Arla Kytökivi

IR and 1H NMR studies on the adsorption of gaseous hydrogen chloride on γ-alumina

The reaction of HCl at 100–600 °C with γ-alumina preheated at 200–600 °C has been studied at various reaction times by a combination of FTIR and 1H MAS NMR. The two primary reactions considered were the exchange reaction with hydroxy groups and the dissociation reaction of HCl. The evolution of water in the exchange reaction and subsequent rehydration were taken into account. The results showed that the exchange reaction occurred under all conditions, with the basic OH groups being more reactive. The dissociation reaction increased in importance at lower reaction temperatures, as did the secondary reaction of evolved water. It is suggested that the exchange reaction occurred with isolated OH groups rather than with associated ones. The new OH groups formed from the dissociation of water appeared to be acidic in nature.

Processing of catalysts by atomic layer epitaxy : modification of supports

Abstract Different supports were modified with titania, zirconia and chromia by the atomic layer epitaxy technique (ALE). In ALE, a metal precursor is bound to the support in saturating gas-solid reactions. Surface oxides are grown by alternating reactions of the metal precursor and an oxidizing agent. Growth mechanisms differ depending on the precursor-support pair and the processing conditions. In this work, the influences of the support, precursor and reaction temperature were investigated by comparing the growth of titania from Ti(OCH(CH 3 ) 2 ) 4 on silica and alumina, titania from TiCl 4 and Ti(OCH(CH 3 ) 2 ) 4 on silica, and zirconia from ZrCl 4 on silica and alumina. The modification of porous oxides supported on metal substrates (monoliths) was demonstrated for the growth of chromia from Cr(acac) 3 .

Reaction of acetylacetone vapour with [gamma ]-alumina

Acetylacetone (pentane-2,4-dione, Hacac) has been adsorbed on preheated γ-alumina support from the gas phase at 200 and 270°C. In the surface reactions, formation of Al(acac)x, acetates and 3,5-dimethylphenol was observed using diffuse reflectance IR Fourier transform (DRIFT) and 13C cross-polarization magic angle spinning (CP MAS) NMR spectroscopy. The main products released in the reactions were acetone and water, as monitored by on-line gas-phase FTIR spectroscopy. Leaching of aluminium as Al(acac)3 was observed.