Effect of Activated Carbon Catalytic on Supercritical Water Gasification of Glycine as a Model Compound of Protein

Abstract

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.

Gasification Characteristics of Aminobutyric Acid and Serine as Model Compounds of Proteins under Supercritical Water Conditions

“…Valine had the lowest gasification rate; possibly due to the formation of secondary radicals, which are relatively stable and can combine to form bulky molecules 39) . Gasification of glycine and alanine was found to follow first order reaction kinetics over this range of reaction temperatures 37), 38) , so we assumed that the gasification reaction rate of aminobutyric acid and serine are also first-order with respect to the amount of carbon feedstock. The pre-exponential factors and activation energies of the employed amino acids were determined by fitting to the experimental data of carbon gasification efficiency.…”

Gasification Characteristics of Amino Acids in Supercritical Water

“…We have already determined that the gasification rates of glycine 75) and alanine 76) , as model protein compounds in supercritical water, are practically the same. If other amino acids also undergo gasification at the same rate, we will be able to safely apply this gasification rate to other amino acids and likely proteins as well.…”

Gasification Characteristics of Alanine in Supercritical Water

“…As is characteristic for supercritical water gasification, the efficiency increases significantly with increasing temperature, as was observed for glucose by Xu et al 7),15) . Figure 4 also shows the carbon gasification efficiency of 1.0 wt% glycine 38) . Glycine gasification was conducted four times, and alanine gasification was conducted three times to obtain sufficient reproducibility.…”

“…To determine the gasification characteristics, the effect of tarry material production should be omitted. It is not possible to completely get rid of it, but judging from the effect of residence time, 1.0 wt% was found to be sufficiently dilute so that the gasification characteristics is expressed as a first order reaction with a small error 38) . For the case of alanine, the effect of tarry material production is negligible, and we can safely assume first order kinetics.…”

“…compound, in supercritical water 38) , the determination of gasification of other amino acids and comparison of t h e i r g a s i fi c a t i o n r a t e s s h o u l d b e i n t e r e s t i n g . Especially if we can compare two similar compounds that differ by only one functional group, it might give some insight into the effect of the functional group on decomposition rate in supercritical water.…”