Preparation, characterization and catalytic properties of S2O82−/ZrO2-CeO2 solid superacid catalyst

A novel solid superacid catalyst S2O82–/ZrO2-CeO2 was prepared by a coprecipitation method and characterized by means of XRD, FTIR, BET, TEM and DSC/TG analysis methods. The results indicated that incorporation of appropriate amounts of Ce into the catalyst was beneficial to the formation of sole tetragonal ZrO2 and effectively prevented from the formation of monoclinic ZrO2, and restrained the loss of sulfated species. XRD revealed the presence of tetragonal Ce0.16Zr0.84O2 phase in the case of S2O82–/ZrO2-CeO2 calcined above 500 °C. Catalytic activities of S2O82–/ZrO2-CeO2 for the esterification of lactic acid with n-butanol was studied. The results showed that the optimum conditions were as follows: calcination temperature of the catalyst 600 °C, n(lactic acid):n(n-butyl alcohol)=1.0:3.0, w(S2O82–/ZrO2-CeO2)=12.0%, reaction temperature 145 °C, and reaction time 2 h. The esterification efficiency of lactic acid was about 96.6%.