La_2O_3对CuO/CeO_2水煤气变换反应催化剂微观结构及催化性能的影响(英文)

以La2O3为助剂,采用共沉淀法制备了具有良好催化活性和热稳定性的CuO/CeO2-La2O3水煤气变换反应催化剂,其中,当La2O3含量为2wt%时,催化剂的催化性能最为优异.同时运用X射线衍射、N2吸附-脱附、Raman光谱、程序升温还原等手段,研究了不同含量的La2O3对CuO/CeO2催化剂微观结构及催化性能的影响.结果表明,La2O3助剂进入了载体CeO2的晶格并对CuO/CeO2催化剂的微观结构和催化性能产生了直接影响,适量La2O3的添加可以抑制CuO和CeO2晶格的长大、增强CuO与CeO2间的相互作用、提高催化剂的比表面积、促进CeO2载体中生成更多的氧空位,CuO/CeO2催化剂的催化活性和热稳定性也明显改善.     

稀土尾矿基整体催化剂的制备及其低浓度甲烷催化燃烧性能

以稀土尾矿泡沫陶瓷(Tailings foam ceramics,简称TFC)为载体,采用拟薄水铝石制备铝溶胶,经过泡沫陶瓷载体表面涂覆铝溶胶和Cu溶液浸渍得到CuO/γ-Al₂O₃/TFC整体式催化剂,并利用SEM,XRD,XPS,H₂-TPR等技术对催化剂进行表征,评价其甲烷催化燃烧反应性能。结果表明,与原泡沫陶瓷相比,负载CuO的样品催化活性明显增强;随着CuO的负载量增加,催化性能呈现先升高后降低的趋势,CuO的负载量达到4%时催化活性最佳,甲烷转化率为10%和90%时的反应温度分别为301和581℃。CuO的负载量达到6%时,催化剂的活性中心由分散态CuO转变为晶相CuO,导致CuO在载体表面分散度降低并且利用率下降,催化活性降低。负载到泡沫陶瓷载体上的CuO形貌呈球形,整体催化剂活性组分中所有催化剂铈以Ce³⁺,Ce⁴⁺形态共存,铜以Cu²⁺和Cu~+形态共存,各金属元素间变价表明催化剂有较高的氧化还原能力,催化剂表面发生反应：Cu^2...     

La2O3对CuO/CeO2水煤气变换反应催化剂微观结构及催化性能的影响（英文）

以La2O3为助剂,采用共沉淀法制备了具有良好催化活性和热稳定性的CuO/CeO2-La2O3水煤气变换反应催化剂,其中,当La2O3含量为2wt%时,催化剂的催化性能最为优异.同时运用X射线衍射、N2吸附-脱附、Raman光谱、程序升温还原等手段,研究了不同含量的La2O3对CuO/CeO2催化剂微观结构及催化性能的影响.结果表明,La2O3助剂进入了载体CeO2的晶格并对CuO/CeO2催化剂的微观结构和催化性能产生了直接影响,适量La2O3的添加可以抑制CuO和CeO2晶格的长大、增强CuO与CeO2间的相互作用、提高催化剂的比表面积、促进CeO2载体中生成更多的氧空位,CuO/CeO2催化剂的催化活性和热稳定性也明显改善.     

Co掺杂CeO2-ZrO2固溶体催化剂甲烷催化燃烧性能的研究

制备了一系列Co掺杂的CeO2-ZrO2固溶体催化剂,考察了其用于甲烷催化燃烧的反应性能.同时,对反应气体总空速、制备方法和焙烧温度等条件对催化剂反应性能的影响进行了研究.并对其进行了BET比表面、XRD等表征分析.结果表明:Ce-Zr-Co-O系列催化剂对于甲烷催化燃烧反应具有良好的活性和稳定性,Co的加入能显著提升...     

镧系六铝酸盐催化剂制备及甲烷燃烧催化性能表征

采用可控共沉淀法以NH4HCO3和NH4OH组成的缓冲溶液作为沉淀剂制备六铝酸盐,采用BET,XRD,TPR等技术考察了催化剂的物化性能.以甲烷催化燃烧为探针反应,对催化剂进行了催化性能表征,并研究了铈取代对催化性能的影响.结果表明： 采用NH4HCO3和NH4OH缓冲溶液作为沉淀剂使沉淀更均匀,可合成化学均一的六铝酸盐.La系六铝酸盐可在较低焙烧温度1050 ℃形成,稀土离子Ce主要是以高储放氧能力的CeO2相存在,与Mn之间存在协同作用提高了催化活性.当Mn取代度为2时,LaMnxAl12-xO19催化性能最佳,此时具有较高的氧化还原性能.Mn容易进入六铝酸盐晶格,Mn取代的La系六铝酸盐催化剂是很有前途的高温甲烷燃烧催化材料.     

焙烧温度对 Pd/Al2O3 催化剂上甲烷燃烧反应性能的影响

 考察了载体与催化剂焙烧温度对 Pd/Al2O3 催化剂上低浓度甲烷催化燃烧反应性能的影响. 采用 X 射线衍射、透射电镜、N2 物理吸附、NH3 程序升温脱附和 O2 程序升温氧化等手段对载体和催化剂进行了表征. 结果表明, 焙烧温度对催化剂活性及稳定性的影响显著. 随着载体焙烧温度的升高, Al2O3 的比表面积、物相结构、酸中心的数量及强度明显改变, 相应的 Pd/Al2O3 催化剂中载体与 Pd 的相互作用减弱, Pd 分散度降低. 当载体焙烧温度为 1 100 °C, Pd/Al2O3 焙烧温度为 200 °C 时, 所得催化剂在 260 h 的连续反应中, 甲烷转化率始终维持在 99%以上.     

