Abstract
A series of Ru/Al 2O 3 catalysts were prepared by the sol–gel method using water/alkoxide ratios, h, of 1, 2, 3, 6 and 9. An increase in h resulted in (i) total BET surface area (149 to 426 m 2 g −1), (ii) particle size (SEM) distribution (1.3/1.7 mm to 0.05/0.14 mm) and (iii) pore characteristic (pore distribution, volume, size and shape) changes. Indeed the pore volume was found to increase linearly with h. Low h values ( h<3) produced compact gel precipitates that had comparatively lower surface areas while better hydrolysis ( h>3) gave rise to more porous gels with larger surface area and finer texture. Alumina crystallinity as well as ruthenium reducibility of calcined samples (773 K) were largely unaffected by h. XRD spectra revealed the presence of RuO 2 after calcination. There was a significant effect on the percent weight loss (50 to 60%) of the samples on heating for h<3. The characterisation results show that the degree of hydrolysis can control the properties of Ru/Al 2O 3 catalysts in a predictable manner.
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