离子液体催化异丁烯二聚纳微反应器的构筑及调控机制

The content of methyl tert-butyl ether, a blending component with high octane number for gasoline, will be strictly restricted. The development of indirect alkylation process, i.e., dimerization of isobutene followed by hydrogenation to produce isooctane, could relieve the double pressure of the decreasing utilization of isobutene and the increasing demand for improvement of gasoline quality. However, the oligomerization of isobutene needs long reaction time and composition of the product is difficult to control. Considering the efficient catalytic activity of ionic liquids and the advantage of Pickering emulsions in intensifying chemical reactions, functional ionic liquids will be designed to catalyze isobutene dimerization, and Pickering emulsions, i.e., ionic liquid-based microreactors, stabilized by modified SiO2 particles will be constructed to improve mass transfer of this liquid/liquid reaction system, to significantly decrease the reaction time, to inhibit occurrence of side reactions, and to intensify isobutene dimerization. The wettability and emulsifying properties of SiO2 will be modified by grafting with various functional groups to change the property of the Pickering emulsions, and regulation mechanism of the microreactor will be clarified. The catalytic activity of isobutene dimerization in the ionic liquid-based microreactors will be investigated, and essential relationship between the catalytic activity and the emulsion property will be revealed. Moreover, the microscopic reaction mechanism of the intensification of isobutene dimerization in this system will be explored. This research will provide scientific basis for the technology development of ionic liquid-based microreactor intensified isobutene dimerization for alkylate oil production.

作为汽油高辛烷值调和组分的甲基叔丁基醚含量将严格受限，开发异丁烯二聚、加氢制异辛烷的间接烷基化技术可缓解异丁烯利用率下降及油品质量持续升级的双重压力。针对异丁烯聚合反应耗时长、产物组成不可控等问题，结合离子液体的优异催化性能及Pickering乳液在强化反应方面的优势，本项目拟设计功能化离子液体催化剂，并借助改性SiO2构筑Pickering乳液，形成离子液体纳微反应器，改善该液/液反应体系传质，大幅度缩短反应时间，抑制高聚、裂解等副反应发生，强化二聚反应的进行。通过在SiO2表面接枝不同官能团改变其浸润性及乳化性质，进而调控Pickering乳液性质，阐明乳液调控机制。探究纳微反应器中异丁烯二聚反应活性，获得反应性能与乳液性质的内在本质关系，并揭示该体系强化异丁烯二聚的微观反应机理，为离子液体纳微反应器催化异丁烯二聚合成烷基化油的技术开发提供科学基础。

丁烯是石油裂化过程的副产品，目前资源化利用率低。丁烯二聚随后加氢制异辛烷是生产烷基化油、实现其高值利用的有效途径，而丁烯齐聚程度与产品品质密切相关，催化剂的设计是实现丁烯可控齐聚的关键。针对传统催化剂易失活、难再生、产物组成不可控等问题，结合离子液体结构可设计及优异催化性能，本项目设计了系列功能化离子液体催化剂，包括非金属酸性离子液体、B-L双酸性离子液体，系统研究了离子液体酸性质及调控规律，发现L酸的引入可增强B酸强度。评价了离子液体在异丁烯齐聚反应中的催化性能，获得催化剂结构/酸性与催化性能的关系，高斯计算结果表明，当离子液体与异丁烯的结合能适宜时，离子液体具有优异的催化性能，太强或太弱的相互作用将抑制反应的进行。此外，离子液体催化丁烯齐聚为典型液-液反应，主要发生在相界面，反应受传质影响。基于乳液（微乳液、Pickering乳液）在强化液-液反应方面的优势，本研究分别以长烷基链离子液体、改性SiO2颗粒为乳化剂，构筑了微乳液、Pickering乳液，形成离子液体纳微反应器，阐明了纳微反应器性质调控规律及机制。具有更好两亲性、成乳能力优异的离子液体乳化剂，可与离子液体催化剂及异丁烯形成稳定微乳液，强化体系传质，提高二聚产物选择性，解决了反应物转化率和二聚产物选择性难以兼顾的难题。磺酸基、长烷基链共改性的SiO2颗粒具有较好耐酸性，可与酸性离子液体催化体系及反应物形成稳定Pickering乳液，通过改变催化剂结构及酸性、乳化剂结构及用量，可调控异丁烯齐聚反应的产物分布，实现定向调控。采用本研究所开发体系，可实现异丁烯的完全转化，二聚产物选择性最高为95.1%。该研究为烯烃资源的高值化利用提供了有效途径，为提高非均相反应体系的传质提供了有益借鉴和理论支撑。