An <i>in Silico</i> Investigation into Polyester\nAdsorption onto Alumina toward an Improved Understanding of Hydrogenolysis\nCatalysts

Chemical\nrecycling of end-of-life plastic wastes through\nhydrogenolysis\nis a promising pathway for achieving a circular plastics economy and\nreducing overall energy costs. Understanding molecular interactions\nat the inorganic–organic depolymerization interface is crucial\nfor enhancing catalyst performance and overcoming challenges posed\nby mixed plastic waste streams. We investigated a fundamental step\nin the depolymerization process: physisorption of polymers onto the\nmetal oxide support preceding diffusion to and reaction at the catalyst–support\njunction. Molecular dynamics simulations, augmented with well-tempered\nmetadynamics, were conducted to explore the adsorption of polylactic\nacid (PLA) and polyethylene terephthalate (PET) oligomers onto a hydroxylated\nalumina support surface. Our findings revealed multiple layers of\nhighly oriented solvent molecules (1,4-dioxane) above the surface,\ncreating significant barriers to polyester adsorption. Disrupting\nand displacing these solvent layers led PET oligomers to adsorb closer\nto and interact stronger with the surface than PLA oligomers, possibly\ncontributing to the higher reaction temperatures needed to achieve\nfull conversion in PET versus PLA hydrogenolysis. We further suggest\nan experimental approach to validate our results of solvent layering\nbehavior through predictions of X-ray reflectivity that are consistent\nwith our initial experiments. The insights gained in this study can\nbe leveraged to refine our understanding of catalytic mechanisms to\npredict depolymerization reactivity and selectivity and improve future\nhydrogenolysis catalyst designs.