reference to the examples and comparative examples the reaction results were obtained by gas chromatography analysis using n pentadecane as an internal standard capillary column bpx 5 available from sge co ltd 50 u00b0 c u2192 300 u00b0 c 3 01 g 32 mmol of phenol 25 54 mg 12 u03bcmol pd of 5 palladium carbon available from n e chemcat co ltd 2 68 mg 12 u03bcmol of lead ii oxide 2 99 mg 12 u03bcmol of cobalt ii acetate tetrahydrate and 77 3 mg 0 24 mmol of tetrabutylammonium bromide were charged in a 40 ml hastelloy autoclave after the air in the system was replaced by carbon monoxide 60 atm of carbon monoxide and 30 atm of dry air were introduced into the autoclave followed by stirring at 100 u00b0 c for 3 hours by induction stirring after reaction the liquid phase was quantitatively analyzed by gas chromatography as a result diphenyl carbonate was obtained with a yield of 5 64 0 90 mmol based on phenol bromophenols were not observed the same reaction as that in example 1 was carried out except that cobalt ii acetate tetrahydrate was not used as a result diphenyl carbonate was obtained with a yield of 8 38 1 33 mmol based on phenol bromophenols o and p bromophenols were observed but m bromophenol was not observed and the same applies hereinafter were produced as by products in an amount of 54 0 0 127 mmol based on the tetrabutylammonium bromide used the same reaction as that in example 1 was effected except that 2 55 mg 1 2 u03bcmol of 5 palladium carbon was used 37 0 mg 0 24 mmol of tetramethylammonium bromide was used in place of.