Thermal stability of TPA template and size-dependent selectivity of uncalcined TS-1 supported Au catalyst for propene epoxidation with H2 and O2

A tetrapropyl-ammonium (TPA) template, as the most critical component inside microporous channels of an uncalcined Au/TS-1 catalyst (Au/TS-1-B), hinders the entrance of Au nanoparticles into the micropores and thus prevents the micropore blocking induced deactivation for direct propene epoxidation with H-2 and O-2. In this work, the essential stability of the TPA template at distinct reaction temperatures is first investigated. It is found that the TPA template inside micropores decomposes to H2O, NH3 and propene after 350 degrees C. Based on a suitable reaction temperature range (< 350 degrees C), the PO formation rate shows a volcano-shaped relationship with reaction temperature and reaches a maximum value of 220 g(PO) h(-1) kg(Cat)(-1) at 260 degrees C, which is a noteworthy result compared with other reported catalysts. Moreover, due to presence of the TPA template inside micropores of TS-1, size-dependent selectivity shown on Au/TS-1-B should be intrinsic because the Au/TS-1-B catalyst exhibits uniform-sized Au nanoparticles and high stability. Hence, a series of Au/TS-1-B catalysts with different Au sizes are then tested for propene epoxidation, and the plausible reaction routes are also discussed.