Pyrolyse thermique des [14C] et [3H] ortho et para-cresols

Cypres, René; Bettens, Bernard

doi:10.1016/0040-4020(75)80045-7

Cited by 25 publications

(10 citation statements)

References 9 publications

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“…Higher reactivities of o-and p-methyl groups were also reported in the literature [16,17,43,14]. As for the reactivities of oand p-methyl groups, relative yields of p-/o-cresols (12.9/6.2) from 2,4-xylenol (11) and o,p-/o,o-xylenols (5.6/1.5) from trimethylphenol 13 [number in parentheses: yield (wt%)] indicate that the o-methyl group is more reactive than the p-methyl group. Masuku [17] and Buryan [43] also reported similar relative reactivities.…”

Section: Gc/ms-detectable Tarsupporting

confidence: 64%

“…There is a large volume of literature [8,9,[24][25][26][27] dealing with the thermal decomposition of phenol and catechol, focusing on PAH formation. A cyclopentadienyl radical is proposed as an important precursor of PAH [28][29][30].…”

Section: Two Stage Cokingmentioning

confidence: 99%

“…Several papers describe the thermal decomposition of catechols, phenols [8][9][10][11][12][13] and cresols/xylenols [14][15][16][17]. However, thermal decomposition behaviors including coking and gas formation have not been compared for guaiacyl-and syringyl-derived pyrolysis intermediates.…”

Section: Introductionmentioning

confidence: 97%

“…Catechols/pyrogallols, cresols/xylenols, phenol, polyaromatic hydrocarbons (PAHs), coke and gas are reported as the secondary products [8][9][10][11][12][13][14][15][16][17]. Two competitive reactions, i.e., O-CH 3 bond homolysis [18] and radical-induced OCH 3 rearrangement (ipso substitution) [18], are known to be important secondary reaction pathways.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Thermal reactivities of catechols/pyrogallols and cresols/xylenols as lignin pyrolysis intermediates

Asmadi

Kawamoto

Saka

2011

Journal of Analytical and Applied Pyrolysis

116

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a b s t r a c tThermal reactivities of lignin pyrolysis intermediates, catechols/pyrogallols (O-CH 3 homolysis products) and cresols/xylenols (OCH 3 rearrangement products), were studied in a closed ampoule reactor (N 2 /600 • C/40-600 s) to understand their roles in the secondary reactions step. Reactivity tends to be enhanced by increasing the number of substituent groups on phenol and this effect was greater for -OH than for -CH 3 . Thus, catechols/pyrogallols were more reactive than cresols/xylenols and syringol-derived products were more reactive than corresponding guaiacol-derived products. Catechols/pyrogallols were effectively converted into CO (additionally CO 2 in the case of pyrogallols) in the early stage of pyrolysis. In contrast, cresols/xylenols were comparatively stable and produced H 2 , CH 4 and demethylation products (cresols and phenol) after prolonged heating. All intermediates except phenol and 2-ethylphenol formed coke during a long heating time of 600 s (second stage coking). Based on the present results, the roles of intermediates in tar, coke and gas formation from guaiacol and syringol are discussed at the molecular level, focusing on their differences. Molecular mechanisms of gas formation from pyrogallols and demethylation of cresols/xylenols are also discussed.

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Section: Gc/ms-detectable Tarsupporting

confidence: 64%

Section: Two Stage Cokingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Thermal reactivities of catechols/pyrogallols and cresols/xylenols as lignin pyrolysis intermediates

Asmadi

Kawamoto

Saka

2011

Journal of Analytical and Applied Pyrolysis

116

View full text Add to dashboard Cite

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“…And Cypres and Bettens suggested that PFs degrade to yield relatively large amounts of cresol, which is subsequently converted to phenol and methane, as shown in Fig. 9 [24]. Similar reactions may be able to occur in the carbonized sample, particularly at the carbon atoms having hydroxyl functional groups and at the methylene or alkyl ether units.…”

Section: Chemical-structure Changes Occurring In the Range 600-800 • Cmentioning

confidence: 86%

Comparative study of carbon dioxide and nitrogen atmospheric effects on the chemical structure changes during pyrolysis of phenol–formaldehyde spheres

Kim

Yun

et al. 2004

Journal of Colloid and Interface Science

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Investigations of Phenolic Resins as Carbon Precursors for C‐Fiber Reinforced Composites

Mucha¹,

Wielage²,

Krenkel³

2009

Advanced Processing and Manufacturing Technologies for Structural and Multifunctional Materials III

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Different Carbon matrix precursors are used for the fabrication of C/C-SiC materials by the liquid silicon infiltration (LSI) route. Phenolic resins represent an important class of suited resins which includes the resol and novolac types. For these resins a universal chemical and structural point of view is adopted. It is based on the aromatic bonding state and leads to the concepts for the carbon yield and the basic structural units after carbonisation. The mechanisms that allow substituents to control the reactivity of the aromatic ring structures, control the phenol-formaldehyde-addition as well, which predetermines the character of its basic resin product (resol or novolac). Direct curing (temperature or acid) is possible for resols. Novolacs are thermoplastics and not curable without additives. With suited addives, novolacs can be cured indirectly. Novolac with an additive (eg. hexamethylentetramine) form a product which is cured at elevated temperatures and hence forming characteristic bridges in casetypical ratios by condensation reactions and thereby releasing gaseous reaction products. The primary bridges show ranges of thermal stability and exhibit different mechanical strengths. This accounts also for the phase of thermal transformations when bridges transform into other bridge types or disintegrate. These thermally induced transformations are investigated for a few resol type resins on a macroscopic mechanical level using the Dynamical Mechanical Thermal Analysis (DMTA) and characterised supplementary by thermo-gravimetric means. The generated porosity is a result of the fabrication history and subjected to microstructural investigations. Furthermore attention is paid to the effect of porosity for the Si-infiltration. INTRODUCTIONThe availability of phenolic resins in a defined chemical state is required for the fabrication of CFRP, C/C-and C/C-SiC materials in a reproducible way. Nevertheless microscopic investigations of the obtained matrix show that it is not a homogeneous, dense component and it exhibits porosity of different shape and size. The occurrence of porosity is depending on the type of resin and its processing conditions. Pore sizes may range from macro-to nanoscale and can be revealed by suited preparation and analysis technologies. Reasons for the generation of pores originate in the resin's molecular constitution, which is essential for the initial curing and the subsequent thermal conversions of the bridges and the cracking processes at higher temperatures. The gaseous products from the reaction are released from or embedded into the resin depending on the resin's constitution. To get accustomed to the class of resins it is required to know the underlying principles of bonding. Phenolic resins are multi particle systems. Central field models that are suited to describe atoms are not adequate to describe the electron distributions within molecules and multi particle formalisms have to be applied. Unfortunately such multi particle systems can not be solved precisely and simplified mode...

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Pyrolyse thermique des [14C] et [3H] ortho et para-cresols

Cited by 25 publications

References 9 publications

Thermal reactivities of catechols/pyrogallols and cresols/xylenols as lignin pyrolysis intermediates

Thermal reactivities of catechols/pyrogallols and cresols/xylenols as lignin pyrolysis intermediates

Comparative study of carbon dioxide and nitrogen atmospheric effects on the chemical structure changes during pyrolysis of phenol–formaldehyde spheres

Investigations of Phenolic Resins as Carbon Precursors for C‐Fiber Reinforced Composites

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