电化学氧化法制取烟酸的研究进展

介绍了直接电氧化法和间接电氧化法制取烟酸的原料及相应的电极反应,同时对直接电氧化法制取烟酸的电解槽、电极材料、离子交换膜及支持电解质等的研究进展进行了评述。直接电氧化法多采用Pt、PbO2和PbO2/Ti为阳极,Pb和Ni为阴极,离子交换膜为隔膜,电流效率可达70%。     

Chemo-enzymatic synthesis of disaccharide fatty acid esters

A novel enzymatic method for the synthesis of disaccharide fatty acid esters was developed with immobilizedMucor miehei lipase (Lipozyme IM-60; Novo Nordisk, Bagsvaerd, Denmark) as a catalyst. A range of lactose and maltose monoesters was prepared in overall yields of 48–77% from the corresponding sugar acetals and fatty acids.     

Desulfurization of gasoline by a new method of electrochemical catalytic oxidation

A new deep desulfurization process for gasoline was obtained by means of electrochemical catalytic oxidation with an electrochemical fluidized-bed reactor on particle group anode. The particle group anode was activated carbon-supported cerium dioxide (CeO₂/C), and the electrolyte was aqueous cerium nitrate solution, and copper pillar was cathode in the electrochemical reactions. The CeO₂/C particle group anode could remarkably accelerate the electrochemical reaction rate and promote the electrochemical catalysis performance for the electrochemical desulfurization reaction. Thermodynamics feasibility analysis clarified that the theoretical decomposition voltage ranged from 0.1–0.5 V in pure acid electrolyte system and desulfurization reactions could not spontaneously carry out, but the reactions were spontaneous when aqueous cerium nitrate solution serves as electrolyte. And the rule of the gasoline desulfurization by the means of electrochemical catalytic oxidation was investigated. The experimental results indicated that the optimal desulfurization conditions were as follows: the cell voltage, concentration of the Ce³⁺ ions, feed volume flow rate and the CeO₂ percentage by weight were 3.2 V, 0.08 mol l⁻¹, 300 ml min⁻¹ and 5.0 wt%, respectively. Under these conditions the concentration of sulfur in gasoline was reduced from 310 to 50 parts per million by weight (ppmw). Based on these experimental results, a mechanism of indirect electrochemical oxidation was also proposed.     

电化学氧化法处理生活污水的研究

采用电化学氧化法处理生活污水,探讨了电解质浓度、电流密度、pH值、反应温度、不同电极等对COD、浊度的影响。实验表明,处理水中COD、浊度的最佳条件是:电解质浓度为45 g/L,pH值为8,电流密度为60 mA/m2,温度为22℃,阳极为RuSn电极,阴极使用不锈钢电极。此时COD去除率达86.22%,浊度去除率达80%,悬浮固体去除率和细菌去除率94%和99%。     

Synthesis of fluorocyclohexadienes by the electrochemical fluorination of p-difluorobenzenes on a preparative scale

Fluorine containing-cyclohexadienes (FCHDs), 3,3,6,6,-tetrafluoro-1,4-cyclohexadiene (1a), 1-chloro-3,3,6,6-tetrafluoro-1,4-cyclohexadiene (3a) and 1-bromo-3,3,6,6-tetrafluoro-1,4-cyclohexadiene (4a), were isolated in pure states with high yields (ca. 80%) by the preparative scale electrochemical fluorination of 1,4-difluorobenzene (1), 1-chloro-2,5-difluorobenzene (3) and 1-bromo-2,5-difluorobenzene (4), respectively, in Et₄NF · mHF (Et = C₂H₅: m = 4.0, 4.45 and 4.7) at a platinum anode, followed by extraction and fractional distillation. The electrochemical fluorination of 1,2,4-trifluorobenzene (2) yielded both 1,3,3,6,6-pentafluoro-1,4-cyclohexadiene (2a) and 2,5,5,6,6-pentafluoro-1,3-cyclohexadiene (2b) with high yield (ca. 90%). Some of (2a) was also isolated in a pure state by fractional distillation. Each substrate compound (1–4) was fluorinated to the corresponding FCHDs with an almost quantitative yield when 2.0–2.1 faraday (per mol of substrate) of electricity was passed.     

