Pt nanoparticles encapsulated on V_(2)O_(5)nanosheets carriers as efficient catalysts for promoted aerobic oxidative desulfurization performance

Platinum group metals(PGMs)usually exhibit promising aerobic catalytic abilities,providing a green and feasible oxidative desulfurization method.However,often,the PGM nanoparticles(NPs)get leached,and the catalysts are deactivated.In this work,Pt NPs with particle sizes of approximately 4–5 nm were encapsulated effectively and uniformly on the surface of vanadium pentoxide(V2O5)nanosheets(with thicknesses of approximately six atomic layers)through strong metal-support interactions.The synthesized catalysts promote catalytic aerobic oxidation reactions,realizing deep desulfurization(99.1%,<5μg g^(–1))under atmospheric pressure and 110℃reaction temperature.Remarkable degrees of sulfur removal could be achieved for oils with different initial S-concentrations and substrates.Additionally,the as-prepared catalysts could be recycled for reuse at least seven times.

Novel cobalt(Ⅱ) complexes of amino acids-Schiff bases catalyzed aerobic oxidation of various alcohols to ketones and aldehyde

Two cobalt（Ⅱ） complexes 1 and 2 of Schiff bases derived from amino acids were synthesized and used for oxidation of benzyl alcohol with molecular oxygen at different conditions of pH,solvent,temperature and complex/alcohol molar ratio to optimize reaction conditions and to evaluate the catalytic efficiency of new cobalt Schiff base complexes.Under obtained optimum conditions,various alcohols were oxidized to corresponding aldehydes and ketones.

Green aerobic oxidative desulfurization of diesel by constructing an Fe-Anderson type polyoxometalate and benzene sulfonic acid-based deep eutectic solvent biomimetic cycle

A unique redox-coupled biomimetic system was developed, in which Fe-Anderson type polyoxometalates(POMs) were employed as electron transfer mediators(ETMs) and benzenesulfonic acid(BSA)-based deep eutectic solvents(DESs) were used as electron-donors for aerobic oxidative desulfurization(AODS) of diesel fuel. Different compositions of DESs were used and the polyethylene glycol 2000(PEG2000)/2.5 BSA system showed the highest desulfurization activity, with the removal of dibenzothiophene(DBT) at 60 ℃ reaching 95% in 60 min. The excellent desulfurization activity of the system is due to the in situ formation of peroxysulfonate via a biomimetic process. By constructing a coupled redox system, Fe-Anderson type POMs as ETMs reduce the activation energy of oxygen-activated sulfonate. The physical characteristics of four different DESs were tested. The results show that the conductivity of DESs is correlated with the composition of BSA-based DESs. However, there is no similar trend in viscosity testing at the same temperature, and the maximum viscosity value is obtained for the PEG2000/2.5 BSA system at 60 ℃, which may be associated with the stronger hydrogen bonds. It is worth noting that the PEG2000/2.5 BSA system also possesses the best desulfurization activity, which suggests that the activity of the desulfurization system is related to the strength of the hydrogen bond in DESs. Finally, the biomimetic desulfurization system exhibits excellent performance and good stability under mild reaction conditions(60 ℃, atmospheric pressure, oxygen as the oxidant).

Aerobic Oxidation of Benzyl Alcohol Catalyzed by Cu-Mn Mixed Oxides and 2,2,6,6-Tetramethyl-piperidyl-1-oxyl

Heterogeneous Cu-Mn mixed oxides can mediate TEMPO-catalyzed selective oxidation of benzyl alcohol by molecular oxygen under neutral condition, and is recyclable. In the case of the molar ratio of Cu and Mn over 1, the highly-dispersed CuO inside the Cu-Mn mixed oxides is responsible for the good performances in catalytic oxidation.

Scalable and facile synthesis of V_(2)O_(5) nanoparticles via ball milling for improved aerobic oxidative desulfurization

In recent years, transition-metal oxides(TMOs) have been long employed for aerobic oxidative desulfurization. However, the inherent bottlenecks, such as the low explosion of active sites, limit the application of bulk TMOs catalyst. In this study, V_(2)O_(5) nanoparticles with oxygen vacancies were prepared in large-scale via facile ball milling strategy with adding oxalic acid as a reducing agent. The as-prepared catalysts exhibit remarkable sulfur removal for oils with different initial S-concentrations and different substrates. Sulfur removal could reach up to 99.7%(< 2 ppm) under the optimized reaction conditions. This work provides a feasible desulfurization strategy for fuel oils.

