温度对Mg-Al-O复合氧化物催化剂体相和表面酸碱性质的影响

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１０７８Ｋ焙烧样品的固态ＭＡＳ＾２７Ａｌ核磁共振结果显示，样品呈现显著的物相转变，炽的过渡态对确定它们碱性质显得非常重要。ＸＰＳ测定样品中Ａｌ２ａ和Ｏ１ａ结合能与样品表面酸碱中心的强度相关。

INFLUENCE OF CALCINATION TEMPERATURE ON BULK AND SURFACE ACID/BASE PROPERTIES OF Mg-Al-O MIXED OXIDES

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.