کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1656907 | 1517608 | 2015 | 8 صفحه PDF | دانلود رایگان |

• Un-calcined K-OMS 2 catalyst can be synthesized by hydrothermal technique.
• Un-calcined OMS 2 crystalline phase was observed in all catalysts.
• K-OMS 2 can be prepared in lower aging temperature than other researchers.
• K-OMS 2 can be prepared in highly atomic ratios of Mn3 +/Mn4 + computed by XANES.
• The surface area plays more effective than atomic ratios of Mn3 +/Mn4 + values.
The synthesis of manganese-based octahedral molecular sieves of the type K-OMS 2 was designed by central composite design (CCD) method. The effect of aging time and temperature was considered for K-OMS 2 synthesis. Consequently, the synthesis was carried out through hydrothermal process without calcination and the obtained K-OMS 2 was tested for benzene oxidation. The physicochemical properties of as-synthesized K-OMS 2 catalysts were characterized by XRD, BET and SEM. The oxidative species of manganese were identified by analysis of the Mn K-edge XANES spectra. CCD results revealed that the crystallization conditions for K-OMS 2 synthesis were dependent on aging temperature and time. The specific surface area of K-OMS 2 was inversely proportional to the aging temperature. The K-OMS 2 sample with aging time of 21 h at aging temperature of 75 °C showed the best catalyst for benzene oxidation. This catalyst was a mixture of Mn2O3 and MnO2 with Mn3 +/Mn4 + ratio of 0.09 as evaluate by XANES technique. It was discovered that the K-edge energy of Mn in each as-synthesized K-OMS 2 samples was 6551.4 eV close to Mn3 + and Mn4 + species. The Mn3 +/Mn4 + ratios were found to have a range of 0.09–0.16. However, a decrease in Mn3 +/Mn4 + ratio and a corresponding decrease in catalytic activity were encountered at high aging time and temperature. Low aging temperature and long aging time could provide active species of manganese oxides for benzene oxidation.
Journal: Surface and Coatings Technology - Volume 271, 15 June 2015, Pages 217–224