利用Pt/BiOX太阳能光催化废油脂脱羧及其反应特性研究

It has important scientific significance and practical value for converting Waste oils and fats (WOF), mainly constituted by Triglycerides and Free fatty acids, into the hydrocarbons via a decarboxylation process, into the hydrocarbons, which does not only reduce the environment pollution, but also facilitate the resource utilization of WOF. In this project, the clean solar photocatalytic oxidation technology will be introduced into the green recycling use process of WOF. Firstly, combined with the complexity of WOF decarboxylation reaction and the controllability of photocatalytic reaction, it is expected to construct the highly efficient sunlight responding Pt/BiOX photocatalytic systems via the charge transfer effect between atom Pt and micro-nano BiOX, achieving the effective transfer of photo-induced electrons and the high oxidizability of photo-induced holes. Secondly, the intrinsic connections between the the reaction medium, reaction temperature, reaction time, catalyst dosage and the decarboxylation behaviors over Pt/BiOX photocatalysts, the transfer-paths of photo-induced electrons, the analysis of reaction products at the different oxidation time, and the reaction-paths in the WOF decarboxylation process using the 18O or 13C isotope tracing measures, should be laid great emphasis. Moreover, the correlative thermodynamic properties of the decarboxylation intermediates, transition states and activation energies for WOF to hydrocarbons will be analyzed and discussed using the first-principle calculations. Finally, to build up the mutual feedback mechanisms among theory-experiment-characterization aspects, to clarify the key active species and their action mechanisms in the WOF decarboxylation reaction, and to master the behavioral parameters of the decarboxylation process for WOF to hydrocarbons, which will provide the scientific methods and basic data for the resource utilization of WOF.

废油脂主要成分为甘油三酯和脂肪酸，将其氧化脱羧转化为烃类物质以减少对环境的污染，同时实现资源化利用，具有重要的科学意义和实用价值。本课题将洁净太阳能光催化氧化技术引入废油脂的绿色处理再利用中，针对废油脂脱羧反应的复杂性及光催化反应的可控性，构筑高效太阳光响应的载Pt卤氧铋光催化体系，利用原子Pt与微纳结构BiOX之间的传荷作用，实现电子的有效传递和空穴的高效氧化；重点研究Pt/BiOX体系光催化反应介质、气氛、时间、温度、催化剂用量等与脱羧进程的内在关联，探究光生电子的转移路径，分析检测不同氧化时段产物组成，并采用18O或13C同位素标记追踪其氧化脱羧反应途径；同时结合第一性原理从分子层面获取废油脂脱羧中间体、过渡态及产物等热力学信息，建立理论-实验-表征相互反馈机制，澄清废油脂光催化脱羧的关键活性物种及其作用机制，掌控脱羧转化烃类物质的行为参数，为废油脂资源化利用提供科学方法和基础数据。

将洁净太阳能光催化氧化技术引入废油脂氧化脱羧转化为其他有用物质，既减少对环境的污染又实现其绿色处理和资源化再利用，具有重要的科学意义和实用价值。本项目执行期间，首先，构建了BiOCl、BiOBr、BiOBr1-xClx、Bi12O17Br2、Bi4O5Br2、Pt/BiOBr、Pd/BiOBr、Ag@AgCl/ZIF-8、Ag@AgCl/h-WO3、Ag@AgCl/Ag纳米膜/ZIF-8、BiOBr/NiO@ACSs等系列光催化体系，提出其简易温和的催化剂制备技术，合理地调控了BiOX导带光生电子的转移，实现了光生电子-空穴的有效分离，增强其光催化性能。其次，结合理论计算分析了BiOX体相-表界面的光生载流子迁移机制和微观结构性质，掌握其光生载流子在体相及表面的激发传输路径，明确其关键活性物种，为寻找脱羧反应的活性位点提供相应的数据。第三，建立酸催化油酸单甘酯的酯基转换反应模型与路径，提出了油酸单甘酯结构裂解脱去一个甘油分子（速控步骤）并最终脱氢生成目标产物游离脂肪酸甲酯(FAME)的反应机制；活性物种•OH作用于硬脂酸甲酯生成中间体碳酸氢甲酯（HO–(C=O)–OCH3，MHC），证实MHC脱羧过程为控速步骤；我们首次发现光催化油酸在无氧气氛下可发生异构化反应，其过程中存在自由基阳离子中间体，提出光诱导h+作用机理，为油酸的深入研究奠定良好的基础数据。最后，光热催化处理废油脂得到的混合产物可应用于煤泥浮选领域，并取得良好的社会经济效益。