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[Display omitted] • Two biomass wastes were subjected to comprehensive thermogravimetric analysis. • Both rice husk (RH) and poplar bark (PB) showed three consecutive pyrolysis stages. • CH 4 and arenes were abundant in the hydrocarbon gaseous products. • Average E a were 209.1 kJ/mol and 203.90 kJ/mol for RH and PB, respectively. • At low conversions, both RH and PB obeyed first-order reaction (F1) mechanism. Rice husk (RH) and poplar bark (PB) as the staple biomass wastes represent herbaceous and woody plants, respectively. Thermo-chemical conversion of these wastes is a practical approach for value-added reclamation of bioenergy in large-quantity and pyrolysis plays core role in this process. In this work, RH and PB were subjected to comprehensive investigations on pyrolysis behavior, kinetics and gaseous product evolution in a thermogravimetry-Fourier transform infrared spectroscopy at different heating rates. The results demonstrated that both RH and PB underwent three consecutive pyrolysis stages, the TG/DTG curves shifted to higher temperature and the peak temperature intervals also enhanced as heating rate increased. It was observed CO 2 was the most dominated species among oxygenated products, followed by C O bond containing species, while CH 4 and arenes were abundant in hydrocarbon gases. In comparison, pyrolysis of RH could generate larger amounts of oxygenated products, and more hydrocarbons like CH 4 , arenes, and C2+ aliphatics were observed in the pyrolytic products of PB. Model-free kinetic methods showed that the average E a were 209.1 kJ/mol and 203.9 kJ/mol for RH and PB, respectively. Criado model-fitting method indicated that pyrolysis of RH and PB both obeyed F1 reaction mechanism first and turned into one-dimensional diffusion and reaction mechanism, respectively at higher conversion of 0.25−0.60. [ABSTRACT FROM AUTHOR]

Volatile compositions of coals during fast pyrolysis are principally governed by their bond structures and establishing the relationships between them is vital for deep understanding the pyrolysis mechanism. The structural features and bond information of Jining bituminous coal (JBC) were evaluated first by the combined advanced analytical tools. Subsequently, thermogravimetry coupled with pyrolysis-gas chromatography/time of flight mass spectrometry analysis were used to capture pyrolysis behavior and volatile species of JBC. The results showed that C O bond containing species were rich in JBC and mainly in the form of aryl ethers. Therefore, phenolic compounds were the most abundant species in volatiles during fast pyrolysis and C 6 C 9 phenols were the major constituent of this group. Average number of aromatic rings per cluster, number of substituents on each aromatic ring, and length of methylene chain in JBC were 3, 3–4, and 1.36, respectively. However, the three parameters calculated from the aryl-containing species in volatiles were all smaller than those of JBC. Cleavages of C al O, C al C al , C ar C al , and C ar O greatly contributed to volatile release and 67% of the mass loss during pyrolysis of JBC was caused by breakage of aliphatic C C and C H. Furthermore, pyrrolic nitrogen was found to be the most abundant form of organically bound nitrogen, but the pyrolysis volatiles contained more pyridine-N. [ABSTRACT FROM AUTHOR]

Trapped small molecular phase is an important part in coal and strongly affects reactivity and volatile release during pyrolysis. In this work, it was separated by normal heptane leaching of extracts from thorough extraction of a lignite and was further fractionated into four sub-fractions by column chromatography. Chemical properties of each sub-fraction were evaluated first and then pyrolysis behavior, gaseous product evolution and kinetics of the raw coal and its four sub-fractions were systematically investigated using a thermogravimetric analyzer coupled with on-line Fourier Transform Infrared spectrometer. Determination results corresponding to the total yield and chemical properties of the sub-fractions proved the effectiveness of the separation procedure. Normal heptane eluate presented one mass loss stage and decomposition of aliphatic moieties in it mainly contributed to formation of methane, ethylene, and other high carbon number aliphatics. Toluene eluate exhibited one broad mass loss stage and produced largest quantities of light arenes and ether bond containing species, while two apparent mass losses occurred in pyrolysis profile of ethyl acetate eluate, during which ketonic bond containing species generated at the first pyrolysis stage. The formation of coke during pyrolysis was mainly caused by the presence of methanol eluate. Kinetic results revealed that distributed activation energy model was suitable for describing the pyrolysis process of raw coal and its four sub-fractions. Trapped small molecular phase could be easily pyrolyzed and the average bond energy of the components was in the order of raw coal ≫ ethyl acetate eluate > normal heptane eluate > toluene eluate > methanol eluate. In addition, the kinetic compensation effects were observed for almost the whole pyrolysis processes of both the raw coal and the four eluates. [ABSTRACT FROM AUTHOR]

