Zr-La Doped Sulfated Titania with a by Far Better Catalytic Activity and Stability than Pure Sulfated Titania in the Esterification of Acetic Acid and w-Butanol

摘要

A novel solid superacid catalyst TiO2-Zr-La/ SO4~(2-) was prepared by doping Zr and La to the bulk of TiO2. The modified TiO2-Zr-La/SO4~(2-) and the unmodified TiO2/SO4~(2-) were used to catalyze the esterification of acetic acid and n-butanol, in which these two catalysts were systematically compared in a lost of aspects such as catalytic activity and stability and so on. When a small amount of Zr and La were co-doped into the bulk of TiO2, the modified catalyst obtained a by far better catalytic activity and stability than the unmodified, showing that the modified is more resistive to deactivation than the unmodified. Under the set reaction conditions, the average conversion (of acetic acid) and the 20th-cycle conversion (of acetic acid) are 88.83 and 77.35 % for the modified, 80.83 and 46.15 % for the unmodified, respectively. The two catalysts were characterized by means of FTIR, XRD, BET, SEM, TG, and NH3-TPD methods to find the possible reasons for the superiority of the modified catalyst to the unmodified one. The characteristic results indicated that the incorporation of a small amount of Zr and La into the catalyst was beneficial to the modified catalyst: (1) improving its water-tolerance; (2) increasing its surface sulfate group content; (3) decreasing its crystallinity after calcination by retarding its crystallization from amorphous TiO2 to anatase TiO2; (4) increasing its specific surface area; (5) increasing its acidity including the concentration and acid strength of the surface acidic sites of it. All the above advantageous effects arisen from the two-element- doping are to be responsible for the substantially-improved catalytic performances of the modified catalyst.