(330c) Newly Proposed Catalytic Route for the Production of Propylene Epoxide

Ethylene glycol, which is made by the addition of water to ethylene epoxide, is widely used as an automobile antifreeze. Because of ethylene glycol’s sweet taste and high toxicity, each year many pets and other animals consume spilled anti-freeze and die. Propylene glycol is a low toxicity alternative but more difficult manufacture than ethylene glycol. This is because ethylene epoxide can be manufactured by passing ethylene over a silver catalyst in the presence of oxygen, while a similar process starting from propylene yields mostly unwanted by-products. I propose a completely new catalytic route for the production of propylene epoxide. In this proposed process, ethylene epoxide plus propylene are passed over a transition metal catalyst to convert them into ethylene plus propylene epoxide. During this process, an oxygen atom is transferred from ethylene epoxide to the catalyst (represented by the symbol M) to form ethylene plus an MO intermediate. The MO intermediate reacts with propylene to form propylene epoxide plus M. Density functional theory (DFT) computations were performed to identify an organometallic complex, M = ZrO₄N₄C₅₂H₇₂, having a suitable molecular architecture for catalyzing this reaction. Approximate energies and geometries of the reactants, intermediates, transition states, and potential side products were computed. Additional computations are needed to investigate the effects of ligand substituents on catalyst reactivity, selectivity, and deactivation kinetics to optimize catalyst performance.