Synthesis of Polyionic Liquid by Phenolic Condensation and Its Application in Esterification

A novel polyionic liquid for esterification was synthesized by phenolic condensation. Different characterization techniques were applied, and the result showed that the catalyst had high acidity amount (4.5 mmol/g) and good thermal stability. The decomposition temperature of the polyionic liquid catalyst (PIL-S) was 240 °C, which was fitted to the product of ester. Owing to these good properties, the PIL-S exhibited excellent catalytic activity in esterification. The optimized condition was the 6 wt % catalyst amount, and the ratio of acetic acid to n-butanol was 0.8:1 at 95 °C for 3 h. In the optimized condition, the yield of ester was 97.1%. The PIL-S also has a good catalytic effect in other esterification systems. Compared with commercial resins (Amberlyst 15) and other catalysts, PIL-S showed better catalytic activity. After eight times use, the yield of ester did not decrease obviously (over 94%). The structure of PIL-S remained stable after eight times use.