Oxidative Dehydrogenation of n-Butane to C4 Olefins Using Lattice Oxygen of VO_x/Ce-meso-Al₂O₃ under Gas-Phase Oxygen-Free Conditions

Abstract

High-performance, fluidizable VO x /Ce-meso-Al 2 O 3 catalysts were prepared by an excessive solvent approach. The prepared catalysts were characterized using various physicochemical techniques in order to secure desired properties. XRD, Raman, and FTIR analyses indicated the presence of amorphous VO x phases on Ce-meso-Al 2 O 3 . Nitrogen adsorption isotherm analysis confirmed a mesoporous framework with a high surface area of the catalysts. H 2 -TPR reduction showed an active and stable behavior of the catalysts in repeated reduction and oxidation cycles. The NH 3 -TPD and NH 3 desorption kinetics analysis revealed that the synthesized catalysts have moderate acidities and low activation energies of NH 3 desorption, suggesting weak metal−support interactions. The VO x /Ce-meso-Al 2 O 3 catalysts were evaluated for n-butane oxidative dehydrogenation (BODH) using a fluidized CREC riser simulator under gas-phase oxygen-free conditions. The reaction time and reaction temperature were varied between 5 and 25 s and 450−575 °C, respectively. It was found that BODH with 0.2 wt % cerium-doped VO x /meso-Al 2 O 3 catalysts gives the highest selectivity (62.3%) of C4 olefins with a conversion of 10.6% at 450 °C and 5 s. Furthermore, the fluidizable VO x /Ce-meso-Al 2 O 3 catalyst showed a stable performance over repeated feed injections followed by catalyst regeneration cycles for BODH.

Effect of Ce Content on the Chemical Looping Oxidative Dehydrogenation of Propane to Propylene over a VOx-CeO2/γ-Al2O3 Oxygen Carrier

“…The diffraction peaks at 2θ = 28.89 • , 32.38 • , and 47.85 • characterize the cubic crystal structure of the CeO 2 phase, indicating that CeO 2 exists in the cubic fluorite phase. The diffraction peaks of VO x species are absent, possibly because these species are highly dispersed on the surface of the γ-Al 2 O 3 carrier, rendering them undetectable by the XRD instruments [16].…”

“…phase. The diffraction peaks of VOx species are absent, possibly because these species are highly dispersed on the surface of the γ-Al2O3 carrier, rendering them undetectable by the XRD instruments [16]. The distributions of the Al, V, O, and Ce elements were investigated through mapping energy spectral analysis.…”

“…Figure 11a XRD patterns of fresh oxygen carriers, Figure 11b XRD patterns of oxygen carriers after 15 cycles of CL-ODHP. No diffraction peaks of VOx species were observed before and after the cycle, and the absence of VOx species peaks could be due to the formation of highly dispersed amorphous VOx phases or the formation of VOx microcrystals undetectable by XRD [16]. The peak intensity of the CeO2 phase of the 10V-3Ce/Al oxygen Figure 11a XRD patterns of fresh oxygen carriers, Figure 11b XRD patterns of oxygen carriers after 15 cycles of CL-ODHP.…”

Advances and future trends in selective oxidation catalysis: a critical review

“…Oxidation of n -butane with 1 mL feed and 1.0 g of 0.2 wt% Ce-doped VO x / meso -Al 2 O 3 catalyst gave the maximum conversion of 10.6% and 62.3% selectivity of C 4 olefins at 450 °C and 5 s reaction time. 18…”

“…Oxidation of n-butane with 1 mL feed and 1.0 g of 0.2 wt% Ce-doped VO x /meso-Al 2 O 3 catalyst gave the maximum conversion of 10.6% and 62.3% selectivity of C 4 olefins at 450 °C and 5 s reaction time. 18 In 2020, Samek et al reported oxidative dehydrogenation of cyclohexane using alumina-supported VO x -CeO 2 materials. Conversion for cyclohexane to cyclohexene and selectivity for cyclohexene, benzene, CO 2 and CO was studied over CeO 2 and VO x /CeO 2 at 450 °C.…”