Formation of Oxygen Radical Sites on MoVNbTeOx by Cooperative Electron Redistribution

Abstract

A novel pathway of increasing the surface density of catalytically active oxygen radical sites on a MoVTeNb oxide (M1 phase) catalyst during alkane oxidative dehydrogenation is reported. The novel sites form when a fraction of Te is reduced and emitted from the M1 crystals under catalytic operating conditions, without compromising structural integrity of the catalyst framework. Density functional theory calculations show this Te reduction induces multiple inter-related electron transfers, and the associated cooperative effects lead to the formation of O radicals. The in situ observations identify complex dynamic changes in the catalyst on an atomistic level, highlighting a new way to tailor structure and dynamics for highly active catalysts.

Site specific and localized structural displacements in open structured multimetallic oxides

“…17,18 They have been the subject of numerous studies that focused on the understanding of their catalytic and structural properties also including operando/ in situ investigations. 7,[9][10][11][12][13]16,[19][20][21][22][23][24][25][26][27][28][29] A crystallographic model is shown in Fig. 1A.…”

“…31 Detailed beam damage studies and their impact on the structure have been addressed elsewhere for similar M1 samples. 2,23 Structural changes that arise due to the electron beam are expressed by an immediate amorphization that spreads from the surface to the bulk or removal of Te from the channel sites. Our studies suggest that under the applied imaging conditions (Mo,V,Te,Nb)O x can be at least 20 minutes exposed continuously to the electron beam without noticeable morphological changes ( Fig.…”

On the Promoting Effects of Te and Nb in the Activity and Selectivity of M1 MoV-Oxides for Ethane Oxidative Dehydrogenation

“…Thus, the higher activity of low-Te catalysts is concluded to be associated with a higher active site density. Conceptually, this can be caused by (i) the creation of additional oxygen radical sites in the material by partial Te reduction under reaction conditions [44] and/or (ii) a higher concentration of V 5+ located in active surface lattice positions of the M1 framework.…”

Defect-rich TiO2 in situ evolved from MXene for efficiently oxidative dehydrogenation of ethane

“…The increasing demand of ethylene as basic feedstock has stimulated the development of new process routes 4,5 . Therein, oxidative dehydrogenation (ODH) of ethane to ethylene is attracting extensive attention with more thermodynamic favorable process and lower energy cost than direct or steam cracking, particularly along with the vast exploration of shale gas resources 6,7 .…”