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

Epoxidation of Propylene over Ag/MgO Catalysts Modified Na^+ and Halogen Anions

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（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.