甲烷氧化偶联催化剂的研究

甲烷氧化偶联是化学工作者十分重视的新课题,并做了许多研究工作,Benson以氯为氧化剂在1700℃高温下反应^[1],Keller等使甲烷在金属氧化物格子氧上反应^[2],Hinsen等以PbO/Y-Al₂O₃做催化剂,氧做氧化剂进行偶联^[3],但乙烯和乙烷的选择率很低,J. H. Lunsford等则用Li₂O/MgO做催化剂,氧为氧化剂把乙烯和乙烷的总收率提高到19.4％^[4],但乙烯的收率低于乙烷。     

甲烷氧化偶联CaF2／Sm2O3催化剂的研究

甲烷氧化偶联ＣａＦ_２／Ｓｍ_２Ｏ_３催化剂的研究周水琴，龙瑞强，黄亚萍，万惠霖，蔡启瑞（厦门大学化学系，固体表面物理化学国家重点实验室，厦门，３６１００５）关键词甲烷氧化偶联，氟化钙，三氧化二钐，离子交换，氧物种甲烷氧化偶联制乙烯是催化领域中最活跃的?..     

La2O3/BaCO3上甲烷氧化偶联反应动力学与历程

以8％La_2O_3/BaCO_3为催化剂,用无梯度反应器,在720～800℃温度范围内,通过改变甲烷与氧分压进行了一系列的甲烷氧化偶联反应动力学测量,确定了该反应的反应历程。乙烷和大部分CO_x(主要是CO_2)是甲烷氧化的一次产物。乙烯是乙烷串行反应的产物。用幂式动力学方程拟合动力学试验数据,估算了各步反应速度方程的动力学参数。还用脉冲反应技术与过渡应答技术证明了参与活化甲烷的是催化剂表面上的可逆吸附氧。     

乙烷在氧化镍上催化氧化脱氢的反应机理研究

应用O~2-TPD,脉冲实验,原位Weiss磁测量以及TAP(temporalanalysisofproducts)技术对NiO上的乙烷氧化脱氢制乙烯催化作用机理进行了研究。结果表明,NiO中的非化学计量氧表现出与气相氧交换的可逆性,其中在较低温度下脱附的α氧(很可能是O~2^-,O~2^2^-)仅存在于催化剂表面,与气相氧交换迅速,而较高温下脱附的β氧(很可能是O^-)不仅存在于催化剂表面,还存在于催化剂体相。β氧较α氧表现出更高的乙烯选择性。在反应条件下,Ni均应处于高氧化态(Ni^(^2^+^δ^)^+,0≤δ≤1),一旦催化剂中有微量Ni^0生成,乙烷便发生裂解反应,乙烯选择性立即降为零。乙烷在NiO上的氧化脱氢(ODHE)的可能反应机理为:首先乙烷与NiO中的非化学计量氧O~n(~s~)作用脱除一个α-H生成乙基自由基,然后进一步脱除一个β-H生成乙烯,乙烯生成的整个过程是在催化剂表面上进行的;副产物CO~2是由表面乙烯进一步氧化(很可能是与O~2^-,O~2^2^-作用)生成的。失去O~n~(~s~)的NiO在反应体系(一定的氧分压)中,重新生成含非化学计量氧的NiO。     

微波场对固态氧离子导体上的甲烷氧化偶联的影响

研究了微波场下甲烷在具有δ－Ｂｉ２Ｏ３结构的固态氧离子导体上氧化偶联反应行为。与常规加热条件下的反应结果相比较，微波辐射下的反应有上特点：（１）在达到相同甲烷转化率时，微波辐照下所需床层温度要远低于常规加热条件下所需床层温度；（２）微波辐照下，甲烷氧化偶联产物中Ｃ２烃的选择性普遍较高，在低温区尤为突出。微波场下甲烷偶联产物乙烷、乙烯的再氧化得到一定程度的抑制，致使微波场下的甲烷氧化偶联反应通常有较     

稀土氧化物催化和表面化学：I.CeO2和Pr6O11的表面羟基及其反应活…

利用ＦＴ－ＩＲ、同位素技术和内循环反应等方法考察了ＣｅＯ２和Ｐ６Ｏ１１的表面羟基及其与ＣＯ反应的活性。ＣｅＯ２和Ｐｒ６Ｏ１１经高温脱气处理后表面大量的碳酸基和羟基脱附。但部分残留的表面羟基反应活性很高，在２００℃甚至更低温度可与ＣＯ反应形成表面甲酸基物种。当温度超过３００℃时，表面甲酸基物种被表面晶格氧进一步氧化为表面碳酸基物种，但部分表面羟基又复原。认为经高温脱气处理后造成表面配位不饱和中心并使     

