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Abstract: In the present study, one process was selected for a fundamental study of structural evolution during rapid pyrolysis, as well as for the study of the influence of such evolution on char reactivity. Chars were prepared at different situations from rice husk. The reactivity of resultant chars was measured using non-isothermal thermogravimetric analysis. The structure of fresh and partly reacted chars was characterized using proximate and ultimate analyses, physical adsorption/desorption measurements of N2 (−196 °C), mercury intrusion porosimetry (414 MPa), FTIR, Helium pycnometer as well as samples visualization by scanning electronic microscopy (SEM). Appreciable differences in the physical characteristics, depending markedly on the pyrolysis stage, were observed. SEM observation showed that surface of pore in char particle became increasingly rough in the middle of pyrolysis. Micropore characteristics obtained from adsorption/desorption measurement were complex. Release of volatile material led to the development of pores with different changing trends. The surface area of char increased with pyrolysis process to a maximum value of 56.95 m2/g at pyrolysis reaction ratio (R p =0.90). Macropores in char particles which were evaluated by mercury intrusion porosimetry indicated that the porosity increases continually. Combined the analysis result of density with porosity data, it was showed that particle shrinkage happened at the first stage of rapid pyrolysis. The H/C, O/C and N/C ratios of the char changed with different trends when the pyrolysis reaction ratio increased. Furthermore, FTIR studies indicated a gradual decrease in the intensities of OH, C–H and C–O stretches with pyrolysis process. At the end of reaction, most bands disappeared, resulting in a char that was mainly an aromatic polymer of carbon atoms. [Copyright &y& Elsevier]

[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]

Based on the concentrated photo-thermal thermogravimetry analyzer (PT-TGA) reactor, the pyrolysis of the cellulose, hemicellulose and lignin with different ratios at 100 °C/min and 550–850 °C was performed. The interaction among the three components significantly reduced the reaction temperatures and increased the maximum weight loss rate. The cellulose/lignin interactions were the main reason for the increase of gas production, especially for the H 2 production which reached 128.13 mL/g biomass, much higher than the calculated value of 75.35 mL/g biomass without considering the interactions. What occurred during the co-pyrolysis of cellulose/lignin was the combination of free radicals without consuming the hydrogen radicals, while the formation of chemicals in others' interactions integrated with the hydrogen radicals inhibited the production of H 2 at high temperatures. For full-component pyrolysis, the yield of C-containing gas can be calculated by adding a coefficient of interaction between two components, indicating that the effect of the three-component interaction was much lower than that of the two-component. This study established the interaction mechanism for the three components of biomass during photo-thermal pyrolysis based on free radicals. [Display omitted] • Inner-particle reaction significantly accelerated the fast pyrolysis process. • C-containing gases of components mixed in different ratios could be predicted. • Radicals from hemicellulose only promoted C-containing gas yields before 650 °C. • The combination of radicals from cellulose/lignin enhanced the production of H 2. [ABSTRACT FROM AUTHOR]

In pyrolysis of biomass via furnace heating, directions for travel of volatiles and heat flow are opposite. This is drastically different from simultaneously heating surface/inner core of a biomass particle with microwave heating. Changing direction of heat flow and volatiles affects volatiles-char interactions and evolution of pyrolytic products. This was investigated herein by pyrolysis of wet and dry pine needles via furnace or microwave heating at 600 °C. The results indicated that microwave heating induced intensive cracking of outer/inner structures of pine needles. This promoted gasification, decreased production of biochar/bio-oil, diminished formation of both light and heavy organics in bio-oil. Microwave heating also accelerated aromatization, forming biochar of higher C/O and C/H ratios and thermal stability. Additionally, formation of "hot spot" in pyrolysis of wet pine needles via microwave heating was evidenced by the phenomenon of decomposition of CaCO 3 to CaO in pyrolysis, which also contributed to enhanced aromatic degree of biochar. Besides, pyrolysis of wet pine needles via microwave heating also generated developed pore structures in biochar (151.4 m2 g−1), as the inherent water and carbonaceous organics were heated simultaneously. Hydrogen bonding from inherent water was largely cracked only above 500 °C. Prolonged retention time of H 2 O reacted with carbonaceous intermediates, generating more aliphatic structures. Additionally, microwave heating also induced formation of unique morphology like massive thorn-like particulate matters on biochar. [Display omitted] [ABSTRACT FROM AUTHOR]

• 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]

Volatile-char interaction is almost unavoidable in pyrolysis, which is part of the process shaping composition of bio-oil/gases and properties of char. In this study, the influence of the char from sawdust/spinach/rice /spirulina /pig manure on pyrolysis of poplar sawdust was investigated at 500 °C, aiming to understand the impact of the char of same or varied origin on formation of volatiles/gases and change of the char catalysts themselves from the volatile-char interaction. The results suggested that the sawdust-, spinach- or rice-char catalyzed cracking of volatiles, reducing formation of heavy tar, decreasing production of bio-oil (28.6–35.5 % vs 49.4%) while enhancing gases generation (36.9–44.0 % vs 22.4%). The spirulina - and manure-char enhanced secondary condensation of volatiles, producing more heavy tar, more bio-oil, and additional oxygen-rich carbonaceous deposit with highly aliphatic nature. This reduced thermal stability, the C/O ratio of the char catalyst, and also led to coverage of char surface, especially for the manure-char catalyst. The in-situ IR techniques showed that manure-char catalyzed formation of abundant ketones and esters/lactones in intermediates, which further involved in polymerization. In comparison, the sawdust-char catalyst catalyzed cracking and aromatization of the volatiles of same origin, producing carbon- and hydrogen-rich carbonaceous solid, enhancing aromatic nature of the char catalyst, which was actually a real process for evolution of structure of biochar in pyrolysis of the sawdust. [Display omitted] • Sawdust-, spinach- and rice-char enhances cracking, producing more gases but less/lighter bio-oil. • Spirulina- and manure-char enhances polymerization, forming more bio-oil and heavy tar. • Volatiles-char interactions forms deposits over spinach-, spirulina- and especially manure-char. • The O-rich deposits are very aliphatic, reducing thermal stability of spent manure-char. • Volatiles-char interactions over sawdust-char of same origin forms deposit of highly aromatic nature. [ABSTRACT FROM AUTHOR]

