Synthesis of Propylene Carbonate from Carbon Dioxide and Propylene Oxide Using Zn- Mg- Al Composite Oxide as High-effici
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Synthesis of Propylene Carbonate from Carbon Dioxide and Propylene Oxide Using Zn-Mg-Al Composite Oxide as High-efficiency Catalyst Wei-Li Dai • Shuang-Feng Yin • Rui Guo • Sheng-Lian Luo • Xin Du • Chak-Tong Au
Received: 17 September 2009 / Accepted: 14 October 2009 / Published online: 30 October 2009 Ó Springer Science+Business Media, LLC 2009
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 B H0 \ 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. Keywords Zn-Mg-Al-O composite oxide Propylene carbonate Propylene oxide Carbon dioxide Heterogeneous catalysis
W.-L. Dai S.-F. Yin (&) R. Guo S.-L. Luo X. Du C.-T. Au (&) College of Chemistry and Chemical Engineering, Hunan University, 410082 Changsha, Hunan, China e-mail: [email protected] C.-T. Au e-mail: [email protected] W.-L. Dai C.-T. Au Department of Chemistry, Hong Kong Baptist University, Kowloon Tong, Hong Kong, China
1 Introduction Although being a major greenhouse gas, CO2 is an attractive C1 building block. The compound is abundant, inexpensive, nontoxic, nonflammable and highly functional [1–3]. In view of the concepts of ‘‘sustainable society’’, ‘‘atomic economy’’ and ‘‘green chemistry’’, the transformation of CO2 to valuable chemicals has been investigated in recent years. The synthesis of cyclic carbonate through cycloaddition of CO2 to epoxide is one of the few catalytic processes that have been commercialized (Scheme 1). Cyclic carbonates, e.g. ethylene carbonate and propylene carbonate (PC) are important compounds that can be used as polar solvents, as electrolytic elements of lithium secondary batteries, as precursors for synthesis of polycarbonates and polyurethanes, and as raw materials in a wide range of chemical reactions [1–3]. In the past decades, numerous catalysts have been studied for the cycloaddition reaction [1–30], e.g., metallic complexes [4–7], phosphines [8, 9], organic bases [10–12], ionic liquids [13–16], metal oxides [17–19], modified molecular sieves [20–24] and smectite [25], and supported catalysts [26–30], etc. However, most of the high-efficiency ones are homogeneous catalysts, and the disadvantages are the high cost for catalysts fabrication (e.g., metallic complexes) and pr
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