Pyrolysis Products Research Articles

Nitrogen migration and transformation during the pyrolysis of corn straw with iron-based catalyst

The pyrolysis of renewable biomass into biofuels and high-value chemicals showcases remarkable application value and extensive market potential. However, the pyrolysis of biomass with high nitrogen content results in the production of NOX precursors that contribute to environmental pollution. Therefore, it is proposed to introduce iron-based catalysts to change the formation pathway of NOX precursors and control their production.The study elucidates the influence of iron-based catalysts on the conversion of nitrogen-containing products between gas, liquid and solid phases during corn straw pyrolysis. First, the effects of iron-based catalyst types on pyrolysis kinetics of corn straw were estimated using Thermogravimetry-mass spectrometry (TG-MS). Based on this, the effects of catalyst type and dispersion on the migration path of three-phase nitrogen-containing products were investigated, and the chemical morphology of the catalyst during pyrolysis was monitored by in-situ XRD to clarify the main catalytic active phase for N2 formation. Results showed that the addition of Fe, FeCl3 and Fe2O3 changed the distribution ratio of three-phase nitrogen-containing products, and the gas phase yield was significantly improved. Notably, the chemical form of Fe2O3 will change and transform into FeOOH, Fe3O4 and α-Fe during pyrolysis. It was confirmed that α-Fe was the main active phase for catalyzing the conversion of nitrogen-containing substances. Higher N2 conversion can be achieved by preparing high purity α-Fe. The mechanism is that α-Fe catalyzes the secondary decomposition of tar nitrogen into NH3 and HCN. Simultaneously, α-Fe reacts with char nitrogen, NH3, and HCN to form FeXN, which decomposes to produce environmentally friendly N2. The research findings offer theoretical guidance for the control of nitrogen pollutant emissions and the targeted acquisition of pyrolysis products (For example, NH3 can be used as a carbon-free hydrogen-rich fue).

Insight into carbon structures and pyrolysis behaviors of coal from the 13C CP/MAS NMR spectra

Carbon structures play an important role in the pyrolysis behavior of coal. Solid-state 13C nuclear magnetic resonance (NMR) spectroscopy is a powerful nondestructive technique for characterizing the carbon skeleton structures in coal. In this study, the carbon type distribution, lattice parameters, and chemical bond concentrations of six coal samples with different Vdaf values were investigated using 13C CP/MAS NMR spectra. Typical TGA and Py-GC-MS methods were utilized to obtain information on weight loss and pyrolysis products of the coals. The aromaticity of coal was determined by an adjustment of the apparent area ratio in the 13C CP/MAS NMR spectra, which shows promising potential for predicting key temperatures, characteristic index, and tar quality in coal pyrolysis. Results from the carbon fractions indicated that the total concentrations of chemical bonds in coal are approximately 150 mmol/g, with more Car−Car and Car−H bonds present in highly mature coal samples, and fewer Cal−Cal, Cal−H, and CO bonds. The breaking behaviors of chemical bonds during coal pyrolysis depend on a combination of temperature and concentration. The breakage of Cal−Cal bond contributes significantly to the pyrolytic weight loss of coal, accompanied by the decrease of Cal−H bonds along with the removal of aliphatic groups. Furthermore, as coal maturity increases, tar from fast pyrolysis contains more polycyclic aromatic hydrocarbons with a higher average molecular weight. The average number of aromatic rings in tar components is notably lower than that of aromatic clusters in coal. These results will contribute to a better understanding of the relationship between coal structure and reactivity, and may provide valuable insights for the efficient and clean utilization of coal.

