Research Article
Volume 1 Issue 2 - 2015
Formation of Polycyclic Compounds from Phenols by Fast Pyrolysis
Minami Akazawa1, Yasuo Kojima2* and Yoshiaki Kato3
1Graduate school of Science and Technology, Niigata University, Japan
2Department of Applied Biochemistry, Niigata University, Japan
*Corresponding Author: Yasuo Kojima, Department of applied Biochemistry, Faculty of Agriculture, Niigata University, Niigata, Japan.
Received: December 20, 2014; Published: February 12, 2015
Citation: Yasuo Kojima., et al. “Formation of Polycyclic Compounds from Phenols by Fast Pyrolysis”. EC Agriculture 1.2 (2015): 67-85.
Abstract
An analytical pyrolysis gas chromatography mass spectrometry method has been used for investigation into the reaction mechanism leading to polycyclic compounds such as polycyclic aromatic hydrocarbons and heterocyclic compounds. Six phenols with different pendant groups were used in this study. The formation mechanism of producing naphthalene and dibenzofuran from phenol is proposed. In this mechanism, a cyclohexadiene-1-one radical was an important intermediate for the formation of these products. Three unique products were detected from m-cresol: 3,7-dimethyldibenzofuran, 1,7-dimethyldibenzofuran and 1,9-dimehyldibenzofuran. Cyclohexadiene-1-one radical was also found to be an important intermediate for dimerization reaction. Guaiacol pyrolysis yielded phenol as the major product, with a small amount of benzofuran. There arrangement of methoxyl group to methyl group and addition of methyl radical on phenoxy radical was a crucial route in this mechanism. From pyrocatechol, three indanone derivatives were produced via CO elimination with aromatic ring opening followed by pentadienone formation. After two proton donation, three pentanone biradicals were intra molecularly coupled to form indanones. From syringol pyrolysis, only benzofuran was produced, and from ethyl phenol, three types of benzofuran were detected containing different pendant groups such as methyl, ethyl and ethenyl groups. These results indicated that the phenol’s ortho position is a vital reaction site for the formation of polycyclic compounds in pyrolysis.
Keywords: Phenols; Analytical pyrolysis; polycyclic compound; Formation mechanism
Introduction
Various polycyclic compounds, polycyclic aromatic hydrocarbons (PAHs) and other hetero-polycyclic compounds are generated from biomass combustion in residential stoves, fireplaces and manufacturing biomass boilers [1-3], and some are ubiquitous and toxic pyrolysis products [4,5]. PAHs and other organic compounds were detected in ash from biomass combustion [6]. This indicated that the analysis of PAHs content in ash is necessary when utilized as fertilizer. Fabri et al. [7] found that the PAHs content in a bio-oil from fast pyrolysis of poplar wood increased dramatically when pyrolysis was conducted over HZSM-5 zeolite. Carlson et al reported that aromatics and polymer fragments are produced from catalytic fast pyrolysis of carbohydrate on solid acid catalyst [8].
Bio-oil produced from fast pyrolysis of biomass is considered a new resource and substitute for fuel oil or diesel in many static applications such as boilers, furnaces, engines and turbines for electricity generation and chemical production [9]. Many types of reactors have been examined for bio-oil production, and pilot plants have also been established worldwide [10,11]. Many agricultural crops and processes yield residues that can potentially be used for energy applications, in a number of ways. Several studies on pyrolysis conversion using residual plants and crops, such as softwood bark [12,13] hardwood [14],wheat straw [15], rice husk [16], tobacco residue [17], orange waste [18], giant cane [19], palm oil waste [20]and microalgae [21] have been reported. These plants consist of cellulose, hemicellulose and lignin. Therefore, bio-oil is a mixture of pyrolysates derived from these components. Lignin is the second most abundant natural biopolymer found in lignocellulosic plants, andit is a heterogeneous and complex polymer synthesized mainly from three p-hydroxycinnamyl alcohols differing in their degrees of methoxylation : p-coumaryl, coniferyl and sinapyl alcohol. Each monolignol gives rise to a different lignin type called the p-hydroxyphenyl (H), guaiacyl (G) and syringyl (S) units, respectively, which together generate a variety of structures and linkages within the polymer [22-24]. Therefore, various phenols are generated from pyrolysis of biomass and lignin derivatives [25,26]. Some of these phenols can be further pyrolyzed to form more stable polycyclic structures such as benzofurans and PAHs. This hypothesis is supported by the following reports in which polycyclic compounds were generated from lignin model compounds. It was reported that reported that pyrolysis of guaiacol and 2-ethoxyphenol yielded benzofuran and xanthene derivatives as well as from tars [27,28]. Britt et al. [29] found benzofuran and dehydrobenzofuran in the pyrolysate from β-alkyl aryl ether model compound pyrolysis. Faix et al. [30] also detected 9, 10-dihydrophenanthrenein addition to naphthalene from the pyrolysis products of lignin dimer models. These model phenols were induced from biomass pyrolysis as primary products, and some of the phenols are converted to polycyclic compounds by a radical coupling reaction. In this reaction pathway, lignin derivatives and biomass yielded polycyclic products. From Kraft lignin pyrolysis, polycyclic compounds such as naphthalene and 3-methoxy-2-naphtalenol were detected [31], and 2,3-dihydrobenzofuran was found from pyrolysate of moso bamboo meal [32] and switch grass [33]. Naphthalene and methylnaphthalene were also detected from the pyrolysate of alfalfa [34]. From pyrolysate of tobacco stem, benzofuran, 2,3-dihydrobenzofuran, indene, naphthalene and acenaphtylene were founded [35].
