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The 13X molecular sieve, a faujasite zeolite with a cubic structure and ~10 A pore size, is vital in industrial gas separation, water purification, and petrochemicals. Its synthesis involves raw material selection, mixing, aging, crystallization, and post-treatment.
First, prepare the reaction mixture using silica (e.g., sodium silicate), alumina (e.g., aluminum sulfate), sodium hydroxide, and template agent (e.g., TPAOH). Critical molar ratios (SiO₂/Al₂O₃=2.5-3.0, Na₂O/SiO₂=0.3-0.4, H₂O/SiO₂=100-200, TPAOH/SiO₂=0.1-0.2) ensure pure 13X phase formation.
Aging for 2-4 hours at room temp stabilizes the precursor and promotes uniform nucleation, essential for crystallization.
Next, crystallization in autoclaves at 100-150°C for 24-72 hours transforms the gel into 13X crystals. pH (12-13) and conditions control particle size, crystallinity, and pore structure.
Post-crystallization: filter, wash with deionized water, dry (100-120°C, 12-24h), then calcine (500-600°C, 4-6h) to remove templates, forming porous sieves.
Key factors: template choice (TPAOH guides faujasite), SiO₂/Al₂O₃ ratio (higher ratios boost stability), and crystallization parameters (temp/time for yield/purity).
In industry, 13X sieves act as packing in columns, with structures (spheres, cylinders) enhancing surface area and flow. tower internals like distributors optimize mass transfer.
Overall, precise control of raw materials, aging, crystallization, and post-treatments yields high-quality 13X sieves, supported by packing and tower internals for efficient separation.