稀土A-Ce-O催化剂的合成及性能研究

采用改进的溶胶-凝胶法合成出了几种含铈稀土复合氧化物催化剂,运用XRD,IR等不同测试手段对复合氧化物催化剂进行了表征,测试了甲烷催化燃烧活性.XRD分析结果表明:经1200 ℃焙烧3 h后4种催化剂中Ba-Ce-O,Sr-Ce-O主要以单一相钙钛矿结构BaCeO3和SrCeO3的形式存在,La-Ce-O体系催化剂呈现面心立方晶体结构特征衍射峰,与立方结构CeO2的衍射峰相似,只是峰的位置偏向低角度;Mg-Ce-O主要以简单氧化物CeO2的相存在,在甲烷催化燃烧反应中La-Ce-O显示出了良好的催化活性,T10为510 ℃,T90为670 ℃;主相为SrCeO3的Sr-Ce-O体系催化剂的甲烷催化活性最差,T10为570 ℃,T90为743 ℃.     

不同CuO/CeO2催化剂上CO低温氧化反应

 分别用热解硝酸铈法和浸渍法制备了不同物性的CeO2粉体和相应的CuO/CeO2催化剂,并用XRD, HRTEM和TPR等对样品进行了表征,利用微反-色谱装置考察了其催化CO低温氧化的活性. 结果表明,热解温度影响CeO2的物性(形貌、粒度大小及分布等). 相同条件下,不同物性的CeO2载体上CuO的负载情况不同, 500 ℃热解获得的CeO2载体上非晶态CuO负载量最高,相应的CuO/CeO2催化剂活性也较高. 非晶态CuO一部分进入CeO2晶格,另一部分高度分散于CeO2表面上. 焙烧温度较低时(≤ 600 ℃), 催化剂活性受焙烧温度的影响较小,而高温(800 ℃)焙烧后,催化剂则因载体粒度增大和CuO烧结团聚等因素导致催化活性明显降低.     

制备方法对CuO-CeO2/ZrO2催化CO氧化性能的影响

以ZrO2为载体、采用不同的浸渍次序制备了3种CuO-CeO2/ZrO2催化剂并在不同的温度(500,650和800℃)下进行焙烧,利用X射线衍射(XRD)、程序升温还原(H2-TPR和CO-TPR)及CO程序升温脱附(CO-TPD)技术对所制备的催化剂进行了表征,并采用色谱流动法考察了其催化CO低温氧化反应性能。结果表明,当焙烧温度为650℃时,3种催化剂的CO催化氧化活性均最佳,且三者的催化活性大小顺序为:CuO/CeO2/ZrO2>CuO-CeO2/ZrO2>CeO2/CuO/ZrO2。结合催化剂的表征和活性测试结果,我们认为高分散的CuO是CO的吸附中心,有利于CO的低温氧化反应,而大颗粒的CuO几乎对CO没有吸附作用,不利于CO的低温氧化反应。在3种催化剂中,CuO/CeO2/ZrO2催化剂具有最佳的低温还原特性和最大的CO2脱附峰面积,相应地具有最佳的催化氧化活性。     

焙烧温度对LaSrFeMo0.9Co0.1O6催化剂催化甲烷燃烧性能的影响

采用溶胶凝胶法制备LaSrFeMo0.9Co0.1O6,以催化甲烷燃烧为目标反应,研究不同焙烧温度(600、700、800、900℃)对其催化甲烷燃烧性能的影响.通过XRD、BET、H2-TPR及SEM技术对其结构进行表征.结果表明,在不同的焙烧温度下均可形成完整的双钙钛矿晶型,且焙烧温度不同其催化活性不同,随着焙烧温度的升高其催化活性先升高后逐渐降低.当焙烧温度为800℃,样品比表面积为14 m2/g,起燃温度T10％为428℃,T90％为640℃.     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

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.     

Microwave-assisted copper-catalyzed stereoselective ring expansion of three-membered heterocycles with α-diazo-β-dicarbonyl compounds

Microwave-assisted copper-catalyzed ring expansions of three-membered heterocycles with α-diazo-β-dicarbonyl compounds were investigated. Thiiranes generated 3-acyl-5,6-dihydro-1,4-oxathiines in the presence of copper sulfate and trans-3-acyl-5,6-dihydro-1,4-oxathiines as stereospecific products for 1,2-disubstituted cis-thiiranes through an intramolecular S_N2 process. Oxiranes gave rise to 2-acyl-5,6-dihydro-1,4-dioxines under the catalysis of copper hexafluoroacetylacetonate and cis-3-acyl-5,6-dihydro-1,4-dioxines as stereospecific products for 1,2-disubstituted cis-oxiranes via an intimate ion-pair mechanism. The current method provides a direct and simple strategy in efficient preparation of 3-acyl-5,6-dihydro-1,4-oxathiines and 2-acyl-5,6-dihydro-1,4-dioxines, important agents in medicinal and agricultural chemistry, from readily available thiiranes and oxiranes, respectively.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.