Pathway to defective highly active and stable MoVSbOx catalysts for ethane oxidative dehydrogenation through a dislodging process involving controlled combustion of amino-organic compounds

Abstract

MoVSbOx are synthesized using a new methodology that allows phase M1 nanorods exhibiting {001}, {120} and {210} lateral facets with accessible active sites to be created. During thermal activation, the combustion of the amino-organic compounds used in the synthesis generates defects along lateral facets, while the treatment with nitrogen takes octahedrally coordinated Mo, V and Sb units out of M1 structure. These defects facilitate the accessibility to additional active sites thereby producing very efficient catalysts for ethane oxidative dehydrogenation (E-ODH). Besides active phase M1, several additional crystalline phases are produced, monitored by TG/DSC and identified/quantified by XRD. The (trans)formation mechanism of them is elucidated by in-situ E-STEM analysis. The active site is determined by high resolution HAADF-STEM. Mo, V and Sb work synergically in the RedOx process, and the oxidation state balance is crucial for high activity and ethylene selectivity. The catalysts produced are very active (75 %), selective (90 C%) and stable over time in E-ODH. In-situ E-STEM under E-ODH conditions probes the stability of the MoVSbOx, a feature that is catalytically demonstrated in a continuous 480 h experiment in a bench-scale reactor on the quadrilobe-shaped scaled-up catalyst.