Gasification characteristics of histidine and 4-methylimidazole under supercritical water conditions

In this study, gasification characteristics of histidine and 4-methylimidazole were investigated for the first time. A tubular flow reactor was employed, and experiments were conducted in the temperature range of 500-650 A degrees C, at a fixed pressure of 25 MPa, with residence times of 86-119 s, and with 1.0 wt% aqueous solutions of histidine and 4-methylimidazole. The gaseous products were identified and quantified by gas chromatography (GC), and the aqueous phase was analyzed for total organic carbon (TOC). The gasification characteristics were compared with those of glycine and alanine, which represented the standard amino acid structure. The result showed that the carbon gasification efficiencies of both histidine and 4-methylimidazole increased with increasing reaction temperature. The gasification rate of 4-methylimidazole followed first-order kinetics and was explained well by the Arrhenius equation. The gasification rate for histidine could be predicted by the weighted summation of the adjusted gasification rates of glycine and 4-methylimidazole.