NHPI/Co(Salen)催化氧化取代甲苯

以分子氧为氧化剂,N-羟基邻苯二甲酰亚胺(NHPI)为引发剂,Co(Salen)配合物[NHPI/Co(Salen)]为催化剂,偶氮二异丁腈(AIBN)为助引发剂,AcOH为溶剂,催化氧化取代甲苯制备取代苯甲酸。最佳反应条件为:甲苯6mmol,q(NHPI)=10%,q[Co(Salen)]=0.5%,q(AIBN)=1%,O2(0.1MPa),AcOH10mL,于80℃反应20h,甲苯转化率92.7%,苯甲酸选择性88.9%。     

N-羟基邻苯二甲酰亚胺和二氧化锰高效催化对硝基甲苯氧化

采用N-羟基邻苯二甲酰亚胺(NHPI)和二氧化锰(MnO2)作为催化剂催化对硝基甲苯的氧化反应以制备对硝基苯甲酸;对反应条件进行了优化.结果表明,采用10%(与原料的摩尔比)NHPI和10%(与原料的摩尔比)MnO2作为催化剂,在110℃、氧气压力0.4 MPa下反应4 h,对硝基甲苯的转化率为97%,对硝基苯甲酸的分...     

聚合物微球固载的N-羟基邻苯二甲酰亚胺在分子氧氧化甲苯过程中的催化性能

以交联聚苯乙烯(CPS)微球为基质,经过几步大分子反应在微球表面合成与固载了N-羟基邻苯二甲酰亚胺(NHPI),形成固载有NHPI的聚合物微球CPS-NHPI。本文主要将CPS-NHPI与过渡金属盐组成共催化体系,用于分子氧氧化甲苯的反应,考察了该非均相催化剂的催化特性与催化氧化机理。结果表明,几种过渡金属盐中,Co(OAc)2的助催化效果最好;微球CPS-NHPI与Co(OAc)2所构成的共催化体系,在温和条件(80℃和常压氧气)下可有效地将甲苯深度氧化为苯甲酸,显现出高的催化活性(甲苯转化率达到57%)与优良的选择性(苯甲酸的选择性达到84%)。催化氧化反应遵循自由基链式反应机理。主催化剂CPS-NHPI固载的NHPI与助催化剂Co(OAc)2适宜的摩尔比为14∶1,主催化剂所含NHPI为底物的12(mol)%时,催化剂用量较为合适。固体催化剂CPS-NHPI具有良好的再循环使用性能。     

气相色谱-质谱法测定甲苯氧化产物的组成

在化纤公司甲苯氧化单元(01单元)中,甲苯与空气中的氧气在氧化反应催化剂醋酸钴的作用下生成苯甲酸,甲苯氧化反应如下:C6H5-CH3+3/2O2→C6H5-COOH+H2O,反应压力为106 Pa,反应温度为165℃.甲苯氧化反应转化率为15%,收率为91%.由于甲苯氧化反应转化率较低,为了提高反应转化率,我所化纤研究室对不同厂家所生产的醋酸钴催化剂进行了评选.在催化剂评选过程中,需要对甲苯氧化产物的组成进行分析.利用现有仪器,摸索实验操作条件,对甲苯氧化产物的组成进行了测定,发现样品中各组分分离良好,并对其中15种组分进行了定性定量分析,结果准确可靠,为醋酸钴催化剂的评选提供了数据依据.     

钴的羟胺酸类配合物催化对-二甲苯氧化反应研究

合成并表征了 3种羟胺酸类钴配合物 Co(OTPHA) 2 、Co(OTBHA) 2 和 Co(OTOHA) 2 ,并对比评价了它们催化对 -二甲苯均相液相氧化合成对 -甲基苯甲酸的活性和选择性 .考察了以纯氧为氧源 ,常压下反应温度、催化剂浓度、反应时间以及水对反应转化率和选择性的影响 .实验结果表明 ,不同分子结构的配体 ,可以通过其空间效应和电子效应对催化活性产生直接的影响 ,3种催化剂的活性顺序为 :Co(OTPHA) 2 >Co(OTBHA ) 2 >Co(OTOHA ) 2 .当反应温度为 110℃、催化剂浓度 1.0× 10 - 3mol/ L、反应 6 h时 ,催化剂 Co(OTPHA) 2 的对 -二甲苯转化率可达 33.9%、选择性为 86 .2 % .若提高反应温度和加大催化剂浓度 ,则会降低催化剂的活性 .反应中生成的水对氧化反应有抑制作用 ,应及时将反应中生成的水从体系中分出     