• Effects of ex-/in-situ catalysis on bio-oil pyrolysis were investigated. • Less coke and more gas were accomplished by pyrolysing bio-oil with Ni/Al 2 O 3. • Cross-linkage structures formation in coke are influenced by in-situ catalysis. • Coke formation was suppressed via pre-elimination of oxygen-containing groups. Bio-oil can be converted into syngas, chemicals, and carbon materials via thermochemical and/or catalytic conversion routes. However, coking remains a significant challenge during the heating of bio-oil. In this study, we investigated the influence of pre-blending Ni/Al 2 O 3 and bio-oil in an in-situ catalytic pyrolysis process on the coking behaviours of bio-oil. Our results indicate that the presence of Ni/Al 2 O 3 significantly reduces coke yield and increases gas yield (for example, by a 14.2 % reduction in coke and a 44.1 % increase in gas at 700 °C). This is attributed to the suppression of the cross-linking reactions responsible for coke formation through the pre-elimination of O-containing groups into CO and CO 2. Additionally, pre-blending of Ni/Al 2 O 3 is highly desirable for transforming or stabilising the highly reactive substances in the early pyrolysis stage of bio-oil, minimising their tendency to polymerise. Furthermore, the presence of Ni/Al 2 O 3 facilitates the cracking of C–H bonds and self-reforming of bio-oil, increasing H 2 production (which is increased by 42.3 % at 700 °C), thereby promoting the breakage of side chains of lignin-derived aromatics and the hydrogenation of unsaturated structures, suppressing the formation of small aromatic systems in coke (<6 rings). Nevertheless, enhanced formation of alkyl-aryl C–C bonds during aromatisation leads to more condensed coke structures. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel concept called Solar Char-Cycling Pyrolysis (SCCP) has been developed. • Solar enhanced char-cycling biomass pyrolysis process was modeled for the first time. • In SCCP process, pyrolysis has the highest exergy destruction due to no combustion. • Due to the external biochar, the SCCP process showed the highest CH 4 and CO yields. Pyrolysis is an efficient technology for converting biomass into value-added products, characterized by endothermal reactions. The introduction of induced solar irradiance can boost product yields and reduce carbon emissions associated with incineration. However, direct solar pyrolysis faces challenges due to difficulties in maintaining a clean solar window, which is essential to ensure efficient sunlight penetration. To address this issue, a novel concept called Solar Char-Cycling Pyrolysis (SCCP) has been developed. In this work, to demonstrate the potential of solar enhanced biomass pyrolysis process as a promising biomass treatment technology, energy and exergy analyses of Autothermal Pyrolysis (AP), Solar Direct Pyrolysis (SDP), and Solar Char-Cycling Pyrolysis (SCCP) processes were studied in Aspen Plus. The results showed that SCCP has the highest energy and exergy efficiencies, which were 90.81% and 76.51%, respectively. In comparison, the solar energy utilization efficiency of char-cycling was 82.18% due to the high radiative heat absorptivity of biochar. Meanwhile, the energy efficiencies for AP and SDP were 87.17% and 80.23 %, respectively. The lower efficiency of SDP was attributed to window contamination. When the solar adsorption efficiency of the SDP process falls below 82.18%, it leads to a lower efficiency than the SCCP process. Through the energy analysis, it was proved that in the SCCP process, solar energy could fully cover the pyrolysis energy requirement since it overcame the problem of window contamination. Through the exergy analysis, it was shown that the SCCP process has the highest exergy efficiency compared to AP and SDP, which was caused by avoiding biochar incineration and enhanced solar energy utilization. This study gives a comprehensive evaluation of biomass solar pyrolysis applications, with the char-cycling method presenting an innovative approach for the efficient utilization of solar energy. [ABSTRACT FROM AUTHOR]

• Insufficient removal of organics in chicken bone (CB) at 400 °C forms littles pores. • Effective removal of organics at 650/800 °C obtains mesopore and high cu dispersion. • Carbonaceous residual from CB results in flower-like morphology of Cu/CB catalysts. • Cu/CB-800 with higher cu dispersion and surface area is active for hydrogenation. • Strong adsorption of functional groups over Cu/CB-800 enhances catalytic activity. Metal/biochar catalysts are prepared by direct impregnation of metal salts with biochar produced from pyrolysis. However, the surface structure of the catalyst carrier is affected by the pyrolysis temperature. Different pyrolysis temperatures can produce different pore structures, which can affect the dispersion of active metals. To verify this, Cu/bone biochar catalysts were prepared by directly supporting copper nitrate on the biochar from chicken bone pyrolysis at 400, 500, 650, and 800 °C, respectively. Catalytic performance of Cu/bone biochar catalysts for vanillin hydrogenation was evaluated. The results showed that the hydroxyapatite produced after pyrolysis of chicken bones was relatively stable, which made the catalyst with superior activity and reusability. The catalyst prepared by pyrolysis at a lower temperature had fewer pore structures on its surface, and the active metal Cu was easily sintered. With increasing pyrolysis temperature, organic matter gradually decreased and more pore structures were generated on the surface of the catalyst carrier, which was more conducive to the dispersion of metallic Cu species. The catalyst prepared from the chicken bone pre-pyrolyzed at 800 °C exhibited uniform dispersion of metal Cu, with the average particle size of Cu particles of 11.9 nm, achieving the yield of 91.7 % for 2‑methoxy-4-methyl phenol from hydrogenation of vanillin. In-situ IR characterizations also showed that, with the increase of pyrolysis temperature, the surface functional groups of the catalyst were more conducive to the hydrogenation of vanillin. The effect of pyrolysis temperature on pore structure and dispersion of metallic Cu of metal/biochar catalysts was investigated for conversion of vanillin. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Formation and evolution process of PFRs during biomass pyrolysis was investigated. • Effect of biomass property and pyrolysis temperature on the PFRs was clarified. • Relationships between PFRs characteristics and chemical structure were established. • Three-stage evolution mechanism of PFRs in biochar during pyrolysis was revealed. The persistent free radicals (PFRs) in biochar can play a crucial role during biochar's utilization, but the formation and evolution mechanism of PFRs in biochar are poorly understood because of biochars' element specificity and chemical structure complexity. In order to further understand the formation and evolution mechanism of PFRs, the PFRs characteristics, chemical structure and element composition of six types of biomasses were investigated. The results revealed that the changing trend of the PFRs types, concentration and line width with pyrolysis temperature is similar for all six feedstocks. The difference in the feedstocks' properties just affects the absolute value of PFRs' characteristic parameters. The arrangement and combination of elements and carbon skeleton structure in biochar determine the evolution of PFRs in the pyrolysis process. Additionally, the (H + O)/C atomic ratio of the biomass feedstock and the content of substitutional groups on aromatic rings were found to influence the types of PFRs in biochar. When biochar has a similar O/C atom ratio, a higher H content can reduce the carbon-centered PFRs in biochar. Besides, the reduction in O element content contributes to a decrease in line width due to the reduction in the effect of heteroatoms. The good correlation between O/C atomic ratio, H/C atomic ratio, chemical structure and PFRs characteristics can be used to predict the PFRs characteristics. Combining the changing characteristics in PFRs concentration and carbon skeleton structure of biochar, a three-stage model of PFRs formation and evolution was constructed. [ABSTRACT FROM AUTHOR]

Abstract: Plastics from waste electrical and electronic equipment (WEEE) have been an important environmental problem because these plastics commonly contain toxic halogenated flame retardants which may cause serious environmental pollution, especially the formation of carcinogenic substances polybrominated dibenzo dioxins/furans (PBDD/Fs), during treat process of these plastics. Pyrolysis has been proposed as a viable processing route for recycling the organic compounds in WEEE plastics into fuels and chemical feedstock. However, dehalogenation procedures are also necessary during treat process, because the oils collected in single pyrolysis process may contain numerous halogenated organic compounds, which would detrimentally impact the reuse of these pyrolysis oils. Currently, dehalogenation has become a significant topic in recycling of WEEE plastics by pyrolysis. In order to fulfill the better resource utilization of the WEEE plastics, the compositions, characteristics and dehalogenation methods during the pyrolysis recycling process of WEEE plastics were reviewed in this paper. Dehalogenation and the decomposition or pyrolysis of WEEE plastics can be carried out simultaneously or successively. It could be ‘dehalogenating prior to pyrolysing plastics’, ‘performing dehalogenation and pyrolysis at the same time’ or ‘pyrolysing plastics first then upgrading pyrolysis oils’. The first strategy essentially is the two-stage pyrolysis with the release of halogen hydrides at low pyrolysis temperature region which is separate from the decomposition of polymer matrixes, thus obtaining halogenated free oil products. The second strategy is the most common method. Zeolite or other type of catalyst can be used in the pyrolysis process for removing organohalogens. The third strategy separate pyrolysis and dehalogenation of WEEE plastics, which can, to some degree, avoid the problem of oil value decline due to the use of catalyst, but obviously, this strategy may increase the cost of whole recycling process. [Copyright &y& Elsevier]

