Search

The chemical looping oxidative dehydrogenation (CL‐ODH) of ethane represents a highly effective approach for converting ethane into the value‐added product ethylene. This investigation focused on the synthesis of SrMnO3 and its halide ions doped derivatives (SrMnO3Cl and SrMnO3Br) through the sol‐gel method. The performance of these perovskites, employed as oxygen carriers in CL‐ODH of ethane, was explored. The results unveiled several advantageous outcomes arising from the incorporation of halide ions (Cl− and Br−) with larger radius into the oxygen sites of the SrMnO3 perovskite. Halide ions doping notably induced cell volume expansion and enhanced lattice fringe spacing. Furthermore, it contributed to elevated oxygen vacancy concentration, increased Mn4+/Mn3+ molar ratio, and improved oxygen ions mobility within the bulk lattice. Fixed‐bed experiments demonstrated that these redox catalysts, doped with halide ions, exhibited outstanding activity and stability during cycling tests, exhibiting enhanced both ethylene selectivity and yield in CL‐ODH of ethane. In summary, the introduction of halide ions into SrMnO3 emerges as a promising strategy for enhancing the performance of CL‐ODH in ethane conversion for SrMnO3 based oxygen carriers. © 2023 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Ni‐M‐O catalysts have demonstrated superior performance in the oxidative dehydrogenation of ethane (ODHE), but precise control over the content of active oxygen species is necessary to achieve optimal C2H4 selectivity. In this work, highly efficient Ni‐Al‐O catalysts were prepared by a plasma‐assisted strategy, and their catalytic properties were evaluated for ODHE reaction. Characterization results revealed that the working atmospheres (O2, H2 and Ar) can not only change the crystallite size of NiO, but also modulate the reduction properties of Ni‐Al‐O catalysts and the distribution of active oxygen species. Consequently, Ar and O2 plasma pretreatment increased the ODHE performance by increasing active surface oxygen, while H2 plasma‐treated catalyst showed a decrease in the catalytic performance compared to the original Ni‐Al‐O catalyst. Among them, O2‐Ni‐Al‐O exhibited 50.8 % ethane conversion and 70.3 % ethylene selectivity at 500 °C. It was accepted that the change in the ratio of defective oxygen to lattice oxygen (OV/OL) was the internal reason to illustrate its excellent performance. For series Ni‐Al‐O catalysts, C2H6 conversion increased linearly while C2H4 selectivity decreased with an increase in OV/OL value. [ABSTRACT FROM AUTHOR]

The oxidative dehydrogenation of ethane (ODHE) to ethylene is a process with many advantages (such as energy conservation and coke resistance). Herein, flower‐like Ni−Al−O catalysts with hierarchical structure and high surface areas were fabricated through a hydrothermal route and were applied to ODHE using O2 as oxidant. Compared with NiO alone, the Al3+ insertion into NiO matrix not only increases the C2H4 selectivity by 3–4 times, but also prevents the generation of CO2 and CH4 above 500 °C. At 550 °C, all Ni−Al−O catalysts maintain approximately 50 % ethylene selectivity regardless of Al content. The ethylene yield of 29.5 % with C2H4 selectivity 55.7 % over Ni−Al0.8‐O sample can be reached at 500 °C. Moreover, the Ni−Al0.8‐O catalyst presents a good stability and has no loss of activity after 100 h continuous evaluation. The various characterizations were carried out for investigating the nature of as‐prepared Ni−Al−O catalysts with different Al loadings. Experimental results demonstrate that the addition of Al not only affects the structure and texture properties of NiO, but also impacts the reducibility of Ni species and the amount of active oxygen species. It is found that the Al3+ substitution results in: (1) smaller NiO size; (2) larger specific surface area; (3) weaker reducibility and (4) fewer non‐stoichiometric oxygen species. Therefore, the significant improvement of ethylene selectivity is observed in Ni−Alx‐O catalysts. [ABSTRACT FROM AUTHOR]

An intensification process for the selective oxidation of hydrocarbons integrates a catalytic reactor and an oxygen separation membrane. This work presents the study of oxidative dehydrogenation of ethane at 1123 K in a catalytic membrane reactor based on mixed ionic-electronic conducting (MIEC) membranes. The surface of a membrane made of Ba0.5Sr0.5Co0.8Fe0.2O3− δ has been activated using different porous catalytic layers based on rare earth-doped cerias (fluorite structure) and the porous catalytic coating was deposited by screen printing (coating around 15 μm). The different catalyst formulations were developed by partial substitution of Ce and were synthesized by co-precipitation followed by cobalt impregnation when required. Specifically, seven different catalysts based on the system Ce1− xLn xO2− δ ( x=0.1 or 0.2; Ln=Tb, Pr, Er, Gd, and Tb+Er), including the effect of cobalt addition (2 % molar) in Ce0.8Tb0.2O2− δ, were studied. The ceria catalysts were studied by XRD, SEM, DC-conductivity as a function of oxygen partial pressure, and the high-temperature stability in a CO2 environment was assessed using thermogravimetry. Then, the influence of the ceria catalytic coating on the oxygen permeation flux through the MIEC membrane was studied using argon and methane as the sweep gas in the permeate side. Finally, oxidative dehydrogenation of ethane reaction tests were performed at 1123 K, as a function of the ethane concentration in the feed. The use of a disk-shaped membrane in the reactor made it possible to prevent the direct contact of gaseous oxygen and hydrocarbons and thus to increase the ethylene yield. High ethylene yields (up to ≈84 %) were obtained using a catalytic coating based on 20 % Tb-doped ceria including macropores produced by the addition of graphite platelets in the screen printing ink. The high yields obtained in this kind of catalytic membrane are attributed to the combination of: the high catalytic activity; the control of the oxygen concentration in the gas phase (reaction chamber); and the appropriate fluid dynamics, enabling the fast ethylene evacuation. [ABSTRACT FROM AUTHOR]