THE CLEAVAGE REACTION OF THE MO-MO TRIPLE BOND - THE CRYSTAL-STRUCTURES OF MOLYBDENUM COMPLEXES [CPMO(CO)(2)(C(5)H(4)NS)], [CPMO(CO)(2)(C(9)H(6)NS)]O=PPH(3) AND [CPMO(CO)(2)(S(2)CNME(2)]

The reactions of [Cp2Mo2(CO)4] (1) with 2,2'-dipyridyl disulphide (C5H4NS-)2, 8,8'-diquinolyl disulphide (C9H6NS-)2 and tetramethyl thiuram disulphide (Me2NC(S)S-)2 in toluene solution resulted in the cleavage of the Mo-Mo triple bond to yield molybdenum complexes [CpMo(CO)2(C5H4NS)] (2), [CpMo(CO)2(C9H6NS)] (3) and [CpMo(CO)2(S2CNMe2)] (4), respectively. The molecular structures of 2, 3 . O=PPh3 and 4 were determined by X-ray diffraction studies. Crystals of 2 are monoclinic, space group P2(1)/n, with Z = 4, in a unit cell of dimensions a = 6.448(1), b = 12.616(2), c = 14.772(2) angstrom, beta = 92.85(1)-degrees. The structure was refined to R = 0.028 and R(w) = 0.039 for 1357 observed reflections. Crystals of 3 . O=PPh3 are triclinic, space group P1BAR, with Z = 2, in a unit cell of dimensions a = 11.351(3), b = 13.409(3), c = 9.895(2) angstrom, alpha = 94.59(2), beta = 90.35(2), gamma = 78.07(2)-degrees. The structure was refined to R = 0.033 and R(w) = 0.037 for 3260 observed reflections. Crystals of 4 are monoclinic, space group P2(1)/a and Z = 4 with a = 12.468(5), b = 7.637(2), c = 13.135(4) angstrom, beta = 96.62(3). The structure was refined to R = 0.032 and R(w) = 0.042 for 1698 observed reflections. Each of complexes 2-4 contains a cyclopentadienyl ligand, a cis pair of carbonyls and a chelate ligand (S,N donor or S,S donor). All the compounds have distorted square-pyramid structures.

STUDIES ON DEFECT STRUCTURE AND CATALYTIC PROPERTIES OF SN-MO OXIDES

The present work is devoted to the studies on relationship of structure and activity of Sn-Mo oxides by using XRD, ESR, IR, XPS, TEM and SEM. Eight samples with Mo/(Mo + Sn) rations: 0.0, 0.1, 0.2, 0.4, 0.6, 0.8, 0.9, 1.0 were prepared. On the basis of structure characterization, Sn-Mo oxides can be divided into three groups: Catalysts I with Mo/(Mo + So) less-than-or-equal-to 0.2, Catalysts II with 0.2 < Mo/(Mo + Sn) < 0.8, and catalysts III with Mo/(Mo + Sn) greater-than-or-equal-to 0.8. The solid solution of Mo5+ in tin oxide was formed and the cation vacancy was formed in catalysts I. The solid solution of Sn4+ in molybdenum oxide was formed in catalysts III. The lattice oxygen in catalysts III has higher mobility and reactivity than that in catalysts I. The catalysts III showed higher activity but lower selectivity than that of catalysts I.

用ESR方法研究Sn-Mo���化物固溶体形成的机理

本文研究了Sn-Mo���合氧化物催化剂的活性与焙烧温度的关系。对Sn_(0.975)Mo_(0.025)催化剂进行了不同焙烧温度的ESR研究,跟踪观察了Sn-Mo���合氧化物固溶体随焙烧温度变化的形成过程。结果表明,焙烧温度在100—300℃之间,钼以钼酸铵微晶高度分散在氧化锡表面;300—550℃时,随温度升高钼逐渐向氧化锡体相扩散;550℃时可能形成嵌入型固溶体,催化活性最好;600℃开始形成置换型固溶体,Mo���Mo~(5+)形式取代氧化锡晶格中的Sn~(4+),此时ESR信号gzz>gxx>gyy。

水煤气变换催化剂Co-Mo-K/Al_2O_3的酸性对活性的影响

用吡啶吸附法研究了Co-Mo-K/Al_2O_3催化剂的酸性,K的加入,由于改变了催化剂的酸性,使其活性得以提高,硫的丢失也可改变酸性,但使催化剂的活性降低。初步探讨了催化剂酸性对活性影响的实质,提出了新的反应机理。

K助化Co-Mo/Al_2O_3催化剂的表征

以XRD,XPS和TPR研究了一系列K助化的Co-Mo/Al_2O_3催化剂,考察了K对Co和Mo���载体上分散的影响。实验表明,K的加入分解了原来存在於催化剂中的CoMoO_4,促进了Mo���硫化还原,是提高水煤气变换反应的一个因素。

Sb-Mo���合氧化物单一相催化剂上的醇类氧化酯化

制备了三种单一相Sb-Mo-O系复合氧化物催化剂并用于C_1—C_4的醇类氧化反应,在反应条件下均可保持其晶体结构与酯化活性的稳定性。对氧化酯化来说,唯有以乙醇为原料时才可以高收率地获得酯类,其活性顺序为Y相>X相>Z相。异丙醇和异丁醇在同一催化剂上的反应结果,因反应温度高低而异,低温时发生脱氢反应,高温时发生脱水反应。利用体相晶格氧,乙醇氧化生成乙醛;而进一步氧化酯化生成乙酸乙酯则是利用气相氧。

