Design of Promoted NiO Catalysts for Energy-Efficient Ethylene Production

Kajetan Leitner¹, Shuqiao Wang¹, and Alyssa J.R. Hensley¹*

1 Department of Chemical Engineering and Materials Science, Stevens Institute of Technology, Hoboken, NJ, U.S.A.

* Corresponding Author: ahensley@stevens.edu

Ethylene is an integral chemical within modern society. From its uses in plastics to its uses in food ripening, ethylene is present in some form in almost every industry and household. Because of this, the market is expected to reach a value of $247 billion by 2027. Despite this, little innovation has been made in the way of making production more efficient. Commercial production proceeds via industrial steam cracking, a very energy intensive and low efficiency process. However, catalysts such as nickel oxide have shown promise to increase the process efficiency and decrease energy consumption through Ethane Oxidative Dehydrogenation (EODH).

Here, we use density functional theory to analyze NiO catalysts promoted with various transition metals to determine their stability with and without defects in the surface and subsurface. We will use the NiO(110) facet as a representative of under-coordinated, highly active facets on the NiO catalysts. NiO(110) surfaces were promoted with 8 different transition metal promoters (Al, Nb, Mo, Sn, Ti, V, W, Zr). The effect of the promoter of the catalyst surface structure was determined by calculating the Gibbs free energies of formation as a function of temperature and gas phase composition. After determining the dominant surface structures for all systems, we analyzed the adsorption energies of several reaction critical EODH intermediates on the catalyst surface. Overall, we found that the addition of a metal promoter will increase the stability of the surface, and that a metal defect will be less stable than an oxygen defect. Furthermore, we have identified three critical surface sites that bind EODH reaction intermediates. Taken together, this work will be used in the future as a foundation for promoter specific testing and can be used to inform and accelerate experimental catalyst screening.