Preparation of SO_4~(2-)/TiO_2-M_xO_y solid superacid and its activity for esterification

SO_4~(2-)/TiO_2-MoO_3, SO_4~(2-)/TiO_2-Nd_2O_3 and SO_4~(2-)/TiO_2-Fe_2O_3 solid superacid was prepared and used as the catalyst for synthesis of isoamyl salicylate. The experimental results showed that SO_4~(2-)/TiO_2-Nd_2O_3 exhibited the highest catalytic activity. Structure of the catalyst was characterized by thermal analysis, IR, SEM and XRD. The results showed that the catalytic activity was dependent on quantity of SO_4~(2-) adsorbed, which caused changes in surface topography and phase of the catalyst and hence affected behaviors of the catalyst. Optimum condition for the esterification reaction was obtained as follows by linear regression orthogonal design: reaction for 1 h, catalyst dosage=14.5% of the mass of salicylic acid, n(isoamyl alcohol): n (salicylic acid)=0.56. Structure of the isoamyl salicylate synthesized was characterized.