Degradation of azo dye by three clean advanced oxidation processes: Wet oxidation, electrochemical oxidation and wet electrochemical oxidation—A comparative study

This work compared the degradation behaviors of an azo dye, cationic red X-GRL, by three clean advanced oxidation processes: wet oxidation (WO), electrochemical oxidation (EO) and wet electrochemical oxidation (WEO). It was found that the WO process was readily to remove color while the EO process was prone to decompose pollutants. Integrated with the advantage of two processes, the WEO process posed synergetic effects for both efficient removal of color and COD. Even at the low temperature of 120 °C, the color could be almost completely removed at 60 min, and the COD removal was about 43.2% at 120 min, which was greatly protomted from that by WO at similar conditions (about 7.8%). And it demonstrated a better performance under a reduced temperature and a wider dye concentration range, representing the most promising alternative for environmental application among the three processes. The main degradation products for three processes were detected and a simplified five-stages degradation pathway was suggested, which indicated that the WEO process mineralized much more completely than the other two processes.     

Facile and clean electrochemical synthesis of new acetaminophen derivatives through electrochemical oxidation of acetaminophen in the presence of thiouracil derivatives

The electrochemical oxidation of acetaminophen (1a) is carried out in the presence of thiouracil derivatives (3a–c), as nucleophiles, in an acetate buffer solution (0.15?M, pH 5) mixed with Dimethylformamide (DMF) using cyclic voltammetry and coulometry under a constant potential. The results obtained indicate that N-acetyl-p-benzoquinone-imine derived from acetaminophen participates in a 1,4-Michael-type addition reaction with thiouracils to form the corresponding acetaminophen derivatives (4a–c) in good yields and with high purities using a facile, catalyst-free, and one-pot electrochemical method using three carbon electrodes in an undivided cell under mild conditions. The products obtained were characterized after purification by IR, ¹H NMR, and ¹³C NMR spectroscopies, and by the elemental analysis method.     

分子氧化及光电催化氧化对石油Pickering乳液的破乳研究进展

石油开采、集输、加工过程中会面临复杂的工况条件,原油中的天然表面活性剂与人工添加乳化剂以及纳微米固体颗粒共同形成石油Pickering乳液,使得油水体系呈稳定的水包油（O/W）、油包水（W/O）或多重乳化状态。油水乳状液作为注水采油的主要产物,其高效破乳是石油工业链条中的普遍需求。目前对于石油Pickering的破乳仍然借鉴普通油水乳液的方法,而对于成因复杂的油水乳状液,以去除成膜乳化剂为目标的氧化破乳法比传统破乳法的效果更佳。为此,本文基于高效的氧化破乳机制,介绍了石油Pickering乳液的特点及危害,与非氧化反应类型的传统化学破乳法进行对比,综述了分子氧化、光催化氧化、电化学氧化三类技术对于不同来源及特征的油水乳状液的破乳进展。通过对每种方法的机理过程、应用实例、优缺点等方面详细分析,总结了分子氧化、光催化氧化、电化学氧化在石油Pickering乳液破乳中的局限性,并对今后如何实现石油Pickering乳液精准破乳提出展望。     

Biological and electrochemical oxidation of naphthalenesulfonates

A biofilm airlift suspension (BAS) reactor and an undivided flow cell equipped with a boron‐doped diamond (BDD) anode and a stainless‐steel cathode were used to investigate the effects of varying operating conditions on process performance in the biological and electrochemical oxidation of a mixture of naphthalenesulfonates contained in the infiltration water of a contaminated industrial site. The experiments were aimed at evaluating the feasibility of process integration and the criteria for optimization (i.e. how to maximize degradation efficiency with minimum energy consumption) in combined biological and electrochemical oxidation of scarcely biodegradable compounds. Because of high reactor biomass concentration and long biomass retention time, the BAS reactor achieved a high degradation capacity (up to 6.8 kg COD m^?3 d^?1). On the other hand, owing to the recalcitrant character of some of the aromatic sulfonates in the leachate, the overall degradation efficiency did not exceed 70% based on COD measurements. All naphthalene‐mono‐ and ‐disulfonates (except naphthalene‐1,5‐disulfonate) were completely degraded in the BAS reactor, whereas more complex molecules (e.g. naphthalenetrisulfonates) were more recalcitrant to biological oxidation. These compounds were completely mineralized by electrochemical oxidation using a boron‐doped diamond anode. The energy consumption and the time required for the complete mineralization of the infiltration water decreased from 80 kWh m^?3 and 4 h to 61 kWh m^?3 and 3 h for the oxidation of raw and biologically pretreated leachate, respectively. Copyright © 2005 Society of Chemical Industry     

