煤直接液化溶剂研究述评

Research progress and prospects of coal direct liquefaction solvents

  • 摘要: 近 3 a我国石油对外依存度达70%以上,严重威胁到了国家能源安全,稳步发展煤直接液化制油技术对于缓解我国油品短缺和促进煤的清洁高效利用具有重要的现实意义。为深入了解煤直接液化溶剂的重要性及溶剂中的氢传递机制,较全面地总结对比了国内外煤直接液化工艺的发展历程,重点介绍了神华集团开发的煤直接液化工艺在溶剂方面以及反应条件上的改进。首先,阐述了煤直接液化溶剂在物理、化学方面的重要作用,溶剂中极性化合物对反应的影响以及溶剂之间的相互作用对煤加氢液化反应的影响,溶剂不仅具有溶胀、分散煤的作用,还能溶解氢气、供氢和传递氢、稳定和保护煤热解生成的自由基,促进煤大分子中键的断裂。其次,依据全二维气相色谱-飞行时间质谱/氢火焰离子化检测器定性定量分析得到溶剂的组成和分子结构,探讨了煤直接液化溶剂的评价方法,如特性因子法、红外吸收光谱法和核磁共振法等。第3,深入分析了煤直接液化溶剂氢转移机制,如氢穿梭机制、氢解机制、热解自由基机制和协同-双氢转移机制,以及操作条件温度和压力对煤直接液化氢转移机制的影响。最后,对于如何降低企业运行成本和提高液化反应的碳转化率和目标产物收率,围绕液化溶剂应开展的工作提出了建议。

     

    Abstract: In the past three years,China’s external dependence on oil has reached over 70%,seriously threatening national energy security. The steady development of direct coal liquefaction technology for producing the oil could compensate for the shortage of oil resources,and promote the clean and efficient utilization of coal in China. To gain an indepth understanding about the importance of solvent for direct coal liquefaction and the hydrogen transfer mechanism,the authors summarized and compared the development history of the direct coal liquefaction processes worldwide,with the special emphasis on the improvement of direct coal liquefaction process developed by Shenhua Group in terms of solvent. The important roles of solvent during direct coal liquefaction in both physical and chemical aspects,the effect of polar compounds on solvents,and the interaction between solvents on coal hydrogenation and liquefaction reactions were discussed. Solvents not only have the role of dissolving and dispersing coal,but also dissolve hydrogen,supply and transfer hydrogen,and stabilize and protect free radicals generated by coal pyrolysis,and promote the cleavage of bonds in coal macromolecules. The composition and molecular structure of solvents were obtained by qualitative and quantitative analysis by using a full twodimensional gas chromatographytimeofflight mass spectrometry/hydrogen flame ionization detector. Also,the evaluation methods of coal direct liquefaction solvents such as the characteristic factor method,infrared absorption spectroscopy and nuclear magnetic resonance method were discussed. The progress of research on the different hydrogen transfer mechanisms of coal direct liquefaction solvents,such as hydrogen shuttle mechanism,hydrogenolysis mechanism,pyrolysis radical mechanism and synergisticbihydrogen transfer mechanism,was highlighted and the effect of temperature and pressure on the hydrogen transfer mechanism of coal direct liquefaction was discussed. At present,the research on liquefaction solvents is not sufficient enough,and the investigation should focus on the composition of solvent and hydrogen transfer mechanism in the future,which is important for reducing the production cost of enterprises and improving the oil yield and conversion of target products.

     

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