Selective preparation of monocyclic aromatic hydrocarbons from ex-situ catalytic fast pyrolysis of pine over Ti(SO4)2-Mo2N/HZSM-5 catalyst

Abstract

To selectively produce monocyclic aromatic hydrocarbons (MAHs) with low amount of polycyclic aromatic hydrocarbons (PAHs), modified HZSM-5 catalysts (Mo2N/HZSM-5, Ti(SO4)2/HZSM-5 and Ti(SO4)2-Mo2N/HZSM-5) were prepared and employed for ex-situ catalytic fast pyrolysis (CFP) of pine wood. Both analytical pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and lab-scale pyrolysis experiments were conducted to investigate the effects of catalyst, pyrolysis temperature and catalyst-to-pine ratio on the distribution of aromatic hydrocarbon products. Py-GC/MS results showed that the maximal MAHs yields from the HZSM-5, Mo2N/HZSM-5, Ti(SO4)2/HZSM-5 and Ti(SO4)2-Mo2N/HZSM-5 catalysts were 7.57 wt%, 8.11 wt%, 8.71 wt% and 12.53 wt% at 650 °C and catalyst-to-pine ratio of 7. Corresponding PAHs yields from the four catalysts were 2.55 wt%, 0.97 wt%, 1.47 wt% and 1.10 wt%, which clearly indicated that the Ti(SO4)2-Mo2N/HZSM-5 significantly increased MAHs formation and decreased PAHs formation as compared with HZSM-5. Furthermore, lab-scale experiments were conducted to quantitatively determine the pyrolytic product distribution. Results showed that Ti(SO4)2-Mo2N/HZSM-5 catalyst increased the yield of liquid and gas products, and decreased solid products as compared with HZSM-5. Under optimal conditions of 650 °C and catalyst-to-pine ratio of 4/3, the actual yields of MAHs and PAHs from Ti(SO4)2-Mo2N/HZSM-5 catalyst were 9.71 wt% and 1.45 wt%, respectively. In addition, stability tests confirmed that the Ti(SO4)2-Mo2N/HZSM-5 catalyst possessed better effects on MAHs production as well as anti-deactivation than the HZSM-5.