A new approach for the aerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid without using transition metal catalysts

The organic compound 2,5-furandicarboxylic acid（FDCA） has been identified by the US Department of Energy（DOE） as a valuable platform chemical for a wide range of industrial applications. Currently, the most popular route for FDCA synthesis is reported to be the oxidation of 5-hydroxymethylfurfural（HMF）by O_2 over the catalysis of noble metals（e.g., Au, Pt, Ru, and Pd）. However, the high costs of noble metal catalysts remain a major barrier for producing FDCA at an industrial scale. Herein, we report a transition metal-free synthesis strategy for the oxidation of HMF to FDCA under O_2 or ambient air. A simple but unprecedented process for the aerobic oxidation of HMF was carried out in organic solvents using only bases as the promoters. According to the high performance liquid chromatography（HPLC） analysis, excellent product yield（91%） was obtained in the presence of NaOH in dimethylformamide（DMF） at room temperature（25 ℃）. A plausible mechanism for the NaOH-promoted aerobic oxidation of HMF in DMF is also outlined in this paper. After the reaction, the sodium salt of FDCA particles were dispersed in the reaction mixture, making it possible for product separation and solvent reuse. The new HMF oxidation approach is expected to be a practical alternative to current ones, which depend on the use of noble metal catalysts.

Ce_(2)(MoO_(4))_(3) as an efficient catalyst for aerobic oxidative desulfurization of fuels

Ce_(2)(MoO_(4))_(3)was synthesized by a simple reflux method using cerium nitrate hexahydrate and ammonium molybdate as reactants.The as-prepared Ce_(2)(MoO_(4))_(3)was characterized by Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD),Scanning electron microscope(SEM),and X-ray photoelectron spectroscopy(XPS).The removal of dibenzothiophene(DBT)in model oil was studied using Ce_(2)(MoO_(4))_(3)as catalyst and oxygen as oxidant.The reaction factors such as reaction temperature,amount of catalyst,and sulfide type on sulfur removal were researched.The results prove that both Ce3+and MoO42-play significant role in the conversion from DBT to DBTO2.The Ce_(2)(MoO_(4))_(3)catalyst has an excellent performance for the sulfur removal of DBT.Under the optimum reaction conditions,sulfur removal of 99.6%was obtained.After recycling five times,no significant loss in catalyst activity of Ce_(2)(MoO_(4))_(3).Mechanism of aerobic oxidative desulfurization was proposed based on the experiment of free radical capture and infrared characterization.

Beneficial mechanisms of aerobic exercise on hepatic lipid metabolism in non-alcoholic fatty liver disease

BACKGROUND：Non-alcoholic fatty liver disease（NAFLD）refers to any fatty liver disease that is not due to excessive use of alcohol.NAFLD probably results from abnormal hepatic lipid metabolism and insulin resistance.Aerobic exercise is shown to improve NAFLD.This review aimed to evaluate the molecular mechanisms involved in the beneficial effects of aerobic exercise on NAFLD.DATA SOURCE：We searched articles in English on the role of aerobic exercise in NAFLD therapy in Pub Med.RESULTS： The mechanisms of chronic aerobic exercise in regulating the outcome of NAFLD include： （i） reducing in- trahepatic fat content by down-regulating sterol regulatory element-binding protein-lc and up-regulating peroxisome proliferator-activated receptor y expression levels; （ii） decreas- ing hepatic oxidative stress through modulating the reactive oxygen species, and enhancing antioxidant enzymes such as catalase and glutathione peroxidase; （iii） ameliorating hepatic inflammation via the inhibition of pro-inflammatory media- tors such as tumor necrosis factor-alpha and interleukin-1 beta; （iv） attenuating mitochondrial dependent apoptosis by reducing cytochrome C released from the mitochondria to the cytosol; and （v） inducing hepato-protective autophagy. CONCLUSION： Aerobic exercise, via different mechanisms, significantly decreases the fat content of the liver and improves the outcomes of patients with NAFLD.

Base-free aerobic oxidation of glycerol on TiO_2-supported bimetallic Au–Pt catalysts

The aerobic oxidation of glycerol provides an economically viable route to glyceraldehyde, dihydroxyacetone and glyceric acid with versatile applications, for which monometallic Pt, Au and Pd and bimetallic Au-Pt, Au- Pd and Pt-Pd catalysts on TiO2 were examined under base-free conditions. Pt exhibited a superior activity relative to Pd, and Au-Pd and Pt-Pd while Au was essentially inactive. The presence of Au on the Au-Pt/TiO2 catalysts led to their higher activities （normalized per Pt atom） in a wide range of Au/Pt atomic ratios （i.e. 1/3-7/1 ）, and the one with the Au/Pt ratio of 3/1 exhibited the highest activity. Such promoting effect is ascribed to the increased electron density on Pt via the electron transfer from Au to Pt, as characterized by the temperature-programmed desorption of CO and infra-red spectroscopy for CO adsorption. Meanwhile, the presence of Au on Au-Pt/TiO2, most like due to the observed electron transfer, changed the product selectivity, and facilitated the oxidation of the secondary hydroxyl groups in glycerol, leading to the favorable formation of dihydroxyacetone over glyceraldehyde and glyceric acid that were derived from the oxidation of the primary hydroxyl groups. The synergetic effect between Au and Pt demonstrates the feasibility in the efficient oxidation of glycerol to the targeted products, for example, by rational tuning of the electronic properties of metal catalysts.

