carbon utilization from glucose conversion by controlling the subreactions to favor the pathways towards the formation of small-molecule products.

The rehydration of 5-hydroxymethylfurfural (HMF), an important bio-based chemical building block, to levulinic acid (LA) and formic acid (FA) over Bronsted acid catalysts is the key block to the effective production of HMF from hexose. In this work, we develop a novel acidic solid organocatalyst, sulfonated polyaniline (SPAN), for the effective dehydration of fructose into HMF in the low-boiling water/1,4-dioxane cosolvent. The highest HMF yield of 71% is obtained from fructose with complete restriction of HMF rehydration to LA. We demonstrate that hydrogen bonds form between the ring-attached sulfonic acid group and the quinoid imine nitrogen as a result of internal doping, which confines the Bronsted acidity of the SPAN catalyst. The H-bonded sulfonic acid species is active for fructose-to-HMF dehydration and complete suppression on HMF rehydration. The chemical bonding of sulfonic acid groups on the backbone of the PAN chain allows stable recyclability of the polymer catalyst. This work highlights the potential importance of confining Bronsted acidity on a solid organocatalyst via H-bonding for transforming renewable carbohydrates into fine chemicals.

We performed a systematic experimental kinetics study on AlCl3-catalyzed conversion of glucose to 5-hydroxymethylfurfural (HMF) in NaCl–H2O/tetrahydrofuran (THF) biphasic solvent. The kinetics model covers an extensive reaction network including the parallel and tandem reactions of isomerization, dehydration, decomposition, and polymerization from glucose. The accuracy of the model was verified by a parity plot and statistical significance analysis of the kinetic parameters. A deliberate insight into the intrinsic kinetic properties (reaction rate constant and apparent activation energy) of each subreaction elaborates the regulatory role of THF and NaCl on reaction pathways within the network. That is, THF suppresses the rehydration, degradation, and polymerization of HMF to unwanted byproducts, inhibits fructose-to-HMF dehydration and fructose-to-humins polymerization, but promotes the generation of formic acid (FA) from the direct degradation of both glucose and fructose by facilitating the generation o...

We report the preparation of bifunctional hybrid catalysts by supporting H3PMo12O40 (PMo12) heteropolyacid (HPA) on polyaniline (PAN) or formyl-functionalized PAN (F-PAN) for the &ldquo, one-pot&rdquo, and &ldquo, one-step&rdquo, synthesis of 2,5-diformylfuran (DFF) from fructose via 5-hydroxymethylfurfural (HMF) intermediate. We show that the PMo12 HPA is the main active species for both fructose dehydration and HMF oxidation owing to its Br&oslash, nsted acidic and redox characters. However, the anchoring of PMo12 on PAN reduces the Br&oslash, nsted acidity by acid&ndash, base interaction between protons in HPA and quinoid diimine structure in PAN, thereby reducing the dehydration performance. We demonstrate that the catalytic dehydration performance of the hybrid catalyst could be strengthened by grafting formyl groups on PAN before HPA anchoring. The highest DFF yield of 76.7% is obtained by conducting the &ldquo, reaction over the 40-PMo12/F3-PAN catalyst at 413 K for 7 h in air, wherein the side-reactions of fructose or HMF degradation and HMF rehydration have been significantly reduced. This hybrid catalyst is reusable without significant activity loss, highlighting the designing of stable inorganic&ndash, organic hybrid catalysts for producing valuable hexose-derived platform chemicals.

