Aromatic hydrocarbon production by the online catalytic cracking of lignin fast pyrolysis vapors using Mo2N/γ-Al2O3

Abstract

This study investigates the online catalytic cracking of lignin fast pyrolysis vapors using Mo2N/γ-Al2O3 prepared by nitriding an alumina-supported molybdenum oxide precursor with nitrogen hydrogen mixtures though temperature programming. The activity and selectivity of the catalyst toward aromatic hydrocarbons were determined in the pyrolysis-gas chromatography/mass spectrometry system. Results show that the catalyst has a significant function in the pyrolysis process. In the presence of the catalyst, the primary pyrolysis products from lignin are catalytically converted into aromatic products, benzene and toluene, as well as to an insignificant quantity of dimethylbenzene, ethylbenzene, trimethylbenzene, and naphthalene. The highest aromatic hydrocarbon yield of 17.5% is obtained using Mo2N/γ-Al2O3 (the catalyst-to-lignin weight ratio=4) at 700°C; by contrast, this yield is only 1.4% when no catalyst is used. Furthermore, the highest benzene yield of 70.1% is obtained using Mo2N/γ-Al2O3 (catalyst-to-lignin weight ratio=4) at 850°C. Under this condition, the monocyclic aromatic hydrocarbons together contribute >95% of the total aromatic hydrocarbon yield, whereas the selectivity toward naphthalene is only 2.2%.