Generation of oxysterols formed by free radicals and enzymes by electrochemical oxidation

It is commonly accepted that cholesterol oxide derivatives, also named oxysterols, are 27 carbon‐atom molecules deriving either from enzymatic and non‐enzymatic oxidation of cholesterol. Most of these compounds can be synthesized by more or less difficult and time consuming chemical reactions, and some of them have been discovered before the identification of the enzymes [mainly cytochrome P450 enzymes (CYP enzymes)] involved in their biosynthesis. A wide range of biological activities depends on oxysterols. Some oxysterols are also involved in the synthesis of cholesterol metabolites which have various properties. The paper by Weber et al. in this issue of European Journal of Lipid Science and Technology is of interest because it reports that an electrochemical oxidation of cholesterol rapidly generates numerous oxysterols which are usually generated either by enzymatic processes in vivo or under the action of different chemical and physical agents (free radicals, sun light, …) in vivo or not. This has a crucial importance and suggests that the border between enzymatic and non‐enzymatic generation of oxysterols should be reconsidered, at least for some of these compounds. Consequently, these observations may have major chemical and physiopathological significance.     

Preparative scale isocratic chromatographic purification of a polyethylene mono-alcohol accompanied by high resolution evaluation of molecular weight distribution

A simple preparative-scale adsorption chromatographic method for separating a commercially available polyethylene mono-alcohol from its non-functional polyethylene impurities has been established using silica as the stationary phase and toluene at 75°C as the isocratic eluant. Characterization of the chromatographic fractions by ¹H-NMR spectroscopy also provided unexpected comprehensive information on the molecular structure and molar mass distribution of the polyethylene mono-alcohol. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

The electrochemical oxidation of phenylenediamines

Five p-phenylenediamines were oxidized electrochemically at a glassy carbon rotating ring-disk-electrode assembly. The overall reaction comprises the transfer of two electrons per molecule. At low to intermediate potentials the rate determining step for all the five compounds is the acid dissociation of the semiquinonediimine radical cation formed in a pre-equilibrium involving the transfer of one electron. Only at higher potentials can the radical cation be oxidized in parallel to the neutral semiquinone radical to form the quinonediimines. In contrast, the neutral semiquinonediimine radicals are oxidized at the same or even a lower potential than the parent phenylenediamines. The dissociation rate constants of the radical cations are in the range of 10-300 s⁻¹. The effect of the substituents on the oxidation potentials is as expected by their property to donate electrons to the mesomeric system. Their effect on the dissociation rates, however, seems to rather correlate with the inductive effect and might influence not only the electronic structure of the molecule itself but also the structure of the ions and the solvent around them. The semiquinonediimine radical cations are found to be slightly more acidic than their protonated parent phenylenediamine cations with pK_a values somewhat below 6.     

Anodic oxidation of N-anions. III. Anodic oxidation of the N-anions of diacylimides: A search for a new electrochemical synthesis of hydrazine

The anodic oxidation of N-anions of diacylimides which are acidic enough to be deprotonated by relatively weak bases in protic solvents was investigated with respect to the electrode kinetics and preparative aspects. All imide anions are oxidized in a one-electron step to the respective imide radicals. Of the imides investigated, two were cyclic carboxylic imides (succinimide and phthalimide) three were sulphonyl imides (di-p-toluene and di-benzene sulphimide, dimethane sulphimide) and one was a mixed carboxylate-sulphonate imide (saccharate). The imide radicals produced by anodic oxidation of the dicarboxylate imides do not couple to form a hydrazine derivative but induce solvent oxidation by H-abstraction. The disulphonyl imides couple to unstable hydrazine derivatives although H-abstraction occurs to more than 80%. Only the anodic coupling of the N-anion of imido-disulphonic acid to hydrazine tetrasulphonate discovered by Grinstead [3] can be performed with good selectivity and current and mass yields. The optimum conditions for this reaction are determined in order to show that it may serve in the future as one step in a new hydrazine process.For parts I and II see [1] and [2].     

