Hydrogen Production from Supercritical Water Gasification of Model Compounds of Crude Glycerol from Biodiesel Industries

Abstract

Biodiesel production through transesterification results in a large quantity of crude glycerol as a byproduct, the utilization of which is technically and economically challenging. Because of the ability to efficiently process wet feedstocks, supercritical water gasification (SCWG) is utilized in this study to convert crude glycerol into hydrogen-rich syngas. A significant challenge addressed through this study is the decomposition routes of different heterogeneous components of crude glycerol during SCWG. Pure glycerol, methanol and oleic acid were investigated for SCWG as the model compounds of crude glycerol. SCWG of model compounds at temperature, pressure, feedstock concentration and reaction time of 500 °C, 23–25 MPa, 10 wt% and 1 h, respectively, revealed methanol to exhibit the highest H2 yield of 7.7 mmol/g, followed by pure glycerol (4.4 mmol/g) and oleic acid (1.1 mmol/g). The effects of feedstock concentration from 30 wt% to 10 wt% increased H2 yield from all model compounds. Response surface methodology (RSM) was used to develop a response curve to visualize the interactive behavior and develop model equations for the prediction of H2-rich gas yields as a function of the composition of model compounds in the crude glycerol mixture. Predictive models showed a good agreement with experimental results, demonstrating high accuracy and robustness of the model. These findings demonstrated a strong potential of crude glycerol for SCWG to generate H2-rich syngas.