纳米尺度氧化石墨烯层作为高效碳催化剂用于苄醇与芳香醛的绿色氧化

合成了纳米尺度氧化石墨烯(NGO)层,用作碳催化剂高效催化苄醇与芳香醛的氧化反应.对于醇氧化反应,当80℃时H2O2存在下,NGOs(20 wt％)可高效催化醇选择性生成醛,其反应速率和产率取决于醇上取代基的性质.对于4-硝基苄醇,反应24 h后,只有10％可转换为相应羧酸.相反,4-甲氧基苄醇和二苯基甲醇分别反应仅9和3h则可完全转化为对应的羧酸和酮.NGO碳催化剂上芳香醛氧化速率高于醇氧化速率.对于所有的醛,采用7 wt％ NGO作催化剂,在70℃反应2-3 h后,就可完全转化为相应羧酸.我们讨论了NGO催化剂结构对苄醇和芳香醛氧化反应影响的可能机理.     

纳米尺度氧化石墨烯层作为高效碳催化剂用于苄醇与芳香醛的绿色氧化（英文）

合成了纳米尺度氧化石墨烯(NGO)层,用作碳催化剂高效催化苄醇与芳香醛的氧化反应.对于醇氧化反应,当80℃时H_2O_2存在下,NGOs(20 wt%)可高效催化醇选择性生成醛,其反应速率和产率取决于醇上取代基的性质.对于4-硝基苄醇,反应24 h后,只有10%可转换为相应羧酸.相反,4-甲氧基苄醇和二苯基甲醇分别反应仅9和3h则可完全转化为对应的羧酸和酮.NGO碳催化剂上芳香醛氧化速率高于醇氧化速率.对于所有的醛,采用7 wt%NGO作催化剂,在70℃反应2-3h后,就可完全转化为相应羧酸.我们讨论了NGO催化剂结构对苄醇和芳香醛氧化反应影响的可能机理.     

羊毛-Pd(0)催化剂的制备、表征及其在水相中对醇的催化氧化反应

以天然生物高分子羊毛为载体,成功制备了负载型Pd(0)催化剂.采用电场发射扫描电镜和光电子能谱等方法对催化剂进行了表征.结果表明,Pd(0)颗粒均匀地分散在羊毛表面.将羊毛-Pd(0)催化剂用于醇氧化反应,考察了催化剂用量、碱类型和用量、反应温度及时间等因素对反应性能的影响.实验发现,在水相中,35mg羊毛-Pd(0)催化剂在0.2mmol的K2CO3存在下,可以高选择性地将0.2mmol的醇转化为相应的醛或酮,且该催化剂具有很好的重复使用性能.     

Sn改性的Ru/H-CMK-3催化剂的制备及其肉桂醛选择性加氢性能的研究

用浸渍-原位还原法制备了Ru-Sn/H-CMK-3催化剂. 以肉桂醛选择性加氢制备肉桂醇为探针反应. 详细研究了催化剂的制备及反应条件对肉桂醛选择性加氢性能的影响. 采用X 射线粉末衍射(XRD)、比表面积(BET)、X光电子能谱(XPS)、透射电镜(TEM)等手段对催化剂结构和性质进行了表征. 结果表明, 介孔CMK-3碳材料能够更好地分散活性物种. 添加适量的Sn(IV)有利于Ru处于电子富集状态. 催化剂的主要活性物种是纳米Ru粒子, Ru和Sn之间的相互作用更加有利于C＝O的活化. 同时, 反应温度和反应压力等条件的变化对肉桂醛选择性加氢制备肉桂醇反应也具有较大的影响.     

