Co-gasification of catechol and starch in supercritical water for hydrogen production

Hydrogen production from waste feedstocks using supercritical water gasification (SCWG) is a promising approach towards cleaner fuel production and a solution for hard to treat wastes. In this study, the catalytic co-gasification of starch and catechol as models of carbohydrates and phenol compounds was investigated in a batch reactor at 28 MPa, 400–500 °C, from 10 to 30 min. The effects of reaction conditions, and the addition of calcium oxide (CaO) as a carbon dioxide (CO2) sorbent and TiO2 as catalyst on the gas yields and product distribution were investigated. Employing TiO2 as a catalyst alone had no significant effect on the H2 yield but when combined with CaO increased the hydrogen yield by 35% and promoted higher total organic carbon (TOC) reduction efficiencies. The process liquid effluent was characterized using GC–MS, with the results showing that the major non-polar components were phenol, substituted phenols, and cresols. An overall reaction scheme is provided.

► The combination of CaO and TiO2 had a remarkable effect on gaseous product yields. ► The presence of CaO as CO2 sequester facilitated the observed increase the H2 yield. ► The impact of reaction time was insignificant compared to temperature effect. ► The catalytic activity of TiO2 was inhibited by formation of cyclo-compounds. ► We postulated starch and catechol co-gasification technique reaction scheme in supercritical water.