(391g) Multiscale Modeling Studies of the Effects of Catalyst Surface Morphology on Polymer Adsorption for Polyethylene Hydrogenolysis

As the global production of plastics skyrockets, it is critical to mitigate the generated plastic waste for a sustainable and circular economy. Heterogeneous catalytic reactions like hydrogenolysis are a powerful approach in the chemical upcycling of plastic waste to useful products like fuels and lubricants.

The interactions of the polymer (plastic) melt with the catalyst surface significantly influence the product distributions. It is difficult to experimentally study polymer adsorption on such surfaces at reaction conditions, especially since catalyst surfaces are not smooth. Since the rate of the hydrogenolysis of linear alkanes is surface morphology dependent, this lack of understanding of the adsorption behavior limits our ability to optimize the yields of the desired products.

Here, we present a multiscale modeling approach combining Density-Functional Theory (DFT) calculations and Replica Exchange Molecular Dynamics (REMD) simulations to study the effect of catalyst surface morphology on the adsorption of polyethylene melts at platinum surfaces of varying termination.

We developed an atomistic forcefield to describe platinum–polymer interactions for different platinum terminations. The forcefield was trained on DFT data. We next deployed the forcefield to simulate surrogate chains of polymer melts over different Pt surfaces. We show that the conformations of the polyethylene chains on the surface are determined by the surface morphology, and that they adsorb in shorter segments and at longer intervals on high-index surfaces than on flat surfaces. The surface dependent distribution of polymer conformations has implications for the hydrogenolysis of polymers on metal surfaces and thereby for the product distribution. We argue that the surface morphology is a macroscopic parameter that could be leveraged to tune the product distribution. The presented methodology can be applied to other polymer-catalyst systems to develop a better understanding of the conformations of polymers on catalyst surfaces and thus product distributions.