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研究了磷、镁和磷镁改性HZSM-5沸石的酸性及其与二甲苯异构化,甲苯用乙烯烷基化和正己烷裂化反应的关系。结果表明,HZSM-5沸石的酸性,二甲苯异构化活性、甲苯乙基化活性、己烷裂化反应活性、环己烷吸附量和表面积均随HZSM-5沸石的磷、镁含量增加而下降。在3％磷改性的HZSM-5沸石中再添加镁,随镁含量增加,总酸量增加,二甲苯异构化酸量与活性却下降。二甲苯吸附和表面积也有同样的变化。而且随镁含量增加,甲苯烷基化反应中甲苯转化率上升,对位选择性提高;正己烷裂化反应酸性与活性也增加。上述三种反应的活性直接取决于改性HZHM-5沸石的酸性、酸类型以及孔结构。
The acidity of phosphorus, magnesium and phosphorus-magnesium modified HZSM-5 zeolites and their relationship with the isomerization of xylene, the alkylation of toluene with ethylene and the cracking of n-hexane were studied. The results showed that the acidity, xylene isomerization activity, toluene ethylation activity, hexane cracking activity, cyclohexane adsorption capacity and surface area of HZSM-5 zeolite all decreased with the increase of phosphorus and magnesium content in HZSM-5 zeolite . Magnesium was added to 3% phosphorus-modified HZSM-5 zeolite. With the increase of magnesium content, the total amount of acid increased and the amount and activity of xylene isomerization decreased. Xylene adsorption and surface area also have the same changes. With the increase of magnesium content, the conversion of toluene in toluene alkylation reaction increased and the para-selectivity increased. The acidity and activity of n-hexane cracking reaction also increased. The activity of the above three reactions directly depends on the acidity, acid type and pore structure of the modified HZHM-5 zeolite.