Toluene Formation from Coadsorbed Methanethiol and Benzenethiol on the Ni(111) Surface

Kane, S. M.; Huntley, D. R.; Gland, John L.

doi:10.1021/ja953926t

Cited by 12 publications

(19 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Diene formation occurs in the presence of oxygen because the oxygen reacts with surface hydrogen to form hydroxyl groups or water well below the hydrocarbon desorption temperatures. [29][30][31] This reaction depletes the surface hydrogen available for the hydrogenation reaction.…”

Section: Resultsmentioning

confidence: 99%

Desulfurization of Thiophenic Compounds by Ni(111): Adsorption and Reactions of Thiophene, 3-Methylthiophene, and 2,5-Dimethylthiophene

1996

Self Cite

View full text Add to dashboard Cite

The adsorption and reactivity of thiophene, 2,5-dimethylthiophene, and 3-methylthiophene on Ni(111) have been examined. The saturation coverages of the three molecules are similar, about 0.13 monolayer (ML), and in all cases alkenes are the major hydrocarbon products. On initially clean surfaces, decomposition to sulfur, carbon and hydrogen is the major pathway, but the selectivity to hydrocarbon production can be enhanced by a factor of about 3 by predosing the surface with hydrogen. Sulfur is easily removed from the ring, and C-S bond scission is complete by 150 K. The rate-limiting step in alkene formation is hydrogenation of a highly unsaturated hydrocarbon intermediate. The hydrocarbon intermediates formed are difficult to unambiguously identify but are most likely cyclic structures, retaining the C 4 framework.

show abstract

Section: Resultsmentioning

confidence: 99%

Desulfurization of Thiophenic Compounds by Ni(111): Adsorption and Reactions of Thiophene, 3-Methylthiophene, and 2,5-Dimethylthiophene

1996

Self Cite

View full text Add to dashboard Cite

show abstract

“…To provide a basis for comparing the reactivities of cyclohexyl and phenyl thiols, a brief summary of benzenethiol reactivity on the same Ni(111) surface follows. The C−S bond in benzenethiol is broken by direct interaction with the nickel surface at 260 K. The formation of an adsorbed phenyl intermediate is clearly confirmed by studying the reactivity of coadsorbed methanethiol and benzenethiol on the Ni(111) surface. , Toluene formation clearly indicates that phenyl and methyl intermediates are formed and couple at 260 K. In the presence of large amounts of coadsorbed hydrogen, the phenyl intermediate can be hydrogenated to form benzene at the same temperature. , Therefore, hydrogen cannot be directly involved in C−S bond breaking. C−S bond activation is independent of surface hydrogen concentration, but the availability of hydrogen increases the yield of benzene at 260 K by hydrogenating the phenyl formed and inhibiting dehydrogenation of surface intermediates.…”

Section: Introductionmentioning

confidence: 92%

“…Benzenethiol has been used extensively as a model reactant because of chemical analogies with important complex model sulfur-containing species such as benzothiophene and because of the stability of the C-S bond adjacent to an aromatic ring. A series of previous papers [10][11][12][13] have shown that the C-S bond breaking in benzenethiol does not involve hydrogen for these nickel surfaces. This paper is focused on the effect of replacing the aromatic group in benzenethiol with a saturated C 6 group.…”

Section: Introductionmentioning

confidence: 99%

“…The C-S bond in benzenethiol is broken by direct interaction with the nickel surface at 260 K. The formation of an adsorbed phenyl intermediate is clearly confirmed by studying the reactivity of coadsorbed methanethiol and benzenethiol on the Ni(111) surface. 12,13 Toluene formation clearly indicates that phenyl and methyl intermediates are formed and couple at 260 K. In the presence of large amounts of coadsorbed hydrogen, the phenyl intermediate can be hydrogenated to form benzene at the same temperature. 10,11 Therefore, hydrogen cannot be directly involved in C-S bond breaking.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Cyclohexanethiol Adsorption and Reaction on the Ni(111) Surface

