occasionally liquid and vent gas samples for gc analysis were taken at the times shown in table 2 after 30 hrs the reaction was terminated the results from the liquid samples taken from the reactor during reaction of example 1 are given in table 1 the dff yield increased with time to a maximum yield of 51 and then decreases thereafter the mini reactor data is summarized in table 3 the rate of reaction as given by the rate of disappearance of huy was dependent upon the concentration of the catalyst see especially examples 3 4 the maximum yields and chemical species selectivities were also dependent on the concentration of the catalyst see examples 1 3 6 the dependence of the selectivity on the concentration of catalyst is given in detail for examples 3 4 and 6 in table 2 the formation of carbon dioxide and carbon monoxide are undesirable because they are caused by the decomposition of hmf and its products as well as from the solvent acetic acid as can be seen in table 2 increasing the catalyst concentration greatly decreases the formation of these carbon oxides example 4 combines the best yield shortest reaction time and one of the lowest rates of carbon oxide formation 2 5 diformylfuran was isolated from the reaction mass as follows the liquid from the reaction mixture was allowed to evaporate the residue after evaporation of the reaction mixture was a sublimed under vacuum followed by recrystallization of the sublimate from toluene or cyclohexane or b mixed with silica gel and extracted with hexanes or cyclohexane in a soxhlet extractor.