Effect of CO₂ Co-Feeding on the Stabilization of Atomically Dispersed Iron Species over MgAl₂O₄ During Ethane Dehydrogenation Reactions

Abstract

Ethane dehydrogenation provides an opportunity for the effective utilization of shale gas and production of ethene. Up to now, it is still a great challenge to acquire a stable ethane dehydrogenation catalyst operated under high temperature and reductive atmospheres. In this study, we prepared an Fe-based catalyst supported on MgAl 2 O 4 with atomically dispersed iron species even after 6 reaction−regeneration cycles. Sheet-like morphology and spinel structure of MgAl 2 O 4 is beneficial for the high dispersion of Fe species. The iron species undergoes reduction, sintering, and detachment during the ethane dehydrogenation reaction, as evidenced by in situ High-Angle Annular Dark-Field Scanning Transmission Electron Microscopy and quasiin situ 57 Fe Mossbauer spectroscopy. By contrast, the introduction of CO 2 leads to a slow deactivation, where only the partial reduction of isolated Fe 3+ species to isolated Fe 2+ species was observed. And the activity could be restored by a simple O 2 treatment. The current work sheds light on the design of high-efficient dehydrogenation catalysts.

Evolution of Co Species in CO2-Assisted Ethane Dehydrogenation: Competing Cleavage of C–H and C–C Bonds

“…The coke species could hardly be removed, which resulted in the passivation of those Co 0 species. According to our previous work, the generated coke species cannot be removed by CO 2 treatment under reaction conditions, hence, the dry-reforming active sites cannot be regenerated and the dehydrogenation reaction dominated when the feeding CO 2 /C 2 H 6 ratio was recovered to 4.0. Another experiment using a feeding CO 2 /C 2 H 6 ratio of 1.0 at the initial stage was performed and the catalytic performance is shown in Figure b.…”

“…11,14,16,23,33 Our previous studies found that co-feeding CO 2 can stabilize isolated Fe 3+ species over MgAl 2 O 4 and suppress the overreduction of FeO x over zeolite during alkane dehydrogenation reactions, leading to more stable catalytic performance compared with direct dehydrogenation reactions. 34,35 Xie et al indicated the dominative effect of CO 2 to prevent the reduction of active species (like Cr 3+ to Cr 2+ ) rather than eliminate coke deposition. 36 Liu et al discovered introducing CO 2 can suppress the formation of unfavorable Ga δ+ -H x species that resulted into a much stable propane dehydrogenation reaction.…”

Rational Design of Catalysts with Spinel Nanostructures for Thermal-Driven C1 Conversion

“…For another irreducible type of catalysts (such as Ga- and In-based oxides), there may exist two tandem steps, direct dehydrogenation and RWGS, during the reaction . The introduction of CO 2 in dehydrogenation systems could promote reactions by consumption of H 2 along with an improvement of stability through removing coke via the Boudouard reaction and keeping metal in optimal oxidation states. , …”

Tuning Pt Location and Intimacy between Pt–Acid Active Sites in Pt/ZSM-5 Bifunctional Catalysts for Effective Alkylation of Benzene with Ethane

“…The rational design of bifunctional catalysts is crucial to their catalytic performance in a targeted reaction. With dual metal and support active sites, it is usually possible to achieve synergistic catalysis by adjusting the metal, − the support, and the interaction between the metal and the support. − In the application of Pt/ZSM-5 in the alkylation of benzene with ethane, much work has been done in optimizing the morphology and acid property of the zeolite support. However, in-depth research on metal active sites is still insufficient.…”