As mentioned above, many monomeric phenols were formed by pyrolysis of dimeric lignin models, isolated lignin and lignocellulose. These monomeric phenols consist of C6–C3, C6–C2, C6–C1 and a C6 structure. They are produced by primary pyrolitic degradation of lignin polymer and subjected to further homolytic reactions such as elimination of pendant groups and condensation. These low molecular primary products can be subjected to inter and/or inner condensation to produce polycyclic compounds as secondary pyrolysates. The bio-oil produced from pyrolysis of biomass consists of phenols; therefore, additional formation and emission of PAHs during combustion of bio-oil is of concern. In some case, bio-oil may be used as an agricultural boiler fuel, and the possibility of contamination of crops by PAHs is to come out. This study evaluates the formation mechanism of polycyclic compounds such as PAHs and furans during a fast pyrolysis process and explores the possibility of the formation and emission during bio-oil combustion.
Materials and Methods
Six phenols were purchased from Wako Pure Chemical Industries, Ltd., Osaka, Japan as guaranteed grade. These samples were pyrolyzed with a Frontier Lab PY-2020iD pyrolizer. Each dried sample cup was inserted into the pyrolizer chamber, which was previously purged with helium gas. After pre-heating the furnace in the pyrolizer (400-600°C), each sample was placed in the middle of the furnace for 0.2 min and then moved to the top of the furnace. The pyrolysates produced at these temperatures were separated and analysed using a GC/MS system coupled directly to the pyrolizer. The GC/MS conditions are described below.
An Agilent GC/MS system consisting of an Agilent 6890 gas chromatograph and an Agilent 5975 inert MS selective detector was used to separate and obtain the MS spectra of the compounds derived from each sample. The samples were injected in split mode (100 : 1 ratio). The carrier gas was helium with a flow rate of 0.93 mL/min. The oven was initially maintained at 40°C for 5 min and ramped at a rate of 4°C/min up to 250°C, and then maintained at this temperature for 60 min. An Rtx-Wax cross-linked polyethylene glycol fused-silica capillary column (RESTEC, 60 m × 0.25 mm i.d., 0.25 μm film thickness) was used to separate the samples. The column was interfaced directly to the electron impact ion source of the MS. The ion source was operated at 70eV, and the injection port was set at 250°C. The separated peaks were identified using the NIST05 MS Library.
Results and Discussion
Formation of phenols and polycyclic compounds from Japanese cedar by fast pyrolysis
Area percentage, rather than the absolute area, was utilized as the dependent variable to eliminate any inconsistencies due to variations in the sample size and product carryover. It was confirmed that the contribution of the area for a given peak was statistically similar between experiments. As is common for pyrolysis-GC/MS, most of the pyrolysis products were identified by comparing their mass data with data in a widely used MS database. However, some of the products were not registered in this database. Therefore, these compounds were identified using the mass fragmentation method, their GC retention times and the MS database.
Figure 1: Total ion chromatograph for bio-oil from Japanese cedar at 600°C.
The total ion chromatograph (TIC) obtained from the Py-GC/MS of Japanese cedar at 600°C is shown in (Figure 1) Several pyrolysis products were produced from wood components such as lignin, hemicellulose and cellulose. Major pyrolysis products from lignin were pyrocathecol, 4-Ethylphenol, 2-methoxyphenol (guaiacol) and phenol. As minor products, naphthalene and 1-indanone were detected. The same results were obtained from pine wood [25], guayule [33] and tobacco stem [34]. To determine the relationship of these phenols and polycyclic compounds, six phenols were prepared and subjected to pyrolysis. The structures and abbreviations of these phenols are illustrated in (Figure 2)
Figure 2: Phenols used in this study.
Pyrolysis of phenol
The TIC profile and MS spectra, with chemical structures of products (1) and (2) obtained from the Py-GC/MS of phenol at 600°C, are shown in (Figure 3). In this TIC profile, only two pyrolysis products and an unreacted starting material were detected. Generally, simple compounds (with low leaving group content) are considered more stable to thermal treatment than complex compounds with large numbers of leaving groups [35]. On the basis of their MS spectra, products (1) and (2) were identified as naphthalene and dibenzofuran, respectively.
Figure 3: Total ion chromatograph for Py-GC/MS of phenol at 600°C and mass spectra of products (1) and (2).
The yields of products (1) and (2) increased with increasing pyrolysis temperature, from 400 to 600°C (Figure 4). This indicates that the formation reactions are accelerated at higher thermal conditions and both pyrolysis products are stable under the thermal condition without thermal degradation.
Figure 4: Effect of pyrolysis temperature on product yields of (1) and (2).