Abstract: The effects of pyrolysis temperature and heating rate on the porous structure characteristics of rice straw chars were investigated. The pyrolysis was done at atmospheric pressure and at temperatures ranging from 600 to 1000°C under low heating rate (LHR) and high heating rates (HHR) conditions. The chars were characterized by ultimate analysis, field emission scanning electron microscope (FESEM), helium density measurement and N2 physisorption method. The results showed that temperature had obvious influence on the char porous characteristics. The char yield decreased by approximately 16% with increasing temperature from 600 to 1000°C. The carbon structure shrinkage and pore narrowing occurred above 600°C. The shrinkage of carbon skeleton increased by more than 22% with temperatures rising from 600 to 1000°C. At HHR condition, progressive increases in porosity development with increasing pyrolysis temperature occurred, whereas a maximum porosity development appeared at 900°C. The total surface area (S total) and micropore surface area (S micro) reached maximum values of 30.94 and 21.81m2/g at 900°C and decreased slightly at higher temperatures. The influence of heating rate on S total and S micro was less significant than that of pyrolysis temperature. The pore surface fractal dimension and average pore diameter showed a good linear relationship. [Copyright &y& Elsevier]

Abstract: The gas release properties and char structural evolution during the pyrolysis of cotton stalk were investigated. The evolution characteristics of volatile products were examined by pyrolysis–Fourier transform infrared spectroscopy (FTIR)/thermal conductivity detection (TCD) analysis (Py–FTIR/TCD). The char chemical structure and physical characteristics were investigated by means of FTIR and N2 physisorption techniques. Evolution characteristics of the main volatile products were given. The evolution of CO2 was approximately 26°C earlier than that of CO. CH4 evolution covered over a wider temperature range of 300–600°C, with a maximum at 394°C. The amount of hydroxyl, aliphatic Cfinic Cn the char decreased significantly above 250°C. The aromatization process started at ≈350°C and continued to higher temperatures, leaving the char enriched with condensed aromatic ring systems. The BET surface area increased continually with increasing temperature to reach a maximum value of 4.68m2/g at 500°C and decreased at higher temperatures. The micropore volume showed a similar behavior to the surface area, while the mesopore volume and total pore volume always increased. [Copyright &y& Elsevier]

Soybean residue (SR) is a main solid waste produced during the extraction of soybean oil with bulk volume. In addition to the use as vegetable protein feed, SR could also be used as feedstock for producing biofuels and carbon materials via pyrolysis. In this study, the pyrolysis behaviors of SR at varied temperatures and heating rates were investigated. The results show that the pyrolysis of the organic components in SR could reach completion even at 500 °C, due to the lower thermal stability of the organic component than that in the typical biomass. This also leads to the bio-oil with little heavy organics and also low carbon content of the resulting biochar, as the organic components decomposed to a significant extent while the charring reactions were insignificant. This leads to the biochar with low heating value and low energy yield when compared with that in the pyrolysis of typical biomass. In addition, the high content of proteins, amino acids and other nitrogen-containing nutrients make the SR derived bio-oil nitrogen-rich and a significant portion of nitrogen could also be retained in the biochar. These specialties have to be considered during their applications as either biofuels or functional carbon materials. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: Pyrolysis of agricultural residues (maize stalk, rice straw and cotton straw) was studied using a thermogravimetric (TG) analyzer and a laboratory scale fixed bed coupled with Fourier transform infrared (FTIR) analyzer. Pyrolysis characteristics of three materials were discussed. The characteristic parameters were determined for the main devolatilization step. Maize stalk showed the highest thermal reactivity, followed by cotton straw and rice straw. Their pyrolysis processes underwent three consecutive stages, corresponding to the evaporation of water, the formation of primary volatiles and the subsequent release of small molecular gases. In order to further study the pyrolysis mechanisms of agricultural wastes, the release of the main volatile and gaseous products were on-line detected by FTIR spectroscopy. The results showed that the major pyrolysis gases for the three materials were similar, including CO2, CO, methane, ethane, ethylene and some organics such as methanol, formaldehyde, formic acid and acetone. HCN was the major nitrogen containing product. At higher temperatures several small molecular gases, such as CO2, CO and methane, could still be monitored. [Copyright &y& Elsevier]

Serious coking from the bio-oil polymerisation is a bottle-neck challenge for bio-oil thermal upgrading. Probing the mechanism of bio-oil coking is the first step to achieve high carbon conversion efficiency. In this study, in-situ electron paramagnetic resonance (EPR) spectroscopy was used to characterise the stable free radical generation during bio-oil pyrolysis at 250–350 °C with reaction time of 2–10 min, which identify the coking process of bio-oil. The liquid and solid products were characterised using gas chromatography-mass spectrometer (GC–MS), ultraviolet fluorescence (UV-F) and Raman spectroscopy. The results indicate that the coking of bio-oil in pyrolysis can be divided into three stages of varied characteristics. The coke formation precedes with an initial induction period that lasts for 2–8 min and shortens with increasing pyrolysis temperature. In the period, light components polymerise into heavy ones, including polycyclic aromatics as the essential coke precursors. After the induction period, significant amounts of stable free radicals are generated with coke formation, and the content increases from 0.2 to 1.6–7.8 μmol/g bio-oil in the early stage of coking. Meanwhile, the coke precursors, polycyclic aromatics, are rapidly depleted. Afterwards, in the late stage, the nascent coke gradually condenses and the stable free radical content increases slowly. • In-situ EPR detection was used to identify the coke formation in bio-oil pyrolysis. • Coke formation and stable radicals generation are simultaneous during pyrolysis. • Coke formation is preceded by an induction period at the start of bio-oil pyrolysis. • In induction period, polycyclic aromatics accumulate due to bio-oil polymerisation. [ABSTRACT FROM AUTHOR]

Pyrolysis technology is an effective way to realize the reduction and recycling of food waste (FW), but the generation of N-containing substances has a great impact on the quality of pyrolysis products and the environment. The present study mainly focused on the effect of typical component interaction on nitrogen conversion during the pyrolysis of FW, which was investigated by TG-FTIR, GC-MS, and DFT calculation. The experimental results show that during pyrolysis at 500 ℃, compared with soybean protein pyrolysis, co-pyrolysis of soybean protein with rice starch reduces the production of NH 3 and HCN in the pyrolysis gas and reduces the production of nitriles in the pyrolysis oil, while the production of N-containing heterocycles and amides in the pyrolysis oil increases. Soybean protein and rice starch promote the immobilization of N in pyrolysis oil through Maillard reaction and produce Maillard reaction products (MRPs). MRPs can be converted to nitrogenous heterocycles by ring formation reactions, and to amides by continued cleavage, which results in the increased yields of N-containing heterocycles and amides in the pyrolysis oil. • The effect of starch and protein interaction on nitrogen conversion was studied. • The N-containing heterocycles yields in oil during co-pyrolysis of starch and protein is significantly higher. • Maillard reaction products can be converted to N-containing heterocycles through ring-forming reactions. • MRPs can be converted to amides by lysis reaction. [ABSTRACT FROM AUTHOR]