The selective removal of oxygen from 5-hydroxymethylfurfural (HMF) is challenging for the effective utilization of biomass. The catalytic mechanisms of palladium acetate toward the conversion of HMF to furfuryl alcohol (FFA), 5-methylfurfural (5-MF) and 2,5-dihydroxymethyl furan (DHMF) have been theoretically investigated. The decarbonylation of HMF to FFA includes (i) migratory extrusion, (ii) metal-acetate-co-assisted deprotonation, (iii) decarbonylation, (iv) metal-assisted deprotonation, and (v) migratory extrusion and catalyst regeneration. Both hydrogenation and deoxidation of HMF with HCOOH as the H-source involve (i) migratory extrusion, (ii) oxidative addition, (iii) reductive elimination, (iv) metal-assisted deprotonation, and (v) migratory extrusion and catalyst regeneration. The C–H bond cleavage is the crucial reaction step, in which the metal-acetate-co-assisted deprotonation is kinetically more preferable than the oxidative addition. Both FFA and DHMF are kinetically superior to 5-MF. In terms of selectivity, increasing the temperature is beneficial to decarbonylation and decreasing the temperature is advantageous to hydrogenation. The present finding provides molecular-level insight into the functions of both the metal-center and coordinated-ligand in the Pd(OAc)2 catalyst, which may drive the novel design of catalytic systems toward both decarbonylation and hydrogenation reactions.

We report an unprecedented solid organic-base catalyst, formyl-modified polyaniline (FS-PAN), for the dehydration of fructose to 5-hydroxymethylfurfural (HMF) with a high yield of 90.4 mol %. We demonstrate that the nitrogen atoms incorporated between the phenyl rings in the backbone of the polyaniline chain contribute to the basicity of the catalyst. The grafting of electron-withdrawing formyl groups to the imine nitrogen atoms leads to a significant increase of basicity of the polymer catalyst owing to the greater localization of electrons at the amide nitrogen atom formed. A linear dependence of the yield of HMF on the grafting level of formyl groups in FS-PAN indicates that the amide acts as the active phase. A possible reaction mechanism for this organic-base-catalyzed dehydration reaction is proposed. The side-reaction of HMF rehydration is inhibited thoroughly, and the condensation of any reaction intermediates to undesirable oligomers is restrained by this base catalyst. This organic-base catalyst can be recycled completely without loss of activity. This research highlights the first application of a highly effective and stable solid base catalyst for the transformation of renewable carbohydrates into fine chemicals.

Fructose was deoxygenated to furfuryl alcohol (FFA) by tandem dehydration and decarbonylation in one pot over the AlCl3⋅6 H2O/Pd(OAc)2 catalyst combination to give a high FFA yield of 40.6 %. AlCl3⋅6 H2O behaves as an effective Lewis acid to catalyze the dehydration of fructose to 5-hydroxymethylfurfural (HMF), and subsequently, Pd(OAc)2 catalyzes the removal of a CO moiety from HMF to produce FFA selectively. The hydroxyl group on the HMF intermediate was stabilized by poly(1-vinyl-2-pyrrolidinone) through an intermolecular hydrogen bond, which accelerated the dehydration of fructose and inhibited the hydrogenation of HMF by formic acid. The decarbonylation of HMF was promoted and the unwanted decomposition of fructose was inhibited through the use of 4 A molecular sieves. This research highlights a “one-pot” catalytic system to transform renewable carbohydrates into fine chemicals by tandem dehydration and decarbonylation reactions without the separation or purification of HMF.

The nature of the active aluminum species and their interaction with glucose in water are studied to establish a detailed mechanism for understanding AlCl3-catalyzed glucose-to-fructose isomerization. The combination of activity results with electrospray ionization tandem mass spectrometry (ESI-MS/MS) reveal that [Al(OH)2(aq)]+ species contribute a lot to the isomerization. Attenuated total reflection infrared spectroscopy (ATR-IR) results show that glucose undergoes a ring-opening process which is accelerated by the [Al(OH)2(aq)]+ species. The binding of acyclic glucose with [Al(OH)2(aq)]+ species occurs at the C1–O and C2–O positions of glucose, which initiates the hydride shift of the aldose-to-ketose isomerization. The in situ 27Al NMR data elucidate the maintenance of the hexa-coordinated form of Al species throughout the reaction. An obvious kinetic isotope effect occurs with the C2 deuterium-labeled glucose, confirming that the intramolecular hydride shift from the C2 to C1 positions of glucose is ...

