Cycloaddition of CO2 to Epoxides Catalyzed by Polyaniline Salts

• Published in: Chemistry : a European journal Vol. 13; no. 24; pp. 6992 - 6997
• Main Authors: He, Jinling, Wu, Tianbin, Zhang, Zhaofu, Ding, Kunlun, Han, Buxing, Xie, Ye, Jiang, Tao, Liu, Zhimin
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01-01-2007; WILEY‐VCH Verlag
• Subjects: carbon dioxide; cycloaddition reaction; epoxides; heterogeneous catalysis; polymers
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.200700210

The catalytic activity of polyaniline‐HX (X=I, Br, Cl) (PANI‐HI, PANI‐HBr, PANI‐HCl) for the cycloaddition of CO2 to propylene oxide (PO) to produce propylene carbonate (PC) was studied for the first time. It was shown that all the PANI salts were active for the reaction, and PANI‐HI was most active and selective. On the basis of the preliminary results, the effect of the reaction conditions on the cycloadditions of CO2 to propylene oxide and epichlorohydrin was further investigated by using PANI‐HI as the catalyst. The results indicated that the optimized temperature was around 115 °C. The maxima occurred in yield versus pressure curves at about 5 MPa for both substrates. Complete conversion was achieved in 3 h for epichlorohydrin and 6 h for propylene oxide at 115 °C and 5 MPa. With propylene oxide as the substrate, the reusability of PANI‐HI was evaluated and no loss of catalytic activity was detectable after the catalyst had been reused five times. The catalyst was characterized by thermogravimetric analysis (TGA) and scanning electron microscopy (SEM), which provided further evidence for the high stability of the catalyst. We believe that the catalyst has great potential for industrial applications because it has some unusual advantages, such as its easy preparation, high activity, selectivity, stability, low cost, and simple separation from products.
Keeping up with catalysis! Polyaniline‐HI is a very active, stable, selective, and inexpensive heterogeneous catalyst for the cycloaddition of CO2 to epoxides (see scheme).