The Variation of Microbial(Methanotroph)Communities in Marine Sediments Due to Aerobic Oxidation of Hydrocarbons

Methanotrophs in marine sediments and overlying water attenuate the emissions of methane into the atmosphere and thus play an important role for the global cycle of this greenhouse gas.However,gas released from natural hydrocarbon seeps are not pure methane but commonly mixed hydrocarbons.Currently,how methanotrophic bacteria behave in the co-presence of methane and heavier hydrocarbons remains unknown.In this paper,the bacteria were cultured aerobically in fresh sediment samples(collected from Bohai Bay in eastern China)at 28℃under the atmospheres of pure methane and methane+ethane+propane mixed gas,respec-tively.The prevailing terrigenous n-alkanes and fatty acids in the original sediment samples varied consistently after incubations,confirming the proceeding of aerobic bacterial activities.The real-time quantitative PCR assay and sequencing of the 16S rRNA and particulate methane monooxygenase(pmoA)genes revealed the changes of microbe communities to a methanotroph-dominating structure after incubations.Particularly,after incubations the family Methylococcaceae(typeⅠmethanotrophs)became dominant with proportions higher than 40%,whereas Methylocystaceae(typeⅡmethanotrophs)nearly disappeared in all incubated samples.More-over,the species of methanotrophs from the samples treated with pure methane were dominated by Methylobacter luteus,whereas Methylobacter whittenburyi took the predominant proportion in the samples treated with mixed gas.The phenomenon suggests that some methanotrophs may also utilize ethane and propane.Collectively,this study may help to gain a better understanding of the ef-fects and contributions of microbial activities in marine hydrocarbon seep ecosystems.

Rational construction of metal–base synergetic sites on Au/Mg-beta catalyst for selective aerobic oxidation of 5-hydroxymethylfurfural

The selective aerobic oxidation of biomass-derived 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid (FDCA, a potential renewable substitution of fossil-based terephthalic acid to produce polyethylene 2,5-furandicarboxylate plastic) is an appealing transformation for constructing eco-friendly and sustainable chemical processes. Au supported catalysts have showed encouraging performances for this well-received conversion, whose catalytic behavior was greatly affected by the adopted support derived from the existence of metal-support interactions. Herein, a series of Mg-Beta zeolites were hydrothermally synthesized via developed structural reconstruction, which were employed as basic supports for Au catalysts to construct bifunctional catalysts. The relationship between structure (Au particle size, basicity within zeolites and Auδ+ contents) and FDCA yield was concretely established. The conclusion was made that the utilization of Mg-Beta zeolites with strong basicity as the support could not only improve the FDCA yield but also decrease the amount of additional base. Furthermore, the possible reaction mechanism was also proposed via tracking time-dependent variations of corresponding organics and controlled experiment. This work provides some guidance for rationally designing multifunctional catalysts in the view of integrating metal catalysts with metallosilicate zeolites, which was beneficial to the catalytic upgrading of organic compounds with multiple functional groups.

Highly efficient base-free aerobic oxidation of alcohols over gold nanoparticles supported on ZnO-CuO mixed oxides

The design and preparation of suitable supports are of great importance for gold catalysts to attain excellent catalytic performance for alcohol oxidation.In this work,we found that ZnO-CuO mixed oxides supported gold catalysts showed much better catalytic activity for base-free aerobic oxidation of benzyl alcohol than Au/ZnO and Au/CuO catalysts,and among them Au/Zn0.7Cu0.3O displayed the best catalytic performance.In addition,the Au/Zn0.7Cu0.3O catalyst could selectively catalyze the aerobic oxidation of a wide range of alcohols to produce the corresponding carbonyl compounds with high yields under mild conditions without base.Further characterizations indicated that the outstanding catalytic performance of Au/Zn0.7Cu0.3O was correlated with the small size of Au nanoparticles(NPs),good low-temperature reducibility,high concentration of surface oxygen species,and collaborative interaction between Au NPs and mixed oxide.

