Catalytic pyrolysis of tea waste biomass: Enhancing sustainable phenols and (H2+CO) production using a coke-resistant Fe-ZnO/Char catalyst

This study investigates the catalytic efficiency of a coke resistant Fe-ZnO/Char catalyst in the dual-stage pyrolysis-reforming of lignin-rich tea waste (TW), composed of 29.61 % lignin. This biomass serves as a viable source for phenolic-rich bio-oil and (H2+CO)-rich syngas. The incorporation of ZnO addresses prior issues with low phenol production and high coke formation while reducing CO2 emissions in syngas. Thermogravimetric analysis (TGA) indicates that a pyrolysis temperature of 600 °C optimizes the yield of volatile compounds. Under optimal conditions specifically, 10 wt% Fe, 5 wt% ZnO, a pyrolysis temperature of 600 °C, a reforming temperature of 700 °C, and a feed-to-catalyst ratio of 2:1, the phenol yield reached 65.7 %, and the combined yield of hydrogen and carbon monoxide (H2+CO) was 79.8 %. These conditions also resulted in reduced coke production, with 4.53 % for Fe-ZnO/Char compared to 6.41 % for Fe/Char. The catalyst was characterized with X-ray diffraction (XRD), scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), pyridine fourier-transform infrared spectroscopy (Pyridine-FTIR) and Brunauer-Emmett-Teller analysis (BET). These results highlight the great promise of bifunctional bimetallic catalysts for selective biomass transformation.