Pyrolysis gas of polyethylene exhibits a complex composition, predominantly comprising ethylene, methane, and propylene. Nickel-based catalysts are often used for dry reforming of methane, but suffer from metal sintering and carbon deposition. On the basis of Ni/γ-Al2O3, Mg, Ce and Cu were added to improve the stability in this work. Through experiments on cracking and dry reforming of pyrolysis gas, activation effects of Ni on pyrolysis gas and CO2 were investigated, along with effect of promoters on carbon deposition. The stability and mechanism of carbon deposition were further studied for the optimal catalyst. The results indicate that CH4 predominantly undergoes C−H bond dissociation at Ni active sites, with Ni demonstrating 10.2-fold maximum H2 yield higher than γ-Al2O3. C2H4 achieves moderate activation on γ-Al2O3 surfaces, Ni incorporation enhances dehydrogenation kinetics. C3H6 exhibits strong intrinsic activation on γ-Al2O3, with Ni providing limited synergistic effects. Activation of CO2 predominantly relies on Ni active sites, exhibiting 7.0-, 1.9-, and 2.1-fold enhancements in maximum CO production rates compared to γ-Al2O3 during the dry reforming of methane, ethylene and propylene respectively. Ce emerges as the optimal promoter, achieving a marked 93% reduction in total carbon deposition on 10NiAl. The oxygen vacancy in CeO2 can activate CO2 to realize lattice oxygen regeneration. The lattice oxygen can migrate to Ni-Ce interface, effectively compensating for oxygen vacancies surrounding Ni. This study provides a new way for resource recovery from waste polyethylene plastics.
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