Development of Ni-doped Fe/Ca catalyst to be used for hydrogen-rich syngas production during medicine residue pyrolysis

In this work, the catalytic pyrolysis of herbal residues (HR) by Ni–Fe/Ca catalysts and the effects of intrinsic ash and heating rate on the activity of Ni–Fe/Ca catalysts were investigated in a fixed-bed reactor. The results showed that the strong interaction of Fe and Ca formed Ca2Fe2O5, which inhibited the formation of CaCO3, shifted the weakly and moderately acidic sites to high temperatures, promoted the conversion of tar and char, and inhibited the formation of CO2. The H2 yield increased to 54.6 mL/g at 5% Fe/Ca catalyst. The addition of Ni to Fe/Ca improved the catalyst dispersion and promoted the adsorption of alkaline sites, while Ni formed a stable Fe3Ni2 alloy with Fe. The yields of H2 and CO increased from 54.6 mL/g and 63.4 mL/g (0.5% Fe/Ca) to 95.5 mL/g and 70.0 mL/g (0.5% Ni–Fe/Ca), respectively. The CO2 generation was suppressed at high temperatures and the calorific value of pyrolysis gas was significantly increased. Moreover, the acid wash pretreatment improved the tar yield, the alkaline sites in the Ni–Fe/Ca catalyst contributed to the conversion of aromatics and the reforming of CO2, and the presence of AAEMs promoted the redox reaction between gas and solid. The increase in the heating rate (100 °C/min) was beneficial to improve the activity of the Ni–Fe/Ca catalyst. The yields of H2 and CO reached 121.7 mL/g and 71.9 mL/g, respectively.