Bio-oil has a high tendency towards coking upon heating, which can be the feedstock for production of carbonaceous materials with particular morpholpgy. Herein, production of carbon nanospheres via bio-oil pyrolysis at 800–1100 °C was conducted. The results revealed that the increasing temperature promoted the formation of carbon-rich structures of the nanospheres. The primary precursors for carbon spheres were identified as small gas-phase molecules. The competitive production of carbon spheres and flake carbon was observed, while carbon spheres gradually became the main product at higher pyrolysis temperature (>1000 °C). Furthermore, the abundance of aromatic organics was a critical factor for carbon nanosphere formation. Among the typical model components, the yields of carbon nanosphere at 1100 °C followed the order: guaiacol (38.2 wt%) > furfural (36.6 wt%) > heavy components (28.5 wt%). While acetic acid, acetone, and methanol as model compounds showed a yield of 0 wt%. The degree of interactions among bio-oil components also influenced the yield and properties of the produced carbon nanospheres. The addition of guaiacol to bio-oil facilitated the production of carbon spheres and graphitization, achieving a substantial yield of 12.7 wt% at 900 °C. However, the addition of methanol leads to a decrease in yield of carbon nanospheres. • Carbon nanospheres can be produced via bio-oil pyrolysis. • Interactions among bio-oil components influenced the yield and properties of carbon nanospheres. • The order of carbon nanosphere yields was as follows: guaiacol > furfural > heavy components. • Adding guaiacol to bio-oil improved the yields and graphitization of carbon nanospheres. [ABSTRACT FROM AUTHOR]

Heavy components in bio-oils pose significant challenges for their utilisation through thermal conversion, as they are highly reactive and prone to polymerisation upon heating. This study investigates the formation and reduction of heavy components during ex-situ and in-situ catalytic pyrolysis of bio-oil over Ni/Al 2 O 3. The heavy components present in the volatile products from bio-oil pyrolysis can be cracked for ex-situ catalysis. In contrast, in-situ catalysis results in catalyst deactivation due to the polymerisation of bio-oil components. However, at temperatures >700 °C, as thermal cracking reactions dominate during bio-oil pyrolysis, in-situ catalysis can further suppress the polymerisation among bio-oil components. As a result, the tar and coke yields decrease by 9.8 wt% and 2.7 wt% at most. • Evolution of heavy components during in−/ex- situ catalysis were investigated. • Tar and coke were decreased by in-situ catalytic pyrolysis of bio-oil. • O-containing groups in heavy components tend to be cracked over Ni/Al 2 O 3. • Ni leads to more C−C- cross-linkage structures in heavy components. [ABSTRACT FROM AUTHOR]

Torrefaction of biomass is a well-known pretreatment method that can remarkably influence evolution of property of pyrolytic products in subsequent pyrolysis. Automobile shredder residue (ASR) is an important product in car recycling and it needs to be pretreated before recycling via pyrolysis. Nevertheless, how torrefaction impacts the composition and pyrolysis behaviours of ASR is still unknown, as ASR has a distinct composition from biomass. Thus, this study investigates the effect of torrefaction on the formation of heavy components in pyrolysis oil. ASR samples were torrefied from 240 °C to 330 °C and subsequently pyrolyzed from 600 °C to 800 °C with varied heating rates (ca. 80 °C /s and 0.17 °C /s). Results indicate that compared to raw ASR pyrolysis oil, torrefaction enhances the interaction between the volatile and semi-char, promoting the polymerization to form precursors of heavy components, thus the relative content of heavy components increases by >50% and heavy components containing heteroatoms decrease by >30% in the torrefied ASR pyrolysis oil, with the release of volatile heteroatom-containing compounds during torrefaction. More aliphatic heavy components are generated, reducing the overall aromaticity and degree of unsaturation of heavy components in the pyrolysis oil. [Display omitted] • Torrefaction promotes the formation of heavy components in ASR pyrolysis oil. • Torrefaction reduce the heteroatomic content in ASR pyrolysis oil. • The unsaturation degree of heavy components was reduced after torrefaction. • A proposed formation mechanism of heavy components in ASR's oil is provided. [ABSTRACT FROM AUTHOR]

An analysis was conducted on two integrated models involving direct co-firing and pyrolysis co-firing systems within a typical 600 MW coal-fired power generation plant. The study assessed the performance of various biomass sources (sawdust, corn straw, and rice husk) using distinct co-firing ratios (5%, 10%, 15%, 20%) across technological, environmental, and economic dimensions. The findings revealed that in terms of thermal and exergy efficiency, the pyrolysis co-firing approach exhibited lower results compared to direct co-firing. Notably, among the biomasses tested, sawdust demonstrated the least impact on boiler efficiency. The CO 2 emission was estimated by the Life Cycle Assessment method. The emission of the conventional boiler, along with direct and pyrolysis co-firing of corn straw at a 20% ratio, resulted in CO 2 emissions of 1.075 kg, 0.954 kg, and 0.942 kg per 1kWh of electricity, respectively. The different feeding methods were also discussed, providing technically and economically rational options for coal-fired power plants. The economic feasibility of both co-firing systems was also proposed. At carbon tax rates of 410 CNY/t and 464 CNY/t for the direct co-firing and pyrolysis co-firing models respectively, the operational cost of the co-firing systems becomes comparable to that of a coal-fired boiler. However, when the by-product price exceeds 3700 CNY/t, the pyrolysis co-firing model becomes the more economically favorable option. This study primarily concentrates on investigating the real-world application and effective utilization of biomass co-firing systems within the specific framework of China's energy scenario. [Display omitted] • Co-firing processes of coal and biomass has been simulated and taken a 3E assessment. • Increased blending ratio leads to higher power generation cost and lower efficiency. • Providing options to select co-firing methods, ratio and biomass type. • Byproduct char can be sold and has economic benefit than direct combustion in boiler. [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]

Coal is naturally heterogeneous on chemical structure, which significantly affects its pyrolysis behaviours. However, due to the limit of characterization tools, quantification of the chemical structural heterogeneity and its effects on pyrolysis are still challenging. In this study, a quantification method for chemical structural heterogeneity by Raman mapping technique was firstly proposed, and the heterogeneous chemical structure of coal was investigated. The results show that the distributions of the chemical structure are highly uneven, even though the average structural characteristics are highly similar. Besides, the effects of chemical structural heterogeneity on pyrolysis behaviours were studied. It is found that except for the average structural properties, the chemical structural heterogeneity affects the pyrolysis behaviours significantly. It is attributed to the different pyrolysis mechanisms and uneven distribution of these chemical structures with different reactivity. The effects of the average chemical structures and the chemical structural heterogeneity on the pyrolysis behaviours are independent. Furthermore, new predicting models for pyrolysis behaviours by considering both the average structure and the chemical structural heterogeneity were established and validated. The final models were proved to be adequate to effectively predict the pyrolysis behaviours of raw and blended coals. [Display omitted] • Coal chemical structural heterogeneity was quantified by Raman mapping. • 3 kinds of structures varied in reactivity were identified by chemical distribution. • Effects of chemical structural heterogeneity on pyrolysis behaviours were revealed. • Predicting models of pyrolysis behaviours considering heterogeneity were built up. [ABSTRACT FROM AUTHOR]

