Synergistic Effect Between Ca₄V₄O₁₄ and Vanadium‐Substituted Hydroxyapatite in the Oxidative Dehydrogenation of Propane

Abstract

The present work reports on a new type of V-based catalysts, namely V-substituted hydroxyapatites, and the influence of the synthesis conditions on their catalytic performance in the oxidative dehydrogenation of propane (ODHP) reaction. V xsubstituted hydroxyapatite materials prepared with the periodic addition of ammonia during the maturation step (V x -HAp-pHper) were shown to exhibit a Ca 4 V 4 O 14 phase in addition to the V-substituted hydroxyapatite phase for x greater than or equal to 3.5. TEM characterization of the biphasic samples allowed us to demonstrate that the Ca 4 V 4 O 14 phase was grown epitaxially on the V x -HAp nanorods. The close intimacy between the two phases was confirmed by NMR suggesting the involvement of V 4 + species. Consistently EPR data of the fresh and spent samples showed that V 4 + species may be stabilized at the boundaries of these two phases. The strong promotion of the oxidative dehydrogenation reaction to propene observed from 723 K for the V 4 -HAp-pH-per composition is attributed to a synergistic effect between the V x -HAp nanorods that enable the activation of propane and the Ca 4 V 4 O 14 phase that helps the redox exchanges. This synergy may be attributed to an easier electron delocalization on the V 4 O 14 units located at the phases' boundaries.

Hydroxyapatite Derived from Salmon Bone As Green Ecoefficient Support for Ceria-Doped Nickel Catalyst for CO2 Methanation

“… 17 , 18 Furthermore, because HA has a high thermal stability and is only structurally altered at temperatures above 1000 °C, the sintering of NiO species can be significantly reduced. The weakly basic nature of the HA surface and high thermal stability have been utilized and reported for various high-temperature catalytic reactions, including the oxidative coupling of methane, 19 the oxidative dehydrogenation of propane, 20 the dry reforming of methane, 21 the water gas shift reaction, 22 and CO oxidation. 23 However, few studies have been conducted on the possibility of using HA as a potential support for CO 2 methanation.…”

Phosphorus Co-Existing in Water: A New Mechanism to Boost Boron Removal by Calcined Oyster Shell Powder

“…However, this has been considered questionable because HAP is a good bio-porous material which can be substituted by heavy metal ions for Ca ions, oxyacid for phosphate ions, and halide ions for hydroxyl groups. The formation of HAP requires an excess of Ca, typically in the form of Ca(OH) 2 , as compared to the molar ratio of Ca and P in HAP [ 13 , 14 ]. Cost-effective and easily attainable Ca sources must be considered as an ideal approach to co-precipitation to retrieve B from solutions.…”