Investigation on the properties of mobile phase in low rank coals and its pyrolysis characteristics is an alternative approach for understanding the pyrolysis mechanism and structure features of these coals. In this work, heat reflux extraction with cyclohexanone (CYC) was developed to dissolve the mobile phases in two low rank coals and afford one extract from Chifeng coal (E CF ) and another extract from Hami coal (E HM ). The structural features of the extracts were investigated using multiple analytical techniques first. Then, thermal reactivity and gaseous product evolution of the extracts, residues, and raw coals were evaluated by TG–FTIR. Detailed volatile specie composition during fast pyrolysis of extracts were further detected on the pyrolysis gas chromatography/time of flight mass spectrometer (Py–GC/TOF–MS). The results suggest that heat reflux extraction with CYC is an effective method for dissolving a fairly high fraction of the organic matters in low rank coals. Two low rank coals mainly showed one mass loss stage of devolatilization of the organic matters near 430 °C and large numbers of gaseous products were released such as hydrocarbons (CH 4 , C 2 H 4 , C 2+ aliphatics, and arenes), CO 2 , C O and C O bonds containing species, which were the result of the cracking and cleavage of the alkyl sides, strongly bonded functional groups, and bridged bonds, respectively. Forming of CO during pyrolysis of low rank coals was mainly derived from the cracking of the O-containing primary tar fragment and the condensation reactions of the aromatic clusters above 600 °C rather than from the initial cleavage of the organic structures in low rank coals. Thermal dissolution effect of CYC can depolymerize the macromolecular structure of raw coals and thereby the dissociated coal structures (residues) are beneficial to crack the alkyl side chains and break the O-containing structures at lower temperatures. Two extracts can be pyrolyzed at temperatures lower than that of their parent coals and large quantities of O-containing gaseous products and C 2+ aliphatics release during pyrolysis process. Furthermore, aliphatic hydrocarbons, arenes, ketones, phenols, and benzofurans are the most abundant species in the products during fast pyrolysis of both two extracts. Notably, the cleavage of C C bonds near the aromatic rings in longer-chain alkylbenzenes is a crucial reaction during fast pyrolysis of E CF and E HM . [ABSTRACT FROM AUTHOR]

The devolatilization characteristics, kinetics, and volatile-char interaction mechanism during co-pyrolysis of a bituminous coal (BC) and four kinds of biomass were deeply investigated by the integrated pyrolysis method to achieve new understanding of the pyrolysis synergy. The results showed that co-pyrolysis of BC and the biomass presented obvious synergy in the respects of volatile release, gas formation, pyrolysis kinetics, and char structure. Co-pyrolysis of BC and the biomass increased the maximum devolatilization rate and activated energy (E), but had no influence on initial and maximum devolatilization temperatures compared to individual pyrolysis below 380 °C. In addition, co-pyrolysis of BC and the biomass produced more C–O and C=O bearing compounds, but less CO, CH 4 and C 2 + aliphatics. Compared with the woody biomass, blending the two herbs in BC generated less CO 2 and arenes, but more porous structures in the chars. The study on the pyrolysis kinetics suggested that co-pyrolysis processes obeyed 1.5 order reaction mechanism and the synergy in terms of E was related to both biomass types and reaction temperatures. Furthermore, a new volatile-char interaction mechanism was proposed to interpret the existence of the external molecular interaction between BC volatiles and the bio-chars in the temperature range of 380–650 °C. [Display omitted] • Co-pyrolysis of coal and the biomass showed strong synergy. • The synergy was influenced by both biomass types and temperatures. • Blending the two herbs in coal reduced CO 2 and arene content. • The pyrolysis process basically obeyed chemical reaction model of 1.5 order. • A strong volatile-char interaction was observed in the range of 380–650 °C. [ABSTRACT FROM AUTHOR]

