Decomposition of formic acid in supercritical water

 The decomposition of formic acid (0.05mol/L~0.70mol/L) in supercritical water was investigated under 550℃~650℃, 24MPa~30MPa, and a residence time of 16s~46s. The results showed that the gaseous products from the decomposition are mainly H₂, CO₂ and CO; the yields of H₂ and CO₂ are much higher than that of other products. High temperature is in favor of H₂ production, while the pressure exhibits less effect on formic acid decomposition at high temperature (> 600℃). With the increase of the residence time from 16s to 20s, the molar fraction H₂ in the gaseous products is increased steadily, along with the rapid increase of carbon gasification efficiency. The reaction routes are dependent largely upon the feedstock concentration. With a low concentration of formic acid in the feed (＜ 0.1mol/L), the decomposition includes decarboxylation and dehydration routes; the former is the dominant pathway. Higher formic acid concentration may bring on many sidereactions. Alkaline additives are harmful for the hydrogen production from formic acid decomposition.