Synthesis of low-silica X-zeolite (LSX) via crystallization directing agent under aging at room temperature

Low-silica X zeolite (LSX) with the molar ratio 2.0 of SiO₂ to Al₂O₃ was prepared by introducing the crystallization directing agent (CDA) under aging at room temperature(15-30℃)and crystallizing at 100-110℃. The crystal structure of LSX was characterized by XRD. The effect of CDA (17Na₂O·6SiO₂·Al₂O₃·250H₂O) on the crystallization of LSX was studied. The results showed that the additive of CDA aged for 5 h could inhibit from impurity hydroxysodalite (HS) in LSX, but could not speed up the rate of crystallization. The study on the ratio of raw material showed that the purity of LSX was greatly influenced by the changes in molar ratio of H₂O/(Na₂O + K₂O) and Na₂O/(Na₂O + K₂O). The crystallinity of product LSX raised with increasing reaction temperature and aging time. The fine purity and crystallinity of the product could be obtained when aging for 12 h at room temperature (25-30℃) and crystallizing for 3 h at 110℃, and the molar ratio Si/Al of product LSX was 1.02±0.03.