Pyrolysis behavior and bonding information of coal — A TGA study

Shi, Lei; Liu, Qingya; Guo, Xiaojin; Wu, Weize; Liu, Zhenyu

doi:10.1016/j.fuproc.2012.06.023

Cited by 399 publications

(183 citation statements)

References 40 publications

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“…The large initial energy barrier (ca. 200 kJ/mol) is attributed not only to the relatively facile decarboxylation and cleavage of weak bonds between the aromatic structural units (see arrows in Figure 3a) but also to alkylation [79]. The second stage (Table 3) corresponds mainly to tar evolution, ca.…”

Section: Pyrolysis Kinetics and Thermodynamicsmentioning

confidence: 99%

Structure-reactivity relationship in pyrolysis of plastics: A comparison with natural polymers

Larraín

Carrier

Radović

2017

Journal of Analytical and Applied Pyrolysis

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Highlights• Global activation energy depends on conversion in pyrolysis of all polymers.• Activation energy variability is proportional to chemical complexity of polymers.• An Evans-Polanyi relationship for initiation reactions of polymer pyrolysis is proposed. AbstractRecent advances in plastics recycling confirm the high potential of pyrolysis technologies to enhance recovery and selectivity rates. Modelling the kinetics of this complex process to stimulate scaling-up opportunities remains a major challenge.This study is an attempt to develop practical quantitative reactivity indices for the pyrolysis of natural and synthetic polymers. Representative samples from both categories (coal and pine vs. PET, PE and PMMA) were selected. Their weight loss during pyrolysis was determined experimentally and analyzed using judicious lumping procedures for its initiation, propagation and termination steps. The combined experimental and theoretical approach allowed us to determine apparent activation energies using the isoconversional Friedman method; and the use of Benson's group contribution method generated reaction enthalpies for the initiation reactions. Increasing activation energies with conversion in each case indicated that bond scission proceeds in order of increasing bond strength. The greater chemical complexity of natural polymers was reflected in the higher coefficients of variability for activation energy and wider ranges of reaction enthalpies. A structure-reactivity relationship based on the Evans-Polanyi theory was used to test the hypothesis that primary pyrolysis kinetics is controlled by cleavage of weakest chemical bonds. While the results show that this approach is promising, especially if confirmed by extension to a larger data set, they also suggest the need to compare the relative kinetic importance of initiation and propagation steps in the sequence of polymer pyrolysis reactions.

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Section: Pyrolysis Kinetics and Thermodynamicsmentioning

confidence: 99%

Structure-reactivity relationship in pyrolysis of plastics: A comparison with natural polymers

Larraín

Carrier

Radović

2017

Journal of Analytical and Applied Pyrolysis

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“…5a) basically occurred in the temperature range below 290°C, i.e., when the temperature was above 290°C, the curve smoothed and the weight loss ratio lowered. According to the statement of the reference mentioned above (Shi et al 2013), weight loss below 290°C corresponds to the volatilization of small molecular compounds and the decomposition or dehydration condensation of oxygen-containing groups such as carboxyl and hydroxyl groups, demonstrating that the depolymerized coal samples obtained under the strongest acid condition mainly consist of small molecular substances linked with oxygen-containing groups, and the content of aromatic structure is relatively low. For sample 5 (Fig.…”

Section: Structures Of Depolymerized Coal Samples Obtained Under Diffmentioning

confidence: 99%

“…The XRD results are consistent with the FT-IR results, which may be attributed to the partial breakdown of the aliphatic chains linking the aromatic units by HNO 3 under reflux condition. It has been reported that the weight loss of coal sample under 150°C is due to the vaporization of water; the weight loss between 150 and 300°C corresponds to the volatilization of light component and the decomposition or dehydration condensation of reactive groups such as carboxyl and hydroxyl groups; the weight loss between 300 and 500°C is mainly the pyrolysis of active bridge bonds in the coal, which is a devolatilization process and tar is produced; a second pyrolysis occurs between 600 and 800°C, which is mainly a process of condensation of aromatic structures and dehydrogenation to produce semicoke (Shi et al 2013). Therefore, the first weight loss peak at 75°C of raw coal sample ( Fig.…”

Section: Properties Of Depolymerized Coal Samplesmentioning

confidence: 99%

Effect of pH conditions on the depolymerization of Wucaiwan coal by mixed acids/ultrasound method and the product structures and performance

