Understanding the Gas-Phase Epoxidation of Propene With Hydrogen Peroxide Vapor

The production of propylene oxide (PO) with aqueous hydrogen peroxide over TS-1 is an efficient and clean process where water is the only by-product. If the H₂O₂ is generated in situ in a plasma reactor, no solvent is required and the peroxide obtained has high purity. After the plasma, the produced vapor peroxide can react directly with propene, avoiding intermediate capturing steps and resulting in a simple integrated process. On the other hand, working with hydrogen peroxide vapor is a challenging task, due to its fast decomposition into oxygen and water. In this project the gas-phase epoxidation of propylene was studied in a packed bed reactor, analyzing the main factors involved.

The complications encountered when working at high temperatures with H₂O₂ vapor are evaluated and solutions are proposed. Factors like the equipment materials used, as well as the presence of a catalyst were identified as very relevant to the matter. However, besides the high tendency of hydrogen peroxide to decompose, we could demonstrate that the epoxidation of propene is fast enough so that propene oxide is obtained with productivity values of up to 12 kg_PO·kg_cat^-1·h^-1, which are higher than the minimum required for industrial implementation. Selectivities of hydrogen peroxide and propene to PO of 40% and close to 90% respectively have been obtained.

In our presentation we will describe the effects of the process parameters on the reaction and make a comparison with other direct epoxidation routes.