Selective oxidative dehydrogenation of ethane on MoVTeNbO mixed metal oxide catalysts

摘要

MoVTeNbO catalysts,prepared by hydrothermal synthesis,are active and highly selective in the ODH of ethane,especially those with a Mo-V-Te-Nb molar ratio of 1-0.15-0.16-0.17 and heat-treated at 600-650 degC.On the best catalyst,selectivities higher than 80% at ethane conversion levels higher than 80% have been obtained operating at relatively low reaction temperatures(340-400 degC).Thus,yields of ethylene of ca.75% have been obtained,which exceeds the best yield reported in the literature.Te_2M_20O_57(M = Mo,V,Nb)and(V,Nb)-substituted sigma-Mo_5O_14,in addition to small amounts of the Te_(0.33)MO_(3.33)(M = Mo,V,Nb)phase,can be proposed in the most selective catalysts from XRD,SAED,and HREM results.However,the catalytic performance in ethane oxidation can mainly be related to the presence of the multifunctional Te_2M_20O_57 orthorhombic phase in cooperation with the Mo_5O_14-type phase.The nature of active and selective sites is discussed.