精细有机中间体的间接电合成

阐述了间接电氧化的进展及应用 ,并重点介绍了以BrO- /Br- 和Cr2 O2 - 7/Cr3 + 作电解媒质分别氧化葡萄糖和对二甲苯的研究。     

电合成对氟苯甲醛的研究

以PbO2 /Ti为阳极 ,Pb为阴极 ,于无隔膜电解槽中将Mn(Ⅱ )电氧化成Mn(Ⅲ ) ,产率为87 0 % ,电流效率为 71 5 % ,明显优于用Pb(+) -Pb(- )电极对的电解结果。电解液可循环使用。以Mn(Ⅲ )为氧化媒质 ,采用槽外式间接电合成法将对氟甲苯氧化成对氟苯甲醛 ,产率为76 5 %。     

间接电氧化合成对溴苯甲醛

提出采用间接电合成法以Ce4+/Ce3+为媒质,在高剪切混合乳化机搅拌下使Ce4+氧化对溴甲苯合成对溴苯甲醛工艺,使用后的媒质再生循环使用,无三废排放。在隔膜电解槽中Ce3+电氧化的最佳条件是c(Ce3+)=0 8mol/L;c(H2SO4)=0 3mol/L;电流密度200A/m2;电量1 0F/mol,Ce4+的电解收率90 9%。槽外合成对溴苯甲醛的最佳条件是n(Ce4+)∶n(p Br—C6H4—CH3)=4∶1;c(H2SO4)=0 3mol/L;反应温度85℃,对溴苯甲醛反应收率78 5%,Ag+催化下对溴苯甲醛反应收率90 3%。     

电化学法合成茴香醛的中试研究

采用间接电合成法以Ce4+/Ce3+为媒质,在高剪切混合乳化机搅拌下对Ce4+氧化对甲基苯甲醚合成茴香醛进行了中试研究。结果表明,Ce4+电解收率83 4%,茴香醛单程反应收率88 8%;使用后的媒质再生循环使用,无三废排放。     

以四碳不饱和酸为原料成对电合成1,2-二醇类化合物

建立了一种成对电合成体系 ,以VO(acac) 2 VO(acac) 2 OOH为媒质 ,间接氧化烯烃得到相应的环氧化物 ;阳极以Br2 Br- 为媒质 ,间接氧化烯烃成邻溴代醇。马来酸环氧化反应总电流效率高达 145 %     

间接电合成槽型结构的研究

研究了Ce4+/Ce3+做氧化媒质间接电合成芳香醛的槽型结构。结果表明,隔膜电解槽与无隔膜电解槽相比,电解收率高6 8%,电流效率高6 6%;在无隔膜电解槽内,槽压低0 85V,通过调节阴阳极面积比,减少在阳极区Ce3+电解氧化生成的Ce4+在阴极区被还原为Ce3+,电耗比隔膜电解槽减少70 6kW·h/t,生产对甲氧基苯甲醛电耗减少590kW·h/t。     

间接电氧化法合成氟代苯甲醛

在无隔膜电解槽中采用石墨电极,以稀HNO3为介质,Ce4+/Ce3+为氧化还原媒质,间接电氧化氟代甲苯法合成了邻(间、对)氟代苯甲醛。通过实验,得到了电解最佳条件,电流效率达到62%,氟代苯甲醛收率80%。     

茴香脑间接电氧化合成茴香醛

研究了在硫酸溶液中以Mn(Ⅱ)/Mn(Ⅲ)作为媒质,铅为阴极和阳极,在无隔膜电解槽中间接电化学氧化茴香脑合成茴香醛,讨论了电解反应条件对电解产率的影响。结果表明,以5.5 mol/L H2SO4+0.15 mol/LMn(Ⅱ)为电解液,控制电流密度为50 mA/cm2,电解温度为40℃,阴、阳极面积比为1∶6,电解2 h时,得到的Mn(Ⅲ)电解产率高达95.6%;以乙醚为溶剂,在50℃恒温搅拌且回流冷凝的条件下,用Mn(Ⅲ)氧化稍超过理论量的茴香脑,合成的茴香醛产率高达80.7%。     

