Activity For Oxidative Dehydrogenation Research Articles

Surface anchoring requirements for vanadia clusters on titanium oxide surfaces and their impact on activity for oxidative dehydrogenation of ethanol

Titanium oxide site requirements for the anchoring of catalytically active forms of dispersed vanadia species are investigated. Using a series of oxygen-modified titanium nitride materials, we systematically modify the available vanadia-anchoring moieties on the titanium-bearing support surface. This strategy in turn results in a very narrow size distribution of well-dispersed vanadia clusters anchored on the support. This synthesis technique ensures that only highly dispersed vanadia is present on the catalyst surface even at nominal monolayer coverages. A deeper insight into the catalytic behavior for ethanol partial oxidation of the active vanadia species is obtained by comparing intrinsic kinetic and thermodynamic parameters of kinetically relevant reaction steps (heat of ethanol adsorption, hydrogen abstraction activation energy, and the energetics of catalyst reoxidation). It is found that these parameters are dependent on the relative amount of oxygen in the titanium-bearing support and the resulting distribution of vanadia species, which validates the premise of a potential participation of lattice oxygen atoms of the titania support into the catalytic activity of active vanadia species.

N, P codoped hollow carbon prisms for efficient oxidative dehydrogenation reaction with both enhanced activity and selectivity

Carbon materials have stimulated tremendous interest in oxidative dehydrogenation (ODH) of alkane to olefin molecules at low temperature. Unfortunately, its further development has been seriously hindered due to the unsatisfactory catalytic performance. To tackle these challenges, nitrogen and phosphorus codoped hollow carbon prisms (NPC) are designed with controllable surface functional groups through supramolecular pre-assembly and substitution reaction from guanine and hexachlorotriphosphazene. The resultant catalysts can achieve both high catalytic activity (63 % conversion) and styrene selectivity (90 %) in ODH of ethylbenzene, outerperforming previous reported carbon-based catalysts. Structural characterizations, kinetics measurements and theoretical results unravel that nitrogen doping can promote nucleophilicity of –CO, thus improving the catalytic activity. The phosphorus doping not only changes reaction rate-determining step from activation of O2 in N-doped carbon to activation of –C–H bond of EB in N,P-codoped carbon, but also inhibits the formation of electrophilic oxygen species, which enhances selectivity of styrene. The current work provides a facile strategy for preparation of functional NPC catalyst and physical–chemical insights on the structure–activity relationship of NPC catalysts, paving the way for further development of the highly efficient non-metallic catalytic systems.

Cobalt catalyzed ethane dehydrogenation to ethylene with CO2: Relationships between cobalt species and reaction pathways

TiO2, ZrO2 and a series of TiO2-ZrO2 (TxZ1, x means the atomic ratio of Ti/Zr = 10, 5, 1, 0.2 and 0.1) composite oxide supports were prepared through co-precipitation, and then 3 wt% Co was loaded through wetness impregnation methods. The obtained 3 wt% Co/TiO2 (3CT), 3 wt% Co/ZrO2 (3CZ) and 3 wt% Co/TxZ1 (3CTxZ1) catalysts were evaluated for the oxidative ethane dehydrogenation reaction with CO2 (CO2-ODHE) as a soft oxidant. 3CT1Z1 catalyst exhibits excellent catalytic properties, with C2H4 yield, C2H6 conversion and CO2 conversion about 24.5 %, 33.8 % and 18.0 % at 650 °C, respectively. X-Ray Diffraction (XRD), in-situ Raman, UV–vis diffuse reflectance spectra (UV–vis DRS), H2 temperature-programmed reduction (H2-TPR), Electron paramagnetic resonance (EPR) and quasi in-situ X-ray Photoelectron Spectroscopy (XPS) have been utilized to thoroughly characterize the investigated catalysts. The results revealed that 3CT1Z1 produced TiZrO4 solid solution with more metal defect sites and oxygen vacancies (Ov), promoting the formation of Co2+-TiZrO4 structure. Furthermore, the presence of Ov and Ti3+can facilitate the high dispersion and stabilization of Co2+, as well as suppressing the severe reduction of Co2+, leading to superior ethane oxidative dehydrogenation activity. Besides, less Co0 is beneficial to ODHE reaction, because of its promotion effects for reverse water gas shift reaction; however, more Co0 results in dry reforming reaction (DRE). This work will shed new lights for the design and preparation of highly efficient catalysts for ethylene production.

