Na--+和卤素修饰的Ag/MgO催化剂在丙烯环氧化反应中的催化性能

Abstract

制备了一系列未经修饰和经nA+和卤素修饰的5%(质量分数)Ag/MgO催化剂.考察了富氧条件(P(C3H6)∶P(O2)=2.53∶98.8)下,nA+和卤素的修饰对Ag/MgO催化剂的丙烯环氧化反应性能的影响.研究发现,添加于催化剂中的nA+有助于环氧丙烷选择性的提高,而与nA+共存的Cl-和br-则显著增加环氧丙烷的选择性.氧程序升温脱附(O2-TPd)表征显示,Ag/MgO催化剂中nA+和Cl-的添加提高了催化剂中次表面氧的含量和稳定性,从而促进了其在丙烯环氧化反应中的催化性能.

A series of 5%(by mass)Ag/MgO catalysts modified with and without Na+ and halogen anions were prepared,and the performances of these catalysts for epoxidation of propylene were studied under O2-rich condition(p(C3H6)∶p(O2)=2.53∶98.8) by using oxygen as oxidant.It was found that catalysts modified with Na+ showed higher selectivity for PO formation.Furthermore,Cl-or Br-coexisted with Na+ in the catalysts could also lead to obvious increase of PO selectivity(>20%).O2-TPD characterization suggested that Na+ and Cl-in the catalysts stabilized subsurface oxygen species Oβ,and this might favor the formation of PO.