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• Heavy components in the condensed volatiles from amino acids pyrolysis were characterized. • Stable free radical intensity in char shows positive correlation with tar yields and heavy components average mass. • Heavy components from alanine were developed based polypeptide formation followed by dissociation of small groups. • Phenylalanine and tryptophan prefer to crack into radicals like C 8 H 7 N/C 12 H 10 N 2 ·and then recombine together. • Heavy components from the three amino acids all decreased above 550 °C, but the reasons are different. Heavy components, comprised of molecules with a substantial molecular mass, are essential constituents within volatiles. Within these molecules, nitrogen-containing compounds have a tendency to undergo transformation into coke during thermal treatment, exerting a substantial impact on the efficient and secure utilization of biomass. Three amino acids- alanine with an aliphatic structure, phenylalanine with additional aromatic features, and tryptophan with an extra heterocyclic ring were selected as model compounds, individually subjected to pyrolysis within the temperature range of 450 to 650 °C. The evolution of heavy components and the associated reaction mechanisms were comprehensively explored through extensive characterization and network analysis. The results showed that alanine transformed into heavy components mainly through dehydration followed by dissociation of CH 2 and CH. In contrast, phenylalanine and tryptophan tended to undergo fragmentation into C 8 H 7 N· and C 12 H 10 N 2 · derivatives, subsequently recombining to form heavy molecules. As the temperature increased, heavy components in alanine-derived volatiles monotonously decreased due to elimination reactions and the breaking of C–C bonds. Conversely, heavy components in phenylalanine and tryptophan initially increased and then decreased due to the enhanced cracked fragments, along with the competitive relationship between aromatization and polymerization reactions. For all three amino acids, there is a positive correlation among the average mass of heavy components, tar yield, and the intensity of permanent free radicals in the char. This implies that we may rapidly predict the evolutionary patterns of heavy components and tar through free radical detection. HCN dissociation is mathematically identified as a pivotal reaction in heavy component evolution, irrespective of amino acid type, possibly unveiling an important pathway for NOx formation. This study shows substantial theoretical significance for the eco-friendly and efficient conversion of nitrogen-rich biomass. [ABSTRACT FROM AUTHOR]

Co-combustion of sewage sludge (SS) and coal slime (CS) could improve the combustion properties of the two materials, however, high levels of trace elements (TEs) can be released from the two wastes, resulting in secondary pollution. The migration and transformation behavior of As, Cr, Pb, Zn, and Mn during co-combustion is explored in current research. The results showed co-combustion could inhibit the emission of Zn, As, Pb, and Mn, and the effect was more pronounced for Zn, As and Mn. Meanwhile, minerals like kaolinite and gypsum were found to generated in the ash from co-combustion but not solo-combustion. Model experiments demonstrated that kaolinite captured As, Pb and Mn, while gypsum captured Zn, As and Mn but facilitated the emission of Pb and Cr. This well explained the distinct TEs emission characteristics between co-combustion and solo combustion. As the temperature elevated, kaolinite in co-combustion ash decomposed and the generation of gypsum was promoted. In this way, the emission ratios of Zn, As, and Mn initially increased but subsequently decreased between 700 and 1300 °C, whereas Pb and Cr emission ratios increased by twofold within the same temperature range. Leaching characteristics and risk assessment code on co-combustion ashes were also conducted in this study. The results indicated a marginal elevation in the risk associated with trace elements (TEs) following co-combustion, provided that all five TEs remained within the limits of national standards. [Display omitted] • Kaolinite, gypsum and grossular were generated during sludge and coal slime co-combustion. • Gypsum inhibited Zn, As and Mn emissions but facilitated Pb and Cr emissions. • Kaolinite was demonstrated to inhibit As, Pb and Mn emissions during co-combustion. • The emission ratio of Zn, As, Mn increased and then decreased from 700 to 1300 °C. [ABSTRACT FROM AUTHOR]

Highlights • This study focuses on the evolution of heavy component of bio-oil during pyrolysis. • Temperature and heating rate influence the evolution of heavy components obviously. • O-containing species are prone to be enriched in the heavy components. • Polymerization of heavy components and breakage of O-species are simultaneous. • Molecular weight and O numbers of heavy components are not in linear relationship. Abstract The knowledge about the formation of the heavy tars of bio-oil during pyrolysis is of great importance for the further utilization of bio-oil. This work focuses on the formation of the heavy tars during pyrolysis of bio-oil at various temperatures and heating rates in a fixed-bed reactor. In order to investigate the detailed composition of the heavy tar, the bio-oil and tars were characterized with a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS). Our results indicate that low temperature promotes the formation of heavy tars via the polymerization of bio-oil components, especially at slow heating rates, therein the condensed aromatics are formed via the polymerization of small aromatics with one or two rings. High temperature promotes the breakage of the oxygen-containing functional groups, meanwhile the highly condensed aromatics with more than 4 rings are formed at 800 °C via the strong secondary reactions (e.g. recombination), especially at fast heating rates. [ABSTRACT FROM AUTHOR]

Heavy components affect conversion behaviors of sludge-derived pyrolytic liquids during their utilization and contribute significantly to the formation of the notorious tar and soot during sludge gasification and combustion. Understanding the evolution of heavy components during pyrolysis is vital for developing a reliable sewage sludge utilization technology. This study investigates the compositions of oils from the pyrolysis of sewage sludge using an electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT ICR-MS). Hundreds of compounds with molecular mass higher than 400 Da were detected from the pyrolytic oil obtained at 450 and 650 °C. Higher pyrolysis temperatures promoted decomposition and polycondensation of large molecules and increased the amount of nitrogen-containing compounds in the liquid. Aromatic structured molecules consisting of carbon, hydrogen and nitrogen were the predominant compounds at 850 °C. From the results of this study, the evolution routes of heavy components in the pyrolytic liquid are proposed. [ABSTRACT FROM AUTHOR]

Gas-pressurized torrefaction is efficient for upgrading biomass to substitute metallurgical coke. Herein, the effects of pressure and temperature on corncob torrefied products as well as the synergistic mechanism were investigated. The results indicated pressure facilitated secondary reactions that converted volatiles to fixed carbon. As the temperature increased to 280 °C from 180 °C under 3 MPa, the volatile content decreased from 82.72% to 48.71%, and the HHV improved from 16.14 MJ/kg to 28.60 MJ/kg, which were close to the quality of bituminous coal. Lignin was mixed with corncob to further improve the property of torrefied products. The fixed carbon of mixture semi-char increased by 11.28% compared to the theoretical value, the O/C and H/C ratios decreased to 0.18 and 0.74 respectively, reaching the quality of coking coal. The blending of lignin promoted the formation of water under subcritical conditions, accelerating biomass decomposition. Cross-interaction reactions among volatiles intensified the deoxygenation and more acetic acid was produced that promoted carbonization reactions, causing the removal of oxygen in the form of gas and a higher fixed carbon in the semi-char. The finding promoted biomass application in low-carbon iron production significantly by obtaining bio-coking coal. • The reaction mechanism of corncob under different conditions was studied. • A lignin-corncob mixture pressurized torrefaction method was proposed. • Higher fixed carbon and lower oxygen content was obtained due to a synergism. • This synergy facilitated decomposition, deoxygenation and aromatization reactions. • A substitute with similar fuel quality to coking coal feedstock was prepared. [ABSTRACT FROM AUTHOR]

