| Light aromatic hydrocarbons(BTEXN)such as benzene,toluene,ethylbenzene,xylene and naphthaleneare widely used in the industry as high-value raw materials.Refining of coal retorting tar is one of the important production methods of BTEXN.In this paper,we carry out fast pyrolysis research on Xinjiang high-alkali coal in order to expand the applications of Xinjiang high-alkali coal in chemical industry.Two typical high-alkali coals from Xinjiang which called Hongshaquan and Jiangjunmiao,which prepeared through the two pretreatment methods of sequential extraction and external addition of sodium,was used to semi-quantitatively study the effect of sodium form and content in high-alkali coal,as well as the types of mineral components on the fast pyrolysis tar and BTEXN precipitation characteristics by Py-GC/MS.At the same time,the influence of inherent minerals on the structure of high-alkali coal was explored through FTIR.Later,the application and feasibility of the inherent minerals of high-alkali coal were explored by adding coal ash from an external source.The results show that the inherent minerals in both high-alkali coals could increase the precipitation of tar and BTEXN for which the water-solubl(Na,Ca)minerals played a key role.Endogenous water-soluble minerals and ammonium acetate-soluble minerals which mainly based on sodium and calcium both increased the precipitation of Hongshaquan coal tar by 22%and 55%.However,the addition of water-soluble NaCl and ammonium-acetate-soluble CH3COONa from external sources reduced the precipitation of Jiangjunmiao coal tar.Water-soluble minerals,1.0 wt%NaCl and CH3COONa respectively increased the precipitation of BTEXN in coal tar by 45%,42%and 62%.However,the ammonium acetate soluble substance and low content(0.4 wt%)Na will inhibit the precipitation of BTEXN.The gradual extraction and deashing treatment had certain effects on the structure of high-alkali coal.The gradual extraction and deashing treatment had a certain influence on the structure of high alkali coal,and each mineral type had a significant influence on the absorption peak of the functional group structure Both ammonium acetate washing and water washing suppressed the absorption peak intensity of COO-and carboxylic acid structures.And pickling could significantly promote the absorption peak intensity of COO-and carboxylic acid structure,because pickling can significantly removed the metal attached to COO-.High-alkali coal ash(intrinsic mineral)could be used as an efficient and cheap coal-based BTEXN catalyst.Coal ash could significantly promote the formation of BTEXN in tar(38.4%),because ash could promote the conversion of polycyclic aromatic hydrocarbons to BTEXN. |
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