Epoxidation of propylene by molecular oxygen over unsupported AgCu_x bimetallic catalyst

• 作 者: Xiang Zheng Yang-Long Guo Yun Guo Qing Zhang Xiao-Hui Liu Li Wang Wang-Cheng Zhan Guan-Zhong Lu
• 机 构: Key Laboratory for Advanced Materials, Research Institute of Industrial Catalysis, East China Univer
• 出 处: Rare Metals
• 发表日期: 2015年07期
• 关键词: propylene selectivity metallic adding crystallite dispersed sharply oxidized rem

The unsupported Cu and Ag catalysts with different oxidation states were prepared, and their catalytic performances for propylene epoxidation were investigated.The metallic Cu catalyst exhibits much higher catalytic activity and propylene oxide(PO) selectivity than Cu2 O and Cu O catalysts.The Cu0 species are the main active sites for propylene epoxidation, but Cu2 O and Cu O species are in favor of CO2 and acrolein production.The PO selectivity of 54.2 % and propylene conversion of 2.6 % can be achieved over the metallic Cu catalyst at 160 °C in initial stage, but metallic Cu catalyst would be oxidized to Cu2 O during propylene epoxidation, resulting in a sharp decrease in the PO selectivity and propylene conversion.Nanosize Ag Cuxbimetallic catalysts were prepared.It is found that adding Ag to the metallic Cu catalysts can prevent the oxidation of Cu and make Ag Cuxbimetallic catalysts more stable under the condition of propylene epoxidation.The Ag/Cu molar ratio can remarkably affect the catalytic performance of Ag Cuxcatalyst and the selectivity to PO and acrolein.After Ag Cuxwas supported on MOx-modified a-Al2O3, its catalytic performance can be improved and has a close relationship with the acid–base property of support.

The unsupported Cu and Ag catalysts with different oxidation states were prepared, and their catalytic performances for propylene epoxidation were investigated. The metallic Cu catalyst exhibits much higher catalytic activity and propylene oxide (PO) selectivity than Cu 2 O and CuO catalysts. are the main active sites for propylene epoxidation, but Cu2 O and Cu O species are in favor of CO2 and acrolein production. The PO selectivity of 54.2% and propylene conversion of 2.6% can be achieved over the metallic Cu catalyst at 160 ° C in initial stage, but metallic Cu catalyst would be oxidized to Cu 2 O during propylene epoxidation, resulting in a sharp decrease in the PO selectivity and propylene conversion. Nanosize Ag Cuxbimetallic catalysts were prepared. It is found that adding Ag to the metallic Cu catalysts can prevent the oxidation of Cu and make Ag Cuxbimetallic catalysts more stable under the condition of propylene epoxidation. The Ag / Cu molar ratio can remarkably affect ct the catalytic performance of Ag Cuxcatalyst and the selectivity to PO and acrolein. After Ag Cuxwas supported on MOx-modified a-Al2O3, its catalytic performance can be improved and has a close relationship with the acid-base property of support.