Sewage sludge is an important class of bioresources whose energy content could be exploited using pyrolysis technology. However, some harmful trace elements in sewage sludge can escape easily to the gas phase during pyrolysis, increasing the potential of carcinogenic material emissions to the atmosphere. This study investigates emission characteristics of arsenic, cadmium and lead under different pyrolysis conditions for three different sewage sludge samples. The increased temperature (within 723–1123 K) significantly promoted the cadmium and lead emissions, but its influence on arsenic emission was not pronounced. The releasing rate order of the three trace elements is volatile arsenic compounds > cadmium > lead in the beginning of pyrolysis. Fast heating rates promoted the emission of trace elements for the sludge containing the highest amount of ash, but exhibited an opposite effect for other studied samples. Overall, the high ash sludge released the least trace elements almost under all reaction conditions. [ABSTRACT FROM AUTHOR]

This work aimed to investigate effects and reaction mechanisms of CaO/Fe 2 O 3 on emission behaviors of arsenic during sewage sludge pyrolysis. The results showed that 24.8–54.2%, 26.4–60.4% and 27.7–63.1% of arsenic escaped from three samples when pyrolysis process happened at 723, 923 and 1123 K respectively. And the sludge which contained higher calcium and iron contents released less arsenic than others. External CaO and Fe 2 O 3 were added into the sewage sludge to study their effects on arsenic emissions during pyrolysis, where both of them inhibited arsenic emission effectively, especially at high temperatures. With the help of thermogravimetry analysis and X-ray fluorescence, inhibitory mechanisms of CaO/Fe 2 O 3 on arsenic emission during sewage sludge pyrolysis were studied. CaO could react with As 2 O 3 , As 2 S 3 and NaAsO 2 to form nonvolatile substances, such as Ca(AsO 2 ) 2 ; while Fe 2 O 3 could react with NaAsO 2 to generate certain substances which was stable below 1123 K. [ABSTRACT FROM AUTHOR]

• The evolution of heavy volatile during cellulose steam reforming was revealed. • Heavy components were formed by polymerization accompanied with deoxygenation. • Steam simultaneously accelerated cracking and polymerization of heavy components. • KCl facilitated the generation of heavy phenols below 700℃. • Molecules below 300 Da significantly increased in the presence of KCl. Biomass sources could transform into green chemicals and energy through steam reforming but heavy components of the resulting volatile, which are the precursors of undesirable coke, would also be formed. In the current study, the evolution of heavy components from cellulose is investigated. The effects of an inorganic potassium salt KCl on the heavy component evolution during steam reforming are firstly revealed in the homogeneous steam-volatile reforming process. The results suggest that heavy components were formed by polymerization reactions accompanied with dehydration and decarboxylation. Steam and alkali metal both promoted the cracking and secondary polymerization of heavy components. In the presence of steam and alkali metal, the percentage of molecules with low weight (<250 Da) and high weight (>500 Da) both improved. KCl significantly promoted the polymerization of oxygen-containing compounds, increasing the average oxygen number of the heavy components by 1.4 to 2.2 times depending on the reaction temperatures. Heavy phenols are also promoted in the presence of alkali metal below 700℃. [ABSTRACT FROM AUTHOR]

Substituted polycyclic aromatic hydrocarbons released from sewage sludge pyrolysis bring the concern of the clean utilization for the waste. Herein, the roles of calcium oxide on the release of these compounds, especially the heavy ones containing nitrogen and oxygen atoms were investigated. The results showed that calcium oxide significantly decreased light substituted polycyclic aromatic hydrocarbons in the volatiles from 450 to 850 °C and showed obvious inhibitory effects on the formation of heavy substituted polycyclic aromatic hydrocarbons at 850 °C. To understand the impact mechanisms, pyrolysis experiments of sludge model compounds lipid, protein and polysaccharides were conducted. It was found that calcium oxide could catalyze or react with all three components to decrease the content of light substituted polycyclic aromatic hydrocarbons. Heavy oxygen-containing aromatics in sludge derived volatiles mainly resulted from polysaccharides and protein, and they considerably decreased after mixing with calcium oxide. Oxygen-containing aromatics content in the lipid derived volatiles, however, would increase due to polymerization reactions. The decreasing release of nitrogen substituted polycyclic aromatic hydrocarbons from sludge could be attributed to the synergy effects of CaO and other minerals or the effects of CaO on the interaction between protein and other organics. • CaO promoted the release of substituted PAHs at 450 °C but decreased that above 650 °C. • Oxygen substituted PAHs mainly derived from polysaccharide and protein. • CaO decreased oxygen substituted PAHs from polysaccharide and protein. • CaO promoted the generation of heavy oxygen substituted PAHs from lipid. • CaO increased heavy nitrogen substituted PAHs from protein. [ABSTRACT FROM AUTHOR]

Thermal treatments of sludge lead to the emission of carcinogenic aromatics, which has already attracted the attention of researchers for years. However, until now the evolution of substituted polycyclic aromatic hydrocarbons (PAHs), especially those with high molecular weight, during thermal treatments of sludge was not paid enough attention even though some of them are more toxic than their parent PAHs. To comprehend the generation of substituted PAHs, in particular that of heavy substituted PAHs, volatiles released from the pyrolysis of three sludge at three temperatures were comprehensively analyzed. The results show oxygen-substituted PAHs (O-PAHs) and nitrogen-substituted PAHs (N-PAHs) are the most abundant light substituted PAHs at 450 °C, while PAHs containing both nitrogen and oxygen atoms (NO-PAHs) and O-PAHs are the dominant substituted aromatics in heavy components. With the temperature increased, condensation degree and content of substituted PAHs in light and heavy components both increase due to condensation effect. Deamination and deoxygenation of NO-PAHs also enhance content of O-PAHs and N-PAHs, respectively. At 850 °C, nearly all heavy components derive from the condensation of light molecules instead of the direct decomposition of sludge. Aromatics, especially N-PAHs, are the dominant compounds in both light and heavy components. Calcium compounds in sludge can greatly affect the formation of substituted PAHs at high temperatures. • NO-PAHs are abundant in both light and heavy components in oils at 450 °C. • Substituted PAHs result from incomplete cracking of sludge at 450 °C. • Heavy O-PAHs reached peaks at 650 °C while heavy N-PAHs reached peaks at 850 °C. • The largest aromatic ring numbers of N-PAHs and O/NO-PAHs can be 9 and 11. • Light S-PAHs only released at 850 °C from sludge with high content of Ca and Fe. [ABSTRACT FROM AUTHOR]

[Display omitted] • Quick measurement method of three components was established based on PT-TGA. • The method can be applicated with high heating rates up to 300 °C/min. • The time for three-component content measuring test can be as short as 3 min. • Maximum deviation of relative contents of three components was less than 3.32%. Cellulose, hemicellulose, and lignin are the major components of lignocellulosic biomass, and fast and accurate measurement of the three components' content is beneficial for the efficient application of biomass. However, the current chemical dissolution and titration method was tedious and time-consuming. In this study, a quick determination method of three components in biomass was developed for determining their contents based on a photo-thermal thermo-gravimetric analyzer (PT-TGA). Cellulose was modeled using a single F1 model, while hemicellulose and lignin were fitted with two consecutive processes according to their pyrolysis characteristic with F2 and F1 models. Using the kinetic parameters obtained from the fast pyrolysis of cellulose, hemicellulose and lignin on the PT-TGA, the contents of the three components in biomass samples were calculated by fitting the DTG curves with different peaks. Under the heating rate of 300 °C /min, the relative content deviation of the three components of rice straw was less than 2.00 % with the measurement time within 3 min. Furthermore, coconut shell and pine were used to verify that the maximum difference determined by the kinetic fitting method and the chemical method was only 3.32 %, demonstrating that the method could reliably and rapidly measure the contents of the three components in lignocellulosic biomass. This study provided a fast and effective method for determining the relative content of biomass components. [ABSTRACT FROM AUTHOR]

