负载型纳米复合杂多酸催化α-蒎烯的环氧化反应研究

以自制的负载型纳米复合杂多酸H3PW12O40/SiO2催化剂和30%(质量分数)H2O2制备的过氧乙酸为氧化剂,研究α-蒎烯环氧化反应。试验结果表明,过氧乙酸与α-蒎烯的摩尔比为3.0,相转移催化剂四丁基溴化铵浓度为0.06 mol/L,负载型纳米复合杂多酸用量为4%(占α-蒎烯质量百分数),在三氯甲烷溶剂中反应2.0 h,反应温度在16~20℃,α-蒎烯转化率达86.53%,2,3-环氧蒎烷选择性为74.84%。     

催化氧化法从重质松节油制高纯度长叶烯及环氧石竹烯

以过氧磷钼钨酸十六烷基吡啶盐(Cat-PMo2W2O24)为催化剂,质量分数30%H2O2为氧化剂,催化重质松节油中β-石竹烯氧化生成环氧石竹烯;产品结构经气质联用谱、红外光谱、1HNMR及13CNMR谱表征确认。考察了反应温度、溶剂种类、催化剂用量、反应物料比、反应时间对催化反应体系相态以及底物转化率与环氧选择性的影响,得出最优反应条件为:重质松节油2.80 g,催化剂用量为重质松节油质量的1.07%,溶剂乙酸乙酯5m L,H2O2与β-石竹烯的物质的量之比1.78,反应温度35℃,反应时间2.5 h。在该条件下,反应体系为环境友好液-液-固相转移催化反应体系,催化剂易分离回收、重复利用;β-石竹烯转化率和环氧石竹烯选择性分别高达98.1%和98.4%,而长叶烯基本不被氧化;反应结束后,反应混合物经冷却、相分离除去水相,过滤回收催化剂,减压分馏得到高纯度长叶烯(GC含量92%)和环氧石竹烯(GC含量95%)。     

四硫富瓦烯类衍生物的合成及表征

以金属钠和二硫化碳为起始原料,合成四硫富瓦烯(TTF)锌的配合物(TTF)Zn(NBu_4)_2。其与卤代烷烃或取代类酰氯反应得到16个对称的四硫富瓦烯硫酮类衍生物,再经醋酸汞氧化分别得到16个四硫富瓦烯氧酮类衍生物,其中13个未见文献报道。操作简单且收率达80%以上,其结构经~1H NMR、~(13)C NMR表征确证。     

反应条件对α—蒎烯异构成苎烯选择性的影响

研究了用化学气相沉积法修饰的１３Ｘ分子筛催化α－蒎烯异构化反应，考察了反应温度，反应时间，催化剂酸性质及催化剂孔径对苎烯选择性的影响。     

HN型催化剂催化α——蒎烯制苎烯的初步研究

本文用ＨＮ型催化剂低温催化α－蒎烯异构化制苎烯，考察了反应温度、反应时间、催化剂种类对反应结果的影响。实验结果表明在７０℃、反应４ｈ以上，苎烯的选择性仍保持在３５％以上。     

SWA/TiO_2微球的制备及催化α-蒎烯异构化性能

采用溶胶-凝胶法和浸渍法,制备了纳米负载型H4SiW12O40（SWA）催化剂,考察了载体种类、SWA浸渍浓度对催化剂性能的影响。结果表明,用TiO2固载、8%SWA浸渍所得催化剂SWA/TiO2的催化性能较佳。利用XRD、TEM和BET比表面测定技术对其结构进行了表征。结果显示,该催化剂颗粒为圆球形,粒径为40～50 nm,具有较好的分散性。载体TiO2的引入明显增大了SWA的比表面积。将纳米SWA/TiO2用于催化α-蒎烯异构化反应,实验结果表明,该催化剂具有较好的催化活性和选择性,异构化反应的主产物是莰烯。在适宜的实验条件下,α-蒎烯的转化率达98%,莰烯的产率达58%。与其它负载型催化剂比较,SWA/TiO2具有用量少、活性高、反应时间短等特点。     

