砂岩型铀矿石无氧化剂碱法浸出特征

为研究无氧化剂条件下砂岩铀矿碱法溶浸水岩作用过程及铀浸出特征,在实验室开展了蒸馏水浸泡和无氧化剂碱法浸出试验。结果表明,无试剂的水岩作用盐离子综合体及水中天然溶氧作用,可使铀向水中弱迁移;无氧化剂碱法浸出铀迁移强度与HCO3-浓度正相关,HCO3-浓度700～900mg/L是对浸铀影响相对显著的区间;UO2(CO3)22-和UO2(CO3)34-是无试剂和碱法浸出溶解铀的主要存在形式,两者占比与HCO3-浓度和pH相关。缺少氧化作用的碱法浸铀强度较弱,液固比1.5∶1浸出40d铀回收率17.17%～22.37%,且浸出速度衰减较快,这与矿石中的铀以四价占优有关。尽管如此,在碱性地下水体系尤其是碱法地浸退役采区,长时间内铀的迁移仍不可忽视。

无金属和氧化剂温和条件下碱促进的烯胺酮碳-碳双键断裂合成NH2-结构脒类化合物

报道了室温条件下烯胺酮和磺酰叠氮通过碳-碳双键断裂合成N-磺酰基醚类化合物的方法.反应在1,8-二.氮杂双环[5.4.0]十一碳-7-烯(DBU)存在下进行,无需使用任何金属和氧化剂,具有良好的底物适用性.烯胺酮上的15N同位素标记实验证实,磺酰叠氮仅作为产物中的磺酰胺片段供体,同时,该实验也有力地支持反应机理涉及关键的1,2,3-三唑啉中间体的原位形成以及环分解.

Pd/C催化3,4-二氢吡喃酮脱氢制备α-吡喃酮

α-吡喃酮是许多药物和天然产物中存在的重要结构单元,具有广泛的生物活性。本文开发了一种Pd/C催化3,4-二氢吡喃酮类化合物无氧化剂脱氢制备α-吡喃酮类化合物的绿色合成方法,氢气是其唯一副产物。研究表明,在氮气保护下,5 mol%Pd/C作为催化剂,50 mol%Na_(2)CO_(3)作为碱添加剂,130℃反应时,可达到60-88%的收率。该方法无需氧化剂和氢接受体的加入,符合绿色化学的理念。并且,该反应对含有卤素、芳杂环、稠环的底物均有兼容性,催化剂便于回收利用,具有良好的工业化应用潜力。

Influences of process parameters on solvent-free toluene oxidation over Au /γ-MnO_2 catalyst

γ-MnO2 nanorobs and Au/γ-MnO2 catalysts were synthesized and characterized by the X-ray powder diffraction XRD the scanning electron microscope SEM and transmission electron microscope TEM . The characterizations show that Au particles are well dispersed on the surface of γ-MnO2 nanorobs with a particle size of about 10 nm.The catalytic performance is evaluated in solvent-free toluene oxidation with oxygen. The influences of several process parameters such as reaction time reaction temperature initial oxygen pressure and catalyst amounts on the catalytic performance are studied.Catalytic results reveal that Au/γ-MnO2 catalyst has a unique selectivity to benzaldehyde and all these factors greatly influence the conversion of toluene and selectivity of bezaldehyde benzoic acid and benzyl benzoate.However these factors have slight influence on the selectivity of benzyl alcohol.

A binder-free, flexible cathode for rechargeable Na-O_2 batteries

Rechargeable Na-O2 batteries have attracted significant attention as energy storage devices owing to their theoretically high energy storage capacity and the natural abundance of sodium. However, practical applications of this type of battery still suffer from low specific capability, poor cycle sta- bility, instable electrolytes, and unstable polymer binders. Herein, we report a facile method of synthesizing binder free and flexible cathodes with C0304 nanowire arrays vertically grown onto carbon textiles. When employed as a cathode for Na-O2 batteries, this cathode exhibits superior performance, including a reduction of charge overpotential, high specific capacity （4687 mAh/g）, and cycle stability up to 62 cycles. These enhanced performance can be attributed to the synergistic effect of the porosity and catalytic activity of the C0304 nanowire catalyst.

