Showing papers on "Ammonium tetrathiomolybdate published in 1993"

Physicochemical characteristics of electrochemically deposited molybdenum sulfide and polypyrrole-tetrathiomolybdate/molybdenum trisulfide composite electrodes

Abstract: Amorphous molybdenum sulfide and polypyrrole-tetrathiomolybdate/molybdenum sulfide thin films obtained by electrodeposition from aqueous solutions of ammonium tetrathiomolybdate and pyrrole + ammonium tetrathiomolybdate, respectively, have been characterized by elemental analysis, Auger electron spectroscopy, X-ray photoelectron spectroscopy, infrared spectroscopy, and X-ray absorption spectroscopy. The authors' data revealed that the structure of electrochemically and thermally produced molybdenum trisulfide are identical but that additional sulfur is also present in the electrodeposited material. On the other hand, polypyrrole films grown in the presence of tetrathiomolybdate as the counterion also contains molybdenum trisulfide. Elemental analysis and X-ray absorption spectroscopy of polypyrrole-tetrathiomolybdate/molybdenum trisulfide thin film suggest that 30% of molybdenum is under the MoS[sub 4][sup 2[minus]] form and 70% is present as MoS[sub 3]. 34 refs., 9 figs., 1 tab.

Swelling pretreatment of coals for improved catalytic temperature-staged liquefaction

Abstract: Two coals, a Texas subbituminous C and a Utah high-volatile A bituminous, were used to examine the effects of solvent swelling and catalyst impregnation on liquefaction conversion behavior in temperature-staged reactions for 30 min each at 215 and 425 °C in H 2 and 95:5 H 2 :H 2 S atmospheres. Methanol, pyridine, tetrahydrofuran, and tetrabutylammonium hydroxide were used as swelling agents. Molybdenum-based catalyst precursors were ammonium tetrathiomolybdate, molybdenum trisulfide, molybdenum hexacarbonyl, and bis(tricarbonylcyclopentadienylmolybdenum). Ferrous sulfate and bi(dicarbonylcyclopentadienyliron) served as iron-based catalyst precursors

Molybdenum-induced changes in the epiphyseal growth plate

Abstract: Molybdenum (Mo), at high concentrations, induces changes in the epiphyseal growth plate through its effects on copper (Cu) metabolism but it is unclear whether or not Mo can induce changes independent of its effects on copper status. To this end, the effect of Mo on longitudinal bone growth was examined in rats. Dietary Mo was given either as ammonium heptamolybdate or as ammonium tetrathiomolybdate, the latter producing a marked Cu deficiency. There was a significant reduction in longitudinal bone growth in both groups; however, growth plate width was increased only in the Cu-deficient animals due to an increase in the width of the zone of transitional/hypertrophic chondrocytes. Both glucose 6-phosphate dehydrogenase activity and cell proliferation (assessed by bromodeoxyuridine incorporation) were markedly decreased in the proliferating zone of the growth plate in both Mo-treated groups. These changes were not apparently related to changes in circulating vitamin D metabolites or insulin-like growth factor-1. The results indicate that excess Mo impairs cell proliferation within the growth plate, whereas the effects of copper deficiency are more related to chondrocyte differentiation. Thus, Mo can induce changes in longitudinal bone growth which are distinct from those resulting from Cu deficiency.