Unravelling the role of boron dopant in borocarbonitirde catalytic dehydrogenation reaction

Borocarbonitride (BCN) materials are newly developed metal-free catalytic materials exhibiting high selectivity in oxidative dehydrogenation (ODH) of alkanes. However, the in-depth understandings on the role of boron (B) dopants and the intrinsic activities of –C=O and –B–OH still remain unknown. Herein, we report a series of BCN materials with regulable B content and surface oxygen functional groups via self-assembly and pyrolysis of guanine and boric acid. We found that the B/C ratio is the key parameter to determine the activity of ODH and product distribution. Among them, the high ethylbenzene conversion (∼57%) and styrene selectivity (∼83%) are achieved in ODH for B1CN. The styrene selectivity can be improved by increasing of B/C ratio and this value reaches near 100% for B5CN. Structural characterizations and kinetic measurements indicate that –C=O and –B–OH dual sites on BCN are real active sites of ODH reaction. The intrinsic activity of –C=O (5.556 × 10−4 s−1) is found to be 23.7 times higher than –B–OH (0.234 × 10−4 s−1) site. More importantly, we reveal that the deep oxidation to undesirable CO2 occurs on –C=O rather than –B–OH site, and B dopant in BCN materials can reduce the nucleophilicity of –C=O site to eliminate the CO2 emission. Overall, the present work provides a new insight on the structure–function relationship of the BCN catalytic systems.

Crucial role of H and O spillover in VOx/CeO2 catalysts reduction and re-oxidation during the ODH reaction

Ceria-supported monomeric vanadia (VOx/CeO2) catalysts show outstanding activity in oxidative dehydrogenation (ODH) in the CO2 atmosphere. This work reports the density functional theory calculations exploring the reduction and reoxidation mechanisms in the Mars-van-Krevelen cycle for the ODH over VOx/CeO2(111). Intriguingly, a new phenomenon was observed in the reduction of VO2/CeO2(111), the H species generated by CH bond activation on the VOx cluster could spill over to CeO2 with a minimum barrier, enabling the reduction to occur at CeO2 substrate. Subsequently, the formed H2O releases and causes a structure evolution, resulting in VO2/CeO2(111) reduction to VO/CeO2(111). However, this H spillover is hard to be detected at the interface of VO/CeO2(111), VOx/TiO2(101), and VOx/α-Al2O3(001) due to a higher barrier, indicating that the H spillover is related to the electron acceptability of substrate and the structure of VOx cluster. Moreover, O spillover from CeO2 is noticed at the interface of VOx/CeO2(111) in the reoxidation process, causing the V oxidation to VO. However, VO reoxidation to VO2 is thermodynamically and dynamically unfavorable. Therefore, the structure VO/CeO2(111) seems to be conserved in the steady-state reaction process. This paper would provide key insights for understanding the structure evolution of catalyst in the ODH.

Origin of the Activity Trend in the Oxidative Dehydrogenation of Ethanol over VOx/CeO2**

AbstractSupported vanadia (VOx) is a versatile catalyst for various redox processes where ceria‐supported VOx have shown to be particularly active in the oxidative dehydrogenation (ODH) of alcohols. In this work, we clarify the origin of the volcano‐shaped ethanol ODH activity trend for VOx/CeOx catalysts using operando quick V K‐ and Ce L3‐ edge XAS experiments performed under transient conditions. We quantitatively demonstrate that both vanadium and cerium are synergistically involved in alcohol ODH. The concentration of reversible Ce4+/Ce3+ species was identified as the main descriptor of the alcohol ODH activity. The activity drop in the volcano plot, observed at above ca. 3 V nm−2 surface loading (ca. 30 % of VOx monolayer coverage), is related to the formation of spectator V4+ and Ce3+ species, which were identified here for the first time. These results might prove to be helpful for the rational optimization of VOx/CeO2 catalysts and the refinement of the theoretical models.

Origin of the Activity Trend in the Oxidative Dehydrogenation of Ethanol over VOx /CeO2.

