Effect of MgO promoter on Ni-Mg/ZSM-5 catalysts for catalytic pyrolysis of lipid-extracted residue of Tribonema minus

Abstract

The catalytic pyrolysis of lipid-extracted residue of Tribonema minus with a biomass to catalyst mass ratio of 1:2 has been performed in a fixed-bed reactor. In this paper the influence of Ni-Mg/ZSM-5 catalysts with Ni/Mg ratio (6:1, 6:2, 6:3 and 6:4) and catalyst Si/Al ratio (25, 50, 80 and 360) on products yields and composition were investigated. The catalytic characterization results indicated that the addition of MgO is beneficial to the dispersion of NiO in the ZSM-5. The pyrolysis process shown that the metal-modified ZSM-5 catalysts can enhance secondary cracking and decomposition reaction, resulted the gas product increasing with the liquid product yield decreased. The Ni-Mg/ZSM-5 catalysts lead to a decrease of acids and esters, and an increase of the hydrocarbons fraction. With the Ni(6%)-Mg(2%)/ZSM-5 catalyst (Si/Al=50) treatment, the bio-oil product contained the highest hydrocarbon compounds with a yield of 35.52% (12.94% for aliphatic HC and 22.58% for aromatic HC) and maximum alkylbenzene content (8.48%), lower total PAHs concentration (14.10%) and lower acids yield (0.30%).