Process feasibility experiments were carried out to form 1,3-propanediol precursor, acrolein, at 400 degrees C and 35 MPa using supercritical water with sulfuric acid and a large concentration of glycerol. In the experiments, optimization methods for reaction time and sulfuric acid concentration deduced from a reaction model were examined as functions of initial glycerol concentration. The optimum reaction time at which the yield peaked was inversely proportional to the initial glycerol concentration. Optimum sulfuric acid concentration was estimated by maintaining a constant ratio of the squared proton concentration to the initial glycerol concentration when the acid concentration was optimized at a certain initial glycerol concentration. A yield larger than 70% was obtained at 15 wt% of the initial glycerol concentration by using the conditions predicted by the optimization methods.