Abstract
Abstract The rates of crystallization of zeolite ZSM-5 from a reaction mixture containing small amounts of ZSM-5 seed crystals and organic solvents such as acetone and 1,4-dioxane (i.e., ( a = 0.10–0.20)Na 2 O-( b = 0.005–0.02)Al 2 O 3 -SiO 2 -46H 2 O-0.7 (orga nic solvent)-seed system; a and b values indicate the molar Na 2 O/SiO 2 and Al 2 O 3 /SiO 2 ratios, respectively) were investigated. The crystallization of ZSM-5 began immediately after the addition of the seed crystals without any induction period. The degree of crystallization and the uniformity of the crystal shape and size were advanced with the addition of the organic solvent. After the start of the crystallization of ZSM-5, it decomposed and the more stable phase, α-quartz, was subsequently crystallized, depending on the composition of the reaction mixture. The apparent activation energies for ZSM-5 crystal growth were 76 ( a = 0.15) and 42 ( a = 0.02) kJ mol -1 for the acetone mixed system, and 71 ( a = 0.15) and 45 ( a = 0.20) kJ mol -1 for the 1,4-dioxane mixed system. The accelerated crystallization of ZSM-5 with the addition of an organic solvent is thought to be caused by the increased fluidity of the reaction mixture thus increasing also the diffusion rate of the ZSM-5 species.
Published Version
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