Supercritical water gasification and subsequent steam reforming of the product gas under elevated temperature and pressure

A continuous process combining the supercritical water gasification (SCWG) of ethanol with the subsequent steam reforming (SR) of the product gas was investigated. An experimental study was conducted that involved the operating parameters in the SR reactor, the ethanol concentration, and a comparison of two commercial catalysts for SR. With ethanol as a biomass model compound, complete gasification in the SCWG reactor was achieved. Regarding the SR reactor, high pressures, i.e., 20–40 bar, required a temperature of 750 °C to achieve methane conversion higher than 90% at a constant gas hourly space velocity of 63500 h −1 . The increase in EtOH concentration significantly decreased the steam/carbon ratio of the SCWG product and increased the content of CH 4 , C 2+ hydrocarbons, and CO. This in turn resulted in a decrease in H 2 yield in the SR reactor from 98.6% to 58.3%, as the EtOH concentration increased from 5 wt% to 20 wt% at a temperature of 730 °C, pressure of 30 bar, and a space velocity of 47877 h −1 . Under atmospheric pressure, both catalysts showed similar CH₄ conversion. However, at higher pressures (30–40 bar), the catalyst with the higher Ni loading exhibited greater activity in SR. • EtOH supercritical water gasification (SCWG) followed by steam reforming (SR). • Carbon Gasification Efficiency (CGE) during ethanol SCWG ranged from 97% to 99.6%. • CH 4 conversion after SR > 90% at 750 °C, 20–40 bar, and 63500 h −1 space velocity. • Increasing EtOH (5–20 wt%) .→ H₂ yield from 98.6% to 58.3%. • At 30–40 bar during SR, the Ni catalyst with higher loading had higher activity.