The upcycling of polyolefin plastic waste into valuable chemicals and products via catalytic technology remains of scientific interest. While the activity of different metal catalysts has been explored in the literature, the viability of oxide catalysts remains underexplored. In this study, we computationally investigated the activity of TiO2 catalysts for polyolefin hydrogenolysis following the reported activity of ZrO2 catalysts. The anatase form of TiO2 was considered due to its high reactivity, polyolefin was modeled using a hexane molecule, and typical reaction conditions of 573 K and 9 bar PH2 were used. Both the dominant (101) and minority (001) facets of anatase were screened for activity using DFT (PBE+U) and microkinetic modeling. We found that both the clean and defect crystalline surfaces of (101) and (001) anatase TiO2 are inactive for hydrogenolysis, due to a high reaction barrier for the required initial dehydrogenation. The reconstructed (001) surface, reported to be more active, was also found to have high barrier, although significantly lower compared to the crystalline surfaces. Similarly to the reported adatom observation on ZrO2, we observed that Ti adatom sites are possible on (101) anatase and these sites are stabilized in the presence of surface moisture and a H2 rich reaction environment. Ti(OH)(O) and Ti(O) sites were found to be stable at relatively high (10-6 bar) PH2O, while only Ti(O) sites are stable at low (10-11 bar) PH2O. Ti(OH)(O) site was observed to be inactive for hydrogenolysis due to a high effective barrier for all possible pathways. However, the Ti(O) site was found to be active for hydrogenolysis via β-alkyl elimination mechanism with an effective barrier of <2 eV. These findings were corroborated by experimental observations where TiO2 is found to be active for hydrogenolysis and activity decreases with increasing moisture content.
