中文摘要：

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（C3H8）：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Cr^-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．

英文摘要：

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（C3 H8 ） ： 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 O2,and this might favor the formation of PO.