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首页> 外文学位 >CHARACTERIZATION OF MOLYBDENUM BASED SYSTEMS IN SOLUTION AND ON SUPPORTS BY SPECTROSCOPIC METHODS AND ACTIVITY STUDIES (TITANIA, HYDRO-DESULFURIZATION, MOLYBDENUM-OXALATE, FISCHER-TROPSCH REACTION, RAMAN SPECTROSCOPY).
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CHARACTERIZATION OF MOLYBDENUM BASED SYSTEMS IN SOLUTION AND ON SUPPORTS BY SPECTROSCOPIC METHODS AND ACTIVITY STUDIES (TITANIA, HYDRO-DESULFURIZATION, MOLYBDENUM-OXALATE, FISCHER-TROPSCH REACTION, RAMAN SPECTROSCOPY).

机译：基于钼的体系的溶液表征和光谱学方法和活性研究（二氧化钛，加氢脱硫，草酸钼，费歇尔-托普希反应，拉曼光谱法）。

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The aggregation behavior of ammonium heptamolybdate and sodium tungstate precursor solutions as a function of concentration and pH were investigated by Raman spectroscopy and Laser Light Scattering. The results agree with the aggregation scheme of simple (--->) hepta (--->) octa (--->) Mo(,36)O(,112)('-8) (--->) protonated polymeric species, for molybdate solutions. Tungstate solutions aggregate according to simple (--->) Y-polytungstate (--->) paratungstate-A (--->) paratungstate-B (--->) (PSI)-metatungstate.; The structure of molybdenum oxalate complexes in solution and on alumina were studied by Raman and FTIR spectroscopy. The results show that the molybdenum oxalate complex changes from a dimeric bidentate structure to a monomeric unidentate structure in solution as pH increases. Molybdenum oxalate complexes are stable compared to isopolymolybdates when supported on alumina.; The Fischer-Tropsch activity and selectivity of carbon-supported molybdenum catalysts were studied as a function of preparation conditions and potassium promotion. Catalysts prepared by equilibrium adsorption were better dispersed and showed a high activity as compared to catalysts prepared by the incipient wetness method. Potassium promotion increased the selectivity towards C(,2) and C(,3) hydrocarbons while reducing moderately the activity.; The nature of molybdate species on the titania surface, as a function of preparative variables, was followed by Raman and FTIR spectroscopy. The distribution of monomeric tetrahedral species, polymeric species and bulk like molybdenum trioxide depends on the loading, pH of the starting solution, method of catalyst loading, and pretreatment conditions. Addition of cobalt to titania supported molybdenum catalysts suppresses the formation of bulk MoO(,3) and leads to the formation of a cobalt-molybdate phase.; Hydrodesulfurization (HDS) activity and selectivity were determined at 350(DEGREES)C and 1 atmosphere for a series of molybdena-titania catalysts. For loadings at or below monolayer coverage, titania-supported Mo catalysts were found to be more active when compared with an industrial Co-Mo catalyst. Addition of cobalt increases the HDS activity modestly. The selectivity of these catalyst correlates well with the proposed model.; Surface acidity of these molybdena-titania catalysts was determined by using pyridine as a probe molecule. From the relative concentrations of Lewis acid sites, Bronsted acid sites and hydrogen bonding sites, the adsorption and aggregation mechanisms of molybdates on the titania surface were inferred.
机译：通过拉曼光谱和激光散射研究了七钼酸铵和钨酸钠前体溶液的聚集行为与浓度和pH的关系。结果与简单（--->）七（--->）八进制（--->）Mo（，36）O（，112）（'-8）（-）的聚集方案一致质子化的高分子物质，用于钼酸盐溶液。钨酸盐溶液根据简单的（--->）Y-多钨酸盐（--->）仲钨酸盐-A（->）仲钨酸盐-B（->）（PSI）-metungungstate聚集。通过拉曼光谱和FTIR光谱研究了溶液中和氧化铝上草酸钼配合物的结构。结果表明，随着pH的升高，草酸钼络合物从溶液中的二聚二齿结构变为单体不明结构。当负载在氧化铝上时，草酸钼配合物与异聚钼酸盐相比是稳定的。研究了碳载钼催化剂的费-托活性和选择性随制备条件和钾促进作用的变化。与通过初期湿润法制备的催化剂相比，通过平衡吸附制备的催化剂具有更好的分散性并显示出高活性。钾的促进提高了对C（，2）和C（，3）烃的选择性，同时适度降低了活性。二氧化钛表面上的钼酸盐种类的性质，作为制备变量的函数，随后是拉曼光谱和FTIR光谱法。单体四面体物质，聚合物物质和本体（如三氧化钼）的分布取决于负载量，起始溶液的pH值，催化剂负载量的方法以及预处理条件。在二氧化钛负载的钼催化剂中添加钴抑制了块状MoO（，3）的形成并导致了钼酸钴相的形成。对于一系列钼-二氧化钛催化剂，在350（DEGREES）C和1个大气压下确定了加氢脱硫（HDS）活性和选择性。对于单层覆盖率或低于单层覆盖率的负载，发现二氧化钛负载的Mo催化剂与工业Co-Mo催化剂相比更具活性。钴的添加适度地增加了HDS活性。这些催化剂的选择性与所提出的模型很好地相关。这些钼-二氧化钛催化剂的表面酸度通过使用吡啶作为探针分子来确定。从路易斯酸位，布朗斯台德酸位和氢键位的相对浓度，推断钼酸盐在二氧化钛表面的吸附和聚集机理。

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