Synthesis and characterization of BEC-zeotype germanosilicates and B-substituted zeolitic materials

摘要

Pure BEC-type germanosilicates (denoted as SiGe-BEC) and B-containing BEC-zeotype (denoted as B-BEC) materials were synthesized by the hydrothermal method in the presence of an organic structure-directing agent, N,N,N',N'-Tetra-methylethylenediamine. The effects of the reaction mixture ratio and the incorporation of transition boron on the synthesis of the pure product were investigated. The synthesized samples were characterized by powder and single-crystal X-ray diffraction, scanning electron microscopy, inductively coupled plasma analysis, thermogravimetric analysis, and nitrogen sorption measurements. The results reveal that the crystallization time, the concentration of H2O in the reaction mixture and the addition of HF have an important impact on the synthesis of BEC-type zeolite. It was also determined that Ge atoms occupy only the T sites in the D4Rs units. BEC material in the germanosilicate form is stable up to 800 A degrees C and boron can successfully be introduced into the BEC-type (denoted as B-BEC) framework.