Assessing the kinetic accessibility of the hydride transfer of the silica-supported organometallic catalyst

Abstract

A large portion of plastic waste is burned or put into a landfill, which are unsustainable practices. Recycling is a good solution to increase circularity, but currently a significant part of plastic is recycled mechanically. Mechanical recycling reduces the quality of the plastic, consequently plastic can only be recycled a few times before it needs to be discarded. This significant downside can be solved by chemical recycling aided by catalysis. The investigated zirconium catalyst (BuCp2ZrH – OSi) is supported on an amorphous silica surface. The ISE group at the TU Delft has developed a configurational space exploration algorithm that has found states of this supported catalyst, which are far more thermodynamically stable compared to a chemical guess. Many stable states are the result of the hydride transfer from Zr to Si. The thermodynamic stability does not only determine if the state can be accessible at the reaction conditions (80∘C), the kinetics must also be considered as well. To determine the kinetic accessibility, the hydride transfer activation energies were estimated for various amorphous silica surfaces as well as perfect beta-cristobalite. The Cristobalite and minimum strain silica surface showed relatively high energy reaction barriers (≈96-107 kJ/mol) compared to the higher strain surfaces (≈15-54 kJ/mol). This shows that the reaction barrier is highly dependent on the surface structure. The found barriers show that the configurational space exploration algorithm can find kinetically accessible states at reaction conditions.