Coking- and sintering-resistant surface-mounted sub-nano cluster catalysts of endothermic cooling
EMSL Project ID
48745
Abstract
The ultimate objective of the proposed research is understanding and design of novel catalytic surfaces based on sub-nano surface-deposited clusters, with a particular application to dehydrogenation of hydrocarbons and carbon gasification for endothermic cooling of surfaces in extreme environments. The focus of this particular proposal is the design of such catalytic cluster-based interfaces stable against cluster sintering and coking, i.e. the two main means of deactivation. Surface deposited nano-clusters are very promising catalysts, because of the unique electronic structure effects in them, such as presence of corner and edge sites, dangling orbitals, separation of bands into MOs, and small HOMO-LUMO gaps. The aim of this work is to develop Pt-based clusters deposited on oxides, such as alumina, to catalyze selective dehydrogenation of hydrocarbons in fuels, and also to gasify coke. These processes are endothermic, and so they will provide endothermic cooling. There are two main ways through which such catalysts can deactivate: 1) cluster sintering on the support and forming large islands and films possessing no size-specific catalytic properties of interest, and 2) building up of coke on the surface of the catalyst, blocking the binding sites. Thus, the particular goal here is to understand and mitigate these deactivation pathways. Through the strategic choice of dopants for the clusters and the support, we will manipulate the electronic structure of these systems to achieve greater stability and longer life-times, by inhibiting both mechanisms of deactivation.
In order to approach catalyst design rationally and with a reasonable degree of predictability, it is critical to have a qualitative and quantitative understanding of chemical bonding on the material surface, along with their resultant structure and properties. This understanding is the key feature of the proposed theoretical research. Modeling will be done in a realistic way, mimicking the high T and p relevant to the experiment. For example, the process of cluster sintering will include the effect of temperature and surface-coverage. Not only migration is accelerated at elevated temperatures, but also clusters themselves stop occupying just a single global minima of the potential energy surface, and instead can be represented as an ensemble of thermally-accessible minima. For this mission, we have a wealth of in-house methods, complementary to traditional electronic structure techniques. The work also features a close collaboration with experimental groups that prepare, characterize, and test such cluster-based interfaces.
The deliverables of the proposed research include both the recipes for strategic doping to enhance the life-time of cluster-surface catalysts, and the fundamental understanding of such catalytic systems from the chemical bonding perspective, which will help future design. Understanding the mechanisms of existing catalysts and the design of new, active, catalysts are both among the grand challenges put forward by DOE, in the area of "Catalysis for Energy". This work falls within chemistry area of EMSL.
We request computer time at the EMSL Cascade machine to make this research possible.
Project Details
Project type
Exploratory Research
Start Date
2015-03-09
End Date
2015-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Related Publications
Baxter ET, MA Ha, AC Cass, H Zhai, AN Alexandrova, and SL Anderson. 2018. "Diborane Interactions with Pt7/Alumina: Preparation of Size-Controlled Borated Pt Model Catalysts." Journal of Physical Chemistry C 122(3):1631–1644. doi:10.1021/acs.jpcc.7b10423
Dadras MJ, L Shen, and AN Alexandrova. 2015. "Pt–Zn Clusters on Stoichiometric MgO(100) and TiO2(110): Dramatically Different Sintering Behavior." Journal of Physical Chemistry C 119(11):6047–6055. doi:10.1021/jp512277x
Ha MA, ET Baxter, AC Cass, SL Anderson, and AN Alexandrova. 2017. "Boron Switch for Selectivity of Catalytic Dehydrogenation on Size-Selected Pt Clusters on Al2O3." Journal of the American Chemical Society 139(33):11568–11575. doi:10.1021/jacs.7b05894