Carbon Nanofibers Modified with Heteroatoms as Metal‐Free Catalysts for the Oxidative Dehydrogenation of Propane

Abstract

Carbon nanofibres (CNFs) were modified with B and P by an ex situ approach. In addition, CNFs doped with N were prepared in situ using ethylenediamine as the N and C source. After calcination, the doped CNFs were used as catalysts for the oxidative dehydrogenation of propane. For B-CNFs, the effects of boron loading and calcination temperature on B speciation and catalytic conversion were studied. For the same reaction temperatures and conversions, B- and P-doped CNFs exhibited higher selectivities to propene than pristine CNFs. The N-CNFs were the most active but the least selective of the catalysts tested here. Our results also show that the type of P precursor affects the selectivity to propene and that CNFs modified using triphenylphosphine as the precursor provided the highest selectivity at isoconversion.

Direct Insight into Ethane Oxidative Dehydrogenation over Boron Nitrides

“…Chemical changes in the s ‐BN catalyst, on the other hand, were evident by X‐ray photoelectron spectroscopy (XPS, Figure S7 a–c) and Raman and infrared (IR) spectroscopy (Figure S7 d, e). Interestingly, a B−O signature (at a binding energy of 193 eV in the B 1s spectrum) emerged in the used catalyst (after high X operation), whereas no change in the N 1s feature was observed. Consistently, the vibrational features found by Raman ( =882 cm −1 , B−O from H 3 BO 3 ) and IR ( =1217 cm −1 for B−O and =3231 cm −1 for O−H) spectroscopy suggested the presence of B−O species without any clear change in the N‐related vibrations.…”

“…Chemical changes in the s-BN catalyst, on the other hand, were evident by X-ray photoelectron spectroscopy (XPS, Figure S7 a-c) and Raman and infrared (IR) spectroscopy ( Figure S7 d, e). Interestingly,aB ÀOs ignature (at ab inding energy of 193 eV in the B1ss pectrum) [13] emerged in the used catalyst (after high X C 2 H 6 operation), whereas no change in the N1sf eature waso bserved.C onsistently,t he vibrational features found by Raman (ñ = 882 cm À1 , BÀOf rom H 3 BO 3 ) [14] and IR (ñ = 1217 cm À1 for BÀOa nd ñ = 3231 cm À1 for OÀH) [15] spectroscopy suggested the presence of BÀOs peciesw ithout any clear change in the N-related vibrations. Given that the active sites are likely located at the edges of the s-BNn anosheets, these results indicate that the edge B atoms must be involved in O 2 activation.Operando diffuse reflectance infrared Fourier-transform (DRIFT) spectroscopyc oupled with on-line gas chromatography (GC) for simultaneous monitoring of the catalyst and the ODH reactionw as conducted to understand the reaction process better.D ynamic evolution of the s-BN catalyst under aerobic and anaerobic conditions was investigated by switching the feed gas from Ar to C 2 H 6 /Ar (step 1), O 2 /Ar (step 2), C 2 H 6 /Ar (step 3), and finally C 2 H 6 /O 2 (step 4).…”

Facile simultaneous defect production and O,N-doping of carbon nanotubes with unexpected catalytic performance for clean and energy-saving production of styrene

“…This approach presents a facile strategy for producing surface defects and O,N-doping of carbon nanotubes simultaneously through the explosive decomposition of melamine nitrate. However, current efforts have been mainly focused on carbon catalyzed oxidative dehydrogenation, [14][15][16][17][18][19][20][21][22][23][24][25] and so far, reports on oxygen-and steam-free DDH are rare. Direct dehydrogenation (DDH) of ethylbenzene has attracted considerable attention owing to the growing demand for styrene in the chemical industry.…”

Modulating the microstructure and surface chemistry of carbocatalysts for oxidative and direct dehydrogenation: A review

“…The introduction of electron-rich heteroatoms can adjust the electronic properties of oxygen functionalities and also modulate the defectiveness, which significantly affects the activity, selectivity (over-oxidation) and stability (combustion of carbocatalysts). Through oxidative treatment and heteroatom-doping, the surface chemical properties of carbon materials including surface elemental component and state can be directly or indirectly regulated, which in turn adjusts their catalytic performance in the ODH reaction [138][139][140][141][142][143][144][145][146].…”

“…Doping by heteroatoms is also an efficient approach for regulating the surface chemistry of carbocatalysts. The effect of N, P, and B doping on the surface chemical properties and catalytic performance in ODH has been investigated [46,59,63,66,80,[144][145][146]. Chen et al [59] found that graphitic nitrogen has a determining effect on enhancing the catalytic performance of CNTs in the ODH reaction through reducing the activation energy by speeding up dissociative adsorption and activation of molecular oxygen.…”