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通过测定加氢反应后反应溶液中金属的溶出量,考察了高分子负载催化剂的稳定性,研究了活性中心金属的种类、价态及分散程度对催化剂稳定性的影响。实验表明,在聚苯乙烯苄基氨茴酸树脂载体上,不同金属物种的催化剂稳定性次序为:Pd混合价态钯>二价钯。随着载体表面钯分散度的增大,钯盐中配体En值的减小,溶剂极性的减弱,钯的流失量也呈下降趋势。 相似文献
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添加硼砂助熔剂煤灰熔融性的量子化学与实验研究 总被引:4,自引:0,他引:4
将硼砂按不同比例分别掺入四种高灰熔点煤灰中,对混合灰样熔融特性进行实验研究。 采用密度泛函理论对熔融过程中作为反应物的莫来石反应活性进行计算。莫来石属于正交晶系Pbam空间群。计算结果表明,莫来石很容易与电子接受体结合,不容易与电子给予体结合。当莫来石与电子给予体结合时,Si原子的活性高于Al。因此,向莫来石中加入助熔剂硼砂时,硼砂中的Na+作为电子接受体,非常容易进入莫来石的晶格中,促使莫来石转变为霞石,降低了灰熔融温度。在还原性气氛下,煤灰熔融特性实验证实了理论计算结果。 相似文献
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0引言氧载体是一类能够可逆吸收分子氧的特殊金属配合物。由于它在贮氧、除氧上有潜在的应用价值及对探索生命科学的重要意义,使得氧载体的研究得以广泛的展开[1~3],目前对氧载体氧合性能的影响因素研究局限于溶剂、温度、配体等因素的研究[4~6],而不同金属盐对氧载体氧合性能影响的探讨很少见于报道。作者在实验中发现,当使用不同阴离子的钴盐进行固相合成氧载体时,所得氧载体吸收分子氧的性能有明显差异。为探讨固相反应中不同钴盐对钴配合物氧合性能的影响,本文以丙二胺为配体,与四种不同钴盐分别发生液鄄固反应和气鄄固反应,再通过氧合… 相似文献
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建立了叶下珠药材中黄酮的毛细管电泳指纹图谱。以硼砂和十二烷基磺酸钠(pH9.0)为背景电解质溶液,运行电压15kV,紫外检测波长245nm,流体静压力进样15s(高度12cm),对不同产地叶下珠药材进样检测。按电泳峰共有率fi≥70%为依据,确定10个不同产地叶下珠药材中黄酮的毛细管电泳指纹峰为8个,各产地叶下珠的毛细管电泳指纹图谱与标准毛细管电泳指纹图谱的相似度较好。在制备供试液后不同时间进样测定,各指纹峰的相对迁移时间的相对标准偏差小于5%,相对峰面积的相对标准偏差在3.0%~7.8%之间,结果表明样品在48h内稳定。 相似文献
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Wenjie SHEN 《物理化学学报》2017,33(7):1267-1268
正金属-载体相互作用是负载型金属催化剂的基本结构特征,也是影响催化性能的关键因素。长期以来,对金属-载体相互作用机制的研究大都集中在氧化还原性氧化物负载的贵金属纳米粒子催化剂体系;但是由于金属粒子尺寸分布的不均匀性和氧化物载体表面的各向异性,很难从原子尺度上形成对催化活性位点和反应机理明确认知,也难以定量描述和理解金属-载体相互作用的化学本质~1。基于单原子催化剂研究金属-载体相互作用能够排除金属颗粒在金属-载体界面上尺寸、形貌和取向的影响,因此,单原子催化剂被 相似文献
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固体炭对一氧化氮低温催化解离还原反应的影响——Ⅰ.复合催化剂还原活性的考察 总被引:1,自引:0,他引:1
考察了担载在活性炭上的以铜、铁为主的复合催化剂对一氧化氮催化解离还原活性的影响,并通过TPR和XRD研究了不同金属组份配比和不同助剂(K、Na)对催化剂性能的影响。结果表明,通过选择不同催化剂配比和添加不同助剂,降低主催化剂在载体炭上的还原温度和提高主催化剂在载体炭上的分散度,将有利于提高催化剂对一氧化氮催化解离还原的活性。文中还采用电镜方法研究了不同组成复合催化剂的金属颗粒大小和Cu、Fe复合催化剂经反应后其表面的形貌结构,发现在这种炭载型复合催化剂上进行一氧化氮催化解离还原反应的过程中,有催化剂表面金属颗粒迁移、生成炭丝和金属颗粒在载体炭上打洞等迹象。 相似文献
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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%. 相似文献
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Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction
Laurent Gavara Thomas Boisse Jean-Pierre Hénichart Adam Daïch Philippe Gautret 《Tetrahedron》2010,66(38):7544-5571
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. 相似文献
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Uroš Grošelj Mojca Žorž Amalija Golobič Branko Stanovnik Jurij Svete 《Tetrahedron》2013,69(52):11092-11108
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. 相似文献
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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. 相似文献
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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. 相似文献
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Rebecca J. Burton Mandy L. CrowtherNeal J. Fazakerley Shaun M. FilleryBarry M. Hayter Jason G. KettleCaroline A. McMillan Paula PerkinsPeter Robins Peter M. SmithEmma J. Williams Gail L. Wrigley 《Tetrahedron letters》2013
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. 相似文献
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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. 相似文献
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N. A. Nedolya 《Chemistry of Heterocyclic Compounds》2008,44(10):1165-1219
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. 相似文献
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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%). 相似文献
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Shashikant U. Dighe Surya K. Samanta Shivalinga Kolle Sanjay Batra 《Tetrahedron》2017,73(17):2455-2467
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. 相似文献