Supported vanadia (VOx ) is a versatile catalyst for various redox processes where ceria-supported VOx have shown to be particularly active in the oxidative dehydrogenation (ODH) of alcohols. In this work, we clarify the origin of the volcano-shaped ethanol ODH activity trend for VOx /CeOx catalysts using operando quick V K- and Ce L3 - edge XAS experiments performed under transient conditions. We quantitatively demonstrate that both vanadium and cerium are synergistically involved in alcohol ODH. The concentration of reversible Ce4+ /Ce3+ species was identified as the main descriptor of the alcohol ODH activity. The activity drop in the volcano plot, observed at above ca. 3 V nm-2 surface loading (ca. 30 % of VOx monolayer coverage), is related to the formation of spectator V4+ and Ce3+ species, which were identified here for the first time. These results might prove to be helpful for the rational optimization of VOx /CeO2 catalysts and the refinement of the theoretical models.

Engineering Specific Mo–O Bond Stretching to Activate Lattice Oxygen in V-Doped Bi2MoO6 for Enhanced Oxidative Dehydrogenation of 1-Butene

Structural distortion has been demonstrated to regulate lattice oxygen activity, but its precise regulation has always been a thorny problem, especially for the oxidative dehydrogenation of hydrocarbons. Herein, by synthesizing a series of V-doped Bi2MoO6 catalysts, mechanistic insight into the effect of structural distortion on the catalytic activity of oxidative dehydrogenation of 1-butene was provided. Comprehensive characterizations and kinetics tests revealed that the V-doped Bi2MoO6-induced active lattice oxygen initiates 1-butene activation by abstracting the C–H bond, which is a rate-determining step. Combined with density functional theory results, an overwhelming effect of the bond length between Mo and apical oxygen atom in the MoO6 octahedron on lattice oxygen activation and butadiene formation pathway was proposed. The stretching Mo–Oapical bond elicited by V doping enhances the abstraction of hydrogen and accelerates the redox cycle. The sample with a 5% V content possesses the maximum Mo–Oapical bond length, enabling superior catalytic performance at an 87.6% 1,3-butadiene yield.

Active Ni and Fe species on catalysts Ni/Al2O3 and NiFe/Al2O3 for the oxidative dehydrogenation (ODH) of ethane to ethylene assisted by CO2

Ni/Al2O3 and NiFe/Al2O3 catalysts were synthesized by incipient wetness impregnation and tested for oxidative dehydrogenation (ODH) of ethane to ethylene. The effect of Ni loading and Fe as a promoter for bimetallic catalysts were characterized by X-ray diffraction (XRD), Raman spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy (UV-vis DRS), scanning electron microscopy (SEM), and temperature-programmed reduction (H2-TPR). The catalyst with 10 wt% Ni and 6.6 wt% Fe (NiFe32) displayed the highest ODH activity. XRD results showed smaller crystalline NiO (˂ 7 nm) for bimetallic catalysts than the monometallic ones. Raman results depicted NiOx species in the monometallic catalysts. The bimetallic catalysts exhibited spinel-type structures as NiFe2O4 and FeAl2O4 related to more active species in ODH of ethane. DRS results revealed that the higher ODH activity for bimetallic catalysts is related to a predominance of Ni and Fe in tetrahedral symmetry (Td) than octahedral symmetry (Oh). These suggest that tetrahedral symmetry species were more effective than octahedral symmetry. TPR profiles showed that the iron addition increased the nickel species with strong interaction with the support. This rearrangement of Ni and Fe species in octahedral and tetrahedral sites of the NiO and alumina lattice could explain the shift reduction temperatures for Ni species and the formation of the spinel-type structure in the bimetallic catalysts. A relation between the metal-support interaction and the selectivity toward ethylene was found. A higher strong metal-support interaction favors a better catalytic activity.

Investigation of Phosphorus Loaded V2O5/ZrO2 Catalysts for the Oxidative Dehydrogenation of Propane (ODH)

