高含氧含水褐煤液化铁碱复合催化体系构建及作用机理研究

The liquefaction conversion of lignite to oils is a realizable and feasible way to alleviate the interdependecy of crude oils, due to the abundance of lignite reserves in our country. The high oxygen content of lignite can result in the production of waters with some quantities during the liquefaction process. Moreover, the high water (especially inner water) content of lignite can result in the increasing energy consumption during the drying process. Consequently, how to resolve the above shortcomings of lignite becomes a main problem for the liquefaction conversion technology of lignite to oils. Therefore, the construction of catalytic system with high efficiency, which is suitable for the liquefaction of lignite with high oxygen and water contents, appears very important. Up to now, the used catalysts for all industrial and pilot units of direct coal liquefaction are almost iron-based catalysts around the world. Obviously, the iron-based catalysts are very important for the coal liquefaction process. However, the present understandings of iron-based catalysts are only confined to those for direct coal liquefaction process under the organic solvent system, and the study on the iron-based catalysts for the lignite liquefaction process under the condition of high water content are not enough much. Especially, the investigations on the co-catalytic actions and the interaction effects of iron and alkali metals in the presence of CO and H2O are very scarce. Therefore, the study on construction and action mechanism of iron and alkali-based complex catalytic system for direct liquefaction of lignite with high oxygen and water contents is proposed in this project. This project can not only provide the theoretical foundation and basic data for the development of the iron and alkali-based complex catalytic system for direct liquefaction of lignite with high oxygen and water contents, but also has important theoretical significance and application value.

我国褐煤资源丰富，利用褐煤液化制油是减少原油对外依存度的现实而可行的途径。褐煤氧含量高(在液化过程中产生相当数量的水)和水含量高(内在水分高不易脱除且干燥耗能大)是其液化制油技术中亟待解决的主要难题之一,构建适合于高含氧高含水褐煤液化的高效催化体系显得尤为重要。迄今为止，国内外煤直接液化工业装置和中试装置几乎全部采用铁催化剂，可见在煤液化转化中铁催化剂具有十分重要的作用,然而,有关铁基催化剂的认识主要还局限于有机溶剂体系，对高含水条件褐煤直接液化铁催化剂的研究，尤其是对水与一氧化碳同时存在时铁与碱金属组分共同发挥催化作用及相互影响的研究几无涉及，相关的认识十分缺乏，也未见报道。以此为出发点，本项目拟提出高含氧含水褐煤直接液化铁碱复合催化体系构建及作用机理的研究。此项研究可为高含氧含水褐煤液化铁碱复合催化剂的开发提供理论依据和基础数据，具有重要的理论意义和应用价值。

我国褐煤资源丰富，利用褐煤液化制油是减少原油对外依存度的现实而可行的途径。褐煤氧含量高(在液化过程中产生相当数量的水)和水含量高(内在水分高不易脱除且干燥耗能大)是其液化制油技术中亟待解决的主要难题之一。本项目系统研究了褐煤高含氧及含水对直接加氢液化过程的影响，深入探讨了高含氧含水在不同液化阶段对不同反应组分转化的作用机制，揭示了褐煤加氢转化催化活性相组成及催化环境调控优化的途径，进而完成构建适用褐煤直接加氢液化的复合催化体系。研究表明，在铁催化剂催化褐煤液化过程中，添加碳酸钠能显著提高煤液化转化率和油产率，降低沥青烯产率和水产率。当碳酸钠添加量为5%时(FC:NC=1:1)，煤液化转化率从74.95%增加至86.34%，油产率从32.81%增加至51.33%。铁催化剂和碳酸钠在煤液化过程中存在协同作用，能促进前沥青烯和沥青烯向油的转化，降低了重质产物残渣的产率。当FC:NC=1:1时，铁碱催化剂表面积最大(12.97 m2/g)。在液化过程中，添加碳酸钠并未改变铁催化剂活性相磁黄铁矿的物相。铁碱催化剂催化红柳林煤液化时，先担载Na后担载Fe比同时担载Na和Fe表现出了更强的活性。铁碱催化剂能促进(H2+CO)混合气氛下的红柳林煤液化油收率。在高含氧含水褐煤液化不同阶段中，不同反应组分转化所需的环境不同。在较低的液化温度下，碱催化剂的加入即可脱除褐煤结构中的氧，且能促进褐煤中丰富的含氧结构(醚键和羰基键)水解，尤其能够促进褐煤结构中的芳香醚键水解，这一过程消耗掉部分液化过程产生的水，降低水产率。铁催化剂的作用更多的体现在高温下对褐煤结构的加氢，裂解，促进活性氢的活化。在CO气氛与含水溶剂系统下，当碳酸钠浓度为3%时，沥青质转化率为74.46%，油产率显著增加至57.06%。合成气气氛与含水溶剂系统下，铁硫体系对沥青质的转化具有显著的促进作用。本项目完成了适合于高含氧含水褐煤液化的高效催化体系的构建，同时也为高含氧含水褐煤液化铁碱复合催化剂的开发提供理论依据，对高含氧褐煤液化制油工业化提供了丰富的基础数据。