Stable free radicals are the long-lived macromolecule radicals formed in pyrolysis, and their reactions play an essential role in biochar formation. The alkali and alkaline earth metals (AAEMs) in biomass might be involved in the radical reactions during pyrolysis. Figuring out the effect of AAEMs on the reactions of stable free radicals can further understand the radical reaction mechanism and the formation of biochar in pyrolysis. In this paper, the in-situ electron paramagnetic resonance (EPR) spectroscopy was used to detect the stable free radicals in cocoanut pyrolysis, and the effect of AAEMs was analysed by the comparative experiments. The results indicate that the stable free radicals in nascent chars, which are generated from the thermal decomposition of biomass, could react and couple with each other. The AAEMs in biomass improve the activity of stable free radicals and promote the radical-radical coupling during high-temperature pyrolysis above 400 °C, which inhibits the condensation of aromatic structure and generates more weak bonds in hot nascent char. After stopping the heating, the weak bonds will be broken by cooling stress, thus inducing radical reactions and further changing the char structure. • In-situ EPR detection was used to study stable radicals during biomass pyrolysis. • Effect of alkali and alkali earth metals on stable radical reactions was analysed. • Nascent char formed in pyrolysis has secondary reaction after volatiles releasing. • Alkali and alkali earth metals promote coupling of stable radicals during pyrolysis. • Unstable structures formed by stable radicals coupling can be broken during cooling. [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]

The interaction between volatiles and homologous and/or heterologous char is almost inevitable during the transfer or diffusion of volatiles from inner core to outer surface of a biomass particle in pyrolysis. This shapes both composition of volatiles (bio-oil) and property of char. In this study, the potential interaction of lignin- and cellulose-derived volatiles with char of varied origin was investigated at 500 °C. The results indicated that both the lignin- and cellulose-char promoted polymerization of the lignin-derived phenolics, enhancing production of bio-oil by ca. 20%–30%, generating more heavy tar but suppressing gases formation, especially over cellulose-char. Conversely, the char catalysts, especially the heterologous lignin-char, promoted cracking of the cellulose-derivatives, producing more gases while less bio-oil and heavy organics. Additionally, the volatiles-char interaction also led to gasification of some organics and also aromatization of some organics on surface of char, resulting in enhanced crystallinity and thermostability of the used char catalyst, especially for the lignin-char. Moreover, the substance exchange and formation of carbon deposit also blocked pores and formed fragmented surface dotted with particulate matters in the used char catalysts. [Display omitted] • Char catalyzes condensation of lignin-derived phenolics, forming more bio-oil. • Char catalyzes cracking of cellulose-derived volatiles, forming more gases. • Interaction between heterologous char and volatiles is more intense. • Interaction enhances gasification/aromatization, making char more aromatic. • Interaction causes matter exchange, blocking pores and changing char morphology. [ABSTRACT FROM AUTHOR]

Understanding the complexity of thermal degradation characteristics, kinetic behavior, and thermodynamic parameters is pertinent for the efficient design and process optimization of large-scale conversion systems. Comparative assessment of pyrolysis characteristics and thermodynamic parameters of corn cobs (CC), peanut shells (PS) and sugarcane bagasse (SB) are investigated using high heating rates (100–1000 ℃/min) TGA results. Despite the effect of the heating rate increase on the degradation process of individual samples, increasing heating rates affect pyrolysis characteristics due to compositional differences. With increasing heating rates, the comprehensive pyrolysis index increased sporadically for CC (2.54–44.09 ×104%2/min2 ℃3) and PS (1.36–31.13 ×104%2/min2 ℃3), indicating easier release of volatiles at higher pyrolysis heating rates. The pyrolysis stability index (R w), which relates to thermal degradation stability, presented an increasing trend (CC>PS>SB) with a heating rate increase (≥106%). Kinetic parameters estimated using model-free methods showed that the activation energies of CC and PS were significantly lower than that of SB. Comparative evaluation of fractional conversions and kinetic parameters using traditional and modified parallel models showed that the double random pore model (DRPM) fitted the best for simulating the experimental results at higher heating rates than other models. The change in Gibbs free energy (ΔG) trend for PS and SB showed a deviation, suggesting reaction difficulties due to higher temperature demands. • High heating rates TGA analysis is performed for corncob, peanut shell and bagasse. • Corncob presented the best pyrolysis stability index with a heating rate increase. • Model-free methods and modified parallel models were used for kinetic studies. • The double random pore model is best suited for simulating the experiment results. • Thermodynamic parameters were comparatively studied from the kinetic results. [ABSTRACT FROM AUTHOR]

Highlights • Interactions among bio-oil fractions influence the coking mechanisms obviously. • Structure of cokes generated from bio-oil was strongly affected by the interactions. • Cokes from bio-oil are not simple mixture of cokes from bio-oil fractions. • Interactions increase the C O, O H and C O functional groups in cokes. • Interactions promote the O-containing species to be transformed into the cokes. Abstract Coke formation is one major problem during thermal conversion of bio-oil and its main components. Fundamental knowledge about the evolution of the structure of cokes is a prerequisite towards a deep understanding of coking of bio-oil. This study investigates the structure (morphology, elemental composition, O-containing functional groups and aromatic structures) of cokes generated from the pyrolysis of aromatic-rich fraction (ARF) and the aromatic-poor fraction (APF) of bio-oil. The effects of interactions of ARF and APF on properties of the coke formed during the pyrolysis of bio-oil are also studied. The results show that the cokes from the pyrolysis of APF (APF-cokes) are sponge-like while the cokes from the pyrolysis of ARF (ARF-cokes) have a dense structure. The matrix of cokes from the pyrolysis of the whole bio-oil (oil-cokes) is similar to the matrix of ARF-cokes, while its surface is similar to that of APF-cokes, which should be due to the interactions between different bio-oil fractions. The APF-cokes contain more C O, O H and C O functional groups than the ARF-cokes due to the higher O content of APF. Moreover, the interactions between ARF and APF can promote more O-containing species to be transformed as C O, O H and C O functional groups in the oil-cokes. The aromatic rings of ARF-cokes and APF-cokes can be cracked to form smaller ring systems at 300–500 °C, while it is opposite for the oil-cokes because the aromatic structures formed via the interactions between ARF and APF are more stable. At higher temperatures (>500 °C), the interactions (e.g. self-gasification) lead to the highly condensed cokes, while the secondary cokes, which are spherical particles, are preferentially consumed by the steam. [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]

This study focuses on the effects of interactions among bio-oil components on the formation of aromatic structures of bio-oil during its thermal treatment processes at various temperatures and heating rates. A bio-oil sample and its extracted fractions were pyrolyzed in a fixed-bed reactor at 300–800 °C at different temperatures and heating rates. The results show that the pyrolytic products (including the yields and aromatic structures) from raw bio-oil and its extracted fractions are significantly different, which proves the existence of the interactions between the aromatic components and light components of the bio-oil. Additionally, those interactions are determined by the pyrolysis temperature and heating rate to different extents, which further leads to the evolution of aromatic structures during the pyrolysis of bio-oil. For example, owing to the presence of the aromatic-poor fraction, the aromatic compounds (especially ≥ 2 rings) from the pyrolysis of bio-oil are less than that of the aromatic-rich fraction at relatively low temperatures (≤ 500 °C), especially at slow heating rates. This is because the polymerization, as the main interactions, promotes the transformation of more aromatic compounds (over wide range of ring sizes) into coke at these conditions. At fast heating rates, among the complex interactions, the self-gasification of bio-oil is intensified at high temperatures (≥ 700 °C), resulting in lower secondary coke yields and tar yields as well as the concentration of aromatic compounds (especially ≥ 2 rings). [ABSTRACT FROM AUTHOR]

