We present a direct and highly efficient approach for synthesizing glycerol carbonate, via the catalytic oxidative carbonylation of glycerol, using PdCl2(phen) (phen = 1,10-phenanthroline) as catalyst with the aid of RI. The palladium catalyst loading as low as 0.25 mol% is sufficient for high conversion (92%) and selectivity (99%) at the reaction condition: 2.0 MPa CO, 1.0 MPa O-2, 140 degrees C, 2h. The turnover frequency (TOF) reaches 184 h(-1). Furthermore, using crude glycerol, we achieved 85% conversion of glycerol. We discuss in detail a plausible mechanism based on PdI2(phen) as an intermediate. We propose that there is synergistic effect of l- and 1,10-phenanthroline on the performance of the Pd complex catalyst. Based on the cyclic voltammograms, the reduction of PdI2(phen) occurred at a more positive potential than that of PdCl2(phen). This may explain why the catalytic activity of PdI2(phen) was more effective than that of PdCl2(phen). (C) 2010 Elsevier B.V. All rights reserved.