Study On The Conversion Of Alkali Depolymorized Products From Shengli Lignite

The efficient and clean utilization of coal-based heavy carbon resources is crucially importantfor the sustainable development of national economy. In this study, NaOH depolymorizedproducts （SDP） of Shengli （SL） lignite was used as the model compounds of coal-based heavycarbon resources. Hydrotreatment of SDP and preparation of carbon materials based on SDPwere investigated. The characteristics of the SDP, the performance of catalysts such as solidacid catalysts, Ni-Mo-S/Al₂O₃and Ni-Mo-S/Zr（Ti）-Al₂O₃used for SDP hydrogenation andproduct distribution resulted from hydrogenation of SDP were primarily investigated. Thefeasibility of the preparation of carbon materials using SDP as precursor was preliminarilyprobed.The results show that SDP contain the oxygen-containing groups, aromatic and aliphaticstructures. The main product of SDP hydrogenation was tetrahydrofuran soluble fraction（THFS）, which contains1to3rings aromatic structure probably linked by alkyl chains andaliphatic rings.The SDP were found hydro-treatable, resulting in lighter products-hexane soluble fraction（HS） and gas. The preliminary screening of hydrogenation catalysts showed that solid acidcatalysts have low catalytic activities on the hydrogenation of SDP. Ni-Mo-S/Al₂O₃catalystshowed higher activity towards the hydrogenation of SDP. THFS was the most activecomponent during the hydro-treatment, which can be easily converted into HS. The percentageof THFS decreases70.7wt%while the percentage point of HS increases63.8wt%at400oCand initial H₂pressure of5MPa in the presence of Ni-Mo-S/Al₂O₃.The addition of Zr（Ti） to Ni-Mo-S/Al₂O₃significantly increased the conversion of SDP, andthe yield of HS by64.8%and inhibited the formation of tetrahydrofuran insoluble （THFI）. Evenmore important, Ni-Mo-S/Al₂O₃and Ni-Mo-S/Zr-Al₂O₃catalysts show better performance forthe hydrogenation of SDP during consecutive use. The HS yield could still approach to62.5%after3cycles. The HS resulted from the hydrogenation of SDP over Ni-Mo-S/Al₂O₃orNi-Mo-S/Zr（Ti）-Al₂O₃mainly contains benzene, toluene, naphthalene, anthracene, and a few ofpyrene. The addition of Zr to Ni-Mo-S/Al₂O₃can significantly promote the formation ofnaphthalene and increase HS by about19.4%compared to that obtained over Ni-Mo-S/Al₂O₃.The high hydrogenation activity of Ni-Mo-S/Zr-Al₂O₃catalyst can be attributed to the weak interaction between active metal and support, the increase of the acidity and the change of themorphology of MoS2（the increase of the stacking degree and length of MoS2） by the additionof Zr to Ni-Mo-S/Al₂O₃.The kind of the template and temperature significantly affected the morphology of carbonmaterials using SDP as precursor. Carbon micro-spheres （CMSs） can be synthesized bysurfactant-assisted self-assembly method when Cetyltrimethyl Ammonium Bromide （CTAB）was used as the template. CMSs prepared at600oC have a spherical morphology, smoothsurface, probable size of about5-10μm. The prepared CMSs are amorphous carbon, and have arelatively high thermal resistance and a good stability.