Evaluation of different reaction systems to obtain zeolite 4A via reverse microemulsion

Abstract

Abstract Zeolites are crystalline hydrated aluminosilicates with defined morphology and pore size. These are technologically important materials applied in several processes, including the treatment of toxic and hazardous waste. Known as molecular sieves, zeolites can also be used as catalytic agents and ion exchangers. Among the various types of zeolitic syntheses, a noteworthy technique is the synthesis via reverse microemulsion, in which nanometric droplets of water dispersed in oil can act as nanoreactors. Thus, given the importance of obtaining zeolites with specific crystal pore size control and morphology, this research focused on the synthesis of 4A zeolite via reverse microemulsion using an anionic surfactant. In order to assess the optimal conditions for the synthesis, two experimental designs with different combinations were used, along with two methods of dispersion: mechanic and ultrasonic shaking. The variables tested were: Si/Al ratio (1.9, 2.2 and 2.4); temperature (60 °C, 70 °C and 75 °C); time span (6h, 7h and 8h). The products were characterized using XRD, FTIR, TG/DTA, SEM, TEM and BET analysis. In 70% of the experiments, high degrees of crystallization were obtained for both dispersion methods. For the mechanic shaking, the most important variables were Si/Al ratio and crystallization temperature. For the ultrasonic shaking method, higher Si/Al ratios stemmed similar results, although, under longer reaction time, lower Si/Al ratios resulted in higher crystallization.