超临界水中甲酸降解过程实验研究

在550℃~650℃,24 MPa~30 MPa,反应停留16 s~46 s的条件下,对初始浓度0.05 mol/L~0.70 mol/L的甲酸溶液在超临界水中的降解过程进行实验研究。结果表明,甲酸降解的气体产物为H2、CO2和CO,其中H2、CO2为主要产物。高温有利于甲酸降解和H2生成。温度较高(600℃)时,压力变化对甲酸降解无明显影响。在一定范围内延长反应时间可提高气体产物中H2的体积分数和碳气化率。甲酸初始浓度对甲酸降解机理有重要影响,浓度较低(0.1 mol/L)时,甲酸降解主要包含脱羧反应和脱羰反应两条反应路径,其中脱羧反应为主反应路径;浓度较高时则有许多副反应发生。碱性添加剂不利于甲酸降解生成H2。

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.