Selective chemical looping combustion of acetylene in ethylene-rich streams.
basic_science · Level V
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- Record sourced from PubMed, PMID 39946462.
- Also identified by DOI 10.1126/science.ads3181.
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Abstract
The requirement for C<sub>2</sub>H<sub>2</sub> concentrations below 2 parts per million (ppm) in gas streams for C<sub>2</sub>H<sub>4</sub> polymerization necessitates its semihydrogenation to C<sub>2</sub>H<sub>4</sub>. We demonstrate selective chemical looping combustion of C<sub>2</sub>H<sub>2</sub> in C<sub>2</sub>H<sub>4</sub>-rich streams by Bi<sub>2</sub>O<sub>3</sub> as an alternative catalytic pathway to reduce C<sub>2</sub>H<sub>2</sub> concentration below 2 ppm. Bi<sub>2</sub>O<sub>3</sub> combusts C<sub>2</sub>H<sub>2</sub> with a first-order rate constant that is 3000 times greater than the rate constant for C<sub>2</sub>H<sub>4</sub> combustion. In successive redox cycles, the lattice O of Bi<sub>2</sub>O<sub>3</sub> can be fully replenished without discernible changes in local Bi coordination or C<sub>2</sub>H<sub>2</sub> combustion selectivity. Heterolytic activation of C-H bonds across Bi-O sites and the higher acidity of C<sub>2</sub>H<sub>2</sub> results in lower barriers for C<sub>2</sub>H<sub>2</sub> activation than C<sub>2</sub>H<sub>4</sub>, enabling selective catalytic hydrocarbon combustion leveraging differences in molecular deprotonation energies.