Interplay of On- and Off-Surface Processes in the B₂O₃-Catalyzed Oxidative Dehydrogenation of Propane: A DFT Study

Abstract

Metal-free boron-based catalytic systems are growing to be promising choices in the oxidative dehydrogenation (ODH) of light alkanes to olefins. However, the ambiguity in the understanding of the mechanism has impeded the improvement of novel catalytic systems. Herein, by using density functional theory (DFT), we mapped a complex reaction network for the B 2 O 3catalyzed ODH of propane, which displayed a typical feature of interplay between the on-surface and off-surface channels through the whole reaction from the initiation stage to the termination stage. The results showed that the interplay between the channels in the two regimes was necessary in two aspects: On one hand, to guarantee high selectivity for olefin products, the gaseous channels need the intervention of the surface sites to eliminate the oxygenated intermediates, for example, alkoxyl radicals, that would otherwise evolve into deep oxidation products. On the other hand, to maintain the high conversion of propane, the catalyst surface needs gaseous radicals to regenerate reactive >BO• species. The mechanism also well explained the catalytic role of trace water and addressed the surface dynamical restructuring, thus constituting a plausible comprehensive understanding of the ODH of propane catalyzed by an oxygenated boron system.

Promoting Catalytic Activity of Boron by Phosphor in Propane Oxidative Dehydrogenation

“…The nascent • C 3 H 7 species, with the assistance of gaseous oxygenated radical, such as • OH and • OOH, could further undergo DH to form C 3 H 6 . A previous study has shown that the gaseous channel cannot be ignored in the formation of propylene from • C 3 H 7 species, and the detailed processes have been addressed …”

“…The use of employed methodology have been qualified and the influence of diffuse function, basis set, and dispersion correction for similar B-containing catalysts h-BN and B 2 O 3 are evaluated in our previous work. 32,33 Vibrational frequency calculations 34 are conducted to identify the stationary points as minimum energy structures or transition states at the same level of the theory. Intrinsic reaction coordinate (IRC) has been investigated to verify that each transition state can connect two minima along the reaction pathway.…”

“…All stationary points are obtained at the B3LYP-D3/6-31+G­(d,p) level of theory (with the default D3 dispersion correction proposed by Grimme). − The default convergence criteria have been used during the geometrical optimization. The use of employed methodology have been qualified and the influence of diffuse function, basis set, and dispersion correction for similar B-containing catalysts h-BN and B 2 O 3 are evaluated in our previous work. , Vibrational frequency calculations are conducted to identify the stationary points as minimum energy structures or transition states at the same level of the theory. Intrinsic reaction coordinate (IRC) has been investigated to verify that each transition state can connect two minima along the reaction pathway. , The single-point energies for all stationary points were calculated at the B3LYP-D3/6-311++G­(2df,2pd) level of theory.…”

“…The high reaction barriers implicate that an induction period may exist in the BPcatalyzed ODHP reaction, similar to the reactions in other boron-based catalytic systems. 21,32,33,43,44 These data also suggest that transition states H-TS1-1 and H-TS1-2 (catalyzed by BP-H) are more stabilized than L-TS1-1 and L-TS1-2 (catalyzed by BP-L) by 9.2 and 6.6 kcal/mol, respectively, indicating that it is easier to generate active >B−O • species on the BP-H catalyst than that on BP-L during the DH reaction.…”

The Journal of Physical Chemistry C Virtual Special Issue on “Energy and Catalysis in China”

“…CO oxidation on RuO 2 (110) surfaces, 85 Pt nanocatalysts, 86 Cu/Rh bimetallic catalysts, 87 Ag clusters, 88 and Ru/RuO 2 interfaces 89 is discussed. Theoretical studies on other important reactions are also included: the HER on the VS 2 monolayer 90 or black phosphorus, 91 the electrochemical CO 2 reduction reaction on h-BN nanosheets, 92 photocatalytic CO 2 reduction on silver nanoclusters, 93 CO 2 dissociation on Cu clusters, 94 the methanol-to-olefins (MTO) process on different zeolites, 95 the ORR on the two-dimensional NiTe monolayer, 96 the nitrogen reduction reaction on Ru-or Fe-supported Nb 2 C MXene, 97 NO reduction by CO on Cu 2 O(110) and Pd 1 / Cu 2 O(110), 98 NO oxidation on different oxides, 99 methane steam reforming on Ni, Pt, and Pd, 100 dry reforming of methane on the Ni/Mo alloy, 101 the B 2 O 3 -catalyzed oxidative dehydrogenation of propane, 102 the hydrodeoxygenation of hydroquinone on Au/TiO 2 , 103 the hydrogenation of CO 2 to methanol over Pt 4 /In 2 O 3 , 104 syngas conversion to ketene on ZnCr 2 O 4 , 105 the structural and optoelectronic properties of ZnSe 1−x Te x photocatalysts, 106 bimetallic salen-complex-catalyzed epoxide hydration, 107 Rh-catalyzed formaldehyde hydroformylation, 108 the peroxidase and oxidase-like properties of nanoceria in biosystems, 109 the formation of polarons in TiO 2 , HfO 2 , and BiVO 4 , 110,111 and interfacial charge transfer in Li− O 2 batteries. 112 This VSI reflects the recent progress in the experimental and theoretical development of chemical energy in mainland China.…”