无碱条件下Au/ZnO选择性催化氧化1,3-丙二醇合成3-羟基丙酸甲酯

采用溶胶-沉积法合成了高选择性的Au/ZnO催化剂,用于1,3-丙二醇选择性氧化酯化为3-羟基丙酸甲酯的反应.研究了保护剂PVA用量、金溶胶合成温度、金负载量及催化剂循环利用对反应的影响,且优化了反应温度和反应压力,并对催化剂进行了XRD和TEM表征.结果表明,PVA∶Au(m/m)=1∶4、金溶胶合成温度25℃、金负载量1%的Au/ZnO对目标反应的催化活性最好,在100℃和Po2=2MPa的条件下1,3-丙二醇的转化率达82.8%,产物3-羟基丙酸甲酯的选择性达95.4%.Au纳米粒子的粒径影响催化性能,在Au平均粒径为2.8~6.1nm的范围内,产物选择性随Au纳米粒子的粒径的减小而增大,平均粒径在2.8~4.8nm的范围内时,催化剂具有较好的产物选择性(大于90%);Au/ZnO催化剂循环利用4次后催化性能(转化率和选择性)无明显下降;并推测了无碱条件下Au/ZnO选择性催化氧化1,3-丙二醇合成3-羟基丙酸甲酯的反应机制.     

丙烯气相直接环氧化Au/TiO2催化剂的研究

在H2和O2共存条件下，金催化剂催化丙烯气相直接环氧化反应是近年来发展起来的一种新型环氧丙烷(PO)合成技术．本文采用沉积沉淀法制备了一系列Au／TiO2催化剂，考察了反应溶液的pH值、Au负载量、沉淀剂以及焙烧温度等因素对催化剂丙烯环氧化催化性能的影响．结果表明制备条件对催化性能有明显影响：反应溶液的pH值为7．5及Au负载量为2．4％时所得催化剂活性最好；当以Na2CO3、NaOH等含Na^ 物质作为沉淀剂时，催化性能明显优于Li^ 、K^ 等其它碱金属离子；400℃焙烧制得的催化剂活性较好，在50℃低温反应条件下，环氧丙烷得率可达1．3％．HRTEM结果表明，催化剂中Au组分高度分散于载体表面，且随着焙烧温度的增加Au粒因发生聚集而变大，从而影响了催化剂的活性．表面XPS分析证实，活性较好的Au／TiO2催化剂中活性组分Au除部分呈氧化态外，主要是以金属态的形式存在．     

负载型介孔Au/NiO催化剂的制备、表征与光谱特性研究

采用还原法和沉积-沉淀法制备了介孔Au/NiO催化剂,并运用XRD、N2吸附-脱附、UV-Vis、FTIR、和XPS等方法对其进行了表征,考察了制备方法对Au/NiO催化剂物理化学性质和丙烷氧化脱氢制丙烯反应催化性能的影响.实验结果表明Au/NiO催化剂具有一定的低温催化活性,而还原法制备的催化剂催化性能好于沉积-沉淀法制备的催化剂,反应温度350℃时,还原法制备的Au/NiO催化剂的丙烷转化率和丙烯选择性分别达到25.1%和39.8%.制备方法对表面Au的价态分布、颗粒大小及分散度均有影响.催化剂表面Auδ+物种是催化剂的主要活性组分.     

Te掺杂对MoPO/SiO2催化剂上丙烷选择氧化制丙烯醛反应的影响

 考察了Te的添加及Te含量对MoPO/SiO2催化剂催化丙烷选择氧化制丙烯醛反应性能的影响. MoPO/SiO2催化剂对丙烷选择氧化制丙烯醛反应的中间产物丙烯选择性较高,而Te的添加促进了丙烯向丙烯醛的转化. N2吸附、XRD、Raman、XPS、H2-TPR、丙烷脉冲、NH3-TPD和Py-IR等实验结果表明,催化剂添加Te后虽然比表面积有所下降,但单位比表面积上的酸量增加,催化剂低温可还原性得到改善,从而有利于丙烷的转化. Te可能有利于丙烯α-H的脱除和/或烯丙基的插氧反应.     

氢氧混合体系下Ag／TS－1催化剂上丙烯的高效环氧化反应

 在氢氧混合体系中，沉积-沉淀法制备的Ag/TS-1催化剂对丙烯环氧化反应具有高的催化活性和选择性。本文主要考察了载体TS-1的硅钛比和反应温度对催化剂性能的影响。结果表明：当载体TS-1硅钛比为64，反应温度150℃时，2wt%Ag/TS-1催化剂表现出优异的催化性能，丙烯转化率和环氧丙烷选择性可分别达1.37%和93.51%。     

