DFT approach study of the hydrogenation of Ni- and V- octaethylporphyrins catalyzed by MoS2 promoted with Fe, Co or Ni

Abstract

The effect of promoting the catalytic surface of MoS₂ with Fe, Co and Ni, utilized in the hydrodemetallization reactions of heavy oil fractions, was investigated using the model porphyrins VO-octaethylporphyrinate and Ni-octaethylporphyrinate. Density Functional Theory was employed to simulate a representative chemical environment with two hydrogen molecules. For this purpose, a catalytically active site was defined. The results indicated that porphyrins exhibited the strongest chemisorption in the molybdenum-exposed region, followed by the sulfur-exposed region. Furthermore, the initial hydrogenation was favored on the Co- and Fe-promoted catalytic surfaces with both porphyrins. Similarly, the Co- and Fe-promoted surfaces interacting with Ni-OEP demonstrated strong chemisorption of a second H₂ molecule, whereas for VO-OEP, the second H₂ molecule exhibited favorable chemisorption with the Fe-promoted catalytic surface. These findings suggest that two H₂ molecules are necessary to weaken the macrocyclic bonds of the porphyrins.