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Zeolite LTA synthesis: Optimising synthesis conditions by using the modified sequential simplex method
Síntesis de Zeolita LTA: optimización de las condiciones de síntesis, usando el método simplex secuencial modificado
Keywords:
LTA zeolite, crystallinity, simplex method, optimisation (en)Zeolita LTA, cristalinidad, método simplex y optimización (es)
This paper presents research concerning the simultaneous effect of the most influential synthesis variables in the preparation of Zeolite LTA. The simplex method was used for ascertaining optimal synthesis conditions, where the relative crystallinity (regarding a commercial sample) of synthesised zeolite was defined as response function. Crystallinity was measured by X-ray diffraction. Optimum conditions were found after 24 trials, giving 95.4% relative crystallinity and Na2O/SiO2=2.58, SiO2/Al2O3=1.45 and H2O/Na2O=46.92 molar ratios; 11.7 h crystal growth time, 6.1 h crystallisation time (reaction) and 78oC reaction temperature were found to be optimal synthesis conditions. A computer programme for simulating a zeolite phase diagram was designed to verify whether the molar ratios indicated by the optimisation algorithm were leading to the desired zeolite type. The results were compared to those in previous work where the fixed factor method was used.
Este artículo presenta un estudio del efecto simultáneo de las variables de síntesis más significativas en la obtención de Zeolita LTA. Se aplicó el método simplex modificado para determinar las condiciones óptimas de síntesis, definiendo como función y objetivo la cristalinidad relativa de la zeolita obtenida y evaluada mediante la difracción de rayos X. Se requirieron 24 ensayos para que el método convergiera de manera óptima, logrando así, una cristalinidad de 95,4 %, obtenida para las relaciones molares Na2O/SiO2=2,58, SiO2/Al2O3=1,45 y H2O/Na2O=46,92, condiciones de operación de 11,7 h de maduración, 6,1 h de cristalización y 78oC de temperatura de reacción. Se diseñó un programa de computador para simular el diagrama de fases zeolíticas, el cual indicaba si las relaciones molares propuestas por el algoritmo de optimización conducían a la zona de obtención de la zeolita deseada. Los resultados obtenidos, aplicando el método simplex, fueron comparados con un trabajo previo en el que se usó el método de una variable fija en el tiempo.
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