劣质柴油超临界均相加氢反应体系的构建和过程强化

As to increasingly stringent environmental regulations and leading position of FCC technology in refining industry, production of clean fuels from low quality diesel is great urgent in China. Hydrogen was supplied by recirculation system (circulating hydrogen or circulating oil) in the current diesel hydroprocessing processes. Hydrogen solvation and diffusional transport are two critical factors to reduce the efficiency of these processes. This project plan to construct a homogeneous hydrogenation environment to low quality diesel by introduce a supercritical solvent. The hydrogen solubility and interphase transport limitations are eliminated at supercritical conditions. Process intensification in the diesel hydroprocessing was achieved, and low quality diesel can be converted to clean fuel economically and efficiently. New technology of diesel supercritical hydrogenation can be developed thereafter. During the research process, the phase behaviors of diesel-solvent-H2 ternary system are obtained in this project by a visual PVT apparatus. The effect of solvents, diesel properties and composition of the ternary system on phase behavior are investigated. Based on determination of homogeneous phase conditions, suitable supercritical solvent is screened. The intensification effect of supercritical medium on the hydrogen solubility and diffusional transport is evaluated by comparison. The supercritical data and theory of complicated system can be improved thereafter.

日益严格的环保法规和催化裂化为主的炼油格局，造成劣质柴油高效清洁化已成为我国炼油行业面临的重要挑战。现有柴油加氢工艺均采用循环体系（循环氢或循环油）为反应供氢，造成氢气溶解和扩散传质制约了其过程效率。本项目针对这一化学工程问题，提出通过引入超临界溶剂从而构建劣质柴油均相加氢反应体系的新思路，克服现有工艺过程氢气溶解度低和扩散传质差的两个难点问题，实现柴油加氢反应中的过程强化，从而经济高效地将劣质柴油转化为清洁油品。重点考察柴油-溶剂-氢气三元复杂体系相态递变规律，研究溶剂种类、柴油组成性质和三元体系构成对其相行为的影响，在确定均相形成边界条件的基础上，优选实现劣质柴油均相加氢的适宜超临界溶剂，获得超临界介质对氢气溶解以及扩散传质性能的定量强化效果，并丰富复杂体系超临界流体数据和理论。

日益严格的环保法规和催化裂化为主的炼油格局，造成劣质柴油高效清洁化已成为我国炼油行业面临的重要挑战。现有柴油加氢工艺均采用循环体系（循环氢或循环油）为反应供氢，造成氢气溶解和扩散传质制约了其过程效率。基于此，本项目提出通过引入超临界溶剂从而构建劣质柴油均相加氢反应体系的新思路，从而经济高效地将劣质柴油转化为清洁油品。首先，课题应用可视相平衡仪进行了柴油-溶剂-氢气体系的相平衡实验，发现柴油组成和溶剂类型对体系相行为存在明显影响，引入正构烃类可降低体系的临界温度和提高临界温度，且变化幅度随碳数减小而增大。由此通过适宜溶剂选择和物料组成调控，可以实现劣质柴油均相加氢体系的构建。在此基础上，课题应用高压釜进行柴油以及柴油-溶剂二元物性的溶氢实验，表明优选的轻烃溶剂可以显著提高物料中的溶氢性能，可为劣质柴油高效加氢精制提供充足的有效氢。随后，课题应用固定床加氢装置系统考察了柴油常规加氢和超临界流体均相加氢工艺过程的转化效果，发现温度、压力、氢油比和空速对柴油加氢脱硫脱氮均存在显著影响，引入溶剂构建超临界流体均相加氢体系可以大幅提升柴油中硫氮化合物的脱除效果，而且新工艺对柴油中烷基取代的二苯并噻吩类硫化物和多环芳烃的加氢转化更具技术优势。最后，课题应用不同粒径的催化剂进行加氢脱硫反应动力学研究，发现工业尺寸催化剂中扩散阻力较大，抑制了加氢脱硫反应的高效进行，超临界流体的引入可以提高硫化物在催化剂中的扩散系数，从而缓解扩散对加氢脱硫反应的影响。基于上述实验结果可见，向柴油体系引入适宜溶剂构建超临界流体均相加氢体系，可以克服传统工艺过程氢气溶解度低和扩散传质差的两个难点问题，实现柴油的深度加氢精制，为生产优质车用柴油添加组分提供有效路径。