Mg. Cutrufello et al., CeO2-La2O3 catalytic system - Part II. Acid-base properties and catalytic activity for 4-methylpentan-2-ol dehydration, PHYS CHEM P, 3(14), 2001, pp. 2928-2934
CeO2-La2O3 mixed oxides, formerly prepared via a sol-gel procedure and char
acterised by several techniques, have been further investigated as to their
acid-base properties and catalytic activity. Surface acidity and basicity
have been assessed by adsorption microcalorimetry, using ammonia and carbon
dioxide as probe molecules. Catalytic activity for 4-methylpentan-2-ol deh
ydration has been tested at atmospheric pressure in a fixed-bed flow micror
eactor. The acid and base features of the catalysts markedly depend on the
relative amounts of the two component oxides. For pure ceria, cerium and ox
ygen ions are the source for acidity and basicity, respectively. Some contr
ibution of OH groups to the acid-base character is probable for the mixed o
xides. Most of the acid sites of each catalyst are weak, whereas most of it
s base sites are strong. The concentration of the base sites tends to preva
il over that of the acid sites as the lanthanum content increases. 4-Methyl
pent-1-ene is by far the most abundant product of 4-methylpentan-2-ol conve
rsion for all the catalysts, which are quite stable, even after repeated op
eration cycles. Subtle differences in the relative extents of dehydration a
nd dehydrogenation activity seem to be due to a shift in the reaction mecha
nism, originated by changes in the relative amounts of acid and base sites.