Co-pyrolysis is regarded as an effective approach to upgrade the quality of pyrolysis products. In this work the activity of KF-846 was evaluated by co-pyrolysis of pubescens and low density polyethylene under different experimental conditions including catalytic mode, pyrolytic atmosphere and temperature, etc. The results showed that the fresh KF-846 exerted strong effects of cyclization, aromatization, hydrogen transfer and vapor-catalytic reforming reactions on the primary intermediates from the co-pyrolysis. The hydrogen-rich gases indicated a synergistic effect between Ni and Mo over KF-846 on producing hydrogen. More importantly, the reforming reactions might be inhibited to some extent by H2 atmosphere, the low temperature and the decrease of acidity over catalyst. Furthermore, it was deduced that the oxygen over the lattice of catalyst or some intermediates might transfer into other intermediates, possibly resulting in more products with high oxygen content, but it was presumed that the low temperature, co-pyrolysis process and N2 atmosphere could repress the trend to a certain degree. The mass and energy balance of co-pyrolysis were analyzed, and the main reaction pathways were also proposed. The interference in pyrolysis by regulating the catalytic mode, pyrolytic atmosphere and temperature, acidity over catalyst might posses a certain guiding significance for the pyrolytic technology and the design/selection of catalysts employed.

The catalysts (Me)-Al-MCM-41 (Me = Ni, Pd and their combination) were synthesized hydrothermally, characterized with XRD, BET, NH 3 -TPD, SEM, TEM, XPS, H 2 -TPR, chemisorption of hydrogen, and tested by experiments of co-pyrolysis of pubescens and LDPE under vapor-catalyzed condition. Characterization results suggested that the synthesis of Al-MCM-41 was successful, but the introduction of Me into Al-MCM-41 caused some changes in structure of catalyst to a certain degree, resulting in significant changes in their properties and catalytic behavior. The results obtained from vapor-catalyzed co-pyrolysis over these catalysts showed that there were some interactions between the intermediate species from the co-pyrolysis, as the relative content of aromatics in oil was high, whereas that of phenol in corresponding aqua was low, and vice versa. The type of metal in catalysts was of more importance than the metal siting. Moreover, all catalysts except Ni-Pd-Al-MCM-41 exerted strong effect of alkanisation on the primary intermediate species from the pyrolysis of LDPE, which demonstrated that the pore architecture of parent Al-MCM-41 and (Me)-Al-MCM-41 containing single Me strongly favored the reactions in relation to alkanisation; on the contrary, Ni-Pd-Al-MCM-41 exerted a strong effect of dehydrogenation on those primary intermediate species. More importantly, the synergistic effect on producing hydrogen, based on the 61.8 vol.% of H 2 in gaseous mixture, indicated that the combination of Ni and Pd in (Me)-Al-MCM-41 might bring about a novel performance during the vapor-catalyzed co-pyrolysis of biomass and plastics. It was predicted that Ni-Pd-Al-MCM-41 might play its special application in development of hydrogen energy, exploitation and utilization of biomass as well as municipal solid waste (MSW) such as waste plastics, etc. The major schemes of reactions involved in the vapor-catalyzed co-pyrolysis had been proposed.

One-dimensional assembly of gold nanoparticles (see picture)is achieved by a sphere-to-cylinder transformation of polymer shells. A large amount of monomers remains after the assembly, which is characteristic of the chain-growth “polymerization”. Single-line chains can be converted to double-line chains, thus substantiating the unique role of the polymer shell.

