煤直接液化是煤加氢转化、定向生产高品质燃料和高附加值化学品的有效途径之一。煤直接液化过程是由煤、氢气、溶剂和催化剂组成的复杂反应体系，涉及气相、液相、固相3相间的物料传递和反应。其中溶剂具有传递氢和提供氢的作用，催化剂可促进煤裂解反应和加氢稳定煤裂解的大分子碎片反应，如何有效协调并发挥催化剂和溶剂在煤氢解反应中的作用，将决定煤氢解反应液体产物的结构组成和收率。为此，首先概括煤中典型模型化合物如芳烃、芳基烷烃、含硫/氧/氮/卤素等杂原子芳香族化合物热解研究动态，简述含不同官能团的芳香族化合物在常用溶剂、重质油溶剂和有机废弃物溶剂中发生的物理化学结构变化及其对后续煤加氢反应效果的影响，具体分析了溶剂对煤的溶胀作用、传递氢和提供氢作用机制；其次，介绍了煤直接液化的自由基反应机理，分析了当前用于煤直接液化研究较多的金属、金属氧化物、金属硫化物和酸性催化剂（金属卤化物）特点及其催化作用；探讨了煤直接液化工艺氢传递过程中可能存在的溶剂与催化剂的协同作用，该作用不仅可促进煤氢解反应，提高煤直接液化油收率，而且可以调变液体产物结构组成。最后，为进一步提高煤液化收率，在强化溶剂和催化剂协同作用方面提出了具体研究内容和方法。

Direct coal liquefaction (DCL) is one of the effective ways for coal-hydro conversion and directional production of high-quality fuels and high value-added chemicals. The direct coal liquefaction process is a complex reaction system composed of coal,hydrogen,solvent and catalyst,involving the material transfer and reaction of gas phase,liquid phase and solid phase. While the solvent acts as hydrogen source during DCL,the catalyst promotes the hydrogenation of macromolecules and thermal cracked fragments of coal. How to effectively coordinate and play the role of catalyst and solvent in coal hydrogenolysis reaction will determine the structure composition and yield of liquid products of coal hydrogenolysis reaction. The pyrolysis of typical model compounds in coal,such as aromatics,alkylaromatics,and hydrocarbons having sulfur/oxygen/nitrogen/halogen,etc. was summarized,and the changes observed on the physicochemical properties of these compounds in common solvents,heavy oil solvents and organic waste solvents were discussed,which might affect the subsequent hydrogen-assisted liquefaction. The mechanism of solvent swelling,hydrogen transfer and hydrogen supply to coal was analyzed. A brief introduction was given on the free radical reaction and catalytic liquefaction mechanism occurring during the DCL. The role and status of various DCL catalysts such as metals,metal oxides,metal sulfides,and solid acids (e. g. metal halides and others) were described with a special emphasis on iron-based catalysts. Then,the possible synergistic effect of solvent and catalyst in the hydrogen transfer process of direct coal liquefaction process was discussed. This effect can not only promote the coal hydrogenolysis reaction,improve the yield of direct coal liquefaction oil,but also adjust the structure of liquid products. Finally,in order to further improve the yield of coal liquefaction,the specific research contents and methods in strengthening the synergistic effect of solvent and catalyst were put forward.

0 引言

1 煤直接液化反应机理

   1.1 自由基机理

   1.2 氢解机理

   1.3 碳正离子加氢机理

2 煤氢解反应中溶剂作用及种类

   2.1 溶胀作用

   2.2 供氢与传递氢作用

   2.3 溶剂种类

3 煤氢解反应催化剂

4 催化剂和溶剂在氢传递中的作用

5 结语与展望