摘要
The interplay between analytical technique and industrial practice has been central in the development of catalytic materials for processing petroleum. This article presents reviews of key aspects of two of the most important classes of catalytic materials: noble-metal Pt nanoparticles (NPs) on alumina, which are the basis of catalytic reforming;and layered sulfides of Mo and W, which catalyze hydrogenation and hetero-atom removal in hydroprocessing. The state of understanding of Pt cluster growth and resulting structures, as developed using X-ray absorption spectroscopy and STEM, is reviewed. Influences of both Pt reduction temperature in hydrogen gas, and oxidizing pretreatment conditions prior to Pt reduction, are considered. Recent work by the present authors on Pt NP structure evolution is presented in the context of the previous work. A review is subsequently presented of layered sulfide based NPs, summarizing contributions from a range of analytical techniques. Work on active site structures of sulfide NPs is reviewed, focusing particularly on the critical interactions of active edge sites with sulfur and hydrogen in chemisorption, physisorption, and spillover interactions. New temperature programmed reduction (TPR) results are presented for supported and unsupported sulfide NPs. Structural changes in TPR of alumina-supported MoS2 are investigated using extended X-ray absorption fine structure and density functional theory modeling, and are determined to arise from removal of identifiable edge-site sulfur species.
分析表征与工业应用技术之间的相互影响对开发石油加工的催化材料一直起着至关重要的作用.本文着重介绍石油化工中两类最重要的催化材料:(1)催化重整工艺中广泛使用的负载于氧化铝上的铂纳米颗粒;(2)加氢处理工艺中用于加氢和去除杂原子的含钼和钨的层状硫化物.首先,我们综述了用扩展X射线吸收精细结构(EXAFS)和扫描透射电子显微镜研究铂团簇生长和结构的最新研究动态.详细讨论了氧化预处理条件以及氢气环境中的还原温度对铂纳米粒子形态的影响,并结合最近的实验结果进一步延伸对铂纳米颗粒结构演变的理解.随后,本文总结了一系列分析表征技术对层状硫化物纳米颗粒研究的贡献,综述了硫化物纳米粒子活性中心结构的研究进展,重点介绍了边缘活性中心与硫和氢之间的互动在化学吸附、物理吸附及溢流效应中的关键作用.本文也对负载及非负载型的硫化物纳米粒子最新程序升温还原实验结果进行了探讨.氧化铝负载的硫化钼颗粒在程序升温还原过程中的结构变化可以通过EXAFS实验和密度泛函理论模拟来解释.研究表明,可识别的硫化物边缘活性中心上硫原子的去除是导致这一类结构变化的主要原因.
基金
the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357
