功能化聚乙二醇的结构设计及其燃油萃取脱硫脱氮性能调控机理

Polyethylene glycol (PEG) is a green extractant, but not satisfactory for S- and N-removal from fuel oil. For desulfurization, the terminal –OH of PEG causes the intermolecular H-bonding, which covers the Lewis base site and thus hinders the S-removal. Etherification of terminal group can completely deprotonate PEG，entirely eliminate the intermolecular H-bonding, and accordingly improve the desulfurization performance. However, the etherified PEG is deficient in polarity, and thus its S-selectivity is not good. For denitrogenation, PEG shows weak Brønsted acidity. Thus, it is only effective for non-basic nitrogen, but not active for basic nitrogen. Carboxylation of terminal group can enhance the acidity of PEG and accordingly realize the removal of both basic and non-basic nitrogens. However, carboxylized PEG still has the intermolecular H-bonding, which hinders the N-removal. For the better desulfurization, this project will further modify etherified PEG (or PEG) via sulfonylation and imidazolization to enhance the Lewis basicity and polarity. For the better denitrogenation, this project will modify carboxylized PEG via forming deep eutectic solvent to weaken the intermolecular H-bonding. Moreover, this project aims to design the structure of functionalized PEG mentioned above, to control the distribution of its active groups, to explore the quantitative relationship between extractant property and desulfurization or denitrogenation performance and explain the mechanism of this relationship, and to provide the scientific basis for the oriented design and development of the green extractant with novelty and high performance.

聚乙二醇（PEG）是一种绿色萃取剂，但其燃油脱硫脱氮性能不够理想。对脱硫而言，PEG端-OH导致分子间氢键的形成，掩盖Lewis碱位点，干扰脱硫。端基醚化可实现PEG的非质子化，消除分子间氢键，提升脱硫能力。然而，醚化PEG的极性不足，其S选择性不佳。对脱氮而言，PEG的Brønsted酸性弱，使其仅对非碱性氮有效，而对碱性氮的效果不佳。端基羧酸化可提高PEG的酸性，实现两类有机氮的同时脱除。然而，羧酸化PEG仍存在分子间氢键，干扰脱氮。针对脱硫，本项目将通过磺酰化、咪唑化来进一步改性醚化PEG（或PEG）,提高Lewis碱性和极性。针对脱氮，本项目将改性羧酸化PEG，使其形成低共熔溶剂，以弱化分子间氢键。本项目旨在设计上述功能化PEG的结构，调控活性基团分布，研究其性质分别与脱硫和脱氮性能之间的定量构效关系，并解释机理，为新型、高性能绿色萃取剂的定向设计与开发提供科学依据。

本项目完成了功能化聚乙二醇（PEGs）体系的结构设计及其萃取脱硫脱氮性能的研究。以脱硫脱氮性能为导向，对季铵化、氨基-酸化和添加剂改性等三类功能化萃取体系进行了深入研究。在萃取性能方面，季铵化聚乙二醇二羧酸（dcPEG）基萃取体系以低共熔溶剂的形式存在，显示出极好的萃取脱氮性能，不仅可同时脱除油中的碱性氮和中性氮，还保持了较高的N-选择性和油收率。聚醚胺-甲酸基萃取体系依靠所形成的酰胺基的Lewis碱性和可调控的Brønsted酸性，实现了噻吩硫、碱性氮和中性氮的同时脱除。PEGs-添加剂基萃取体系借助添加剂可调控的Lewis酸性，也展现出良好的萃取性能。上述萃取体系均显示出性能良好、成本可控、条件温和等特点，具有应用前景。进一步地，为实现非线性分布体系性能的量化描述，本项目开发出一种具有广泛适用性的新型等温模型。该模型基于理论推导，不仅形式简单，还可精准描述液-液平衡体系中溶质在两相间的平衡浓度分布。更重要的是，该模型中的参数（如平衡常数K和化学计量比n）具有明确的物理意义，能很好地反映萃取体系内部的相互作用机理，其平衡常数K（或吉布斯自由能变）可作为萃取性能的量化指标。该模型的提出不仅解决了传统活度系数模型（如NRTL、UNIQUAC等）所存在的形式复杂、参数缺乏物理意义等问题，还使得非线性分布体系性能的量化描述成为可能。基于上述研究结果，本项目还尝试了部分功能化萃取体系的结构-性能定量关系的建立。综上所述，本项目的研究工作兼具科学性和实用性，对相关研究具有一定的指导意义。