The effects of alkaline treatment on the physical properties of ZSM-5 catalysts and on their activities for methanol to aromatics conversion have been investigated. A mild alkaline treatment （0.2 and 0.3 mol/L NaOH）...The effects of alkaline treatment on the physical properties of ZSM-5 catalysts and on their activities for methanol to aromatics conversion have been investigated. A mild alkaline treatment （0.2 and 0.3 mol/L NaOH） created mesopores in the parent zeolite with no obvious effect on acidity. The presence of mesopores gives the catalyst a longer lifetime and higher selectivity for aromatics. Treatment with 0.4 mol/L NaOH decreased the number of Bronsted acid sites due to dealumination and desilication, which resulted in a lower deactivation rate. In addition, more mesopores were produced than with the mild alkaline treatment. As a result, the lifetime of the sample treated with 0.4 mol/L NaOH was almost five times that of the parent ZSM-5. Treatment with a higher alkaline concentration （0.5 mol/L） greatly reduced the number of Bronsted acid sites and the number ofmicropores resulting in incomplete methanol conversion. When the alkalinetreated catalysts were washed with acid, some of the porosity was restored and a slight increase in selectivity for aromatics was obtained.展开更多
文摘The effects of alkaline treatment on the physical properties of ZSM-5 catalysts and on their activities for methanol to aromatics conversion have been investigated. A mild alkaline treatment （0.2 and 0.3 mol/L NaOH） created mesopores in the parent zeolite with no obvious effect on acidity. The presence of mesopores gives the catalyst a longer lifetime and higher selectivity for aromatics. Treatment with 0.4 mol/L NaOH decreased the number of Bronsted acid sites due to dealumination and desilication, which resulted in a lower deactivation rate. In addition, more mesopores were produced than with the mild alkaline treatment. As a result, the lifetime of the sample treated with 0.4 mol/L NaOH was almost five times that of the parent ZSM-5. Treatment with a higher alkaline concentration （0.5 mol/L） greatly reduced the number of Bronsted acid sites and the number ofmicropores resulting in incomplete methanol conversion. When the alkalinetreated catalysts were washed with acid, some of the porosity was restored and a slight increase in selectivity for aromatics was obtained.
