Unraveling the Active Site and Mechanism for C–S Bond Activation in Alumina-Supported Pt Catalysts: Ab Initio Insights into Catalytic Desulfurization

Abstract

Understanding the active sites of metal/oxide catalysts is of great significance in heterogeneous catalysis. In this work, we performed periodic density functional theory calculations to study the C–S bond activation of CH3SH on Pt/α-Al2O3 catalysts. Five different types of sites were investigated, which are single Pt-atom site in Pt1/α-Al2O3, Pt(111) site in Pt slab/α-Al2O3, and top-edge, interface, and atop-Al sites in Pt nanorod/α-Al2O3, respectively. In contrast to the common thought that lower-coordinated atoms at the surface of small metal nanoparticles (NPs) would lead to the higher reaction activity, the present work clearly demonstrates that the coordination-unsaturated sites over Pt NPs have subtle influence on the C–S bond scission. On the basis of energetic analysis, we propose that the interfacial Pt (type I) site, summarized as the “Pt–Al” dual perimeter site, could be the active site for the C–S bond activation. The presence of alumina support adversely impacts catalytic performance of Pt nanoparticle itself but exerts positive influence along the Pt/alumina interfacial boundary. The origin of this positive effect on the C–S bond activation over the “Pt–Al” dual perimeter site can be understood from the electronic perspective, in which the active interfacial Pt atoms act as electron acceptors (Ptδ−) while alumina support acts as electron donors. The electron-rich property of Ptδ− and the energy-level downshifting of the C–S antibonding orbitals of CH3SH both facilitate the electron transfer from Pt to the C–S antibonding orbitals, leading to subsequent C–S bond cleavage. The electron transferred from the support to Pt is the determining factor to activate the C–S bond of CH3SH and is dependent on the termination type of alumina. The present work provides geometric and electronic insights into the nature of active sites and sheds light on the design of more active metal/oxide catalysts toward catalytic desulfurization.

Enhancing Kinetics of Carbonyl Sulfide Hydrolysis Using Pt-Supported Al2O3 Catalysts: First-Principles-Informed Energetic Span Analysis

“…It can be seen that the scission of the C–S bond and hydrogenation steps are kinetically more favorable in the presence of Pt catalysts. This is consistent with previous computational studies that tell that Pt facilitates hydrogenation and various bond breakings including C–C and C–S bonds . Then, H 2 S* prefers to desorb before CO 2 *; nevertheless, their overall desorption energy is very high at 2.72 eV.…”

“…The energy profile of COS hydrolysis on Pt-Al 2 O 3 lies much lower in energy due to the strong COS adsorption on the Pt- This is consistent with previous computational studies that tell that Pt facilitates hydrogenation 64 and various bond breakings including C−C 66 and C−S bonds. 30 Then, H 2 S* prefers to desorb before CO 2 *; nevertheless, their overall desorption energy is very high at 2.72 eV. This is due to the formation of stable intermediates such as S* on the Pt site as also evidenced in experimental observation that S and C contaminate postreaction catalysts 65 indicating S poisoning.…”

“…Interestingly, our previous study found that Al 2 O 3 catalysts alone can offer 100% conversion of COS with better stability where it can withhold the conversion of 50% up to 7 h Adding transition metals, such as Ni, Au, Pd, and Pt, is expected to enhance the catalytic performance since these metals normally facilitate hydrogenation − and C–S bond breaking. − In particular, Pt has been recognized as one of the most efficient catalysts for selective hydrogenation, − , CO oxidation, and C–S bond activation . Such properties could hasten kinetics of COS hydrolysis.…”

Association between teachers’ outdoor smoking attitude and smoking initiation among in-school adolescents in Albania: A cross-sectional study

“…In general, social engagement with friends signi cantly in uences how adolescents behave; in fact, the usefulness of a particular activity rests on the behaviour of their friends [43]. A young person may receive access to cigarettes from a smoking acquaintance or feel pressured to start smoking [43,44]. This result is in line with many other studies on the relationship between smoking among adolescents in various school grade levels and peer smoking [22,45].…”

“…Relative to their colleagues, the odds of initiating smoking increased among in-school adolescents who have close friends who smoke. In general, social engagement with friends signi cantly in uences how adolescents behave; in fact, the usefulness of a particular activity rests on the behaviour of their friends [43]. A young person may receive access to cigarettes from a smoking acquaintance or feel pressured to start smoking [43,44].…”