N-羟基邻苯二甲酰亚胺及其类似物催化下的分子氧氧化反应

本文综述了近年来N-羟基邻苯二甲酰亚胺（NHPI）及其类似物催化下分子氧氧化的各种反应,并对它们的催化机理作了简要介绍。NHPI与过渡金属离子组成的催化体系能高效的催化乙烷氧化为乙酸、环烷烃氧化为二元羧酸、甲苯氧化为苯甲酸、烯烃氧化为环氧化物、炔烃氧化为炔酮、酰胺氧化为酰亚胺;NHPI单独使用能催化金刚烷发生氧化羰基化反应、催化氧化醇制取过氧化氢;NHPI与有机助催化剂如：偶氮二异丁腈、溴化季铵盐、蒽醌、醇等也能催化分子氧氧化反应。     

钴分子筛催化剂的制备及其分子筛载体对环己烷氧化选择性的影响

为了考察催化剂载体的孔道结构和择形性能对环己烷部分氧化反应的影响,采用直接水热法制备出了Co/S-1,Co/TS-1以及Co/MCM-41分子筛催化剂.XRD,FT-IR和SEM结果表明合成的样品具有较高的结晶度,晶粒大小均匀,其活性组分钴进入了分子筛骨架.采用氧气为氧化剂,考察了合成的钴催化剂样品对环己烷部分氧化的催化性能,并与CoAPO-5、Co/A l2O3、均相Co(OAc)2.4H2O催化剂以及无催化氧化的结果进行了比较.实验结果表明:分子筛载体能利用其孔道结构和择形性能,降低环己醇(酮)选择性对环己烷转化率的依赖性,且反应的选择性随分子筛载体孔径的增加而下降.孔道较小的Co/TS-1和Co/S-1做催化剂时,过氧化物含量低,环己烷转化率可达5%以上,同时反应总选择性为95%左右.     

四羰基钴/咪唑离子液体在羰基化合成丙二酸二甲酯反应中的催化性能

采用原位法合成了不同类型的四羰基钴/咪唑离子液体催化剂, 并考察了其在氯乙酸甲酯羰基化反应中的催化性能. 研究了咪唑环上不同支链对催化活性的影响. 结果表明, 1-丁基-3-甲基咪唑羰基钴离子液体[Bmim][Co(Co)₄]不仅催化活性高, 选择性好, 而且对空气和水有较好的稳定性能. 在p_CO=2.0 MPa, 85 ℃, 反应3 h的条件下, [Bmim][Co(Co)₄]催化剂循环使用4次, 氯乙酸甲酯的平均转化率为94.3%, 丙二酸二甲酯的平均选择性和平均产率分别为98.5%和92.9%. 与传统的Na[Co(Co)₄]催化剂相比, [Bmim][Co(Co)₄]催化剂在保证高活性的条件下可以实现羰基钴催化剂的直接循环使用.     

β-二酮钴配合物催化空气氧化二苯甲醇反应的研究

研究了β-二酮钴催化空气氧化二苯甲醇生成二苯甲酮的反应．利用正交实验方法考察了反应温度、时间、N-羟基邻苯二甲酰亚胺(NHPI)用量、催化剂种类及用量对反应的影响．发现同一金属中低价态β-二酮金属配合物的活性较高，配体给电子能力强，催化活性就越高．当反应温度80℃、反应时间12h、NHPI为l0％、Co(acac)2为0．9％时，二苯甲醇的转化率高达97．6％．     

乙醇水蒸气重整Co/CeO2催化剂

 采用共沉淀法制备了Co/CeO2催化剂并将其应用于乙醇水蒸气重整制氢反应,考察了活性组分含量和焙烧温度对催化剂性能的影响. 结果表明,在原料气水∶乙醇∶N2摩尔比为3∶1∶16, 空速为40 L/(g·h)和反应温度为350～600 ℃的条件下, 经650 ℃焙烧的10%Co/CeO2催化剂对乙醇水蒸气重整制氢反应具有高活性和高选择性. 在500 ℃下进行的40 h稳定性测试中,该催化剂上的乙醇转化率始终接近100%, 反应后气体中的H2含量保持在65%左右. X射线衍射表征结果显示,焙烧后催化剂的主要物相组成为Co3O4和CeO2, 二者之间存在相互作用. Co/CeO2催化剂中钴的主要存在形式包括小晶粒的钴氧化物、大晶粒Co3O4和进入CeO2晶格的钴,Co3O4含量和焙烧温度的改变可影响催化剂中钴的存在形式. 由催化剂中高分散小晶粒的钴氧化物还原所得的金属钴是关键的活性组分.     

