Selective preparation of monocyclic aromatic hydrocarbons from catalytic cracking of biomass fast pyrolysis vapors over Mo2N/HZSM-5 catalyst

Abstract

Fast pyrolysis of biomass followed by catalytic cracking of pyrolysis vapors over zeolite catalysts offers a promising way to produce monocyclic aromatic hydrocarbons (MAHs). However, many polycyclic aromatic hydrocarbons (PAHs) will be formed accompanied with MAHs. To solve this problem, a series of noble metal-like catalysts prepared by Mo2N, W2N, MoP and WP supported on Hβ, HY and HZSM-5 were used for catalytic conversion of biomass fast pyrolysis vapors to prepare aromatic hydrocarbons rich in MAHs but with low PAHs. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) experiments were conducted to analyze the pyrolytic product distribution and evaluate the catalyst performance. Major aromatic hydrocarbons were quantitatively determined. Moreover, deactivation properties of catalysts were examined via recycling experiments. The results indicated that among the noble metal-like catalysts, Mo2N/HZSM-5 showed the best selectivity for MAHs. Compared with HZSM-5 catalyst, the modification with Mo2N could significantly decrease the formation of PAHs, while slightly increase MAHs, and also improve the anti-deactivation property of the catalyst. Under optimal conditions of 750 °C and catalyst-to-biomass ratio of 5, the actual yields of MAHs from HZSM-5 and Mo2N/HZSM-5 catalysts were 8.08 wt% and 8.19 wt% respectively, while the yields of PAHs were 2.37 wt% and 0.88 wt%.