Highly efficient and recyclable catalysts SnCl 2 – x H 3 PW 12 O 40 /AC with Brønsted and Lewis acid sites for terephthalic acid esterification

Abstract

The esterification of terephthalic acid with monohydric alcohol is an important reaction that has been widely applied in plasticizer industry. However, high pressure, harmful solvent or prolonging the reaction time are always needed to achieve high conversion of terephthalic acid, which increase the production cost. In this work, a series of SnCl2–xH3PW12O40/AC (x = 10, 15, 20, and 30 wt%) catalysts containing both Brønsted and Lewis acidic sites were prepared and used for preparation of terephthalates without any solvent under atmospheric pressure. Compared with the other works in previous reports, the catalysts in this study demonstrated that the high catalytic activity and strong stability in the process of esterification, which could be attributed to the high total surface acidity and the unique Keggin structure of catalysts, respectively. Among them, the catalyst SnCl2-15H3PW12O40/AC possesses the highest acid content and exhibits a high conversion of terephthalic acid (99% in 2.5–3 h). The remarkable activity and stability of the catalyst SnCl2–15H3PW12O40/AC hold a great potential application in plasticizer industry.