Supercritical water gasification of fructose as a model compound for waste fruits and vegetables

• Fructose was gasified in supercritical water as a model compound for waste fruits.
• Impact of temperature, feed concentration, residence time and catalyst was studied.
• Maximum H2 yield was obtained with 4 wt% fructose in 60 s at 25 MPa and 700 °C.
• The selectivity for H2 from fructose was enhanced in the presence of 0.8 wt% KOH.
• KOH and NaOH relatively promoted water–gas shift reaction for higher H2 yields.

Generous amount of waste food as refused fruits and vegetables are obtained on a global scale that is usually disposed in landfill or oceans. The waste fruits are enriched with fructose, glucose and sucrose along with minor amounts of cellulose and hemicellulose that could potentially be converted to biofuels and biochemicals. With this objective, fructose was used as a model compound of waste fruits and vegetables for gasification in supercritical water using a continuous flow tubular reactor. Different parameters influencing supercritical water gasification were investigated in this study such as temperature (550–700 °C), residence time (30–75 s), feed concentration (4–10 wt%) and catalyst concentration (0.2–0.8 wt%) at a constant pressure of 25 MPa. Total gas yields, carbon gasification efficiency and hydrogen yields improved at an optimal temperature (700 °C), feed concentration (4 wt%) and residence time (60 s). Fructose gasification with 0.8 wt% KOH enhanced the selectivity for hydrogen (10.67 mol/mol) compared to those by 0.8 wt% NaOH (9.86 mol/mol) and non-catalytic gasification (3.37 mol/mol).

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