Ni-Al尖晶石的合成与还原制备Ni/Al2O3催化剂的过程机理及催化性能的研究

Ni/Al2O3 catalysts have been widely used in chemical industry. However, there are still some critical issues to be addressed, such as the sintering of Ni nanoparticles, carbon deposition, and the difficulty in regeneration of deactivated catalysts. Based on the chemistry principles of solid reaction between NiO and Al2O3 to produce highly stable spinel NiAl2O4, and reduction reaction of Ni species in NiAl2O4 at the high temperatures, this project will focus on the systematic investigation of the solid reaction and reduction reaction processes, in which, how NiO nanoparticles immerge into the Al2O3 to create surface NiAl2O4 and how Ni nanoparticles emerge from NiAl2O4 surface respectively. These will include the diffusion, reaction, immigration, and aggregation of NiO and Ni nanoparticles during the different processes, the change of interfacial NiAl2O4 spinel phase, and the interaction of Ni-supports. The structure-performance of NiO nanoparticles, Ni spinel, Ni nanoparticle, and their catalytic properties in both methanation (CO and CO2) and methane reforming with CO2 will be discussed to find the novel control strategy of re-dispersion of active Ni nanoparticles during reduction. In addition, the direct regeneration of deactivated Ni catalysts will be explored. Furthermore, the formation of Ni-Al multiple spinels on Al2O3 surface and the reduction of multiple metal species will be studied to understand their individual characteristics and general rules, as well as the synergistic effects, which will be helpful for developing new Ni composite catalysts. The successful implementation of this project will be significant not only in understanding the fundamental science of spinel-based catalysts but also in addressing some key issues occurred in industrial Ni catalysts.

工业Ni/Al2O3催化剂在高温反应时（甲烷化、甲烷干气重整等）常存在Ni颗粒烧结和再生困难等问题。本项目基于NiAl2O4尖晶石的高温合成及其中的Ni可还原的化学原理，系统研究NiO纳米颗粒进入Al2O3通过固相反应生成表层NiAl2O4,和Ni纳米颗粒从NiAl2O4表面还原溢出分散的过程机理，通过调控NiO和Ni的扩散、反应、迁移、聚并等过程，以及NiAl2O4相界面的演变和Ni-载体之间的相互作用，探索NiO-Ni尖晶石-Ni颗粒-催化性能的构效关系和Ni活性颗粒的还原溢出分散机制，探讨失活Ni催化剂的直接再生方法，研究含Ni-Al多元尖晶石在Al2O3表面的形成过程和不同金属组分还原过程的个性特征、共性规律及协同效应，开发含高稳定性和活性的Ni新型复合催化剂，对于探明尖晶石型催化剂的科学理论和解决工业Ni催化剂存在的问题具有重要意义。

Al2O3 负载的Ni 基催化剂凭借其良好的催化性能、相对低廉的价格，广泛应用于加氢、脱氢、烃类重整、甲烷化等化学工业中。然而，Ni/Al2O3 催化剂在高温反应时存在Ni 颗粒及载体的烧结、积碳、再生困难等问题。鉴于此，本项目主要进行了以下几方面的研究：（1）研究了NiO纳米颗粒进入Al2O3表面，并通过固相反应生成NiAl2O4，以及Ni 纳米颗粒从NiAl2O4表面还原溢出再分散的过程机制。在此基础上初步探讨了Ni-Fe、Ni-Co双金属进入Al2O3及其从相应的尖晶石结构中还原析出的过程机制。（2）基于上述固相反应—控制还原的策略，建立了失活Ni/Al2O3催化剂直接再生的新方法。研究发现，通过调控还原条件，可以使Ni纳米晶可控地从尖晶石矩阵中逐渐成核、析出，实现Ni颗粒的再分散；再生催化剂Ni与Al2O3载体间存在一层NiAlxOy中间相，Ni与NiAlxOy之间作用力很强，能够防止Ni颗粒的迁移、团聚。因此，再生后催化剂的活性和稳定性均高于新鲜催化剂。（3）通过剖析NiAl2O4相界面的变化规律和Ni-载体之间的相互作用，初步探明了NiAl2O4中间相的分布状态与Ni 催化剂的催化性能之间的构效关系，发现NiAl2O4中间相的存在能够提高催化剂的抗烧结及抗积碳性能，为高效Ni基催化剂的制备提供了一种新思路。基于前期研究的结果，我们设计合成了一系列含有NiAl2O4中间相的催化剂体系，研制出了高效、高稳定Ni基甲烷化催化剂。（4）尝试把尖晶石类化合物的固相反应过程应用到开发集成式反应器领域。采用刚玉管作为反应器进行了尝试，通过对反应管的前处理、浸渍Ni盐、固相反应和控制还原等步骤，制备出集成了Ni基催化剂的反应器，该反应器在CO甲烷化反应中表现出一定的活性。这种方法与传统的后涂敷法相比，可以显著增加催化剂与反应器壁面的结合力，具有良好应用前景。

内容获取失败，请点击重试