In this work, thermal behavior of five different coal particle fractions were investigated using thermogravimetric analyzer (TGA) under various heating rates with the maximum of 1000 K/min. An on–line Fourier Transform Infrared Spectrometry (FTIR) was employed to evaluate the evolution characteristics of the gaseous products. The results showed that the coal particle size remarkably affected the mass loss and the ash amount. The larger the particle size was, the higher mass loss and the more ash could be, which revealed its high pyrolysis reactivity. In addition, with increasing the particle size, the initial devolatilization temperature (T in ) and devolatilization index (D i ) increased, whereas, the final devolatilization temperature (T f ) decreased. This phenomenon was explained by a proposed mechanism of the obstacle escaping of volatiles from the interparticles corresponding to forming large block unit of metaplast. The heating rate has significant effect on the performance of devolatilization profiles and gaseous products releasing. T in , T max and T f displayed the logistic distribution along with heating rate up to 1000 K/min, whereas, R max and the heating rate were highly linear correlated with different particle fractions. The enhanced yield at maximum releasing rate for all the gas species were observed with increasing the heating rate. Moreover, the peak of maximum releasing rate on the evolving profiles of gaseous products became narrower and sharper, and releasing time of the gaseous products reduced extremely with increasing the heating rate. These findings can provide fundamental data for practical applications, plant designing, handling, and modeling of integrated coal fluidized bed gasification system as well as other coal fluidized bed pyrolysis/gasification process. [ABSTRACT FROM AUTHOR]

Catalytic fast pyrolysis is a prospective and effective route to produce value-added products from rice husk (RH). Understanding the volatile compositions and its formation pathways as well as kinetics during RH pyrolysis is crucial and fundamental to regulate the quality of the target products since catalysts interact directly with primary volatiles. In this study, two pyrolysis coupled real-time volatile monitoring techniques (TG-FTIR and Py-GC/TOF-MS) were employed to conduct comprehensive experiments for RH. The results showed that RH presented three mass loss and gaseous product evolution stages in the temperature range of 200 to 330 °C, 330 to 390 °C, and 390 to 600 °C, respectively. After speculating the formation pathways of the 24 main volatile species, it was indicated that 2,3-dihydro-benzofuran was the major product for hemicellulose, while 2-methoxy-4-(1-propenyl)-phenol was potentially a key active intermediate and very unstable during pyrolysis of lignin constituent in RH. In addition, pyrolysis of RH could be divided into two kinetic stages at cut-off point of 25% conversion. The first kinetic stage obeyed three-dimensional (D3) diffusion model and E a was within 140–170 kJ/mol. In the secondary kinetic stage, E a raised gradually to about 200 kJ/mol and pyrolysis reactions followed the second-order reaction model. • Rice husk was subjected to comprehensive pyrolysis experiments. • Both mass loss and gaseous product evolution contained three stages. • 2,3-dihydro-benzofuran was the major product for hemicellulose. • 2-methoxy-4-(1-propenyl)-phenol might be an important active intermediate. • E a was within 140–200 kJ/mol at the whole pyrolysis stage. [ABSTRACT FROM AUTHOR]