炔醇选择加氢催化剂研究进展

炔醇选择加氢制备相应的烯醇在医药、农药、食品添加剂、香精、香料和聚合物单体等众多高端精细化学品合成中是一个非常重要的化工过程.通过一系列复杂的平行和连续的反应,炔醇可加氢生产若干个关键中间体.提高对烯醇的选择性和保持催化剂的效率是工业生产的关键,也是一个巨大的挑战.迄今为止,各种有效的贵金属和非贵金属催化剂得到了广泛的发展,尤其是钯基和镍基多相催化剂取得了显著进展.从经典的Lindlar催化剂和Raney-Ni催化剂到生物基金属催化新材料,本文系统综述了近几十年炔醇选择加氢催化剂的设计,从催化剂本身的金属活性中心、助剂(第二金属、有机配体和稳定剂)的作用、载体的性质(孔结构、酸碱性、金属与载体强相互作用)以及反应条件等因素对催化活性、目标产物的选择性和稳定性的影响进行了系统的综述.借助先进的表征技术、理论计算和实验研究,本文还阐述了炔醇选择加氢反应的机理.研究发现:(1)在所有贵金属催化剂中,Pd基催化剂对炔醇半加氢制烯醇的效率最高,且选择性最好.稳定剂和抑制剂的加入可以提高中间体的选择性,但在一定程度上降低了催化活性.此外,Zn,In和Cu等第二金属的掺杂可以调节金属Pd的几何效应和电子结构,从而调节底物和中间产物的吸附,并抑制过度加氢.与传统的Lindlar型催化剂相比,这种Pd基合金或金属间化合物可广泛应用于炔醇的选择性加氢反应,显著提高烯醇的选择性,且不需要引入有毒添加剂.(2)Ni基材料作为可替代贵金属催化剂,可分别实现炔醇的高选择性加氢制备烯醇或烷醇.然而,与贵金属催化剂相比,其反应条件相对苛刻.炔醇加氢产物分布很大程度上取决于助剂的引入和载体的酸性.此外,碳物种易沉积在Ni表面造成活性位点被覆盖,且在水热环境下Ni颗粒因团聚而失活,因此,用于炔醇选择加氢反应的镍基催化剂稳定性仍有待提高.尽管炔醇选择加氢反应在学术界和工业界都有广泛研究,但对于这些催化体系,特别是催化剂的结构性能关系和反应机理,仍有待进一步明确.(1)原位表征技术和理论计算的发展,将有助于人们理解炔醇选择性加氢的催化过程,并指导研究者根据炔醇加氢的特点设计出具有良好选择性的高效催化剂.(2)烯醇类产品一般应用于医药中间体和高分子单体,对产品纯度要求较高.因此,在不引入有毒添加剂的情况下,设计高效、高选择性催化剂至关重要.(3)水相或醇相中炔醇选择加氢反应对催化剂的水热稳定性有很高的要求.通过锚定和包覆来增强金属与载体的相互作用,抑制金属纳米粒子的聚集和流失是一种有效的手段.此外,在炔醇选择加氢反应中引入耐水载体可以有效提高催化剂的稳定性.(4)短碳链炔醇催化选择加氢反应一直是研究的热点.然而,关于长碳链炔醇的选择加氢反应过程,国内外报道相对较少.基于长碳链炔醇底物分子的空间位阻效应,有必要设计具有特殊孔道结构的选择加氢催化剂.(5)目前,绝大多数炔醇选择加氢过程还处于间歇性操作.随着市场对烯醇的需求不断增加,为了获得高品质的产品,连续化操作将是一个必然趋势.     

银-磷催化剂的催化性能和表面特征研究

电解银是醇氧化制醛的有效催化剂,已广泛用于甲醛、乙醛和乙二醛等工业生产.在反应过程中,醇被深度氧化生成二氧化碳的副反应在很大程度上阻碍了醛的选择性和产率的进一步提高.实验证明,在纯净的电解银中添加微量磷化合物作为助催化剂,能有效抑制副产物的生成.为了探索这类反应中助催化剂的作用,我们用X射线光电子能谱(XPS)、等离子体火焰发射光谱(ICP-AES)和程序升温反应(TPR)等手段,与活性测试数据结合,对Ag-P催化剂进行了研究.     

一氧化碳加氢合成低碳燃料醇催化剂的研究

以甲醇为主(～75%),异丁醇为辅(～15%)的低碳混合醇称为低碳燃料醇,它与汽油有良好的掺合能,可以掺入汽油作为代用燃料。本工作目的是在较缓和条件下研制合成低碳燃料醇催化剂,进行催化剂评价试验,考察其反应特性,并进行1000小时稳定性试验。1.实验方法催化剂评价试验在固定床反应装置上进行。反应管为φ15×480mm。催化剂20—30     

光照下钴镍盐催化肉桂醛的转移加氢反应

以甲醇为氢源,研究了光照下金属镍盐、钴盐催化肉桂醛的转移加氢反应.结果表明,以Co(OAc)2和Ni(OAc)2为催化剂,肉桂醛可以发生催化转移加氢反应,得到肉桂醇;就催化剂的转移加氢活性和产物肉桂醇的选择性而言,Co(OAc)2的催化效果更好.与此同时,在反应体系中添加NaOAc和Na2C2O4等碱性添加剂可提高肉桂...     

