Hydrothermal gasification performance of Enteromorpha intestinalis as an algal biomass for hydrogen-rich gas production using Ru promoted Fe–Ni/γ-Al2O3 nanocatalysts

Abstract

Supercritical water gasification (SCWG) of Enteromorpha intestinalis (E. intestinalis) as a major algal biomass of southern coast of Caspian Sea was investigated in a batch reactor with and without the catalyst, to determine its potential for hydrogen production. The highest hydrogen yield of 5.25 (mmol H2/g of E. intestinalis) was observed for the noncatalytic test in the temperature of 440°C, water loading of 6g, E. intestinalis loading of 0.06g and reaction time of 10min. All catalytic tests were performed in this condition in the presence of unpromoted and ruthenium promoted Ni–Fe/γ-Al2O3 nanocatalysts. Catalysts were prepared with 12wt.% of Ni and 6wt.% of Fe in the active phase and 0.5–2wt.% of Ru as a promoter via microemulsion technique. Nanocatalysts were characterized by ICP, BET, XRD, H2 chemisorption, and TEM techniques to recognize their physicochemical properties. According to catalyst characterizations, the promoted Ni–Fe/γ-Al2O3 with 2wt.% Ru with higher dispersion and smaller size of nickel on γ-Al2O3, showed the best performance during SCWG of E. intestinalis. The maximum H2 yield of 12.28 (mmol H2/g of E. intestinalis) and hydrogen selectivity of 0.74, were obtained by using this optimized catalyst.