The proposed formation pathways of these products are illustrated in Figure 5. Cyclopentadiene is an important intermediate for the formation of naphthalene. The formation of the cyclopentadiene intermediate is initiated by the proton radical donation from the phenolic hydroxyl group of phenol followed by the radical transfer to the ortho quinone radical (route A). Then, elimination of CO from the ortho-radical occurs to yield the corresponding pentadienyl biradical and form cyclopentadiene. The unsaturated bond in this intermediate structure is subjected to homolytic electron transfer to form two pentenyl biradicals. These biradicals couple with each other to form a polycyclic product. Naphthalene is produced by the intermolecular arrangement associated with four proton radical releases (route B). This pathway was proposed by Egsgaard et al. [36].Conversely, another formation mechanism was proposed by Evans et al. [37] and Melius et al. [38]. They reported that naphthalene is produced by a combination and rearrangement of two cyclopentadienyl radicals. The cyclopentadienyl radicals are formed from the elimination of a CO from phenol. The former pathway includes a two point coupling of biradical structures, and the latter pathway includes a one point coupling of radical structures. In both mechanisms, pentadienyl radical is a key intermediate as shown by Khachatryan et al. [39].This compound is possibly carcinogenic to humans (Group 2B) and is a known product from biomass combustion [40].
Figure 5: Proposed pathways for the formation of products (1) and (2).
Dibenzofuran is formed via radical coupling of two ortho radicals of phenol, and intermolecular condensation of a phenoxy radical with an aromatic carbon radical (route C).This formation mechanism has been proposed [37], and supported [41,42]. This compound has no serious effects on human health although it exhibits an irritating odour.
Pyrolysis of m-cresol
The TIC profile and the MS spectra, with chemical structures of products (3), (4) and (5) obtained from the Py-GC/MS of m-cresol at 600°C, are shown in Figure 6 Product (3) was identified as phenol, and it is inferred that naphthalene and dibenzofuran were produced from this product in an undetectable amount with GC as shown in 3.2. On the basis of the MS spectra, products (4), (5) and (6) were identified as 1,7-dimethyldibenzofuran, 3,7-dimethyldibenzofuran, and 1,9-dimethyldibenzofuran, respectively. In the case of pyrolysis at low temperature (400 or 500°C), these products were not detected and the starting material remained without thermal degradation.
Figure 6: Total ion chromatograph for Py-GC/MS of m-cresol at 600°C and mass spectra of products (4) and (5).
The proposed formation pathways of these products are illustrated in Figure 7. In the first step of these pathways, two types of quinonemethide radicals (5-methyl-2,4-cyclohexadiene-1-one radical and 5-methyl-3,5-cyclohexadiene-1-one radical) are formed by proton radical donation from the hydroxyl group of m-cresol (the first half of route A).These radicals are considered to be important intermediates. Radical coupling with each other yields three kinds of dimers of 5-methyl-cyclohexadiene-1-one. These dimers are then subjected to intra molecular coupling (route C), as shown in Figure 5, to form 3,7-dimethyldibenzofuran, 1,7-dimethyldibenzofuran and 1,9-dimethyldibenzofuran.
Figure 7: Proposed pathway for the formation of products (3)-(5).
Pyrolysis of guaiacol
The TIC profile and the MS spectra, with chemical structures of products (3) and (7) obtained from the Py-GC/MS of guaiacol at 600°C, are shown in Figure 8 Product (3) is the major pyrolysis product and identified as phenol, while product (7) was the minor product and identified as benzofuran.
Figure 8: Total ion chromatograph for Py-GC/MS of guaiacol at 600°C and mass spectrum of product (6).
The proposed formation pathway of product (7) is illustrated in Figure 9. Guaiacol, as a starting material, is subject to rearrangement of the methoxyl group to epoxide, which is initiated by proton radical donation from the methoxyl group. Then, the epoxide is opened by cleavage of the O–C (aromatic) bond to form the hydroxyl methyl group followed by elimination to form the o-cresol radical (route D). These reaction mechanisms are proposed by Asmadi et al. [28]. A proton radical donation at the hydroxyl group followed by addition of a methyl radical produces the biradical of 2-methylanisol. The radical undergoes intra molecular coupling to form benzofuran (route E). This compound was detected as the minor product. Therefore, this formation pathway may be an inconsequential reaction in guaiacol pyrolysis.
Figure 9: Proposed pathway for the formation of products (3) and (6).
Pyrolysis of pyrocatechol
The TIC profile and the MS spectra, with chemical structures of products (8), (9) and (10) obtained from the Py-GC/MS of pyrocatechol at 600°C, are shown in Figure 10. On the basis of their MS spectra, these products are assumed to have an indanone structure and products (8), (9) and (10) were identified as 2-indanone, 1-indanone and 1-dehydroindanone, respectively. Only product (8) was detected from the pyrolysate at 500°C, while the other products were not detected, as shown in Figure 11. The proposed formation pathways of these products are illustrated in Figure 12. The pyrolitic reaction is initiated by the formation of o-quinone from pyrocatechol, and CO elimination occurs to form a pentadienone biradical. Intra molecular radical coupling of the biradical produces cyclopentadienone as an important intermediate. The cyclopentadienone is subjected to two different electron transfers, forming two biradical structures: 3-cyclopentene-1-one (a) and 2-cyclopentene-1-one (b). Further reactions occur as two proton additions and an electron transfer occur in biradical structure (a) to form a new biradical structure (c). These biradical intermediates couple with each other and produce three indanone derivatives (route B). Coupling (a) with (c) and an electron transfer produces 2-indanone product (8), (route F). Coupling (a) with (b) and an electron transfer produces 1-dihydroindanone (product 10, route G). 1-Indanone is produced by two proton addition at the C1–C2 unsaturated bond of 1-dihydroindanone (product 9, route H).
Figure 10: Total ion chromatograph for Py-GC/MS of pyrocatechol at 600°C and mass spectra of products (7)-(9) .

