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During pyrolysis, the intrinsic organic species in coals play an important role on the formation of tar but the relationship between them has not been elucidated in detail. In this study, the composition and structural characteristics of pyrolysis tars and soluble portions (SPs) via thermal dissolution from Baoqing lignite were analyzed with Fourier transform infrared spectroscopy (FTIR), gas chromatograph/mass spectrometer (GC/MS) and quadrupole/Orbitrap mass spectrometer (Orbitrap MS), and the formation mechanisms of main components in pyrolysis tars were proposed. FTIR analyses showed that both the SPs and tars are rich in -OH, C O, aromatic C C, C-O, aliphatic and aromatic C-H functional groups, suggesting they are partially similar in composition and structure. GC/MS and Orbitrap MS analyses indicated that a part of soluble organic species was directly volatilized into the tars, while others were suffered from complex reactions during pyrolysis, such as the cleavage of bridged bonds, the decomposition of oxygen-containing functional groups and the condensation of aromatics. Compared with the SPs, the higher contents of CH and O 1 classes but lower contents of O 2 -O 6 classes in the tars demonstrated that the soluble organic species are partially or completely deoxygenated during pyrolysis. [Display omitted] ● The yield of pyrolysis tars is obvious lower than that of soluble organic species. ● The components of tars are very closely related to soluble organic species. ● A part of soluble organic species is directly volatilized into pyrolysis tars. ● The soluble organic species were subjected to deoxygenation during pyrolysis. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fe/NC catalyst shows good activity and stability for cleaving C-O bonds in lignite. • Fe-N and Fe/Fe 3 C species in the catalyst were crucial to the catalytic activity. • Active hydrogen species were hydrogen radicals generated from H 2 and isopropanol. • The hydrocracking products have higher H/C ratio and heating values than lignite. • Catalytic hydrocracking promoted producing phenols via the cleavage of C-O bonds. Cleaving C-O bridged bonds of lignite via catalytic hydrocracking (CHC) is an effective method to produce chemicals and clean fuels. Herein, a nitrogen-doped carbon supported Fe catalyst was developed by using a one-pot method for CHC of Xilinguole lignite (XL) and its related model compounds. The doped nitrogen enhanced the interaction between Fe and N species to form Fe-N sites and favored forming smaller Fe/Fe 3 C nanocrystals, which played a crucial role in CHC performance. Toluene and phenol were produced from CHC of benzyl phenyl ether (BPE) with high yield and selectivity at 250 °C over the optimal catalyst with 4% Fe, without hydrogenation products. The Fe-based catalyst activated both H 2 and isopropanol to generate hydrogen radicals for cleaving C-O bridged bonds. The CHC of XL under different temperature and time showed that the yields of oil, asphaltene and preasphaltene were obviously promoted under 325 °C, 1 MPa, and 6 h, and they had much higher H/C ratio but remarkably lower O/C ratio, resulting in much higher heating values (28.19–36.90 MJ/kg) than XL. Phenols were the major group component with relative content of 53.6 wt% in oil from CHC, and the asphaltene and preasphaltene from CHC had obviously lower molecular weights, which could attributed to depolymerization of C-O bridged bonds in the XL macromolecular structures over the catalyst. [ABSTRACT FROM AUTHOR]

Ni and Zr modified nanosheet ZSM-5 zeolites as tandem catalysts were designed using co-impregnation method (Zr-Ni/S-Z5) or combining in-situ hydrothermal synthesis of Ni@S-Z5 and sequential impregnation of Zr (Zr/Ni@ S-Z5). Their applications in upgrading of lignite pyrolysis volatiles coupling with methanol to light aromatics were investigated. The results demonstrated that nanosheet zeolites with larger surface areas and shorter b-axis length benefited the production of light aromatics due to exposing more active sites and improved diffusion limitation compared with conventional ZSM-5 zeolites. Adding Ni and Zr into tandem catalysts further enhanced BTEXN yields, which was attributed to the induction of oxyphilic ZrO 2 for activating C Ar -O bonds combining the promotion of Ni for hydrogenation. Comparing to Zr-Ni/S-Z5 catalyst, lower BTEXN yield was observed due to the decrease in exposing active sites over Zr/Ni@ S-Z5 catalyst. Moreover, enhancing diffusion behaviors in shorter b-axis length and the presence of more fractions of external coke indicated less effective in blocking pore channels, thus nanosheet zeolite series showed lower deactivation rates. [Display omitted] • Nanosheet zeolites with larger surface areas and shorter b-axis benefited the production of light aromatics. • Adding Ni and Zr into tandem catalysts further enhanced BTEXN yields. • Nanosheet zeolites with more fractions of external coke presented lower deactivation rate. [ABSTRACT FROM AUTHOR]