Benzene formation from acetylene on Pd(111): a high-resolution electron energy loss spectroscopy study

Jungwirthová, I.; Kesmodel, L. L.

doi:10.1016/s0039-6028(00)00842-6

Cited by 12 publications

(12 citation statements)

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“…However, due to the complexity of these spectra, the clear extraction of benzene requires more detailed analysis. 13 A strong feature at approximately 1800 cm -1 is due to carbon monoxide impurity. It appears at a frequency of 1750 cm -1 in the spectrum taken at 120 K. Since collecting the spectra for one temperature in specular and off-specular directions takes several hours, the exposure of CO from the residual atmosphere is not negligible.…”

Section: Resultsmentioning

confidence: 99%

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Thermal Evolution of Acetylene Overlayers on Pd(111)

Jungwirthová

Kesmodel

2000

J. Phys. Chem. B

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The thermal evolution of acetylene adsorbed on the (111) surface of palladium has been studied by high resolution electron energy loss spectroscopy (HREELS). This study encompasses the temperature range 120-800 K for acetylene exposures of 0.25-3.5 langmuirs and includes HREELS data for both specular and off-specular scattering. The spectra are interpreted in terms of acetylene evolution to ethylidyne via a vinylidene intermediate, with the additional hydrogen supplied by the residual gas. Evidence for benzene formation is also seen in the appearance of the benzene ν 4 (720 cm -1 ) band. Subsequent heating to 400 K results in dehydrogenation of ethylidyne to CCH species. A spectral normalization method is employed to compare intensities of vibrational bands as a function of temperature and proves useful in analysis of the temperature dependence of the surface species. We find that 0.25-langmuir exposure results in an essentially pure ethylidyne layer whereas higher coverages eventually result in lower ethylidyne production, likely due to steric hindrances on the vinylidene intermediate and the competing channel of benzene production.

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Section: Resultsmentioning

confidence: 99%

“…24 A more detailed study of benzene formation will be presented elsewhere. 13 As explained in the following paragraph we surmise that the 1100 cm -1 loss below 233 K is associated with a vinylidene in-plane CH 2 bend (or rocking mode).…”

Section: Origin Of Reaction Intermediate At 213 Kmentioning

confidence: 86%

Thermal Evolution of Acetylene Overlayers on Pd(111)

Jungwirthová

Kesmodel

2000

J. Phys. Chem. B

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“…This conversion mechanism (known as cyclo-trimerization) has mostly been explored on pure and mixed Pd catalysts (e.g. Jungwirthova and Kesmodel (2000) and Ramirez-Cuesta et al (1995)). In this case, cyclo-trimerization seems to occur through the rapid formation of the C4H4 metallocyclic intermediate species (Ormerod et al, 1993a;Pacchioni and Lambert, 1994;Ramirez-Cuesta et al, 1995).…”

Section: Titanmentioning

confidence: 99%

“…Second, cyclo-trimerization studies of C2H2 at low temperatures on metal surfaces have identified benzene as the C6H6 product through ultraviolet photoelectron spectroscopy (Sesselmann et al, 1983;Tysoe et al, 1983) and high-resolution electron energy loss spectroscopy (Jungwirthova and Kesmodel, 2000).…”

Section: Thrower Et Al (2009) It Is Unlikely That Other C6h6 Isomermentioning

confidence: 99%

Uptake of acetylene on cosmic dust and production of benzene in Titan's atmosphere

Frankland

James

Carrillo‐Sánchez

et al. 2016

Icarus

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A low-temperature flow tube and ultra-high vacuum apparatus were used to explore the uptake and heterogeneous chemistry of acetylene (C2H2) on cosmic dust analogues over the temperature range encountered T below 600 km. The uptake coefficient, , was measured at 181 K to be (1.6 ± 0.4) × 10 -4 , (1.9 ± 0.4) × 10 -4 and (1.5 ± 0.4) × 10 -4 for the uptake of C2H2 on Mg2SiO4, MgFeSiO4 and Fe2SiO4, respectively, indicating that  is independent of Mg or Fe active sites. The uptake of C2H2 was also measured on SiO2 and SiC as analogues for meteoric smoke particles T but was found to be below the detection limit ( < 6 × 10 -8 and < 4 × 10 -7 , respectively). The rate of cyclo-trimerization of C2H2 to C6H6 was found to be 2.6 × 10 -5 exp(-741/T) s -1 , with an uncertainty ranging from ± 27 % at 115 K to ± 49 % at 181 K. A chemical ablation model was used to show that the bulk of cosmic dust particles (radius 0.02 -10  T mass loss through sputtering), thereby providing a significant surface for heterogeneous 2 chemistry. A 1D model of dust sedimentation shows that the production of C6H6 via uptake of C2H2 on cosmic dust, followed by cyclo-trimerization and desorption, is probably competitive with gas-phase production of C6H6 between 80 and 120 km.

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“…A reaction, which has attracted much attention in the past, is the unusual trimerization of acetylene to benzene on the Pd(1 1 1) surface [1][2][3][4][5][6][7][8][9][10][11]. The onset of the reaction is coupled to a coverage threshold of acetylene and supposed to proceed via a trimerization mechanism [1,[5][6][7][8][9]11].…”

Section: Introductionmentioning

confidence: 99%