几种氧化还原电对在间接电氧化合成中的应用

间接电氧化有机物是有机合成的一个重要方向。本文介绍了间接电化学氧化过程中常用的凡种氧化煤质的电生过程以及它们在间接电氧化合成中的应用，对比了Co3+、Ce3+及Mn3+的氧化活性，指出了适合于用它们来氧化的甲苯衍生物的特征。     

以Ce3+/Ce4+为媒质间接电合成1,4-萘醌

探讨了以Ce³⁺/Ce⁴⁺为媒质的1,4-萘醌间接电化学合成反应。考察了液相氧化、Ce³⁺电解氧化过程的影响因素,并进行了萘醌的间接电合成实验。结果发现,硫酸浓度、溶液温度对铈离子的氧化能力和电化学反应活性具有重要的影响;当温度为70℃、硫酸浓度为1.0 mol·L^-1时,液相氧化反应的收率最高(85.8%)。Ce³⁺电解氧化的最优条件为:电流密度50 mA·cm^-2、硫酸浓度1.0 mol·L^-1、温度为50℃,其电流效率可达90.6%;间接电合成实验过程中萘醌的平均收率达85.7%,Ce³⁺电解氧化的平均电流效率达87.8%,并且电解过程具有良好的稳定性,表明该技术具有良好的产业化应用前景。     

均匀设计法研究甲苯间接电氧化合成苯甲醛

用均匀设计法研究了以三价锰为媒质 ,间接电氧化甲苯合成苯甲醛。研究了反应物浓度、槽电压、反应温度和反应时间等因素对电解过程三价锰产率和电流效率的影响 ,实验数据通过多元回归分析 ,找出其最佳工艺条件。实现了媒质多次循环的效果。     

Paired electrosynthesis of epoxides and dibromides from olefinic compounds

A VO(acac)₂/[VO(acac)₂OOH]⁻ redox mediator was used for the cathodic oxidation of olefinic compounds to the corresponding epoxides. The oxidation process consists of a multi-step such as (a) cathodic reduction of dioxygen to hydrogen peroxide, (b) chemical oxidation of VO(acac)₂ to [VO(acac)₂OOH]⁻ with the resulting hydrogen peroxide, (c) the chemical epoxidation of olefins with [VO(acac)₂OOH]⁻, and (d) the regeneration of VO(acac)₂. On the other hand, the olefinic compounds are indirectly oxidized (brominated) with a Br⁻/Br⁺ mediator to give the corresponding 1,2-dibromides. Pairing this indirect anodic oxidation (bromination) with the above indirect cathodic epoxidation, an efficient paired electrosynthetic system could be developed for preparation of epoxides and 1,2-dibromides.     

丁二烯和醋酸电化学合成山梨酸

正交实验表明 ,在醋酸 醋酐体系中 ,Mn2 + 电解氧化生成Mn3 + 的最佳工艺为 :电解时间 1h ,电解温度 90℃ ,电流密度 5mA/cm2 ,电解液 (2 0 0mL)组成 :5 70gMn(OAc) 2 ·4H2 O +2 0 .0gKOAc+醋酸与醋酸酐的混合物 ,V(HOAc)∶V(Ac2 O) =3∶1,电流效率为 75 %。稳态极化曲线和RDE实验表明 ,在石墨电极上 ,Mn2 + 阳极氧化的电极反应控制步骤为扩散 电荷传递混合控制。通过Mn3 + 氧化有丁二烯存在的醋酸 醋酐体系 ,合成山梨酸的前体乙酰氧基己烯酸 (AA) ,丁二烯的浓度为 0 2 5～ 1.0 0mol/L ,温度控制在 90℃ ,反应 5h ,得到AA。用盐酸可将AA进一步水解生成山梨酸 ,反应温度为 90℃ ,反应 5～ 6h ,产率超过 80 % (对AA而言 )。     

Catalysts based in cerium oxide for wet oxidation of acrylic acid in the prevention of environmental risks

