Ce-OMS-2催化剂气相催化氧化甲苯制苯甲醛

采用回流法合成了氧化锰八面体分子筛(K-OMS-2),采用浸渍法制备了不同Ce含量的八面体分子筛(Ce-OMS-2)催化剂,并将其用于甲苯气相氧化制苯甲醛反应;考察了Ce含量、反应温度、空速、n(空气)∶n(甲苯)对催化剂活性的影响;用X射线衍射、傅里叶变换红外光谱、O2程序升温脱附方法对催化剂的结构进行了表征。实验结果表明,以Ce质量分数为46.0%的Ce-OMS-2为催化剂,在反应温度723K、空速2 400h-1、n(空气)∶n(甲苯)=4.2的条件下,甲苯的转化率为14.0%,苯甲醛的选择性达85.0%,苯甲醛收率为12.0%。表征结果显示,所制备的催化剂具有结晶良好的八面体分子筛结构,且Ce-OMS-2催化剂中存在Mn3O4,CeO2,CexMn1-xO2-y物相,Ce3+/Ce4+间的氧化还原循环给活性中心Mn提供晶格氧,改善了活性中心的电子传递,提高了甲苯的转化率和苯甲醛的选择性。

Vapor Phase Oxidation of Toluene to Benzaldehyde over Ce-Octahedral Molecular Sieve

Manganese oxide octahedral molecular sieves(K-OMS-2) were synthesized by reflux method.Ce-OMS-2 catalysts with different contents of Ce3+ were prepared by impregnation of K-OMS-2 with Ce(NO3)2 solutions and characterized by means of XRD,FTIR and O2-TPD.Selective vapor phase oxidation of toluene to benzaldehyde on the Ce-OMS-2 catalysts was studied.Effects of Ce content,reaction temperature,WHSV and mole ratio of air to toluene on Ce-OMS-2 catalyst performances were investigated.Under appropriate conditions: Ce mass fraction 46.0%,reaction temperature 723 K,WHSV 2 400 h-1 and n(air) ∶n(toluene) 4.2,conversion of toluene,selectivity to benzaldehyde and its yield are 14.0%,85.0% and 12.0%,respectively.Mn3O4,CeO2 and CexMn1-xO2-y phases exist in prepared Ce-OMS-2 catalyst.Alternate redox between Ce3+ and Ce4+ provides crystal lattice oxygen to active species of Mn,which favors the electrical transfer of active sites,and enhances conversion of toluene and selectivity to benzaldehyde.