摘要
用 NH3和 CO2 作探针分子 ,采用红外光谱 ,真空原位测定 Mg-Al-O复合氧化物表面酸碱中心的类型结果表明 ,主要存在 L 酸 ,碱中心是氧阴离子 ,而焙烧温度对样品表面碱中心的类型几乎没有影响 ,在 673、873和 1 0 73 K焙烧样品的固态 MAS2 7Al核磁共振结果显示 ,样品呈现显著的物相转变 ,转变中的过渡态对确定它们表面酸碱性质显得非常重要。 XPS测定样品中 Al2 s和 O1s结合能与样品表面酸碱中心的强度相关。
NH 3 and CO 2 molecules were used as the probing molecules to investigate the nature of acid and base sites on Magnesium Aluminium mixed oxides.Infrared spectroscopic studies of these adsorped molecules indicated that the acid sites were mainly of Lewis acid feature,whereas the base sites were anionic surface oxygen.The results showed that the calcination temperature has little influence on the nature of surface base sites.Results of solid state magic angel spinning 27 Al NMR revealed that significant phase transitions occur in the samples upon calcination at 673,873 and 1073K,respectively.These transitions seem very important in determining their surface acid/base properties.Furthermore,the binding energies of Al 2s and O 1s of the samples determined by XPS is relevant to the strength of surface acid and base sites of the samples.
出处
《化学研究与应用》
CAS
CSCD
2000年第3期273-277,共5页
Chemical Research and Application
基金
湖南省自然科学基金! (No.98JJY2 0 57)
湖南省教委和湖南省重点学科资助!(湘教通 [1997]2 0 0号 )课题
关键词
Mg-Al-O复合氧化物
体相结构
酸碱性质
催化剂
magnesium aluminum mixed oxide
bulk structure
acid/base properties
MAS 27 Al NMR
XPS
