Catalytic Gasification of Pinewood in Hydrothermal Conditions for Hydrogen Production

Lignocellulosic biomasses are gaining attention for biofuel production to supplement the increasing energy demands. This study is focused on identifying the candidacy of pinewood for hydrogen production through subcritical (300 degrees C), near-critical (370 degrees C) and supercritical (550 degrees C) water gasification. Pinewood was gasified to study the impacts of temperature (300-550 degrees C), feed concentration (20-30 wt%) and reaction time (20-60 min). The effects of metal catalysts (e.g., Ni/Al2O3, Ru/Al2O3, NaOH and KOH) were also examined to maximize hydrogen yields and carbon gasification efficiency. The individual gas yields, total gas yields and lower heating values were calculated for comparative evaluation between subcritical, near-critical and supercritical water gasification as well as between catalytic and non-catalytic gasification of pinewood. Supercritical water gasification at higher temperatures (550 degrees C), longer reaction time (60 min) and lower feed concentration (20 wt%) improved water-gas shift reaction resulting in high hydrogen yields. Greater yields of hydrogen (0.52 mmol/g) and total gases (6.4 mmol/g) with lower heating value of 423 kJ/Nm(3) was found with 20 wt% of pinewood at 550 degrees C and 60 min. Ni/Al2O3 at a concentration of 5 wt% showed highest yields for hydrogen (2.54 mmol/g) in the gas products when compared to other catalysts. The catalytic activity towards hydrogen production decreased as Ni/Al2O3 > KOH > Ru/Al2O3 > NaOH. The findings imply that pinewood is a promising feedstock for hydrogen production by supercritical water gasification.