Infrared study of unsaturated surface compounds on supported bimetallic catalysts

Kharson, M. S.; Kiperman, S. L.

doi:10.1007/bf02068183

Cited by 5 publications

(3 citation statements)

References 5 publications

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“…When modified by NaCl, the Na ions appear to enhance the bond strength of chlorine to silver [31]. Furthermore, another detrimental effect of too much alkali could be ascribed to increased isomerization of the epoxide [32,33].…”

Section: Propylene Epoxidation On the Different Silver Catalystsmentioning

confidence: 99%

Epoxidation of propylene on NaCl-modified silver catalysts with air as the oxidant

Luo

Lei

et al. 2002

Applied Catalysis A: General

105

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Section: Propylene Epoxidation On the Different Silver Catalystsmentioning

confidence: 99%

Epoxidation of propylene on NaCl-modified silver catalysts with air as the oxidant

Luo

Lei

et al. 2002

Applied Catalysis A: General

105

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“…It can be largely explained by the absence of experimental techniques and conditions amenable to such studies. The majority of the industrial catalysts for the aromatization reaction to date are primarily based on supported platinum. − Hence, the major experimental technique for characterization of such systems was chromatography. Other techniques, such as infrared spectroscopy and temperature-programmed reaction, were rarely used because of the experimental difficulties.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Dehydrocyclization of 1-Hexene to Benzene on Cu₃Pt(111): Identification of 1,3,5-Hexatriene as Reaction Intermediate

et al. 1998

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We report here ultrahigh vacuum studies of the dehydrocyclization reaction of submonolayer coverages of 1-hexene to benzene on a Cu3Pt(111) single crystal surface, using reflection-absorption infrared spectroscopy (RAIRS), near edge X-ray absorption fine structure (NEXAFS) studies, and temperatureprogrammed reaction/desorption (TPR/D) spectrometry. As discussed in a previous TPR/D paper, at surface coverages up to 13% of monolayer saturation, 1-hexene forms benzene on a Cu3Pt(111) surface. Selectivity to benzene formation is 70 ( 10%, with the remaining 30 ( 10% of the adsorbed 1-hexene dehydrogenating irreversibly to surface carbon and H2. For higher coverages, molecular desorption commences. Spectroscopic identification of the intermediates of the reaction of 1-hexene and other model compounds, such as a 1,3,5-hexatriene, with a Cu3Pt(111) surface suggests that 1-hexene and 1,3,5-hexatriene have a common intermediate, and this intermediate has been identified as a rehybridized hexatriene species. Other model compounds, such as trans-3-hexene, have also been used to provide further understanding of the mechanism of the aromatization reaction.

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“…Since the platinum-containing industrial catalysts are usually used as supported platinum, − studies of the real catalysts were limited by the number of techniques available for characterization of the reaction occurring on such surfaces. Chromatography was the most valuable technique to quantify the reaction products.…”

Section: Introductionmentioning

confidence: 99%

Mechanism of Dehydrocyclization of 1-Hexene to Benzene on Cu₃Pt(111)

Teplyakov

Bent

1997

J. Phys. Chem. B

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Even though dehydrocyclization is widely practiced in heterogeneous catalysis for the conversion of straight chain hydrocarbons into aromatic compounds, knowledge of the mechanism of this process remains limited, largely because it has not previously been possible to carry out the reaction under conditions amenable to detailed mechanistic studies. We report here ultrahigh vacuum studies of the dehydrocyclization of submonolayer coverages of 1-hexene to benzene on a Cu3Pt(111) single-crystal surface. On the basis of temperature-programmed reaction/desorption (TPR/D) studies of dehydrocyclization of 1-hexene as compared to the reactions of cyclohexene, 1,3-cyclohexadiene, 1,4-cyclohexadiene, benzene, 1,3-hexadiene, and 1,3,5-hexatriene with a Cu3Pt(111) surface, it is found that a rate-determining step in the overall reaction is cyclization. The obtained results show that at low coverages of mono- and bi-unsaturated cyclic compounds, benzene is the only gas-phase hydrocarbon product of reaction of these compounds with a Cu3Pt(111) surface, while after a certain threshold in coverage, molecular desorption of these compounds commences. The temperature of benzene evolution for all the cyclic compounds studied is between 200 and 300 K, whereas for linear chain hydrocarbons this temperature is ∼400 K. TPR/D studies of product hydrogen evolution show that all cyclic compounds evolve hydrogen upon reaction with the surface at the temperatures close to that of hydrogen recombination−desorption reaction, 220−290 K. On the other hand, 1-hexene evolves hydrogen upon reaction with this surface at two different temperatures: ∼270 and ∼405 K. Combining these results with the studies of hydrogen evolution from 1,3,5-hexatriene, which occurs at 400 K, we suggest that cyclization is a rate-determining step and that mono- and bi-unsaturated C6 cyclic compounds are not the reaction intermediates for the dehydrocyclization of 1-hexene to benzene.

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Infrared study of unsaturated surface compounds on supported bimetallic catalysts

Cited by 5 publications

References 5 publications

Epoxidation of propylene on NaCl-modified silver catalysts with air as the oxidant

Epoxidation of propylene on NaCl-modified silver catalysts with air as the oxidant

Mechanism of Dehydrocyclization of 1-Hexene to Benzene on Cu₃Pt(111): Identification of 1,3,5-Hexatriene as Reaction Intermediate

Mechanism of Dehydrocyclization of 1-Hexene to Benzene on Cu₃Pt(111)

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Infrared study of unsaturated surface compounds on supported bimetallic catalysts

Cited by 5 publications

References 5 publications

Epoxidation of propylene on NaCl-modified silver catalysts with air as the oxidant

Epoxidation of propylene on NaCl-modified silver catalysts with air as the oxidant

Mechanism of Dehydrocyclization of 1-Hexene to Benzene on Cu3Pt(111): Identification of 1,3,5-Hexatriene as Reaction Intermediate

Mechanism of Dehydrocyclization of 1-Hexene to Benzene on Cu3Pt(111)

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Mechanism of Dehydrocyclization of 1-Hexene to Benzene on Cu₃Pt(111): Identification of 1,3,5-Hexatriene as Reaction Intermediate

Mechanism of Dehydrocyclization of 1-Hexene to Benzene on Cu₃Pt(111)