SO42-/Ti-M-O (M=Al, Fe, Sn) solid superacids were used in the esterifi
cation of phthalic anhydride with 2-ethyl hexyl alcohol. The catalytic
activity of SO42-/Ti-Al-Sn-O (1) is higher than SO42-/TiO2, and SO42-
/Ti-Al-O solid superacids. In the presence of(1) DOP is prepared in go
od yield at 175 degrees C over a period of 6 h. The acid strength, sur
face area and catalytic activity of SO42-/Ti-M-O are obviously affecte
d by the preparation conditions. Temperature-programmed desorption of
pyridine adsorbed on the catalyst was used to characterize the acid st
rength distribution of the catalysts. It was found that there were thr
ee kinds of acid sites (weak acid, middle acid and superacid) on SO42-
/Ti-Al-O, and the concentration of the middle-acid site on the catalys
ts is directly proportional to its catalytic activity for the esterifi
cation. Adding Al into SO42-/TiO2 could increase its surface area grea
tly.