Fractionated degradation and valorization of polypropylene waste into sulfonate surfactants

Tandem upcycling presents a promising approach to converting plastic waste into valuable chemicals. Controlling the chain length distribution (CLD) of hydrocarbons in plastic degradation is crucial for the downstream synthesis of high-quality and high-value functional chemicals. However, controlling the CLD remains a significant challenge due to the high randomness and poor regulation of polymer chain scission. Herein, we introduce a fractionated degradation approach to tune the CLD of hydrocarbons derived from polypropylene (PP) degradation, thereby facilitating effective downstream valorization. By designing a fractionated degradation reactor that manipulates latent heat, we achieve size-selective degradation of PP into C₆-C₁₅ and C₁₅-C₂₈ α-alkenes with narrower and more tunable CLDs compared to traditional methods. Modeling and ASPEN simulations reveal a quasi-linear relationship between chain length and fraction temperatures, as well as a positive correlation between CLD and number of fractions. Scale-up experiments with 10 kg of real-life PP waste validate the effectiveness of the fractionated degradation. The PP-derived α-alkenes with narrow CLDs exhibit superior performance in sulfonation, resulting in foaming, detergency, and biodegradability, comparable to commercial sulfonate surfactants. Techno-economic and life cycle analyses demonstrate improved economic and ecological benefits of PP-to-surfactant upcycling over existing petrochemical-based methods.