This study focused on the interaction between organic solid waste (OSW) components on the formation and chemical composition of heavy components (>150 m / z) in OSW-oil. Rice husk (RH) and polypropylene (PP) as typical biomass and plastic fractions in OSW, were co-pyrolyzed at different blend ratios and different temperatures. The heavy components were characterized by FT-ICR MS, UV-F and GC MS. The results indicated that the yield of heavy components in PP-oil was higher than in RH-oil under the same temperature. Heavy hydrocarbons were found in PP-oil, while heavy phenols and heavy lipids existed in RH-oil. Significant interactions occurred at high temperatures (>600 °C). The interactions promoted the heavy components in all the blend-oils, corresponding to an increase of 20–35% compared to the calculated value of the content in PP-oil and RH-oil. At low PP ratio (25PP + 75RH), PP provided hydrogen to the reactive O-containing species in RH, leading to promoted heavy phenols and heavy lipids. At high PP ratio (50PP + 50RH and 75PP + 25RH), large aromatics (>3 rings) increased of 48–111% with respect to the calculated values. Plenty of PP‑hydrogen and a rich oxygen environment provided by RH radicals enhanced the formation of heavy aromatics and heavy PAH. • Interactions between OSW components affect the formation of heavy components in the oil. • Temperature and blending ratio change the interaction effects on the heavy component formation. • Hydrogen provided by PP enhanced the recombination of heavy O-containing species. • Rich oxygen environment provided by RH enhanced the formation of heavy PAH. [ABSTRACT FROM AUTHOR]

• Lignin tar components were detailedly characterized via FT-ICR MS measurement. • Experimental results and theoretical calculation were significantly combined. • The formation of two typical OPAH and SPAH during lignin pyrolysis were revealed. OPAHs and SPAHs are highly genotoxic and would largely be formed during the thermal conversion of lignin. Herein, the distribution of OPAHs and SPAHs in lignin pyrolytic tar at different temperatures is elaborated with ESI (-) FT-ICR MS and GC–MS, and the formation routes of two typical OPAH and SPAH are deeply explored via DFT. It is found that most of oxygen-containing compounds convert to phenols and their homologues such as guaiacol (a typical precursor of OPAHs) with the temperature increased. The tar prepared at high temperature contains disulfide, thiophene and thiophene homologues, which are typical precursors of SPAHs. FT-ICR-MS strongly suggests that molecular mass of OPAHs and SPAHs compounds mainly concentrates between 200 Da and 400 Da with carbon atom number from 5 to 25 and DBE from 4 to 15. Higher temperature significantly promotes deoxygenation reaction since weighted average carbon atom number and DBE of molecules increase 28.4 % and 12.9 %, while the corresponding weighted average oxygen atom number decreases from 7.21 to 5.96 with temperature rising from 500 ℃ to 900 ℃. Incorporating with DFT calculation, the pathways of OPAHs and SPAHs during lignin pyrolysis at high temperature are concluded: Guaiacol converts to 1-methoxynaphthalene via 4 methylation reactions, and butene firstly generates thiophene and then converts to methyl-benzothiophene. Among the reactions above, benzene ring and thiophene ring generation steps possess the highest energy barriers (436.74 kJ/mol and 446.33 kJ/mol), further illustrating higher temperature promotes the formation of OPAHs and SPAHs. [ABSTRACT FROM AUTHOR]

Heavy components (molecular weight > 200 Da) in bio-oil affect the thermal conversion of bio-oil significantly. The inherent alkali/alkaline earth metal species (AAEMs) in biomass affect the formation of heavy components in bio-oil due to its catalytic effects. In order to investigate the effects of AAEMs on the formation of heavy components in bio-oil during biomass pyrolysis, the heavy components in bio-oil were characterized with the Fourier transform ion cyclotron resonance mass (FT-ICR MS) spectrometer and the ultraviolet fluorescence (UV-F) spectroscopy. The roles of K and Ca were also investigated. The results showed that AAEMs promoted the breakage of active oxygen-containing functional groups in heavy phenolics and inhibited their formation during pyrolysis, as well as the formation of heavy carbohydrates. The total content of heavy components decreased due to the catalytic effects of AAEMs. The catalytic effects of K on the decomposition of large molecular weight compounds (> 500 Da) in heavy components were stronger than those of Ca. K increased the content of single ring aromatic components in bio-oil for 1.5 times, while Ca decreased the content of the 2–3 rings aromatic components in bio-oil for more than 50%, compared to the bio-oil generated from the pyrolysis without AAEMs. • AAEMs inhibit the formation of heavy components in bio-oil during pyrolysis. • AAEMs promote the breakage of O-containing structures of heavy components. • Ca promotes formation of heavy lipids and inhibits formation of heavy sugars. • Both Ca and K can inhibit formation of pyrolysis lignin in heavy components. [ABSTRACT FROM AUTHOR]

Photo-thermal (PT) pyrolysis has emerged as a promising technique for efficiently converting biomass into high-quality bio-oil. The pyrolysis characteristics of rice straw (RS) and rapeseed cake (RC) were analyzed using a photo-thermal reactor with heating rates of 20, 200 and 500 °C/min and compared with 20 °C/min fixed-bed (FB) pyrolysis at 750 °C. Due to the uneven temperature distribution caused by its limited heating area, fast PT heating significantly increased the presence of high molecular weight components (>650) in the bio-oil. PT pyrolysis of RS exhibited higher phenolic contents compared to FB pyrolysis, whereas RC oil showed enhanced decomposition of fatty acids through ketonization. In terms of N-compounds, PT slow pyrolysis oil contained more nitriles but fewer linear amines/amides than FB, while more cyclic amides were formed under fast PT pyrolysis. Furthermore, the analysis of heavy components revealed that more aromatic compounds with low H/C ratios were produced in fast PT pyrolysis oil. Overall, PT heating exerted dual effects by reducing secondary reactions and synergistically enhancing inner-particle reactions with fast heating. This study provides valuable insights into the mechanism of bio-oil evolution under PT pyrolysis. [Display omitted] • PT pyrolysis produces bio-oil with more MW > 650 components. • Phenols in RS oil reach 33.2% in fast PT pyrolysis, but only 19.4% in fixed-bed. • PT pyrolysis benefits the fatty acids decomposition to ketones in RC oil. • Nitriles and lactams are promoted in RC slow and fast PT pyrolysis respectively. • Fast PT pyrolysis enhances the aromaticity of the heavy components. [ABSTRACT FROM AUTHOR]

