, Volume 136, Issue 1-2, pp 35-44
Date: 30 Oct 2009

Synthesis of Propylene Carbonate from Carbon Dioxide and Propylene Oxide Using Zn-Mg-Al Composite Oxide as High-efficiency Catalyst

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Abstract

A series of Zn-Al composite oxides that were modified with alkaline earth metals, Zn-M-Al-O (M = Mg, Ca, Sr, and Ba) were fabricated via calcination of the corresponding hydrotalcite precursors, and evaluated as catalysts for the synthesis of propylene carbonate (PC) from CO2 and propylene oxide. Among the Zn-M-Al-O catalysts, Zn-Mg-Al-O (Zn/Mg = 4.0, pH = 10, without hydrothermal treatment) is the best in performance, showing PC selectivity of 99.2% and yield of 88.8% (140 °C, 12 h). Furthermore, the Zn-Mg-Al-O catalyst can be readily reused and recycled without any loss of activity in a test of five cycles. Through detailed studies of the basic nature of the Zn-M-Al-O catalysts, it was found that a moderate basicity (6.1 ≤ H 0 < 8.9) is beneficial to the cycloaddition reaction. The NH3- and CO2-TPD results also indicate that the Zn-Mg-Al-O catalyst has acid–base bifunctional properties, and a reaction mechanism is proposed.

Graphic Abstract

Zn-Mg-Al composite oxides were prepared via calcination of the corresponding hydrotalcite precursors, and used as catalysts for the synthesis of propylene carbonate from CO2 and propylene oxide. We achieved high catalytic efficiency under mild conditions, easy separation of catalyst from the product, and good recyclability of the catalyst. A plausible reaction mechanism has been proposed for the catalytic action.