Identification of multiple steps in the dehydrogenation of cyclic C6 hydrocarbons to benzene on platinum(111)

Dehydrogenation of Cyclohexene on Platinum Nanoclusters on a Thin Film of Al2O3/NiAl(100)

“…4(b), implying the co-existence of various hydrocarbon species. The continuous change implies a continuous process, in contrast with earlier observations on Pt single crystals [1][2][3][4][5] but consistent with a mechanism of dehydrogenation proposed on the basis of thermochemical calculations for cyclohexene on a Pt(111) surface [6]. There, adsorbed cyclohexene loses H atoms stepwise to form a cycloallylic species (c-C 6 H 9 ), cyclohexadiene (c-C 6 H 8 ), cyclohexadienyl (c-C 6 H 7 ) and then benzene (C 6 H 6 ).…”

“…There, adsorbed cyclohexene loses H atoms stepwise to form a cycloallylic species (c-C 6 H 9 ), cyclohexadiene (c-C 6 H 8 ), cyclohexadienyl (c-C 6 H 7 ) and then benzene (C 6 H 6 ). The dehydrogenation notably begins at 150 K, much lower than the temperature for a single-crystal surface [1][2][3][4][5][6][7][8][9][10][11]. The dissociation of benzene, evident through the shift of the C 1s signal to the elemental carbon position about 284.5-285 eV, occurs between 300 and 400 K, also a lower temperature than expected for Pt single crystals [9].…”

“…Because of the relevance to petroleum processing [1][2][3][4][5][6][7][8][9][10][11], the dehydrogenation of cyclic hydrocarbons such as cyclohexane (C 6 H 12 ) and cyclohexene (C 6 H 10 ) over singlecrystal Pt(100) and Pt(111) surfaces has been extensively investigated with various techniques. Cyclohexene, a possible intermediate in the dehydrogenation of cyclohexane into benzene, can be hydrogenated to cyclohexane or dehydrogenated to benzene (C 6 H 6 ).…”

Molecular surface science of C–H bond activation and polymerization catalysis

“…Cyclohexene adsorption under UHV conditions has been extensively studied on the Pt(111) and Pt(100) surfaces using thermal desorption spectroscopy (TDS) [23][24][25], reflection adsorption infrared spectroscopy (RAIRS) [23], electron energy loss spectroscopy (EELS) [23], bismuth post dosing TDS (BPTDS) [5,25], laser-induced thermal desorption (LITD) [24], high-resolution electron energy loss spectroscopy (HREELS) [23,24], and SFG [26][27][28][29][30][31]. Briefly, cyclohexene exists in a di-r form on the Pt(100) and Pt(111) surfaces at 100 K. Di-r cyclohexene is transformed to p-allyl c-C 6 H 9 as the surface temperature is increased to 200 K. Dehydrogenation and benzene desorption results from further increasing the surface temperature [23].…”

“…Briefly, cyclohexene exists in a di-r form on the Pt(100) and Pt(111) surfaces at 100 K. Di-r cyclohexene is transformed to p-allyl c-C 6 H 9 as the surface temperature is increased to 200 K. Dehydrogenation and benzene desorption results from further increasing the surface temperature [23]. Decomposition of benzene occurs at temperatures above 300 K [5,24,32]. It is important to note that the surface species present at low temperatures in UHV environments may not necessarily be the same as those species that are adsorbed under catalytically relevant conditions found at high pressures/temperatures or in the presence of excess hydrogen.…”