Co-pyrolysis of pretreated cotton stalk and low-density polyethylene: Evolved products and pyrolysis mechanism analysis

The preparation of bio-oil from cotton stalks and agricultural residue films using co-pyrolysis technology can achieve resource recovery and energy conversion, which has important research value and significance. In this study, cotton stalks were subjected to different chemical pretreatments using NaOH, HCl, and H2O solutions to understand their structural changes and pyrolysis characteristics. In addition, the lower H/C ratio of cotton stalks resulted in higher oxygen content in the pyrolysis oil, which limited its efficient and clean utilization. Therefore, the characteristics and pyrolysis kinetics of the pyrolysis products of pretreated cotton stalks and LDPE (low-density polyethylene) were studied. The results showed that the ash content of alkali pretreatment cotton stalks decreased by 1.24 %, and the dense structure of cotton stalks significantly relaxed. NaOH pretreatment effectively removed hemicellulose sugars and cracked them. During the co-pyrolysis process, when the ratio of NaOH-CS/LDPE was 50/50, the synergistic effect was more pronounced, and the oil yield increased by 2 % compared to the theoretical value. The oxygen content of CO and CO2 in the pyrolysis gas was higher than the theoretical value, at 10.4 % and 14.1 % respectively. The synergistic effect of bio-oil on hydrocarbons was the most significant, reaching 18.9 %. More hydrogen and less oxygen migrated into the co-pyrolysis oil, resulting in an increase in hydrocarbons and a decrease in oxygen-containing compounds, and improving the quality of bio-oil. Results from electron paramagnetic resonance (EPR) indicated that adding LDPE might raise the quantity of stable free radicals. The evolution mechanism of functional groups of NaOH-CS and LDPE co-pyrolysis behavior was analyzed by Fourier in-situ infrared spectrometry (FTIR), and it was found that C–O–C, C=O, and O–H decreased due to dehydroxylation, decarboxylation, decarbonylation, and demethoxy reactions with the increase of temperature, indicating that there was a synergistic effect between NaOH-CS and LDPE co-pyrolysis. The pyrolysis kinetics of NaOH-CS, LDPE and their blends were determined by the model-free method. The introduction of LDPE can reduce the activation energy of NaOH -CS pyrolysis alone, and the 3D diffusion (D3) model is suitable for their blends.

Comparative analysis of additive decomposition using one-dimensional and two–dimensional gas chromatography: Part II - Irgafos 168 and zinc stearate

Plastic production has experienced a significant increase in the last sixty years due to its cost-efficiency and adaptable characteristics, leading to the extensive use of additives to improve its performance and longevity. Due to the high demand for plastic, plastic waste production has increased, contaminating the environment and living beings by leaching additives, among other substances. Pyrolysis stands out among recycling techniques because it can handle mixed polymer waste feedstock. However, understanding the pyrolyzates distribution of additives is fundamental to assessing pyrolysis process of plastic waste. This study investigated the pyrolysis product distributions of two commonly used antioxidants, namely, Irgafos 168 and zinc stearate (ZnSt), using one-dimensional gas chromatography equipped with a quadruple mass spectrometer (GC–MS) and two-dimensional gas chromatography coupled to flame ionization detector and time–of–flight mass spectrometer (GC×GC–FID/TOF–MS). While GC separation technique provided limited information on product distribution, GC×GC offered enhanced resolution and identification of the decomposition products. In the pyrolysis of Irgafos 168 at 550 °C, GC identified 18 products, while GC×GC identified 198 products, representing an increase of approximately 11-fold. Similarly, for ZnSt, GC identified 67 products, while GC×GC identified 434 products, representing a 6-fold increase. GC×GC identified decomposition products from 15 different chemical classes for Irgafos 168 and 16 chemical classes for ZnSt, compared to 4 and 11 chemical classes identified by GC, respectively. Phenols and their derivatives were the major chemical class in the decomposition products of Irgafos 168 with a yield of 9.51 wt.%. In contrast, olefinic products were the dominant ones for ZnSt, with a yield of 9.73 wt.%. The major decomposition product of Irgafos 168 and ZnSt was 2‑tert‑butyl‑methylphenol (C11H16O) and C6 olefin (C6H12) with yields of 3.88 wt.%, and 1.13 wt.%, respectively. Utilizing the GC×GC separation method improved the ability to identify decomposition products, which can ultimately lead to a better understanding of antioxidant degradation that occurs during the pyrolysis process. GC×GC also provided thorough characterization of minor and co-eluted products along with major antioxidant degradation products. Additionally, the decomposition product distribution of Irgafos 168 and ZnSt was also compared with the primary antioxidants, Irganox 1010, Irganox 1076, and BHT, studied in part 1. The analysis indicated that the olefinic chemical class was the predominant one in Irganox 1010, Irganox 1076, and ZnSt, while ketones were the major chemical class in the decomposition of BHT and phenolics had the highest yield in Irgafos 168.

