Study on the synergistic effect between Ni and Me species over Ni-Me/HZSM-5 on the in-situ catalytic pyrolysis of alkali lignin

Abstract

The research is to investigate synergistic effect between Ni and Me over Ni-Me/HZSM-5 (Me = Zn, Cu, Pd) on in-situ catalytic pyrolysis of alkali lignin at 550 °C in N2. The results showed that Ni and Cu, Zn formed Ni0.8Cu0.2O, Ni0.9Zn0.1O, respectively, yet Ni and Pd formed NiO and PdO. The synergistic effect of Ni-Cu was regarded as intramolecular synergism, realizing both the lowest yield of bio-oil (37.7 wt. %) and the highest yield of gas (18.5 wt. %) with 55.3 vol. % of H2 among all catalytic tests, which were attributed mainly to Ni0.8Cu0.2O and its strong Lewis acidity. The effect of Ni-Zn was similar to that of Ni-Cu, being weaker than that from Cu. The effect of Ni-Pd was considered as intermolecular synergism, bringing about similar results to those displayed by Ni-Cu/HZSM-5. It is feasible to substitute non-precious metal for noble metal in the preparation of catalyst for H2-rich gas.