The aqueous phase nitration of phenol and benzoic acid studied through flow-gated capillary electrophoresis

The aqueous phase nitration of benzoic acid and phenol was investigated via on-line capillary electrophoresis (CE). The presence of nitrated benzoic acid and phenol was supported through appearance of corresponding molecular ion peaks in ESI-MS measurements, and speciation of the nitrated isomers is achieved via the on-line CE method. The nitrated isomers produced in both reactions were successfully separated in <4?min by addition of 15?mM β-cyclodextrin to the electrophoresis buffer. Sequential separations (on-line analysis) allowed the reaction kinetics to be described. For benzoic acid, reaction yields were low (2–3%) however, results suggest both 3- and 2-nitrobenzoic acid form in a 1–1.4 concentration ratio. In addition, 3-hydroxybenzoic acid also forms in significant quantity under our reaction conditions. For the nitration of phenol, the reaction occurred more rapidly with observed yields between ≈10–30% for individual isomers. The yield of 2-nitrophenol was higher than 4-nitrophenol by a ratio of ≈?1.7–2, but 3-nitrophenol was not detected. For both reactions, nitrated and hydroxylated aromatics were the major products and formation of higher molecular weight oligomers was not observed.     

The role of benzoic acid in proline‐catalyzed asymmetric michael addition: A density functional theory study

In asymmetric Michael addition between ketones and nitroolefins catalyzed by L ‐proline, we observed that it was benzoic acid or its derivatives rather than other proton acid that could accelerate the reaction greatly, and different benzoic acid derivatives brought different yields. To explain the experimental phenomena, a density functional theory study was performed to elucidate the mechanism of proline‐catalyzed asymmetric Michael addition with benzoic acid. The results of the theoretical calculation at the level of B3LYP/6‐311+G(2df,p)//B3LYP/6‐31G(d) demonstrated that benzoic acid played two major roles in the formation of nitroalkane: assisting proton transfer and activating the nitro group. In the stage of enamine formation from imine, the energy profiles of benzoic acid derivatives were also calculated to investigate the reasons why different benzoic acid derivatives caused different yields. The results demonstrated that the pK_a value was the major factor for p‐substituted benzoic acid derivatives to improve the yields, whereas for m/o‐substituted benzoic acid derivatives, both pK_a value and electronic and steric effects could significantly increase the yields. The calculated results would be very helpful for understanding the reaction mechanism of Michael addition and provide some insights into the selection of efficient additives for similar experiments. © 2012 Wiley Periodicals, Inc.     

Mechanistic Insights into Selectivity Control for Heterogeneous Olefin Oxidation: Styrene Oxidation on Au(111)

We demonstrate that intermolecular interactions, controlled by both oxygen and styrene coverage, alter reaction selectivity for styrene oxidation on oxygen‐covered Au(111). Several partial oxidation products are formed—styrene oxide, acetophenone, benzoic acid, benzeneacetic acid, and phenylketene—in competition with combustion. The maximum ratio of the yields of styrene oxide to the total CO₂ produced is obtained for the maximum styrene coverage for the first two layers (0.28 ML) adsorbed on Au(111) precovered with 0.2 ML of O. Furthermore, our reactivity and infrared studies support a mechanism whereby styrene oxidation proceeds via two oxametallacycle intermediates which, under oxygen‐lean conditions, lead to the formation of styrene oxide, acetophenone, and phenylketene. Benzoate, identified on the basis of infrared reflection absorption spectroscopy, is converted into benzoic acid during temperature‐programmed reaction. These results demonstrate the ability to tune the epoxidation selectivity using reactant coverages and provide important mechanistic insight into styrene oxidation reactions.     

离子液体中芳烃侧链分子氧催化氧化反应研究

分别以离子液体[Hex-mim]BF4, [Bmim]BF4, [Bmim]PF6和[Omim]BF4为溶剂, Co(Ⅱ), Mn(Ⅱ)或Ni(Ⅱ)/NHPI(AIBN)为复合催化剂, 考察了不同离子液体-催化剂体系中常压分子氧氧化芳烃侧链烷基的反应. 在[Hex-mim]BF4中, Co(Ⅱ)或Mn(Ⅱ)/NHPI可有效地催化芳烃侧链烷基的分子氧氧化. 在优化条件下, 乙苯、正丙苯和正丁苯分别以高达90%, 94%和93%的收率得到相应的芳香酮; 甲苯和对位取代甲苯以32%~47%的收率被氧化为相应的芳香酸. 离子液体及金属催化剂体系在减压下除水后, 可循环使用.     

