Effect of TS-1 Crystal Planes on the Catalytic Activity of Au/TS-1 for Direct Propylene Epoxidation with H<sub>2</sub> and O<sub>2</sub>
Zhishan Li, Xiaoyang Chen, Weihua Ma, Qin Zhong
Abstract
In this work, we demonstrated that titanium silicalite-1 (TS-1) crystal planes affected the activity of nanogold supported on TS-1 (denoted as Au/TS-1) for direct propylene epoxidation with H2 and O2. TS-1 with different amounts of the organic template tetrapropylammonium (TPA+) was obtained by controlling the calcination temperature and time. It was found that the residual TPA+ in TS-1 affected the relative intensities of the crystal planes of (101) and (501) (denoted as I(101)/I(501)). The less the amount of residual TPA+, the greater the I(101)/I(501) ratio. Simultaneously, the Au–Ti catalyst with less TPA+ showed a higher propylene oxide formation rate. There existed two reasons. One was that the number of active sites increased with the removal of TPA+. The other was that a greater I(101)/I(501) ratio contributed to the adsorption of propylene, which was beneficial for enhancing the activity. After excluding the influence of active sites, the catalyst with a greater I(101)/I(501) ratio exhibited higher activity for propylene epoxidation. The present work reveals the effect of TS-1 crystal planes on the catalytic activity of Au/TS-1 for the first time.