Effect of K and Bi doping on the M1 phase in MoVTeNbO catalysts for ethane oxidative conversion to ethylene

Statistically Guided Synthesis of MoV-Based Mixed-Oxide Catalysts for Ethane Partial Oxidation

“…As the primary Mo-V-O phase, hallmarked by the characteristic 22 • XRD peak, has been attributed to the preferential oxidation towards olefins and acids [20,54], it is reasonable to assume that the destabilization of this phase and secondary-phase formation induced by Cs would negatively affect activity through the loss of AA and ethylene-selective sites or formation of combustion sites. This type of structural disturbance induced by dopant addition to the base Mo-V-O structure is markedly different from that observed by others, where activity has been found to increase with increased dopant concentrations accompanied by higher defect densities and more polydisperse crystallites [24]. Additionally, decreased activity can also be attributed to a disruption of the crystalline M1/M2 structure, which can hinder lattice oxygen mobility that results in a loss in selectivity towards acids and olefins from alkane oxidation [22,36,55].…”

“…In addition to studies focused on stabilizing the Mo-V-O catalyst, recent studies have been dedicated to improving the catalytic performance through the incorporation of promoters. Such promoters are typically either acid/base elements, such as tellurium [10,14], calcium, potassium [24], or transition metals with varying redox properties, such as palladium, nickel, and titanium [3,21,22]. Optimal loadings of acid/base elements are typically on the same order of magnitude as the loading of niobium into the base catalyst, such as Mo 6 V 2 Te 1 O x and Mo 6 V 2 Sb 1 O x [25], where the acid/base elements in this case were tellurium and antimony in place of the niobium.…”

“…Optimal loadings of acid/base elements are typically on the same order of magnitude as the loading of niobium into the base catalyst, such as Mo 6 V 2 Te 1 O x and Mo 6 V 2 Sb 1 O x [25], where the acid/base elements in this case were tellurium and antimony in place of the niobium. Similarly, in cases where both the niobium and an additional acid/base element is present, their atomic ratio remains at approximate unity, such as Mo 1 V 0.22 Nb 0.15 Te 0.23 [15,24,26]. Interestingly, in some cases the destabilization of the primary Mo-V-O phase has not resulted in decreased catalytic activity, possibly due to the formation of new active sites in lieu of the Mo-V-O phase.…”

“…Interestingly, in some cases the destabilization of the primary Mo-V-O phase has not resulted in decreased catalytic activity, possibly due to the formation of new active sites in lieu of the Mo-V-O phase. One such example is the incorporation of small amounts of alkali metals such as potassium, or basic metals such as bismuth, to MoVTeNbO [24]. Due to extensive segregation of the crystalline structure of mixed-oxide catalysts upon addition of dopants, forming a clear correlation between catalyst structure, dopants, and performance is currently challenging when comparing the varied literature [24,[27][28][29][30].…”

Characterization of MoVTeNbOx Catalysts during Oxidation Reactions Using In Situ/Operando Techniques: A Review

“…Due to its unique redox properties, CeO 2 is an excellent oxygen storage material which can consequently increase the abundance of V +5 on the catalyst surface [30]. A similar improvement in ethylene yield is achieved by Ishchenko et al with Bi-doped M1 samples, which increases the surface V +5 /V +4 ratios [31]. In another XPS study by Nguyen et al, the surface V +5 content is claimed to be directly related to the total bulk V content [32].…”