Vanadium Oxide Based Nanostructured Materials for Catalytic Oxidative Dehydrogenation of Propane: Effect of Heterometallic Centers on the Catalyst Performance

Abstract

Catalytic properties of a series of new class of catalysts materials-[Co 3 (H 2 O) 12 V 18 O 42 (XO 4 )].24H 2 O (VNM-Co), [Fe 3 (H 2 O) 12 V 18 O 42 (XO 4 )].24H 2 O (VNM-Fe) (X = V, S) and [H 6 Mn 3 (H 2 O) 12 V 18 O 42 (VO 4 )].30H 2 O for the oxidative dehydrogenation of propane is studied. The open-framework nanostructures in these novel materials consist of three-dimensional arrays of {V 18 O 42 (XO 4The effect of change in the heterometallic center M (M = Mn, Co, Fe) of the linkers on the catalyst performance was studied. The catalyst material with Co in the linker showed the best performance in terms of propane conversion and selectivity at 350°C. The material containing Fe was most active but least selective and Mn containing catalyst was least active. The catalysts were characterized by Temperature Programmed Reduction (TPR), BET surface area measurement, Diffuse Reflectance Infrared Fourier Transform Spectroscopy, and X-ray Absorption Spectroscopy. TPR results show that all three catalysts are easily reducible and therefore are active at relatively low temperature. In situ X-ray absorption near edge spectroscopy (XANES) and extended X-ray absorption fine structure spectroscopy (EXAFS) studies revealed that the oxidation state of Co(II) remained unchanged up to 425°C (even after pretreatment). The reduction of Co(II) into metallic form starts at 425°C and this process is completed at 600°C.

Oxidative Dehydrogenation Properties of Novel Nanostructured Polyoxovanadate Based Materials

“…The reduction of Co 2? in Co-POV starts after 400°C as reported earlier by X-ray Absorption Near Edge Structure (XANES) [23]. Co-POV has a very broad reduction peak with a T max at 386°C.…”

[V16O38(CN)]9–: A Soluble Mixed-Valence Redox-Active Building Block with Strong Antiferromagnetic Coupling

“…8 The cluster-like topologies of polyoxovanadates endow them with excellent capabilities for encapsulating neutral and anionic species, which influence the size and shape of the clusters. A variety of cluster architectures have been observed, with a few groups being most prevalent in terms of their frequency of formation, such as [V 15 O 36 ] n − , 9 [V 15 O 42 ] n − , 10 and [V 18 O 42 ] n− 11,10b clusters. A smaller but equally interesting group is based on the [V 16 O 38 (X)] n− cluster.…”

The Effects of P-Atoms on the Selective Dehydrogenation of C6H10 over Model Ru Surfaces

“…As such, barriers for the C–C cleavage should be increased or pathways to remove carbon from surfaces should be incorporated without sacrificing rates or selectivities for kinetically relevant C–H bond rupture events. Oxidative dehydrogenation of alkanes with reactive metal oxides (e.g., V 2 O 5 , MoO 3 , WO 3 , and Ta 2 O 5 ) addresses several of these points − because the reaction conditions reduce the coverage of surface carbon and metal oxides do not cleave C–C bonds by the pathways that plague metal surfaces . Yet, oxidative dehydrogenation suffers from lower selectivities toward alkenes because the presence of reactive oxygen leads to the formation of undesirable CO and CO 2 . , …”