Dispersed Vanadium in Three-Dimensional Dendritic Mesoporous Silica Nanospheres: Active and Stable Catalysts for the Oxidative Dehydrogenation of Propane in the Presence of CO₂

Abstract

The uniform monodispersed vanadium-doped three-dimensional dendritic mesoporous silica nanospheres (nV-MSNSs) were successfully synthesized in a heterogeneous oil-water biphase stratification reaction system and characterized by several state-of-the-art methods. The synthesized nV-MSNSs were applied to the oxidative dehydrogenation of the propane (ODHP) reaction with the presence of CO and exhibited excellent catalytic performances. The results show that the vanadium loading (1.3-8.0 wt %) evidently influences the textural properties, oxidation state, and polymerization degree of vanadium species of nV-MSNSs. The specific surface area (S), pore diameter (D), and pore volume (V) of nV-MSNSs decrease with the loading of vanadium species. The excessively high vanadium loading leads to the slight connection of nanospheres, but does not affect the assembly and growth of the three-dimensional (3D) dendritic channels. The percentage of highly dispersed vanadium V species gradually increases and attains the maximum value for 5.2V-MSNSs with the loading of vanadium and then decreases with further vanadium addition. The higher-polymerized VO species gradually generates above 5.2 wt % vanadium content for nV-MSNSs. The lower-polymerized VO species appear to be more active than the higher-polymerized VO species. Markedly, the 5.2V-MSNSs exhibit the highest catalytic activity with the initial propane conversion of 58% for the ODHP. The excellent catalytic performance can be maintained after eight reaction-regeneration cycles. The silica mesoporous frameworks can be well preserved in the reaction-regeneration cycles; meanwhile, the highly dispersed vanadium oxide also can be fully recovered after in situ regeneration. Hence, nV-MSNS catalysts exhibit outstanding activity and stability, and it would have a promising application in the DH of alkanes.

Insights into Redox Dynamics of Vanadium Species Impregnated in Layered Siliceous Zeolitic Structures during Methanol Oxidation Reactions

“…During reaction steps using the [5 V]Si‐ITQ‐6 catalyst a very fast activation of O 2 and regeneration of reduced sites occurs, since no contribution of V 4+ species were observed in the total spectra. By monitoring the gases exiting the XANES cell during the reaction steps (Figure S13), formaldehyde and carbon monoxide were identified as major products, with small amounts of dimethyl ether, due to the low acidity present in the vanadium sites . Under the oxidizing atmosphere, formaldehyde formation is predominant in relation to carbon monoxide.…”

“…By monitoring the gases exiting the XANES cell during the reaction steps ( Figure S13), formaldehyde and carbon monoxide were identified as major products, with small amounts of dimethyl ether, due to the low acidity present in the vanadium sites. [53][54][55] Under the oxidizing atmosphere, formaldehyde formation is predominant in relation to carbon monoxide. This is explained by the use of a limited O 2 /CH 3 OH ratio (0.71), since oxidation to CO and CO 2 are favored in oxygen rich conditions (Table S4).…”

VOx/γ‐Al2O3 Catalysts for Propane Dehydrogenation Prepared by “Impregnation‐Solid Phase Reaction” Method with Aluminum Hydroxide as Support Precursor

“…The decrease of the percentage of water can be attributed to that the introduced VO X species decreased the OH groups bonded to Al 2 O 3 . Meanwhile, NH3 can be adsorbed by the introduced VO X species and desorbed at 150–350 ° C . Rodemerck et al.…”

Effect of dealumination on the catalytic performance of Cr-containing Beta zeolite in carbon dioxide assisted propane dehydrogenation

“…Many different catalysts were investigated in CO 2 -PDH containing Pt [3], Ni-Fe [4] Cr [5][6][7][8][9][10][11][12][13][14][15][16], Ga [17][18][19][20], In-Al [21][22][23], Fe [24] or V [25,26]. Among them, the chromium oxide-based materials are considered as a very promising for CO 2 -PDH due to high activity and selectivity.…”