催化苯羟基化反应的高效介孔VOx/SBA-16催化剂

利用浸渍法制备了介孔SBA-16负载高分散氧化钒催化剂(VOx/SBA-16),并使用XRD,TEM,N2物理吸附和Raman光谱对其进行了表征.结果表明,制备的VOx/SBA-16催化剂保持了SBA-16立方笼状孔结构,钒物种主要高度分散在SBA-16载体孔内.钒含量为7·3%的VOx/SBA-16催化剂在催化苯羟基化反应中表现出优异的催化性能.这是由于催化剂表面形成了高分散的VO4物种和纳米结构V2O5微晶.     

纳米Fe2O3-K2O催化剂的制备及其催化乙苯脱氢性能

采用浸渍-热分解法制备了纳米Fe2O3-K2O催化剂,并在常压和520～580℃的条件下,考察了其对乙苯催化脱氢反应的催化性能.结果发现,纳米Fe2O3-K2O催化剂表现出很好的活性和稳定性.在550℃,N2/H2O/乙苯摩尔比为30.7/10/1和WHSV=0.43h-1的条件下,纳米Fe2O3-K2O催化乙苯脱氢的转化率为71.9%,苯乙烯选择性为91.1%.透射电子显微镜和X射线衍射测试结果表明,氧化铁的粒径为10～14nm.催化剂的尖晶石结构和高比表面积是其表现出高催化性能的主要原因.     

CO2 气氛下 MCF 负载氧化钒催化剂上乙苯脱氢反应

 以介孔氧化硅泡沫 MCF 为载体合成了一系列负载型氧化钒催化剂 (V 含量为 2%?10%). 采用 N2 吸附、X 射线衍射和 H2 程序升温还原对 V/MCF 催化剂的结构和织构性质进行了表征, 并评价了催化剂在 CO2 气氛下的乙苯脱氢性能. V/MCF 催化剂具有较高的乙苯脱氢活性, 其中 V 含量为 6% 的催化剂具有最高的反应活性. V/MCF 催化剂的乙苯脱氢活性显著高于 V/MCM-41, 这是由于前者具有较高的可还原性以及较好的扩散性能. CO2 气氛下的乙苯转化率明显高于 N2 气氛下的, 这归因于 CO2 与乙苯发生氧化脱氢, 并通过逆水煤气变换反应在线除去脱氢反应生成的氢.     

VOx/SBA-15催化剂上甲苯气相部分氧化

采用等体积浸渍法制备了不同负载量的VOx/SBA-15催化剂。UV-Vis和H2-TPR等表征结果表明,在较低钒负载量下,钒物种的分散程度较高,主要以孤立的VO4 3－以及少量聚合体V－O－V形式存在;钒负载量较高时会有大量的聚合体V－O－V甚至晶相V2O5出现,而且,催化剂的酸性随着钒物种的高度分散而降低。甲苯气相部分氧化反应结果表明,随着钒负载量的提高,苯甲醛的选择性先升后降,CO、CO2等选择性逐渐提高。这是由于催化剂存在大量的聚合体V－O－V和晶相V2O5时,聚集态钒物种表面较多的酸量促使苯甲醛深度氧化。在相同钒负载量下,催化剂VOx/SBA-15的钒物种分散状态优于VOx/MCM-41和VOx/SiO2,从而使得催化剂VOx/SBA-15呈现较高的苯甲醛选择性。     

MSU-2负载的Sb-V复合氧化物催化剂上甲烷选择性氧化制

 制备了MSU-2负载的Sb-V复合氧化物催化剂,并将其用于以O2为氧化剂的甲烷选择性氧化制甲醛. 结果表明,Sb-V-O/MSU-2 复合氧化物催化剂保持了MSU-2分子筛的孔结构,在催化反应中表现出较高的甲烷转化率和可观的甲醛选择性. 其甲醛单程收率高于Sb2O5/SiO2和VOx/SBA-15催化剂. 在Sb2O5负载量为5%, V2O5负载量为1.12%的Sb-V-O/MSU-2催化剂上甲醛的单程收率为2.9%.     

