Synthesis and characterisation of chromium-substituted ETS-10

A series of microporous chromium-containing ETS-10 (ETCrS-10) with differen t Cr/Ti molar ratios have been synthesised and characterised by energy disp ersive absorption of X-rays (EDAX), powder X-ray diffraction (XRD), scannin g electron microscopy (SEM), N-2 adsorption measurements, diffuse-reflectan ce ultraviolet spectroscopy (DR-UV), electron paramagnetic resonance (EPR) and Si-29 magic-angle-spinning nuclear magnetic resonance (MAS NMR). The di ffractograms of the as-synthesised ETCrS-10 materials indicate that the ETS -10 structure has remained intact upon Cr substitution. DR-UV and EPR revea l that the as-prepared ETCrS-10 samples contain Cr3+ in octahedral coordina tion. The resonances in the Si-29 MAS NMR spectra of ETCrS-10 are considera bly broader than those of ETS-10 and such a broadening may relate to isomor phous substitution of Cr for Ti in the ETS-10 framework. The acid-base prop erties of ETCrS-10 materials are responsible for the high dehydrogenation a ctivity in the conversion of isopropanol to acetone and dehydration activit y in the conversion of tert-butanol to isobutene. Ethanol oxidation over ET CrS-10 yields acetaldehyde as a main product.