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1.
用X射线光电子能谱(XPS)分析研究了不同氧化层结构的铀金属试样在CO(25℃)和H2(200℃)气氛中的表面反应。CO和H2与铀金属表层反应后,氧化物中氧含量均减少,O/U比值随气体进气量的增加而减少。CO对铀金属表面的还原效果随铀表层氧化程度的提高而增强,并且强于H2。当表层氧化物较少、氧化程度较低时,铀试样在H2气氛中发生氢化反应。  相似文献   

2.
采用成键能判据探讨了CO/H在Ru/SiO2和Pt/SiO2担体金属催化剂上的吸附和反应,从成键能角度说明了CO在催化剂上吸附强弱的原因以及CO氢化活性高低的原因。  相似文献   

3.
本文通过二茂基镧系金属氯化物Cp2LnCl(CP=C5H5;Ln=Dy,Ho,Yb)与等摩尔的NaOAc(Ac=CH3CO)及烷基醇HOR(R=-CH2CH2CH3,-CH2CH=CH2)在四氢呋喃溶剂中混合一步反应,合成了六种新的含三种不同配位基的镧系金属有机化合物。化合物的元素分析结果符合通式CpLn(OR)(OAc),红外光谱显示了η^5-Cp、OR及OAc基团的特征吸收峰,质谱显示了化合物  相似文献   

4.
本文应用“原位”发射红外光谱技术,在280℃,0.5MPa反应条件下,对于Cu/ZnO/Al2O3催化剂 CO+H2CO+H2+CO2反应体系的反应过程进行了动态跟踪结果表明,CO|H2反应体系中,CO插入表面-烷氧基的金属-碳键可能是生成碳二以上醇的反应速控步骤。  相似文献   

5.
本文通过二茂基镧系金属氯化物Cp2LnCl(Cp=C5H5;Ln=Dy,Ho,Yb)与等摩尔的NaOAc(Ac=CH3CO)及烷基醇HOR(R=-CH2CH2CH3,-CH2CH—CH2)在四氢呋喃溶剂中混合一步反应,合成了六种新的含三种不同配位基的镧系金属有机化合物.化合物的元素分析结果符合通式CPLn(OR)(OAc),红外光谱显示了η5-CP、OR及OAc基团的特征吸收峰,质谱显示了化合物的三聚碎片离子峰.基于元素分析、红外光谱及质谱数据,建议化合物可能为三聚体结构,即:[CpLn(OR)(OAc)]3.  相似文献   

6.
本文通过二茂基镧不金属氯化物Cp2LnCl(Cp=C5H5;Ln=Dy,Yb)与烷基醇ROH(R=-CH2CH2CH3,-CH2CH=CH2)在四氢呋喃中反应,合成了四个新的含三种不同配位基的镧系金属有机化合物;元素分析,红外光谱及质谱分析表明这些化合物可能具有三聚体结构,即:[CpLn(OR)Cl]3。  相似文献   

7.
分别以清洁及氧悠Cu(100)表面作为金属态铜和部分氧化态铜的表面模拟,用键级守恒-Mores势法研究了两种表面上CO2加氢制甲醇反应的能量学,计算结果表明,在两种表面上,CO2加氢制甲醇反应的优势反应途径均为“CO2,s→HCOOs→H2COs→CH3Os→CH3OHs”与清洁铜表面上的相应基元步骤相比,在Cu(100)-p(2×2)O表面上甲醇合成反应各基元步骤具有更低的活化能;HCOOs是含  相似文献   

8.
在2.9%(wt)Ni/Al2O3催化剂上用insituFTIR研究了CH4部分氧化制合成气的反应机理。结果表明,催化剂表面的活性碳物种与化学吸附的O原子反应生成CO;CH4/O2(2:l)混合气在催化剂表面吸附的IR谱图表明只有H2O和CO2存在,说明CH4和CO2的重整反应没有发生。因此,我们认为CO和H2是一级产物。  相似文献   

