Catalytic supercritical gasification of biocrude from hydrothermal liquefaction of cattle manure

Abstract

In this article, we performed catalytic supercritical water gasification (SCWG) of biomass to enhance hydrogen production. First we used glucose as a model compound to screen the best catalyst and then we used this catalyst to gasify biocrude from hydrothermal liquefaction of cattle manure. We introduced a novel dual metal (Ni, Ru)—dual support (Al2O3, ZrO2) catalyst for the first time in SCWG in order to improve the H2 yield. A continuous flow tubular reactor was employed to perform the experiments. Novel 10%Ni-0.08%Ru/Al2O3-ZrO2 catalyst showed the highest H2 yield (1.34mol/mol of C for glucose and 1.01mol/mol of C for biocrude) and highest carbon gasiifcation efficiency (88% for glucose and 92% for biocrude). It was found that Ru promoted Ni and ZrO2 showed some catalytic activities towards hydrogen production. The pressure was 25MPa for all experiments. Stability test showed that 10%Ni-0.08%Ru/Al2O3-ZrO2 was highly stable for a 20h run. Among the parameters studied, higher temperature favored H2 yield, whereas higher concentration led to lower H2 yield. We found that carbon gasification efficiency of cattle manure biocrude was independent of variation in temperature and concentration. Also the equilibrium condition was attained at lower temperature and concentration in terms of carbon conversion of the feed. An Eley–Rideal (ER) based mechanistic model was devised and tested against the obtained data. It was found the dissociation of adsorbed oxygenated hydrocarbon is the rate determining step with an average absolute deviation 6.65%.