331 / 2018-07-30 04:21:29

Selective preparation of monocyclic aromatic hydrocarbons

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In-situ or ex-situ catalytic pyrolysis of biomass with zeolite HZSM-5 provides an efficient way to selectively produce monocyclic aromatic hydrocarbons (MAHs), but a lot of polycyclic aromatic hydrocarbons (PAHs) will be formed together with MAHs. In this study, in order to inhibit PHAs formation and promote MAHs formation, Ti(SO4)2-Mo2N/HZSM-5 catalyst was prepared and employed for ex-situ catalytic pyrolysis of pine to selectively produce MAHs accompanied with low PAHs, via both analytical pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and lab-scale pyrolysis experiments. Analytical Py-GC/MS experiments were firstly performed to compare the catalytic performance of HZSM-5, Mo2N/HZSM-5, Ti(SO4)2/HZSM-5 and Ti(SO4)2-Mo2N/HZSM-5 catalysts. Moreover, based on Ti(SO4)2-Mo2N/HZSM-5 catalyst, the effects of pyrolysis temperature and catalyst-to-pine ratio on the aromatics formation were investigated. Furthermore, lab-scale experiments were conducted the quantitatively determine the pyrolytic products. The Py-GC/MS results indicated the maximal MAHs yield reached as high as 12.53wt% from the Ti(SO4)2-Mo2N/HZSM-5 catalyst at 650oC and catalyst-to-pine ratio of 7, together with the PAHs yield of only 1.10wt%. Correspondingly, the yields of MAHs and PAHs from HZSM-5 under the same condition were 7.57wt% and 2.55wt% respectively, which clearly indicated the catalytic capability of the Ti(SO4)2-Mo2N/HZSM-5 catalyst to inhibit the formation of PAHs while promoting the MAHs. Moreover, the lab-scale results showed that compared with the HZSM-5, the Ti(SO4)2-Mo2N/HZSM-5 catalyst resulted in the increased liquid and gas products, and decreased solid product. Under optimal conditions of 650oC and catalyst-to-pine ratio of 4/3, the actual yields of MAHs from Mo2N/HZSM-5 and Ti(SO4)2-Mo2N/HZSM-5 catalysts were 6.38wt% and 9.71wt%, respectively. In addition, the recycling experiments confirmed that the Ti(SO4)2-Mo2N/HZSM-5 catalyst possessed better anti-deactivation ability than the HZSM-5 catalyst.