Figure 11: Effect of pyrolysis temperature on products yields of (7)-(9).

Figure 12: Proposed pathway for the formation of products (7)-(9) from pyrocatechol .
Pyrolysis of syringol
The TIC profile and MS spectra, with chemical structures of products (7) and (11-15) obtained from the Py-GC/MS of guaiacol at 600°C, are shown in (Figure 13). Product (6) was identified as benzofuran and the only polycyclic compound obtained from syringol. Peaks 11-15 were identified as 1,3-dimethoxybenzene, guaiacol, o-cresol, 1,3-dimethyphenol and homovanillin, respectively. These compounds are formed by elimination of the methoxyl or hydroxyl groups and rearrangement of the methoxyl group to methyl or aldehyde groups. Benzofuran (product 6) is formed via a guaiacol intermediate in route E as shown in the pyrolysis of guaiacol section.
Figure 13: Total ion chromatograph for Py-GC/MS of syringol at 600°C.
Pyrolysis of ethyl phenol
The TIC profile and MS spectra, with chemical structures of products (3), (7) and (16-21) obtained from the Py-GC/MS of guaiacol at 600°C, are shown in (Figure 14). Products (3), (16), (20) and (21) are not polycyclic compounds and are identified as phenol, 4-ethylanisol, p-cresol and 4-vinylanisol, respectively. These four polycyclic products were detected as benzofuran derivatives. Product (7) was identified as benzofuran, and products (17), (18) and (19) were identified as5-metylbenzofuran, 5-ethylbenzofuran and 5-ethenylbenzofuran, respectively. The proposed formation pathways of these products are illustrated in (Figure 15). These benzofuran derivatives are formed in the same reaction route E, as shown in (Figure 9), except for ethyl radical addition. These radicals are induced from phenol, ethyl phenol and ethenyl phenol as well as o-quinonmetide. Addition of the ethyl radical tocyclohexadiene-1-one radicals followed by intra molecular radical coupling produced the dihydrobenzofuran radicals. Elimination of the two proton radicals resulted in products (7) and (17-19) (route I).
Figure 14: Total ion chromatograph for Py-GC/MS of 4-ethylphenol at 600°C and mass spectra of products (16)-(18).