TOF(s-1)

炔醇选择加氢制备相应的烯醇在医药、农药、食品添加剂、香精、香料和聚合物单体等众多高端精细化学品合成中是一个非常重要的化工过程.通过一系列复杂的平行和连续的反应,炔醇可加氢生产若干个关键中间体.提高对烯醇的选择性和保持催化剂的效率是工业生产的关键,也是一个巨大的挑战.迄今为止,各种有效的贵金属和非贵金属催化剂得到了广泛的发展,尤其是钯基和镍基多相催化剂取得了显著进展.从经典的Lindlar催化剂和Raney-Ni催化剂到生物基金属催化新材料,本文系统综述了近几十年炔醇选择加氢催化剂的设计,从催化剂本身的金属活性中心、助剂(第二金属、有机配体和稳定剂)的作用、载体的性质(孔结构、酸碱性、金属与载体强相互作用)以及反应条件等因素对催化活性、目标产物的选择性和稳定性的影响进行了系统的综述.借助先进的表征技术、理论计算和实验研究,本文还阐述了炔醇选择加氢反应的机理.研究发现:(1)在所有贵金属催化剂中, Pd基催化剂对炔醇半加氢制烯醇的效率最高,且选择性最好.稳定剂和抑制剂的加入可以提高中间体的选择性,但在一定程度上降低了催化活性.此外, Zn, In和Cu等第二金属的掺杂可以调节金属Pd的几何效应和电子结构,从而调节底物和中间产物的吸附,并抑制过度加氢.与传统的Lindlar型催化剂相比,这种Pd基合金或金属间化合物可广泛应用于炔醇的选择性加氢反应,显著提高烯醇的选择性,且不需要引入有毒添加剂.(2)Ni基材料作为可替代贵金属催化剂,可分别实现炔醇的高选择性加氢制备烯醇或烷醇.然而,与贵金属催化剂相比,其反应条件相对苛刻.炔醇加氢产物分布很大程度上取决于助剂的引入和载体的酸性.此外,碳物种易沉积在Ni表面造成活性位点被覆盖,且在水热环境下Ni颗粒因团聚而失活,因此,用于炔醇选择加氢反应的镍基催化剂稳定性仍有待提高.尽管炔醇选择加氢反应在学术界和工业界都有广泛研究,但对于这些催化体系,特别是催化剂的结构性能关系和反应机理,仍有待进一步明确.(1)原位表征技术和理论计算的发展,将有助于人们理解炔醇选择性加氢的催化过程,并指导研究者根据炔醇加氢的特点设计出具有良好选择性的高效催化剂.(2)烯醇类产品一般应用于医药中间体和高分子单体,对产品纯度要求较高.因此,在不引入有毒添加剂的情况下,设计高效、高选择性催化剂至关重要.(3)水相或醇相中炔醇选择加氢反应对催化剂的水热稳定性有很高的要求.通过锚定和包覆来增强金属与载体的相互作用,抑制金属纳米粒子的聚集和流失是一种有效的手段.此外,在炔醇选择加氢反应中引入耐水载体可以有效提高催化剂的稳定性.(4)短碳链炔醇催化选择加氢反应一直是研究的热点.然而,关于长碳链炔醇的选择加氢反应过程,国内外报道相对较少.基于长碳链炔醇底物分子的空间位阻效应,有必要设计具有特殊孔道结构的选择加氢催化剂.(5)目前,绝大多数炔醇选择加氢过程还处于间歇性操作.随着市场对烯醇的需求不断增加,为了获得高品质的产品,连续化操作将是一个必然趋势.     

固体超强酸ZrO_2/S2O_8~(2-)催化合成肉桂酸甲酯

研究了在固体超强酸ZrO2/S2O2-8催化下,肉桂酸与甲醇作用合成肉桂酸甲酯的工艺.考查了催化剂的用量、酸醇摩尔比、反应时间及催化剂的性能对反应的影响.最佳反应条件为∶n(肉桂酸)∶n(甲醇)=1∶10,m(肉桂酸)∶m(催化剂)=3∶1,反应温度90～95℃,反应时间5h,酯化率为95.7%.     