SWA/TiO2微球的制备及催化α-蒎烯异构化性能

采用溶胶-凝胶法和浸渍法,制备了纳米负载型H4SiW12O40(SWA)催化剂,考察了载体种类、SWA浸渍浓度对催化剂性能的影响。结果表明,用TiO2固载、8%SWA浸渍所得催化剂SWA/TiO2的催化性能较佳。利用XRD、TEM和BET比表面测定技术对其结构进行了表征。结果显示,该催化剂颗粒为圆球形,粒径为40～50 nm,具有较好的分散性。载体TiO2的引入明显增大了SWA的比表面积。将纳米SWA/TiO2用于催化α-蒎烯异构化反应,实验结果表明,该催化剂具有较好的催化活性和选择性,异构化反应的主产物是莰烯。在适宜的实验条件下,α-蒎烯的转化率达98%,莰烯的产率达58%。与其它负载型催化剂比较,SWA/TiO2具有用量少、活性高、反应时间短等特点。     

丙烷CO_2氧化脱氢制丙烯研究进展

丙烷氧化脱氢反应不受热力学平衡限制,焓变小于零,为放热反应,可节省能源。但氧化脱氢制丙烯因为有O2存在,导致丙烷和丙烯深度氧化,使丙烯选择性下降。可通过以下途径改进:(1)通过添加助剂或改变活性组分限制丙烯的深度氧化;(2)改变反应气氛,用氧化性较弱的氧化剂(如CO2和N2O等)代替O2。近年来,在低碳烷烃脱氢领域以CO2为氧化剂的研究较多,CO2可以避免深度氧化。综述在丙烷氧化脱氢反应中通过引入CO2,将丙烷直接脱氢反应与逆水煤气反应进行偶合,打破了丙烷直接脱氢反应平衡,消除积炭,提高催化剂稳定性,推动反应向生成丙烯的方向进行,丙烯收率提高;在低温(270℃)区域,副反应可提高丙烷CO2氧化脱氢反应的丙烯平衡收率,丙烷二氧化碳脱氢反应的催化剂体系主要包括铬系催化剂、镓系催化剂、钒系催化剂及其他催化剂。     

高纯度α—柏木烯的制备研究

以粗柏木烯为原料，在催化剂作用下经异构化反应使β－柏木烯转化α-柏木烯后，进一步精馏提纯得到了高纯度α-柏木烯，测试产品的质量和性能，对柏木烯异构化的反应温度，反应时间，催化剂及用量进行了选择试验。     

伞花烃,Ning烯,α—蒎烯的电氧化反应的对比研究

探讨了伞花烃，Ｎｉｎｇ烯，α－蒎烯的电氧化反应，分离和提纯了这些反应的主产物，并通过ＩＲ，＾１ＨＮＭＲ，ＭＳ谱证实了它们的结构。     

Catalytic oxidation of alcohols using molecular oxygen mediated by poly(ethylene glycol)-supported nitroxyl radicals

The selective catalytic oxidation of alcohols over a mixture of copper(I) chloride and a number of linear ‘linker-less’ or ‘branched’ poly(ethylene glycol)-supported nitroxyl radicals of the 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) family as a catalyst system has been investigated in the presence of molecular oxygen in a batch reactor. It is found that the activity profile of the polymer-supported nitroxyl radicals is in good agreement with that of low-molecular weight nitroxyl catalysts, for example, allylic and benzylic alcohols are oxidised faster than aliphatic alcohols. The oxidations can be tuned to be highly selective such that aldehydes are the only oxidation products observed in the oxidation of primary alcohols and the oxidations of secondary alcohols yield the corresponding ketones. A strong structural effect of the polymeric nitroxyl species on catalytic activity that is dependent upon their spatial orientation of the nitroxyl radicals is particularly noted. The new soluble macromolecular catalysts can be recovered readily from the reaction mixture by solvent precipitation and filtration. In addition, the recycled catalysts demonstrate a similar selectivity with only a small decrease in activity compared to the fresh catalyst even after five repetitive cycles.     