Co-combustion of biomass offers a great potential to reduce CO 2 emissions but rarely mentioned co-combustion behavior of pelletized coal-biomass mixtures and inconclusive results based on single determinants formed obstacle for industrial application. In this study, ignition and flame characteristics, reaction and kinetic parameters and pollutant generation path were comprehensively investigated. Intrinsic combustion experiments were carried with the gas phase maintaining at room temperature in a concentrating photothermal reactor at heating rate over 200 °C/s. Same "homogeneous" ignition was evidenced while advanced devolatilization but more intense slagging behaviors were identified with the increase of biomass proportion. With the biomass proportion increased from 0% to 40%, the activation energies during devolatilization to ignition decreased non-linearly from 47.44 kJ/mol to 8.03 kJ/mol, indicating the existence of synergistic effect. CO exhibited relative high generation rates and the generation rate increased with the biomass content. Three fitted CO peaks were identified during co-combustion, which were contributed by devolatilization of coal and biomass, and combustion of char, respectively. First increased and then decreased NO emission with the increase of biomass proportion was evidenced for the higher N content in biomass but enhanced reduction by char and NH radicals with higher biomass proportion. • Co-combustion behaviors (ignition, slagging, kinetic and pollutant) were studied • The Ea decreased non-linearly from 47.44 kJ/mol to 8.03 kJ/mol with biomass addition • CO exhibited high intrinsic generation rate and biomass formed an independent CO peak • Biomass enhanced primary fuel-N emission and NO reduction by char and NH radical • Synthetic effects were proved by combustion characteristics and kinetic analysis [ABSTRACT FROM AUTHOR]

Co-pyrolysis of lignocellulosic biomass (LCB) with plastic has gained significant attention recently. Studying the pyrolysis kinetic behavior of LCB and plastic is beneficial for developing a framework for designing and improving biofuel production. The co-pyrolysis behavior, synergistic interactions and kinetic triplet parameters of the three main LCB components, i.e., cellulose, hemicellulose and lignin, and two plastics (polyethylene terephthalate [PET] and polyvinyl chloride [PVC]) were evaluated using a fast heating concentrating photothermal TGA system. The maximum decrease in mass loss rate with increasing heating rates was observed for cellulose with PET (1.23–0.94%/°C) and with PVC (1.05–0.62%/°C). The mechanism of synergistic interaction between hemicellulose and PET proceeded with polymer degradation and conversions of monomer units into excess volatiles in the higher heating rate regime. Distributed Activation Energy Model [DAEM] and Coats-Redfern [CR]) were used to calculate the kinetic parameters. DAEM results confirmed that mixed samples required lower activation energy to start the reaction. Using the CR method, the first degradation phase showed the best synergistic effect for lowering the PET and PVC activation energy, particularly with hemicellulose and lignin. [Display omitted] [ABSTRACT FROM AUTHOR]

Coal with a high moisture content is increasingly being utilized in power generation. However, the influence of moisture on coal ignition and soot generation characteristics remains unclear. Understanding the effect of moisture on coal ignition and soot generation characteristics is important for improving energy efficiency in coal utilization. The characteristics of soot generation and ignition of lignite coal including different contents of moisture (0%, 5%, 10%, 15%) were studied with Planar Laser Induced Fluorescence of OH radicals (OH-PLIF) on a novel concentrating photothermal platform. The results showed that the ignition delay time (t ign) of coal and observed soot generation during volatile combustion by the observation of flame luminosity both increased as the moisture content of the coal particles increased from 0% to 15%. The observed increase in t ign corresponded to the decreased OH intensity during the ignition. Similarly, the increased generation of soot during volatile combustion corresponded to the increased OH intensity resulting from increased moisture content in the coal. Before ignition, the steam surrounding the coal particle inhibits the release of volatiles. Thus, the formation of fuel molecules (RH) is reduced. Simultaneously, the inhibitory effect of moisture on RH leads to a decrease in H atoms, which further results in a decline in OH radical concentration resulting from the reaction H + O 2 → OH + O. The combined effect of reduced RH and OH concentrations inhibits ignition for coals containing moisture. During volatile combustion, although OH is commonly acknowledged as the primary oxidant for soot, the increase in OH facilitates gasification reactions, thereby promoting the massive release of volatiles. These volatiles, through processes such as nucleation reactions, contribute to the formation of an increased amount of soot, consequently resulting in an elevated formation of soot in coal with higher moisture content. • Ignition delay increases with decreasing OH intensity at 0%-5 wt% coal moisture. • Soot formation rises as increased coal moisture and OH during volatile combustion. • Mechanisms of ignition and soot generation in varied coal moisture was proposed. [ABSTRACT FROM AUTHOR]

Abstract Oxygenated polycyclic aromatic hydrocarbons (OPAHs) are an important group of components produced from the thermal conversion of cellulose. Through using gas chromatography mass spectrometry (GC–MS), Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) and ultraviolet fluorescence spectroscopy (UV-F), the information for the evolution of OPAHs is obtained in this study. The tar produced at low temperature mainly contains light components such as homologues of pyran and furan, while the components in the tars at 700 °C and 900 °C show high double bond equivalent (DBE) values, indicating the existence of large aromatic structures. High temperature promote condensation reactions during cellulose thermal conversion, thus leading to a higher percentage of OPAHs in the tar at higher temperature process. According to Density Functional Theory (DFT) calculation, the energy barrier of Diels-Alder reaction (302.65 kJ/mol) is lower than the dehydration (583.26 kJ/mol), which means that Diels-Alder reaction could be the main route for OPAH formation rather than dehydration reaction. High reaction temperature is calculated to be favorable for the formation of naphthol during the cellulose thermal conversion because of the high energy barrier of dehydration between phenol and furan. It is consistent with the ESI FT-ICR MS result that there is a higher content of naphthol in the tar at 700 °C than that at 500 °C. [ABSTRACT FROM AUTHOR]

The effects of catalyst supports (γ-Al 2 O 3 and α-Al 2 O 3 ) on hydrogen yield and carbon nanotubes formation were studied during steam reforming of toluene over Ni-based catalysts. Hydrogen yield and CNTs quality over Ni/γ-Al 2 O 3 were better than those over Ni/α-Al 2 O 3 at S/C ratio of 1 due to the high Ni dispersion of Ni/γ-Al 2 O 3 . With the increasing of steam addition, CNTs production remarkably increased over Ni/α-Al 2 O 3 , while it decreased over Ni/γ-Al 2 O 3 . The CNTs on Ni/γ-Al 2 O 3 were corroded at S/C ratio of 3 by excess steam. Toluene conversion and hydrogen yield over Ni/α-Al 2 O 3 were significantly larger than those over Ni/γ-Al 2 O 3 , which was attributed to the different effects of CNTs on catalytic activity. The strong interaction between Ni particle and γ-Al 2 O 3 led to the base-growth mechanism of CNTs on Ni/γ-Al 2 O 3 in which Ni particles located at the bottom of CNTs, thus the growth of CNTs covered Ni active sites and decreased catalytic activity of Ni/γ-Al 2 O 3 . By contrast, owing to weak interaction, CNTs grown on Ni/α-Al 2 O 3 followed tip-growth mechanism that would increase Ni dispersion and promote reforming reaction. [ABSTRACT FROM AUTHOR]

