Propylene oxide is currently produced commercially from propylene isolated as a co-product of petroleum processing. The reaction processes are based on chlorohydrin or hydroperoxide synthesis procedures, which are very hazardous. These processes are inefficient, energy intensive, involve multiple steps, have low selectivity, and are accompanied by huge volumes of effluent wastewater and by-products. In addition, direct oxidation catalysts are very expensive due to the fact that they contain precious metals, like gold and silver. It is evident that propylene oxide production could be significantly enhanced by finding an alternative production route than starting with a propylene feedstock.

When soybean oil is used to produce biodiesel, significant quantities of glycerin are produced as a co-product. Recently, commercial production of propylene glycol from glycerin has begun. This propylene glycol has the potential to be a feedstock that can be further reacted to produce propylene oxide and other oxygenated C3 hydrocarbons that are commonly produced using a propylene feedstock, providing a renewable route to common petroleum-based C3 hydrocarbons.

The limited literature covering the production of propylene oxide from propylene glycol indicates that basic catalysts are optimum for this reaction to occur selectively to propylene oxide. Our studies have focused on using common base catalysts, including magnesium oxide, calcium oxide, and alkali modified aluminas and zeolites. We have identified nine total products that have been produced from our gas-phase reactivity studies: acetaldehyde, propylene oxide, propionaldehyde, acetone, 2-propanol, 1-propanol, allyl alcohol, acetol, and dipropylene glycol. The effect of catalyst type, temperature, and space time on selectivity to propylene oxide will be discussed and potential reaction pathways explored. We have found that, when the residence time of propylene glycol in the reactor is decreased, an increase in selectivity to propylene oxide is observed, indicating that propylene oxide may be a reactive intermediate in the production of the other byproducts formed. In addition, the production of dipropylene glycol appears to contribute to higher propylene oxide production rates. While the primary goal of this research was to produce propylene oxide, catalysts that are effective at producing any other of the other byproducts at high selectivity may be useful routes for the renewable production of other high-volume bulk chemicals that are typically produced from propylene.