昭通褐煤氨解可溶化转化及热溶物中氧和氮的赋存形态

Soluble conversion of Zhaotong lignite by ammonolysis and the occurrence forms of oxygen and nitrogen in soluble portion

褐煤碳含量高且富含氧、氮等杂原子,是制备炭材料的重要原料。但由于褐煤可溶有机碳含量低,杂原子分配无规律,导致以褐煤为原料制备炭材料面临诸多挑战。因此,亟需实现褐煤的可溶化转化。本研究以氨水为溶剂,旨在温和条件下,同步实现昭通褐煤的可溶化和褐煤热溶物中氧和氮的调控。实验结果表明,在氨水质量分数15%、温度160℃条件下反应3 h,热溶物收率最高为76.66%,昭通褐煤表现出良好的热溶效果。基于对热溶物的表征和分析,发现氨解在一定程度上改变了煤中的大分子结构,表现为氨基与羟基置换,或与部分羧基、羰基直接反应生成有机态氮。对比发现,原煤中氮元素赋存形态以季氮和吡咯氮为主,而可溶物中氮元素赋存形态以氨基氮和吡啶氮为主,表明褐煤氨解热溶过程产生了氨基或酰胺基。

Lignite is of high carbon content,rich in oxygen and nitrogen,and other heteroatoms,thereby is treated as an important raw material for the preparation of carbon materials.However,the preparation of carbon materials from lignite is faced with many challenges,due to the low soluble organic carbon content and the irregular distribution of heteroatoms.Therefore,it is necessary to achieve the soluble transformation of lignite.In this investigation,ammonia was applied to achieve the solubilization of Zhaotong lignite,and also the regulation of oxygen and nitrogen in soluble portion from lignite under mild conditions.As a result,Zhaotong lignite exhibits efficient thermal dissolution with a soluble portion yield of 76.66%,at the condition of ammonium concentration of 15%,temperature of 160℃,and reaction time of 3 h.Based on the characterization and analysis of soluble portion,the macromolecular structure of coal is changed by ammonolysis,mainly displaying the replacement of the hydroxyl group by the amino group or the formation of organic nitrogen groups by the direct reaction between the carboxyl or carbonyl groups with the amino group.By contrast,the occurrence forms of nitrogen in raw coal are mainly quaternary nitrogen and pyrrole nitrogen,while they in soluble matter are mainly amino nitrogen and pyridine nitrogen,indicating that amino or amide groups are formed during the thermal dissolution of lignite.