Analysis Of Shengli Lignite Pyrolysis Products And Construction Of Typical Char’s Molecular Structure Model

Lignite reserves in China is abundant, relative research spots concerning to lignite were focused on pyrolysis, gasification, liquefaction and combustion. Study on molecular structure of lignite by pyrolysis is also a hotspot. Shengli lignite was chosen as the study subject to analyze the effects of pyrolysis conditions on the products. The average molecular model of the char under 350 ℃ and 500 ℃ were build respectively, which assisted by elemental analysis, FTIR spectroscopy and13C-NMR analysis. The study showed that:The influence of temperature on the Shengli lignite pyrolysis products indicated that with the temperature rising, the char’s yield was reduced while the yield of pyrolysis water and gas were increased. The decrement of C=O content was unconspicuous when temperatures of 350-400 ℃, and the bond of C=O started breaking to produce CO when temperatures is greater than 400 ℃. The coal samples content of absorbing water were decreased with the temperature rising. Under the different RVP, the equilibrium adsorption water content was showed a linear relationship with the content of-OH and C=O, whereas showed a weak linear inclination with-O- content. The percentage of phenols was the largest in tar, which reached to 36.99% under the temperature of 500 ℃. And the aliphatic compounds were mainly composed of alkane.The influence of retention The influence of retention time on the Shengli lignite pyrolysis:With the extension of retention time, the functional group absorption peak area percentage was decreasing, and the variation was comparatively fiercer when the retention time was 5-10 min. With the extension of heat preservation time, coal samples content of absorbing water reduced gradually. With the extension of retention time, it reached its maximum at approximate 20 min, the change turned into a mitigatory state after 20 min.350 ℃ char’s average molecule model was established by experiments and the stability of molecular structure. The molecular formula of model structural was C142H116O38N2. The structure features were listed as: the structure of aromatic compounds mainly composed of benzene rings, while fat structure was presented in the form of short-chain fatty, the oxygenous groups mainly belonged to cover hydroxygrou, carbanyl group and ether bond group types. Furthermore, FT-IR ofbrown acid model was also calculated with HF/3-21 G. FT-IR experiments correlated well with that obtained by calculating, which suggested that the result was reasonable.500 ℃ char’s average molecule model was established by results of elemental analysis, FT-IR spectroscopy, and13C-NMR analysis. The molecular formula of molecule model was C92H88O21. The structure features were: the structure of aromatic compounds were mostly benzene rings, aliphatic carbon atoms was low, which was a shorter aliphatic chain. The oxygenous group was mainly consisted of ether linkage and carbanyl group. The same calculation method was used to evaluate its FT-IR which correlated well with that obtained by experiment.