Solvent-free selective oxidation of cyclohexane with molecular oxygen over manganese oxides:Effect of the calcination temperature

The effects of calcination temperature on the physicochemical properties of manganese oxide catalysts prepared by a precipitation method were assessed by X-ray diffraction,N2 adsorption-desorption,X-ray photoelectron spectroscopy,H2 temperature-programmed reduction,O2 temperature-programmed desorption,and thermogravimetry-differential analysis.The catalytic performance of each of these materials during the selective oxidation of cyclohexane with oxygen in a solvent-free system was subsequently examined.It was found that the MnOx-500 catalyst,calcined at 500 °C,consisted of a Mn2O3 phase in addition to Mn5O8 and Mn3O4 phases and possessed a low surface area.Unlike MnOx-500,the MnOx-400 catalyst prepared at 400 °C was composed solely of Mn3O4 and Mn5O8 and had a higher surface area.The pronounced catalytic activity of this latter material for the oxidation of cyclohexene was determined to result from numerous factors,including a higher concentration of surface adsorbed oxygen,greater quantities of the surface Mn4＋ ions that promote oxygen mobility and the extent of O2 adsorption and reducibility on the catalyst.The effects of various reaction conditions on the activity of the MnOx-400 during the oxidation of cyclohexane were also evaluated,such as the reaction temperature,reaction time,and initial oxygen pressure.Following a 4 h reaction at an initial O2 pressure of 0.5 MPa and 140 °C,an 8.0% cyclohexane conversion and 5.0% yield of cyclohexanol and cyclohexanone were achieved over the MnOx-400 catalyst.In contrast,employing MnOx-500 resulted in a 6.1% conversion of cyclohexane and 75% selectivity for cyclohexanol and cyclohexanone.After being recycled through 10 replicate uses,the catalytic activity of the MnOx-400 catalyst was unchanged,demonstrating its good stability.

Selective suppression of toluene formation in solvent-free benzyl alcohol oxidation using supported Pd-Ni bimetallic nanoparticles

The solvent‐free oxidation of benzyl alcohol was studied using supported Pd‐Ni bimetallic nanoparticles.Compared with monometallic Pd,the addition of Ni to Pd was found to be effective in suppressing the nondesired product toluene,thereby enhancing the selectivity towards benzaldehyde.This result was attributed to a dual effect of Ni addition:the weakening of dissociative adsorption of benzyl alcohol and the promotion of oxygen species involved in the oxidation pathway.

Mechanism study of organic antioxidant and inorganic salt on suppressing coal oxidation

The advantages and disadvantages of organic antioxidant and inorganic salt on suppressing coal oxidation were analyzed on the basis of the theory that coal oxidation mechanisms can be attributed to the free radical chain-type reaction mechanism. The inhibition curves on suppressing coal oxidation of the different type and different concentration of organic antioxidant and inorganic salt were given through experimental study and data processing. Then some conclusions can be gained from the experimental study combining with theoretical analysis. First the inhibition mechanism of the organic antioxidant and inorganic salt is different. The former is that the chemical action is the dominant position. It can be called as the chain termination theory because the free radical is captured during coal oxidation. And the later is that the physical effect is the dominant position. It can be called as the decreasing-temperature theory because the liquid membrane which was formed by the inorganic salt can make coal body be the state of wetness and prevent oxygen from coal surface. Second the inhibition effect of the organic antioxidant is higher than the inorganic salt in the later period. But it is lower in the early period.

Simple synthesis of nitrogen‐doped carbon spheres as a highly efficient metal‐free electrocatalyst for the oxygen reduction reaction

In the present work, nitrogen‐doped carbon spheres were synthesized through a simple hydro‐thermal treatment using glucose and melamine as inexpensive carbon and nitrogen sources, re‐spectively. The ratio of melamine to glucose and annealing temperature were optimized. The final optimal sample exhibited a catalytic activity for the oxygen reduction reaction（ORR） that was supe‐rior than that of commercial 20%Pt/C in 0.1 mol/L KOH. It revealed an onset potential of –22.6 mV and a half‐wave potential of –133.6 mV （vs. Ag/AgCl）, which are 7.2 and 5.9 mV more positive than those of the 20%Pt/C catalyst, respectively, as well as a limiting current density of 4.6 mA/cm^2, which is 0.2 mA/cm^2 higher than that of the 20%Pt/C catalyst. The catalyst also exhibited higher stability and superior durability against methanol than 20%Pt/C. Moreover, ORRs on this catalyst proceed through a more effective 4 e^– path. The above mentioned superiority of the as‐prepared catalyst makes it promising for fuel cells.