Figure 15: Proposed pathway for the formation of products (16)-(18).
Conclusion
Six phenols with different pendant groups were used in this study for the investigation into the reaction mechanism leading to polycyclic compounds such as polycyclic aromatic hydrocarbons and heterocyclic compounds. The formation mechanism of producing naphthalene and dibenzofuran from phenol is proposed. In this mechanism, a cyclohexadiene-1-one radical was considered an important intermediate for the formation of these products. Three unique products were detected from m-cresol: 3,7-dimethyldibenzofuran, 1,7-dimethyldibenzofuran and 1,9-dimehyldibenzofuran. Cyclohexadiene-1-one radical was also found to be an important intermediate for the dimerization reaction. Guaiacol pyrolysis yielded phenol as the major product along with a small amount of benzofuran. In this formation mechanism, rearrangement of a methoxyl group to a methyl group and addition of a methyl radical on the phenoxy radical was a crucial route. From pyrocatechol, three indanone derivatives were produced via CO elimination with aromatic ring opening followed by pentadienone formation. After two proton donation, three pentanone biradicals were intra molecularly coupled to form indanones. From syringol pyrolysis, only benzofuran was produced, and from ethyl phenol, three types of benzofuran were detected containing different pendant groups such as methyl, ethyl and ethenyl group. From the results, it was determined that the ortho position of the phenol is considered an important reaction site for the formation of polycyclic compounds in pyrolysis. The polycyclic compounds detected in this study are formed easily from pyrolysis of phenols, and those phenols are abundant in the bio-oil. Therefore, incomplete combustion of bio-oil may lead to the emission of various polycyclic compounds.
Acknowledgements
This research was funded by the Bio-oriented Technology Research Advancement Institution (BRAIN) Grant, Japan.
Bibliography
  1. Zhang Y and Tao S. “Global atmospheric emission inventory of polycyclic aromatic hydrocarbons (PAHs) for 2004”. Atmospheric Environment 43.4 (2009): 812-819.
  2. Nolte CG., et al. “Highly polar organic compounds present in wood smoke and in the ambient atmosphere”. Environmental Science and Technology35.10 (2001): 1912-1919.
  3. Fine PM., et al. “Chemical characterization of fine particle emissions from the fireplace combustion of woods grown in the Southern United States”. Environmental Science andTechnology 36.7 (2002): 1442-1451.
  4. Bolling AK., et al. “Health effects of residential wood smoke particles: The importance of combustion conditions and physicochemical particle properties”. Particle and Fibre Toxicology 6.29 (2009): 1-20.
  5. Kocbach A., et al. “Physicochemical characterization of combustion particles from vehicle exhaust and residential wood smoke”. Particle and Fibre Toxicology 3.1 (2006): 1-10.
  6. Straka P and Havelcova M. “Polycyclic aromatic carbons and other organic compounds in ash from biomass combustion”. Acta Geodynamica et Geomaterialia 9.4 (2012): 481-490.
  7. Fabri D., et al. “GC-MS determination of polycyclic aromatic hydrocarbons evolved from pyrolysis of biomass”. Analytical and Bioanalytical Chemistry 397.1 (2013): 309-317.
  8. Carlson TR., et al. “Aromatic Production from Catalytic Fast Pyrolysis of Biomass-Derived Feedstocks”. Topics in Catalysis 52.3 (2009): 241-252.
  9. Bridgwater AV. “Renewable fuels and chemicals by thermal processing of biomass”. Chemical Engineering Journal 91.2-3 (2003): 87-102.
  10. Bridgwater AV, and Peacocke, G. “Fast pyrolysis processes for biomass”. Renewable and Sustainable Energy Reviews 4.1 (2000): 1-73.
  11. Zhang Q., et al. “Review of biomass pyrolysis oil properties and upgrading research”. EnergyConversion and Management 48.1 (2007): 87-92.
  12. Boucher ME., et al. “Bio-oils obtained by vacuum pyrolysis of softwood bark as a liquid fuel for gas turbines. Part I: Properties of bio-oil and its blends with methanol and a pyrolitic aqueous phase”. Biomass and Bioenergy 19.5 (2000): 337-350.
  13. Umemura A., et al. “Pyrolysis of barks from three Japanese softwoods”. Journal of the JapanInstitute of Energy 93 (2014): 953-957.
  14. Tzanetakis T., et al. “Liquid fuel properties of a hardwood-derived bio-oil fraction”. Energy & Fuels 22.4 (2008): 2725-2733.
  15. Fidalgo M., et al. “Comparative study of fraction from alkaline extraction of wheat straw through chemical degradation, analytical pyrolysis, and spectroscopic technology”. Journal of Agricultural and FoodChemistry 41.10 (1993): 1621-1626.
