Selective chemical looping combustion of acetylene in ethylene-rich streams

Abstract

The requirement for C₂H₂ concentrations below 2 parts per million (ppm) in gas streams for C₂H₄ polymerization necessitates its semihydrogenation to C₂H₄. We demonstrate selective chemical looping combustion of C₂H₂ in C₂H₄-rich streams by Bi₂O₃ as an alternative catalytic pathway to reduce C₂H₂ concentration below 2 ppm. Bi₂O₃ combusts C₂H₂ with a first-order rate constant that is 3000 times greater than the rate constant for C₂H₄ combustion. In successive redox cycles, the lattice O of Bi₂O₃ can be fully replenished without discernible changes in local Bi coordination or C₂H₂ combustion selectivity. Heterolytic activation of C–H bonds across Bi–O sites and the higher acidity of C₂H₂ results in lower barriers for C₂H₂ activation than C₂H₄, enabling selective catalytic hydrocarbon combustion leveraging differences in molecular deprotonation energies.