Application of the unique redox properties of magnesium ortho-vanadate incorporated with palladium in the unsteady-state operation of the oxidative dehydrogenation of propane
Application of the unique redox properties of magnesium ortho-vanadate incorporated with palladium in the unsteady-state operation of the oxidative dehydrogenation of propane
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DOI：
10.1016/j.jcat.2008.09.015
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发表时间：
2008-11
影响因子：
7.3
通讯作者：
S. Sugiyama;Y. Hirata;Keizo Nakagawa;K. Sotowa;K. Maehara;Y. Himeno;W. Ninomiya
中科院分区：
文献类型：
--
作者：
S. Sugiyama;Y. Hirata;Keizo Nakagawa;K. Sotowa;K. Maehara;Y. Himeno;W. Ninomiya
研究了掺Pd ~（2+）的正钒酸镁（Pd-ortho-MgVO）催化丙烷氧化脱氢反应，尽管人们一直认为正钒酸镁（Mg_3V_2O_8）在氧化脱氢反应中的催化活性很低。在0.75小时的运行，一个更高的活性比镁焦钒酸盐（单斜Mg 2 V2 O 7），这被认为是一个更活跃的催化剂氧化脱氢，观察到使用5%Pd-邻-MgVO。不幸的是，较高的催化活性随着时间的推移而下降，由于晶格氧从5%Pd-邻-MgVO的快速提取。虽然提取的晶格氧在氧化脱氢过程中在过量气态氧的存在下不再生，但在再氧化过程中在进料流中不存在丙烷的情况下容易再生。用扩展X射线吸收精细结构和51 V魔角自旋核磁共振分别证实了钯和钒物种在催化反应和再氧化过程中的氧化还原循环。本研究的结果表明，较高的催化活性，观察到使用5%的Pd-邻-MgVO在0.75小时的流可以保持通过使用非稳态操作与催化反应和催化剂再氧化相结合。
The oxidative dehydrogenation of propane on Pd2+-incorporated magnesium ortho-vanadate (Pd-ortho-MgVO) was examined, despite the long-held belief that magnesium ortho-vanadate (Mg3V2O8) demonstrates scant catalytic activity in oxidative dehydrogenation. At 0.75 h on-stream, a higher activity than that on magnesium pyro-vanadate (monoclinic Mg2V2O7), which is believed to be one of the more active catalysts for oxidative dehydrogenation, was observed using 5% Pd-ortho-MgVO. Unfortunately, the higher catalytic activity decreased with time on stream due to the rapid abstraction of lattice oxygen from 5% Pd-ortho-MgVO. Although the abstracted lattice oxygen was not regenerated during oxidative dehydrogenation in the presence of excess gaseous oxygen, it was easily regenerated during reoxidation in the absence of propane in the feedstream. Redox cycles of palladium and vanadium species during the catalytic reaction and reoxidation were confirmed using extended X-ray absorption fine structure around the Pd K-edge and51V magic-angle spinning nuclear magnetic resonance, respectively. The results of the present study suggest that the higher catalytic activity observed using 5% Pd-ortho-MgVO at 0.75 h on-stream can be maintained by using an unsteady-state operation in combination with the catalytic reaction and catalyst reoxidation.