Unraveling the Coverage-Dependent Kinetics of Chemical Looping Selective Hydrogen Combustion in Propylene-Rich Streams

Nonoxidative propane dehydrogenation (PDH) is typically constrained by thermodynamic equilibrium and high energy input. Coupling PDH with chemical looping selective hydrogen combustion (CL-SHC) enables in situ H2 removal to boost propylene production, yet the kinetic factors governing oxygen carrier selectivity remain ambiguous. This paper describes the surface coverage-dependent kinetics of CL-SHC over size-tunable FeVO4 oxygen carriers (50–200 nm) in propylene-rich streams. Quantitative kinetic analyses reveal that CL-SHC is dominated by surface reaction rather than bulk lattice oxygen diffusion, governed by H2/C3H6 competitive adsorption and C−H/H−H bond activation. Specifically, nanosized FeVO4 (ca. 50 nm) exhibits favorable H2 adsorption and surface oxygen exchange, enabling higher SHC selectivity with suppressed propylene over-oxidation. By coupling FeVO4 with a PtSn PDH catalyst, the tandem system further increases the propylene selectivity to 92% at 500 °C, representing a 2.7- and 1.5-fold propylene productivity compared to the sole PtSn PDH catalyst and conventional VOx-FeVO4 tandem systems. This work establishes the structure-kinetics-performance relationship of oxygen carriers for CL-SHC, offering a strategy for rational design of tandem systems toward efficient light alkane upgrading.