Enhanced methane yield from supercritical water gasification of pentadecanoic acid

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.