Bio-oil from the fast pyrolysis of biomass can be converted to solid carbon materials, chemicals and syngas by various thermochemical conversion methods. As a first step in all of these processes, bio-oil undergoes drastic components changes due to its exposure to the elevated temperature. Understanding the effects of heating rate on bio-oil transformation during its pyrolysis is therefore crucial for effective utilization of bio-oil. In this study, a bio-oil sample produced from the fast pyrolysis of rice husk at 500 °C was pyrolyzed in a fixed-bed reactor at temperatures between 300 and 800 °C at three different heating rates: fast (≈200 °C/s), medium (≈20 °C/s), and slow (≈0.33 °C/s). In addition to the quantification of coke and tar yields, the tar was characterized with an ultraviolet (UV) fluorescence spectroscopy, a gas chromatography/mass spectrometer (GC/MS) and a Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS). Our results indicate that slow heating rates promote polymerization of bio-oil components, particularly at low temperatures (<500 °C), resulting in higher primary coke yields than that of the fast heating rates. Decomposition reaction was found to be pronounced at fast heating rates, causing decreases in the tar yields and abundance of light compounds. The increases in the yields of the secondary coke, the formations of more condensed aromatic structures and macromolecules ( m / z  > 500) were also promoted at fast heating rates via the more intense secondary reactions. [ABSTRACT FROM AUTHOR]

Four types of biomass-derived organics (toluene/1-methylnaphthalene/phenol/ethanol) were catalytically decomposed and steam reformed over Ni/α-Al 2 O 3 for co-production of hydrogen and carbon nanotubes (CNTs). In the decomposition reaction, the oxygen functional group in phenol and ethanol promoted the co-production of hydrogen and CNTs, while a small amount of toluene and 1-methylnaphthalene were cracked to hydrogen and amorphous carbon. In the reforming reaction, the yields of hydrogen and CNTs sharply increased. More than 2000 mmol/(g-cata∗h) of H 2 and 260 mg/(g-cata∗h) of CNTs were produced after the reforming of toluene and ethanol. However, 1-methylnaphthalene was difficult to be reformed and small amount of CNTs were formed. The organics with low molecular weight and low degree of unsaturation conduced to the formation of hydrogen and CNTs. The growth of CNTs on Ni/α-Al 2 O 3 mainly follows the tip-growth mechanism. The diameter distribution of CNTs is not only influenced by Ni particle size, but also related to the different organics and steam addition. [ABSTRACT FROM AUTHOR]

• Interaction between the sewage sludge and coal slime during their co-combustion was found. • SO 2 formation and release mechanism during co-combustion of sewage sludge and coal slime was revealed. • AAEMs play a key role on the evolution of S-functional groups. The production of sewage sludge (SS) and coal slime (CS) is increasing year by year, which affects the ecological environment and human daily life, and it is urgent to deal with them reasonably. This study investigated the SO 2 release characteristics and the evolution of S functional groups and minerals during the combustion of SS, CS and their blends. The results showed that the co-combustion of SS and CS had an interaction on desulfurization. When the temperature was 800 ℃ and the blend ratio of SS was 20%, it was most beneficial to suppress the emission of SO 2. The types of S functional groups in SS and CS were similar but the relative content was different. The evolution of some S functional groups showed various laws. In the early stage of co-combustion, Sulfate (S1) reached maximum value earlier and decreased at the end of co-combustion, and Sulfide (S5) were more likely to be converted to aromatic-S (S4). According to XRD and SEM-EDS results, Ca (mainly CaCO 3) in the fuels had a significant effect on SO 2 release characteristics during the co-combustion. CaO formed by thermal decomposition of CaCO 3 could react with SO 2 to form intermediate solid products (CaS and CaSO 3). These intermediates further reacted with O 2 to generate CaSO 4 , thus retaining SO 2 in the ash. Some CaSO 4 was decomposed in the later stage of combustion, leading the re-release of SO 2. Excessive combustion temperature and reductive gases would lead to the decomposition of CaSO 4 , which reduced the ability of Ca to absorb SO 2. [ABSTRACT FROM AUTHOR]

The devolatilization and volatile combustion of lignite coal (LC), sub-bituminous coal (SBC) and bituminous coal (BC) with different O 2 concentrations (21%-50%) were investigated on a concentrating photothermal experiment platform. The characteristics and mechanism of different coal particle combustion were analyzed by using multiple diagnostics, including Planar Laser Induced Fluorescence (PLIF) of OH radicals and polycyclic aromatic hydrocarbons (PAHs), high-speed cinematography and FT-IR. The results showed that, with increasing O 2 concentration, the ignition delay time (t ign) of different ranks of coal decreased, which was associated with the increase of OH concentrations during the ignition stage. The good correlation between t ign and OH concentration was observed. For the volatile combustion, the OH concentration, volatile release amount and volatile flame duration time (t vol) significantly increased with the increasing of O 2 concentration at low O 2 concentrations. In the higher O 2 concentrations, coals with different PAHs generation amount responded differently on the increasing of O 2 concentration. On one hand, for the coals with lower PAHs generation amount, the OH concentration increased with the increasing of O 2 concentration, while the t vol was not sensitive to changes of the O 2 concentration. On the other hand, for the coals with higher PAHs generation amount, the OH concentration decreased with the increasing of O 2 concentration while the t vol increased with the increasing of O 2 concentration. It can be concluded that PAHs inhibited the OH generation, and the generation characteristics of OH and PAHs affected the sustained state of volatile combustion. The higher PAHs concentration consumed higher amount of OH during the volatile combustion. Meanwhile, with the increasing of PAHs concentration, the reaction rate of H + O 2 +M → HO 2 +M in which PAHs participate was increased, inhibiting the reaction H + O 2 → OH+O , and the increasing of polymer soot of PAHs will reduce the flame temperature through thermal radiation, which further inhibited the OH formation. [ABSTRACT FROM AUTHOR]

This work aimed to evaluate the detailed chemical structures of the asphaltenes in the tetrahydrofuran-microwave-extracted portions from two Chinese coals, namely, Shenfu and Zhundong coal (SF, ZD) and to clarify their characteristics on chemical composition at molecular level. Based on the analyses of diffuse reflectance Fourier transform infrared spectroscopy (DRIFT) and Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS), the detailed chemical structure of a series of basic and non-basic nitrogen- and oxygen-containing class species in the asphaltenes were clarified. The results revealed that condensed nitrogen-containing alkylaromatic structures with amidogens (1–3) were the main structure units in N 4 O y (y = 0–2) class species due to the high double bond equivalent (DBE) values for both the asphaltene from SF (A SF ) and the asphaltene from ZD (A ZD ). Acidic O 2 –O 7 class species with two or three aromatic rings were the main structure units, among which O 4 and O 2 class species had the highest relative abundances (RAs) in A SF and A ZD , respectively. Acidic oxygen-containing components in A ZD had narrower range of DBE and carbon number and mainly consisted of aromatic structure units with two rings. On the contrary, the average DBE values of O 4 –O 7 class species in A SF had positive relationship with oxygen atom number which could be attributed to the introduction of phenol groups. The results provided more detailed information on the structural characteristics of polar and aromatic-rich components of mobile phase in coal. [ABSTRACT FROM AUTHOR]