Vanadium-catalyzed green oxidation of benzylic alcohols in water under air atmosphere

The oxidation of alcohols using catalytic amounts of metal complexes is highly attractive from the viewpoint of green chemistry principles. However, examples of metal complex-catalyzed oxidations of alcohols with O₂ using water as the solvent are still rare, and precious metals, high-pressure O₂ or air, and a stoichiometric amount of base are often required. In this study, it was found that an oxovanadium-4,4′-t-Bubpy (4,4′-di-tert-butyl-2,2′-bipyridyl) complex exhibited high catalytic activity in the oxidation of benzhydrols under an atmosphere of O₂ in water as the sole solvent. Interestingly, this catalytic oxidation method could be applied to the gram-scale aerobic oxidation of alcohols in water under the atmosphere.     

Cu(II) 2-quinoxalinol salen catalyzed oxidation of propargylic,benzylic, and allylic alcohols using tert-butyl hydroperoxide in aqueous solutions

The synthesis of carbonyl compounds by oxidation of alcohols is a key reaction in organic synthesis. Such oxidations are typically conducted using catalysts featuring toxic metals and hazardous organic solvents. Considering green and sustainable chemistry, a copper(II) complex of sulfonated 2-quinoxalinol salen (sulfosalqu) has been characterized as an efficient catalyst for the selective oxidation of propargylic, benzylic, and allylic alcohols to the corresponding carbonyl compounds in water when in combination with the oxidant tert-butyl hydroperoxide. The reactions proceed under mild conditions (70 °C in water) to produce yields up to 99% with only 1 mol % of catalyst loading. This reaction constitutes of a rare example of propargylic alcohol oxidation in water, and it makes this process greener by eliminating the use of hazardous organic solvents. Excellent selectivity was achieved with this catalytic protocol for the oxidation of propargylic, benzylic, and allylic alcohols over aliphatic alcohols. The alcohol oxidation is thought to go through a radical pathway.     

In Process Citation

Oxidation with vanadium pentoxide in aqueous sulphuric acid has certain limitations, mainly because of the instability of vanadosulphate complexes in aqueous media. Hence the possibility of use of less strongly dissociative solvents than water has been examined with a view to enhancing the stability and oxidizing power of these complexes. Some simple organic oxygen compounds (alcohols, aldehydes, ketones and acids) have been examined as reductants, together with some others (acetals and esters) which are difficult to study in aqueous media because of the hydrophobic character. The results show that alcohols are more resistant to attack in non-aqueous medium than in water, and that the longer-chain alcohols are more easily oxidized. The aldehydes are more difficult to oxidize than ketones, as is also the case in water. The acids, also as in water, react only very feebly. The use of non-aqueous media extends the range of oxidation with vanadate to some substances insoluble in water (such as epoxides) which display sufficient reactivity.     

Mild and selective oxidation of alcohols to aldehydes and ketones using NaIO4/TEMPO/NaBr system under acidic conditions

A TEMPO-catalyzed selective oxidation of alcohols to the corresponding aldehydes and ketones using NaIO₄ as the terminal oxidant is reported. The NaIO₄/TEMPO/NaBr system provides a mild and efficient method for the oxidation of alcohols that are sensitive to basic conditions. Furthermore, the recoverable ionic liquid immobilized TEMPO-catalyzed oxidation of benzyl alcohol in ionic liquid-H₂O medium is also developed.     

Studies on the oxidation reaction of tyrosine (Tyr) with H2O2 catalyzed by horseradish peroxidase (HRP) in alcohol-water medium by spectrofluorimetry and differential spectrophotometry

An oxidation reaction of tyrosine (Tyr) with H(2)O(2) catalyzed by horseradish peroxidase (HRP) was studied by spectrofluorimetry and differential spectrophotometry in the alcohol(methanol, ethanol, 1-propanol and isopropanol)-water mutual solubility system. Compared with the enzymatic-catalyzed reaction in the water medium, the fluorescence intensities of the product weakened, even extinguished. Because the addition of alcohols made the conformation of HRP change, the catalytic reaction shifted to the side of polymerization and the polymer (A(n)H(2), n>or=3) exhibited no fluorescence. The four alcohols cannot deactivate HRP. Moreover isopropanol activated HRP remarkably.     

