Catalysts were prepared via the sol–gel route illustrated
in Fig. 1. The precursor was titanium(IV)
butoxide (Ti(OC4H9)4, 97% in n-butanol), as purchased
from Aldrich (USA). The hydrolysis process
was performed in a glove box maintained at a relative
humidity under 25% by purging with tank nitrogen.
To avoid rapid precipitation during polycondensation
and the formation of unstable colloidal sols, the
hydrolyzing water was homogeneously released by
the esterification of butanol and acetic acid [5]. The
basic aim was to provide the appropriate stoichiometric
quantity of water to hydrolyze titanium butoxide
during hydrolysis. A typical batch contained 0.02 mol
titanium butoxide, 0.08 mol anhydrous butanol (minimum
99.8%) and 0.08 mol glacial acetic acid (minimum
99.7%). The clear solution was stirred for 8 h
at which time the pH value became stabilized. The
final pH value of the solution approached 3.56. The
transparent sol was dried from room temperature to
150 ◦C in an oven, then transferred to a furnace and
calcined at 500 ◦C to burn off hydrocarbons. The sample
was crushed into powder in a mortar. The JRC-2
and P25 titania powders were obtained from Fuji Titan
(Japan) and Degussa (Germany), respectively, for
comparison. Copper-loaded titania (Cu/TiO2) and P25
(Cu/P25) were impregnated by adding CuCl2 during
the sol–gel process and incipient wetness method,
respectively. Following calcination similar to that of
TiO2, Cu-loaded titania was reduced under a flow of
5% H2/Ar mixture at 300 ◦C for 3 h.