clay interlayers is too narrow to accommodate large molecules such as capric acid, resulting in apparent poor activity of the photocatalyst. Studies to confirm this idea are under way.

The changes occurring in SAPO-37 upon heating it to 1273 K are studied using 29Si, 27AI and 31P magic-anglespinning nuclear magnetic resonance (MAS NMR), X-ray diffraction (XRD) and infrared spectroscopy. The removal of the template at 873 K leads to a shift of both 29Si and 27AI MAS NMR peaks, suggesting an interaction of the template with some SiO, and AIO, tetrahedra. A further solid-state transformation is shown to occur between 1073 and 1173 K. This involves the formation of siliceous islands, generating silicoaluminate domains. The faujasite crystal structure is maintained. At 1273 K the material is fully transformed to a mixture of tridymite and cristobalite structures. A model is proposed for the migration of atoms in the framework.

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