V_2O_5-CeO_2/SBA-15催化剂的制备及氯苯催化燃烧的性能研究

以介孔分子筛SBA-15为载体,采用等体积浸渍法分别制备了不同V负载量(4%～15%(质量分数))的V2O5/SBA-15及经过铈掺杂后的V2O5-CeO2/SBA-15催化剂,考察了催化剂对氯苯的催化燃烧性能,用XRD,UV-vis,SEM和TEM对催化剂进行了表征。活性评价结果表明,当V质量分数在10%时的V2O5/SBA-15催化剂对氯苯催化燃烧性能最好,在掺杂10%的稀土Ce后,催化燃烧氯苯的活性得到明显提高。表征结果表明,V2O5和CeO2均分散在SBA-15的孔道骨架上,没有破坏SBA-15的中孔结构。     

Cu-Zn-Zr/SBA-15介孔催化剂的制备及CO2加氢合成甲醇的催化性能

以具有骨架结构的SBA-15介孔分子筛为载体,采用浸渍法合成了具有高比表面积、不同金属氧化物含量的Cu-Zn-Zr介孔催化剂CZZx/SBA-15(x=0.3,0.4,0.5,0.6).采用N2吸附-脱附(BET)、X射线衍射(XRD)、H2程序升温还原(H2-TPR)、CO2吸附(CO2-TPD)和透射电子显微镜(TEM)等手段对样品进行了表征.在固定床反应器上评价了其CO2加氢合成甲醇的催化性能.实验结果表明,CZZx/SBA-15催化剂具有介孔结构,负载的Cu O,Zn O和Zr O2能够很好地分散在表面,并且负载氧化物晶粒尺寸不同.催化剂的铜比表面积SCu与甲醇催化活性呈近似线性关系,其中CZZ0.4/SBA-15催化剂表现出最大甲醇选择性(54.32%),与CZZ相比,甲醇选择性增加24.85%.随着金属氧化物负载量的增大,催化剂比表面积和SCu明显减小,甲醇选择性与收率也相应减小,负载型CZZx/SBA-15催化剂表面结构对CO2加氢合成甲醇反应活性起关键作用.     

Pt／SBA-15、Pt／SBA-16催化剂的合成、表征及甲烷催化燃烧性能

以Na2SiO3.9H2O为硅源,H2PtCl6为铂源,水热法一步合成了Pt质量分数约1%的Pt/SBA-15和Pt/SBA-16催化剂.采用XRF、XRD、HRTEM等方法对样品进行了表征.在微型固定床反应器中考察了催化剂的甲烷催化燃烧性能.结果表明:合成的Pt/SBA-15和Pt/SBA-16样品分别具有SBA-15和SBA-16的高度有序的介孔结构;通过这种简便、低成本的方法可将Pt颗粒高分散地引入到样品的孔道内;催化剂表现出了较好的甲烷催化燃烧性能,在常压、原料气为含3.5%CH4的空气和GHSV=6000mL/(gcat.h)的反应条件下,在大约580℃下甲烷即可完全转化.     

VOx/SiO2-Al2O3催化剂催化苯羟基化制苯酚

以硅溶胶为硅源、偏铝酸钠为铝源及环己胺合成SiO2-Al2O3复合氧化物,并采用水热合成法合成了VOx/SiO2-Al2O3催化剂。采用XRD、SEM、TEM、XPS、NH3-TPD、N2物理吸/脱附等手段对此催化剂和复合氧化物微观结构进行表征分析。由表征结果可知钒活性中心能够高分散于此复合氧化物表面,VOx/SiO2-Al2O3催化剂呈现层片积雪状;当钒的含量为4%时,催化剂中V4+含量最大且总酸量契合于此反应所需要的催化酸环境。探究了4%VOx/SiO2-Al2O3催化剂对苯羟基化制苯酚反应的催化性能,结果表明：基于高分散活性中心、V4+含量最大及载体酸性环境等优点而表现出良好的催化性能,苯转化率为48.1%,苯酚选择性为99.6%。     

PtZn-Sn/SBA-15合成、表征及对丙烷催化脱氢性能

以SBA-15为载体,利用浸渍法制备了单、双和三金属Pt催化剂,并对催化剂进行了N2物理吸附(BET)、程序升温还原(H2-TPR)、H2-化学吸附、透射电子显微镜(TEM)和O2-脉冲等技术表征,研究了它们对丙烷催化脱氢(CDH)制丙烯反应的催化性能。研究结果表明,Pt在三金属催化剂中的分散性能最好,并且部分负载组分可以进入SBA-15的孔道,Pt的分散度达到29%,Pt粒子尺寸为3 nm左右。三金属催化剂表现出优越的脱氢性能,这主要归结于载体的弱酸性、活性组分和助剂、载体之间的相互作用及Zn对Pt的电子调控作用。这些因素使催化剂的积炭量较低,因而具有较高的脱氢稳定性和极高的选择性。     

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.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

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.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.