The effect of zirconium addition on vanadium-catalyzed toluene oxidation by hydrogen peroxide in acetic acid was studied. 51 V NMR, ESI-MS and DFT calculation were used to characterize the intermediate metal species formed in the reaction. Over high vanadium amount, the addition of Zr is beneficial for benzaldehyde generation and toluene conversion, and the ratio of (benzaldehyde + benzoic acid)/(benzyl alcohol + benzyl acetate) was enhanced. Dimer of vanadium may directly coordinate to zirconium to form soluble mixed zirconium–vanadium polymeric species, which inhibited the further aggregation of vanadium. The structures of these species were determined by ESI-MS and DFT calculation. The trinuclear complex (OH)(OAc)Zr(μ-O) 2 V(OH)(μ-O) 2 V(OH)(OAc) showed compatible activity to the best catalyst VO(OH) 2 (OAc) for benzyl peroxide dehydration. The rate-determining step of benzyl peroxide dehydration catalyzed by metal species was the abstraction of α-H of PhCH 2 OO ligand.

Reaction pathways and free-energy profiles for the conversion of benzene and hydroxylamine to aniline, catalyzed by NaVO3 and VOSO4, in acetic acid/water, were discussed using density functional th...

High-valent iron(IV)-oxo species was proved to be the main oxidizing species for hydroxylation of benzene to phenol by a Fenton-like reagent in triethylammonium acetate ionic liquid via UV–vis and ESI-MS characterization, while hydroxyl radical was excluded by detailed investigations. It was found that the formation of hydroxyl radical was prohibited by the reduction of redox potential of Fe(III)/Fe(II) couple in triethylammonium acetate medium, leading to a decreased over-oxidation of benzene than that in aqueous solution. The reaction mechanisms for hydroxylation of benzene, as well as for over-oxidation of phenol by iron(IV)-oxo species were proposed. The latter is partly prohibited by the hydrogen-bond interaction between as-produced phenol and acetate anion of the ionic liquid.

The stepwise hydrothermal conversion of Pubescens selectively to furans and phenol compounds was investigated in a sealed autoclave reactor. The influence of reaction temperature and reaction time on the product distribution was studied. The results were compared to those from direct pyrolysis process. The residues from Pubescens via hydrothermal route and pyrolytic route were characterized by SEM and component analysis. A new method for obtaining furans and phenols separately through a two-step process was proposed. The first step was suggested performing at a moderate temperature for a shorter time to obtain liquid product with high furan content, while the second step was designed proceeding at a higher temperature for a comparatively longer time to produce more phenol compounds.

The competitive oxidation of the C–H bonds on the aromatic ring and side-chain of ethylbenzene (EB) with hydrogen peroxide is investigated over four diperoxovanadate catalysts, that is, K 3 [VO(O 2 ) 2 (ox)] (bpV(ox)), K 2 [VO(O 2 ) 2 (pic)] (bpV(pic)), K[VO(O 2 ) 2 (bpy)] (bpV(bpy)), and K[VO(O 2 ) 2 (phen)] (bpV(phen)). The selectivity to ring C–H bonds activation is found to be affected by the polarity and acidity of the solvent. The electrophilicity of the diperoxovanadate complexes and their catalytic performance are tuned by different ligands. The high electrophilicity of the vanadium center shows preference for the ring C–H bonds activation. The HOAc molecule was involved not only in the ligand exchange around the vanadium center, but also in the stabilization of the diperoxovanadium species in the media. A polar intermediate mechanism by generating electrophilic catalytic species is proposed. The bpV(bpy)–H 2 O 2 –HOAc system is found to be effective for the selective activation of the C–H bonds on aromatic ring of EB ( S = 68.3%). It shows promise for the direct one-step synthesis of substituted-phenols from alkylbenzene.

The catalytic reforming of the pyrolytic intermediates from the co-pyrolysis of pubescens and LDPE over the parent and desilicated zeolite ZSM-5 (DeZSM-5) was investigated. The results showed that the parent HZSM-5 exhibited high aromatization activity in the co-pyrolysis, whereas DeZSM-5 exhibited high alkanisation activity. On the other hand, the total relative content of phenolic compounds in aqua obtained by co-pyrolysis catalyzed by both parent HZSM-5 and DeZSM-5 was rather high (60–65%) compared to the thermal co-pyrolysis (26.94%). From the analysis of NH3–TPD for ZSM-5, it might be proposed that the aromatization was favored mainly by strong acid sites and the alkanisation was favored chiefly by weak acid sites in catalyst ZSM-5. In addition, the formation of phenolic compounds was mainly related to the interactions between the intermediates from the co-pyrolysis over ZSM-5.

