NCL-7, A novel all silica analog of polymorph B rich member of BEA family: Synthesis and characterization

Abstract

Polymorph B-rich BEA type structure, NCL-7, was synthesized using hydrothermal method in fluoride medium using perchloric acid as promoter. The samples were characterized using XRD, low temperature N2-adsorption and 29Si MASNMR. As the structure of beta is highly disordered Rietveld refinement of powder XRD patterns is precluded. Phase composition is derived using the simulated patterns for the random intergrowths of polymorph A and B by DIFFaX. The stacking direction c0 is perpendicular to the a0b0 plane of the layer. The composition of polymorph B is found to be ca. 60–65%. Two other structures namely NCL-5 and NCL-6 with varying degree of polymorph B enrichment were also synthesized. Synthesis parameters such as effect of H2O/SiO2, TEAOH/SiO2, HClO4/SiO2 and crystallization temperature were studied thoroughly. The present article explains for the first time the synthesis and characterization of NCL- 7, an analog of BEA type family with enrichment of polymorph B and its comparison with normal beta (*BEA).