NiCrOx@silicalite-1 with Advanced CO2Utilization in Oxidative Dehydrogenation of Propane: Insights into Bifunctional Catalysis and Reaction Efficiency

Abstract

CO₂-mediated oxidative dehydrogenation of propane (CO₂-ODHP) has attracted great attention, as it not only efficiently favors propylene production but also provides a promising route for carbon neutralization. The present work has developed a highly efficient CO₂-ODHP catalyst Ni_2.1%Cr_3.6%O_x@S1-1.0 with exceptional C₃H₈ conversion (51.7%), C₃H₆ selectivity (91.4%), long-term stability (passing through a 36 h test), and significantly enhanced CO₂ conversion (21.9% → 52.7%). This can be closely related to the incorporation of Ni into the lattice of CrO_x, forming NiCrO_x, which facilitates the adsorption and activation of CO₂, thereby promoting the timely removal of subtracted H from C₃H₈. Additionally, the evenly dispersed NiCrO_x species encapsulated by silicalite-1 (S1) also play crucial roles in the remarkable reaction efficiency and stability of Ni_2.1%Cr_3.6%O_x@S1–1.0. The specific CO₂-ODHP mechanism was systematically investigated based on the combined experimental (in situ FTIR and in situ UV–vis) and theoretical (Density Functional Theory) simulations, which illustrates a bifunctional catalysis process that the dehydrogenation of C₃H₈ to C₃H₆ predominantly occurs over the Cr site, while CO₂ adsorption, activation, and subsequent reaction with dissociated H mainly occurs over the Ni site. The DFT-based microkinetic modeling quantitatively validates the significantly higher reaction efficiency following Ni incorporation (7.42 × 10^–7 → 6.10 × 10⁷ s^–1), which is 14 orders of magnitude higher than that of the CrO_x site. Electronic structure analyses further demonstrate that Ni incorporation efficiently reduces the band gap (2.43 → 0.95 eV) between the NiCrO_x site and CO₂, which is identified as the fundamental factor underlying the superior CO₂-ODHP activity of Ni_2.1%Cr_3.6%O_x@S1–1.0. Generally, the present work has developed an efficient bifunctional catalyst for CO₂-ODHP, which paves the way for other highly efficient catalyst designs.