Highlights • Cokes generated at slow heating rates are imporous with smooth surface. • The radical concentration of cokes reaches highest at 600 °C then decreases rapidly. • Interactions among bio-oil components bring the O-functional groups into the coke. • The cokes are more condensed with bigger aromatic rings at high temperatures. Abstract Coke can be formed once the bio-oil was heated, even at very low temperatures, causing almost always serious problems in the upgrading and direct utilization of bio-oil. To minimize the negative impacts from coke formation, the key point is to fully understand the formation and evolution of coke during the thermal treatment of bio-oil. Thus, in this study, the cokes formed from the pyrolysis of bio-oil at different temperatures (300–800 °C) and heating rates were characterized by using a range of advanced analytical instruments. The evolution of cokes (e.g. morphology, elemental composition, chemical structure and concentration of radicals) with increasing temperature and heating rate was traced. The results show that the cokes generated at slow heating rates are imporous with smooth surface but porous at high temperatures and fast heating rates. The radical concentration of the cokes reaches the highest level at 600 °C, then decreases rapidly with further increasing temperature to form more free radicals, which promote the condensation reaction of aromatic systems to form larger ring structures of the coke at high temperatures, with lower H/C and O/C ratios. The O-containing functional groups could be brought into the coke via the interactions between light and heavy components of bio-oil. [ABSTRACT FROM AUTHOR]

Highlights • Less gases while more tar formed over acidic oxides than that over basic oxides. • Over CaO, the production of phenolic compounds was suppressed. • Coking was more significant over the basic oxides than that over the acidic oxides. • The tar from cellulose contributed more to coking than that from lignin. • Cellulose–derivatives and lignin–derivatives affect coke structures in varied ways. Abstract This study investigated the effects of the acidity/alkalinity of seven oxides (Al 2 O 3 , SiO 2 , ZnO, K 2 O, MgO, CaO, La 2 O 3) on the pyrolysis of poplar, cellulose and lignin. The results showed that the basic supports such as CaO and MgO promoted the formation of gaseous products. CO, CO 2 , and CH 4 were the main gaseous products in the pyrolysis of poplar, cellulose and lignin, and CO was formed first, followed by CO 2 and CH 4. Some H 2 was also formed from the dehydrogenation reactions over CaO with cellulose as the feedstock. The acidic oxides promoted the tar formation, while the basic oxides suppressed tar formation. The oxides like CaO could remarkably suppress the production of phenolic compounds. The coke formation over the basic oxides were also much more significant than that over the acidic oxides, and the tar from cellulose contributed more towards coking. The heating of the coke in inert gas released CO 2 , CO, H 2 , CH 4 via probably decarboxylation/decarbonylation, dehydrogenation and etc. The coke from the pyrolysis of lignin was much more stable. CaO and La 2 O 3 reacted with the CO 2 produced in pyrolysis and form the carbonates, while MgO could not. The TPO–MS characterization showed that the coke species were multiple types over CaO, and a single type over MgO. The cellulose–derivatives and the lignin–derivatives have distinct effects on the structural configuration of the coke. [ABSTRACT FROM AUTHOR]

[Display omitted] • The evolution of nitrogen in pyrolysis oil and pyrolysis gas during the pyrolysis of food waste was investigated. • NH 3 mainly comes from the detachment of amino groups. • HCN is mainly derived from the dehydrogenation of amino acids and the cleavage of N -containing heterocycles and nitriles. • N -containing heterocycles are the main N -containing substance in pyrolysis oil. • N -containing heterocycles are generated by de-H 2 O or intermolecular de-H 2 O of amino acids or condensation reactions of amino acids with small molecules. Pyrolysis technology is an effective way to realize the reduction and recycling of food waste (FW), but the generation of N -containing substances has a great impact on the quality of pyrolysis products and the environment. The present study mainly focused on the migration and transformation mechanism of N during the pyrolysis process of FW, which was investigated by TG-FTIR, GC–MS, and DFT calculation. The experimental results show that NH 3 and HCN are the main N -containing gas products, and the N -containing substances in the pyrolysis oil are mainly N -containing heterocycles (21.82%), nitriles (6.43%), and amides (4.00%) at 500 ℃. The proteins in food waste are cleaved into various amino acid molecules at temperatures above 300 ℃. Some amino acid molecules generate NH 3 and HCN by removing various groups. Some other amino acid molecules generate N -containing heterocycles, nitriles, amides, and various other N -containing substances by intramolecular de-H 2 O or intermolecular de-H 2 O reactions of amino acids or condensation reactions of amino acids with small molecules and transfer to the pyrolysis oil. As the temperature increases, most of the N -containing heterocycles and nitriles will be cleaved and generate HCN. [ABSTRACT FROM AUTHOR]

Microwave heating is different from furnace heating in terms of heat transfer direction and heating mechanism. The torrefaction with microwave or furnace heating might further impact evolution of the pyrolytic products in further pyrolysis. This was investigated herein via thermal pretreatment of sawdust at 150 to 250 °C and the subsequent pyrolysis at 600 °C. The results showed that the microwave pretreatment led to more pronounced pyrolysis at 200/250 °C, which enhanced aromatic degree of semi-char and created difficulty for its further cracking in pyrolysis at 600 °C but not affected gasification. This led to the formation of more biochar and much more gases but less bio-oil with less heavy components than that from furnace heating plus pyrolysis. Additionally, the microwave pretreatment could enhance deoxygenation but the enhanced aromatic degree of the semi-char created difficulty for creating micropores and development of the pore structures (176.2 m2g−1 with 67.3% micropores from microwave pretreatment versus 441.1 m2g−1 with 78.5% micropores from furnace pretreatment). The characterization of the pyrolysis of semi-char with in-situ IR technique confirmed that the microwave pretreatment substantially removed the aliphatic structures and made the biochar with more fragmented morphology. [Display omitted] • Microwave pretreatment (MP) at 200/250 °C induces aromatization of semi-char. • MP forms more biochar/gases but less bio-oil than furnace pretreatment (FP) in semi-char pyrolysis. • MP at 250 °C hinders formation of micropores in pyrolysis but forms more mesopores. • In-situ DRIFTS measurement indicates less aliphatic structures in semi-char from MP. • MP plus pyrolysis lead to biochar of more fragmented morphologies. [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]

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]

