在载体堇青石表面涂覆一层 L a Al O3作为第二载体 ,用浸渍法制备负载型 L a Mn O3、 L a Co O3等钙钛矿型燃烧催化剂时 ,发现能促进 L a Mn O3等活性相的生长 ,从而提高了二甲苯完全氧化的催化活性 ;对于负载型 L a-Co O3催化剂 ,可避...在载体堇青石表面涂覆一层 L a Al O3作为第二载体 ,用浸渍法制备负载型 L a Mn O3、 L a Co O3等钙钛矿型燃烧催化剂时 ,发现能促进 L a Mn O3等活性相的生长 ,从而提高了二甲苯完全氧化的催化活性 ;对于负载型 L a-Co O3催化剂 ,可避免因用γ- Al2 O3作第二载体而生成的低活性 Co Al2 O4类尖晶石相 。展开更多
Oxidative coupling of methane(OCM) was conducted over LaAlO3X catalysts that were prepared by a coprecipitation method using different co-precipitation pH values(X = 6–10). The aim is to investigate the effect of p H...Oxidative coupling of methane(OCM) was conducted over LaAlO3X catalysts that were prepared by a coprecipitation method using different co-precipitation pH values(X = 6–10). The aim is to investigate the effect of p H values on the catalytic activity of La AlO3 catalysts in this reaction. The results showed that the co-precipitation pH value affected greatly on the formation of chemical species of precipitate precursors in the co-precipitation step, leading to different phases of the finally obtained LaAlO3 catalysts.When the co-precipitation pH value increased up to 8, the lanthanum-related phases such as La2 O3 and La(OH)3 were gradually formed as by-products, preventing the formation of LaAlO3 perovskite crystalline structure and facilitating the formation of oxygen vacancies on catalyst surface. However, at pH value of9 or higher, the lanthanum content in the precipitate precursor was increased greatly. Not LaAlO3 perovskite but lanthanum-related phases were developed as main phases, reducing their catalytic activities in this reaction. Among LaAlO3 catalysts, the one prepared at pH = 8 showed the highest C2 yield due to its well-developed oxygen vacancies and electrophilic lattice oxygen. Therefore, the co-precipitation pH value strongly affected the LaAlO3 catalyst activity in OCM reaction. A precious pH control should be required to prepare various perovskite catalysts for the OCM.展开更多
Luminescent properties of Y2O3 and LaAlO3 nanopowders doped with Pr^3＋ ions and PMMA-based composite materials doped with these powders were reported. The set of active nanopowders differing in praseodymium ions conc...Luminescent properties of Y2O3 and LaAlO3 nanopowders doped with Pr^3＋ ions and PMMA-based composite materials doped with these powders were reported. The set of active nanopowders differing in praseodymium ions concentration was prepared using sol-gel method and carefully characterized with respect to emission properties in the visible spectral range. In particular, the excitation and emission spectra were measured together with fluorescence decay profiles and the differences between optical properties of these materials were discussed and compared with data available for bulk materials. Finally, the PMMA-based composite materials doped with Pr^3＋：Y2O3 and Pr^3＋：LaAlO3 nanopowders were manufactured and characterized. The obtained results showed that polymer composites doped with active nanopowders in general tended to keep the luminescent properties of the original nanopowders.展开更多
文摘在载体堇青石表面涂覆一层 L a Al O3作为第二载体 ,用浸渍法制备负载型 L a Mn O3、 L a Co O3等钙钛矿型燃烧催化剂时 ,发现能促进 L a Mn O3等活性相的生长 ,从而提高了二甲苯完全氧化的催化活性 ;对于负载型 L a-Co O3催化剂 ,可避免因用γ- Al2 O3作第二载体而生成的低活性 Co Al2 O4类尖晶石相 。
基金supported by C1 Gas Refinery Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science,ICT&Future Planning(2015M3D3A1A01064908)
文摘Oxidative coupling of methane(OCM) was conducted over LaAlO3X catalysts that were prepared by a coprecipitation method using different co-precipitation pH values(X = 6–10). The aim is to investigate the effect of p H values on the catalytic activity of La AlO3 catalysts in this reaction. The results showed that the co-precipitation pH value affected greatly on the formation of chemical species of precipitate precursors in the co-precipitation step, leading to different phases of the finally obtained LaAlO3 catalysts.When the co-precipitation pH value increased up to 8, the lanthanum-related phases such as La2 O3 and La(OH)3 were gradually formed as by-products, preventing the formation of LaAlO3 perovskite crystalline structure and facilitating the formation of oxygen vacancies on catalyst surface. However, at pH value of9 or higher, the lanthanum content in the precipitate precursor was increased greatly. Not LaAlO3 perovskite but lanthanum-related phases were developed as main phases, reducing their catalytic activities in this reaction. Among LaAlO3 catalysts, the one prepared at pH = 8 showed the highest C2 yield due to its well-developed oxygen vacancies and electrophilic lattice oxygen. Therefore, the co-precipitation pH value strongly affected the LaAlO3 catalyst activity in OCM reaction. A precious pH control should be required to prepare various perovskite catalysts for the OCM.
基金Project supported by Ministry of Science and Higher Education (N N515 518538)
文摘Luminescent properties of Y2O3 and LaAlO3 nanopowders doped with Pr^3＋ ions and PMMA-based composite materials doped with these powders were reported. The set of active nanopowders differing in praseodymium ions concentration was prepared using sol-gel method and carefully characterized with respect to emission properties in the visible spectral range. In particular, the excitation and emission spectra were measured together with fluorescence decay profiles and the differences between optical properties of these materials were discussed and compared with data available for bulk materials. Finally, the PMMA-based composite materials doped with Pr^3＋：Y2O3 and Pr^3＋：LaAlO3 nanopowders were manufactured and characterized. The obtained results showed that polymer composites doped with active nanopowders in general tended to keep the luminescent properties of the original nanopowders.
