Toward understanding methane coupling

The role of the oxide catalyst in the methane coupling reaction is to activate the methane to form methyl radicals. These radicals are released into the gas phase, where they react further with molecular oxygen and other hydrocarbon intermediates to form the final product mix. The preferred catalysts efficiently form methyl radicals from methane without combusting the reaction products. The main impetus of this research work has been to try to find out what controls this activity. In examining the relationship between oxide structure and activity, the authors have concentrated on the simple oxide MgO. This oxide can be prepared by three different routes: burning magnesium ribbon in air, thermal decomposition of magnesium hydroxide, and thermal decomposition of magnesium basic carbonate

Relationship between morphology and catalytic performance of lithium and gold doped magnesium oxide catalysts for the oxidative coupling of methane

A detailed study is presented of the relationship between morphology and catalytic performance of Li and Au doped MgO prepared by the thermal decomposition of the hydroxide. Addition of Li to MgO causes a loss of the characteristic morphology of the precursor MgO due to grain growth via agglomeration of crystallites and grain boundary dislocations are evident. In contrast, Au doping of MgO does not lead to an increase in grain size. For both Li and Au doped MgO, dislocations are observed that are immobile and are proposed to be of the type (110) which are probably pinned by Li or Au ions segregating to the line of the defect. The importance of these dislocations is discussed with respect to the catalytic performance of Li and Au doped MgO catalysts for the oxidative coupling of methane

Structural aspects of magnesium oxide catalysts for the oxidative coupling of methane

A study of the structure and catalytic performance of Li doped MgO catalysts is presented. The addition of Li to MgO causes a loss of the characteristic morphology of the precursor MgO due to agglomeration of crystallite grains. Growth of MgO grains leads to the formation of grain boundary dislocations. In addition, dislocations are also observed in the bulk of the grains. These dislocations are immobile and are suggested to be of the type a/2(110) and are probably pinned by Li+ segregating to the line of the defect. The importance of these dislocations is discussed with relevance to the partial oxidation of methane

Effects of interferon alpha on human osteoprogenitor cell growth and differentiation in vitro

The specific effects of interferon alpha (IFNalpha), on the differentiation pathways of human osteogenic cells are not known. The aim of this study was to investigate possible effects of IFNalpha on osteogenic development by investigating cell differentiation, colony formation (colony forming unit-fibroblastic, CFU-F), cell proliferation, and gene expression, in particular bone morphogenetic protein (BMP) expression, of human bone marrow osteoprogenitor cells. Human bone marrow fibroblasts were cultured with or without the addition of IFNalpha (5-1,000 IU/ml) in the presence and absence of dexamethasone (10 nM) and ascorbate (100 microM), which are agents known to affect osteogenic differentiation. IFNalpha produced a significant dose-dependent inhibition of cell proliferation and alkaline phosphatase specific activity at concentrations as low as 50 IU/ml. IFNalpha (50-1,000 IU/ml) inhibited the stimulation of alkaline phosphatase specific activity induced by ascorbate and dexamethasone. Examination of CFU-F showed dose- and time-dependent inhibitions of colony formation and reductions in both colony size and alkaline phosphatase-positive CFU-F colonies particularly at earlier times. Reactivity with an antibody specific for osteoprogenitors (HOP-26), was reduced in IFNalpha-treated cultures. Northern blot analysis showed a significant dose-dependent up-regulation of BMP-2 mRNA, estrogen receptor alpha mRNA and osteocalcin mRNA expression in ascorbate/dexamethasone cultures. In contrast, IFNalpha significantly inhibited BMP-2 mRNA expression in the absence of ascorbate and dexamethasone. In conclusion, IFNalpha inhibits human osteoprogenitor cell proliferation, CFU- F formation, HOP-26 expression, and alkaline phosphatase specific activity and modulates BMP-2 gene expression. These results suggest a role for IFNalpha in local bone turnover through the specific and direct modulation of osteoprogenitor proliferation and differentiation

Co-precipitated copper zinc oxide catalysts for ambient temperature carbon monoxide oxidation: effect of precipitate ageing on catalyst activity

A detailed study of the morphological changes that occur during the ageing of a copper zinc oxide (Cu ∶ Zn 2 ∶ 1), formed by co-precipitation from the nitrates is reported and discussed. Using TEM and STEM-EDS, the composition and morphology of the non-calcined precursor are observed to change from an initial amorphous state to micro-crystalline aurichalcite and rosasite, which are present as needles and platelets, respectively. In addition, the detailed microscopy study has shown that a dispersion of Cu-rich nanoparticles is progressively formed as the precipitate ages. On calcination at 550 °C, an intimate mixture of CuO and ZnO crystallites is formed, and using STEM-EDS analysis it is shown that the CuO contains Zn, and the ZnO contains Cu in solid solution. The highest incorporation of Zn into CuO correlates with the highest concentration of the Cu-rich nanoparticles in the precursor. The catalytic activity of the calcined copper zinc oxide is also correlated with the highest incorporation of Zn into CuO for the oxidation of carbon monoxide at 20 °C