Hydrogen production from glycerol by supercritical water gasification in a continuous flow tubular reactor

In this work, glycerol was used for hydrogen production by supercritical water gasification. Experiments were conducted in a continuous flow tubular reactor at 445∼600 °C, 25 MPa, with a short residence time of 3.9∼9.0 s. The effects of reaction temperature, residence time, glycerol concentration and alkali catalysts on gasification were systematically studied. The results showed that the gasification efficiency increased sharply with increasing temperature above 487 °C. A short residence time of 7.0 s was enough for 10 wt% glycerol gasification at 567 °C. With the increase of glycerol concentration from 10 to 50 wt%, the gasification efficiency decreased from 88% to 71% at 567 °C. The alkali catalysts greatly enhanced water-gas shift reaction and the hydrogen yield in relation to catalysts was in the following order: NaOH > Na₂CO₃>KOH > K₂CO₃. The hydrogen yield of 4.93 mol/mol was achieved at 526 °C with 0.1 wt% NaOH. No char or tar was observed in all experiments. The apparent activation energy and apparent pre-exponential factor for glycerol carbon gasification were obtained by assuming pseudo first-order kinetics.