In this study, V2O5/ZrO2 samples loaded with different wt% of V2O5, ranging between 0% and 20% (wt% = 2.5, 3.6, 7.5, 10, and 20), were prepared and studied in the dehydrogenation of 2-butanol in order to investigate their acid-basic properties and to select the most interesting sample, that was identified in the 3.6 wt%V2O5/ZrO2. Such a catalyst was modified by adding phosphate at different atomic ratios (P/V = 0.5, 1, and 2) and further characterized by XRD, SEM-EDX, ESR, UV-Vis-PIR diffuse reflectance. Tests of catalytic dehydrogenation of 2-butanol were also performed. Then, the so-prepared samples were investigated in the oxidative dehydrogenation (ODH) of propane that represents the reaction of main interest in this study. It has been shown that the introduction of 3.6 wt%V2O5 and phosphate in the zirconia matrix enhances the stability of the tetragonal structure, improves acidity, and promotes ODH activity. Compared to the unpromoted 3.6 wt%V2O5/ZrO2 catalyst, the addition of phosphate increases the overall propane conversion from 12% to 20%, and also the propylene selectivity from 54% to near 64%, in the experimental conditions F °C3H8/F°O2/F°total (cm3/min): 3.6/1.8/60 at the temperature of 500 °C. The influence of the reaction mixture on the ODH, in particular the oxygen flow rate, was addressed. Highlights: Phosphorus loaded V2O5/ZrO2 catalysts were prepared and investigated in the oxidative dehydrogenation of propane. Addition of V2O5 and phosphorus to ZrO2 stabilized the tetragonal phase with respect to the monoclinic one. Among the prepared V2O5/ZrO2 samples, the most active catalyst corresponds to 3.6 wt% of V2O5/ ZrO2, The addition of phosphorus to 3.6 wt% V2O5/ZrO2 improves acidity and selectivity to propylene. Correlation between catalysts acidity and oxidative dehydrogenation of propane was observed.

Oxidative dehydrogenation of ethane and subsequent CO2 activation on Ce-incorporated FeTiOx metal oxides

• Oxidative dehydrogenation (ODH) with successive CO 2 activation was studied. • Number of lattice oxygen mobility was related with chemical looping (CL)-ODH activity. • Facile redox property of CeFeTiO x was enhanced with new FeTiO 3 phases formation. The Ce-incorporated FeTiO x catalysts were investigated for an oxidative dehydrogenation (ODH) of C 2 H 6 (reduction step) and successive CO 2 activation to CO (oxidation step) through redox chemical looping (CL-ODH) cycles of those partially reducible metal oxides via mutual phase changes between Fe 2+ /Fe 3+ and Ti 3+ /Ti 4+ species. A higher lattice oxygen mobility with less surface electrophilic oxygen natures on an optimal FeCeTiO x (1) (Fe/Ce molar ratio = 1.0) was responsible for an enhanced cyclic stability. The lattice expansion by Ce-incorporation into the Fe/TiO 2 structures not only enhanced charge transport rates but also generated thermally stable trigonal ilmenite FeTiO 3 phases. These larger oxygen storage capacity of CeO 2 on the FeCeTiO x (1) also revealed an excellent 5-times cyclic stability with a stable C 2 H 4 formation rate and C 2 H 4 selectivity of 84.1% for a reduction step of ethane as well as an excellent CO 2 activation to CO at 600 °C for an oxidation step (named as CL-ODH). Those superior catalytic performances on the FeCeTiO x (1) were attributed to the partial formation of FeTiO 3 phases, which caused an improved lattice oxygen mobility by CeO 2 contribution with its higher oxygen storage nature and facile redox property. The large amount of non-stoichiometric surface oxygens at a higher Fe/Ce ratio above 2 mainly caused an enhanced CO 2 byproduct formation by the full oxidation of C 2 H 6 . The synergy effects on the FeCeTiO x (1) were attributed to facile redox properties of lattice oxygen vacant sites by partially forming the strongly interacted stable FeTiO 3 phases with its resistance to coke depositions.

Atomically Precise Single Metal Oxide Cluster Catalyst with Oxygen‐Controlled Activity

AbstractSingle cluster catalysts (SCCs) consisting of atomically precise metal nanoclusters dispersed on supports represent a new frontier of heterogeneous catalysis. However, the ability to synthesize SCCs with high loading and to precisely introduce non‐metal atoms to further tune their catalytic activity and reaction scope of SCCs have been longstanding challenges. Here, a new interface confinement strategy is developed for the synthesis of a high density of atomically precise Ru oxide nanoclusters (Ru3O2) on reduced graphene oxide (rGO), attributed to the suppression of diffusion‐induced metal cluster aggregation. Ru3O2/rGO exhibits a significantly enhanced activity for oxidative dehydrogenation of 1,2,3,4‐tetrahydroquinoline (THQ) to quinoline with a high yield (≈86%) and selectivity (≈99%), superior to Ru and RuO2 nanoparticles, and homogeneous single/multiple‐site Ru catalysts. In addition, Ru3O2/rGO is also capable of efficiently catalyzing more complex oxidative reactions involving three reactants. The theoretical calculations reveal that the presence of two oxygen atoms in the Ru3O2 motif not only leads to a weak hydrogen bonding interaction between the THQ reactant and the active site, but also dramatically depletes the density of states near the Fermi level, which is attributed to the increased positive valence state of Ru and the enhanced oxidative activity of the Ru3O2 cluster for hydrogen abstraction.

