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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]

• 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]

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]

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]

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]

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]