368 JOURNAL OF COSMETIC SCIENCE highest acid conversion for the esterification reaction system. The boiling temperatures of the reactants and the product (benzyl acetate) were taken into consideration when mak- ing the selection. In order to investigate the effect of temperature on the esterification reaction of AA with BA catalyzed by [EMIM] [HSO 4 ], experiments were performed for 8 h with AA:BA:[EMIM] [HSO 4 ] molar ratio of 1:1:0.75 at 90–100°C and 110°C. The results were shown in Figure 3. It has been determined that 110°C is the reaction tem- perature at which the conversion of acid close to 90% is achieved. The effect of AA to BA molar ratio on the esterification reaction was investigated exper- imentally. Similar to previous studies in the literature, AA:BA molar ratio of 1, 1.5, 2 was selected. The experiments at 4, 6, and, 8 h in which [EMIM] [HSO 4 ] mole ratio was 0.75 were carried out at 110°C. The results were given in Figure 4. It was seen that as the number of acid increases, the conversion in the reaction decreases. It shows that when the 0 20 40 60 80 100 0 1 2 3 4 5 6 7 8 Reaction time (h) Figure 2. Effect of time on the conversion of acid (%) using [EMIM] [HSO 4 ] as catalyst. (AA: BA: [EMIM] [HSO 4 ] molar ratio 1:1:0.5, T=110°C) 0 10 20 30 40 50 60 70 80 90 100 90 100 110 Temperature (°C) Figure 3. Effect of temperature on the conversion of acetic acid (AA) (%) using [EMIM] [HSO 4 ] as catalyst. (Reaction conditions: AA: BA: [EMIM] [HSO 4 ] molar ratio 1:1:0.75, t = 8 h) Conversion of acid (% ) Conversion of acid (%)

369 SYNTHESIS OF BENZYL ACETATE initial acid concentration is excess in the reaction medium, the reversible esterification reaction is more effective in the reverse direction. Therefore, the conversion is low due to a large amount of product formed. Conventional acidic catalysts used in esterification reactions cause corrosion of process equipment and pose a threat to environment. Experiments were carried out to get an idea about the amount of ILs used as catalysts to eliminate these disadvantages. In this study in which high conversion was aimed using an optimum catalyst, the relationship between the change of IL amount and conversion AA:BA:[EMIM] [HSO 4 ] molar ratio was investigated by experiments between 1:1:0.15 and 1:1:0.75. Figure 5 showed that AA conversion increases with an increasing amount of IL in the reaction. For this reason, in optimization experiments, IL molar ratios were studied as 0.25, 0.50, and 0.75. 4 6 8 0 20 40 60 80 100 1 1.5 2 AA : BA molar ratio Figure 4. Effect of acid/alcohol molar ratio on the conversion of acid (%) using [EMIM] [HSO 4 ] as catalyst at T = 110°C. 0 10 20 30 40 50 60 70 80 90 100 0.00 0.15 0.25 0.50 0.75 IL molar ratio Figure 5. Effect of amount of catalyst on the conversion of acid (%) using [EMIM] [HSO 4 ] as catalyst. (Reaction Conditions: AA:BA = 1:1 T = 110°C, t = 6 h) Conversion of acid (%) Conversion of acid (% )