Gasification of two and three-components mixture in supercritical water: Influence of NaOH and initial reactants of acetic acid and phenol

Acetic acid (HAc) and phenol are the most common and refractory compounds during supercritical water gasification (SCWG) of organic waste water for hydrogen production. Here we report SCWG of HAc and the two and three-components mixture containing HAc and phenol with and without sodium hydroxide catalyst, which was conducted in a tubular flow reactor. Sodium hydroxide had a catalytic effect on the steam reforming reaction of methane during SCWG of HAc. For SCWG of HAc (0.5wt%) and phenol (1.0wt%) mixture, yield of hydrogen and carbon dioxide reached a maximum at 0.2wt% of sodium hydroxide. The hydrogenation of phenol to form benzene and further to cyclohexane can be reinforced by the acceleration of NaOH on hydrogen production. The amount of undesired long-chain alkyl esters were also found in the liquid products. Large amount of sodium acetate and sodium phenolate formed at high NaOH concentrations, which can lead to lower reaction efficiency and more serious deposition and coking problem. For SCWG of the three-components (methanol, HAc and phenol) mixture, TOC (Total Organic Carbon) removal efficiency, H and C gasification efficiency can be strongly retarded by both HAc and phenol. Decarboxylation of HAc leaded to relatively higher C gasification efficiency. Besides, their empirical quadric polynomial regression models were provided via response surface method.

► Supercritical water gasification of acetic acid with NaOH catalyst.
► Influence of NaOH on co-gasification process of acetic acid and phenol mixture.
► Study of interaction effect and co-gasification characteristics of three-components mixture by response surface method.