Role of Lattice Oxygen of Metal Oxides in the Dehydrogenation of Ethylbenzene under a Carbon Dioxide Atmosphere

Abstract

The mechanism for the dehydrogenation of ethylbenzene over V, Cr, and Fe oxides loaded on activated carbon, powdered diamond, Al(2)O(3), and MgO was studied in the presence of CO(2). Vanadium oxide-loaded catalysts provided higher styrene yields under CO(2) than Ar flow. The transient response method was carried out to understand the reaction behaviors of lattice oxygen of various metal oxides on the support. The results showed that lattice oxygen of vanadium oxide (V=O) was consumed in the dehydrogenation reaction and that reduced vanadium oxide was reoxidized with CO(2). A similar redox cycle was observed on iron oxide-loaded activated carbon catalyst. Spectroscopic characterization revealed that vanadium oxide and iron oxide on the support were reduced to a low valence state during the dehydrogenation reaction, and that CO(2) could oxidize the reduced metal oxides. In contrast, chromium(III) oxide was not reduced during dehydrogenation. From these findings, the redox cycle over vanadium oxide- and iron oxide-loaded catalysts was concluded to be an important factor in promoting the catalytic activity with CO(2).

Preparation of Isolated VO₄³⁻ Species in Silica Framework by Alkoxy-exchange Reactions between Metal Alkoxides and Polyethylene Glycol

“…29 Si spectra were recorded at 79.4 MHz with a pulse width of 7.0 μs using 32768 scans. 13 C NMR spectra were recorded at 100.5 MHz with a pulse width of 5.5 μs using 2048 scans.…”

“…at atmospheric pressure containing 50 mg of catalyst. Details of the reaction procedure and analyses were reported previously 29) .…”

“…With higher VOx loading, peak areas increased together with a shift to higher reduction temperatures. Figure 8 shows the 29 Si cross polarization magic angle spinning (CP-MAS) NMR spectra of the asprepared gel from V(OR), TEOS, and PEG25, and its calcined sample (V(1.0) _ PEG25). The as-prepared gel exhibited resonances at 83, 90, and 98 ppm that are attributable to Si(OEt)2(PEG25)2, Si(OEt)(PEG25)3, and Si(PEG25)4 with an intensity ratio of 25 : 52 : 23, respectively.…”

“…The present study investigated the formation process of the gel during the alkoxy-exchange reaction between PEG and metal alkoxides. The gels and calcined products were characterized by various analyses, such as N2 adsorption-desorption isotherm, XRD, Raman, FT-IR, H2-TPR, 13 C, and 29 Si CP-MAS NMR spectroscopies. The obtained material was assessed as a catalyst for the oxidative dehydrogenation of ethylbenzene (EB) using CO2 as a mild oxidant 27) , which found good performance for ODH of EB.…”

Use of Trickle Bed Reactor for Fischer-Tropsch Reaction over Co–Mn/Oxidized Diamond Catalyst

“…In a series of the development of catalysts and catalytic reactions such as dehydrogenation of alkanes 18) or ethylbenzene 19) , selective oxidation of methane 20) and ethane 21) to aldehydes, and carbon nanotube formation 22) were successfully carried out using a new type of carbon-based support material, oxidized powdered diamond (O-Dia) and the results are summarized in a review article 23) . All these reactions are performed under oxidative conditions.…”