Multimetallic catalysts of RuO2–CuO–Cs2O–TiO2/SiO2 for direct gas-phase epoxidation of propylene to propylene oxide

摘要

RuO _(2) –CuO/SiO _(2) catalysts doped with Cs _(2) O and TiO _(2) were investigated for the direct gas phase epoxidation of propylene to propylene oxide (PO) using molecular oxygen under atmospheric pressure. The optimal catalyst was achieved at Ru/Cu/Cs/Ti = 8.3/4.2/0.6/0.8 by weight and total metal loading of 21 wt% on SiO _(2) support. NH _(3) and CO _(2) temperature programmed desorption measurements of RuO _(2) –CuO/SiO _(2) catalyst modified with Cs _(2) O showed that the surface's acidity decreased, resulting in enhanced PO selectivity. The addition of TiO _(2) increased the PO formation rate by promoting the synergy effect between RuO _(2) and CuO. Using the Box–Behnken design of experiments on the RuO _(2) –CuO–Cs _(2) O–TiO _(2) /SiO _(2) catalyst, an extraordinarily high optimal PO formation rate of 3015 g _(PO) h ~(?1) kg _(cat) ~(?1) was obtained with a feed comprised of O _(2) /C _(3) H _(6) at a volume ratio of 3.1 and (O _(2) + C _(3) H _(6) )/He at a volume ratio of 0.26, all at 272 °C and 34 cm ~(3) min ~(?1) . To the knowledge of the authors, this is the highest PO formation rate ever reported for direct propylene epoxidation via O _(2) .