Characterisation of the active sites in mixed oxides derived from LDH precursors by physico-chemical and catalytic techniques

Catalytic conversion of 4-methyl-pentan-2-ol (MPO) was investigated over oxidic materials obtained by the calcination of MgNiCuAl layered double hydroxide (LDH) precursors. Keeping constant the M2+/M3+ ratio equal to 2 (where M2+ = Mg2+, Cu2+, Ni2+ and M3+ = Al3+) various compositions of LDHs were prepared and characterised by X-ray diffraction (XRD), inductively coupled plasma (ICP), N2 adsorption/desorption and X-ray photoelectron spectra (XPS). The acid–base properties have been investigated by the means of physico-chemical methods such as microcalorimetry, by using ammonia (for acid sites) and carbon dioxide (for base sites) as probe molecules. The conversion of 4-methyl-pentan-2-ol (MPO) was chosen as test reaction to investigate the catalytic activity and selectivity of the oxidic materials obtained by the calcination of MgNiCuAl LDHs and to correlate them with the acid–base properties of the oxide surfaces. Copper was found to increase the alcohol dehydrogenation.

Catalytic conversion of 4-methyl-pentan-2-ol (MPO) was investigated over calcined MgNiCuAl layered double hydroxide precursors. The catalytic behaviour of the catalysts was related to their acid–base properties, which govern the competition between the dehydration over acid sites (giving 4-methylpent-1-ene, 4-methylpent-2-ene and, by isomerisation, resulting C6 alkenes) and the dehydrogenation over basic sites (giving 4-methylpentan-2-one and higher ketones by condensation) of the MPO (scheme). Copper was found to increase the alcohol dehydrogenation.Figure optionsDownload as PowerPoint slide