Redox property of Co3O4/CeO2 and the effect of reaction conditions on its performance in CO oxidation

采用沉淀氧化法制备了Co3O4/CeO2催化剂.运用XRD、BET和TPR表征手段,考察了不同钴铈比及焙烧温度对钴铈复合氧化物物理及化学性能的影响,并分别在干、湿条件下进行了一氧化碳氧化反应研究.结果表明,与纯的Co3O4相比,在不同比例的Co3O4/CeO2均经723 K焙烧的各种催化剂中,钴铈原子比为9∶1的复合氧化物粒径较小,比表面积较大,说明适当比例铈的添加能使Co3O4具有较小的粒径.此氧化物经538 K温度焙烧制得的钻铈比为9∶1的复合氧化物中Co3O4平均粒径为7.2nm,BET比表面积为167.6 m2/g.经TPR考察发现其具有最优的氧化还原性能.     

镍基催化剂上乙醇水蒸气重整反应的研究

考察了载体对Ni催化剂乙醇水蒸气重整制氢反应性能的影响。结果表明，Ni/CeO2催化剂具有较好的低温活性和氢气选择性。对Ni担载量和焙烧温度考察发现，400℃焙烧的15%NiCeO2催化剂具有较好的催化性能；继续升高焙烧温度引起NiO和CeO2粒子的显著增大,导致对氢气选择性的降低。较小的Ni和CeO2粒子有利于乙醇水汽重整反应的进行，而大的粒子倾向于乙醇的分解反应。 350℃时,在反应过程中分别添加CO、CO2和CH4的结果表明没有发生CO和CO2甲烷化反应,而发生了一定程度的CH4水汽重整反应。     

以稀土氧化物为助剂的乙醇水蒸气重整制氢催化剂研究

采用浸渍法,以γ-Al2O3为载体,稀土(Ce,Nd)氧化物为助剂,金属Ni为活性物,制备了用于乙醇水蒸气重整制氢的复合催化剂.该类催化剂在400～550 ℃的较低温度范围内具有较高的氢气产率.不管助剂为何种稀土(Ce,Nd)氧化物,当其含量一定时,活性组分Ni的含量为15%的催化剂均具有最佳活性;当活性组分Ni一定,助剂的含量为10%时,催化剂的产氢率最大.采用10%CeO2/15%Ni/γ-Al2O3催化剂时,乙醇重整制氢的产氢率可达5.2以上.     

乙醇水蒸气重整制氢催化剂Ni/Al2O3的研究

采用壳多糖螯合、浸渍法制备出Ni/Al2O3催化剂,并用BET、XRD、TG等方法对催化剂的性能、结构进行表征.通过在常压固定床流动体系中进行乙醇水蒸气重整制氢反应,讨论和评价了催化剂的性能.结果表明,10%Ni/Al2O3催化剂对乙醇水蒸气重整制氢表现出较好的活性.在反应温度高于500℃、水醇比为3∶1时,乙醇转化率100%,H2选择性在68%以上,增大水醇比可使H2选择性适度提高.     

LaNiO3的焙烧温度对甲醇水蒸气重整制氢CuO/LaNiO3催化剂的影响

采用溶胶凝胶法合成了LaNiO_3钙钛矿型氧化物载体,再采用浸渍法制备了CuO/LaNiO_3催化剂,并通过XRF、XRD、BET、H_2-TPR和XPS等手段对催化剂进行了表征,考察了LaNiO_3钙钛矿的焙烧温度对CuO/LaNiO_3催化剂结构及其催化甲醇水蒸气重整制氢性能的影响。结果表明,载体焙烧温度主要影响了催化剂的表面晶格氧缺位,活性组分和载体间的相互作用。当载体焙烧温度为800℃时,催化剂表面氧空穴较多,活性组分与载体间相互作用较强,因此,催化甲醇水蒸气重整制氢活性较好。     

CeO2改性Cu/Al2O3催化剂上甲醇水蒸气重整制氢

研究CeO2改性Cu/Al2O3催化剂上甲醇水蒸气重整制氢反应过程,得到低温活性、氢选择性和稳定性较好的催化剂.Cu/Al2O3催化剂中添加CeO2提高了催化剂的活性和稳定性,当CeO2质量分数为20％时,催化剂活性表现最佳.在反应温度250 ℃,水醇摩尔比为1.0,液体空速为3.28 h －1条件下,甲醇转化率为95.5％,氢气选择性为100％.此外,CeO2通过促进水气转化反应降低了重整气中CO的含量.Cu/CeO2/Al2O3催化剂在200 h的寿命实验中,活性仍保持在90.0％以上,而Cu/Al2O3催化剂在100 h的寿命实验中,活性已很快下降.XRD和TPR分析及表面元素分布结果表明,铜和铈相互作用促进了铜在催化剂表面的高度分散,阻止了铜晶粒团聚、烧结,促使铜晶粒细小化,促进了铜的还原,改善了Cu/CeO2/Al2O3催化剂的性能.     