[Display omitted] • Double-green of purifying electroplating Ni wastewater and producing H 2 was realized. • Surface complexation and ions exchange mechanisms of biochar promoted Ni2+ removal. • The recycled Ni on biochar increased the H 2 yield by 15 times. • Two-step activation of steam and H 2 greatly improved double-green performance. • Steam activation increased surface area, Ni dispersion and surface Ni amount. The new method of using biochar to purify nickel-simulated electroplating wastewater and subsequent preparation of a Ni-based catalyst to produce H 2 in bio-oil reforming reaction is proposed. This process aims to realize the double-green of wastewater treatment and H 2 production. Different types of biochar (rice straw, rice husk and cotton stalk) were used. The results indicated that rice straw char (RSC) performed the highest Ni2+ removal efficiency due to ash components' high ion exchange capacity and high complexation ability of oxygen-containing functional groups. Then the adsorbed RSC was reduced and recycled to prepare Ni/RSC catalyst. Compared with the unadsorbed RSC, the recycled metal Ni remarkably improved the catalytic activity. The average carbon conversion of acetic acid at 600 °C was increased to 76.26% and H 2 yield was increased by 15 times. To further enhance the double-green performance, a two-step activation process was implemented. The biochar was firstly corroded by steam addition (5%, 15% and 25%) and then the adsorbed biochar was reduced by H 2. After that, the surface area, oxygen-containing functional groups and exchangeable cations of biochar were remarkably enhanced, which increased the Ni removal efficiency to reach 100%. Besides, the formed metal Ni with the higher metal dispersion and smaller Ni particle size improved the reforming of acetic acid. The activation by adding 25% steam further improved carbon conversion by 13.34% and H 2 yield by 60.47%. [ABSTRACT FROM AUTHOR]

Pyrolysis has been demonstrated to be promising for the conversion of coal slime (CS) to fuels and high value-added chemicals, which could achieve resource utilization of CS. For the in-depth understanding of the pyrolysis mechanism of CS, in this study, the pyrolysis kinetics and pyrolytic products distribution were investigated by TG-FTIR and Py-GC/MS and compared with those of raw coal (RC). The results demonstrated that the pyrolysis of CS comprises three reaction stages, with the decomposition of volatiles as the main stage (180–680 °C). Using the master plot method, the pyrolysis kinetic mechanism of RC and CS were predicted to be f(α) = (1 – α)4.6 and f(α) = (1 – α)5.4, respectively. The enrichment of inorganic minerals significantly increased the order of the CS pyrolysis reaction, indicating that minerals play an important role in the pyrolysis chemical reaction. Compared to that of RC, the alkene content of CS pyrolysis products decreased significantly, while the contents of CO 2 and aromatics increased, indicating that the minerals in CS promote the polymerization and cyclization of alkene, as well as the formation of macrocyclic aromatic hydrocarbons in CS tar. Those consequences also determined that inorganic matter in CS considerably affects pyrolysis, which in turn affects the whole pyrolysis process and tar quality. Therefore, in this study, theoretical and practical guidance on the efficient thermochemical conversion and utilization of CS is provided. • RC and CS were comparatively pyrolized. • Minerals in ash enhance kinetics resulting in higher reaction order. • CS rich in AAEMs promoted the formation of phenol and alcohol. • Tar precursors prefer to form larger PAHs by high ash content from CS. [ABSTRACT FROM AUTHOR]

As a typical solid municipal waste, waste tire (WT) needs to be efficiently treated for high-value utilization due to its large production capacity. ZnCl 2 –KOH heat treatment method was developed to treat WT to prepare high-yield sulfur-doped porous char. The treatment effect was the best when the additive mass ratios of ZnCl 2 /WT and KOH/WT were both 1, every g WT produces capacitance of 25.7 F/g WT (much higher than 9.2 F/g WT of pyrolysis and K 2 FeO 4 -activation). The effects of different ratios of ZnCl 2 /WT were found: For the activated char structures, more ZnCl 2 /WT decreased micropores, smaller pores turned to larger when the ratio increased from 1/3 to 1 and larger pores formed with some pores blocking as it further rose to 3 for mesopores + macropores; higher ratio (<1) resulted in more graphitic microcrystals, further increased ratio generated aromatic rings; 1 time of ZnCl 2 /WT promoted formations of both sulphide and sulphone bridges most powerfully. The roles of ZnCl 2 and KOH in pyrolysis and activation processes were revealed: During pyrolysis process, ZnCl 2 promoted polymerization reactions, huge generation of pores, disordered carbon skeleton structures turned to graphitic microcrystals. During activation process, ZnCl 2 inhibited the oxidation reactions of KOH on char, promoted formations of mesopores + macropores, converted inorganic sulfur to doped sulfur, weakened the reactions between KOH and doped sulfur. [Display omitted] • A novel ZnCl 2 –KOH heat treatment method was developed to treat waste tire. • High-yield sulfur-doped char with competitive specific capacitance was acquired. • Effects of ZnCl 2 additive ratio on char yield and specific capacitance were found. • Key roles of ZnCl 2 and KOH in pyrolysis and activation processes were revealed. [ABSTRACT FROM AUTHOR]

The electrochemical method is becoming a promising approach to deliver the bio-oil upgrading objective at room temperature. However, it still faces the coke formation issue because of the easy polymerization nature of bio-oil. Interactions among components impact the polymerization during the electrochemical upgrading of bio-oil. This study investigates the effects of interactions between the aromatic-rich and aromatic-poor fractions (ARFs and APFs) of the bio-oil on polymerization under various reaction time and current densities. Coke yield differences provide direct evidence of the existence of interactions between ARFs and APFs during the electrochemical upgrading process. Our results indicate that the coke yields and its condensation level are decreased by the interactions. The surface area, pore volume and the functionalities content of the coke are increased by the interactions. In addition to polymerization, more types of reactions including hydrogenation and esterification are induced by the interactions, resulting in more types of products and less coke. The interactions can inhibit polymerization by consuming the coke precursors before their condensation. The interactions can also inhibit the anodic adsorption and oxidation, thus depressing polymerization and coke formation. Investigating the impacts of interactions between aromatic-rich and aromatic-poor fractions on polymerization of bio-oil in chronoamperometric electrochemical upgrading. [Display omitted] • Interactions of aromatic-rich and -poor fractions in bio-oil is proven existed in electrolysis. • Aromatic-poor fractions end-cap the reactive chains of polymerization precursors. • Interactions weaken the anodic adsorption and polymerization of bio-oil. • Interactions decrease the yields, surface areas and pore volumes of the coke. [ABSTRACT FROM AUTHOR]

