Trimeric chromium oxyformate route to chromia-pillared clay

A chromia-pillared clay has been prepared by ion exchange type intercalatio n reaction between the sodium ion in montmorillonite and the trimeric chrom ium oxyformate (TCF) ion, and by subsequent heat-treatment. The structural and thermal properties have been systematically studied by thermal analysis , powder XRD, LR spectroscopy, and XAS. The gallery height of similar to6.8 Angstrom upon intercalation of the TCF ion suggests that the Cr3O plane is parallel to the aluminosilicate layers. Even though the basal spacing of T CF intercalated clay decreases slightly upon heating, the layer structure w as retained up to 550 degreesC as confirmed by XRD and TG/DTA. According to the EXAFS spectroscopic analysis, it is identified that the (Cr-Cr) distan ce of 3.28 Angstrom between vertex-linked CrO6 octahedra in TCF splits into 2.64 Angstrom, 2.98 Angstrom, and 3.77 Angstrom due to the face-, edge-, a nd comer-shared CrO6 octahedra after heating at 400 degreesC, implying that a nano-sized chromium oxide phase was stabilized within the interlayer spa ce of clay.