A laboratory reactor was designed to test the effect of the interference instant of HY on the pyrolysis of pubescens. The time instant for intermediate species from pyrolysis to contact HY was controlled by varying the position of the catalyst bed relative to the pyrolytic cell. It was found that the effect of the interference instant was significant on the variation of different intermediate species, and the yield and quality of the products. The results also showed that, with the increase in the distance between the pyrolytic cell and the catalyst bed, the yield of liquid and relative content of the organics such as aldehyde, phenols, etc ., decreased, while the yield of residue and relative content of acetic acid increased. The deoxygenation of the intermediate species was favored when the catalyst exerted its performance on them immediately after their formation.

Cellulose was dissolved in the ionic liquid 1-butyl-3-methylimidazolium chloride, and then regenerated from the solution by using different methods. Thermogravimetric analysis (TG)-Differential Scanning Calorimetry (DSC), X-ray diffraction (XRD), and Scanning Electron Microscopy (SEM) were used to characterize the structure of the original and regenerated cellulose. Cellulose II or amorphous cellulose was obtained by pouring cellulose solution into de-ioned water or pouring de-ioned water into cellulose solution, respectively. The pyrolysis behavior of original and regenerated cellulose was tested in a fixed bed reactor. The pyrolysis of cellulose I gave high content of furfural and 1,4;3,6-dianhydro-alpha- d -glucopyranose in the liquid products, and cellulose II and amorphous cellulose gave high content of furfural and 5-(hydroxymethyl)-2-furancarboxyaldehyde, with 5-(hydroxymethyl)-2-furancarboxyaldehyde the highest for cellulose II and furfural the highest for amorphous cellulose. And the treatment of the cellulose samples favored the removal of oxygen in the form of CO 2 in the pyrolysis.

The selective catalytic oxidation of toluene with hydrogen peroxide over V-Mo-based catalysts under mild conditions was studied. The promotion effect of Mo on the catalysts was studied with V/Al2O3 and Mo/Al2O3 as reference samples. The catalysts were characterized by XRD, TPR, and XPS techniques. The results show that the addition of Mo to V/Al2O3 may change the distribution of V species on Al2O3 surface. Over V-Mo/Al2O3 catalyst, highly dispersed amorphous V species facilitates benzaldehyde formation, and crystalline V2O5 species increases the conversion of toluene but decreases the selectivity to benzaldehyde, while AlVMoO7 species favors both the conversion of toluene and the formation of cresols. The yield of benzaldehyde depends remarkably on the surface O/Al and Mo/V atomic ratios, and gets to a maximum value of 13.2% with a selectivity of 79.5% at an O/Al atomic ratio of 3.0 and Mo/V atomic ratio of 0.7.

The oxidation of hydroxylamine by VO 2 + to the primary product HNO in gas phase were investigated with density functional theory (DFT) at the B3LYP/6-311++G(d,p) level. Calculations including geometry optimization and vibrational analysis for the stationary points on the ground and the first excited states were performed. Two possible mechanisms were investigated. The fist one is the one-electron mechanism through firstly the formation of NH2O and NHOH radical complexes ([VO(OH)(NH2O)]+ and [VO(OH)(NHOH)]+) from NH2OH and VO 2 + , and then the oxidation of the stable intermediate NH2O by VO 2 + to produce the products HNO and VO(OH)+. The one-electron mechanism is predicted to be spin-conserved and the rate-limiting step is the cleavage of the O–H bond with 27.92 kcal/mol energy barrier. The other one is the two-electron mechanism in which the first half is also the formation of NH2O and NHOH radical complexes and the second half is the intra-molecular hydrogen transfer of NH2O and NHOH radical complexes to the product HNO together with the reduction of VIV–VIII. The crossing point between singlet and triplet potential energy surfaces (PESs) results in the stable product triplet V(OH) 2 + in the two-electron mechanism. The two-electron mechanism may be kinetically competitive with the one-electron mechanism only if the spin inversion between singlet and triplet PESs occurs easily, while, the one-electron mechanism is energetically more favorable than the two-electron mechanism. Therefore, the one-electron mechanism is predominant.