• Inorganic sodium inhibits coal combustion in early stage under fast-heating rate. • Ignition delay time of NaCl-loaded coal increases visibly under fast-heating rate. • Evolution pathways of condensation reactions catalyzed by Na are studied by DFT. • Na in studied coal reduces energy barrier of condensation reactions in early stage. The combustion characteristics of raw (RAW), acid-washed (AW) and inorganic sodium impregnated (NaCl-loaded) Zhundong (ZD) coals were researched in a fast-heating rate combustion system and thermal gravimetric (TG) analyzer, aiming to exhibit the effect of inorganic sodium on coal combustion processes under different heating rates. The results showed that the ignition delay time decreased in the order: NaCl-loaded coal > AW coal > RAW coal in the early stage with fast-heating rate. The surface temperature of NaCl-loaded coal increased the slowest, while with the highest T is , reflecting that the ignition and combustion behavior became more difficult after adding NaCl in the early stage. However, in the later stage, the fastest increase in temperature and the shortest t b , together with the shorter extinction time of volatile flame, were observed on NaCl-loaded coal. The size of NaCl-loaded coal decreased faster than that of AW coal. Thus, it can be concluded that inorganic sodium will inhibit coal combustion in the early stage, while promotes coal combustion in the later stage under fast-heating rate. In the TG experiment, the T i-TG and T b-TG of NaCl-loaded coal were lower than that of AW coal, and the T m-TG of NaCl-loaded coal moved to the low temperature area, revealing that inorganic sodium can promote coal combustion with low-heating rate during the whole combustion process. The quantum chemistry calculation at M06-2X/6-31G(d,p)//CBS-QB3 level reveals that inorganic sodium can catalyze the addition and cyclization reactions of small chain molecules in the early stage with fast-heating rate, thereby inhibiting coal combustion in the early stage, which was different from that in the later stage. Inorganic sodium will promote the formation of OH radical, and the organic sodium obtained from sodium-containing surface compounds of the char can be beneficial for the oxidation reaction of the carbon residue, thereby promoting coal combustion in the later stage with fast-heating rate, which was consistent with the references. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bio-oil from biomass with a small particle size can generate more gases. • Bio-oil produced with maximum is not suitable for syngas production. • Bio-oil with high oligomers produces more tar and aromatic molecular structures. • Organic fraction of bio-oil determines the gas yield to a great extent. • Bio-oil with low oligomers and high organics is suitable for syngas production. This paper investigated the effects of initial bio-oil production conditions (temperature and biomass particle size) on the downstream catalytic and non-catalytic steam reforming of bio-oil. The various bio-oil samples obtained from different pyrolytic temperatures (375, 500, and 580 °C) as well as from different biomass particle sizes (average size from 0.3 to 5.2 mm) were condensed as liquid and then fed into the reforming reactor. The results indicated that the tar yield from the steam reforming decreased significantly by as much as 80% as the original biomass particle size increased from 0.3 to 0.8 mm, but remained almost unchanged for further increasing the particle size up to 5.2 mm. As the biomass particle size increased, the aromatic ring systems in the tars decreased, and the amount of aromatic ring systems in bio-oil tars was much lower than that in biomass tars at the same reforming condition. Additionally, the trends of the effects of bio-oil production temperature and biomass particle size on the tar yields followed the trends of these effects on bio-oil yields, i.e. , the higher the bio-oil yield, the higher the tar yield from bio-oil reforming. The tar yields were affected by the amount of oligomers in the bio-oil to a great extent. The gas yields from steam reforming gradually decreased as the biomass particle size increased. The content of oligomers in bio-oil was not the key factor dominating the formation of gases products, while the content of organics in bio-oil determined the gas yields significantly. According to the results, bio-oil produced at higher temperatures (e.g., 580 °C) from biomass with a small particle size (≤0.3 mm) could generate more syngas from steam reforming using the Fe-loaded bio-char catalyst. [ABSTRACT FROM AUTHOR]

[Display omitted] • Polymerization electro-initiates on cathode surface, and propagates in bio-oil bulk phase. • Large molecules (MW > 800 Da) originally existed in bio-oil contributes to polymerization. • Aromatics, furans and levoglucosan are important polymerization reactants. • Increasing reaction time and current density can enhance polymerization of bio-oil. • Polymer layer forms on anode surface by polymerization. The electrochemical method provides a green route to upgrade bio-oil, but it is still challenged by the issue of bio-oil polymerization which restrains its application. This study investigates the polymerization behaviors of the bio-oil during its electrochemical upgrading under various current densities and different reaction time using macrophotography and multiple characterizations. The results show that the polymerization is not only electro-initiated on the cathode surface, but also electro-propagated in the bulk solution. The large molecules (MW > 800 Da) originally existed in the bio-oil are consumed in the polymerization. The small molecules (MW < 800 Da) can be produced from the polymerization of aromatics with 1–3 rings, furans and levoglucosan through cycloaddition, dehydration and demethoxylation. These small molecules can directly form solid products (coke) rather than leading to the increase of the large molecules. The polymerization can be enhanced by the increasing current density and reaction time. The rate of bio-oil polymerization can surpass the rate of coke formation as the reaction proceeds. The polymer layer also forms on the anode surface by polymerization during the electrochemical upgrading of bio-oil. [ABSTRACT FROM AUTHOR]

The vapor-/solid-phase interactions are the inevitable phenomenon in biomass pyrolysis process, which significantly affects the formation of heavy components (molecular weight > 200 Da) in bio-oil (HCO). In this study, to deeply understand the mechanism of the formation of HCO during biomass pyrolysis, the effects of the vapor-/solid-phase interactions among cellulose, hemicellulose, and lignin (biomass three components) on the formation of HCO during pyrolysis were studied in a fixed-bed reactor system. The HCO were analyzed by the FT-ICR MS spectrometer and the UV-F spectrometer. The results showed that the vapor-phase interactions mainly promoted the formation of heavy phenolic compounds at a slow heating rate, and the total content of HCO was increased. The vapor-phase interactions decreased the total content and the O content of HCO obviously at a fast heating rate; meanwhile, the highly reactive compounds (e.g., furans, acids, and ketones) generated from the pyrolysis of cellulose and hemicellulose could interact with the phenol monomers. Thus the phenolic compounds were transformed into large aromatic compounds via the vapor-phase interactions. The solid-phase interactions facilitated the transformation of O-containing structures of the HCO into the char via cross-condensation reaction, decreasing the yield of HCO, especially the phenolic compounds and the saccharides. • Vapor-/solid-phase interactions affect the heavy components formation in bio-oil. • Effects of vapor-/solid-phase interactions vary with the changes in heating rate. • Vapor-/solid-phase interactions affect the primary and secondary reaction pathways. • Interactions are hard to bring new O-/H-structures into the heavy components. [ABSTRACT FROM AUTHOR]

The electrochemical method has emerged as a novel option for bio-oil upgrading due to the advantages of having mild reaction conditions, control convenience and carbon neutrality. Bio-oil is easy to form coke even at low current densities during electrochemical upgrades of bio-oil. Unveiling the coke evolution during the electrochemical processing of bio-oil is essential to enable both oil-to-material and oil-to-fuel strategies. Here, we investigate the coke formation behaviors during the electrochemical processing of bio-oil. The coke comes primarily from the polymerization of aromatic components. The reaction time and current density have a promoting effect on the coke yields. The current density has an accelerating influence on the morphological evolution of the coke. The O-containing groups increases slightly with the increasing reaction time and current density. The large to small ring ratio of the coke is similar under different reaction time and current densities. The potential applications as carbon materials of the coke formed from bio-oil via electrochemical polymerization are discussed based on its physical morphology and chemical structure. [Display omitted] • Coke yields increase with the increasing reaction time and current density. • Coke typically contains small aromatic clusters connected by ether and C-C bonds. • Time and current density slightly affect chemical structural evolution of the coke. • Increasing current density accelerates morphological evolution of the coke. [ABSTRACT FROM AUTHOR]

