Biohydrogen Production by Catalytic Supercritical Water Gasification: A Comparative Study

Abstract

In this article, supercritical water gasification of biocrude at different conditions was performed and compared to each other. Three scenarios were considered while treating biocrude originating from cattle manure (CM) and corn husk (CH), namely, uncatalyzed feedstock, catalyzed with 10% Ni–0.08% Ru/Al ₂O ₃ and finally catalyzed with 10% Ni–0.08% Ru/Al ₂O ₃–ZrO ₂. It was found that 10% Ni–0.08% Ru/Al ₂O ₃–ZrO ₂ has performed significantly better than the other two scenarios over the 5 hour run time with a 193 and 187% higher hydrogen yield compared to the uncatalyzed and 10% Ni–0.08% Ru/Al ₂O ₃ catalyzed scenarios, respectively. Compared to CM gasification in the presence of a 10% Ni–0.08% Ru/Al ₂O ₃–ZrO ₂ catalyst, the catalyst got deactivated because of the high phenol and furan content in the corn husk biocrude, therefore hydrogen yield performance fell significantly. It was observed that the carbon gasification efficiency of the biocrude was independent of temperature. In terms of carbon conversion, the equilibrium conditions for the biocrude considered were attained at lower temperature. A mechanistic model based on the Eley–Rideal method was devised and tested against the obtained data. The dissociation of adsorbed oxygenated hydrocarbon is found to be the rate-determining step with an average absolute deviation of 3.55%.