The gasification characteristics of five amino acids, i.e., glycine, alanine, valine, leucine, and proline, in supercritical water were compared. A tubular reactor was employed for the gasification reactions in the temperature range of 500 to 650 ℃ with a reaction pressure of 25 MPa and residence time of 86-119 s. The gasification characteristics of glycine, alanine, and leucine were determined to be similar, while the gasification rate of valine was much slower. The activation energies of valine and proline were lower than those of glycine, alanine, and leucine. These behaviors are attributed to the stability of the transition state for carboxyl radical production and secondary radical produced from valine.
Aqueous solutions (1.0-5.0 wt%) of glycine, which is a model compound of proteins, was gasified in supercritical water using a tubular reactor at temperature of 500-650 ℃ and pressure of 25 MPa for a residence time of 63-188 s. Activated carbon (0.5 wt%) was employed as a catalyst in order to improve gasification efficiency. The identification and quantification of gaseous products were conducted and the total organic carbon was measured for the liquid effluent. Based on the experimental results, the reaction rate parameters were determined for the carbon gasification efficiency of glycine in supercritical water, assuming a first-order reaction. The results showed that an elevated temperature would be required for achieving high carbon gasification efficiency. The activated carbon catalyst was found to be ineffective for glycine.
The gasification characteristics of aminobutyric acid and serine were determined under supercritical water conditions using a tubular flow reactor. A 1.0 wt% aqueous solution of these two amino acids was gasified at temperatures ranging from 400 to 650 and a pressure of 25 MPa with residence time of 86-222 s. The products were identified and quantified by gas chromatography, and the total organic carbon in the aqueous phase was also determined. The gasification characteristics were compared with those of glycine and alanine. The carbon gasification efficiency increased with higher reaction temperature. The gasification rate followed first order kinetics and was explained well by the Arrhenius equation. The gasification rate of aminobutyric acid was similar to that of glycine and alanine but the gasification rate of serine is faster. The oxygen in the hydroxyl group of serine is highly electronegative, so serine is more reactive than glycine and alanine.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.