Selective oxidation of glycerol in a base-free aqueous solution: A short review

Catalytic transformation of glycerol to value-added products has attracted the attention of scientists all over the world. Among various transformations, selective oxidation of glycerol with molecular oxygen to dihydroxyacetone, glyceric acid, glyceraldehydes, and tartronic acid is challenging both from the viewpoint of academic research and industrial application. Herein, we review the recent progresses in the selective oxidation of glycerol under base-free conditions. Those catalysts widely reported for the selective oxidation of the terminal hydroxyl and secondary hydroxyl groups in glycerol, such as monometallic Au, Pt, and Pd NPs, and bimetallic Au-Pt, Au-Pd, Pt-Bi, Pt-Sb, and Pt-Cu, were compared and discussed in detail. The reaction mechanism over Pt-based catalysts, possible catalyst deactivation, and the corresponding improvements are presented. Further, the recent progresses in the continuous oxidation of glycerol in fixed bed reactors and its excellent selectivity in the formation of dihydroxyacetone are highlighted.

Nanoscale graphene oxide sheets as highly efficient carbocatalysts in green oxidation of benzylic alcohols and aromatic aldehydes

Nanoscale graphene oxide(NGO)sheets were synthesized and used as carbocatalysts for effectiveoxidation of benzylic alcohols and aromatic aldehydes.For oxidation of alcohols in the presence ofH2O2at80°C,the NGOs(20%mass fraction)as carbocatalysts showed selectivity toward aldehyde.The rate and yield of this reaction strongly depended on the nature of substituents on the alcohol.For4‐nitrobenzyl alcohol,<10%of it was converted into the corresponding carboxylic acid after24h.By contrast,4‐methoxybenzyl alcohol and diphenylmethanol were completely converted into thecorresponding carboxylic acid and ketone after only9and3h,respectively.The conversion ratesfor oxidation of aromatic aldehydes by NGO carbocatalysts were higher than those for alcohol oxidation.For all the aldehydes,complete conversion to the corresponding carboxylic acids wasachieved using7%(mass fraction)of NGO at70°C within2–3h.Possible mechanisms for NGOcarbocatalyst structure‐dependent oxidation of benzyl alcohols and structure‐independent oxidationof aromatic aldehydes are discussed.

Corrosion resistance improvement of Ti-6Al-4V alloy by anodization in the presence of inhibitor ions

Colorful thin oxide films were synthesized by galvanostatic anodization on Ti−6Al−4V alloy.Three different aqueous solutions containing corrosion inorganic inhibitors(Na_(2)MoO_(4),NaH_(2)PO_(4) and NH4VO3)were employed for the anodization treatment.The effect of inhibitor anions on the corrosion behavior of the alloy in Ringer solution was studied.Open circuit potential(OCP),Tafel polarization,linear sweep voltammetry(LSV)and chronoamperometry(CA)were performed to evaluate the corrosion performance of the treated electrodes.The incorporation of the inhibitor ions was detected by the release of Mo,V and P through ICP-AES technique.The formed oxides were characterized by scanning electron microscopy(SEM),X-ray diffraction(XRD)and X-ray photoelectron spectroscopy(XPS).The results show that compact,amorphous oxides without pores or cracks were obtained independently of the solution used.The sample anodized in Na_(2)MoO_(4) solution registered the lowest corrosion current density(0.11μA/cm^(2)),and it was able to protect the alloy even after 168 h of immersion in Ringer solution.No cracks or corrosion products were detected.The XPS analysis reveals the incorporation of molybdenum to the oxide film in the form of Mo^(6+) and Mo^(4+).