Efficient aerobic oxidative desulfurization via three-dimensional ordered macroporous tungsten-titanium oxides

A series of three-dimensional ordered macroporous(3 DOM)W-TiO_(2)catalysts have been prepared through a facile colloidal crystal template method.The prepared materials characterized in detail exhibited enhanced catalytic activity in aerobic oxidative desulfurization process.The experimental results indicated that the as-prepared materials possessed excellent 3 DOM structure,which is beneficial for the catalytic activity.The sample 3 DOM W-TiO_(2)-20 exhibited the highest activity in ODS process,and the sulfur removal can reach 98%in 6 h.Furthermore,the oxidative product was also analyzed in the reaction process.

Aerobic oxidation assisted by ligand-free palladium catalysts

Aerobic oxidation of electron-rich benzylic and phenyl allylic alcohols was achieved with high yields with only 0.1 mol.% of Pd(OAc)2 catalyst in the absence of any ligand. This procedure was expected to be valuable for realistic industrial-scale applications from both economic as well as environmental points of view.

Regulation of Active Oxygen Species by Grain Boundaries to Optimize Reaction Paths toward Aerobic Oxidations

Aerobic oxidation by using molecular oxygen(O_(2))as the oxidant is highly attractive,in which activating O_(2)to reactive oxygen species(ROS)is a prerequisite.Although some progress has been achieved in regulating ROS by heterogeneous catalysts,the strategies to efficiently control ROS in aerobic oxidation are still urgently desired.Herein,grain boundaries(GBs)in metal oxides are discovered to be able to facilely regulate ROS.Impressively,MoO_(3)nanocrystals with high density of GBs(MoO_(3)-600)deliver a mass activity of 83 mmol g^(-1)h^(-1)in aerobic oxidation of benzyl alcohol,7 and 8 times as high as that of MoO_(3)nanoparticles without GBs and Pt/C,respectively.In addition,the selectivity of benzoic acid is 100%during whole reaction process over MoO_(3)-600.Mechanistic studies reveal that the oxygen atoms at GBs in MoO_(3)-600 are highly active to form·OH radicals with the generation of oxygen vacancies,while the oxygen vacancies are replenished by O_(2).The reaction path directly contributes to the excellent catalytic performance.

Highly Dispersed RuOOH Nanoparticles on Silica Spheres:An Efficient Photothermal Catalyst for Selective Aerobic Oxidation of Benzyl Alcohol

Photothermal catalysis represents a promising strategy to utilize the renewable energy source(e.g.,solar energy)to drive chemical reactions more efficiently.Successful and efficient photothermal catalysis relies on the availability of ideal photothermal catalysts,which can provide both large areas of catalytically active surface and strong light absorption power simultaneously.Such duplex requirements of a photothermal catalyst exhibit opposing dependence on the size of the catalyst nanoparticles,i.e.,smaller size is beneficial for achieving higher surface area and more active surface,whereas larger size favors the light absorption in the nanoparticles.In this article,we report the synthesis of ultrafine RuOOH nanoparticles with a size of 2–3 nm uniformly dispersed on the surfaces of silica(SiOx)nanospheres of hundreds of nanometers in size to tackle this challenge of forming an ideal photothermal catalyst.The ultrasmall RuOOH nanoparticles exhibit a large surface area as well as the ability to activate adsorbed molecular oxygen.The SiOx nanospheres exhibit strong surface light scattering resonances to enhance the light absorption power of the small RuOOH nanoparticles anchored on the SiOx surface.Therefore,the RuOOH/SiOx composite particles represent a new class of efficient photothermal catalysts with a photothermal energy conversion efficiency of 92.5%for selective aerobic oxidation of benzyl alcohol to benzylaldehyde under ambient conditions.

Identification of functionally active aerobic methanotrophs and their methane oxidation potential in sediments from the Shenhu Area,South China Sea

Large amounts of gas hydrate are distributed in the northern slope of the South China Sea,which is a potential threat of methane leakage.Aerobic methane oxidation by methanotrophs,significant methane biotransformation that occurs in sediment surface and water column,can effectively reduce atmospheric emission of hydrate-decomposed methane.To identify active aerobic methanotrophs and their methane oxidation potential in sediments from the Shenhu Area in the South China Sea,multi-day enrichment incubations were conducted in this study.The results show that the methane oxidation rates in the studied sediments were 2.03‒2.36μmol/gdw/d,which were higher than those obtained by sediment incubations from other areas in marine ecosystems.Thus the authors suspect that the methane oxidation potential of methanotrophs was relatively higher in sediments from the Shenhu Area.After the incubations family Methylococcaea(type I methanotrophs)mainly consisted of genus Methylobacter and Methylococcaea_Other were predominant with an increased proportion of 70.3%,whereas Methylocaldum decreased simultaneously in the incubated sediments.Collectively,this study may help to gain a better understanding of the methane biotransformation in the Shenhu Area.

