Effects of Lewis acid on catalyzing gasification of sewage sludge and model compounds in supercritical water

• Published in: International journal of hydrogen energy 2021-02, Vol.46 (13), p.9008-9018
• Main Authors: Gong, Miao, Li, Zhen, Wang, Mengqi, Feng, Aixin, Wang, Linlu, Yuan, Shoujun
• Format: Article
• Language: English
• Subjects: Dewatered sewage sludge; Hydrogen; Lewis acid catalyst; Supercritical water gasification
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2020.12.207

In this work, we investigated how different types and concentrations of Lewis acids effect gas yield and composition from supercritical water gasification (SCWG) of dewatered sewage sludge (DSS). Furthermore, the catalytic mechanism was investigated using AlCl3 as a representative Lewis acid catalyst. Results showed that non-catalytic gasification of DSS produced a hydrogen yield of 0.13 mol/kg organic matter (OM) and total gas yield of 4.82 mol/kg OM; while the addition of 10 wt% Lewis acid resulted in a significantly improved H2 and total gas yield of 0.77–7.76 mol/kg OM and 7.57–22.88 mol/kg OM, respectively. In addition, the Lewis acids tested herein depicted the following activity trend: AlCl3＞FeCl3＞NiCl2＞ZnCl2. The required temperature for generating hydrogen from SCWG of DSS was greatly reduced when AlCl3 was present during the heating process. Furthermore, AlCl3 significantly increased the hydrogen yield from SCWG of the model compounds. Finally, AlCl3 catalyzed SCWG of guaiacol and glycerol showed the best hydrogen selectivity. •Effects of different Lewis acid on gas yield and composition were studied.•The hydrogen production increased by 60 times after adding 10 wt% AlCl3.•AlCl3 can promote C–C bond breakage and gasification of small molecular organics.•AlCl3 greatly enhanced the H2 selectivity of SCWG of guaiacol and glycerol.•AlCl3 makes the damage and porous morphology of solid surface more evident.