Production of hydrogen-rich syngas by steam reforming from toluene over βNiFe/CaO-δZSM-5 catalysts

Toluene reforming for hydrogen production can convert toluene in waste gas into clean energy. A novel 3NiFe/ CaO-3ZSM-5 catalyst was prepared through Fe doping and carrier modification to improve the H2 yield, carbon deposition resistance, and stability of toluene for hydrogen production. When the Ni:Fe molar ratio was 3:1 and the mass ratio of CaO to ZSM-5 was 1:3, the H2 yield from the 3NiFe/CaO-3ZSM-5 catalyst reached 97.5 % at 800 degrees C. Moreover, after 10 consecutive cycles, the toluene conversion rate at 800 degrees C was still as high as 100 %, and the H2 yield still reached 68.6 %. The promotion mechanism of Fe doping and carrier modification on the 3NiFe/CaO-3ZSM-5 catalyst was further analyzed. The results showed that Fe doping resulted in the formation of NiFeOx. The presence of NiFeOx effectively reduced the agglomeration and sintering of the Ni metal particles, increasing their dispersion and thereby improving the H2 yield of the catalyst. The addition of CaO to the carrier caused an even dispersion of the active components on the carrier surface and formed Ca2Fe2O5. Ca2Fe2O5 has multiple oxygen vacancies, which facilitate the migration of O2- and the diffusion of CO2. Moreover, the doping of CaO in the carrier increased the number of alkaline sites in the catalyst, which promoted the ability of the catalyst to capture CO2 and generate CaCO3. CaCO3 effectively reduced the generation of graphite carbon and amorphous carbon on the catalyst surface and weakened the adhesion of the generated carbon deposits on the catalyst. In addition, CaCO3 promoted the CO water gas and CH4 steam reforming reactions in the processing of toluene to produce hydrogen, thereby increasing the H2 yield.