Assessment and comparison of ordered & non-ordered supported metal oxide catalysts for upgrading propane to propylene

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

“…also concluded to a beneficial influence of the formation of Ca 2 V 2 O 7 pyrovanadate on the olefin selectivity in the ODH of n ‐octane [41] . Whereas too rapid redox exchanges were claimed to be responsible for over‐oxidation reactions in transition metal oxide‐like compounds, and isolated transition metal species were found to be too hardly reducible, [1c,3–4] metal clusters of limited size (potentially isolated from each other in phosphate matrices also referring to as the concept of isolation of active sites [4,10,12] ) were reported to be beneficial for a better control of the electronic exchanges in oxidation reactions [13–15,42] . In order to monitor the redox properties of the Ca 4 V 4 O 14 ‐containing samples, an in situ Raman investigation was carried out under successive reductive (H 2 (5 %)/Ar) and oxidative (O 2 (2.5 %)/Ar) atmospheres (Figure 12).…”

“…It is usually well accepted that highly‐polymerized oxide‐like catalytic species are detrimental to the control of the propene selectivity, [3] due to rapid electronic exchanges between adjacent metal species and/or fast surface oxygen ions mobility resulting in the overoxidation of adsorbed products to CO 2 [4] . Vanadium‐based systems were found among the most performant catalysts for the ODHP reaction [1c,2a,3] . For most supported vanadium systems, beside the support effect, [1b,5] and the vanadium coordination environment, [6] the propene formation rate per V atom (also defined as turnover frequency: TOF) has been found to depend on the vanadium surface density [3] and to reach an optimum for intermediate surface densities, [5c,7] suggesting that species of limited nuclearity would be beneficial to C 3 H 6 selectivity [2a] .…”

“…For most supported vanadium systems, beside the support effect, [1b,5] and the vanadium coordination environment, [6] the propene formation rate per V atom (also defined as turnover frequency: TOF) has been found to depend on the vanadium surface density [3] and to reach an optimum for intermediate surface densities, [5c,7] suggesting that species of limited nuclearity would be beneficial to C 3 H 6 selectivity [2a] . This motivated the design of highly‐dispersed species such as single sites for heterogeneous catalysis (SSHC) through metal anchoring of an organometallic complex, [1c,8] or controlled incorporation in hosting structures [9] . Typically, in BEA zeolite, the TOF of monomeric pseudo‐tetrahedral V species was found to be much higher than that of polynuclear oxide‐like entities present as extra‐framework species in the ODHP reaction [9b] .…”

Propylene Synthesis: Recent Advances in the Use of Pt-Based Catalysts for Propane Dehydrogenation Reaction

“…The reaction conditions therefore result in an increase in side reactions such as thermal cracking, deep dehydrogenation, coke formation and the sintering of the supported nanoparticles, limiting the average life of the catalyst [6]. To overcome the catalyst deactivation, it is therefore mandatory to employ a periodic regeneration through oxidative cycles to eliminate the coke, followed by reduction; moreover, oxygen-chlorine treatment can be carried out to partially redisperse agglomerated Pt particles [10].…”

“…Three different pH values (9)(10)(11) were used for the synthesis of Boron-modified ZrO 2 (B-ZrO 2 ), subsequently adopted as the supports of PtSn catalysts (PtSn/B-ZrO 2 -x); the characterization results showed that the acid strength increased with the synthesis pH [65]. In particular, the moderate interaction occurring between the metal species and B-ZrO 2 -10 support results in a stronger interaction between Pt and Sn.…”