A generalized approach to adjust the catalytic activity of borocarbonitride for alkane oxidative dehydrogenation reactions

The borocarbonitrides (BCNs) have exhibited enormous potential as non-metallic catalysts for alkane oxidative dehydrogenation (ODH) reactions. However, the poor electron transportation ability in BCN leads to a low reactivity of oxygen functional groups (CO and BOH). Herein, we present a generalized strategy to promote the catalytic activity of BCN through in situ encapsulation of transition-metal (Fe, Co, Ni) nanoparticles within BCN nanotubes (BCNNTs). Among them, individual metal particles themselves do not contribute directly on ODH reactions and mainly serve as electron modulators to tune the electron density of CO and BOH active sites on BCNNTs. As a result, catalytic activities of all metal@BCNNTs catalysts surpass pure BCN in ethylbenzene (EB) ODH reactions, among which Fe@BCNNTs displays a significant activity enhancement with 36 % EB conversion with the styrene (ST) selectivity remaining >98% under gentle reaction conditions. Structural and kinetic analyses proved that the promotion effect originated from the strong interactions between metal nanoparticles and BCNNTs. The theoretical calculations disclosed that the enhanced ODH activity was due to the electron transfer from the encapsulated metal to BCNNTs, which increases the electron transportation ability and electron density of BCNNTs, thus promoting the nucleophilicity of CO and BOH active sites, leading to the reduced activation energy barrier for CH bond dissociation. The present work sets forth the structure-function relationship, identifying opportunities for rational design of highly efficient BCN catalysts for ODH reactions.

Three-Dimensional Porous Hexagonal Boron Nitride Fibers as Metal-Free Catalysts with Enhanced Catalytic Activity for Oxidative Dehydrogenation of Propane

Boron nitride (BN) as an emerging and revolutionary metal-free catalyst has demonstrated great potential in various oxidative dehydrogenation reactions. However, traditional BN sheets always presen...

Ce-modified SrFeO3-δ for ethane oxidative dehydrogenation coupled with CO2 splitting via a chemical looping scheme

The current study investigates Ce-modified SrFeO3-δ oxygen carriers for oxidative dehydrogenation (ODH) of ethane coupled with CO2 splitting in a chemical looping manner. During 39 cycles of redox testing over the sample of 0.2Ce/SrFeO3, up to 29% ethane conversion and 82% ethylene selectivity are achieved, and the CO generation in the subsequent CO2 splitting step is 0.25 mmol/g. XPS characterization results indicate decreased Fe2+/(Fe3++Fe4+) ratio as well as increased active oxygen species proportion on the near-surface of Ce-modified samples, which are responsible for the improved activity of the 0.2Ce/SrFeO3 in ethane ODH reaction. DFT calculations further reveal that the increased ODH activity of 0.2Ce/SrFeO3 is due to the lower surface oxygen vacancy formation energy upon Ce promotion. Moreover, the higher resistance of lattice oxygen diffusion from the bulk to the surface is the main reason for the superior ethylene selectivity attained by the CO2-regenerated sample than that by O2 regeneration.

New Multicomponent MoVSbNbCeOx/SiO2 Catalyst with Enhanced Catalytic Activity for Oxidative Dehydrogenation of Ethane to Ethylene

AbstractIn our study, we have obtained a multicomponent MoVSbNbCeOx/SiO2 catalyst with high catalytic activity for oxidative dehydrogenation of ethane (ODE) to ethylene. To date, multicomponent MoVTe(Sb)NbOx catalysts, which have been intensively studied during the last years, were found as very promising for the ODE to produce ethylene. It was generally agreed that the MoVTeNbOx catalyst was more efficient than MoVSbNbOx. The major drawback of using Te‐containing catalysts is the presence of environmentally harmful, toxic tellurium, and its volatility during the catalyst preparation and catalytic reaction conditions. In our work, the Mo1V0.24Sb0.23Nb0.08Ce0.01Ox/50 wt. % SiO2 catalyst was prepared via the spray‐dry method of aqueous solutions of the starting components, followed by heat‐treatment in He at 350 and 600 °C. For comparative purpose, one of the best Te‐containing catalysts Mo1V0.3Te0.23Nb0.12Ox was also tested in this reaction under the similar reaction conditions. A comparison of the catalytic properties of Sb− and Te− containing catalysts at the reaction temperature of 400–450 °C illustrates for both catalysts relatively high catalytic properties for ODE. The yield of ethylene of ca. 74 % was obtained for these catalysts, which exceeds the best yield reported in literature for Sb‐containing catalysts. The two main phases – M1 and M2 were revealed by XRD in the Sb‐containing catalyst. Intergrowth between the crystals of M1 and M2 phases with the formation of the interphase boundary in the highly active and selective Sb‐containing catalyst can be proposed from HRTEM results. The nature of the active state in this catalyst is discussed.

