Molybdenum distribution ratios

A theoretical treatment of metal halide extractions, encompassing various cationic, anionic, and polymeric species, has been presented by Diamond, who was particularly interested in molybdenum(VI) halides. Section 23-5 examines in more detail the questions of distribution ratios and chemical equilibria in the aqueous and organic phases. 

Taylor SR, McLennan SM (1985) The Continental Crust Its Composition and Evolution. Blackwell, Boston Tuit CB, Ravizza G (2003) The marine distribution of molybdenum. Geochim Cosmochim Acta 67 A4950 Tumlund JR, Keyes WR, Peiffer GL (1993) Isotope ratios of molybdenum determined by thermal ionization mass spectrometry for stable isotope studies of molybdenum metabolism in humans. Anal Chem 65 1717-1722... 

In cattle, molybdenosis is characterized by a foamy diarrhea which may be bloody. Affected cattle also have depigmented hair. Molybdenosis is a subacute to chronic condition and occurs when the cop-per molybdenum ratio is 2 1 or less. The condition shows geographical distribution and occurs in areas deficient in copper or having an excess of molybdenum (e.g., parts of California, Oregon, Nevada, and... 

Furthermore, [NiCit] can readily be reduced to metallic nickel (c.f. Eq. 39) at the potential where the Ni-Mo alloy is formed. Yet, no such reduction is shown in Eqs. (42) and (43), in which Mo is first reduced from the hexavalent molybdate to the tetrava-lent molybdenum dioxide, and then further to metallic molybdenum. A solution, in which the concentrations of Ni and Cit - were equal, was used and it was assumed that all citrate ions were bound to Ni in [NiCit] . This assumption ignores the possible existence of complexes of the type [(Mo04)(Cit)(H)ni] (written for short as [l,l,m] where m is the number of protons in the complex), in spite of the fact that such complexes are well known (cf.. Fig. 13a). In addition, detailed calculation of the distribution of species in a NP and Cit - mixture shows that, when the ratio of the concentrations of the two ions is unity, there are still a few percents of free Ni and Cif" ions not bound in the complex, as seen if Fig. lb. 

The molybdenum-zeolites prepared by adsorption and decomposition of Mo(CO)g have been shown to be active CO hydrogenation catalysts. The product distribution varies with the charge-compensating cation in the zeolite and Si/Al ratio. An LPG selectivity of up to 575t has been observed. 

The nitrogen content of the molybdenum nitride hydrodesulfurization catalysts was determined by x-ray phoioeleciron spectroscopy. The Mo 3d spectra were fitted into six sets of Mo doublets (Mo 3dv and 3ds ) with each fwhm corresponding to six different molybdenum species. The XPS N Is peak in the catalysts was deconvoluted with the individual Mo 3pt 2 signals based on the same distribution of the Mo 3d electrons of Mo 3p3 2 as the Mo 3d. 2 spectra. This method is accurate for the determination of the N/Mo ratio in molybdenum nitrides with a small error during hydrotlesulfurization reaction. 

The loss of free atoms in the atomizer is also a function of the chemistry of the sample. If the oxide of the analyte element is readily formed, the free atoms will form oxides in the flame and the population of free atoms will simultaneously decrease. This is the case with elements such as chromium, molybdenum, tungsten, and vanadium. On the other hand, some metal atoms are stable in the flame and the free atoms exist for a prolonged period. This is particularly so with the noble metals platinum, gold, and silver. Adjusting the fuel/oxidant ratio can change the flame chemistry and atom distribution in the flame as shown in Fig. 6.17(b). Atoms with small ionization energies will ionize readily at high temperatures (and even at moderate temperatures). In an air-acetylene flame, it can be shown that moderate concentrations of potassium are about 50% ionized, for example. Ions do not absorb atomic lines. 

The selectivity and product distribution on various Mo-based catalysts show several common features that differ from group 8-10 metals (95,113). First, they show a high paraffin/olefin ratio. This seems due to a secondary reaction of initially formed olefins with dihydrogen to form paraffins. Second, they form a large amount of hydrocarbons of C2-C5, and the concentration of hydrocarbons heavier than C5 is very low. The last feature is the production of a large amount of CO2 due to the secondary water gas shift reaction of initially produced water and CO. These features are similar to those reported for Mo metal, oxides, nitrides, and sulfides, and reflect the fact that the active phase of molybdenum under working conditions seems to be molybdenum carbide irrespective of the phase present in fresh catalysts (112,114). 

ROMP readily using the Schrock molybdenum carbene initia-tors. The cis/trans ratio in the product polymer and the molecular-weight distribution depended on the substituents at molybdenum in the initiator used and the conditions adopted. The well-defined Schrock initiator, Mo(=CHC(CH3)2Ph) (=NAr)(OC(CH3)(CF3)2)2/ gave a relatively slow reaction to give the expected precursor polymer in good yield, a molecular weight of about M 60 000kDa and relatively broad polydispersity. 

---