金属载体强相互作用增强Au/TiO2催化剂在3-硝基苯乙烯选择性加氢反应的活性

自Haruta与Hutchings于上世纪八十年代末发现金纳米催化剂优异的反应活性以来,科研人员对金催化的应用领域进行了广泛而深入地研究.对金催化科学和应用领域的研究一直在进行.大量的研究表明,金催化剂在各种选择性氧化反应中具有优异的催化性能(高活性和高选择性).然而,在催化加氢反应中,尽管金催化剂相比于铂族金属显示出优越的选择性,但是由于金催化剂选择性加氢反应的活性较差,使其在选择性催化加氢反应中的应用受到了极大的限制.研究表明,金催化剂较弱的活化氢气能力是其催化加氢反应活性低的主要原因.研究发现,氢气活化的活性中心可能是界面、负价金、低配位的金原子等.金催化剂具有明显的载体效应,金属-载体之间的相互作用能够显著地改变金催化剂的催化性能.Tauster等研究发现,铂族金属与还原性载体之间存在强相互作用,能够引发载体包覆金属表面,并且使得电子从载体向金属迁移,导致金属带负电.受金属-载体强相互作用(SMSI)效应的启发,本文探究了Au/TiO2催化剂中SMSI对金催化剂加氢性能的影响.在H2或O2气氛下高温焙烧Au/TiO2,获得一系列金催化剂(Au/TiO2-TA,T为焙烧温度(oC):300、400、500和600;A为气氛:H2或O2).对比在3-硝基苯乙烯(3-NS)选择性加氢反应中的活性发现,Au/TiO2-500H的TOF值是Au/TiO2-500O的3.3倍;动力学测试表明,Au/TiO2-500H和Au/TiO2-500O的反应表观活化能分别为79.5和105.1 kJ/mol.这表明两类催化剂催化活性中心的结构存在差异.X射线光电子能谱测试结果表明,Au/TiO2-H样品中Au带部分负电,而Au/TiO2-O中Au显示为金属态.HAADF-STEM和EELS显示,Au/TiO2-H中Au NPs的表面有TiOx物种,增加了Au-TiO2的界面.EPR结果表明,Au/TiO2-H中存在表面Ti3+物种,而Au/TiO2-O样品中则没有.为确认加氢反应的活性中心到底是界面还是负价金物种,本文探究了不同温度下氢气处理的Au/TiO2的结构与性能的关系,发现Au/TiO2-300H/400H/500H催化剂都显示出较好的催化3-NS加氢活性,而Au/TiO2-600H虽然具有更多的负价金物种,但是3-NS选择性加氢反应的活性反而降低,因此,负价金不是活性中心.这是因为不同温度处理的Au/TiO2-H样品中,SMSI的强弱不同,在300、400、500 oC下,SMSI能够增加Au-TiO2的界面长度,从而增强了3-NS加氢反应的活性;而温度达到600 oC,SMSI效应太强,Au NPs被包覆更密实,导致Au/TiO2-600H的3-NS选择性加氢反应的活性下降.密度泛函理论计算表明,Au/TiO2-H样品具有更低的H2解离活化能以及氢转移活化能.氢氘交换反应也进一步验证了SMSI有利于H2的活化.     

植物还原法制备负载型金纳米催化剂催化乙醇选择氧化反应

采用侧柏叶提取液还原氯金酸制备负载型金纳米催化剂,通过乙醇选择氧化反应,筛选出催化性能较好的TiO2载体。以TiO2载体为载体,考察了Au负载量、焙烧温度、催化剂用量、碳酸氢钠添加量及催化剂反应条件(时间、温度、压力)等因素对乙醇选择氧化反应的影响。结果表明,1.5%Au/TiO2催化剂(Au负载量为1.5%,质量分率,下同)催化乙醇选择氧化反应性能最佳,产物为乙醛、乙酸乙酯和缩醛,0.5%碳酸氢钠添加剂可抑制缩醛的生成,并可显著提高乙醇转化率和乙酸乙酯选择性。通过优化催化反应条件(1.5%Au/TiO2催化剂焙烧温度为400℃、用量为0.4 g、反应温度为100℃、氧气压力为3 MPa、反应时间为3 h时),乙醇转化率为47.9%,乙酸乙酯选择性为89.1%。     

纳米Au/TS-1催化剂的制备及用于甲醇羰基化体系

采用负压沉积沉淀法、等体积浸渍法、负压等体积浸渍法等方法制备了纳米Au/TS-1催化剂,研究了深床焙烧和等离子体焙烧,以及焙烧温度和焙烧气氛对催化剂中纳米金粒子大小和催化性能的影响,并采用ICP、TEM、XRD、UV-vis、XPS对催化剂金粒子进行了物化性能表征,采用甲醇羰基化制乙酸甲酯反应表征催化性能.结果表明,不同制备方法、不同焙烧方法、不同焙烧温度和焙烧气氛对负载型纳米Au/TS-1沸石分子筛催化剂中金粒子的大小、形貌、物化性质和催化性能有明显影响.其中,3种制备方法中,氢气气氛下焙烧均比空气和氮气气氛下焙烧得到的催化剂的金粒子尺寸更小,分散更均匀,约为5~10 nm.与其它方法相比,负压沉积沉淀法可制得分散更均匀的金粒子,Au/TS-1沸石催化剂中的金粒子尺寸更小,平均粒径为1~5 nm.催化性能评价结果显示,3种方法制备出的负载型金催化剂用于催化甲醇羰基化制乙酸甲酯反应体系中,甲醇的转化率分别为85%、75%、60%,乙酸甲酯选择性可高达68%,反应温度200℃为最好.     

