کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
27507 | 44027 | 2013 | 8 صفحه PDF | دانلود رایگان |
• Synthesis method controls the local structure and activity of V-oxides in V-MCM-41.
• Exposed tetrahedral VO4 species are efficient in photocatalytic partial oxidation of methane with NO into methanol.
• Methane coupling reaction products are obtained on confined VO4 species.
• Interaction between NO and the complex of V4+ species and methyl radical results in the methanol formation.
Vanadium-containing MCM-41 mesoporous molecular sieves with tetrahedrally coordinated VO4 species have been prepared by two direct synthesis methods under acidic and basic conditions as well as impregnation method. V-MCM-41 prepared in acidic solution and imp-V/MCM-41 exhibit high activity and methanol selectivity for the photocatalytic partial oxidation of methane with NO under UV irradiation at 295 K. However, V-MCM-41 prepared in basic solution shows only a low activity for the coupling reaction of methane. Photoluminescence, UV–vis, photoadsorption and ESR measurements reveal that V-MCM-41 prepared in acidic solution contains VO4 species exposed on a silica surface, while the catalyst prepared in basic solution contains VO4 species confined within a silica layer. The exposed tetrahedral VO4 species act as active sites for the formation of methanol. Furthermore, it is found that the V4+ species and methyl radicals formed by UV irradiation of the exposed VO4 species with methane interact easily with NO, resulting in the selective formation of methanol.
Journal: Journal of Photochemistry and Photobiology A: Chemistry - Volume 264, 15 July 2013, Pages 48–55