Ni-based xero- and aerogels as catalysts for nitroxidation processes |
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Authors: | Maria Giorgia Cutrufello Elisabetta Rombi Italo Ferino Danilo Loche Anna Corrias Maria Francesca Casula |
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Institution: | 1.Dipartimento di Scienze Chimiche and INSTM,Università di Cagliari,Monserrato,Italy |
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Abstract: | Porous nanocomposites made out of nickel dispersed on silica or alumina matrices were prepared as prospective catalysts for
the nitroxidation of hydrocarbons in the form of aerogel or xerogel by adopting either a supercritical or a conventional gel
drying procedure. The structural and textural features of the materials were investigated by X-ray diffraction, transmission
electron microscopy and N2 physisorption and combined to the acid/base and reducibility data as deduced by adsorption microcalorimetry and temperature
programmed reduction (TPR) profiles. The alumina-based samples are made out of nanocrystalline nickel aluminate and are mesoporous,
although the aerogel has larger pore volumes and surface area than the xerogel. On the other hand, in the silica-based samples
nickel oxide nanocrystals are dispersed on amorphous silica, the size of the nanocrystals being around 5 nm in the microporous
xerogel and 14 nm in the mainly mesoporous aerogel. TPR data point out that the alumina-based samples have similar reducibility,
whereas significant differences were observed in the silica-supported composites, the NiO–SiO2 aerogel exhibiting improved reducibility at low temperature. The NO-catalyst interaction was monitored by temperature programmed
NO reaction coupled to mass spectrometry and preliminary tests on the use of the NiO–SiO2 xerogel and aerogel nanocomposites for the catalytic nitroxidation of 1-methyl-naphthalene to 1-naphthonitrile were obtained
in a fixed-bed continuous-flow reactor. The data indicate that the aerogel exhibits larger selectivity than the corresponding
xerogel, pointing out the importance of tuning the sol–gel parameters in the design of porous composite materials for catalytic
applications. |
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