Structured binder‐free MWW‐type titanosilicate with Si‐rich shell for selective and durable propylene epoxidation

Selective and durable fixed‐bed catalysts are highly desirable for developing eco‐efficient HPPO(hydrogen peroxide propylene oxide)process.The powder titanosilicate catalysts must be shaped before being applied in industrial processes.As the essential additives for preparing formed catalysts,binders are usually the catalytically inert components,but they would cover the surface and pore mouth of zeolite,thereby declining the accessibility of active sites.By recrystallizing the binder(silica)/Ti‐MWW extrudates with the assistance of dual organic structure‐directing agents,the silica binder was converted into MWW zeolite phase to form a structured binder‐free Ti‐MWW zeolite with Si‐rich shell,which enhanced the diffusion efficiency and maintained the mechanical strength.Meanwhile,due to the partial dissolution of Si in the Ti‐MWW matrix,abundant silanol nests formed and part of framework TiO4 species were transferred into open TiO_(6)ones,improving the accumulation and activation ability of H_(2)O_(2)inside the monolith.Successive piperidine treatment and fluoridation of the binder‐free Ti‐MWW further enhanced the H_(2)O_(2)activation and oxygen transfer ability of the active Ti sites,and stabilized the Ti‐OOH intermediate through hydrogen bond formed between the end H in Ti‐OOH and the adjacent Si‐F species,thus achieving a more efficient epoxidation process.Additionally,the side reaction of PO hydrolysis was inhibited because the modification effectively quenched numerous Si‐OH groups.The lifetime of the modified binder‐free Ti‐MWW catalyst was 2400 h with the H_(2)O_(2)conversion and PO selectivity both above 99.5%.

Efficient Solvent-free Synthesis of Chloropropene Carbonate from the Coupling Reaction of CO_2 and Epichlorohydrin Catalyzed by Magnesium Porphyrins as Chlorophyll-like Catalysts

Highly efficient solvent-free coupling reaction of carbon dioxide(CO2)and epichlorohydrin catalyzed by meso-tetraphenyl porphyrin magnesium(MgTPP)in the presence of triethylamine as co-catalysts is reported.As a chlorophyll-like catalyst,MgTPP showed excellent activity for the coupling reaction of CO2 and epichlorohydrin to chloropropene carbonate,in which the turnover number could reach up to 9200.Moreover,different factors including the amount of catalyst,reaction temperature,pressure and time were systematically investigated and the optimal reaction conditions were obtained(epichlorohydrin 50 mmol,MgTPP 5.0×10- 3mmol,triethylamine 6.25×10-3 mmol,140°C,1.5 MPa,8 h).A plausible two-pathway mechanism for the coupling reaction of CO 2and epichlorohydrin is proposed to propound the catalysis of MgTPP.

Macrokinetics of Ethylene Epoxidation over A-type Silver Catalyst

By taking the surface chemical reactions as the rate-controlling step, a possible reaction mechanism for ethylene epoxidation to synthesize ethylene oxide over the A-type silver catalyst was developed, while it was assumed that the epoxidation reaction would take place between ethylene and the un-dissociated adsorbed oxygen O2 a on the solo active sites, while the deep oxidation would occur between ethylene and the dissociated adsorbed oxygen Oa on the adjacent multi-active sites. In order to describe the effect of 1,2-C2H4Cl2(EDC) inhibitor on the ethylene epoxidation process, the reversible reactions between EDC and vinyl chloride(VC) on the active sites of silver catalyst was introduced. According to the assumed mechanism, the hyperbolic macro-kinetic model of ethylene epoxidation over the A-type silver catalyst was established, and the macrokinetic experiments were carried out in an internal-recycle gradientless reactor operating at a pressure of 2.1 MPa and a temperature in the range of 217.8—249.0 ℃, with the gas composition(molar fraction) consisting of 15.82%—34.65% C2H4, 2.55%—7.80% O2, 0.88%—6.15% CO2, 0.15—2.61 μmol/mol of 1,2-C2H4Cl2 and 0.14—1.28 μmol/mol of C2H3 Cl. By means of the Simplex Optimal Method, the parameters of the macrokinetic models were estimated. Statistical test showed that the macrokinetic models developed for the A-type silver catalyst agree well with the experimental results.

三乙胺促进的α-卤代酮C—C键断裂:合成α-乙酰氧基芳基酮（英文）

C-C键断裂在有机合成中有着重要的作用.报道了一种胺促进的α-卤代酮化合物C-C键断裂的新方法,该方法无需使用过渡金属催化剂以及氧化剂.采用这种方法以廉价的α-卤代酮化合物制备了多种α-乙酰氧基芳基酮化合物.

