Hydrothermal synthesis of zeolite T from kaolin using two different structure-directing agents

Abstract

Zeolite T was synthesized from the molar chemical composition of 1SiO2:0.04Al2O3:0.26Na2O:0.09K2O:14H2O in the form of a homogenous milky solution in the presence of the two different structure-directing agents TMAOH and TEAOH respectively. Modification of the composition of silica was undertaken using metakaolin from calcined kaolin at 750 °C for 4 h, while the molar composition of each different SDA was variated from 0.05, 0.10, 0.15, 0.20 and 0.25. The homogenous mixture was left at room temperature for 24 h before undergoing hydrothermal synthesis at 100 °C for 168 h. The synthesized samples were filtered and aged at 120 °C for 2 h and each sample was calcined at high temperatures (545 °C for TMAOH and 520 °C for TEAOH) for template removal before characterization using XRD and SEM. Crystallization of the zeolite T in its major form only took place at a molar ratio of 0.10 of TMAOH, while TEAOH showed the species evolution of zeolite T into zeolite L and W for other molar ratios.

Important Synthesis Parameters Affecting Crystallization of Zeolite T: A Review

“…Meanwhile, crystal formation of zeolite T (either by hydrothermal synthesis or aided with microwave-, or sonochemical-irradiation) is affected by several primary factors. From the past and recent literature, several cases involve crystals' behavior upon several factors, namely SiO 2 /Al 2 O 3 ratio, alkalinity (n (OH)-)/n (SiO 2 )), water ratio, synthesis temperature and crystallization time, and the addition of structure-directing agents (SDA) [1,3,4,8,16,[19][20][21][22], while pressure is not directly involved in zeolite T synthesis [23]. This review summarizes the factors that affect the growth of zeolite T. However, the ratio of SiO 2 /Al 2 O 3 depends on the alkalinity of the composition.…”

“…Moreover, SDA can accelerate the nucleation and crystallization phase. As an example, for TMAOH, the hydroxide anion within it will provide the necessary alkalinity to facilitate the formation of anionic silicates, thus expediting the rate of dissolution of silicate and aluminate [3,7,20,21,28,30]. Additionally, the authors in [7] reported that providing an abundant amount of SDA will create high supersaturation conditions and steric stabilization of proto-nuclei, which are the critical factors in forming zeolite nanoparticles without aggregation [30].…”

“…Additionally, the authors in [7] reported that providing an abundant amount of SDA will create high supersaturation conditions and steric stabilization of proto-nuclei, which are the critical factors in forming zeolite nanoparticles without aggregation [30]. Determination of the exact amount of SDA needed in synthesizing zeolite, especially ERI-type zeolite, is crucial because erionite (ERI) intergrowth crystals will not form effectively if the system contains a large amount of cation [7,13,20,21].…”

Comparative study using different external sources of aluminum on the zeolites synthesis from rice husk ash

“…The zeolite's cation exchange capacity is related to its Si/Al ratio [46]. There are approximately forty natural occurrences of zeolites, and some of them are analcime, chabazite, clinoptilolite, erionite, faujasite, ferrierite, heulandite, laumontite, mordenite and phillipsite [47,48]. Natural zeolites have impurities that limit their application, as a result people have begun to synthesize zeolites for academic as well as industrial purposes [46].…”

Preparation of 13X zeolite powder and membrane: investigation of synthesis parameters impacts using experimental design

“…A large number of variables can affect the synthetic zeolites crystallinity and phases' purity, i. e., synthesis procedure, SiO 2 /Al 2 O 3 molar ratio, synthesis solution alkalinity (H 2 O/Na 2 O) and water content (H 2 O/Al 2 O 3 ), synthesis temperature (T R ,°C) and time (t R , h), aging time (t A , h), template (if any) and seeding [20][21][22].…”