Ni2＋－交换蒙脱石的TPR和XRD研究

对一组自制Ｎｉ２＋－交换蒙脱石样品中是镍物种的存在形式及焙烧温度影响进行了ＴＰＲ和ＸＲＤ考察．结果表明，样品中镍负载量等于或小于Ｎｉ２＋的交换量时，镍主要以难还原的可交换阳离子Ｎｉ（ＯＨ）ｑ＋ｘ一种形式存在，如果样品中镍负载量超过Ｎｉ２＋的交换量时，镍则以难还原的可交换性阳离子Ｎｉ（ＯＨ）ｑ＋ｘ和易还原的自由态镍Ｎｉ（ＯＨ）２或ＮｉＯ两种形式存在，随着焙烧温度的提高，样品中的各镍物种均可迁入蒙脱石骨架结构内，只是迁入难度不尽相同：可交换性镍＜柱羟基镍＜自由态镍．Ｎｉ２＋－交换蒙脱石中自由态镍的存在，可能是造成其催化活性在高温时明显下降的主要因素

TPR and XRD Studies on Ni 2 exchanged Montmorillonite

Ni species and the effects of calcination temperatures on them are studied by means of TPR and XRD for a group of samples of Ni 2 exchanged montmorillonites.The results show that only one species,exchangeable cation Ni(OH) q x which is not a species easy to be reduced,occurs in the samples when Ni loadings on samples are eaqual to the Ni 2 exchange content,and two species,exchangeable cation Ni(OH) q x and free state Ni(OH) 2 which is a species easy to be reduced,occurs in the samples simultaneously when Ni loadings on samples are more than the Ni 2 exchange content.All Ni species in the samples can migrate into the framework structure of montmorillonite after sufficient calcination,while each of the Ni species shows a distinct degree of the migration,exchangeable Ni >pillared Ni>free state Ni.The free state Ni in the Ni 2 exchanged montmorillonite is a main factor to damage the catalytic activity of the montmorillonite at elevated temperature.