Zhang

Maimaiti

Zhang

et al. 2017

Int J Coal Sci Technol

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The cleavage of the aliphatic chain or ether bond connecting the polycyclic aromatic hydrocarbons in coal can be achieved by not only hydrogenation reduction but also oxidative acid treatment. In this paper, coal samples from Wucaiwan in Xinjiang were pretreated with HNO 3 followed by mixed acids/ultrasound treatment. The depolymerized coal samples obtained under different pH conditions were then separated by fractional washing. The structures and properties of the resulting coal samples were studied by elemental analysis, FT-IR, XRD, TG-DTA, TEM, UV-Vis, and PL. The results showed that when pH = 0.012, the obtained coal samples were fragments stripped off from the raw coal samples by ultrasound in strong acid conditions, aliphatic hydrocarbons linked with oxygen-containing groups such as nitro group, a small amount of small aromatic molecules and mineral salts; when pH = 1.99-4.09, the obtained coal samples were polycyclic aromatic hydrocarbons linked with oxygen-containing groups such as nitro group,possessing the annulus wall of multilayer graphene fragment structures built up by sp 2 carbons, and they are typical fluorescent substances of carbon nanoparticle structure. The former has no solubility in organic solvents, while the latter can be well dissolved in polar solvents such as acetone. All the depolymerized coal samples obtained under different pH conditions exhibited good absorption and ability of fluorescence emission.

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“…Then, the proximate analysis was carried out using a thermogravimetric analyzer (TGA), employing the method described by Shi, Liu, Guo, Wu, & Liu (2013). At the end of each experiment, residual mass was removed from the sample holder and determined using an analytic balance Mettler Toledo brand, XP205 model, with precision ±0,01 mg, with that the mass loss was calculated.…”

Section: Coals and Chars Samples Analysismentioning

confidence: 99%

Effects of pyrolysis atmosphere on the porous structure and reactivity of chars from middle and high rank coals

Valdés¹,

Guerrero²,

López³

et al. 2018

Ing. Inv.

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The influence of a CO 2 or N 2 -based atmosphere on the porous structure and microstructure of the chars obtained from the nonisothermal slow devolatilization (10 °C/min), from room temperature to 900 °C, of two coals of different rank (Semi-Anthracite (SA) and High Volatile Bituminous type C (HVBC)) and different particle size distribution was studied. Physicochemical characterization (ultimate and proximate analysis), structural and morphological characterization by Raman spectroscopy, FE-SEM, BET surface area, and volume and diameter microporous by CO 2 adsorption measurements were carried out for all the chars. It was found that the kinetic parameters, the physicochemical properties, and reactivity of the chars are different, depending on the pyrolysis atmosphere. It was also determined that for the char from SA coal with particle size greater than 0.7 mm, the BET surface area increases when the atmosphere is enriched with CO 2 . This effect appears to be promoted by the interaction of different processes such as intraparticle side reactions (softening, nucleation and coalescence of bubbles, crosslinking, among others), differences in the thermal diffusivity of N 2 and CO 2 , and the reactive effects of the latter. Additionally, tests of oxidative reactivity of chars showed that the char formed in a CO 2 atmosphere is more reactive than that formed in N 2 . With the results of Raman analysis and kinetic parameters quantified, it was concluded that the reaction atmosphere determined the degree of ordering achieved by the char structure and that the thermodiffusive properties of the reaction atmosphere promoted structural differences in the char even at low heating rates.Keywords: Slow pyrolysis, Pore size distribution, large coal particles, Oxy-combustion, reactivity. RESUMENSe estudió la influencia de una atmósfera basada en CO 2 o N 2 sobre la estructura porosa y la microestructura de carbonizados de carbón obtenidos de la pirólisis lenta no isotérmica desde temperatura ambiente hasta 900 °C de dos carbones de diferente rango (Semi-Antracita (SA) y Bituminosos Alto en Volátiles tipo C (BAVC)), y de diferentes distribuciones de tamaño de partícula. Para todos los carbonizados se realizó la caracterización fisicoquímica (Análisis ultimo y próximo), la caracterización morfológica y estructural por combinación de técnicas como espectroscopia Rama, Microscopia electrónica de barrido por emisión de campo (FE-SEM), área superficial (BET -Brunauer-Emmett-Teller) y volumen y diámetro de microporos por mediciones de adsorción en CO 2 (Horvath-Kawazoe (HK) method). Se encontró que los parámetros cinéticos, las propiedades fisicoquímicas y la reactividad de los carbonizados de carbón son diferentes dependiendo de la atmósfera de pirólisis. También se determinó que para el carbonizado de carbón de SA, con un tamaño de partícula mayor de 0,7 mm, la superficie BET aumenta cuando la atmósfera se enriquece en CO 2 . Este efecto parece ser promovido por la interacción de diferentes procesos como las reacciones secund...

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Pyrolysis behavior and bonding information of coal — A TGA study

Cited by 399 publications

References 40 publications

Structure-reactivity relationship in pyrolysis of plastics: A comparison with natural polymers

Structure-reactivity relationship in pyrolysis of plastics: A comparison with natural polymers

Effect of pH conditions on the depolymerization of Wucaiwan coal by mixed acids/ultrasound method and the product structures and performance

Effects of pyrolysis atmosphere on the porous structure and reactivity of chars from middle and high rank coals

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