Oxidation of alcohols by TBHP in the presence of sub-stoichiometric amounts of MnO2

Commercially available activated MnO₂ has been investigated as a catalyst for the oxidation of alcohols (phenylethanol, 4-methyl- and 4-methoxybenzyl alcohol, trans-cinnamyl alcohol, cyclohexanol, menthol, perillyl alcohol and myrtenol) by TBHP/decane or TBHP/water in MeCN. The activity is highest for benzylic and allylic alcohols. Secondary alcohols yield ketones with good selectivities, while the aldehydes generated from primary alcohols are further oxidized. The process competes with the TBHP catalyzed decomposition. It thus requires the use of excess TBHP and high catalyst loadings to achieve high conversions. However, the low cost of the reagents makes this new protocol convenient for the oxidation of reactive secondary alcohols. The study also suggests that MnO₂ should be proscribed as a reagent to quench excess TBHP in oxidative processes when the synthetic target contains easily oxidizable alcohol functions and when carrying our detailed kinetic monitoring of oxidation processes.     

Efficient synthesis of carbonyl compounds: oxidation of azides and alcohols catalyzed by vanadium pentoxide in water using tert-butylhydroperoxide

Catalytic amount of vanadium reagent with tert-butylhydroperoxide as the oxidant was found to be an excellent oxidizing agent in aqueous medium. Vanadium pentoxide with aq tert-butylhydroperoxide readily oxidizes primary benzylic azides to the corresponding acids and secondary benzylic azides to the corresponding ketones in excellent yields. Further, vanadium pentoxide and aq tert-butylhydroperoxide combination turned out to be an effective catalyst for the oxidation of alcohols. Using vanadium pentoxide and aq tert-butylhydroperoxide primary alcohols were oxidized to the corresponding acids, whereas secondary alcohols underwent a smooth transformation to furnish corresponding ketones in excellent yields. All the oxidations are performed in water.     

典型醇类物质超临界水氧化反应途径研究

采用自主设计的连续流动气封壁超临界水氧化反应装置,研究了典型醇类物质甲醇、乙醇和异丙醇在超临界水中氧化的反应途径,并归纳了醇类物质超临界水氧化反应的规律及特点。研究结果表明,甲醇超临界水氧化反应的主要中间产物为甲醛,同样条件下转化率较乙醇和异丙醇低;乙醇和异丙醇超临界水氧化反应的主要中间产物为丙酮、乙酸、乙醛和甲醇等。三种醇超临界水氧化过程中均涉及到大量活性自由基的相互作用,表现为脱氢、裂解和聚合等反应形式;产物包括碳链增长、不变、降低三种类型。总体来看,醇类物质超临界水氧化反应的趋势是向碳链降低的方向进行,即通过一系列中间产物最后生成CO₂和水。     

I2O5: mild and efficient reagents for the oxidation of alcohols in water

The mild and efficient nature of HIO₃ and I₂O₅ as environmentally benign, commercially available, atom efficient, and safe reagents for the oxidation of alcohols has been demonstrated. Additionally, these oxidants are highly chemoselective, and effect smooth room temperature oxidation of various electron-rich alcohols with catalytic amounts of KBr in water.     

Catalytic Oxidation of Alcohols to Corresponding Aldehydes or Ketones with TEMPO-Mediated Iodosobenzene in Water in the Presence of a Surfactant

An efficient, facile, and rapid oxidation of alcohols to the corresponding aldehydes or ketones with a stoichiometric amount of iodosobenzene (PhIO) in the presence of catalytic amounts of 2,2,6,6-tetramethyl-1-piperidinyloxyl free radical (TEMPO), KBr, and a surfactant, such as SDS (sodium dodecylsulfate), was reported. The oxidation proceeded in water at room temperature to afford aldehydes or ketones in excellent yields and high selectivity without overoxidation to carboxylic acids. Selective oxidation of primary alcohols in the presence of secondary alcohols was also achieved with the catalytic system of PhIO/TEMPO/KBr/SDS. A possible mechanism for the oxidation was supposed.