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

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 Ni2.1%Cr3.6%Ox@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 CrOx, forming NiCrOx, which facilitates the adsorption and activation of CO2, thereby promoting the timely removal of subtracted H from C3H8. Additionally, the evenly dispersed NiCrOx species encapsulated by silicalite-1 (S1) also play crucial roles in the remarkable reaction efficiency and stability of Ni2.1%Cr3.6%Ox@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 CrOx site. Electronic structure analyses further demonstrate that Ni incorporation efficiently reduces the band gap (2.43 → 0.95 eV) between the NiCrOx site and CO2, which is identified as the fundamental factor underlying the superior CO2-ODHP activity of Ni2.1%Cr3.6%Ox@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.