The direct amination of benzene to aniline with hydroxylamine catalyzed by sodium metavanadate in acetic acid water under mild conditions took place more efficiently in open air than in a closed system. The presence of oxygen significantly enhanced the yield of aniline. Satisfactory aniline yield (64%) and turnover number (48 mol of aniline per mol of vanadium) were obtained under optimized reaction conditions. The decomposition of hydroxylamine was studied to understand its function during the amination process. A computational study on the UV–vis spectra of some typical vanadium complexes was carried out by the time-dependent DFT method. A free-radical mechanism is proposed based on the results of EPR, 51V NMR, and UV–vis characterizations.

The homogenous liquid-phase direct catalytic oxidation of benzene to phenol was performed at room temperature in acetonitrile solvent using sodium metavanadate as the catalyst and hydrogen peroxide as the oxidant. The effects of various reaction parameters, such as acidity of the system, reaction temperature, reaction time and the amount of hydrogen peroxide used, were studied. Under the optimized conditions, a phenol yield of 13.5% with a selectivity of 94% was obtained. The variation of vanadium species during the reaction was studied by in situ 51V-NMR method. It was found that vanadium species existed as VO2+ before the reaction. In the presence of hydrogen peroxide, VO2+ species might be transferred to peroxovanadate species, such as HVO(O2)2, VO(O2)+, which oxidized benzene to phenol exerting the catalytic performance. A catalytic cycle involving the above mechanism was proposed.

In this work, a one-pot strategy for directly converting fructose into 2,5-diformylfuran (DFF) over Mo-containing Keggin heteropolyacids (HPAs) in open air is developed. H3 PMo12 O40 HPA is found to show high activity and selectivity to the formation of DFF owing to its higher Bronsted acidity and moderate redox potential. The partial substitution of the H(+) in H3 PMo12 O40 with Cs(+) leads to the heterogenization of the HPA by forming its cesium salts Csx H3-x PMo12 (x=0.5, 1.5, and 2.5). A satisfactory yield of 69.3% to DFF is obtained over Cs0.5 H2.5 PMo12 polyoxometalate after deliberate optimization of the reaction conditions. The heterogenized polyoxometalate could be recycled and reused without significant loss of catalytic activity for five runs. The produced DFF could be separated from the resulting mixture by an adsorption-desorption method using activated carbon as the adsorbent and furfural as the desorbent. A highest isolated yield of 58.2% is obtained.

The liquid-phase direct catalytic amination of benzene to aniline was performed in acetic acid water solvent using a series of vanadium (III, IV, V) complexes with N,O- or O,O-ligands as catalysts and hydroxylamine hydrochloride as the aminating agent. The vanadium complexes exhibited much higher selectivity towards the production of aniline than NaVO3 or VOSO4. Under the optimized conditions, an aniline yield of 42.5% and a TON of 48 with a high selectivity of above 99.9% was obtained using 0.2 mmol of [VO(OAc)2] as the catalyst.

Catalytic distillation (CD) technology was used in the direct amination of benzene to aniline with aqueous ammonia and hydrogen peroxide over a V−Ni/Al2O3 catalyst. The effects of several parameters (including the packing manners of the catalytic column, the feed ratio, the distillation temperature, and the reaction time) on the amination were studied. It was found that the yield of aniline was significantly improved in the CD process, in comparison to the kettle-type reaction.