稀土氧化物的催化和表面化学I．CeO_2和Pr_6O_（11）的表面羟基及其反

利用ＦＴ－ＩＲ、同位素技术和内循环反应等方法考察了ＣｅＯ＿２和Ｐ＿６Ｏ＿１１的表面羟基及其与ＣＯ反应的活性。ＣｅＯ＿２和Ｐｒ＿６Ｏ＿１１经高温脱气处理后表面大量的碳酸基和羟基脱附。但部分残留的表面羟基反应活性很高，在２００℃甚至更低温度可与ＣＯ反应形成表面甲酸基物种，当温度超过３００℃时，表面甲酸基物种被表面晶格氧进一步氧化为表面碳酸基物种，但部分表面羟基又复原。认为经高温脱气处理后造成表面配位不饱和中心并使表面羟基得到活化，故易与ＣＯ反应形成表面甲酸基。表面甲酸基是ＣＯ氧化为ＣＯ＿２的中间物，表面羟基起活化ＣＯ和形成表面甲酸基中间物的作用。     

掺杂SrTiO3体系上甲烷氧化偶联反应的研究—活性氧物种的作用

本文采用循环氧化还原法,脉冲反应及TPD等实验手段对钙钛矿型氧化物掺杂SrTiO_3体系上甲烷氧化偶联反应中的活性氧物种的作用进行了研究.结果表明,催化剂由于掺杂产生的未被充分还原的氧物种(O~(α-)(0<α<2)是活化甲烷并促使其发生偶联反应的主要的活性中心,而表面晶格氧(O_L~(2-))则主要使甲烷深度氧化;消耗掉的未被充分还原的氧或晶格氧可以在高温下氧气氛中氧化复原.对于掺杂的SrTiO_3样品,体相中的氧在惰性气氛或还原气氛中可以向表面扩散.吸附氧可能不直接与甲烷作用而主要通过催化剂表面活性氧物种(O~(α-)或O_L~(2-))而起作用.     

在Li-Nd-Zn-Mg氧化物上甲烷氧化偶联

天然气资源丰富,其中主要成分为甲烷.以甲烷为原料开发化工产品一直引起人们的重视.1982年Keller首先提出甲烷氧化偶联制乙烯、乙烷的催化过程,为开拓廉价乙烯原料路线提供了新的可能途径,从而引起各国催化工作者的重视.近年来,此催化过程的乙烯及乙烷的收率(y_(02))已提高到10—30%之间.各国都在努力开发活性高及选择性好的催化剂,促使此催化过程工业化。本文研究了Li-Nd-Zn-Mg氧化物甲烷氧化偶联催化剂,对反应条件进行了初步考察,乙烯及乙烷的收率y_(02)达到30.8%。     

锆促进纳米氧化镍催化剂的制备及其对乙烷氧化脱氢制乙烯的催化性能

 用尿素均匀沉淀法制备了不同含量锆促进的纳米氧化镍催化剂,并考察了其对乙烷氧化脱氢制乙烯的催化性能. 结果表明,纯纳米氧化镍在优化条件下的最高乙烯收率为21.7%; 而锆促进的纳米氧化镍催化剂对乙烯选择性和高温抗乙烷裂解性能都有明显改善. 15%ZrO2-NiO表现出最佳的催化性能,在410 ℃下,乙烷转化率为61.5%,乙烯选择性为68.6%,乙烯收率为42.2%; 该催化剂在420 ℃经36 h反应,乙烯收率仅下降约4%,粒子没有发生明显的团聚,表现出较好的稳定性. XRD结果表明,锆促进的纳米氧化镍粒子较纯纳米氧化镍粒子小,平均粒径为5～7 nm; 助剂锆以无定形的ZrO2形式存在. O2-TPD-MS结果表明,锆的加入提高了催化剂中较高温度下脱附的氧物种量,降低了较低温度下脱附的氧物种量. H2-TPR结果显示,锆促进的纳米氧化镍催化剂较纯纳米氧化镍难以完全还原.     

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.