9.
采用半微量相平衡方法研究了三元体系Y(ClO4)3.3H2O-B15C5-CH3OH在25℃的溶解度,测定了各饱和溶液的折光率。该体系在25℃生成三种化学计量的配合物,其组成分别为:4Y(ClO4)3.3B15C5.12H2O.12Ch3OH(I),Y(ClO4)3.2B12C5.3H2O.Ch3OH(Ⅲ),其中配合物(I)和(Ⅱ)是溶解不一致化合物。在甲醇溶剂中,分离制备了配合物(Ⅲ),在69-  相似文献   

10.
王海清 《大学化学》1995,10(2):46-47
用前线轨道理论、催化理论对乙烯催化加氢反应机理进行了分析,可以得出:在此反应中,有下列反应机理存在:在一些教材和文献中,对乙烯催化加氢反应机理一般用下列方法解释[1](如图1):但据催化理论,C2H4、CO、H2三种气体在金属Ni上的化学吸附强度顺序是C2H4>CO>H2[2]。这是由于C2H4与金属Ni形成较强的σ-π反馈键[3](如图2):从CO在J105Ni催化下的加氢反应,可知CO的吸附主要为不可逆吸附(此反应机理为被Ni吸附的CO受到H-H基团的进攻,造成C-O键的断裂,生成CH4+H2O)[4]。由于Ni对C2H4的吸附较CO强,从而推断出Ni对C2H4,的吸附亦是不可逆的。若按上述机理进行反应,则必然导致局部不可逆中毒,使反应难以进行,或进行得相当缓慢。但这样的推论与实验结果不符,相反,在一定条件下,此反应进行得相当迅速。为此,我们断定,必然存在一个能使C2H4解吸的反应步骤,这个反应如图3。因此,我们认为,在乙烯催化加氢反应中,有两种反应机理同时存在,它们是:1.H2被Ni吸附,分裂为氢原子,附着在Ni晶体表面,因自由原子不受对称效应的制约[5],故可与C2H4发生反应。2.C2H4被Ni吸  相似文献   

11.
K3InF6 is synthesized by a sol-gel route starting from indium and potassium acetates dissolved in isopropanol in the stoichiometry 1:3, with trifluoroacetic acid as fluorinating agent. The crystal structures of the organic precursors were solved by X-ray diffraction methods on single crystals. Three organic compounds were isolated and identified: K2InC10O10H6F9, K3InC12O14H4F18 and K3InC12O12F18. The first one, deficient in potassium in comparison with the initial stoichiometry, is unstable. In its crystal structure, acetate as well as trifluoroacetate anions are coordinated to the indium atom. The two other precursors are obtained, respectively, by quick and slow evaporation of the solution. They correspond to the final organic compounds, which give K3InF6 by decomposition at high temperature. The crystal structure of K3InC12O14H4F18 is characterized by complex anions [In(CF3COO)4(OHx)2](5−2x)− and isolated [CF3COOH2−x](x−1)− molecules with x=2 or 1, surrounded by K+ cations. The crystal structure of K3InC12O12F18 is only constituted by complex anions [In(CF3COO)6]3− and K+ cations. For all these compounds, potassium cations ensure only the electroneutrality of the structure. IR spectra of K2InC10O10H6F9 and K3InC12O12F18 were also performed at room temperature on pulverized crystals.  相似文献   

12.
一些具有NASICON型网格结构的固体电解质具有高的电导率和好的稳定性,NASICON的意思是Na Super Ionic Conductor[1]。当NaZr2(PO4)3中P5 被Si4 部分取代时便可以得到具有NASICON结构的Na1 xZr2SixP3-xO12体系,其具有高的钠离子电导率。然而有相同结构的Li1 xZr2SixP3-xO12体系的离子电导率却很低,这是因为Li 半径太小,而NASICON三维网格结构的离子通道太大,两者不匹配而使电导率下降[2]。但当LiZr2(PO4)3中Zr4 被离子半径小些的Ti4 取代,所得LiTi2(PO4)3的通道就与Li 半径相匹配,适合于锂离子的迁移,从而使其电导率…  相似文献   

13.
Magnetic susceptibility of Ca2F2-xMnxO5 members crystallizing in two different structures, one having octahedral (O), tetrahedral (T) and square-pyramidal (SP) coordination of transition metal atoms (OTSP structure) and the other having octahedral and tetrahedral coordination (OT structure), has been investigated. Susceptibility behaviour of the oxides with OTSP structure is different from that of the oxides with OT structure. Ca2Fe1-33Mn0-67O5 with OTSP structure shows an antiferromagnetic ordering while the corresponding oxide with OT structure shows weak ferromagnetism. Contribution No. 398 from the Solid State and Structural Chemistry Unit  相似文献   

