The effect of reaction condition on catalytic cracking of wheat straw pyrolysis volatiles over char-based Fe–Ni–Ca catalyst

In this study, the catalytic reforming of wheat straw pyrolysis volatiles over char-based Fe–Ni–Ca catalyst in a fixed bed reactor to investigate the influence of heating rate, pyrolysis temperature and catalyst calcination temperature on the yield of bio-oil, char and pyrolysis gas was presented. Char-based Fe–Ni–Ca catalysts had good activity for the removal of heavy oil, the heavy oil yield is 0.43% with 500 °C pyrolysis temperature and 5 °C/min heating rate. The maximum yield of hydrogen (288.41 mL/g) and combustible gas (hydrogen, methane and carbon monoxide; 403.45 mL/g) were obtained at a pyrolysis temperature of 800 °C and 10 °C/min heating rate. XPS, H2-TPR, XRD, TEM, SEM-EDS and BET were employed to analyze char-based Fe–Ni–Ca catalyst. Characterization results reveal that heating rate, pyrolysis temperature and catalyst calcination temperature had a significant effect on the distribution of active phase. Comparing to 800 °C, the diffraction peaks of Fe, Fe0.64Ni0.36, and Fe2O3 become weak as 500 °C, the particle size changed from 23.17 nm to 24.34 nm. At 500 °C, the power of the diffraction peak decreases successively from Fe2O3, Fe, and Fe0.64Ni0.36. At 800 °C, the highest intensity of the diffraction peak is Fe, followed by Fe2O3. The high activity of char-based Fe–Ni–Ca catalyst is also attributed to the robust adsorption of CO2 forming CaCO3 species facilitated on the oxide ion vacancy site of CaO acting as oxygen exchange site. Also, the char-based Fe–Ni–Ca catalyst can be utilized as an appropriate candidate to crack the bio-oil. The pyrolysis temperature of 800 °C and the heating rate of 10 °C/min can be used as the best reaction conditions for industrial hydrogen production.