CeO2改性Cu/Al2O3催化剂上甲醇水蒸气重整制氢

研究CeO2改性Cu/Al2O3催化剂上甲醇水蒸气重整制氢反应过程,得到低温活性、氢选择性和稳定性较好的催化剂.Cu/A12O3催化剂中添加CeO2提高了催化剂的活性和稳定性,当CeO2质量分数为20%时,催化剂活性表现最佳.在反应温度250℃,水醇摩尔比为1.0,液体空速为3.28 h-1条件下,甲醇转化率为95.5%,氢气选择性为100%.此外,CeO2通过促进水气转化反应降低了重整气中CO的含量.Cu/CeO2/Al2O3催化剂在200 h的寿命实验中,活性仍保持在90.0%以上,而Cu/Al2O3催化剂在100 h的寿命实验中,活性已很快下降.XRD和TPR分析及表面元素分布结果表明,铜和铈相互作用促进了铜在催化剂表面的高度分散,阻止了铜晶粒团聚、烧结,促使铜晶粒细小化,促进了铜的还原,改善了Cu/CeO2/Al2O3催化剂的性能.     

柠檬酸络合法制备的Co/CeO_2催化剂上中温乙醇水蒸气重整性能(英文)

采用柠檬酸络合法制备了Co/CeO2及其钙掺杂系列催化剂,并对催化剂进行了低温N2物理吸附、X射线衍射、H2程序升温还原、傅里叶变换红外光谱、高分辨透射电镜表征以及乙醇水蒸气重整催化性能测试.结果表明,所制Co/CeO2催化剂具有良好的乙醇水蒸气重整催化性能,500oC时乙醇能全部转化为C1,氢气产率高达85%以上.Ca掺杂减小了载体CeO2纳米颗粒尺寸,但对还原后Co0尺寸的影响较小.当Ca掺杂量大于5.0%时,催化剂氧化还原性能和乙醇水蒸气重整催化性能下降.较高的还原温度有利于体相Ce4+还原为Ce3+,并且提高了催化活性,认为金属-氧化物边界的增加提高了催化活性.初步稳定性考察结果表明,5%钙掺杂后的催化剂具有更好的抗积炭性能.     

柠檬酸络合法制备的Co/CeO2催化剂上中温乙醇水蒸气重整性能（英文）

采用柠檬酸络合法制备了Co/CeO2及其钙掺杂系列催化剂,并对催化剂进行了低温N2物理吸附、X射线衍射、H2程序升温还原、傅里叶变换红外光谱、高分辨透射电镜表征以及乙醇水蒸气重整催化性能测试.结果表明,所制Co/CeO2催化剂具有良好的乙醇水蒸气重整催化性能,500oC时乙醇能全部转化为C1,氢气产率高达85%以上.Ca掺杂减小了载体CeO2纳米颗粒尺寸,但对还原后Co0尺寸的影响较小.当Ca掺杂量大于5.0%时,催化剂氧化还原性能和乙醇水蒸气重整催化性能下降.较高的还原温度有利于体相Ce4+还原为Ce3+,并且提高了催化活性,认为金属-氧化物边界的增加提高了催化活性.初步稳定性考察结果表明,5%钙掺杂后的催化剂具有更好的抗积炭性能.     

焙烧温度对甲醇水蒸气重整制氢Ce/Cu/Zn-Al水滑石衍生催化剂的影响

采用原位合成法在γ-Al_2O_3载体表面上合成了Zn-Al水滑石,再采用顺序浸渍法制备了一系列Ce/Cu/Zn-Al催化剂,并采用XRD、BET、H_2-TPR和XPS等手段对催化剂进行了表征,考察了焙烧温度对Ce/Cu/Zn-Al催化剂表面结构及其催化甲醇水蒸气重整制氢性能的影响。结果表明,焙烧温度主要影响了催化剂的Cu比表面积、表面氧空穴含量和Cu-Ce间相互作用。当焙烧温度为500℃时,催化剂Cu的比表面积较大,表面氧空穴含量较多,Cu-Ce间相互作用较强,因此,催化甲醇水蒸气重整制氢活性较好。当焙烧温度升高到700℃时,Cu物种主要以稳定的CuAl_2O_4尖晶石形式存在,不利于甲醇水蒸气重整制氢反应的进行,因此,催化活性较差。     

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.