Over the past decade, ionic liquids (ILs) have received great deal of attention as possible “green” replacement for volatile organic solvent mainly due to their nonmeasurable vapor pressure and good dissolubility for other salts. [1-5] Reaction types successfully performed in ILs include Diels–Alder, [6] Friedel–Crafts, [7] olefin hydrogenation, [8] hydroformyla‐ tion, [9] , [10] oligomerization, [11] and Heck and Suzuki coupling reactions. [12] , [13] In addition to solvent, ILs may have multiple functions in catalytic reactions. They may act as catalyst, co-catalyst, support, or ligands for the catalytic process. [14] In particular, some “unexpected” effects have been observed in affecting the catalytic reaction pathway. For ex‐ ample, the cations/anions in ILs may be involved in the formation of the active species changing the reaction mechanism. [15] [20] Understanding the functions of ILs in the cata‐ lytic reaction is of critical importance for deliberately modifying existed reaction system and exploiting new types of synthetic route by using this “green” solvent.

Growth of polythiophene (PTh) on five-fold twinned Ag nanowires (NWs) is not symmetrical due to preferred etching of their intrinsic defects. This imbalance of polymer formation leads to consistent bending action along the etched NWs, coiling the resulting Ag-PTh nanocomposites into planar spirals. We studied the etching intermediates and also the effects of the surface ligands in order to understand the symmetry-breaking action. The defect-dependent etching chemistry offers a new means to induce motion and a novel perspective in the ordered occurrence of certain defects. We demonstrate that Ag can be deposited back onto the coiled Ag-PTh composite to form metallic spirals.

We show that embedding of a surface ligand can dramatically affect the metal–metal interfacial energy, making it possible to create nanostructures in defiance of traditional wisdom. Despite matching Au–Ag lattices, Au–Ag hybrid NPs can be continuously tuned from concentric core–shell, eccentric core–shell, acorn, to dimer structures. This method can be extended to tune even Au–Au and Ag–Ag interfaces.

We show that the microstructures of polycrystalline ice can serve as a confining template for one-dimensional assembly of colloidal nanoparticles. Upon simply freezing an aqueous colloid, the nanoparticles are excluded from ice grains and form chains in the ice veins. The nanoparticle chains are transferable and can be strengthened by polymer encapsulation. After coating with polyaniline shells, simple sedimentation is used to remove large aggregates, enriching single-line chains of 40 nm gold nanoparticles with a total length of several micrometers. When gold nanorods were used, they formed one-dimensional aggregates with specific end-to-end conformation, indicating the confining effects of the nanoscale ice veins at the final stage of freezing. The unbranched and ultralong plasmonic chains are of importance for future study of plasmonic coupling and development of plasmonic waveguides.

We show that bundles of carbon nanotubes can be coiled into ring structures by controlling the contraction of their polymer shells. With the robust carbon nanotubes, we demonstrate their reversible transformation between circular and compressed rings in a colloid.

Nannochloropsis sp. (a kind of green microalga) residue was pyrolyzed without catalyst or with different amount of HZSM-5 catalyst in a fixed bed reactor in nitrogen flow. The effects of pyrolysis parameters such as temperature and catalyst-to-material ratio on product yields were studied. The bio-oils obtained were analyzed by elemental, GC-MS and FTIR analysis. The results indicated that the bio-oils from catalytic pyrolysis of Nannochloropsis sp. residue (BOCP) had lower oxygen content (19.5 wt.%) and higher heating-value (32.7 MJ kg(-1)) than those obtained from direct pyrolysis (BODP) which had an oxygen content of 30.1 wt.% and heating-value of 24.6 MJ kg(-1). The BODP mainly consisted of long carbon chain compounds with various terminal groups (LCTG), while the BOCP mainly consisted of aromatic hydrocarbons. These properties of bio-oils demonstrated that the Nannochloropsis sp. residue can be used as a renewable energy resource and chemical feedstock.