Gas-Phase Deoxygenation of Biomass Pyrolysis Tar Catalyzed by Rare Earth Metal Loaded Hβ Zeolite

Abstract

Biomass pyrolysis tar (BPT) with a higher heating value of 24.23 MJ/kg was used as raw feed for the catalytic gas-phase deoxygenation (GDO) process using Hβ zeolite loaded with different amounts of active elements (Ce, La, and Nd). Acetone molecule was chosen as a model compound to test the activity of pure Hβ zeolite, 1 wt% Ce/Hβ zeolite, 5 wt% Ce/Hβ zeolite, 1 wt% La/Hβ zeolite, 5 wt% La/Hβ zeolite, 1 wt% Nd/Hβ zeolite, and 5 wt% Nd/Hβ zeolite at 400 °C and process time of 3 h. BPT characterization showed a wide range of oxygenated compounds with the main components including water: 0.71%, furfural: 5.85%, 4-ethylguaiacol: 2.14%, phenol: 13.63%, methylethyl ketone: 5.34%, cyclohexanone: 3.23%, isopropanol: 4.78%, ethanol: 3.67%, methanol: 3.13%, acetic acid: 41.06%, and acetone: 16.46%. BPT conversion using 1 wt% Ce/Hβ zeolite catalyst showed the highest values of degree of deoxygenation (DOD) (68%) and conversion (16% for phenol, 88% for acetic acid, and 38% for 4-ethlyguaiacol). Yields of water, liquid phase, and gas phase in the GDO reaction using 1%Ce/Hβ zeolite were 18.33%, 47.42%, and 34.25%, respectively. Alkyl-substituted phenols and aromatic hydrocarbons achieved the highest yields of 37.34% and 35.56%, respectively. The main interaction pathways for BPT-GDO are also proposed.