SYNTHESIS AND CATALYTIC PROPERTY OF POLYSTYRENE SUPPORTED PHENYLALANINE SCHIFF BASE COMPLEX OF Mn(Ⅱ) IN AEROBIC OXIDATION OF CYCLOHEXENE

The polystyrene supported phenylalanine Schiff base complex of Mn（Ⅱ） （PS-Sal-Phe-Mn ） was prepared with chloromethylated styrene polymer heads, 2 L-phenylalanine and manganese （Ⅱ） acetate tetrahyrate., The polymeric ligand and the complex were characterized by FT.IR,, small area X-ray photoelectron spectroscopy （XPS）, and ICP-AES. in the presence of the manganese complex, cyclohexene （1） was effectively oxidized by molecular oxygen without reductant. The major products of the reaction were 2.cyclohexen-l-ol （2）, 2-cyclohexen-l-one （3）and 2-cyclohexen-1-hydroperoxide （4）, which was different with typical oxidation of cyclohexene. The influence of reaction temperature and additive for oxidation had been studied. The selectivity of 2-cyclohexen-l-hydroperoxide varied with reaction time and different additives. The mechanism of cyclohexene oxidation had also been discussed.

SYNTHESIS AND CATALYTIC PROPERTY OF POLYSTYRENE SUPPORTED GLUTAMIC ACID SCHIFF BASE COMPLEX OF Mn(Ⅱ) IN AEROBIC OXIDATION OF CYCLOHEXENE

The polystyrene supported glutamic acid Schiff base complex of Mn （ Ⅱ ） （PS-Sal-Glue-Mn） was prepared with chloromethylated styrene polymer beads, 2,4-dihydroxybenzaldehyde, L-glutamic acid and manganese （ Ⅱ ） acetate tetrahyrate. The polymeric ligand and the complex were characterized by FT-IR, small area X-ray photoelectron spectroscopy （XPS） and 1CP-AES. In the presence of the manganese complex, cyclohexene （1） was effectively oxidized by molecular oxygen without reductant. The major products of the reaction were 2-cyclohexen-l-ol （2）, 2-cyclohexen-l-one （3） and 2-cyclohexen-1- hydroperoxide （4）, which was different with typical oxidation of cyclohexene. The influence of reaction temperature and additive for oxidation had been studied. The selectivity of 2-cyclohexen-1-hydroperoxide varied with reaction time and different additives. The mechanism of cyclohexene oxidation had also been discussed.

Synergy in magnetic Ni_(x)Co_(1)O_(y) oxides enables base-free selective oxidation of 5-hydroxymethylfurfural on loaded Au nanoparticles

The base-free aerobic oxidation of 5-hydroxymethylfurfural(HMF) to 2,5-furandicarboxylic acid(FDCA)in water is recognized as an important and sustainable upgrading process for cellulosic carbohydrates.However,selectivity control still remains a challenge.Here,we disclose that the unique synergy in magnetic Ni_(x)Co_(1)O_(y)(x=1,3 and 5) bimetallic oxides can induce reactive oxygen defects and simultaneously stabilize small-sized metallic Au nanoparticles in the Au/Ni_(x)Co_(1)O_(y)catalysts.Such catalytic features render effective adsorption and activation of O_(2),OH and C=O groups,realizing selective oxidation of HMF to FDCA.On a series of magnetic Au/Ni_(x)Co_(1)O_(y)catalysts with almost identical Au loadings(ca.0.5 wt%) and particle sizes(ca.2.7 nm),the variable Ni/Co molar ratios give rise to the tunable electron density of Au sites and synergistic effect between NiO and CoO_(y).The initial conversion rates of HMF and its derived intermediates(i.e., DFF,HMFCA and FFCA) show a volcano-like dependence on the number of oxygen defects(i.e.,O_(2)^(-)and O^(-)) and electron-rich Au0sites.The optimum Au/Ni3Co1Oycatalyst exhibits a highest productivity of FDCA(12.5 mmol_(FDCA)mol_(Au)^(-1)h^(-1)) among all the Au catalysts in the literature and achieves> 99% yield of FDCA at 120℃ and 10 bar of O_(2).In addition,this catalyst can be easily recovered by a magnet and show superior stability and reusability during six consecutive cycling tests.This work may shed a light on Au catalysis for the base-free oxidation of biomass compounds by smartly using the synergy in bimetallic oxide carriers.