Synthesis of LTA zeolite based on natural minerals of Nakhchivan: the influence of various factors on the crystallization process

Abstract

The process of crystallization of LTA type zeolite promising for practical use has been studied, the influence of various factors on the rate and selectivity of synthesis using natural minerals from Nakhchivan has been considered. The influence of temperature in the range of 80 – 150 °C, the weight ratio of the initial components of halloysite (G) and obsidian (O) G:O, equal to 1:1, 1:2, 1:3, 2:1 and 3:1, the concentration of the used thermal NaOH solution in the range of 5 – 30 % and the process duration in the range of 10 – 100 hours for the crystallization of LTA were studied. It has been determined that the optimal conditions for the synthesis of a single-phase zeolite of the LTA type with 100 % crystallinity are: temperature 100 ± 10 °C, concentration of thermal NaOH solution — 10 – 15 %, the ratio of the initial components of halloysite (G) and obsidian (O) G:O, equal to 1:1, processing time — 20 hours. Synthesis of zeolite LTA using natural minerals of Nakhchivan was carried out in the presence of tetramethylammonium hydroxide (TMAOH). The effect of temperature, concentration of thermal NaOH solution, ratio of initial components, duration of aging on the process of LTA crystallization has been studied. It was shown that violation of the optimal synthesis conditions leads to a decrease in the selectivity of the process and the formation of other zeolites (X), aluminosilicates (sodalite, anorthite, sanidine) or their associations, as well as quartz. The process of aging was studied in the duration interval from 1 to 3 days. It has been determined that an increase in the aging duration leads to an increase in the linear rate of crystallization of the LTA zeolite.