Catalytic oxidation of alcohols using molecular oxygen mediated by poly(ethylene glycol)-supported nitroxyl radicals

The selective catalytic oxidation of alcohols over a mixture of copper(I) chloride and a number of linear ‘linker-less’ or ‘branched’ poly(ethylene glycol)-supported nitroxyl radicals of the 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) family as a catalyst system has been investigated in the presence of molecular oxygen in a batch reactor. It is found that the activity profile of the polymer-supported nitroxyl radicals is in good agreement with that of low-molecular weight nitroxyl catalysts, for example, allylic and benzylic alcohols are oxidised faster than aliphatic alcohols. The oxidations can be tuned to be highly selective such that aldehydes are the only oxidation products observed in the oxidation of primary alcohols and the oxidations of secondary alcohols yield the corresponding ketones. A strong structural effect of the polymeric nitroxyl species on catalytic activity that is dependent upon their spatial orientation of the nitroxyl radicals is particularly noted. The new soluble macromolecular catalysts can be recovered readily from the reaction mixture by solvent precipitation and filtration. In addition, the recycled catalysts demonstrate a similar selectivity with only a small decrease in activity compared to the fresh catalyst even after five repetitive cycles.     

Efficient and Selective Aerobic Alcohol Oxidation Catalyzed by Copper(II)/2,2,6,6,‐Tetramethylpiperidine‐1‐oxyl at Room Temperature

A simple and efficient copper(II)/2,2,6,6,‐tetramethylpiperidine‐1‐oxyl (TEMPO)‐catalyzed aerobic oxidation of both primary and secondary benzylic, allylic, and aliphatic alcohols to their corresponding aldehydes and ketones at room temperature using the copper(II) complex [Cu(μ‐Cl)(Cl)(phen)]₂ as the Cu(II) source is reported. The conversion of both electron‐rich and electron‐neutral benzyl alcohols is smooth and faster than those of electron‐deficient ones. The chemoselectivity of a primary benzyl alcohol over the secondary alcohol is also observed. Alcohols regarded as difficult substrates for oxidation due to their coordinating ability with transition metal catalyst such as 4‐(methylthio)benzyl alcohol and 3‐pyridinemethanol are also oxidized easily. In addition, a lignin model alcohol is oxidized to the corresponding aldehyde in excellent yield. Conversions of benzylic and allylic alcohols are faster as compared to those of aliphatic alcohols in accordance with their C_α H bond strengths. A plausible mechanism of the TEMPO‐based catalytic cycle is proposed.     

一步法催化氧化正辛醇生成正辛酸

开发了利用分子氧作为惟一氧化剂、高效一步法氧化正辛醇到辛酸的固体Ru-Co(OH)₂-CeO₂催化剂.使用了XRD和XPS等表征手段分析了老化温度对催化剂结构的影响,认为催化剂中存在CeO₂和Co(OH)₂两种微晶结构,Ru以较高的四价氧化态很好地分散在催化剂中.元素Ru、Co和Ce之间的协同效应对于在温和条件下从正辛醇到正辛酸一步法转化起着高效的促进作用.该反应的机理为首先从正辛醇到辛醛的β消除,随后从辛醛到正辛酸的自由基历程.     

Environmentally friendly alcohol oxidation using heterogeneous catalyst in the presence of air at room temperature

Various types of alcohols oxidation can be achieved using air as a sole oxidant at room temperature without any other additives. From the results of Ru K-edge XAFS and XPS characterizations, MnFe_1.5Ru_0.35Cu_0.15O₄ catalyst with possibly coordinatively unsaturation of the isolated RuO species as active sites is an efficient heterogeneous catalyst and can be reused. Besides, the workup procedure is extremely simple.     

