低阶煤有机质缩合程度低，富含桥键和侧链，H/C和挥发分高，具有较高的化学反应性。催化加氢转化是从低阶煤中获取液体燃料和化学品的有效途径之一。然而，低阶煤氧含量和水含量高，在加氢转化过程中会增加氢耗和能耗，不利于油类的生成，且给产物分离带来困难。此外，催化加氢转化通常在高温高压条件下进行，产品组成复杂且重质化程度高，导致成本高但收益低。如何优化反应体系，进而提高低阶煤转化率和液体产物收率，是低阶煤催化加氢转化亟待解决的问题。催化剂是低阶煤催化加氢转化的核心，发挥着活化氢气、促进加氢转化和脱除杂原子的作用，直接决定反应体系苛刻程度和产物品质。反应条件作为反应体系另一组成要素，既可控制煤中共价键断裂速率及活性氢生成与转移，又能抑制缩聚反应，进而影响催化剂性能和产物组成分布。此外，预处理可以改变煤物理结构与化学活性，从而影响低阶煤催化加氢转化特性。本文综述了反应条件（温度、溶剂、气氛和压力）与预处理方法（热预处理、溶胀预处理、萃取预处理以及水热预处理）对低阶煤催化加氢转化或直接液化影响的研究进展，以及主要的低阶煤加氢转化催化剂，提出了下一步低阶煤加氢转化的研究方向，旨在启发研究者设计更高效的低阶煤加氢转化反应体系。

Low-rank coals (LRCs) are characterized by high chemical reactivity due to their low degree of coali-fication,high H/C atom ratio and high contents of bridge bonds,side chains as well as volatile matter.Catalytic hydroconversion (CHC) is one of the effective ways to obtain liquid fuels and chemicals from LRCs.However,high oxygen and moisture contents of LRCs,undesirably increasing the consumption of hydrogen and energy in CHC,is adverse to the formation of oil and results in difficulties to product separation.Meanwhile,CHC is usually conducted at high temperature under high pressure,and the product composition is complex with heavy fractions,leading to high cost and low return.Optimization of reaction system is a solution to improve the conversion rate of LRCs and the yield of liquid products,which is an urgent problem to be solved in the CHC of LRCs.Catalyst,a core technology in CHC of LRCs,plays an important role in activating hydrogen,promoting hydroconversion and removing heteroatoms,which directly determines the reaction system and product quality.Reaction condition,another component of the reaction system,can not only control the rate of covalent bond cleavage in coal,the generation and transference of active hydrogen,but also inhibit the polycondensation reaction,thereby affecting catalyst performance and product composition distribution.Additionally,pretreatment has an impact on the CHC characteristics of LRCs since it can change the physical structure and chemical reactivity of LRCs.This paper overviews the research progress of the effects of reaction conditions (temperature,solvent,atmosphere and pressure) and pretreatment methods (thermal pretreatment,swelling pretreatment,extraction pretreatment and hydrothermal pretreatment) on CHC or direct liquefaction of LRCs,as well as main catalysts used in LRCs hydroconversion.

1 低阶煤CHC的影响因素

   1.1 温度

   1.2 溶剂

   1.3 气氛

   1.4 压力

2 预处理的影响

3 催化剂

   3.1 铁基催化剂

   3.2 过渡金属催化剂

   3.3 酸催化剂

   3.4 固体超强碱催化剂

4 结语