Highlights • TG experiments are operated at a heating rate of 100–500 °C/min. • High heating rates promote the occurrence of devolatilization reaction. • Fast pyrolysis is carried out at a heating rate of 100–3000 °C/s. • The content of aromatics is increasing at final temperature of 500–1000 °C. • The content of alkanes reaches the maximum (37.03%) under residence time of 1 s. Abstract The chemical properties, pyrolysis behaviors and pyrolysis product distributions of Shenmu (SM) coal were investigated by proximate and ultimate analysis, thermogravimetric analyzer coupled with Fourier transform infrared spectroscopy (TG-FTIR) and Pyrolyzer coupled with gas chromatography/mass spectrometry (Py-GC/MS). The results of the proximate and ultimate analysis indicated that SM coal had less saturated aliphatic structures and more polar components. The coke yield for SM coal during pyrolysis process at 100 °C/min, 300 °C/min, and 500 °C/min was 65.60%, 64.19%, and 63.15%, respectively, which indicating that the increment in heating rates could promote the production of volatile substances. Moreover, there was a lateral shift to high temperature of TG/DTG curves when the heating rates increasing. The main volatile species detected from FTIR in the pyrolysis of SM coal were CO 2 , CO, CH 4 , C 2 H 4 , C2+ aliphatics, light arenes, C O bond containing species and C O bond containing species. Since the difference in the temperature intervals of those volatile species released, the sources of cleavage or chain scission during pyrolysis process were not the same. According to the fast pyrolysis by Py GC/MS, the volatile species could be divided into eleven species including alkenes, cycloalkenes, alkanes, cycloalkanes, aromatics, phenols, ethers, ketones, alcohols, N-containing species, and other species. The relative contents of alkenes and alkanes were dominant regardless of the variegation of heating rate, residence time and pyrolysis final temperature. Furthermore, the trend of each species under different influence factor conditions achieved different tunes rendered with equal skill. [ABSTRACT FROM AUTHOR]

Studying pyrolysis behavior of saturate component is significant to understand the pyrolysis behaviors of coal, as the component can produce volatile matters. The combined utilization of TG-FTIR and Py-GC/MS provides a feasible strategy for investigating pyrolysis behaviors of saturate component. The results of TG-FTIR show that the pyrolysis of saturate component contains one stage. The yield of coal-char at different heating rates is quite low (0.04–0.50 wt%) and the values are close to each other, which indicates that the pyrolysis of saturate component has almost no coal-char and the saturate component mainly consists of volatile substances. Furthermore, the change in absorbance of typical compounds in FTIR indirectly reflects the variety in the content of compounds. The detailed information of pyrolysis products is analyzed by Py-GC/MS, which shows that alkanes and alkenes are dominant. Moreover, the change in the content of alkanes and alkenes is opposite. The pyrolysis mechanism of saturate component belongs to free radical reaction. The possible pyrolysis pathway of saturate component is presented and the appearance of hexane and hexene is also verified. This research provides a methodological model for exploring other group components and reveals more specific details for the pyrolysis of coal. • The pyrolysis of saturate component contains one stage and almost no coke is formed. • The delayed effect of heating rate on characteristic temperature weakens. • The releasing characteristics of volatiles is consistent with pyrolysis behavior. • Alkanes and alkenes are the main pyrolysis products of saturate component. • The pyrolysis mechanism of saturate component is free radical mechanism. [ABSTRACT FROM AUTHOR]

In this study, a typical inertinite- and AAEMs (alkali and alkaline earth metal species)-rich Chinese sub-bituminous coal was systematically investigated in terms of maceral component, mineral occurrence and molecular structure. Based on the experimental data, macromolecular-dependent evolutionary behavior during integrated cascade coal pyrolysis was unraveled, and further a mechanism on staged-pyrolysis was proposed. Compelling evidence shows that after heavy medium separation, the features of coal fractions with different densities were significantly varied in maceral compositions, AAEMs distributions and more importantly, in macromolecular structure. The various functional groups abundant in respective maceral-enriched (vitrinite, liptinite, and inertinite) coal fractions behaved distinctively during pyrolysis due to the different activation energies for the scission of these functional groups, thus resulting in temperature-dependent reactions. Specifically, at lower temperature (400–500 °C), carboxylic groups mainly inherent in vitrinite could be substantially decomposed into CO 2 . Subsequently, at ca. 500 °C, aliphatic chains in vitrinite were cracked to C 2 -C 4 ; while ether structures were broken and contributed to the generation of a small amount of CO. Meanwhile, the small aromatic molecules freely existed in liptinite could also be released in form of light aromatics. At higher temperature (ca. 700 °C), the volatiles including CO 2 would react with char and generate a larger proportion of CO; and particularly, this secondary reaction could be catalytically accelerated by AAEMs at higher temperature. Consequently, the pyrolysis route and gaseous products in different stages were varying in specific manner according to the reaction mechanism; and it was available to direct the production of methane-rich syngas, and provide a useful basis for optimization of cascade coal pyrolysis processes. [ABSTRACT FROM AUTHOR]