Green and efficient cycloaddition of CO2 toward epoxides over thiamine derivatives/GO aerogels under mild and solvent-free conditions

Thiamine derivatives that are cheap, readily available, non-toxic and green are used as heterogeneous catalyst for the generation of cyclic carbonates through cycloaddition of CO_2 to epoxides without the need of co-catalyst and solvent. The interaction between thiamine hydrochloride(VB_1-Cl) and substrates(CO_2 and propylene oxide) was proven by ultraviolet-visible spectroscopy and ~1H nuclear magnetic resonance analysis, and it is deduced that the synergistic action among multi-functional groups(hydroxyl, halide anion and amine) is a favorable factor for cycloaddition reaction. A series of VB_1/GO aerogels were facilely prepared through the addition of aqueous VB_1 derivatives to a suspension of GO in ethanol at room temperature. It was found that the aerogel generated through the interaction of VB_1-Cl with GO shows catalytic activity and stability higher than those of VB_1-Cl. It is because the electrostatic interaction between GO and VB_1-Cl enhances the nucleophilicity and leaving ability of anion. The effects of reaction temperature, catalyst loading, CO_2 pressure and reaction time on CO_2 cycloaddition to propylene oxide were thoroughly studied.

Binder-free S@Ti_(3)C_(2)T_(x)sandwich structure film as a high-capacity cathode for a stable aluminum-sulfur battery

The rechargeable aluminum-sulfur(Al-S)battery is a promising alternative-energy storage device with high energy density and made of cheap raw materials.However,Al-S batteries face several obstacles,especially the shuttle effect.Herein,a binder-free S@Ti_(3)C_(2)T_(x)sandwich structure film with uniform sulfur dispersion was designed.The two-dimensional(2D)layered material Ti_(3)C_(2)T_(x) not only has the function of binder and conductive agent but also is a promising host for sulfur anchoring.As a result,S@Ti_(3)C_(2)T_(x)film showed an initial capacity of 489 mA h g^(−1)at 300 mA g^(−1) and retained the value at 415 mA h g^(−1)after 280 stable cycles,with an average Coulombic efficiency of~95%.The film displayed higher capacity and stability than the S+Ti_(3)C_(2)T_(x)cathode prepared by the slurry-coating method(the initial capacity was 317 mA h g^(−1)and then decayed to 222 mA h g^(−1) after 160 cycles).The main capacity of S@Ti_(3)C_(2)T_(x) film in the Al-S battery came from the reversible redox reaction of S^(2−) and S.This new 2D material combined with a controllable electrode structure design paves the way for the development of Al-S batteries.

Boron-doped amorphous iridium oxide with ultrahigh mass activity for acidic oxygen evolution reaction

Oxygen evolution reaction(OER), as the primary anodic reaction, plays a critical role in many electrochemical energy conversion processes. As the state-of-the-art OER catalysts, iridium-based materials are largely hindered from practical applications mainly due to the extreme scarcity of iridium. Here we demonstrate the successful fabrication of boron-doped amorphous iridium oxide(IrO_(x)-B) via a facile boric acid-assisted method, which realizes an ultrahigh OER mass activity of 2779 A g^(-1)Irat 300 mV overpotential, representing one of the best acidic OER catalysts reported so far.It is found that boric acid can not only facilitate the exposure of Ir, but also dope the amorphous IrOxwith a form of metaborate, which could further modify the electronic and local ligand structure of Ir for the improved intrinsic activity. Interestingly, the reported strategy is universal that can be applied to improve other metal oxide OER catalysts, highlighting a versatile strategy for creating high-performance electrocatalysts with ultrahigh mass activity for OER and beyond.

Facile and efficient one-pot synthesis of 2-arylbenzoxazoles using hydrogen tetrachloroaurate as catalyst under oxygen atmosphere

In this paper, we presented a novel method for the facile and efficient one-pot synthesis of 2-arylbenzoxazoles, which were directly synthesized from 2-aminophenol and aldehydes catalyzed by hydrogen tetrachloroaurate (HAuCl4·4H2O) under an oxygen atmosphere with anhydrous tetrahydrofuran (THF) as solvent or in solvent-free condition. The results show that this method could bring excellent yields as high as 96%. THF was proven to be the best choice among several solvents screened and the reaction was tolerated with a variety of aromatic aldehydes possessing electron-donating or withdrawing groups. The advantages of the present method lie in catalytic process using economic and environmentally benign dioxygen as oxidant.