Effects of gel parameters on the synthesis and characteristics of W-type zeolite nanoparticles

The objectives of this study were to investigate the effects of chemical parameters on the characterizationof W-type zeolite crystals and their intergrowths with other types of zeolites. The crystal size and purity ofW-type zeolites are affected significantly by the gel composition with respect to the molar ratios of SiO /Al O (aluminosilicate module, α),H O/K O (alkainity, β), and water content (H O/SiO , γ). The effects of these gel parameters ont he synthesis and characterizationof W-type zeolite were investigated. Crystalline W-type zeolite of high purity was synthesized using a gel with a molar ratio of Al O :6.4SiO :5.6K O:164.6H O at T = 165°C for a period of 72 h. The effect of excess K O/SiO ratio ina mono-cation (K)-SiO -Al O gel-composition system on the nanoparticle size and purity of the product was also investigated. Experiments were carried out using the following levels of alkalinity: 21.4, 29.4, and 51.9; aluminosilicate module: 5.0, 6.4, and 10.0; water content: 16.5, 25.7, and 32.9; and excess K O/SiO ratio: from 0.65 to 3.33. The results showed that by increasing the aluminosilicate module at high K O/SiO ratio, the crystallinity and crystal size of the zeolite synthesized increased, while at low alkalinity, the crystallinity and crystal size decreased. Decreasing alkalinity at low aluminosilicate module increased the crystallinity and decreased the crystal size, while at high aluminosilicate module, both decreased. Finally, by increasing the water content at all aluminosilicate module and alkalinity values, the crystallinity and crystal size of the W-type zeolite increased. Excess K O/SiO ratio was the key factor that should be adjusted int he range 0.7-1.0 for synthesis of pure crystals of W-type zeolite