Engineering pore structure and acidity of ferrierite zeolites by organic structure directing agents for n-butene isomerization

Abstract

Zeolites are important heterogeneous catalysts in industrial applications, but always suffer from deactivation caused by carbon deposition. In this work, a simple strategy was developed to engineer Ferrierite (FER) zeolites with different pore structure and distribution of Brønsted acid sites by using different organic amine structure directing agents, i.e., pyrrolidine (PY), ethylenediamine (EDA), cyclohexylamine (CyHA). The obtained PY-FER not only exhibited optimal hierarchical porosity, but also showed the highest density of Brønsted acid sites inside micropores and lowest Lewis/Brønsted acid ratio (L/B). Based on the corresponding performance in n-butene skeletal isomerization, it can be concluded that high L/B is prone to coke formation, while a balance between micropores and mesopores is beneficial to the reduction of carbon deposition. Besides, a model y=y0−Aexp(−Kt) was established to describe the behavior of the carbon deposition, which matches well with the properties of the zeolites. These findings are significant for the design of zeolites.