摘要
基于“酸位效率参量”的定义，对Ｂａｒｔｈｏｍｅｕｆ定义的铝原子酸效率参量α０作出诠释．强调α０不仅是铝浓度依赖而且是样品铝分布状态依赖的．具有相同Ｓｉ／Ａｌ的丝光沸石原粉与经历过脱铝的丝光沸石，二者骨架硅、铝分布有很大区别．根据２９ＳｉＭＡＳＮＭＲ拟谱我们曾推断丝光沸石的强酸位更易于从骨架解脱，并进一步予言脱铝丝光沸石的酸性是急剧减弱的．本文的理论计算相当成功地解释了分别对丝光佛石原粉及脱铝丝光沸石所进行的氨ＴＰＤ实验所获二者的酸量及酸量／铝原子含量比率的数据．
Abstract Four types of lattice Al ions were defined for mordenite. Each type was distinguished by the present number (0,1,2,3) of other Al on its next-nearest-neighbors. We call the relative pop ulations of four types AlO4 the Al-Al nnn-distribution in the mordenite sample. The differences of the local environment of AlO4-, lead to the existence of four add strengthes: 0 > 1 > 2 > 3.In the present work, the definition of 'acid site efficiency parameter' which scales the contribution of a type AlO4- towards the acidity is introduced.Based on this definition the efficienCy parameter α0 introduced by Barthomeuf can be expressed quantitatively by the Al-Al nnn-distribution of the mordenite sample.It has been emphasised before that the Al-Al nnn-distributions in parent and dealuminated mordenite samples are quite different. Both Al-Al nnn-distributions can be calculated by Month Carlo simulation. Since the strong-acid sites are preferentially removed, we predict theoretically that the acidity of the dealuminated mordenite is always weaker than the parent mordenite sample with the same Si/Al framework ratio. The Al content dependences of α0 are quite different between parent and dealuminated mordenites. The theory explains the results of the ammonia TPD acidity measurement for the parent and dealuminated mordenite samples satisfactorily.
