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Issue 6, 2013
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Highly efficient synthesis of cyclic ureas from CO2 and diamines by a pure CeO2 catalyst using a 2-propanol solvent

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Abstract

Pure cerium oxide (CeO2) acts as an effective and reusable heterogeneous catalyst for direct synthesis of cyclic ureas from CO2 and diamines even at a low CO2 pressure of 0.3 MPa. 2-Propanol is the most preferable solvent to provide good selectivity. The system composed of a CeO2 catalyst and a 2-propanol solvent is applied to various diamines to provide the corresponding cyclic ureas in high yields (78–98%), including six-membered-ring ureas that are difficult to be synthesized from CO2. Based on the kinetic studies on the effect of CO2 pressure and amine concentration and FTIR studies on adsorption of ethylenediamine and CO2 onto CeO2, the following mechanism for the synthesis of cyclic urea is proposed: (1) formation of carbamic acid and carbamate species on CeO2, (2) decomposition of carbamic acid to a free amino group and CO2, (3) nucleophilic attack of the amino group on the carbamate on CeO2 to produce the cyclic urea and (4) desorption of the product and regeneration of CeO2.

Graphical abstract: Highly efficient synthesis of cyclic ureas from CO2 and diamines by a pure CeO2 catalyst using a 2-propanol solvent

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Publication details

The article was received on 15 Mar 2013, accepted on 11 Apr 2013 and first published on 07 May 2013


Article type: Paper
DOI: 10.1039/C3GC40495A
Citation: Green Chem., 2013,15, 1567-1577
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    Highly efficient synthesis of cyclic ureas from CO2 and diamines by a pure CeO2 catalyst using a 2-propanol solvent

    M. Tamura, K. Noro, M. Honda, Y. Nakagawa and K. Tomishige, Green Chem., 2013, 15, 1567
    DOI: 10.1039/C3GC40495A

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