Enhanced methane yield from supercritical water gasification of pentadecanoic acid

Abstract

The gasification of pentadecanoic acid without the catalyst was performed in supercritical water by using quartz reactors. It was investigated that effects of temperature from 400 to 500 °C, mass loading of 5–20 wt%, and reaction time of 30–75 min on the production of H2, CH4, CO, CO2 and C2H4 from supercritical water gasification. High CH4 yield of 6.50 mmol/g was obtained at 500 °C, 5 wt% pentadecanoic acid and 75 min without any catalyst. The results also showed that the yield of all gas species increased with temperature, and decreased with the rising mass loading; most gas yields increased with the reaction time, except the C2H4 yield got to a maximum at the reaction time of 45–60 min above 500 °C with the all mass loadings (5–20 wt%), and the CO2 yield almost remained constant above 500 °C with the all mass loadings (5–20 wt%) after 45 min reaction time. The sequence of the influence on gas yield was: temperature > reaction time > mass loading. The manipulation of reaction temperature and time offered us an efficient way to control the product selectivity, since the amounts of valuable gas components such as H2, CH4 and C2H4 were strongly attached to these two process variables.