Test data for the catalytic oxidation of ethylene glycol (EG) into glyoxal obtained with a laboratory continuous flow tubular reactor are reported. A ferric molybdate catalyst modified with triammonium phosphate was used. Reaction parameters (temperature. contact time) affect the product distribution. The yield of glyoxal for the Fe-Mo-P catalyst was 43.3% at 88.9% conversion, whereas the corresponding values for the Fe-Mo (unmodified catalyst) were 20.5 and 97.2%. The addition of phosphorus formed a new Fe2MoP12 phase which restrains the reaction pathway towards carbon oxides.