Study on structure and oxide ionic conductivity for new compound Ce(6-x)Ln(x)MoO(15-delta)

A new compound Ce(6-x)Ln(x)MoO(15-delta) has been synthesized by wet-chemistry method. Their crystal structure and oxide ionic conductivity were characterized by powder X-ray diffraction, Raman, IR spectrum and A.C. impedance technique. The XRD results showed that Ce6MO15-delta, Ce(5)LnMoO(15-delta) have cubic symmetry with Fm3m space group. The refined lattice parameters showed that their lattice constants decrease with the decrease of the ionic radius of Ln(3+). The electrochemical measurements showed that the ionic conductivity of resulting oxides Ce(6-x)Ln(x)MoO(15-delta) have an enhance, which may be a kind of promising material for SOFCs.

高灵敏显色反应的研究

本论文“高灵敏显色反应的研究”包括五部分：（一）文献综述，对分光光度法测定钨、钼方面的文献作了较为全面的评述，并同其它仪器方法进行了比较。（二）钨的高灵敏显色反应的研究和（三）、钼的高灵敏显色反应的研究：提出了灵敏，简便，快速，稳定的测定钨和钼的方法。在动物胶存在下，在盐酸介质中以氯化亚锡作还原剂，使硫氰酸钨（V）或钼（V）与罗丹明B形成离子缔合物，在水相中直接比色测定钨或钼。本法测钨的表现摩尔吸光系数达9.2*10~5升·摩尔~(-1)·厘米~(1)。0.3-2.0微克钨／50毫升符合部伯－比耳定律。测钼的表现摩尔吸光系数达7.5*10~5升·摩尔~(-1)·厘米~(1)，0.2-2.0微克钼／50毫升符合部伯－比耳定律。本法是目前分光光度法测钨和钼的高灵敏方法之一，用于测定天然水中的痕量钨和钼以及高温合金钢中的钨，获得满意结果。（四）罗丹明B聚合状态及解聚的研究。研究了罗丹明B在不同介质中的聚合状态及解聚效应。结果表明，在电解质溶液中，会促使染料发生聚合；在有机溶剂和一表面活性剂中会促使染料解聚。同时，对染料的聚合及解聚的作用机理进行了初探。（五）离子缔合物增敏剂的研究－动物胶对Mo(V)-SCN~--RhB(I)三元络合物的增敏作用。以Mo(V)-SCN~--RhB(I)三元络合物为例研究了表面活性剂对体系的作用；用平衡移动法初步确定了络合物的组成（Mo:SCN~-:RhB)比为1:10:7；证实了罗丹明B－硫氰酸盐缔合物对形成硫氰酸铜（V）－罗丹明B缔合物的作用。间接证明了这种高配位缔合物是在形成[MoO(SCN)_5]·[RhB]_2缔合物分子时，又吸附了一定量的[RhB]·[SCN]缔合物分子形成的。并讨论了动物胶的增敏作用。另外，通过对碱性染料－金属硫氰酸离子缔合物体系在水相中稳定性的比较，认为这类体系的稳定性主要是由其本身的结构特性所决定的，而表面活性剂只起延长体系稳定时间的作用。

Post-steam-treatment of Mo/HZSM-5 catalysts: An alternative and effective approach for enhancing their catalytic performances of methane dehydroaromatization

Post-steam-treatment is a facile and effective method for improving the catalytic performances of Mo/HZSM-5 catalysts in methane dehydroaromatization under nonoxidative conditions. The treatment can enhance the stability of the catalyst and also give a higher methane conversion and a higher yield of light aromatics, as well as a decrease in the formation rate of carbonaceous deposits. (27)Al, (29)Si, and (1)H multinuclear magic angle spinning nuclear magnetic resonance, X-ray photoelectron spectroscopy, X-ray diffraction, X-ray fluorescence spectroscopy, and thermogravimetric analysis measurements as well as catalytic reaction evaluations were employed to conduct comparative studies on the properties of the catalysts before and after the post-steam-treatment. The results revealed that the number of free Bronsted acid sites per unit cell decreased, while more Mo species migrated into the HZSM-5 channels for the 6Mo/HZSM-5 catalysts after the post-steam-treatment. In addition, the average pore diameter was also larger for the post-steam-treated catalysts, and this was advantageous for mass transport of the reaction products. However, a severe post-steam-treatment, i.e., with longer treating time, of the 6Mo/HZSM-5 catalyst will lead to the formation of the Al(2)(MoO(4))(3) phases, which is detrimental to the reaction.

Microcalorimetric and IR spectroscopic studies of CO adsorption on molybdenum nitride catalysts

The adsorption of CO on both nitrided and reduced passivated Mo(2)N catalysts in either alumina supported or unsupported forms was studied by adsorption microcalorimetry and infrared (IR) spectroscopy. The CO is adsorbed on nitrided Mo(2)N catalysts on three different surface sites: 4-fold vacancies, Mo(delta+) ( 0 < delta < 2) and N sites, with differential heats of CO adsorption decreasing in the same order. The presence of the alumina-support affects the energetic distribution of the adsorption sites on the nitrided Mo(2)N, i.e. weakens the CO adsorption strength on the different sites and changes the fraction of sites adsorbing CO in a specific form, revealing that the alumina supported Mo(2)N phase shows lower electron density than pure Mo(2)N. On reduced passivated Mo(2)N catalysts the CO was found to adsorb mainly on Mo(4+) sites, although some slightly different surface Mo(delta+) d (0 < delta < 2) sites are also detected. The nature, density and distribution of surface sites of reduced passivated Mo(2)N/gAl(2)O(3) were similar to those on reduced MoO(3)/gamma-Al(2)O(3).

Simultaneous hydrodesulfurization of thiophene and hydrogenation of cyclohexene over dimolybdenum nitride catalysts

A series of unsupported dimolybdenum nitride (gamma-Mo(2)N) catalysts differing in surface area were prepared by temperature programmed reduction of MoO(3) with a mixture of NH(3):N(2) (90:10). Characterization of catalysts by BET, XRD, TPR and XPS techniques was carried out. The samples were used as catalysts in hydrotreating reactions (simultaneous hydrodesulfurization of thiophene and hydrogenation of cyclohexene). Low surface area gamma-Mo(2)N materials show much higher specific conversions than those with higher surface area. These results indicate that HDS and HYD reactions over gamma-Mo(2)N seem to be structure-sensitive. The relative exposure extent of crystalline planes (111) and (200) over the different catalysts can be associated with their hydrogen adsorption capacities and with their catalytic performances. The catalytic activities are significantly affected by the catalyst pretreatment conditions. (C) 1999 Elsevier Science B.V. All rights reserved.