氮氧自由基催化醇选择性氧化反应的研究进展

醇选择性氧化成醛或酮的反应是有机合成中一个重要的研究领域,氮氧自由基(NO·)具有强氧化性,在加快产物醛或酮转化的同时,能有效地防止酸生成,是当前研究较多的醇催化氧化反应活性中心之一。主要介绍了含NO·结构催化剂体系催化醇选择氧化反应的研究进展,对含氮氧自由基结构化合物组成的均相及多相催化剂体系进行了归类总结,分析了催化醇氧化反应的方法及工艺条件方法的优缺点及反应机理,并展望了今后的研究发展方向。     

Oxidation of hydrophobic alcohols using aqueous hydrogen peroxide over amphiphilic silica particles loaded with titanium(IV) oxide as a liquid–liquid phase-boundary catalyst

Phase-boundary catalysis (PBC), a new concept of a heterogeneous catalytic system for oxidation of various hydrophobic alcohols with aqueous hydrogen peroxide (H₂O₂), has been investigated. A part the external surface of silica (SiO₂) particles loaded with titanium(IV) oxides was modified with hydrophobic alkyl groups to obtain amphiphilic particles, having both hydrophobic and hydrophilic surfaces on each particle. The amphiphilic particles were spontaneously assembled at interfaces between dual phase mixtures of aqueous solutions and water-immiscible organic compounds. Upon addition to a dual phase mixture of aqueous H₂O₂ and toluene-containing hydrophobic alcohols, these particles acted as an efficient catalyst for the reaction, to produce corresponding aldehydes and ketones selectively. Notable features of the PBC system are that the oxidation proceeds even without agitation and that only a few percent of titanium species was detected as dissolved species. Productions of aldehydes and ketones were also observed when titanium loaded SiO₂ without modification with alkyl groups was employed for the reaction. However, a large amount of titanium loaded on the material was leached during the reaction. These results indicate that surface-covered alkyl groups not only bring about effective contact with hydrophobic alcohols in the organic phase but also give stability against leaching, leading to heterogeneous catalytic functions.     

Novel efficient catalysts based on Ru or Pd oxide for selective liquid-phase oxidation of alcohols with nitrous oxide

Ru^IV–M and Pd^II–M (MCo^III, Fe^III and Mn^III) binary oxides supported on γ-alumina are demonstrated to be novel, active catalysts for selective liquid-phase oxidation of primary and secondary alcohols to, respectively, aldehydes and ketones with nitrous oxide under 10 bar N₂O pressure and 100 °C. The Ru and Pd catalysts have comparable activities but Ru ones are more selective, the Ru–Co system (Ru/Co=1:1) showing the best performance. Activated primary alcohols (benzyl and cinnamyl alcohol) and secondary alcohols give aldehydes or ketones with 100% selectivity at 95–100% conversion. Non-activated primary alcohols (e.g. 1-dodecanol) give aldehydes with some over-oxidation to acids; the latter is completely inhibited by adding a radical scavenger. The Ru–Co catalyst can be reused without loss of selectivity, although with a gradual decrease in its activity. Compared to the Ru–Co catalysed oxidation of alcohols with O₂ studied earlier, the oxidation with N₂O has the advantage of considerably higher selectivity, albeit occurring under higher pressures.     

Membrane‐Occluded Gold‐Palladium Nanoclusters as Heterogeneous Catalysts for the Selective Oxidation of Alcohols to Carbonyl Compounds

Pre‐formed polyvinylpyrrolidone‐stabilized gold‐palladium clusters, consisting of 80 mol% gold and with a mean size of 1.9 nm, were immobilized quantitatively in a porous polyimide membrane via the process of phase inversion, without loss of metal nanodispersion. The obtained gold‐palladium/polyimide membrane emerged as a highly active heterogeneous metal catalyst for the amide‐phase and solvent‐free oxidation of aliphatic, allylic and benzylic alcohols with full selectivity to the corresponding aldehydes and ketones, and could be recycled with excellently preserved catalytic activity and product selectivity. Occlusion of the optimized bimetallic clusters in the polyimide structure proved beneficial in view of their superior catalytic performance compared to the analogous colloidal gold‐palladium clusters.