Hopcalite mixed oxides were used as support of the catalyst for the synthesis of diphenyl carbonate (DPC) by oxidative carbonylation of phenol .The catalyst was characterized by scanning electron microscopy (SEM), X-ray power diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The results show that the size of the particles is well-distributed and the physical structure is favorable, which contribute to the reaction efficiently. The main crystal phase in catalyst is CuMn2O4, CoMn2O4and Pd0.5Pd3O4, and the valency of Mn and Co remains unchanged. Finally, the synthesis of DPC was carried out and it was found that the yield and selectivity could reach 43.5% and 99.6%, respectively.
The difference of Cu-Co-Mn mixed oxides and hopcalite as support in synthesis of diphenyl carbonate by oxidative carbonylation of phenol was studied. The catalysts were characterized by transmission electron microscopy, scanning electron microscopy, X-ray power diffraction, and X-ray photoelectron spectroscopy. The results show that the average particle diameter of the former catalyst is about 40 nm, whereas the other catalyst is about 0.5 μm. The main crystal phase in the former catalyst is Co2MnO4and Pd0.5Pd3O4, which in the latter catalyst is CuMn2O4, CoMn2O4and Pd0.5Pd3O4.The oxygen atoms lose electrons and form oxygen vacancies in.Pd0.5Pd3O4and Co2MnO4of the former catalyst, which destroys the crystal integrity and prompts the oxygen adsorption on the crystal surface. The oxygen atoms lose electrons and form oxygen vacancies in.Pd0.5Pd3O4of the latter catalyst. Finally, it was found that the difference of the yield and selectivity of the both catalysts was not remarkable.
Homogenization treatment is vital for eliminating eutectic structure and ensuring a preferable microstructure foundation for Aluminum Lithium (Al-Li) alloys. In this paper, solidification phases in an as-cast Al-Li alloy were revealed and their evolutions during multiple homogenization processes were analyzed by means of scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and differential scanning calorimetry (DSC) analysis. The results showed that the as-cast microstructure mainly contained needlelike Al2CuLi and Al2Cu phase, large size Cu-rich phases and netlike Ag-containing phases attached to them. As the alloy homogenized by 455°C/16h, except for needle-like phases inside grains, part of phases on grain boundaries had dissolved into the matrix and exhibited rounded shapes. As homogenized by 455°C/16h+495°C/16h, Ag-containing phase had completely dissolved into the matrix while the Cu-rich phases remained and showed two different morphologies depending on whether Mg element was contained. Prolonging the second homogenization time to 28h, no obvious change occurred for the Cu-rich phase. As homogenized by 455°C/16h+495°C/20h+512°C/20h, most Cu-rich phase had dissolved into the matrix while residual phase was mainly Fe-containing phase. This proposes an effective way to eliminate various solidification phases in Al-Li alloys and identify their contents.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.