1,4-二氯苯在乙腈-水两相系统中的电化学氧化降解途径

研究了乙腈-水两相中Pt电极上1,4-二氯苯的降解途径和氧化特性。实验结果表明,1,4-二氯苯在乙腈-水两相中的氧化电位区间约为2.0～2.3 V(vs SCE),且氧化反应是受扩散控制的不可逆过程。液相色谱、液相色谱-质谱联用、离子色谱等的分析结果表明,乙腈-水两相中1,4-二氯苯氧化中间产物包括对氯苯酚、对苯醌、2,5-二氯对苯醌、草酸根离子、乙酸根离子、甲酸根离子、顺丁烯二酸根离子和氯离子,最终产物为H_2O和CO_2。得出了1,4-二氯苯主要的降解途径有两种。     

3,4-二氯甲苯氨氧化法制备3,4-二氯苯腈

采用气相氨氧化法,在DN120号催化剂作用下,由3,4-二氯甲苯制备了3,4-二氯苯腈(DCBN).考察了反应温度、物料摩尔比和进料量Qv对反应的转化率、摩尔产率和选择性的影响.确定最佳反应条件为:反应温度400℃、物料摩尔比nDCT∶nNH3∶nair=1∶7∶30、进料量Qv=0.6 mL·h-1.在此条件下,使用DN120号催化剂连续反应300 h,DCBN平均摩尔产率为85.3%.     

2，4-二氯苯氧乙酸臭氧化过程中过氧化氢的生成

引言2,4-二氯苯氧乙酸(2,4-D,又名2,4-滴)是一种广泛使用的除草剂[1],应用历史较长,是我国主要的除草剂品种之一,用量也比较大。2,4-D属于苯氧羧酸类除草剂的一种,可有效去除阔叶杂草,目前仍广泛用于农作物除草和草坪养护[2]。2,4-D的水溶性较高,挥发性较低,在自然界中难以生物     

2,4-二氯苯腈的合成

我们在完成氨氧化法制备邻氯苯腈、2,6-二氯苯腈的研究基础上,从价廉易得的2,4-二氯甲苯(以下简称DCT)出发,采用氨氧化法,一步制得2,4-二氯苯腈(以下简称DCBN).其衍生物,如2,4-二氯苯甲酸、2,4-二氟苯腈、2,4-二氟苯甲酸、2,4-二氟苯甲酰胺及2,4-二氟苯胺等均是重要的有机中间体,可广泛地应用于医药、农药、染料、工程塑料和感光材料等行业.其合成路线如下:     

3,4-二氯苯腈的合成

3,4—二氯苯腈及其衍生物广泛应用于农药、医药、颜料、染料等行业[1～ 5 ] 。文献报道 3,4—二氯苯腈的合成方法主要有 :1 .由α,α,α,3,4—五氯甲苯与 NH4Cl反应合成 [6 ] ;2 .由 3,4—二氯苯甲酰胺在 H2 SO4中脱水成腈 [7] ;3.由 3,4—二氯苯甲醛肟脱水制备 [8] ;4 .由 3,4—二氯甲苯在催化剂作用下经氨氧化反应制得 [9]。前 3种方法存在原料昂贵、污染严重等缺点 ,难以实现工业化 ;第4种方法是目前制备芳腈类化合物的最佳方法 ,关键是找到高活性、高选择性的催化剂。文献 [9] 报道用 ( NH4) 2 [( VO) 3( P2 O7) 2 ]作为氨氧化催化…     

2-甲基-1,4-萘醌合成工艺改进

以正己烷为溶剂,Cr6 /Cr3 为氧化介质,间接电氧化2-甲基萘得到2-甲基-1,4-萘醌(2-MNQ)和6-甲基-1,4-萘醌(6-MNQ)的混合物,分离出水相后,用亚硫酸氢钠水溶液处理有机相, 6-MNQ与亚硫酸氢钠优先反应,生成加成产物溶解在水相,溶解在有机相中的2-MNQ经结晶和精制,得到2-MNQ产品.通过优化工艺条件和采用改进的分离提纯方法,2-MNQ的收率可达72.5%以上,质量分数大于99.5%,回收得到的6-MNQ可以转化为相应的蒽醌加以利用.     

