Synthesis and catalytic application of FER zeolites with controllable size

Abstract

The crystal size of zeolites has an enormous effect on zeolite properties and catalytic performance. Herein, a direct hydrothermal synthesis method to control the size of FER zeolites, by using piperidine (PI) as the structure directing agent (SDA) assisted by cetyltrimethyl ammonium bromide (CTAB), is developed. All the resultant FER samples possess high crystallinity, while their crystal sizes range from ∼100 nm to ∼2 μm. The effect of CTAB in the synthesis gel on the physicochemical properties, especially the crystal sizes, and the 1-butene skeletal isomerization performance of FER zeolites was investigated. The addition of CTAB has an obvious effect on the formation of FER zeolites, and the hydrophobic tail of CTAB can restrict the excessive growth of FER leading to the formation of highly crystallized FER with various crystal sizes. The nano-scale FER shows higher initial 1-butene conversion and better catalytic stability than micron-sized FER, which is mainly related to the superior accessibility of acid sites, larger external surface area, and less diffusion limitation due to the decrease of the crystal size. This novel synthesis strategy provides an effective way to regulate the size and performance of FER zeolites, and a new function of CTAB in the synthesis of zeolites is developed.