Modified Zinc Oxide for the Direct Synthesis of Propylene Carbonate from Propylene Glycol and Carbon dioxide
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Modified Zinc Oxide for the Direct Synthesis of Propylene Carbonate from Propylene Glycol and Carbon dioxide Shiyong Huang Æ Shuigang Liu Æ Junping Li Æ Ning Zhao Æ Wei Wei Æ Yuhan Sun
Received: 20 March 2007 / Accepted: 2 July 2007 / Published online: 28 July 2007 Ó Springer Science+Business Media, LLC 2007
Abstract A series of modified zinc oxide catalysts were prepared and their catalytic activities were evaluated by the direct synthesis of propylene carbonate from propylene glycol and carbon dioxide in the presence of acetonitrile, which acted as not only the solvent but also the dehydrating reagent in the reaction. The reusability test indicated that the modified catalysts had the high stability. Ammonium carbonate was added into the reaction to significantly elevate the selectivity of propylene carbonate. Keywords Propylene carbonate Modified zinc oxide Propylene glycol Carbon dioxide
1 Introduction Recently, the development of an environmentally friendly industrial process utilizing carbon dioxide has drawn much interest, and it has been well recognized that the utilization of carbon dioxide as a carbon resource is important [1, 2]. One of the most promising methodologies in this area is the synthesis of five-membered cyclic carbonates from carbon dioxide and cyclic oxide [3–6], which are commercially important compounds and are used as electrolytes in lith-
ium batteries, as aprotic polar solvents, and as intermediates for producing polycarbonate and fine chemicals [7–9]. Moreover, a possible utilization of cyclic carbonates, such as propylene carbonate (PC) and ethylene carbonate (EC), is the transesterification with methanol to form dimethyl carbonate (DMC) and the corresponding glycol. It is well known that the transesterification of PC with methanol to form DMC is widely used in industrial synthetic process [10–14]. However, propylene glycol (PG) as by-product is always inevitable to be produced in the transesterification process (See Eq. (1)). The alcoholysis of urea with PG to synthesize PC is an available approach for making use of PG [15, 16]. However, it is a more perfect route to directly synthesize PC from CO2 and PG (See Eq. (2)). In this way, not only can be PG recycled but also CO2 can be utilized effectively. As a result, DMC is synthesized from methanol and CO2 by using PC as a recyclable intermediate according to Eqs. (1) and (2). H3C HC
H3C
O C
2CH3OH + H2C
O C
O H3C
O
O
O +
OH
OH
CH
CH2
(1)
CH3
H3C
S. Huang (&) S. Liu J. Li N. Zhao W. Wei Y. Sun State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences, Taiyuan 030001, P.R. China e-mail: [email protected] S. Huang S. Liu Graduate School of the Chinese Academy of Sciences, Beijing 100039, P.R. China
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CO2 + CH3
OH
OH
CH
CH2
HC
O
H2C
O
C
O + H2O
(2)
Recently, CeO2–ZrO2, Bu2SnO and Bu2Sn(OMe)2 have been developed to synthesize PC from PG and CO2 [17–19] . However, PC yield was very low, which was only about 2%. This was attributed to the thermodynam
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