Sínteses das zeólitas ZSM-12: avaliação de parâmetros e seus efeitos na cristalização

Abstract

Zeolites are aluminosilicates, crystalline, microporous minerals with special properties that allow their application as catalysts, adsorbents and ion exchangers in the chemical and petrochemical industry. Organic structure-directing agents (OSDAs) are generally avoided in synthesis of commercial zolites due to economic and environmental factors. Studies are carried out with the aim of finding a more economical and viable route for industrial scale production. Many parameters influence the crystallization of zeolites, among which: reagent molar fractions (silica, alumina, alkali metal and alkaline earth hydroxides); water content; temperature; time and use of crystallization seeds. ZSM-12 (MTW) synthesis was studied through conventional (hydrothermal) methodology at different temperatures, aluminum sources and inorganic cations (Li+ and Na+). In order to optimize this synthesis methodology and reduce the content of the organic structure agent directing MTEACl (methyltriethylammonium chloride) crystallization seeds were inserted during preparation of the gel, varying the MTEACl content and relating Li+ And Na+ as compensation cations in order to achieve shorter crystallization times and lower production costs at a temperature of 170 °C. The zeolites synthesized were characterized by X-ray diffraction (XRD), N2 adsorption (BET method), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and thermal analysis (TG / DTA). The ZSM-12 zeolite was obtained with high purity and crystallinity in 24 h of synthesis at 170 ºC. The ZSM-12 zeolites obtained with addition of seeds, reduction of the organic structure-directing agent and addition of Li+, allowed lower synthesis times at 170 ºC than those reported in the literature. By the X-ray diffraction analysis and the Rietveld method, the network parameters of the ZSM-12 zeolite structures confirm their purity and crystallinity.