2-(2,4-二氯苯氧基)-三乙胺的合成

在相转移催化条件下,首先用2,4-二氯苯酚与二氯乙烷反应制得1-氯-2-（2,4-二氯苯氧基）乙烷中间体,然后再与二乙胺反应,合成植物生长调节剂2-（2,4-二氯苯氧基）-三乙胺。其总收率为84．6％,含量为98．0％。     

环氧化反式- 1,4-聚异戊二烯的合成

以负载钛催化异戊二烯本体沉淀聚合所合成的粉状反式-1,4-聚异戊二烯(TPI)为原料,过氧乙酸水溶液为介质,研究了水相悬浮法合成环氧化TPI(ETPI)的合成条件及动力学特性,并考察了ETPI的环氧度测定方法和反应残液的回收利用问题.结果表明,用该法合成ETPI适宜的反应条件为体系pH值等于4.5,且于约20℃反应1～3 h,可获得环氧度小于50%的ETPI;聚合动力学特性为过氧乙酸参与了环氧化反应,过氧乙酸的生成反应可忽略不计,反应的活化能为(72±5)KJ/mol,ETPI的环氧度可由反应前后过氧乙酸浓度的变化求得,与核磁共振法测得的环氧度相比,误差为±10%,有利于环氧度的控制.     

在铂电极上循环伏安法氧化二甘醇研究

用循环伏安法研究了含二甘醇的１．０ｍｏｌ·Ｌ＾－１Ｈ２ＳＯ４溶液在铂电极上的电氧化行为,证明它是一个不可逆的复杂的氧化还原过程,并考察了温度和浓度对该过程的影响。     

Pd/AC催化1,4-二氯苯加氢脱氯研究

以活性炭(AC)为载体,采用浸渍法制备Pd/AC催化剂,并利用XRD,BET,SEM,TEM等表征手段对AC和Pd/AC进行表征,结果表明,活性组分Pd在活性炭上分散均匀。研究了Pd/AC为催化剂,常压下对1,4-二氯苯(1,4-DCB)进行催化加氢脱氯。在以甲醇为溶剂,2 m L,12.5 g/L 1,4-二氯苯-甲醇溶液为反应原料,Pd/AC催化剂用量为100 mg,反应温度35℃,反应时间为4 h和常压氢气条件下,1,4-DCB的去除率达到100%,苯收率为100%。Pd/AC催化剂套用5次后活性下降,主要原因为有机物沉积和活性组分Pd团聚。     

Electrochemical oxidation of aniline at boron-doped diamond electrodes

The electrochemical oxidation of aniline at boron-doped diamond (BDD) electrodes was investigated by cyclic voltammetry, steady-state polarization measurements and bulk electrolysis under potentiostatic control. It was found that acidic media is suitable for efficient electrochemical oxidation of aniline, because at low pH, the potential required for avoiding electrode fouling is lower than in neutral and alkaline media. The results of the longtime polarization measurements suggested that more anodic potentials ensure slightly higher efficiency for the conversion of aniline to CO₂, while the direct oxidation process does not play a prominent part in the overall electrochemical incineration of aniline. The current efficiencies (44%) and the efficiency of aniline conversion to CO₂ (80%) favourably compare with those reported for other electrochemical methods for aniline destruction. The results demonstrate the possibility of using BDD as an electrode material for electrochemical wastewater treatment, mainly when very high anodic potentials are required.     

催化氧化法分解邻二氯苯

通过实验室研究邻二氯苯在TiO₂-V₂O₅-WO₃等催化剂上氧化分解的特性，筛选出一种合适的催化剂，用于分解脱除垃圾焚烧废气中的二恶英。实验表明，在温度为300 ℃和气体空速为7000 h^－1的反应条件下，邻二氯苯在TiO₂-V₂O₅-WO₃催化剂上的分解率大于90%。     

Electrochemical oxidation of several chlorophenols on diamond electrodes Part I. Reaction mechanism

The electrochemical oxidation of 4-chlorophenol, 2,4-dichlorophenol and 2,4,6-trichlorophenol aqueous wastes using boron-doped diamond electrodes was studied. This treatment led to complete mineralization of the wastes regardless of the operating conditions. A simple mechanistic model is consistent with the voltammetric and electrolysis results. According to this model, the electrochemical treatment of chlorophenol aqueous wastes involves the anodic and cathodic release of chlorine followed by the formation of non-chlorinated aromatic intermediates. Subsequent cleavage of the aromatic ring gives rise to non-chlorinated carboxylic acids. Chlorine atoms arising from the hydrodehalogenation of the chlorophenols are converted into more oxidized molecules at the anode. These molecules react with unsaturated C₄ carboxylic acid to finally yield trichloroacetic acid through a haloform reaction. The non-chlorinated organic acids are ultimately oxidized to carbon dioxide and the trichloroacetic acid into carbon dioxide and volatile organo-chlorinated molecules. Both direct and mediated electrochemical oxidation processes are involved in the electrochemical treatment of chlorophenols.     

