碱处理改性对ZSM-5分子筛柴油催化裂化反应性能的影响

Effects of Alkali Treatment on Catalytic Cracking of Diesel over ZSM-5 Zeolite

在不同温度的NaOH溶液中对ZSM-5分子筛进行处理,并将其应用于轻柴油催化裂化反应以考察其催化性能。结果表明,碱处理能够在不破坏ZSM-5分子筛晶相结构的情况下在晶体内部引入介孔,并且处理温度越高介孔的引入程度越大,但碱处理使得分子筛酸性明显降低。然而与分子筛原样相比,催化裂化反应前800℃的高温水汽处理使得碱处理的ZSM-5的微孔孔容稍许降低、强酸量稍许增强,弱酸量和介孔孔容持续且显著增加,因此碱处理的ZSM-5分子筛用于轻柴油催化裂化反应,在成功引入介孔的同时基本维持了丙烯等低碳烯烃良好的产物选择性和微反活性指数。

The ZSM-5 zeolite was treated in the Na OH solution at different temperature and the catalytic cracking of light diesel oil was carried out over the corresponding alkali- treated ZSM-5 zeolites. Alkali treatment can introduce mesopores inside the crystal without destroying its phase structure. The higher the treatment temperature is,the higher the degree of mesopore introduced is. The acidity of ZSM-5 is obviously reduced at same time. However,compared with the parent zeolite,the steam treatment at 800 ℃ before the cracking reaction led to an obvious increase in acidity and a continuous increase in mesorpores but slight decrease in micropores for the alkai- treated ZSM-5. The nice selectivity of propylene and other light olefins as well the MAT index are therefore well maintained when mesopores are successfully introduced into ZSM-5 due to alkali treatment.