The electrochemical synthesis of polyaniline/polysulfone composite films and electrocatalytic activity for ascorbic acid oxidation

Polyaniline (PANI)/polysulfone (PSF) composite films with asymmetric porous structure were successfully prepared by electropolymerization. The back face (in contact with the electrode) of the freestanding composite film is green while the outer face is white. The chemical component and the morphology of the surfaces were characterized by FTIR spectra and scanning electron microscopy, respectively. It was shown that replicate films gave reproducible voltammetry in 0.5 M H₂SO₄. The influence of the electrolyte and the acidic concentration on the redox peak currents of polyaniline were investigated in detail. The composite film electrode showed good electrocatalytic activity for ascorbic acid, which the anodic overpotential was evidently reduced compared with that obtained at bare Pt electrode. The diffusion coefficient of ascorbic acid was 1.38 × 10⁻⁶ cm² s⁻¹.     

电极材料对木质素磺酸盐电氧化效果影响的研究

用C、Ti合金和PbO2电极对木质素磺酸盐进行电氧化．结果表明，C和Ti合金作为阳极，氧化能力弱，氧化效果不显著；PbO2电极氧化木质素磺酸钠，效果明显，氧化前后，其IR，UV和1H－NMR谱图发生显著变化，－COOH含量升高，苯环结构被破坏。其数均分子量随氧化电量的增加而有一个上升到降低的过程，说明电氧化过程中聚合与降解反应共存。电氧化能改善木质素横酸盐作为水泥添加剂的分散性能。     

One-step large-scale synthesis of micrometer-sized silver nanosheets by a template-free electrochemical method

We have synthesized micrometer-sized Ag nanosheets via a facile, one-step, template-free electrochemical deposition in an ultra-dilute silver nitrate aqueous electrolyte. The nanosheet growth was revealed to occur in three stages: (1) formation of polygonal Ag nuclei on a substrate, (2) growth of {112}-faceted nanowire from the nuclei, and (3) anisotropic growth of (111)-planar nanosheets, approximately 20 to 50 nm in thickness and 10 μm in width, in the <112>−direction. The vertical growth of the facet nanowire was induced by the strong interface anisotropy between the deposit and electrolyte due to the ultra-dilute concentration of electrolyte and high reduction potential. The thickness of Ag nanosheets was controllable by the adjustment of the reduction/oxidation potential and frequency of the reverse-pulse potentiodynamic mode.     

电化学氧化法预处理垃圾渗滤液的研究

通过电化学氧化法对垃圾渗滤液进行预处理,用正交实验方法确定最佳的反应条件,对处理前后的有机组成进行GCMS分析。结果表明,较佳电氧化条件为:处理时间120 min,电流密度7.5 A/dm2,极板间距5 mm,阳极板材为SnO2/Ti,阴极为不锈钢,NaCl投加量为2 g/100 mL。在此条件下,当进水COD浓度为44 100 mg/L时,出水浓度为1 369 mg/L,去除率达到68.94%,氨氮进水浓度为4 085 mg/L时,出水浓度为1 209 mg/L,去除率达到了70.4%。有机物的去除明显,挥发性有机物增多,能够达到对高浓度垃圾渗滤液进行预处理并有利于后续的生化处理的目的。     

Characterisation of surface oxidation of nickel-titanium alloy by ion-beam and electrochemical techniques

The passivating effects produced on Ni₄₉Ti₅₁ (at.%) shape memory alloy by electropolishing in methanol-sulphuric acid electrolyte or thermal treatment in air are investigated with ion-beam techniques (secondary ion mass spectrometry (SIMS) and mass resolved ion scattering spectrometry (MARISS)) and electrochemical techniques (polarisation curves, photocurrent spectroscopy and impedance). Electropolishing produces a limited passivation due to formation of a thin layer of amorphous TiO₂, which causes only a slight hindrance to the oxygen evolution reaction. Thermal treatment in air at 450 °C causes a more substantial passivation due to formation of a thick oxide layer, estimated at about 80 nm for a 16 h treatment on the basis of weight increase, disregarding roughness. Data indicate that the film produced by thermal oxidation has probably a duplex structure, with a porous outer layer with inclusions of Ni species and a compact inner layer, in contact with the substrate, consisting of (essentially) nickel free TiO₂ rutile.