Colored Radiative Cooling and Flame-Retardant Polyurethane-Based Coatings: Selective Absorption/Reflection in Solar Waveband.

The aesthetic demand has become an imperative challenge to advance the practical and commercial application of daytime radiative cooling technology toward mitigating climate change. Meanwhile, the application of radiative cooling materials usually focuses on the building surface, related tightly to fire safety. Herein, the absorption and reflection spectra of organic and inorganic colorants are first compared in solar waveband, finding that iron oxides have higher reflectivity in NIR region. Second, three kinds of iron oxides-based colorants are selected to combine porous structure and silicon-modified ammonium polyphosphate (Si-APP) to engineer colored polyurethane-based (PU) coating, thus enhancing the reflectivity and flame retardancy. Together with reflectivity of more than 90% in near-infrared waveband and infrared emissivity of ≈91%, average temperature drops of ≈5.7, ≈7.9, and ≈3.8°C are achieved in porous PU/Fe2O3/Si-APP, porous PU/Fe2O3·H2O/Si-APP, and porous PU/Fe3O4·H2O/Si-APP, compared with dense control samples. The catalysis effect of iron oxides in the cross-linking reaction of pyrolysis products and dehydration mechanism of Si-APP enable PU coating to produce an intumescent and protective char residue. Consequently, PU composite coatings demonstrate desirable fire safety. The ingenious choice of colorants effectively minimizes the solar heating effect and trades off the daytime radiative cooling and aesthetic appearance requirement.

Characteristics of Pyrolysis Products of California Chaparral and Their Potential Effect on Wildland Fires

The aim of this study was to investigate the pyrolysis of selected California foliage and estimate the energy content of the released volatiles to show the significance of the pyrolysis of foliage and its role during wildland fires. While the majority of the volatiles released during the pyrolysis of foliage later combust and promote fire propagation, studies on the energy released from combustion of these compounds are scarce. Samples of chamise (Adenostoma fasciculatum), Eastwood’s manzanita (Arctostaphylos glandulosa), scrub oak (Quercus berberidifolia), hoaryleaf ceanothus (Ceanothus crassifolius), all native to southern California, and sparkleberry (Vaccinium arboreum), native to the southern U.S., were pyrolyzed at 725 °C with a heating rate of approximately 180 °C/s to mimic the conditions of wildland fires. Tar and light gases were collected and analyzed. Tar from chamise, scrub oak, ceanothus and sparkleberry was abundant in aromatics, especially phenol, while tar from manzanita was mainly composed of cycloalkenes. The four major components of light gases were CO, CO2, CH4 and H2. Estimated values for the high heating values (HHVs) of volatiles ranged between 18.9 and 23.2 (MJ/kg of biomass) with tar contributing to over 80% of the HHVs of the volatiles. Therefore, fire studies should consider the heat released from volatiles present in both tar and light gases during pyrolysis.

