褐煤直接液化制备高品质化学品及液体燃料过程中的化学基础

Developing advanced lignite direct liquefaction technology for the production of high-quality chemicals and liquid fuels is of great strategic and practical significance to deal with the severe situation of coal chemical engineering industry. Since lignite has the characteristics of high water and oxygen contents, traditional direct liquefaction process consumes plenty of hydrogen and yields large amounts of phenol water. In addition, the downstream upgrading processes do not thoroughly take the structural characteristics of lignite into account, therefore the processing costs and energy consumption are rather high without a clear product positioning. In consideration of element utilization and environmental impacts, this project propose a strategy including oxygen protection during liquefaction and group component separation, aiming at producing hydrogenated aromatics/cycloalkanes and monophenols. The migration rules and evolution pathways of oxygen in lignite will be studied, based on which the oxygen-containing groups, such as phenolic hydroxyl groups, will be catalytically converted into phenolics instead of water. The whole liquefaction oil will be separated by employing extraction agents to adjust the partition coefficients among the chemical groups. The obtained group components will be upgraded via selective hydrogenation, wherein the abilities of the removal of heteroatoms, selective ring opening and shape-selective hydrogenation will be evaluated and the selective hydrogenation mechanism will be elucidated; thereby the catalyst design methods applicable to liquefaction oil will be developed.

开发先进褐煤直接液化油品制备高品质化学品及液体燃料技术对于应对煤化工当前严峻形势具有重要的战略和现实意义。因褐煤具有高水分、高氧含量的特点，传统直接液化工艺具有氢耗高且产物中含有大量酚水，进一步提质加工成本、能耗高，目标产品定位模糊，工艺未能充分考虑褐煤结构特点。针对这些问题，综合考虑元素利用、环境影响等因素，本项目提出褐煤直接液化过程氧保护、族组分分离、氢化芳烃/环烷烃及单酚为目标产品的褐煤液化油提质加工思路。研究通过对褐煤中氧迁移规律和演化途径的认识，利用催化剂对酚羟基等含氧官能团反应机理的调变，限制水的生成使之形成酚类产品；在此基础上，利用萃取剂调整族组分间分配系数以实现液化油的高效全馏分分离；所得族组分分别进行选择性加氢提质，考察加氢催化剂脱除杂原子、选择性开环、空间择形氢化等性能，揭示选择性加氢机理，开发适应于液化油组成的催化剂设计方法。

褐煤具有高水分、高氧含量和高反应性的特点，传统褐煤直接液化工艺未能充分考虑褐煤结构特点，使得工艺过程氢耗高且产物中组分复杂，油水分离困难，进一步分离提质加工成本和能耗较高。为针对性利用褐煤的结构特点，本项目通过对褐煤液化过程中氧的衡算及其在反应过程中的物流分布考察，对褐煤中氧迁移规律进行研究，利用CUS-Fe催化剂对液化过程中褐煤结构中以酚羟基为代表的等含氧官能团反应进行调变，抑制产物水的生成以降低油水分离成本；在此基础上，探索复配的DES低共融溶剂作为萃取剂，调整产物组分间分配系数，实现高含酚液化油的高效全馏分分离；为进一步提升产品品质和附加值，研究以单酚为目标产品，考察多级孔结构的分子筛对液化油中杂酚的裁剪，最大限度的提高氧在有效产物中的利用率；此外，针对煤液化油中氮含量高达4000ppm的脱氮难点，利用TiO2改性的NiMoS催化剂脱除液化油中特有的高含量的N组分，以实现油品的超净要求；为了进一步制备高能量密度液体燃料，利用磷化物催化剂Ni2P，对以萘为稠环芳烃模型化合物进行反应过程研究，研究芳烃加氢饱和和异构的反应机理；在获得以上关键反应单元数据的基础上，利用流程模拟软件构建并优化了褐煤直接液化制备高质高值产品的工艺体系。