  16. Gai C., et al. “The kinetic analysis of the pyrolysis of agricultural residue under non-isothermal conditions”. Bioresource Technology 127 (2013): 298-305.
  17. Cardoso CR, and Ataide CH. “Analytical pyrolysis of tobacco residue: Effect of temperature and inorganic additives”. Journal of Analytical and Applied Pyrolysis 99 (2013): 49-57.
  18. Lopez-Velazquez MA., et al. “Pyrolysis of orange waste: A thermo-kinetic study”. Journal of Analytical and Applied Pyrolysis99 (2013): 170-177.
  19. Temiz A., et al. “Chemical composition and efficiency of bio-oil obtained from giant cane (Arundodonax L.) as a wood preservative”. BioResources8.2 (2013): 2084-2098.
  20. Abnisa F., et al. “Characterization of bio-oil and bio-char from pyrolysis of palm oil waste”. BioEnergy Research6.2 (2013): 830-840.
  21. Wang K., et al. “Fast pyrolysis of microalgae remnants in a fluidized bed reactor for bio-oil and biochar production”. Bioresource Technology 127 (2013): 494-499.
  22. Higuchi T. “Biochemistry and molecular biology”. (1997) Springer Verlag: London, United Kingdom.
  23. Boerjan W., et al. “Lignin biosynthesis”. Annual Review of Plant Biology 54 (2003): 519-546.
  24. Ralph J., et al. “Lignin: Natural polymers from oxidative coupling of 4-hydroxyphenyl-propanoids”. Phytochemistry Reviews 3.1-2 (2004): 29-60.
  25. Hassan EM., et al. “Characterization of fast pyrolysis bio-oils produced from pretreated pine wood”. Applied Biochemistry and Biotechnology 154 (2009): 182-192.
  26. Shen DK., et al. “The pyrolytic degradation of wood-derived lignin from pulping process”. Bioresource Technology 101.15 (2010): 6236-6146.
  27. Hosokawa T., et al. “Role of methoxyl group in char formation from lignin-related compounds”. Journal of Analytical and Applied Pyrolysis 84.1 (2009): 79-83.
  28. Asmadi M., et al. “Thermal reactions of guaiacol and syringol as lignin model aromatic nuclei”. Journal of Analytical and Applied Pyrolysis 92.1 (2011): 88-98.
  29. Britt PF., et al. “Pyrolysis mechanisms of lignin: Surface-immobilized model compound investigation of acid-catalysed and free-radical reaction pathways”. Journal of Analytical and Applied Pyrolysis 33 (1995): 1-19.
  30. Faix O., et al. “Pyrolysis-gas chromatography-MS spectrometry of two trimeric compounds with alkyl-aryl ether structure”. Journal of Analytical and Applied Pyrolysis 14.2-3 (1988): 135-148.
  31. Hage ERE., et al. “Structural characterization of lignin polymers by temperature-resolved in-source pyrolysis-MS spectrometry and Currie-point pyrolysis-gas chromatography/MS spectrometry”. Journal of Analytical and Applied Pyrolysis 25, (1993): 149-183.
  32. Ren X., et al. “Transformation and products distribution of moso bamboo and derived components during pyrolysis”. BioResources 8 (2013): 3685-3698.
  33. Boateng AA., et al. “Guayule (Parthenium aegentatum) pyrolysis and analysis by PY-GC/MS”. Journal of Analytical and Applied Pyrolysis 87.1 (2010): 14-23.
  34. Liu B., et al. “Pyrolysis characteristic of tobacco stem studied by Py-GC/MS, TG-FTIR, and TG-MS”. BioResources 8.1 (2013): 220-230.
  35. Hosoya T., et al. “Secondary reactions of lignin-derived primary tar components”. Journal of Analytical and Applied Pyrolysis 83.1 (2008): 78-87.
  36. Egsgaard H and Larsen E. “Thermal transformation of light tar-specific routes to Aromatic aldehydes and PAH”. Proceedings of 1st world conference on biomass for energy and industry (2001): 1468-1471.
  37. Evans CS and Dellinger B. “Mechanisms of dioxin formation from the high-temperature pyrolysis of 2-chlorophenol”. Environmental Science & Technology37 (2003): 1325-1330
  38. Melius CF., et al. “26th Symposium on Combustion”. The Combustion Institute: Pittsburgh, PA (1996): 685-692.
  39. Khachatryan L., et al. “Formation of cyclopentadienyl radical from the gas-phase pyrolysis of hydroquinone, catechol, and phenol”. Environmental Science and Technology 40.16 (2006): 5071-5076.
  40. National toxicology program, toxicology and carcinogenesis studies of naphthalene (CAS No. 91-20-3) in B6C3F1 Mice (inhalation studies), long-term study reports & abstracts, (1992) TR410.
  41. Adiunkpe J., et al. “Gas chromatography Mass spectrometry Identification of Labile Radicals Formed during Pyrolysis of Catechol, Hydroquinone, and Phenol through Neutral pyrolysis Product Mass Analysis”. ISRN Environmental Chemistryvol. 2013, Article ID 930573, 8 pages, 2013. doi:10.1155/2013/930573
  42. Truong H., et al. “Mechanisms of molecular product and persistent radial formation from the pyrolysis of hydroquinone”. Chemosphere 71.1 (2008): 107-113.
Copyright: © 2015 Yasuo Kojima., et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