Acrylic acid is a refractory compound for the non-catalytic wet oxidation (WO) process and can seriously damage the environment when released in industrial effluents. Oxidation of acrylic acid by catalytic wet oxidation (CWO) was studied in slurry conditions in a high-pressure batch reactor at 200 °C and 15 bar of oxygen partial pressure. Several solid cerium-based catalysts prepared in our laboratory were used (Ag/Ce, Co/Ce, Mn/Ce, CeO, MnO) and evaluated in terms of activity, selectivity and stability. Mn/Ce shows the higher activity in 2 h with 97.7% reduction of total organic carbon (TOC) followed by: MnO(95.5%)>Ag/Ce(85.0%)>Co/Ce(65.1%)>CeO(61.2%). Attempts were also carried out to analyze the influence of different Mn/Ce molar ratios. High percentages of Mn lead to practically total organic carbon concentration (TOC) abatements while low ratios lead to the formation of non-oxidizable compounds. Acrylic acid was readily degraded by all the catalysts pointing out the high importance of using a catalytic process. pH was an indicator of the reaction pathway and acetic acid was found as the major reaction intermediate compound; however it is completely oxidized after 2 h with exception for Co/Ce, CeO and MnO. Carbon adsorption and leaching of metals were poorly found for Mn/Ce indicating high stability. The catalyst microstructure after the reaction was analyzed and formation of whiskers of β-MnO₂ (or less probably MnOOH) were observed at the catalyst surface. Therefore, Mn/Ce revealed to be a promising catalyst for the treatment of effluents containing acrylic acid; nevertheless, its commercialization depends on further research.     

过氧叔丁醇催化氧化法合成4-氧代-β-紫罗兰酮

开发了一种以过氧叔丁醇为氧化剂,乙酰丙酮钒为催化剂合成4-氧代-β-紫罗兰酮的方法。主要探讨了氧化剂用量、催化剂用量、溶剂、温度对反应的影响。得出4-氧代-β-紫罗兰酮的有利合成条件是β-紫罗兰酮1.92g(10mmol),VO(acac)20.13g(0.5mmol),过氧叔丁醇50mmol,在35℃下于10mL丙酮中反应6h,4-氧代-β-紫罗兰酮的产率达到68%,纯度高于98%。     

过氧叔丁醇氧化合成3-氧代-a-紫罗兰酮

开发了一种以过氧叔丁醇为氧化剂,乙酰丙酮钒为催化剂的合成3-氧代-a-紫罗兰酮的方法。主要探讨了氧化剂用量、催化剂用量、溶剂、温度对反应的影响。得出3-氧代-a-紫罗兰酮的有利合成条件是-a-紫罗兰酮1．92g（10mmol）·VO（acac）2 0·13g（0．5mmol）,过氧叔丁醇50mmol,在35℃下于10mL丙酮中反应6h,3-氧代-a-紫罗兰酮的产率达到58％,纯度高于98％。     

A comparative study of azo dye decolorization by electro‐Fenton in two common electrolytes

BACKGROUND: This study compared the decolorization behaviors of a model azo dye of methyl red in Na₂SO₄ and NaCl media by electro‐Fenton process, in which FeSO₄ was added into the solution, while H₂O₂ was efficiently generated on a graphite–polytetrafluoroethylene cathode. Parameters such as pH, cathodic potential, electrolyte concentration, and initial dye concentration as well as the treatment time were investigated to disclose different decolorization behaviour. RESULTS: Decolorization in NaCl medium had an advantage over that in Na₂SO₄ medium not only in performance but also in its suitability for application, which seemed less sensitive to variations in parameters and thus broadened the optimal performance range. In NaCl medium, indirect oxidation by active chlorine contributed greatly to the decolorization, and the removal of methyl red obeyed pseudo‐first‐order kinetics. CONCLUSION: Electro‐Fenton oxidation in the present system in the presence of NaCl would is a promising procedure for azo dye waste‐water treatment. Copyright © 2009 Society of Chemical Industry