高汇聚光-热协同甲烷重整体系构建及机理研究

Highly concentrated solar energy can be potentially utilized for CO2 dry reforming of CH4 (DMR) to produce synthetic gas, thus to achieve the upgradation, conversion, storage and transport of solar energy as well as carbon cycle for reducing CO2 emission. To this end, this project proposes to design and fabricate highly efficient and stable photo-thermal-catalyst materials with broad absorption to sunlight full spectrum energy. Porous metal medium will be employed to support the novel catalysts which will be incorporated intoaheat plate coupled heat pipe coupled phase-transition heat absorber proposed by the project team previously. The resulted thermochemically coupled phase change reactor is expected to be of a high photo-thermal conversion efficiency and a low risk of thermal distortion. The key factor of the integrated DMR lies in the rational design of the multifunctional catalysts. In the project, through advanced nanostructure design, thermally stable photocatalysts of TiO2 (rutile), WO3 and Bi2WO6 will be coupled with Ni-based conventional thermal catalysts in methane reforming. Moreover, Mg or Al porous medium will be introduced for supporting the catalysts to obtain the engineered photo-thermal-catalyst materials. Mechanistic investigations will be conducted to elucidate the synergistic effect of thermal and photocatalytic catalysis in CO2 dry reforming for CH4. The stability and evolution of microstructure of the supported catalysts under extremely intensive and uneven irradiations as well as the improvement strategy will be studied. Kinetic studies unveiling the mass and heat transfer in the DMR processes under extremely intensive and uneven irradiations and intricate boundary conditions will be also carried out. This project will bring out break-through enhanced catalysis that can never be achieved on single photocatalytic or thermal catalytic process, with illustrating the integrated photo-thermal-catalysis mechanism to pave the foundation for efficient absorption and utilization of highly concentrated, full-spectrum solar energy.

将高汇聚的太阳能用于甲烷-二氧化碳干重整（DMR）体系，制备合成气，实现太阳能的提质、改性和储运，并达到碳资源的循环。提出制备太阳能全谱吸收的DMR光热协同催化剂；将其装载于泡沫金属中，并和项目组开发的热板-热管耦合相变吸热器集成为耦合相变反应器，提高DMR能量转换效率，并降低吸收体和反应器热破坏风险。重点是从高温稳定的光催化剂（如TiO2，WO3和Bi2WO6）出发，通过纳米结构设计，以高效的甲烷重整热催化剂Ni等修饰，选择适当Mg和Al载体，制备多功能、高温稳定的光热催化DMR材料。研究高汇聚条件下DMR光热协同催化机理，分析催化反应历程。探索极强非均匀辐照条件下复合催化材料的微结构演变规律及其抑制措施。阐明极强非均匀辐照和复杂热边界条件下，多效DMR吸收体耦合热质传递的反应规律。本项目将突破传统单效光或热催化的效率障碍，揭示光热协同催化机制，为高汇聚条件下太阳能全谱吸收提供新思路。

光热协同催化对于提高DRM的效率，降低其反应温度具有重要意义，设计新型催化剂、探索反应机理及开发配套的催化反应器是其研究热点。.分别以限域双浸渍法和顺序吸附法制备Ni-Ir/SiO2双金属催化剂，通过限域及调控材料微结构，使其具有较小的粒径和更好的均匀性，比较发现限域双浸渍法工序短，效果较好，更有潜在的价值。光热干重整评价表明，Ni-Ir/SiO2金属粒径小于3.5nm且分布均匀；在700℃和5W/cm2光照条件下，H2产率达861 mmol/g/h，和贵金属主导催化剂相当；双金属的局域表面等离子体共振(LSPR)效应，调控增强对近紫外和可见光的吸收，强化光热协同效应，促进CH4与CO2分子活化；特别有利于甲烷在低于热力学平衡温度下解离，500~700℃下，甲烷转化率仍线性增加，致使H2和CO产率近乎指数级提高；该光热催化DRM反应具有较好的可重复性。.利用VIII族具有LSPR效应的非贵金属Co代替贵金属Ir，制备双金属催化剂Ni-Co/SiO2，较全面地评估光热催化DRM性能和机理。发现，1.2Ni-0.3Co的H2产率最高达到1300mmol/g/h，量子效率达到67%，该值比文献报道的贵金属Pt/TiO2高，充分体现该工作中双金属催化剂构建的优势。量子产率在不同波长下变化趋势与UV-Vis光谱保持一致；有限元分析揭示双金属的构建增强电场强度进而改善反应性能，直接证明其LSPR效应是反应性能提高的主要原因。.将上述材料与泡沫金属集成，制备整体式复合光热吸收体，发现其表现出类似基体的光热协同作用；得到了表征传质的雷诺数、施密特数与舍伍德数的关联式，其热质传递效果明显优于传统颗粒型催化剂。.为了实现光热全谱吸收性能，设计了一种双层泡沫金属梯度太阳能中高温集热器，初步模拟获得反应器内温度场、压力场和速度场分布，探索了泡沫金属孔隙率等结构参数对热质传递特性的影响。