Enhancement of the strong Brønsted acidity and mesoporosity: Zr4+ promoted framework modification of Zeolite Y

Abstract

Brønsted acid of zeolite Y plays an important role in catalytic cracking reaction. However the proportion of strong Brønsted acid in conventional zeolite Y is small which limits the efficiency of transformation. This work described a way to achieve the goal of significant increasing the density of strong Brønsted acid via introducing Zr4+ into the framework of zeolite Y. The density of strong Brønsted acidity increased from 0.085 (HY) to 0.208 mmol/g ([Zr,Al]-HY). Systematic characterization results showed that the introduction of Zr4+ could produce more Si(1Al) but less Si(3Al) and Si(2Al) species in zeolite which was responsible for the high density of Brønsted acid. And abundant mesopores were also formed during the Zr4+ implanting. For the catalytic cracking results of n-octane, the conversion on [Zr,Al]-HY was 1.67 times of that on conventional HY. The apparent activation energy of cracking n-octane on [Zr,Al]-HY was reduced to 73.3%, which indicated that the increase of strong Brønsted acid had significant effect on catalytic cracking. On the other hand, a large number of mesoporous structures of [Zr,Al]-HY provided a good foundation for the catalytic cracking of steric hindered 1.3.5-triisopropylbenzene (1,3,5-TIPB).