The current study aimed to investigate catalytic behaviors of alkali metal salt participating in homogeneous steam-volatile and heterogeneous steam-char reforming reactions in steam gasification of cellulose. The results indicate that the temperature is a key parameter which significantly influenced both yield and composition of gas and tar and catalytic performances of KCl. Externally added steam had negligible effect on cracking/reforming of macromolecules volatiles at the temperature of 700 and 900 °C without KCl, whereas in the presence of KCl, it would be activated and further reacted with low reactivity macromolecules volatiles, leading to an increase in gas yield and a decrease in tar yield. KCl was notably involved in homogeneous steam-volatile reactions, and enhanced the water gas shift reaction and tar reforming reactions. However, KCl had little promotion effect on thermal cracking/reforming of levoglucosan in homogeneous steam-volatile reforming process at 500 °C. Its inhibition effect on levoglucosan formation mainly acted during the primary pyrolysis reactions. KCl could also enhance heterogeneous in situ char-steam reaction resulting in a higher H 2 yield. The general pathway of KCl involved in homogeneous/heterogeneous reactions in steam gasification of biomass was eventually proposed. [ABSTRACT FROM AUTHOR]

Sewage sludge, the inevitable by-product of municipal wastewater treatment plant operation, is a key issue in many countries due to its increasing volume and the impacts associated with its disposal. Thermochemical processing offers a new way of managing sewage sludge, not only by providing effective volume reduction, but also enabling transformation of carbon-rich organic fraction into valuable energy and fuel. Owing to some unique properties, sewage sludge differs from other solid fuels such as lignocellulosic biomass and coal, making its thermochemical conversion application somewhat complicated and challenging. This paper reviews the options of converting sewage sludge to energy and fuel via three main thermochemical conversion processes namely pyrolysis, gasification and combustion. The fundamental aspects of sewage sludge and its behaviour in each of thermochemical process are summarised. The challenges in adopting thermochemical conversion technology in sewage sludge management are addressed, and various alternative approaches deserving further consideration, such as the incorporation of pre-processing and co-utilisation, are discussed. [ABSTRACT FROM AUTHOR]

In this study, Raman mapping technique was developed to realize surface chemical imaging of single pulverized coal particles on a micron scale. Heterogeneity and its evolution during pyrolysis of the Zhundong pulverized coal particles were investigated. The results show that single pulverized coal particles have significantly different heterogeneity. There is a nonmonotonic relation between the heterogeneity degree and average chemical structures of the single pulverized coal particle. During pyrolysis, the structural evolution of various regions in a single pulverized particle differs from each other, especially at the early stage. The regions with more fluorescence-rich structures or small aromatic rings react earlier, and then the whole particle almost experiences a translational reaction. Besides, the heterogeneity of the single pulverized particles evolves differently for specific chemical structures, and the pyrolysis process can change but not eliminate the heterogeneity for various structures. [Display omitted] • Chemical imaging of single pulverized coal particle surface was realized by Raman mapping. • Pyrolysis process of single pulverized coal particle was traced and investigated. • Quantitative indexes for the heterogeneity of single coal particles were proposed. • Differentiation evolution paths of coal particles during pyrolysis were revealed. [ABSTRACT FROM AUTHOR]

To gain new insights into lignin pyrolysis, the synergistic development of carbon skeleton and pore networks in a wide temperature range of 200–800 °C was unraveled. The relative abundance of aromatic carbon structures increased exponentially with increasing temperature, as determined by 13C NMR deconvolution. Additionally, the g-factor type of radicals changed from O-centered (g-factor <2.0030) to C-centered (g-factor >2.0040) radicals. The evolution of the char macromolecules structure from disorder to order was principally characterized by a decrease in aromatic spacing (d 002 , 3.36→3.37 Å) an d an increase in stacking degree (L c , 7.89→8.67 Å) and aromaticity (f a , 75.19%→96.94%). f a h a s a strong negative linear correlation with d 002 (R 2 = 0.965). Ternary quadratic polynomials can relate specific surface area, total pore volume, and relative carbon content to the pore fractal dimension. The hypothesized chemical reaction networks and synergistic development of carbon skeleton and pore networks are essential for lignin effective valorization by a pyrolysis-based biorefinery strategies. [Display omitted] • The synergistic development of carbon skeleton and pore network was unraveled. • f a has a strong negative linear correlation with d 002. • Developed ternary quadratic polynomials link fractal dimension to SSA , TPV and C daf. • SSA and TPV were negatively correlated with d 002 , but positively correlated with f a. [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]

The catalytic pyrolysis of flame retarded high impact polystyrene (Br-HIPS) was performed in the presence of five different solid acid catalysts in order to remove the bromine from the derived pyrolysis oil. The catalysts were three zeolite materials (HY, Hβ and HZSM-5) and two mesoporous solids (all-silica MCM-41 and active Al 2 O 3 ). The results showed that in the presence of HY and Hβ zeolites, a reduction of approximate 50 wt.% in oil yield and a corresponding increase in wax and gas yields were obtained compared to thermal degradation. The addition of HZSM-5 showed less impact on product distribution and produced more oil compared with the other zeolites. The mesoporous catalyst of all-silica MCM-41 obtained the highest oil yield of 67.9 wt.% and reduced the wax yield to 8.73 wt.%. In terms of the composition of the pyrolysis oil, HZSM-5 and all-silica MCM-41 were favorable to produce more valuable single ring aromatics, such as toluene, ethylbenzene and cumene. Moreover, the catalysts exhibited pronounced debromination performance, especially the Hβ catalyst, achieving the debromination efficiency of 70.47%. The results confirmed the catalytic pyrolysis of Br-HIPS and debromination performance was well related to the textural properties of catalysts. [ABSTRACT FROM AUTHOR]

[Display omitted] • Co-pyrolysis was performed in a photothermal TG system under high heating rates. • Activation energy relative difference was used to quantify the synergistic effect. • Thermo-kinetic properties were significantly affected by high heating rates. The heating rate would significantly impact the pyrolysis process, especially for the reactions containing synergistic effects between two different feedstocks. Co-pyrolysis of two widely available biomass (CC–corncob and PS–peanut shell) with plastic (PET–polyethylene terephthalate and PVC–polyvinyl chloride) was studied in a concentrating photothermal thermogravimetric analysis (CP-TGA) system at three heating rates (100, 500, 1000℃/min). The TG and DTG curves of CC and PS differ due to their polymeric components (holocellulose and lignin); two pronounced levels at 100 and 500 ℃/min heating rates were present in PVC. With increasing heating rate, the lateral shift towards higher temperature regions in the TG and DTG curves exceeded 100 °C. The synergistic effects on the blend samples were concentrated in the main decomposition region (250–580℃) due to rapid volatiles release, and the discrepancy values further stabilized at the final decomposition stages. The activation energy (Ea) was assessed using a comparative study of isoconversional methods, namely Kissinger–Akahira–Sunose (KAS), Flynn–Wall–Ozawa (FWO), and Starink. The isoconversional methods demonstrated that the co-pyrolysis process required about 30 % less activation energy than the pyrolysis of plastic (PET/PVC) alone. Coats-Redfern's (CR) model-fitting approach was used to identify the kinetic triplet of the devolatilization stage. The CR models revealed that biomass–PET blends belong to two to four-dimensional diffusion models, whereas biomass–PVC blends are dominated by chemical reactions of 1.5 and 2 orders. The energy barrier between activation energy (Ea) and change in enthalpy (ΔH) for all the blend samples was lower (∼5–6 kJmol−1), which slightly increased at higher heating rate. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomass can be converted to biochar, bio-oil and gas through reactions of non-volatile stabilised free radicals (SFRs) and volatile radicals during thermal conversion. In the process, the interactions between radicals from different biomass components play an essential role. Figuring out the interactions of radicals during pyrolysis holds the key to revealing the interaction mechanism of biomass components. In this study, the evolution of SFRs during the co-pyrolysis of cellulose and lignin was explored using in-situ electron paramagnetic resonance (EPR) detection. The interactions of cellulose- and lignin-derived radicals were analysed based on the variation of SFRs, thermogravimetric behavior and Raman spectrum measurement. The results indicate that the interactions of radicals influence char yield, char structure and the SFRs evolution during pyrolysis. The interaction of volatile radicals and SFRs increases the char yield and promotes the condensation of aromatic structure in biochar. At temperatures above 400 °C, the interaction between cellulose- and lignin-derived SFRs leads to the coupling of radicals, which forms an unstable structure in the hot nascent biochar. In the subsequent cooling process, the weak bonds from interactions may break due to the structure shrinkage, which promotes radical reactions and further changes the char structure. • Interactions during co-pyrolysis improve char yield and stabilised radicals content. • The relationship between stabilised radicals and char carbon skeleton was studied. • The interaction of stabilised radicals in nascent char causes the radicals coupling. • The weak bonds from interaction break to promote radical reactions during cooling. [ABSTRACT FROM AUTHOR]

