Pyrolysis-based plastic chemical recycling has gained
significant
industrial attention due to its advantage of eliminating complex plastic
sorting processes. However, plastic pyrolysis oil contains various
components that require stringent removal before subsequent processes.
In particular, Cl compounds originating from the decomposition of
poly(vinyl chloride) can cause serious corrosion of reactors and catalyst
deactivation in downstream processes. While extensive research has
been conducted on the removal of other heteroatoms (S, N, and O) from
organic compounds via hydrotreating, studies on the removal of Cl
have been scarce. In this study, hydrodechlorination over Pt catalysts
on various supports is comprehensively investigated using 1,2-dichloroethane
as a model reactant. Our results demonstrate that Pt on γ-Al2O3 can exhibit exceptionally high catalytic activity
compared to those on other supports due to a distinct bifunctional
mechanism. Rigorous studies reveal that the Lewis acidic pentacoordinated
Al sites of γ-Al2O3 activate C–Cl
bonds, whereas Pt activates H2 and provides spillover H
to remove Cl as HCl. The bifunctional mechanism enables the minimized
use of precious Pt (<0.1 wt %) to achieve high activity. Pt/γ-Al2O3 also allows for efficient Cl removal (96.8%)
with high stability in treating waste plastic pyrolysis oil containing
7500 ppm of Cl.