Effects of Synthesis Parameters on Crystallization Behavior of K-MER Zeolite and Its Morphological Properties on Catalytic Cyanoethylation Reaction

Abstract

MER-type zeolite is an interesting microporous material that has been widely used in catalysis and separation. By carefully controlling the synthesis parameters, a procedure to synthesize K-MER zeolite crystals with various morphologies has been developed. The silica, water and mineralizer content in the synthesis gel, as well as crystallization time and temperature, have a profound impact on the crystallization kinetics, resulting in zeolite solids with various degrees of crystallinity, crystal sizes and shapes. K-MER zeolite crystals with nanorod, bullet-like, prismatic and wheatsheaf-like morphologies have been successfully obtained. The catalytic performances of the K-MER zeolites in cyanoethylation of methanol, under novel non-microwave instant heating, have been investigated. The zeolite in nanosize form shows the best catalytic performance (94.1% conversion, 100% selectivity) while the bullet-like zeolite gives poorest catalytic performance (44.2% conversion, 100% selectivity).

Effects of Thermal Treatment on Natural Clinoptilolite-Rich Zeolite Behavior in Simulated Biological Fluids

“…Zeolites are crystalline aluminosilicates with three-dimensional open frameworks built by SiO 4 and AlO 4 tetrahedra linked by oxygen bridges and orderly distributed intracrystalline cavities, molecular sizes micropores, or pore channels. Generally, the framework structure (Si:Al ratio) together with the crystal shape and size determine the physical and chemical properties of zeolites [1]. The Structure Commission of the International Zeolite Association (IZA) categorizes zeolites based on the Si:Al ratio into low silica zeolites (Si:Al molar ratio = 1-2; SiO 2 :Al 2 O 3 mass ratio = 1.18-2.35), medium silica zeolites (Si:Al molar ratio = 3-10; SiO 2 :Al 2 O 3 mass ratio = 3.53-11.76), and high silica zeolites (Si:Al molar ratio > 10; SiO 2 :Al 2 O 3 mass ratio > 11.76).…”

“…The Structure Commission of the International Zeolite Association (IZA) categorizes zeolites based on the Si:Al ratio into low silica zeolites (Si:Al molar ratio = 1-2; SiO 2 :Al 2 O 3 mass ratio = 1.18-2.35), medium silica zeolites (Si:Al molar ratio = 3-10; SiO 2 :Al 2 O 3 mass ratio = 3.53-11.76), and high silica zeolites (Si:Al molar ratio > 10; SiO 2 :Al 2 O 3 mass ratio > 11.76). Zeolites with a low Si:Al molar ratio are hydrophilic, while zeolites with a high Si:Al ratio are hydrophobic [1][2][3].…”

“…The chemical and thermal treatments are the most used techniques to modify the zeolite's characteristics by controlling their structural and morphological properties [1,4,8]. These treatments allow the removal of impurities; the enhancement of sorption properties, surface area, and porosity; and also determine important crystallinity loss [8].…”

Advances in Industrial Crystallization

“…The latter might be caused by lattice defects at the crystal surface and crystallization conditions like temperature, supersaturation, impurities present, stirrer energy introduced, and hydrodynamic conditions in general [2,4,5,14]. Hence, there is a need for prediction or empirical study of crystal shape development, an issue that is considered in the Special Issue articles [15][16][17]. It can be shown for numerous substances that the crystal environment is decisive for the morphology, after the process [15], but the fundamental mechanisms [16] are still not completely clarified and there is a great demand for predictive tools [17] for the process design.…”

“…Hence, there is a need for prediction or empirical study of crystal shape development, an issue that is considered in the Special Issue articles [15][16][17]. It can be shown for numerous substances that the crystal environment is decisive for the morphology, after the process [15], but the fundamental mechanisms [16] are still not completely clarified and there is a great demand for predictive tools [17] for the process design. iii.…”