Catalytic gasification of anthracene in supercritical water with Ni/TiO2 catalyst: Products distribution and kinetics

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Supercritical water gasification (SCWG) is a clean and efficient utilization way of coal to produce hydrogen-rich gas. As the consumption of PAHs is the rate-determining step to the rapid gasification of coal in SCW, anthracene was used as the simplest model of PAHs to investigate the ring-opening and gasification mechanism of PAH compounds in supercritical water (SCW). The SCWG experiments of 7.5 wt% anthracene were carried out in SCW under various temperatures (400–550 °C) and residence times (5–30 min). Ni/TiO2 catalysts were added to achieve the fast and complete gasification of anthracene, and a carbon gasification efficiency of 95.73% was achieved at 500 °C, which was 100 times higher than 0.95% of the non-catalytic condition. A kinetic model including a detailed reaction pathway for anthracene was successfully proposed to reveal the catalytic mechanism of anthracene gasification in SCW. The results indicated that the addition of Ni/TiO2 effectively reduced the activation energy of anthracene hydrogenation to generate CH4, and this reaction was most critical for the generation of CH4. This work guided the determination of key parameters for industrial-scale reactors to achieve an optimal design, providing a promising method for in-situ elimination of char during SCWG of coal.