Oxidative dehydrogenation of propane using layered borosilicate zeolite as the active and selective catalyst

Oxidative dehydrogenation (ODH) of propane to propylene offers a promising large-scale alternative to direct dehydrogenation. The reported metal oxides catalysts generally cause over-oxidation of propylene to COx, thus hindering the commercialization of ODH processes. In this study, a layered borosilicate zeolite was demonstrated as highly active and selective catalyst for the oxidative dehydrogenation of propane, showing a propylene selectivity of 83.6% and the total light olefins (propylene and ethylene) selectivity of 91.2% at a propane conversion of 3.9%. Further, at a propane conversion of 15.6%, the catalyst exhibited a propylene selectivity of 80.4% and the total light olefins selectivity of 91.6% at 530 °C. Structural characterization revealed that the abundance of defective trigonal boron species (B[3]a and B[3]b) was responsible for the activity of propane ODH.

B‐MWW Zeolite: The Case Against Single‐Site Catalysis

AbstractBoron‐containing materials have recently been identified as highly selective catalysts for the oxidative dehydrogenation (ODH) of alkanes to olefins. It has previously been demonstrated by several spectroscopic characterization techniques that the surface of these boron‐containing ODH catalysts oxidize and hydrolyze under reaction conditions, forming an amorphous B2(OH)xO(3−x/2) (x=0–6) layer. Yet, the precise nature of the active site(s) remains elusive. In this Communication, we provide a detailed characterization of zeolite MCM‐22 isomorphously substituted with boron (B‐MWW). Using 11B solid‐state NMR spectroscopy, we show that the majority of boron species in B‐MWW exist as isolated BO3 units, fully incorporated into the zeolite framework. However, this material shows no catalytic activity for ODH of propane to propene. The catalytic inactivity of B‐MWW for ODH of propane falsifies the hypothesis that site‐isolated BO3 units are the active site in boron‐based catalysts. This observation is at odds with other traditionally studied catalysts like vanadium‐based catalysts and provides an important piece of the mechanistic puzzle.

On mechanism of formation of SBA-15/furfuryl alcohol-derived mesoporous carbon replicas and its relationship with catalytic activity in oxidative dehydrogenation of ethylbenzene

Abstract A series of CMK-3-like carbon replicas was synthesized by precipitation polycondensation of furfuryl alcohol in an aqueous slurry of SBA-15 at a polymer/SiO2 mass ratio of 0.50–2.00. Changes in textural and structural parameters of SBA-15 after polymer deposition were studied by N2 adsorption and X-ray diffraction. Morphology of the replicas was investigated by transmission electron microscopy, while their surface composition was determined by temperature-programmed desorption and X-ray photoelectron spectroscopy. The mechanism of deposition of poly(furfuryl alcohol) (PFA) onto silica surface was elucidated. It was found that PFA accumulates in SBA-15 pores randomly; certain channels are completely filled, while others remain partially empty. The incomplete filling of mesopores results in “pseudo-CMK-3” structures featuring the bimodal porosity (the typical mesopores of CMK-3 are accompanied by broader ones formed by the coalescence of adjacent partially hollow pores). The total filling of pores with PFA leads to the formation of good-quality CMK-3. The carbon replicas exhibited the presence of abundant amounts of superficial oxygen-containing moieties. These entities are responsible for high activity of the materials in the oxidative dehydrogenation (ODH) of ethylbenzene, bringing evidence supporting the mechanism of active coke, considered as governing the catalytic performance of carbon materials in ODH of alkanes.

Oxidative dehydrogenation of propane on silica-supported vanadyl sites promoted with sodium metavanadate

[VO4]/SiO2 promoted with NaVO3 polymorphs (α or β) shows higher initial activity in oxidative dehydrogenation of propane (increase by 30 and 125%, respectively) compared to that of unpromoted [VO4]/SiO2 at similar vanadium loadings.