Physicochemical and Structural Characterization of Mesoporous Aluminosilicates Synthesized from Leached Saponite with Additional Aluminum Incorporation

Abstract

A thorough investigation was performed on the physical (mechanical, thermal, and hydrothermal stability) and chemical (ion exchange capacity and silanol number) characteristics of aluminosilicate FSMs, synthesized via a new successful short-time synthesis route using leached saponite and a low concentration of CTAB. Moreover, the influence of an additional Al incorporation, utilizing different aluminum sources, on the structure of the FSM derived from saponite is studied. A mesoporous aluminosilicate with a low Si/Al ratio of 12.8 is synthesized, and still has a very large surface area of 1130 m2/g and pore volume of 0.92 cm3/g. The aluminum-containing samples all have a high cation exchange capacity of around 1 mmol/g while they still have a silanol number of about 0.9 OH/nm2; both characteristics being interesting for high-yield postsynthesis modification reactions. Finally, a study is performed on the transformation of the aluminosilicates into their Brønsted acid form via the exchange with ammonium ions and a consecutive heat treatment.