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1.
固溶体α-(Fe_(1-x)Sb_x)_2O_3(0≤x≤0.2)气敏材料   总被引:1,自引:2,他引:1  
用化学共沉淀法在a-Fe_2O_3,中掺入锑离子,X-射线衍射(XRD)分析证实,锑离子可固溶于n型半导体a-Fe_2O_3中形成a-(Fe_1-xSb_x)_2O_3(0《x《0.2)固溶体。由于锑离子(Sb ̄5+)部分取代a-Fe_2O_3晶格中Fe ̄3+的格位,使得该系列材料的电导值增大一个数量级以上,气敏性能明显改善。  相似文献   

2.
α-Fe_2O_3/SnO_2气敏薄膜的结构与性质   总被引:1,自引:0,他引:1  
α-Fe_2O_3/SnO_2气敏薄膜的结构与性质娄向东,杨秀清,李靖华,沈荷生,沈瑜生(河南师范大学化学系新乡453002)(中国科学技术大学材料科学与工程系合肥)关键词α-Fe_2O_3,SnO_2,双层膜,气敏性能α-Fe_2O_3具有刚玉结构...  相似文献   

3.
二氧化碳加氢合成甲醇铜基催化剂表面组成的研究   总被引:5,自引:0,他引:5  
本文分别采用XRD、ESR、XPS和XAES等技术对于二氧化碳加氢低压合成甲醇用CuO,CuO-ZnO,CuO-ZnO-Al_2O_3,CuO-ZnO-ZrO_2催化剂在不同条件下表面Cu、Zn、Al、Zr的存在价态进行了深入分析。实验发现催化剂在还原前Cu以Cu ̄2+存在,在还原后和反应状态下以Cu ̄0存在;Zn在还原后和反应状态下有部分被还原为Zn ̄(2-δ)(0<δ<2),Zr和Al仍保持其还原前价态。催化剂的表面化学组成为:Cu ̄0/Zn(2-δ) ̄+/Zr ̄4+/Al ̄3+/O ̄2-。  相似文献   

4.
合成了(CeO_2)_(0.7-x)(MO)_x(La_2O_3)_(0.3)(M=Mg、Ca、Sr)固体电解质。对其晶体结构、电导率、XPS谱、离子迁移数及制成的燃料电池的V-I曲线进行了测定。(CeO_2)_(0.7)(La_2O_3)_(0.3)中掺入Ca ̄(2+)、Mg ̄(2+)或Sr ̄(2+),可使电解质的氧离子导电性能改善,从而使制成的燃料电他的开路电压输出功率也得到提高。  相似文献   

5.
本文用ESR谱和XPS谱对这类催化剂作了表征研究。结果表明,在经Al ̄(3+)掺杂的ZnO-Al_2O_3体系上,观测到g=1.9606±0.0002,△H_(pp)=(2.8±0.1)×10 ̄(-4)T的顺磁信号,该信号强度(以自旋数/克表示)随ZnO中Al_2O_3掺杂量增加而增长;当Al/Zn达2/100(原子比)时,逐渐趋于平稳。相关体系的ESR和XAES比较研究结果排除了该顺磁信号系产生于顺磁氧物种(诸如,O_2-、O-或O_3-)或Zn+的可能性,而有利于关于三价金属离子(AL ̄(3+))掺杂在ZnO晶格中诱导生成正一价缺位的推断。这类Shottky缺位在催化剂表面富集,有利于表面Cu ̄+物种的稳定,从而促进了CO加氢活性的提高。  相似文献   