Electrochemical oxidation of 2-methylnaphthalene-1,4-diacetate

Cyclic-voltammetric measurements show that 2-methylnaphthalene-1,4-diacetate is electrochemically oxidized on glassy-carbon electrode in glacial acetic acid at +1.45V vs SCE. The process is irreversible and diffusion controlled. Preparative controlled-potential electrolysis indicates that 2-methyl-1,4-naphthoquinone is a sole product. The material and current yields of the process are 94 and 99%, respectively.     

Electrochemical oxidation of phenolic compounds using a flow-through electrolyser with porous solid electrodes

Organic compounds such as phenol and cresols may be found in industrial wastewater along with other organics and are difficult to be economically removed down to concentrations below environmentally permissible limits. By circulating a wastewater through an electrolytic reactor with a stack of porous solid anodes and cathodes, it has been demonstrated that it is feasible to electrochemically oxidize phenolic compounds in the presence of other organic molecules. A porous solid DSA^®-type titanium anode coated with several mixed oxide layers was used as the active material. At low applied current densities, phenol and cresol concentrations were reduced from 5000 ppb to below 20 ppb. The influence of the flow rate and electrodes number was also studied and it was demonstrated that the current density was the main factor to be considered. This work confirms the hypotheses of other authors on the reaction mechanisms involved during the electrochemical oxidation of cresol and phenol.     

顶空固相微萃取-气相色谱法测定水中1,4-二氯苯

建立顶空固相微萃取(HS-SPME)气相色谱测定水中1,4-二氯苯(1,4-DCB).选择SPME前处理技术,毛细色谱柱分离,ECD检测器检测.最低检出质量浓度为1.88 μg/L;工作曲线相关系数为0.992 2;低、中、高三种浓度加标回收率分别为108％、93.1％、117％,相对标准偏差(n=6)分别为7.09％、6.21％、6.98％.该方法具有较好的灵敏度、精密度和回收率.     

Impedance study of methanol oxidation on platinum electrodes

Methanol oxidation on Pt electrodes is studied by ac voltammetry. Data from voltammograms at frequencies from 0.5 Hz to 20 kHz are assembled into electrochemical impedance spectra and analysed using equivalent circuits. Inductive behavior and negative relaxation times are attributed to nucleation and growth behavior. The rate-determining step is proposed to be the reaction of adsorbed CO and OH at the edge of islands of OH, with competition between OH and CO adsorption for the released reaction sites.     

A DEMS study of the electrocatalytic hydrogenation and oxidation of p-dihydroxybenzene at polycrystalline and monocrystalline platinum electrodes

The electrochemical hydrogenation and oxidation of p-dihydroxybenzene (hydroquinone) chemisorbed at polycrystalline Pt, well-ordered Pt(111) and disordered Pt(111) electrodes were studied by differential electrochemical mass spectrometry (DEMS). For comparative purposes, benzene was investigated at polycrystalline Pt. Anodic oxidation yielded only CO₂ as the volatile (DEMS-detectable) product. However, at least three oxidation cycles were necessary for exhaustive oxidation; this indicates that: (i) non-volatile products were generated in the first cycle, (ii) these products either stayed adsorbed or, in part, were re-adsorbed during a cathodic scan into the double-layer potential region, and (iii) these species were further oxidized on subsequent anodic scans. Electrocatalytic hydrogenation of hydroquinone at polycrystalline Pt followed two parallel (not sequential) paths to generate benzene and cyclohexane: the “branching ratio” was heavily in favor of the latter product. The adsorbate can be displaced by CO at potentials in the double layer region. Since no volatile species was observed during this process, the adsorbate is not already reduced; e.g., to benzene. On well-ordered Pt(111), no cyclohexane was produced and only a minuscule fraction of benzene was observed; however, quantitative desorption of (unidentified) non-volatile organic material took place at the negative potential. The disordered Pt(111) surface behaved more like the polycrystalline rather than the monocrystalline surface. The H₂Q-hydrogenation reaction proceeds more readily on Pt with surface steps and kinks.     

Nonlinear phenomena during electrochemical oxidation of hydrogen on platinum electrodes

H₂ oxidation on Pt electrodes, a comparatively simple electrocatalytic reaction, has been known for a long time to exhibit a variety of complex temporal oscillations, depending on the composition of the supporting electrolyte. We report, on the one hand, recent observations of spatial instabilities in the bistable and oscillatory region in this system. The studies indicate that the spatio-temporal dynamic is by far richer than has been assumed so far. On the other hand, aperiodic responses of the system in cyclic voltammetric experiments are described. This behavior is similar to the one observed in potentiodynamic measurements during the electro-oxidation of small organic molecules. A possible common origin of all these complex, current–voltage responses is discussed.