How nitrate and ammonium impact soil organic carbon transformation with reference to aggregate size

While nitrogen (N) deposition and over-fertilization enrich N in soil, it is unclear how it impacts soil organic carbon (SOC) transformation at the aggregate scale. Herein, a 90-day study reveals the transformation mechanisms of SOC in soil aggregates under nitrate and ammonium enrichment conditions. Results showed that nitrate treatment (NT) and ammonium treatment (AT) significantly increased SOC content by 15.6 % and 18.9 %, respectively. In addition, NT increased SOC accrual in large macro-aggregates (LMA), while AT increased SOC accrual in small macro-aggregates (SMA) and micro-aggregates (MA). Further analysis of pyrolysis products showed that N enrichment drove the transformation of labile soil organic matter (SOM) composition into recalcitrant SOM, with polysaccharides declining from 19–30 % to 2–13 %, while lipids rose from 18–27 % to 33–45 %. LMA and SMA contained more aromatic compounds than MA. This is linked to the inhibition of the expression of C degradation function genes, while almost all genes encoding SOC degradation are down-regulated under N enrichment. In the meantime, NT increased the abundance of genes encoding the degradation of N-containing compounds in LMA. Moreover, NO3− enrichment exerted a higher inhibitory effect on labile SOC degradation while NH4+ enrichment substantially inhibited recalcitrant SOC. Finally, Random Forest analysis confirmed that N enrichment elevated the importance of N-containing compounds' metabolism, which diminished when the size of soil aggregates decreased. In contrast, the importance of genes encoding saccharides and cellulose metabolism increased in smaller aggregates. This study highlights that both N type and aggregate size were determining factors in shaping SOC transformation in the N enrichment process.

Thermal properties and decomposition products of modified cotton fibers by TGA, DSC, and Py–GC/MS

The thermal properties and pyrolysis decomposition paths of cotton fibers modified by different chemical treatments, a conventional functionalization with silane and a novel sulphation-phosphorylation approach, were studied. The effects on the fibers thermal behavior and decomposition products were investigated. The cotton fibers were characterized before and after the surface treatments by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and pyrolysis/gas chromatography–mass spectrometry (Py/GC–MS). Morphological investigation was also performed by SEM/EDS analysis to assess the treatment effects on the cotton fibers’ surface. The silanization increases the cotton hydrophobicity and thermal stability, changing the pyrolysis mechanism, favoring depolymerization over dehydration and charring. On the contrary, sulphation-phosphorylation methods cause a decrease in the onset temperature and an increase of fire resistance, and charring yield. Thermal decomposition temperatures, weight losses, and pyrolysis mechanisms and products, were fully analyzed. The results can open the way on the use of modified cotton fibers in industrial fields where fireproofing is strongly desired.

Qualitative and quantitative analysis of synthetic cannabinoids in e-liquids by pyrolysis–gas chromatography/mass spectrometry

Synthetic cannabinoids (SCs) are a series of synthetic substances that mimic the effects of natural cannabis and cause more serious toxicity and public safety issues. SCs, with a wide variety and fast update rate have become the most abused family of new psychoactive substances. A pyrolysis–gas chromatography/mass spectrometry method has been developed to qualitatively and quantitatively analyze SCs in e-liquids using pyrolysis products as analytical targets, which can effectively expand the detection range of SCs. In qualitative analysis, diluted e-liquids were pyrolyzed in the microfurnace at 800, 600, and 300 ℃, respectively, followed by separation and analysis through gas chromatography/mass spectrometry. SCs in the e-liquids were determined by both shared and characteristic pyrolysis products combined with the EI mass spectrometry of their parent compounds. ADB-BUTINACA and 5F-MDMB-PICA were successfully identified in five e-liquid samples seized by local police. Furthermore, five popular SCs in the illegal market, ADB-BUTINACA, 4F-ABUTINACA, 4CN-CUMYL-BUTINACA, 4F-MDMB-BICA, and 5F-MDMB-PICA, were quantitatively analyzed based on their characteristic pyrolysis products as the analysis targets. The results indicated that the linear range of ADB-BUTINACA was 2–200 μg/mL, while those of 4F-ABUTINACA and 4CN-CUMYL-BUTINACA were 1–200 μg/mL. For 4F-MDMB-BICA and 5F-MDMB-PICA, the linear range was 5–500 μg/mL. The linear correlation coefficients of determination of five SCs were greater than 0.994. The limit of detection (S/N=3) for five SCs was 0.25–2.50 μg/mL, and the limit of quantification (S/N=10) was 0.50–5.00 μg/mL. This quantitative method was applied to five positive samples in real cases. The results showed that the concentrations of ADB-BUTIANCA and 5F-MDMB-PICA in the positive samples were 751.32–4810.10 μg/mL and 1109.41 μg/mL, respectively. The current research provides a validated pyrolysis–gas chromatography/mass spectrometry method, with simple pre-treatment, fast operation and wide screening range, to accurately identify and quantify SCs in e-liquid samples without reference materials.

