Ion-radical Mechanism of Low-temperature Benzene Polycondensation on ZSM-5 Zeolites

Bolshov, Vadim A.; Toktarev, Alexander V.; Volodin, Alexander M.

doi:10.1070/mc1994v004n06abeh000418

Cited by 8 publications

(12 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…222 On the basis of ESR evidence, 40 •+ was also proposed as the key intermediate in the polycondensation of benzene on ZSM-5 at temperatures below ∼125 °C. 223 The observation of 40 •+ challenges the "classic" electrophilic substitution mechanism for aromatic substitution. Similarly, substituent effects observed for the vapor-phase nitration of aromatics with dinitrogen tetroxide over Beta zeolite correlate better with the ionization potential of the aromatics than with the Hammett coefficients.…”

Section: Va5 Adsorption Of Benzene and Derivativesmentioning

confidence: 99%

Generation and Reactions of Organic Radical Cations in Zeolites

2002

View full text Add to dashboard Cite

Section: Va5 Adsorption Of Benzene and Derivativesmentioning

confidence: 99%

Generation and Reactions of Organic Radical Cations in Zeolites

2002

View full text Add to dashboard Cite

“…The formation of naphthalene via a radical mechanism seems also to be thermodynamically more favored than via a possible condensation reaction [16]. It is obvious that a high copper concentration leads to a high concentration of benzene radical cations which are finally responsible for the high amounts of naphthalene and biphenyl products on Cu/HZSM5-(1.02, 20).…”

Section: The Influence Of the Copper Concentrationmentioning

confidence: 98%

“…(4) a superoxide anion can react with a benzene radical cation from the benzene adsorption to form a phenyl peroxy radical. Furthermore, two PhOO • radicals can dimerize and via elimination of dioxygen two PhO • radicals can be formed [15,16]:…”

Section: The Role Of Coppermentioning

confidence: 99%

Aerobic one-step oxidation of benzene to phenol on copper exchanged HZSM5 zeolites: A mechanistic study

Tabler

Häusser

Roduner

2013

Journal of Molecular Catalysis A: Chemical

View full text Add to dashboard Cite

Various Cu/HZSM5-zeolites were prepared and their catalytic properties were investigated by product analysis via GC/MS chromatography in order to trace down the mechanism of the gas phase one-step oxidation of benzene to phenol with molecular oxygen. Comparison of Cu free and Cu containing zeolites showed that the activation of O 2 takes place at copper centers of the zeolite and high copper loadings lead to high yields of deep oxidation products (CO, CO 2 ). No phenol was formed in the absence of BrØnsted acid sites, i.e. on Cu/KZSM5, revealing the bifunctionality of the Cu/HZSM5 zeolite. The yields of the various oxidation products and thus the selectivity towards phenol can be influenced by variation of the relative O 2 concentration in the reaction mixture, indicating the possibility of a stoichiometric use of O 2 . The role of the superoxide radical ion O 2•-as a reactive intermediate is discussed and a radical ionic reaction mechanism is suggested.

show abstract

“…Moreover, reaction 2 with the formation of hydrogen instead of water has been shown to be thermodynamically favorable for oligomerization v/a the cation radical pathway [9]. The latter is known to suppress the spectra of cation radicals due to the competition for adsorption sites, while this oligomerization process appears to be general enough for aromatic cation radicals on zeolites.…”

Section: Cat-o + (Cj-i H + ---> Cat + + +mentioning

confidence: 99%

“…Therefore, biphenyl is not immediately formed from benzene cation radicals as it used to be considered [9,12]. Meanwhile their subsequent oligomerization with the formation of biphenyl and heavier products is suppressed.…”

Section: C6i-i6 + D-c6h6 ---) C12nlg -T-h2mentioning

confidence: 99%

Suppression of radical-cationic benzene oligomerization on sulfated zirconia

Bedilo

Volodin

1999

React Kinet Catal Lett

Self Cite

View full text Add to dashboard Cite

Abs~a~The effect of catalyst activation conditions on transformations of bevzene cation radicals on sulfated zirconia has been studied by in situ ESR spectroscopy. After the catalyst activation at 300~ there was no oligomerization of the cation radicals to biphenyl and heavier products, which is observed after catalyst calcination at 500~It has been suggested that the oligomerization is suppressed by the presence of strong Br6nsted sites on the surface.

show abstract

Ion-radical Mechanism of Low-temperature Benzene Polycondensation on ZSM-5 Zeolites

Cited by 8 publications

References 4 publications

Generation and Reactions of Organic Radical Cations in Zeolites

Generation and Reactions of Organic Radical Cations in Zeolites

Aerobic one-step oxidation of benzene to phenol on copper exchanged HZSM5 zeolites: A mechanistic study

Suppression of radical-cationic benzene oligomerization on sulfated zirconia

Contact Info

Product

Resources

About