14.
The crystal structures of Bi2.5Na0.5Ta2O9 and Bi2.5Nam-1.5NbmO3m+3 (m=3,4) have been investigated by the Rietveld analysis of their neutron powder diffraction patterns (λ=1.470 Å). These compounds belong to the Aurivillius phase family and are built up by (Bi2O2)2+ fluorite layers and (Am-1BmO3m+1)2- (m=2-4) pseudo-perovskite slabs. Bi2.5Na0.5Ta2O9 (m=2) and Bi2.5Na2.5Nb4O15 (m=4) crystallize in the orthorhombic space group A21am, Z=4, with lattice constants of a=5.4763(4), b=5.4478(4), c=24.9710 (15) and a=5.5095(5), b=5.4783(5), c=40.553(3) Å, respectively. Bi2.5Na1.5Nb3O12 (m=3) has been refined in the orthorhombic space group B2cb, Z=4, with the unit-cell parameters a=5.5024(7), b=5.4622(7), and c=32.735(4) Å. In comparison with its isostructural Nb analogue, the structure of Bi2.5Na0.5Ta2O9 is less distorted and bond valence sum calculations indicate that the Ta-O bonds are somewhat stronger than the Nb-O bonds. The cell parameters a and b increase with increasing m for the compounds Bi2.5Nam-1.5NbmO3m+3 (m=2-4), causing a greater strain in the structure. Electron microscopy studies verify that the intergrowth of mixed perovskite layers, caused by stacking faults, also increases with increasing m.  相似文献   

15.
Two new compounds, La3Ru8B6 and Y3Os8B6, were synthesized by arc melting the elements. Their structural characterization was carried out at room temperature on as-cast samples by using X-ray diffractometry. According to X-ray single-crystal diffraction results these borides crystallize in Fmmm space group (no. 69), Z=4, a=5.5607(1) Å, b=9.8035(3) Å, c=17.5524(4) Å, ρ=8.956 Mg/m3, μ=25.23 mm−1 for La3Ru8B6 and a=5.4792(2) Å, b=9.5139(4) Å, c=17.6972(8) Å, ρ=13.343 Mg/m3, μ=128.23 mm−1 for Y3Os8B6. The crystal structure of La3Ru8B6 was confirmed from Rietveld refinement of X-ray powder diffraction data. Both La3Ru8B6 and Y3Os8B6 compounds are isotypic with the Ca3Rh8B6 compound and their structures are built up from CeCo3B2-type and CeAl2Ga2-type structural fragments taken in ratio 2:1. They are the members of structural series R(A)nM3n−1B2n with n=3 (R is the rare earth metal, A the alkaline earth metal, and M the transition metal). Structural and atomic parameters were also obtained for La0.94Ru3B2 compound from Rietveld refinement (CeCo3B2-type structure, P6/mmm space group (no. 191), a=5.5835(9) Å, c=3.0278(6) Å).  相似文献   

16.
The crystal structures of compounds with nominal compositions Bi6FeP2O15+x (I), Bi6NiP2O15+x (II) and Bi6ZnP2O15+x (III) were determined from single-crystal X-ray diffraction data. They are monoclinic, space group I2, Z=2. The lattice parameters for (I) are a=11.2644(7), b=5.4380(3), c=11.1440(5) Å, β=96.154(4)°; for (II) a=11.259(7), b=5.461(4), c=11.109(7) Å, β=96.65(1)°; for (III) a=19.7271(5), b=5.4376(2), c=16.9730(6) Å, β=131.932(1)°. Least squares refinements on F2 converged for (I) to R1=0.0554, wR2=0.1408; for (II) R1=0.0647, wR2=0.1697; for (III) R1=0.0385, wR2=0.1023. The crystals are complexly twinned by 2-fold rotation about , by inversion and by mirror reflection. The structures consist of edge-sharing articulations of OBi4 tetrahedra forming layers in the a-c plane that then continue by edge-sharing parallel to the b-axis. The three-dimensional networks are bridged by Fe and Ni octahedra in (I) and (II) and by Zn trigonal bipyramids in (III) as well as by oxygen atoms of the PO4 moieties. Bi also randomly occupies the octahedral sites. Oxygen vacancies exist in the structures of the three compounds due to required charge balances and they occur in the octahedral coordination polyhedron of the transition metal. In compound (III), no positional disorder in atomic sites is present. The Bi-O coordination polyhedra are trigonal prisms with one, two or three faces capped. Magnetic susceptibility data for compound (I) were obtained between 4.2 and 350 K. Between 4.2 and 250 K it is paramagnetic, μeff=6.1 μB; a magnetic transition occurs above 250 K.  相似文献   