[Display omitted] • Raman mapping technology was developed for char structure characterization. • More than 150 individual particles in micro-scale were studied for each sample. • H/C atom ratio of individual char particle in micro-scale was quantified. • Structure evolution characteristics during Zhundong coal pyrolysis was revealed. Heterogeneity of coal in micro-scale is significant and can affect coal thermal behavior. In this study, micro-Raman spectroscopy was developed for characterizing coal/char in the scale of micro- and bulk with a case study of Zhundong coal pyrolysis. More than 150 particles in micro-scale were analyzed for each sample by micro-Raman mapping technology controlled by a computer program. Individual Raman spectrum of each particles in micro-scale and average Raman spectrum for each sample were analyzed, respectively. The results indicate that the evolution characteristics of aromatic rings, C–H in methyl or methylene, and C = O groups can be revealed by combined deconvolution of first- and second-order Raman spectrum. The fluorescence interference in Raman spectrum defined as drift coefficient α can quantitate volatiles content and H/C atom ratio of individual coal/char particle in micro-scale. The results reveal that the chemical structures of the Zhundong coal in micro-scale are significantly heterogeneous. The structural evolution of char particle in micro-scale differs from each other, especially in the early stage of the Zhundong coal pyrolysis. The chemical structure of char particles in micro-scale tends to converge as the pyrolysis progresses. A more severe pyrolysis condition can generally lead to a char with higher heterogeneity. For the bulk structural evolution, the Zhundong coal pyrolysis can be mainly divided into two stages. Firstly, the C–H in methyl or methylene releases rapidly, and the relative amount of small aromatic rings and C = O groups decrease mildly. And then, the aromatization degree of char increases rapidly along with the significant release of C = O groups. [ABSTRACT FROM AUTHOR]

• Higher partial pressure of N 2 suppressed the decomposition of limonene during pyrolysis process. • Shorter residence time in pyrolysis suppressed the decomposition of limonene at high pressures. • The decomposition of limonene can be divided into (1) breaking initially, then cyclizing and (2) direct aromatization. Pyrolysis of waste tires is a promising way to cost-efficiently produce high value limonene, but the reaction characteristics and mechanisms of limonene under pressurized pyrolysis are unclear to date. This study aims to investigate the effects of residence time and pressure on limonene conversion during waste tire pyrolysis. The yields of limonene increased significantly with a decrease of residence time during high pressure pyrolysis. At a pressure of 1.0 MPa, the yield of limonene increases by 20 % as the residence time decreases from 60 s to 15 s, while limonene concentration in TDO (tire-derived-oil) increases to 35.10 wt.%. On the other hand, the pressure has a positive effect on limonene production. The yield of limonene at 1.0 MPa is approximately 1.7 times larger than that of 0.1 MPa at a residence time of 30 s. Based on Spearman correlation analysis, the mechanisms of limonene conversion at pressurized pyrolysis were studied. Longer residence time means limonene undergoes more secondary reactions to be degraded to aromatic rings such as xylene and trimethylbenzene. However, the higher N 2 partial pressure during pyrolysis suppressed the decomposition of limonene, producing TDO with high limonene concentration. Therefore, methods of reducing residence time and increasing pressures promote yield and concentration of limonene in the aspect of inhibiting decomposition, which provides references for improvement in limonene production by waste tire pyrolysis. [ABSTRACT FROM AUTHOR]

• Ni-Fe alloy was formed and played dual promoting effects on the co-production. • The alloy improved the decomposition performance of toluene and H 2 O. • More formation of carbon species and metal carbides promoted the growth of CNTs. • The interaction between Ni particle and support was weakened after Fe addition. • The addition of Fe suppressed the deposition of amorphous carbon. Fe-modified Ni/Al 2 O 3 catalysts with Fe/Ni molar ratios of 0, 0.5, 1 and 2 were prepared to promote the co-production of H 2 and carbon nanotubes (CNTs) during steam reforming of toluene as a tar model compound. After the addition of Fe, toluene conversion increased from 55.1% of Ni/Al 2 O 3 to 73.6% of F1N1A (Fe/Ni ratio of 1), and H 2 yield over F1N1A reached the maximum of more than 2000 mmol/(g-cata). Multi-walled carbon nanotubes with average diameter of 10–30 nm were generated and follow tip-growth mechanism. Compared with Ni/Al 2 O 3 , the addition of Fe remarkably increased the amount and quality of CNTs which had longer length and less tortuosity. These dual promoting effects on H 2 and CNTs after the addition of Fe were attributed to the strong interaction between Ni and Fe in Fe-Ni alloy. Fe-Ni alloy had the high activity for the decomposition performance of toluene and H 2 O to generate more H 2 and intermediates for improving the reforming reaction. Meanwhile, the high catalytic decomposition activity supplied more carbon species and the formation of Fe-Ni alloy enhanced the generation of metal carbide for promoting CNTs growth. Besides, the deposition of amorphous carbon was suppressed and the interaction between Ni particle and catalyst support was weakened after the addition of Fe, which kept the activity of catalyst and promoted the tip-growth of CNTs. [ABSTRACT FROM AUTHOR]

• H 2 yield increased by 7 times while its purity decreased 5% from 500 °C to 800 °C. • Coke amount initially increased to maximum at 650 °C then remarkably decreased. • High temperature enhanced conversion of amorphous carbon to improve CNTs quality. • Almost no CNTs generated at 800 °C due to the sintering of Ni crystallite. The effects of reaction temperature (range from 500 °C to 800 °C) on multiple competitive processes were studied for the co-production of hydrogen and carbon nanotubes (CNTs) during catalytic reforming of toluene over Ni/α-Al 2 O 3. With the temperature raising from 500 to 800 °C, H 2 yield increased by 7 times while H 2 proportion slightly decreased 5 vol% due to the competitive effect between steam reforming and reverse water–gas shift (WGS) reaction. Coke amounts (including amorphous carbon and CNTs) firstly increased and then decreased, which was determined by the competitive rate of formation and consumption reaction. Detailed characterization indicated the yield and quality of CNTs improved with the temperature increasing from 500 to 650 °C and reached the maximum at 650 °C, resulting from the enhancing transformation from amorphous to CNTs and consumption of amorphous carbon by steam. However, the growth of CNTs was suppressed by further increasing temperature, and almost no CNTs were generated at 800 °C. The higher temperature aggravated the sintering of Ni and enlarged their particle size, which was not conduced to CNTs growth. [ABSTRACT FROM AUTHOR]

The certain challenge for the utilization of bio-oil is to investigate the nature and formation of reactive large molecular (heavy) components (>200 Da) in bio-oil. In order to investigate the chemical composition of the heavy components in the bio-oils from the pyrolysis of cellulose, hemicellulose and lignin, the molecular formulas of the heavy compounds and the large aromatic structures were obtained based on the results from the Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) and the ultraviolet fluorescence (UV-F) spectrometer. The results indicated that both the oxygen content and yield of the heavy components showed the highest in the cellulose-oil and the lowest in the lignin-oil. The large molecular compounds were formed mainly via the recombination of the O-containing species, which could be changed at different temperatures and heating rates. Large amount of heavy saccharide and phenolic species existed in cellulose-oil and hemicellulose-oil, while almost no saccharide species and little phenolic species were detected in the lignin-oil. The main heavy components in the lignin-oil were lipids rather than the phenolic species. The heavy components in the bio-oil from the biomass should be mainly derived from the pyrolysis of the cellulose individually or the interactions among the three components. • Main heavy components (>200 Da) in lignin-oil are lipids instead of the phenols. • Heavy components content is highest in cellulose-oil and lowest in lignin-oil. • Methyl groups of the heavy components are easier to be cracked than the O-groups. • High temperature and fast heating rate promote formation of the heavy components. • Heavy components are formed mainly via recombination of O-containing species. [ABSTRACT FROM AUTHOR]