Noncatalytic Gasification of Lignin in Supercritical Water Using a Batch Reactor for Hydrogen Production: An Experimental and Modeling Study

In this work, Central Composite Design (CCD) methodology was first introduced to noncatalytic SCWG of lignin for experimental design, model building, and data analysis. Noncatalytic SCWG of lignin was performed in a batch reactor with the specific focus on hydrogen yield optimization. By both experimental and statistical modeling, the main effects as well as interaction effects of three parameters including temperature, pressure, and water to biomass ratio were investigated in a wide range of 399-651 degrees C, 2329 MPa, 3-8, respectively. As the result, up to 651 degrees C higher temperature is desirable for hydrogen production; however, change of pressure from 23-29 MPa did not show significant effect on hydrogen yield. Strong interaction between temperature and water to biomass ratio was observed at temperatures higher than 525 degrees C, and a dramatic decrease in hydrogen yield with increase in water to biomass ratio was observed at 600 degrees C. According to the model, the maximum hydrogen yield can reach 1.60 mmol/g biomass when the reaction conditions are temperature = 651 degrees C, pressure = 25 MPa, and water to biomass ratio = 3.9.