微波等离子体化学气相沉积法低温合成纳米碳管

纳米碳管的低温合成是纳米碳管合成的一个重要研究方向。在众多的合成方法 中,化学气相沉积法,特别是等离子体化学气相沉积法在纳米碳管的低温合成方面 意义重大。本研究利用溶胶-凝胶法结合等离子体还原,获得了负载在SiO_2上的纳 米金属钻颗粒。以甲烷为碳源、氢气为载气,在纳米金属钴颗粒的催化作用下,利 用微波等离子体化学气相沉积法在低于500 ℃ 的温度条件下合成了纯度较高的纳 米碳管。     

超细4A分子筛的超声波低温快速合成

在低温条件下用超声波快速合成了4A分子筛.产物分别用XRD,IR,SEM和DSC等进行了表征.结果表明,用超声波法合成4A分子筛的速度是常规法的24倍.合成产物的白度为95%,钙离子交换容量为335mgCaCO₃/g4A分子筛,平均粒径为280nm.与采用常规方法合成的产物相比,超声波法合成的产物热稳定性有所下降.     

BaCe0.8Ln0.2O2.9(Ln=Gd, Sm, Eu)固体 电解质的低温制备及其燃料电池性质

利用溶胶-凝胶法低温合成了BaCe     

浆态床反应器中甲醇合成反应的数学模拟

为了对低温液相甲醇合成反应的模试及进一步的工业应用提供一定的预测和参考,用搅拌釜中得出的低温液相甲醇合成反应的动力学方程,经过合理的反应器模型假设,对低温甲醇合成鼓泡浆态床反应器进行了数学模拟,其中的非线性常微分方程组,采用变步长四阶Runge-Kutta法进行数值计算,结果表明,模试操作条件下对CO转化率和H2转化率的模拟计算结果与实际的模模试值的误差分别为13％和4％,模拟结果与模试实验结果比较相符;对不同条件下的反应速率和转化率进行了模拟预测。     

两种有机溶胶法合成铬酸镧超细粉体的对比研究

用两种有机溶胶法——Pechini法和低温燃烧法分别合成了铬酸镧超细粉体。借助红外光谱（ATR）、热分析（TG，DSC）、X射线衍射等手段对制备的凝胶结构、热分解过程、粉体结构和形貌进行对比分析。结果得出，羟基作为最主要的络合基团存在于两种合成方法的凝胶中。虽然两种方法的反应过程相似，但燃烧法只经过一步燃烧就可以迅速合成最终粉体，Pechini法必须经过较长时间煅烧。燃烧法得到的粉体粒径小于Pechini法，分散性也较好。另外，还讨论了两种合成方法反应过程及产物形态差别的原因。     

锐钛矿型纳米氧化钛及其复合材料的低温制备技术

探索低温合成高催化活性纳米TiO2及其复合材料的有效方法,突破传统的高温煅烧法制备锐钛矿相纳米TiO2光催化剂带来的局限,已成为该领域研究的热点问题。本文综述了近年来低温合成锐钛矿型纳米TiO2光催化剂的研究进展,讨论了目前所报道的各种方法（胶溶－相转移法、衍生溶胶－凝胶法、水热法、超声水解法、微波照射法、微乳液法和低温直接氧化法）的原理、操作步骤、反应进程以及优缺点。针对纳米TiO2晶体用作光催化剂时固有的缺陷,即量子效率低且无法利用可见光,进一步评述了离子掺杂、贵金属沉积以及半导体复合等纳米TiO2复合材料的低温制备技术,展望了该领域今后的发展方向和研究重点。     

还原剂对低温燃烧合成Ce_(0.85)Sm_(0.15)O_(1.925)粉体性能的影响

低温燃烧合成法是新兴的制备纳米粉体的工艺,在制备固体氧化物电解质方面有着很好的应用前景。对低温燃烧合成工艺中不同还原剂对粉体性能的影响进行了研究。分别用甘氨酸和尿素作还原剂制备Ce0.85Sm0.15O1.925粉体,以固相法粉体为参照,通过红外光谱、XRD,SEM等检测方法,从粉体的掺杂效果和烧结活性两方面进行比较。结果发现:用甘氨酸作还原剂制备的Ce0.85Sm0.15O1.925粉掺杂效果良好,晶格常数为0.5431 nm;晶粒细小,平均晶粒尺寸为5.8 nm;烧结活性良好,在1200℃即可达到较高致密度,烧结体晶界洁净,晶粒尺寸均匀适中。     

杂原子ZSM－5、ZSM－11和ZSM－48型分子筛的合成

在Na₂O-SiO₂-M_xO_y-H₂O体系中,以HMDA为模板剂用动态法和静态法合成了Ti-ZSM-48型分子筛,首次以85%(wt)HMDA+15%(wt)TPA⁺为模板剂用低温陈化的静态法合成了第四周期过渡金属杂原子M-ZSM-5型分子筛,并与以HMDA、TPA⁺为模板剂合成M-ZSM-5和以TBA⁺为模板剂合成M-ZSM-11进行了对比研究。利用XRD技术跟踪晶体生长过程,考查了模板剂、合成方法、pH值、Na⁺含量等因素对晶化动力学的影响,得出了合成各种杂原子分子筛的最佳条件。各种测试均表明杂原子进入了分子筛骨架。     

K3Sb0.3Y4O8·6H2O新型低温相的水热合成与表征

低温相合成是水热合成化学的重要特征之一［’j，因此，水热合成对低温相功能材料的开发和应用研究有着十分重要的意义．水热晶化法合成的固体电解质材料具有结晶度高、均匀性好等特点，更有利于材料的制备［’－‘j．低温型质子导体在气体传感器和股分离及股反应器方面有着广泛的应用前景，材料体系多含水或羟基化合物．为此，我们以开发新型低温相质子导体为目的，在K。0－Sb。0。－Y。O。－H。O体系中开展了新型低温相的水热合成研究，本文报道了K3Sbo3Y408·6HZO新型低温相的水热合成与表征．1实验方法以分析纯KOH、Y刀。和C。H…     

高活性载体Ziegler-Natta催化剂的研究

<正> 用反应法(MgCl_2/ROH/TiCl_4)合成MgCl_2载体Ziegler-Natta催化剂已被聚烯焊工业越来越广泛的接受。这不仅是因为这种催化剂体系具有高活性,用于α-烯烃聚合能得到高等规度的聚合物;而且比用研磨法制备催化剂易于控制操作条件,合成这种催化剂的关键步骤是醇溶解MgCl_2,再在低温下与TiCl_4反应。放出HCl和形成Ti(OR)Cl_3的同时,MgCl_2再次从溶液中沉淀出来而得到很好的载体。过去,曾从不同     

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%.     

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.     

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.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

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.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

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.