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用量热滴定法、保留体积法和脉冲色谱法对M型和ZSM-4型沸石的表面酸性与二甲苯异构化催化活性进行了测定。结果表明,随着灼烧温度的提高,两类沸石的表面酸性先是增加,而后降低,分别于450℃,500℃左右有一极大值。在M型沸石上,NH_4~+交换度增加,酸性也增加;但当交换度超过一定限度后,酸性的增加变化不明显。两类沸石上邻二甲苯异构化脉冲反应活性的测定结果,显示出与其表面酸性之间有一定的对应关系。
The surface acidity and xylene isomerization catalytic activity of M-type and ZSM-4 zeolites were determined by thermal titration, retention volume and pulse chromatography. The results showed that the surface acidity of the two types of zeolite first increased and then decreased with the increase of the burning temperature, respectively, with a maximum at about 450 ℃ and about 500 ℃ respectively. On the M zeolite, the exchange degree of NH 4 + increased and the acidity also increased. However, when the exchange degree exceeded a certain limit, the change of acidity did not change obviously. The results of the measurement of the o-xylene isomerization pulse reaction activity on the two types of zeolites show a certain correspondence with the surface acidity.