过渡金属磷化物双功能助剂修饰卤氧化铋选择性光催化氧化柴油深度脱硫

Heterogeneous photocatalytic oxidative desulfurization is a novel and environmental friendly technology for deep desulfurization of diesel fuel, but the bottleneck in present lies in the low selectivity of desulfurization process, which leads to the oxidation of unsaturated hydrocarbons and reduction of diesel fuel quality. In this project, in order to improve the selectivity of desulfurization reaction, two-dimensional bismuth oxyhelide (BimOnXp, X = Cl, Br, I) is chosen as main photocatalyst, and its redox potentials can be controlled by the stoichiometric ratio change. Then the surface oxygen vacancies (SOVs) will be introduced to improve the molecular oxygen activation ability, and the transition metal phosphides (TMPs) work as bifunctional co-catalysts to promote the selective chemical adsorption of organic sulfides and increase the separation efficiency of photogenerated charge carriers. Thus, TMPs/BimOnXp-SOVs composite photocatalysts are constructed and applied to the visible-light-driving diesel desulfurization with high selectivity and activity. Meanwhile, in order to obtain the photocatalytic desulfurization mechanism, the separation and transfer process of photogenerated electron-hole pairs as well as substance changes during the chemisorption and surface-catalytic reaction will be investigated by systematic characterizations, including photoelectrochemical measurements, surface photovoltaic technology, theoretical calculation and GC-MS, etc. The selective enhancement mechanism will be elucidated by revealing the relationship between composition, microstructures and catalytic selectivity performance. The research results of this project will provide scientific basis and experimental support for the application of photocatalytic oxidation desulfurization technology in clean fuel production.

多相光催化氧化是一种新兴绿色的柴油深度脱硫技术，目前的瓶颈问题在于脱硫过程选择性较低造成柴油中不饱和烃发生氧化，导致燃油品质降低。本项目以提高脱硫反应选择性为核心，以二维卤氧化铋（BimOnXp,X=Cl,Br,I）为主催化剂，通过改变组分化学计量比对催化剂氧化还原电势进行控制，结合表面氧空位（SOVs）修饰促进分子氧活化，借助过渡金属磷化物（TMPs）双功能助剂负载促进有机硫化物的选择性化学吸附和活化，增强光生载流子分离效率，构筑TMPs/BimOnXp-SOVs复合光催化材料，实现可见光激发下高选择性、高活性催化氧化柴油深度脱硫。利用光电化学测试、表面光电压技术、理论计算和GC-MS等手段，获得光生电荷分离、迁移规律和吸附-表面催化反应物质变化过程，揭示催化剂组成、结构与脱硫选择性之间的构效关系和增强机制，阐明其选择性催化反应机理，为光催化氧化脱硫技术的实际应用提供科学依据和实验支持。

多相光催化氧化是一种绿色低耗的燃油深度脱硫技术，但存在催化剂载流子分离效率低、分子氧活化能力不足、脱硫过程选择性差等瓶颈问题。对此，本项目围绕卤氧化铋、钨酸铋和氮化碳等催化氧化材料，建立了催化剂组分调控与掺杂工程、极化电场强化、双功能助剂修饰、表面缺陷改性、异质结构建等性能优化策略，协同促进催化反应过程中光吸收、光生电荷定向分离、反应物分子吸附和活化效率，显著提升材料光催化氧化活性，并且明晰了其光催化活性和组成结构之间的“构效关系”。研究结果表明，控制材料合成条件可制备得到富铋型Bi24O31ClxBr10–x固溶体催化剂，通过卤素类型和比例调控可增加晶体结构单元的不对称性，调节[Bi24O31]和[X]层之间的电势差，增强卤氧化铋催化剂的极化内电场强度，促进体相电荷分离和转移效率；同时利用过渡金属磷化物和表面氧空位修饰，构筑NiCoP/Bi4O5Br2和Ni2P/Bi3O4Br-OVs双功能异质结体系，可通过S型界面电荷转移机制提高光生载流子的分离和传输效率，并为分子氧吸附和活化提供高效的双活性位点，加强分子氧活化效率和氧化活性物种浓度。为强化催化剂与芳香杂环噻吩硫化物的吸附及亲和能力，项目组筛选非金属有机聚合物氮化碳材料，利用共热解法实现其分子裁剪效应，制备得到超薄多孔的N3C缺陷型氮化碳催化剂；其大量微孔结构和不饱和N–C=N活性位点，可有效加强芳香杂环噻吩硫化物在催化剂表面的吸附传质效率，并促进对分子氧的吸附和活化效率，表现出优异的模拟汽油和柴油脱硫活性，可在光照1h后实现99.5%的脱硫效率，使硫含量从500 ppm降低至2.1 ppm，并表现出良好的选择性。此外，项目还揭示了Bi2WO6和ZnIn2S4等非对称层状材料的极化电场效应，并建立了表面缺陷和异质结界面调控等极化电场强化策略。项目的开展对于开发高效光催化有氧氧化催化剂和极化催化剂，推进光催化氧化燃油深度脱硫技术的实际应用具有重要意义。