(669c) Selective Dehydrogenation of Ethanol to Acetaldehyde and Hydrogen on a Highly Diluted Nicu Alloy

The development of catalysts with a high dispersion of an active site for the production of targeted products selectively is a timely subject. Various highly diluted alloys or single atom catalysts have been reported to be highly active for a variety of catalytic reactions. For example atomically dispersed Au species supported on ZnZrO_x oxides can catalyze the dry ethanol dehydrogenation reaction.¹ PtCu single atom alloy catalysts exhibit high activity for several selective hydrogenation and dehydrogenation reactions.^2,3 Moreover, nanoporous Au materials modified with highly dispersed Ag species exhibit unique catalytic performance in the oxidative coupling of alcohols to esters.⁴

Here we report on the selective dehydrogenation of ethanol to acetaldehyde and hydrogen, an important industrial reaction to produce acetaldehyde which is an important commodity chemical, and also valuable hydrogen, using the single atom alloy strategy. Ni-containing Cu nanoparticles (NiCu NPs) and nanoporous Cu (np-NiCu) materials were found very active and selective for this reaction. Although monometallic Cu catalysts are also active, deactivation of Cu was observed. Adding a small amount of Ni to Cu forming NiCu highly diluted alloys dramatically increases the catalytic activity of copper. The kinetic studies show the apparent activation energy decreases from ~70 kJ/mol for Cu to ~45 kJ/mol for NiCu highly diluted alloys. Furthermore adding a small amount of Ni to Cu also significantly improves the stability of these catalysts, likely due to the stabilization of Cu against sintering. Our characterization data show that Ni is highly dispersed or even atomically dispersed on the Cu surface. Such highly dispersed Ni or isolated Ni atoms play a key role in the dehydrogenation of ethanol. This work opens a new route for the use of highly diluted alloys for alcohol dehydrogenation reactions. Furthermore the comparison of the catalytic performance of highly diluted alloy NPs with nanoporous materials is used to guide the design of the novel mesoporous catalyst architectures for selective dehydrogenation or oxidation reactions.

References

1. C. Wang, G. Garbarino, L. F. Allard, F. Wilson, G. Busca, M. Flytzani-Stephanopoulos, ACS Catal., 2016, 6, 210â??218.

2. F. Lucci, J. Liu, M. Marcinkowski, M. Yang, M. Flytzani-Stephanopoulos, C. E. H. Sykes, Nat. Commun.6, 8550 (2015).

3. J. Shan, F. R. Lucci, J. Liu, M. El-Soda, M. D. Marcinkowski, L. F. Allard, C. E. H. Sykes, M. Flytzani-Stephanopoulos, Surface Science(2016), DOE: 10.1016/j.susc.2016.02.010.

4. Branko Zugic, Stavros Karakalos, Kara J. Stowers, Monika M. Biener, Juergen Biener, Robert J. Madix, and Cynthia M. Friend, ACS Catal., 2016, 6, 1833â??1839.