In situ and post-synthesis control of physicochemical properties of FER-type crystals

by Xiaoxin Chen, Totka Todorova, Alexandre Vimont, Valérie Ruaux, Zhengxing Qin, Jean-Pierre Gilson, Valentin Valtchev

DOI: 10.1016/j.micromeso.2014.07.057

Highlights

• FER-type zeolites were synthesized in three different initial systems.
• Seeds were used to decrease zeolite crystals size.
• Secondary pores in zeolite crystals were formed by etching with HF-NH4F solutions.
• Crystal morphology of obtained materials was studied.
• Physicochemical properties of zeolites were studied by complementary methods.

Abstract

FER-type zeolites were synthesized in the presence of Na-Ethylendiamine (Na-En), Na-Pyrrolidine (Na-Py) and Na-K. The crystallization times varied between 96 and 240 h. Ferrierite harvested from the Na-En synthesis was also used as seeds and reduced crystallization time from 240 to 30 h. The product of seeded synthesis was not uniform: nanosized with micronsized crystals as well as complex aggregates of different sizes were obtained. Hierarchical FER-type zeolites were prepared using seeded Na-En synthesized FER as a parent. Secondary pores in zeolite crystals were formed by etching at room temperature with HF-NH4F containing solutions, using the HF concentration and treatment time as variables. Crystal morphology and physicochemical characteristics of micron-, nano-sized and hierarchical FER-type crystals were studied by complementary methods including: X-ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetry (TG/dTG), 27Al and 29Si MAS NMR, IR spectroscopy of adsorbed probe molecules (Pyridine, Acetonitrile and Lutidine), nitrogen adsorption and chemical analysis. We demonstrate that FER-type zeolites with pre-determined properties can be easily prepared.

Keywords