核壳型Ni基催化剂催化CO2和甲烷制合成气构效关系和反应机理研究

Carbon dioxide reforming of methane to synthesis gas has become an attractive route due to its conforming to the sustainable development of energy and environment. Core-shell structured Ni-based catalyst with different Ni partical size will be synthesized in a controllable way by modulating physical and chemical conditions of catalyst preparation such as temperature, pressure and properties of solute. The structure-performance relationship between catalyst core-shell structure and its catalytic activity will be uncoverd. Based on the results of in-situ IR study, the adsorption form of CO2 and CH4 adsorbed on the surface of catalysts, the intermediate product, the way of and CH4 participation in the reaction and the reation mechanism of dry reforming reaction will be confirmed. Combined the results of DFT quantum computation, the adsorption form of reactant, intermediate product and reaction product on the catalyst surface can be explored. Furthermore, the rate-controlling step can be cleared by comparing the activation energy of each reaction steps with trasition state search.

CO2和甲烷重整制合成气符合能源和环境可持续发展战略，是一条很有吸引力的工艺路线。通过调变催化剂制备的物理、化学条件（如温度、压力和溶液的性质等），可控合成具有不同粒径大小的核壳型Ni基催化剂，揭示催化剂核壳结构与催化性能间的构效关系。通过原位红外动态行为研究，确定CO2和甲烷在催化剂表面的吸附活化方式、反应生成的中间体物种及反应方式，明确CO2和甲烷反应制合成气的反应机理。结合DFT量化计算，考察反应物、中间产物和产物物种在催化剂表面的吸附情况，进行过渡态搜索，比较各步反应活化能大小，确定反应速率控制步骤。

CO2和甲烷重整制合成气符合能源和环境可持续发展战略，是一条很有吸引力的工艺路线。通过调变催化剂制备的物理、化学条件，实现了核壳型Ni基催化剂的可控合成。通过水热晶化-Stoöber法，合成了NiCeOx@SiO2催化剂；通过采用水包油的微乳体系，一步法制备出了具有Yolk-shell结构的Ni@HSS催化剂；进而通过无溶剂晶化得到具有分子筛包覆结构的Ni@S2催化剂。研究了不同核壳型Ni基催化剂催化CO2和甲烷反应制合成气反应性能，揭示了催化剂核壳结构与催化性能间的构效关系。核壳结构的限域效应、活性中心与载体间的强相互作用以及富含氧空穴的氧化铈的消碳作用提高了催化剂的活性及稳定性。通过原位漫发射红外光谱（DRIFTS）和密度泛函理论（DFT）计算对NiO-MgO催化剂在甲烷-二氧化碳干重整反应中的机理，尤其是CO2活化形式进行研究。结果表明，对于产物CO的形成，气相CO2与CH4裂解产物C直接反应生成CO，即Eley-Rideal（E-R）型机理，是主要的反应路径。同时，另一反应路径是，单齿型碳酸盐作为MgO表面活性吸附态CO2物种，与CH4在活性组分Ni表面裂解产生并溢流到载体表面的解离H发生氢解作用形成产物CO。