A new study published in Engineering introduces a universal entropy‑reduction engineering strategy that enhances the hydrogenolysis of waste polyolefins by optimizing catalyst surface polarity, offering a scalable pathway for the sustainable upcycling of plastic waste.
Polyolefin hydrogenolysis has been recognized as a promising approach for the circular economy, yet the high entropy of polymer chains creates thermodynamic barriers that restrict catalytic activity. The large number of degrees of freedom in polymer molecules leads to a substantial entropy decrease upon adsorption onto catalyst surfaces, and the endothermic C–H activation step results in a positive Gibbs free energy change, making the process less favorable. Previous entropy‑reduction methods often rely on precisely designed porous structures, which struggle to match the complex compositions of real‑world polyolefin wastes and face limitations in large‑scale synthesis.
Researchers from Soochow University and other institutions have developed a surface polarity reconstruction method using silane coupling agents to modify conventional supported metal catalysts. This surface engineering tailors the polarity match between polymers and catalyst supports, effectively confining the molecular freedom of polyolefins during hydrogenolysis and stabilizing transition‑state adsorption on catalyst surfaces.
The team prepared ruthenium‑based catalysts with a metal loading of 3 wt% via a simple wet‑impregnation method and modified them using silane coupling reactions. The optimized Ru/CeO₂‑M0.2 catalyst showed improved hydrogenolysis performance compared with the unmodified sample. Characterization techniques including transmission electron microscopy, X‑ray photoelectron spectroscopy, and Fourier‑transform infrared spectroscopy confirmed that the modification did not cause metal leaching or alter the geometric and electronic structures of the ruthenium active sites. Instead, the silane agents selectively bonded with the oxide supports, transforming catalyst surfaces from hydrophilic to hydrophobic and strengthening van der Waals interactions between polyolefin chains and the catalyst.
Solid‑state nuclear magnetic resonance and molecular dynamics simulations further revealed that the modified surfaces increased the proportion of extended conformations of long‑chain alkane models, reduced conformational entropy, and raised the adsorption density of polyethylene chains near catalyst surfaces. The modified catalysts exhibited consistent improvements in hydrogenolysis activity across different oxide supports, including alumina, zirconia, and titania.
The optimized catalyst demonstrated good recyclability and stability in repeated hydrogenolysis runs and long‑term tests. It also showed effective performance in converting various polyolefin materials, such as low‑density polyethylene, high‑density polyethylene, and polypropylene, as well as commercial plastic wastes including bags, films, bottles, and container lids.
This entropy‑engineering approach provides a versatile and scalable modification route for traditional supported metal catalysts, helping to address the activity limitations caused by high polymer entropy during polyolefin hydrogenolysis. The findings support the development of industrially viable chemical upcycling technologies for waste polyolefins and contribute to more sustainable plastic waste management in the circular economy.
The paper "Entropy Engineering for the Efficient Hydrogenolysis of Waste Polyolefins," is authored by Qianyue Feng, Shengming Li, Feng Jiang, Panpan Xu, Yeping Xie, Mingyu Chu, Zhongyu Li, Weilin Tu, Muhan Cao, Qiao Zhang, Jinxing Chen. Full text of the open access paper: https://doi.org/10.1016/j.eng.2025.04.030