Sn-Mo���合氧化物的缺陷结构及催化性能的研究

本文以1-丁烯在水蒸汽存在下选择性氧化制甲乙酮为典型反应,利用 XRD,ESR,IR,XPS,TEM 和 SEM 研究了 Sn-Mo 氧化物的结构与活性的关系.制备了8个样品,A,B,C,D,E,F,G 和 H 的 Mo/(Mo+Sn)分别为0,0.1,0.2,0.4,0.6,0.8,0.9,1.0.根据结构特征,可将 Sn-Mo 氧化物分为三组:第Ⅰ组 Mo/(Mo+Sn)≤0.2;第Ⅱ组0.2

Co,Mo���Al_2O_3和K在Co-Mo���化剂上的吸附和分布

钴离子在γ-Al_2O_3上的吸附速度比钼酸根离子的慢,但钴离子的视扩散系数比钼酸根的大(25℃下D_(Co)=1.2×10~(-5)cm~2/s,D_(Mo)=4.4×10~(-6)cm~2/s)。钴的吸附等温线符合Langmuir等温式,而钼的符合Freundlich等温式。在等孔容积共浸法制备催化剂时,低pH值下由于Al_2O_3吸附Mo���多而导致Co、Mo���颗粒中分布不均;在高pH值下由于Mo���吸附量锐减,可用共浸法得到分布均匀的催化剂。K_2CO_3在均匀型Co-Mo/Al_2O_3催化剂上的吸附等温线符合Langmuir等温式,虽然吸附量较大,但在浸渍液中含量足够时也可得到均匀分布的结果。

Co-Mo-K/Al_2O_3水煤气变换催化剂的失硫与活性

Co-Mo 系催化剂由于其优越的耐硫性能和对水煤气变换反应的高活性,因此在制氢工业中日益得到重视。已知 Co-Mo-K/Al_2O_3催化剂是一种优良的水煤气变换催化剂,该催化剂在使用前须经硫化。实际上催化剂在反应时

乙醇氧化酯化反应中Sb-Mo���元氧化物催化剂的复合效果

从活性试验、比表面测定、结构分析、还原度测定及程序升温还原等多方面考察了 Sb—Mo���元氧化物体系与单独氧化物 MoO_3、Sb_2O_4的特性,认为与单独氧化物相比,在标题反应中 Sb-Mo���元氧化物的高活性与其比表面的增大有关,乙酸乙酯选择性的提高是由于在反应气氛下催化剂内生成了新的活性相。显示出较高氧化酯化选择性的工作状态,催化剂处于某种程度被还原的状态。这种状态下的催化剂体相氧比较活泼。

MEASUREMENT OF SPONTANEOUS EMISSION BRANCHING RATIOS IN MO(I) TRANSITIONS BY LASER-INDUCED SENSITIZED FLUORESCENCE

I. TNTRODUCTIONThe emission spectroscopic method is usually used to measure spontaneous emission branching ratios. As emission spectra cannot be detected in atomic beams, the laser-induced fluorescence or ion detection method is often used. When the fluorescence method is used to measure branching ratios, it is usually necessary to detect

甲醇氨氧化合成氢氰酸Fe-Mo���化物催化剂的研究

利用固定床反应器,研究了 Fe-Mo 氧化物/载体催化剂对甲醇氨氧化制氢氰酸的催化性能,考察了催化剂组成和反应条件(如温度)对催化活性的影响。氢氰酸的单程收率可达94%。发现催化剂的活性与表面酸性有关。活性相的结构为 Fe_2(MoO_4)_3。

Extraction behavior of Mo and W as homologs of Sg with α-benzoinoxime

Solvent extraction of molybdenum and tungsten as homologues of Sg with a-benzoinoxime from HCl solutions has been investigated. The extraction equilibration was achieved at 20s for Mo and W. Molybdenum was almost quantitatively extracted from 0.001 to 4M HCl solutions, and the extraction yields decreased at higher and lower acid concentrations due to the formation of anionic oxychloride complex and anionic species MO42-, respectively. The extraction yield of W was lower than that of Mo during the whole range of acid concentration. The composition of the extracted species was determined by using the slope method in present experiment. The elemental analysis, IR and 1H NMR spectra of the extracted species suggest that the extracted complex contain one MoO22+or WO22+ groups bonded with two a-benzoinoxime molecules.

Geomorphic and hydrodynamic responses in salt marsh-tidal creek systems, Jiangsu, China

Salt marsh-tidal creek systems as a coastal geomorphological unit represent an important natural resource. The present study on Jiangsu salt marshes, eastern China, shows that variations in tidal current velocities in salt marsh creeks are controlled by the local tidal wave characteristics and the bed slope and elevation of the salt marshes and creeks. Likewise, the tidal currents modify the geomorphology of the salt marsh-tidal creek systems by transporting sediments and causing erosion/deposition. Storm events, which appear to have cyclical changes in their intensity relating to sunspot activities, can affect the geomorphic evolution of such systems. Further, in response to accelerated sea-level rise, accretional rates on salt marshes may increase. The tidal creeks have the function of transporting water and sediment onto the salt marsh surface; further, the energy of tidal currents and waves are dissipated within the salt marsh-tidal creek system. Hence, this coastal system has a potential value for coastal protection.

地质样品中Mo���位素测定的前处理方法研究

通过对地质样品中Mo���位素测试前的处理方法的比较，对传统的阴、阳离子树脂交换法进行了改进研究。经改进后的方法实用范围较宽，Mo���回收率达到97．49％±0．27％，Mo���位素质谱分析过程中可能的同重干扰元素Zr、Fe、Mn等的去除效果理想，其它金属元素的去除效果也较理想，且在阴离子交换柱洗脱Mo���过程中总计约需的提取液（盐酸和硝酸）体积只有75mL，只需文献报道用量的45％，从而减少了试剂对样品，特别是对低含量地质样品可能带来的潜在污染.