2. Experimental
2.1. Synthesis of novel titania–silica pellets
Titania–silica pellets were made from titanium alkoxide and
tetraethylorthosilicates (TEOS) using the sol–gel method. There
are two steps involved to prepare TiO2/SiO2. The first stage
involved the hydrolysis of Ti(OC4H9)4 to form the uniform sol.
Titanium butoxide was diluted by ethanol with small amount of
HCl to form yellowtransparent colloid. Then deionedwater with
small amount of hydrochloric acid dropped into above colloid
solution. The molar ratio of Ti(OC4H9)4:C2H5OH:H2O:HCl is
1:15:10:0.89. It is then left to stand by at room temperature for
gelation. The second stage is that TEOS were hydrolysed under
the molar ratio of TEOS:C2H5OH:H2O:HCl = 1:7.6:25:0.28 and
added into the above TiO2 sol to form transparent TiO2/SiO2 sol
mixture. The transparent mixture gel can be obtained after drying
at 60 ◦C in an oven. Further drying at 105 ◦C was performed to
form xerogel. Finally, the xerogel was sintered at 540 ◦C in a
furnace to obtain titania–silica pellets.