Waste fan blade would explosively grow with the life time of wind power machine is ended. Developing new low carbon-emission method to treat waste fan blade and achieving high resource recovery is promising. In this work, a novel photothermal pyrolysis method was developed and firstly applied to treat waste fan blade. A typical waste fan blade was cut, crushed and screened to separate base material and reinforcing fiber, whose mass ratio was 74.36:25.64. The base material was pyrolyzed at varied conditions of pyrolysis temperature, heating rate, gas flow rate respectively. The study showed that bisphenol A was significantly acquired in tars (relative contents were commonly over 40%), and its generation can be promoted by increasing pyrolysis temperature, heating rate and gas flow rare. The generation mechanism of bisphenol A was revealed during photothermal pyrolysis process: The main chain of 2,2-bis(4-glycidyloxyphenyl)propane resin in base material undergone random or chain cracking reaction to produce bisphenol A rigid skeleton, phenoxy, alkane, hydroxyl and other active groups. Bisphenol A rigid skeleton was the precursor of bisphenol A. Bisphenol A was formed after receiving hydrogen atoms, accompanied by the formation of tetrahydrofuran, 4,4-(propane-2,2-diyl)bis(methoxybenzene) and other substances. Bisphenol A undergone decomposition via secondary reactions, and it was mainly decomposed into phenol and 4-isopropylphenol, 4-isopropylphenol was then dehydrogenated to produce 4-isopropenylphenol. • Waste fan blade was firstly pyrolyzed using novel photothermal pyrolysis system. • High yield and relative content of bisphenol A was detected in pyrolytic oil. • Generation mechanism of bisphenol A during photothermal pyrolysis was revealed. [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]

Electronic waste plastics (e-waste plastics) have been one of the emerging and fastest-growing waste streams due to the increasing number of generation in waste electrical and electronic equipment (WEEE). Given that brominated flame retardant (BFR) materials in e-waste plastics have been the major impediment for recycling treatment, chemical recycling has been proposed as an environmentally friendly method of recycling e-waste plastics for clean fuels production or chemical feedstocks. This paper summarized the current techniques of BFR-plastics recycling with a view to solving energy crisis and the environmental degradation of BFR-plastics. Emphasis was paid on the recent chemical treatment of BFR-plastics, including pyrolysis, co-pyrolysis and catalytic cracking, which are yet to be completely feasible in conversion of BFR-plastics for clean fuels production. Hydrothermal treatment is regarded as a novel high-efficiency technology to recycle BFR-plastics, which can be a potential process for the in situ debromination of oil products. An advanced chemical recycling technique, pyrolysis-catalytic upgrading process, is highlighted. The recycling route of pyrolyzing BFR-plastics prior to catalytic upgrading was intended to obtain high quantity oils, and then the upgrading process of pyrolysis oils was conducted by means of catalytic hydrodebromination with the aim of obtaining bromine-free oils for commercial applications. In short, the integration of pyrolysis with catalytic upgrading process can provide significant economic and environmental options in conversion of e-waste plastics into useful and high-value materials. Further investigations are required to develop the pyrolysis-catalytic upgrading process to become sustainable and commercially viable for clean fuels production. [ABSTRACT FROM AUTHOR]

• A novel photothermal pyrolysis system was successfully built to treat waste tire. • High-yield limonene can be acquired with the photothermal pyrolysis of waste tire. • Waste tire photothermal pyrolysis and limonene generation mechanisms were found. Waste tire is a typical solid municipal waste with large production capacity. Developing new low carbon-emission method to pyrolyze waste tire and produce high-value limonene is promising. Herein, a novel photothermal pyrolysis system was successfully built, and waste tire was firstly pyrolyzed by photothermal at different temperatures (400 °C, 500 °C, 600 °C, and 700 °C). The photothermal pyrolysis can assist in achieving high yield of limonene, of which the yield can high up to 8.98 wt% at 600 °C and the relative peak areas of Gas Chromatography-Mass Spectrometer (GC–MS) results were all about 30 A.%. cis-1,4-polyisoprene in waste tire partly decomposed into some free radicals and they further reacted to generate limonene by intramolecular cyclization, dimerization, and isomerization. Parts of limonene aromatized to 1-methyl-4-(1-methylethenyl)-benzene and converted to triolefins that formed diene rings, the diene rings further aromatized to xylene and toluene, which were partly combined to generate 1,6,7-trimethyl-naphtalene. The photothermal pyrolysis mechanisms of waste tire were revealed: At higher pyrolysis temperature, waste tire partly decomposed and others polymerized to form amorphous carbons. The small aromatic rings and alkyl-aryl C C bonds further polymerized to be large aromatic rings system. The pores in char further formed and limonene generation was strengthened, because the limonene formation/decomposition was mainly limited in the pores. Subsequently, some pores were blocked at 700 °C, the generation of limonene was thus inhibited. [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]

• Char structure was investigated via characterization of its extraction and residue. • Effects of pellet sizes on char structure were weakened by temperatures. • Polymerisation of extract is account for the structural difference of pellet chars. • Aromatisation degree of pellet char is related to its surface-area-to-volume ratio. Char structure can reflect the pyrolysis characteristics and affect the efficiency of gasification and combustion processes, while biomass pellet size and shape are critical for the heat and mass transfer, which in turn influence greatly char structure. The aim of this study is to experimentally study and compare the effect of aspect ratio (diameter/length) on char structure during the pyrolysis of sawdust pellet. Cylindrical sawdust pellets with similar masses and volumes but different diameters (6, 8, 12, 16 mm) were pyrolysed at various temperatures. The chars were separated into two phases (liquid extraction, solid residue) via microwave-assisted extraction. Experimental results show that the pellet with a low aspect ratio had a large char yield because of intra-particle volatile-char interaction especially at low temperature, while there was an optimum aspect ratio due to the change of residence time. The pellet with a high aspect ratio had an intense polymerisation, resulting in the formation of fused aromatic rings in char and residue. By increasing aspect ratio, there was a lowest surface area. This means that less heat entered from surface, and low thermal conductivity caused a slow decomposition. Due to large heat and mass transfer residence, more aromatic molecules with small weight formed in extracts of char, especially at high temperature. Besides, an increase in temperature weakened the differences in structural features of the pellet char caused by different aspect ratios. [ABSTRACT FROM AUTHOR]