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Volatile organic compounds (VOCs) in cooking oil fumes need to be efficiently removed due to the significant damage they cause to the environment and human health. This review discusses the emission characteristics, which are influenced by different cooking temperatures, cooking oils, and cuisines. Then, various cooking oil fume purification methods are mainly classified into physical capture, chemical decomposition, and combination methods. VOCs removal rate, system operability, secondary pollution, application area, and cost are compared. The catalytic combustion method was found to have the advantages of high VOC removal efficiency, environmental protection, and low cost. Therefore, the last part of this review focuses on the research progress of the catalytic combustion method and summarizes its mechanisms and catalysts. The Marse-van Krevelen (MVK), Langmuir-Hinshelwood (L-H), and Eley-Rideal (E-R) mechanisms are analyzed. Noble metal and non-noble metal catalysts are commonly used. The former showed excellent activity at low temperatures due to its strong adsorption and electron transfer abilities, but the high price limits its application. The transition metals primarily comprise the latter, including single metal and composite metal catalysts. Compared to single metal catalysts, the interaction between metals in composite metal catalysts can further enhance the catalytic performance. [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]

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

The chemical structures of pyrolytic chars prepared from 32 kinds of Chinese coals were investigated with micro-Raman spectroscopy in this study. Both first-order and second-order Raman spectra of the chars were curve-fitted and analyzed. The effects of the parent coal properties, including coal rank, volatile, fixed carbon, and ash content, on the pyrolytic char structures were detailed discussed and the correlations between these coal properties and pyrolytic char chemical structures were set up. Multiple-factor analysis was done to propose a comprehensive coal property index that relates well to the pyrolytic char chemical structure. The results indicate that the aromatization degree is the key distinguishable structure of pyrolytic chars prepared from coals with various rank, and the alkyl C−H and aryl C−H structures have no significant difference. The aromatization degree of pyrolytic char decreases with the increase of coal rank, while it increases with the increase of the fixed carbon content in parent coals. The high content of moisture in parent coal can induce condensation of the pyrolytic char, but the inorganic composition probably prevents the condensation of the char. Limited correlations between the coal rank, fixed carbon, moisture and ash content, and the aromatization degree of pyrolytic chars were found. A comprehensive coal property index: (fixed carbon content + moisture content)/(volatile content + ash content) (in air dry basis) combining the coal properties together relates well to the aromatization degree of pyrolytic char and can act as a good indicator for the pyrolytic char chemical structure. This study reveals the effects of the parent coal properties, including coal rank, fixed carbon, moisture, and ash content, on the pyrolytic char chemical structure, and provides a new comprehensive coal property index to predict the pyrolytic char chemical structure. [ABSTRACT FROM AUTHOR]

Sludge contains a high content of phosphorus (P) which makes the recovery of P from this material attractive. Inorganic apatite phosphorus (AP) could be utilized as a slow-release P fertilizer in a long term, thus transforming P-containing compounds into AP is greatly attractive. Herein, the migration and transformation behaviors of P from two municipal sewage sludge and a food-processing sludge were investigated during pyrolysis, and the effects of two calcium-based conditioners (CaO and CaCl 2) on the formation of AP were explored. The results showed that nearly all P remained in sludge below 650 °C but around 22.5–49.0% P released from that at 850 °C, respectively. CaO helped retain phosphorus in sewage sludge at 850 °C, while CaCl 2 facilitates its volatilization. Even though, the generation of AP was still improved under the effect of CaCl 2. AP amount increased by 7.1–37.5% in food sludge derived char while AP amount increased by 7.3% to 21 times in sewage sludge derived char because of the two calcium-based conditioners. Model experiments showed that CaO could react with non-apatite inorganic phosphorus (NAIP) to generate calcium pyrophosphate and calcium orthophosphate, and CaCl 2 could react with NAIP to form calcium pyrophosphate, calcium chlorapatite and phosphide. In general, CaCl 2 exhibited a more excellent effect on the formation of AP than CaO while CaO showed more stable performance on the retention of TP. [Display omitted] • CaO showed more stable ability to help retain phosphorus for all the samples. • CaCl 2 helped retain phosphorus in the char for food sludge but not sewage sludge. • CaO and CaCl 2 facilitated AP formation regardless of temperatures and sludge type. [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]

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

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

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

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

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

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

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

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