6.
三环己基锡O,O'-二(4-氯苯基)二硫代磷酸酯(Ⅰ),C_(30)H_(41)Cl_2O_2PS_2Sn,M_r=718.36,单斜晶系,P2_1/n,a=16.151(2),b=9.415(1),c=22.987(3),β=105.69(1)°,Z=4,Dc=1.418g·cm ̄(-3),R=0.063;二丁基锡双[O,O'-二(4-甲基苯基)二硫代磷酸酯](Ⅱ),C_(36)H_(46)O_4P_2S_4Sn,M_r=851.66,单斜晶系,P2_1/c,a=12.284(4),b=9.807(1),c=34.471(8),β=99.02(2)°,Z=4,D_c=1.379g·cm(-3),R=0.042。化合物Ⅰ具有单分子的四配位变形四面体结构。其Sn-S(1)键长为2.501(2);而Sn与S(2)的原子间距则为3.597;化合物Ⅱ具有单分子的六配位变形八面体结构,其Sn-S(1),Sn-S(2),Sn-S(3)和Sn-S(4)的键长分别为2.495(3),2.493(2),3.244(4)和3.228(3)。  相似文献   

7.
以乙烯、乙烷为探针反应分子,以混合不同锌含量的ZnO/SiO_2,与HZSM-5为催化剂,在不同处理条件与不同混合方式(直接混合或机械研磨)下研究高温焙烧的俗化剂对乙烯、乙烷芳构化反应的影响。考察了不同含量的Zn/HZSM-5上C_2H_4、C_2H_6的芳构化反应及NaHZSM-5与ZnO/SiO_2和NaZnHZSM-5与ZnO/SiO_2混合催化剂高温焙烧后的C_2H_4芳构化反应。发现Zn/HZSM-5是一种双功能催化剂,乙烯、乙烷芳构化反应的活性和选择性均与Zn/HZSM-5的双中心Zn ̄(2+)和B酸的相互匹配有密切关系,B酸和Zn ̄(2+)存在最合适匹配。而NZSM-5与ZnO/SiO_2合催化剂高温焙烧后具有Zn/HZSM-5的双功能性,HZSM-5与ZnO/SiO_2在高温下发生了固相反应。  相似文献   

8.
Cu-Zn-Cr/Al_2O_3催化剂的XRD研究解韫青,连业良(青岛建工学院分析检测中心,山东青岛266033)以Al_2O_3为载体的催化剂有广泛的用途,国内外有不少学者进付研究,卞国柱 ̄[1]研究了K-MoO_3/γ-Al_2O_3催化剂的物种...  相似文献   

9.
Zn/HZSM-5分子筛上乙烯、乙烷芳构化的协同作用机理   总被引:2,自引:0,他引:2  
运用NH_3-TPD、IR-OH、Py-IR、CO-IR及XPS等手段对Zn/HZSM-5及其浸碱催化剂的酸组分和金属组分构成的L酸性质进行了表征,考察了催化剂对乙烯、乙烷的芳构化作用.发现Zn/HZSM-5中形成了Zn ̄(2+)-L强酸中心,使分子筛的B酸中心减少.浸碱也可使分子筛的B酸减少,芳构化反应的活性和选择性均与Zn/HZSM-5的双中心Zn ̄(2+)-L酸和B酸的相互匹配密切相关,B酸和L酸存在最适合匹配,因此Zn/HZSM-5在乙烯、乙烷芳构化反应中存在最佳锌含量.  相似文献   

10.
三羰基环戊二烯基钼负离子与1,3-二卤丙烷在一缩二乙二醇二甲醚介质中反应,生成环卡宾配合物CpMoX(CO)_2CO(CH_2)_2CH2(X=Br,I).硅桥连双环戊二烯基三羰基钼负离子与1,3-二卤丙烷顺利地进行类似反应,生成相应的硅桥连双[环卡宾钼配合物]──E[C_5H_4MoX(CO)_2]CO(CH_2)_2CH_2]_2(E=Me_2Si,Me2SiSiMe_2,Me2SiOSiMe_2).化合物硅氧硅桥联二茂二钼环卡宾配合物11的晶体结构经X射线衍射测定,晶体属三斜晶系,P1空间群,晶体学数据:a=0.8188(1)nm,b=1.045(3)nm,c=2.3252(4)nm,α=94.14(2)°,β=94.09(1)°,γ=102.48(2)°,V=1.9306nm ̄3,Z=2,D_c=1.854g/cm ̄3。  相似文献   

11.
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   

12.
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   

13.
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   

14.
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   

15.
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   

16.
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   

17.
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   

18.
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   

19.
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   

20.
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   

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