钴催化的苯直接羰基化反应研究

研究了一种将苯直接羰基化合成苯甲酸的新型催化体系Co(OAc) 2/CCl3COOH/K2S2O8，考察了反应过程中催化剂、反应时间、温度、CO压力等因素 对反应收率的影响，结果表明在优化的反应条件下，苯甲酸收率可达到20％以上。 同时给出了可能的反应机理。     

Chemiluminescence Determination of Benzoic Acid Using A Solid-Phase Verdigris Reactor

Benzoicacidisacommonadditiveusedwidelyasfoodpreservativeandplasticizer.Itcouldpromoteseverereactiontoallergicpopulationevenatlowconcentrationlevel1.Routinemethodsfortheassayofbenzoicacidincludeschromatographic2-6,spectrophotometry7,8,capillaryelectrophoresis9-13andelectrochemicaltitration14.Stokes15etal.monitoredairbornebenzoicacidbasedonsurface-enhancedRamanscatteringtechniques.Thereisalsoreportonamicrobialsensorusingpseudomonasforbenzoicacidandtheirderivativesinaqua16.Interestofusinglumines…     

One-Pot Synthesis of Heterocyclic beta-Chlorovinyl Aldehydes Using Vilsmeier Reagent

3-Chloro-1H-indole-2-carboxaldehydes are obtained in moderate yields by the one-pot reaction of various substituted 2-[(carboxymethyl)amino]benzoic acids (1a-d) using Vilsmeier reagent (DMF/POCl(3)). The benzfused acyclic diacids analogous to 1a in which nitrogen was replaced by oxygen and sulfur also underwent the reaction smoothly. 3-Chloro-1H-pyrrole-2,4-dicarboxaldehyde was obtained as the only product by the reaction of N-carboxymethyl beta-alanine.     

Highly efficient asymmetric organocatalytic Michael addition of α,α-disubstituted aldehydes to nitroolefins under solvent-free conditions

A chiral pyrrolide-based diamine in combination with benzoic acid has been found to be an effective organocatalyst for Michael addition of α,α-disubstituted aldehydes with nitroolefins. The reaction provided the desired Michael products possessing all-carbon quaternary center with high yields (76–98%) and high levels of enantioselectivities (up to 97% ee) under solvent-free reaction conditions. The procedure presented is simple and makes this method suitable for practical use.     

Investigation of the formation of poly(ethylene terephthalate) with model molecules: Kinetics and mechanism of the catalytic esterification and alcoholysis reactions. I. Carboxylic acid catalysis (monofunctional reactants)

Monofunctional compounds (benzoic acid, heptyl alcohol, and 2-butoxy-ethanol) were used to investigate the kinetics of the esterification and the alcoholysis reactions. Carboxylic acids (benzoic acid) are the only catalysts present in the reaction medium. The factors which influence the kinetics of the esterification reaction were studied: the nature of the carboxylic acid (substituents on the benzene ring), the nature of the alcohol, the composition of the reaction medium (alcohol alone or with another solvent, ester, or water). The results point out for an acyl type (A_AC2) mechanism. The alcoholysis reaction needs the presence of carboxylic acid as a catalyst to occur significantly. A similar mechanism is proposed for both reactions: nucleophilic attack by the oxygen atom of the alcohol at the ion pair formed by protonation of the acid (esterification reaction) or by protonation of the ester (alcoholysis).     

Microwave-assisted synthesis,characterization, and antimicrobial activity of some odorant Schiff bases derived from naturally occurring carbonyl compounds and anthranilic acid

Nine odorant Schiff bases, namely 2-(4-methoxybenzylideneamino) benzoic acid, 2-(benzylideneamino) benzoic acid, 2-(3-phenylallylidene amino) benzoic acid, 2-(3,7-dimethyloct-2,6-enylideneamino) benzoic acid, 2-(3,7-dimethyloct-6-enylideneamino) benzoic acid, 2-(4-isopropylbenzylideneamino)benzoic acid, 2-(3,4-dimethoxybenzylideneamino) benzoic acid, 2-(1-phenylethylideneamino) benzoic acid, and 2-[(4-(2,6,6-trimethylcyclohex-2-enyl)-but-2-enylideneamino)benzoic acid, were prepared by condensation of anthranilic acid with corresponding naturally occurring carbonyl compounds (anisaldehyde, benzaldehyde, cinnamaldehyde, citral, citronellal, cuminaldehyde, veratraldehyde, acetophenone, and α-ionone) employing conventional and microwave irradiation methods. These compounds were characterized with the aid of elemental and spectral (FT-IR, ¹H NMR, and ¹³C NMR) analysis. Microwave irradiation method was efficient in terms of reduced reaction time, solvent use, and increased yields of these compounds without affecting their olfactory characteristics. These Schiff bases also exhibited olfactory characteristics for various fragrance compositions and varied antimicrobial activity against Aspergillus niger, Penicillium chrysogenum, Staphylococcus aureus, and Escherichia coli.