摘要
利用硝基甲烷还原法制备了一系列不同粒径的纳米Au颗粒,用浸渍法担载于ZSM-5分子筛上制得Au/ZSM-5催化剂,并考察了其对分子氧氧化β-紫罗兰酮的催化性能.结果发现,该催化剂可以有效地催化分子氧氧化β-紫罗兰酮生成5,6-环氧-β-紫罗兰酮、4-氧代-β-紫罗兰酮、4-羟基-β-紫罗兰酮以及少量的二氢猕猴桃内酯,这些产物均是优质的香料及其前体.与传统的铬盐催化剂相比,本文制备的催化剂可选择性地将β-紫罗兰酮氧化为环氧化合物,并且反应后催化剂容易分离.详细探讨了不同载体、氧化剂、溶剂、反应温度和反应时间对β-紫罗兰酮氧化反应的影响.结果表明,催化剂的催化性能与担载金的颗粒大小密切相关,同时溶剂的性质也对反应有明显影响.以氯仿为溶剂时催化剂催化性能最好.催化剂循环使用五次仍具有较高的催化活性.
Gold nanoparticles with different sizes were prepared by reducing HAuC14 with nitromethane and were then supported on ZSM-5 zeolite by impregnation. The oxidation of β-ionone with molecular oxygen over Au/ ZSM-5 was studied. The results indicated that β-ionone was catalytically oxidized to 5,6-epoxy-β-ionone, 4- oxo-β-ionone, 4-hydroxy-β-ionone, and a little dihydroactinidiolide. All the products were valuable flavors or their precursors. Compared with the traditional chromium catalyst, the Au/ZSM-5 catalyst could selectively catalyze the oxidation ofβ-ionone to epoxy compounds, and the catalyst could be easily separated after the reaction. The effects of the support, solvent, oxidant, reaction temperature, and time on the catalytic performance of Au/ZSM-5 were investigated. The catalytic activity of the Au/ZSM-5 catalyst decreased with increasing size of Au nanoparticles. In addition, the solvent played an important role in the performance of the catalyst. The catalytic activity of Au/ZSM-5 was maintained after repeated use five times.
出处
《催化学报》
SCIE
CAS
CSCD
北大核心
2007年第3期239-245,共7页