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PMID: 29333536 [PubMed]

PMCID: PMC5766278


EC Neurology
Longer Duration of Downslope Treadmill Walking Induces Depression of H-Reflexes Measured during Standing and Walking.

PMID: 31032493 [PubMed]

PMCID: PMC6483108


EC Microbiology
Onchocerciasis in Mozambique: An Unknown Condition for Health Professionals.

PMID: 30957099 [PubMed]

PMCID: PMC6448571


EC Nutrition
Food Insecurity among Households with and without Podoconiosis in East and West Gojjam, Ethiopia.

PMID: 30101228 [PubMed]

PMCID: PMC6086333


EC Ophthalmology
REVIEW. +2 to +3 D. Reading Glasses to Prevent Myopia.

PMID: 31080964 [PubMed]

PMCID: PMC6508883


EC Gynaecology
Biomechanical Mapping of the Female Pelvic Floor: Uterine Prolapse Versus Normal Conditions.

PMID: 31093608 [PubMed]

PMCID: PMC6513001


News and Events

Researcher's Column Special Issue for the Month of September

Editorial office of E-Cronicon (EC) is here with a great initiation to plan a Researcher's Column special issue for the month of September. The vision of this Researcher's Column is to provide an Awareness among the society with the novel information that you will be contributing. I hope to have the participation of every author who are in association with E-Cronicon to this special issue by making it a successful initiation. Due date to share your insight is September 20, 2019. Best Column article will be picked by the Editorial office and will be provided with an "Appreciation Certificate". Take a smallest step by dropping your opinions to editor@ecronicon.uk for a biggest success.

Best Article of the Issue

The Editors of respective journals will elect one Best Article after each issue release and the authors of the selected article will be provided with a certificate of "Best Article of the Issue".

Submission Timeline for November Issue

E-Cronicon delightfully welcomes the authors for submission of novel research towards November issue of respective journals. Submissions are accepted on/before September 27, 2019.

Certification for each Publication

Corresponding Authors will be issued a "Publication Certificate" with all the Co-Authors included as a token of appreciation for publishing their work with respective journals.

Certifying for Review

E-Cronicon certify the Editors for their first review done towards respective journals.

Latest Articles

Recently published articles will be updated immediately after publication in respective journals.