Cleavage Alkylation Coupling with Versatile Amide-Based Eutectic Catalytic Systems

This study introduces amide-based eutectic solvents (ESs)
as a
versatile and high-efficiency catalytic system for converting polyolefin
waste into liquid alkanes in coupled cracking–alkylation. Owing
to the rich variety of molecular active species (i.e., [AlCl3(Acetamide)n] and AlCl3) and
ionic active species (i.e., [Al2Cl7]− and [AlCl2(Acetamide)n]+) present in the catalytic system, carbocation intermediates
can be stably generated, thereby facilitating hydride transfer and
cleaving polyethylene C–C bonds during the cracking cycle.
For the first time, we establish a direct and quantitative correlation
between Al species diversity and carbocation concentration, validated
by Et3SiH chemical trapping combined with multinuclear
NMR and operando IR spectroscopy. We demonstrate tunable selectivity
to either light gasoline (C4–C10) or
aviation kerosene (C7–C18) with isopentane
or isopentene as alkylation reactants. Time-resolved product analysis
together with isotopic labeling clearly confirms that aviation kerosene-range
hydrocarbons (C7–C18) are primarily derived
from polyethylene fragments and chain-extended by iC5= alkylation. Ab initio molecular dynamics
simulations reveal that cooperative dissociation of diverse Al species
sustains a stable tert-butyl and chloromethyl carbocations
population, rationalizing the superior catalytic efficiency of Acetamide-1.5AlCl3. These advances provide both mechanistic clarity and a broadly
applicable strategy for selective production of gasoline- and kerosene-range
hydrocarbons from plastic waste, offering new opportunities for premium-grade
fuel generation.