Au/Fe2O3催化剂的制备及其对富氢气体中一氧化碳选择性氧化的催化性能

 采用共沉淀法制备了1.5%Au/Fe2O3催化剂,考察了加料方式对Au/Fe2O3催化剂化学组成及其催化富氢气体中CO选择性氧化性能的影响. 结果表明,正加法制备的Au/Fe2O3催化剂的性能明显好于反加法制备的催化剂,80 ℃时前者对富氢气体中CO选择性氧化反应的转化率为94%,CO2选择性为65%,连续反应10 h,催化剂活性没有变化. XRD,XPS和TEM等的测试结果表明,正加法制备的Au/Fe2O3催化剂中金粒子的平均粒径为2～4 nm,金粒子高度分散在载体上,并与载体之间发生了较强的相互作用,从而表现出较高的催化性能.     

负载型金催化剂催化乙醇选择氧化反应

选择不同氧化物(Al2O3,SiO2,TiO2,MgO)和H-ZSM-5分子筛作为载体,以尿素为沉淀剂,采用沉积-沉淀法制备了一系列负载型金催化剂.采用X射线衍射、电感耦合等离子体发射光谱、程序升温还原、NH3程序升温脱附和透射电镜等技术对催化剂样品进行了表征,并测定了催化剂对乙醇选择氧化反应的催化性能.选择Au/Al2O3催化剂,考察了金负载量、反应条件(温度、压力、时间)和添加剂对乙醇选择氧化反应的影响.结果表明,所制备的Au/Al2O3催化剂的金负载率较高,金粒子较小(3～4 nm)且分布均匀.载体对金催化剂催化乙醇氧化反应有显著影响,主要产物为乙醛、乙酸乙酯和缩醛.以TiO2为载体时,乙醇转化率较高.以Al2O3为载体时,乙酸乙酯选择性较高;少量碱性添加剂可抑制缩醛的生成,并可提高乙醇转化率和乙酸乙酯选择性.在优化的条件下,乙醇转化率可达4.7%,乙酸乙酯选择性可达93.5%.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.     

Synthesis of pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles by Curtius reaction in Morita-Baylis-Hillman derivatives

Synthesis of substituted pyrrolo[1,2-a]pyrazines and pyrazino[1,2-a]indoles from the Morita-Baylis-Hillman derivatives of acrylates via saponification followed by Curtius reaction is described.     

正丁胺对激光染料荧光谱影响的研究

用正丁胺作为碳源,采用射频辉光放电制备碳膜,选用激光染料R6G和聚乙二醇混合液作为蒸气源,采用单源热蒸发,在蒸发室与染料同时沉积得到混合膜,用拉曼光谱和红外光谱分析了碳膜的结构和键合方式,分析表明:碳膜中存在胺基团和氢原子.混合膜的荧光谱测量结果表明,认为正丁胺对染料荧光谱的影响是因为胺基和氢原子的存在.     

Cu0-catalysed 1,3-dipolar cycloadditions of α-amino acid derived N,N-cyclic azomethine imines to ynones

A series of 20 CuAIAC reactions between eight 4-acylamino substituted pyrazolidine-3-one-1-azomethine imines and four terminal ynones were performed using Cu⁰ as catalyst. The corresponding fluorescent cycloadducts were obtained in very high yields upon simple workup. Thus, Cu-metal turned out to be a better catalyst than Cu^I in terms of yield and ease of isolation. Availability of azomethine imines, mild reaction conditions, and simple workup enable a “click” access to libraries of densely substituted 2,3-dihydro-1H,5H-pyrazolo[1,2-a]pyrazol-1-ones. Reactivity of differently substituted dipoles was evaluated experimentally and by quantum chemical methods (DFT).     

Synthesis and antioxidative/anti-inflammatory activity of novel fullerene–polyamine conjugates

(E)-4-(Fullerenopyrrolidin-1-yl)-3-methylbut-2-enoic acid and its corresponding succinimidyl ester, readily obtained through Prato-type modification of C₆₀, were used for the selective N-acylation of polyamines. The thus obtained conjugates were evaluated for their antioxidative and anti-inflammatory activity and their cytotoxicity was determined. Members of this family of compounds showed interesting anti-lipid peroxidation, anti-lipoxygenase and anti-inflammatory activity and comparable cytocompatibility to spermidine.