Supercritical water conversion of glycerol : comparative parametric study between batch and continuous process

• Glycerol, a main by-product of the biodiesel production, has a high valorization potential. This paper proposes a comparison of hydrogen production from glycerol using batch (5 mL and 500 mL) and continuous (100 mL) processes. The influence of different operating parameters has been studied: temperature (450°C-600°C), pressure (20-28MPa), glycerol concentration (5-20wt%), catalyst concentration (K 2 CO 3 or NaOH, 0-5 wt%), reaction time (5-120 min, batch), residence time (12 min, continuous process), stirring rate (500-1500 rpm, batch of 500ml), and heating rate (50% and 100% of heating power). • Quantitative glycerol conversion has been observed: until 99% of TOC removal by SCWG. While the amount of solid formed is insignificant, the produced gas volume reached 43 L gas/L solution (5 wt% glycerol) with a molar composition up to 60% H 2 and 30% CO 2 (atmospheric pressure). Various proportions of CH 4 , C 2 H 6 and C 2 H 4 have been observed. Catalyst contribution to the gasification yield of glycerol is relevant. • SCW conversion of glycerol, quantitative by-product in biodiesel industry, into hydrogen is a sustainable process. The yield obtained in the continuous laboratory reactor (3 mol H 2 /L of reactor/h) under homogeneous catalysis (K salts, low concentrations) recommends the process for further research and pilot development