Synthesis of BEA by dry gel conversion and its characterization

Zeolite BEA with SiO₂/Al₂O₃ ratios ranging from 30 to 740 were crystallized at 413 and 453 K by the dry gel conversion technique. The particle size of the products increased with increasing SiO₂/Al₂O₃ ratio as well as with increasing crystallization temperature. In as-synthesized BEA, the TEA⁺ ions interacting with Si-O^- decomposed between 473 and 673 K and those interacting with Al-O^- were cleaved between 673 and 798 K. During their elimination, the TEA⁺ ions interacting with Al-O^- underwent higher degradation than those interacting with Si-O^-. Chemical compositions showed the least influence on the fractions of decomposition product during the elimination between 473 and 673 K. The framework of H-BEA and NH₄-BEA zeolites with SiO₂/Al₂O₃ ratios ranging from 400 to 740 were stable even at 1373 K, whereas H-BEA with SiO₂/Al₂O₃ = 30 was stable only up to 1173 K and became amorphous when calcined at 1373 K. After calcination at 1373 K, Na-BEA with SiO₂/Al₂O₃ = 400 and 730 were transformed to tridymite (dense phase) whereas that with SiO₂/Al₂O₃ = 30 became amorphous. The elimination of Na⁺ ions is necessary to have a BEA remain stable above 1173 K.