A DFT Study and Microkinetic Simulation of Propylene Partial Oxidation on CuO (111) and CuO (100) Surfaces

• Published in: Journal of physical chemistry. C Vol. 120; no. 48; pp. 27430 - 27442
• Main Authors: Song, Yang-Yang, Wang, Gui-Chang
• Format: Journal Article
• Language: English
• Published: American Chemical Society 08.12.2016
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.6b09621

Catalytic reaction of propylene partial oxidation by copper oxide has been considered as an environmentally friendly route, and the selective oxidation of propylene to acrolein and propylene oxide is of significance. Herein, the catalytic mechanism of metallic oxide CuO (111) and CuO (100) catalysts for propylene partial oxidation has been investigated by us via density functional theory calculations with a Hubbard U correction; concomitant microkinetic simulations are carried out to discuss the catalytic activity. We have reported two parallel reaction pathways on both surfaces in detail: dehydrogenation and epoxidation. The transition states and energy profiles are calculated for the formation of intermediates as well as products. On the two surfaces, acrolein is obtained by two H-stripping reactions in the dehydrogenation process. Furthermore, in the epoxidation reaction, propylene oxide and propanal can be created through one propylene oxametallacycle intermediate, competing with the pathway that propylene oxide and acetone can be produced through the other propylene oxametallacycle intermediate. In our calculation, it is found that the activation barriers of propanal and acetone generated from different intermediates on (111) surface are too high, and acrolein is the main product. Besides, energy barriers for the identical reaction pathway on (100) facet are lower than those on (111) facet; microkinetic simulations also show that the turnover frequency of acrolein at the same temperature on (100) surface is larger than that on (111) surface. Moreover, it is found that not only acroline can be formed on (100) facet but also propylene oxide can be formed, which is different from the case of (111) facet where acroline is the only product. All of these results indicate that the catalytic activity on (100) surface is higher toward propylene partial oxidation than that of (111) surface. The reason why (100) facet is more active than (111) has been analyzed by the density of state calculation, and it is also found that the states of the d orbitals of Cu atoms in (100) facet are closer to the Fermi level compared to those of the Cu site in (111) facet.