AL-PILLARED MONTMORILLONITE - PREPARATION FROM CONCENTRATED SLURRIES OF HOMOIONIC CA CLAY, CHARACTERIZATION AND THERMAL-STABILITY

Montmorillonites intercalated with Al polyoxocations are examples of pillared interlayered clays (PILCs) and have a lamellar structure with ''oxide pillars grafted'' on the clay layers. A rigid frame can be produced with constant d(001) spacings meaning that the pillars have the same ''length'' and, therefore, slit-like pores have a constant ''height''. A method of PILC preparation with concentrated slurries is reported. The PILCs produced are compared with those obtained from diluted clay suspensions. d(001) spacings and nitrogen BET specific surface areas were measured after heating the PILCs in air at 823, 923, 1023 and 1073 K: d(001) spacings were constant up to 923 K (1.7 nm) and the specific surface area diminished from ca. 370 m2/g at 823 K to ca. 90 m2/g at 1023 K. At 1073 K the structure collapsed with a specific surface area from 8 to 27 m2/g depending on the preparation method.