Kane

Gland

1998

J. Phys. Chem. B

View full text Add to dashboard Cite

The surface reactions of cyclohexanethiol (CHT) have been characterized on the Ni(111) surface as part of a larger study of C−S bond activation in thiols. The C−S bond is broken by direct interaction with the nickel surface, and hydrogen is primarily involved in subsequent hydrogenation of desulfurized hydrocarbon intermediates. CHT adsorbs at 120 K primarily as cyclohexylthiolate. With heating, C−S bond scission is observed at 240 K evidenced by both sulfur XPS and cyclohexane desorption. Addition of coadsorbed hydrogen does not modify the temperature or extent of desulfurization. A comparison of desulfurization in CHT and benzenethiol indicates that the energetics for C−S bond activation correlate with bond strength, suggesting a radical mechanism. Only a small fraction of the cyclohexane desorbs at 240 K. Most of the gas-phase desulfurized products desorb in a second process starting at 300 K. Cyclohexane is the first product in this second process. Stepwise dehydrogenation of C6 surface intermediate(s) results in desorption of increasingly dehydrogenated C6 hydrocarbons with increasing temperature, culminating in benzene desorption at 315 K. Increasing dehydrogenation with increasing temperature is correlated with free hydrogen desorption in this same temperature range. A final disproportionation process in the 450 K range produces a small amount of benzene. With increasing temperature no further gas-phase organics are produced. Overall, about half of the CHT in a monolayer undergoes complete dehydrogenation to form adsorbed carbon and sulfur. For small coverages (<0.07 ML) most of the CHT undergoes complete decomposition on the Ni(111) surface. For these small coverages, no cyclohexane is observed at 240 K, even in the presence of coadsorbed hydrogen. Smaller amounts of C6 hydrocarbons are formed in the 300−315 K temperature region. It is interesting to note that a small fraction of CHT remains molecular following adsorption at low temperature, producing a CHT peak at 180 K even for low coverages.

show abstract

“…Recent experiments with coadsorbed methanethiol and benzenethiol have yielded important information about the role of hydrogen in C−S bond activation on nickel surfaces. , In addition to the hydrogenolysis products methane and benzene, toluene formation also results from the thermal reaction of the coadsorbed thiols. The toluene formation temperature corresponded exactly with the methane and benzene formation temperatures.…”

Section: Introductionmentioning

confidence: 99%

Benzenethiol Reaction on the Clean and Hydrogen Pretreated Ni(100) Surface

Kane¹,

Huntley²,

Gland³

1998

J. Phys. Chem. B

View full text Add to dashboard Cite

Benzenethiol reactions on clean and hydrogen precovered Ni(100) surfaces have been studied in order to characterize C-S bond breaking. Benzenethiol adsorbs at 90 K as phenylthiolate and surface hydrogen. The dominant benzene formation pathway for large coverages of benzenethiol occurs at 270 K. C-S bond breaking involves direct reaction of phenylthiolate with the nickel surface; hydrogen does not appear to be directly involved. The rate-limiting C-S bond breaking step is followed by rapid hydrogenation of adsorbed phenyl to form benzene which desorbs from the sulfur covered surface. Deuterium incorporation studies support this mechanism since single hydrogen addition dominates as expected for hydrogenation of an adsorbed phenyl intermediate. For the benzenethiol saturated surface (0.30 monolayer), hydrogen preadsorption increases the temperature for benzene formation by up to 20 K and increases the benzene yield up to 37%. Reorientation of the phenylthiolate away from the surface in the presence of large coadsorbed hydrogen coverages is indicated by vibrational characterization. This hydrogen induced reorientation appears to be associated with the increase in C-S bond activation energy. Above 500 K dehydrogenation of adsorbed phenylthiolate derived species results in formation of surface bound polyaromatic hydrocarbons (PAHs) coadsorbed with sulfur; the hydrogen formed in this process desorbs. For low coverages of benzenethiol, no 270 K benzene is observed due to increased dehydrogenation by the surface. A small amount of benzene is formed by disproportionation above the temperature of free hydrogen desorption (400 K). A comparison of benzenethiol reactions on the three low Miller index surfaces of nickel clearly indicates that hydrogen availability at reaction temperature has a large influence on benzene formation. Hydrogen desorption prior to C-S bond activation on the Ni(100) surface limits benzene formation, while substantial hydrogen availability on the Ni(111) and Ni(110) surfaces facilitates benzene formation.

show abstract

Toluene Formation from Coadsorbed Methanethiol and Benzenethiol on the Ni(111) Surface

Cited by 12 publications

References 25 publications

Desulfurization of Thiophenic Compounds by Ni(111): Adsorption and Reactions of Thiophene, 3-Methylthiophene, and 2,5-Dimethylthiophene

Desulfurization of Thiophenic Compounds by Ni(111): Adsorption and Reactions of Thiophene, 3-Methylthiophene, and 2,5-Dimethylthiophene

Cyclohexanethiol Adsorption and Reaction on the Ni(111) Surface

Benzenethiol Reaction on the Clean and Hydrogen Pretreated Ni(100) Surface

Contact Info

Product

Resources

About