17.
采用水热、化学沉积和原位光还原的方法成功制备了新型Ag/Ag2MoO4/Bi2MoO6三元复合光催化剂。通过X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)和紫外可见漫反射光谱(UV-Vis DRS)等技术对材料的组成、形貌、光吸收特性和光电化学性能等进行系统分析。以四环素为目标污染物,研究Ag/Ag2MoO4/Bi2MoO6在可见光下的光催化性能。研究结果表明,相比于纯Ag2MoO4和Bi2MoO6,Ag的表面等离子体共振(SPR)效应显著拓宽了催化体系对可见光的吸收能力及响应范围。当Ag2MoO4理论负载量(质量分数)为24.6%时,Ag/Ag2MoO4/Bi2MoO6复合材料在20 min内可将四环素完全降解,且5次循环使用后仍保持较高的催化活性,表现出良好的循环稳定性。  相似文献   

18.
采用水热合成法制备了Co3O4及复合Ag/Co3O4、CuO/Co3O4一维纳米产品。用XRD,FE-SEM和TEM手段对产品进行了表征。采用循环伏安法研究了合成产品修饰的玻碳电极在碱性溶液中对对硝基苯酚的电催化还原性能。与裸玻碳电极相比,1mmol·L-1的对硝基苯酚在用Co3O4、特别是CuO/Co3O4修饰的玻碳电极上还原的峰电流明显增大,用Ag/Co3O4(Ag/Co原子比分别为1∶5和2∶5)修饰的玻碳电极催化还原对硝基苯酚时,尽管还原峰电流增大不是太大,但其峰电位明显降低(分别降低0.265和0.371V)。  相似文献   

19.
采用水热、化学沉积和原位光还原的方法成功制备了新型Ag/Ag2MoO4/Bi2MoO6三元复合光催化剂。通过X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、X射线光电子能谱(XPS)和紫外可见漫反射光谱(UV-Vis DRS)等技术对材料的组成、形貌、光吸收特性和光电化学性能等进行系统分析。以四环素为目标污染物,研究Ag/Ag2MoO4/Bi2MoO6在可见光下的光催化性能。研究结果表明,相比于纯Ag2MoO4和Bi2MoO6,Ag的表面等离子体共振(SPR)效应显著拓宽了催化体系对可见光的吸收能力及响应范围。当Ag2MoO4理论负载量(质量分数)为24.6%时,Ag/Ag2MoO4/Bi2MoO6复合材料在20 min内可将四环素完全降解,且5次循环使用后仍保持较高的催化活性,表现出良好的循环稳定性。  相似文献   

20.
A new oxide, Bi14Sr21Fe12O61, with a layered structure derived from the 2212 modulated type structure Bi2Sr3Fe2O9, was isolated. It crystallizes in the I2 space group, with the following parameters: a=16.58(3) Å, b=5.496(1) Å, c=35.27(2) Å and β=90.62°. The single crystal X-ray structure determination, coupled with electron microscopy, shows that this ferrite is the m=5 member of the [Bi2Sr3Fe2O9]m[Bi4Sr6Fe2O16] collapsed family. This new collapsed structure can be described as slices of 2212 structure of five bismuth polyhedra thick along , shifted with respect to each other and interconnected by means of [Bi4Sr6Fe2O16] slices. The latter are the place of numerous defects like iron or strontium for bismuth substitution; they can be correlated to intergrowth defects with other members of the family.  相似文献   

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