Preparation, mechanical properties and anti-oxidation behavior of lightweight porosity-controlled SiC(rGO, xZrB2) composite PDCs for thermal protection

Achieving well-balanced light weight with simultaneous improvement in mechanical and antioxidant properties of SiC-based composite polymer-derived ceramics (PDCs) for hypersonic vehicle components is still a huge challenge. Herein, lightweight SiC(rGO, xZrB2) composite PDCs were prepared via re-pyrolyzing ball-milling-induced ZrB2-SiC(rGO)p/polycarbosilane-vinyltriethoxysilane-graphene (PCS-VTES-GO, PVG) blends. Main reinforcements consist of ZrB2, ZrO2(ZrC), ZrOSi and SiO2/β-SiC phases, among which favorable compatibility enables enhanced bear loading performances and high-temperature oxidation resistance. Rigid SiC(rGO)p tightly links with flexible PVG pyrolysis products, and co-assembles into robust SiOxCy/Cfree(rGO) matrix in framework owing to plentiful Si-dangling bonds at their interfaces. More interestingly, interfacial ZrOSi/ZrC transition zone can augment structural disorder of ceramic network, give bridging effects, strengthen interfacial compatibility, and even hinder further crack propagation for self-densification. Particularly, SiC(rGO, 30%ZrB2) composite PDCs possess optimal hardness (6.49 GPa) and outstanding fracture toughness (5.77 MPa⋅m1/2). Porous SiC(rGO, 30%ZrB2) composite PDCs own stable structure integrity within 60-min testing under butane torch flame at 1300 °C. Self-healing protective SiO2-ZrO2 glass layer avoids destructive structure and timely covers defects, thus retains good mechanical performances. Such good synergistic reinforcement and multiscale design of porosity-controlled composite, realizes integration of lightweight/good load-bearing characteristics with improved oxidation resistance for thermal protection system (TPS) of hypersonic vehicles.

Spherical nanocrystalline ScYSZ thermal barrier material by a novel supersonic plasma spheroidization method: Simple synthesis and excellent performance

The performance of plasma sprayed thermal barrier coatings (TBCs) is strongly dependent on the quality of the feedstock powders, which usually are fabricated by conventional spray drying and multi-step sintering methods. In this work, a novel supersonic plasma spheroidization technology was employed to fabricate the spherical nanocrystalline Sc2O3-Y2O3 co-stabilized ZrO2 (ScYSZ) powder. The deformation process from the irregular powder to the spherical one was stimulated by the COMSOL phase field simulation. The results suggested that the original irregular pyrolysis products of ScYSZ precursors were aggregated into spherical powders by plasma spheroidization technology. The COMSOL simulations verified that the powder changed from irregular particles to spherical ones. The spheroidized ScYSZ particles exclusively consisted of non-transformed t’-ZrO2 phase and showed good fluidity, smooth surface and high apparent density, which were expected to have a broader application prospect in the field of TBCs and other ceramic coatings.

Waste Plastic Pyrolysis Industry: Current Status and Prospects

Pyrolysis is a technology that can produce pyrolysis oil by decomposing waste plastic, and has the advantage of being able to process contaminated waste plastic that is impossible to process with other technologies. In Korea, where the amount of waste plastic is increasing and natural resources such as fossil fuels are lacking, pyrolysis technology is attracting attention under the keyword ‘urban oil field’. The Ministry of Environment of the Republic of Korea announced a ‘plan to revitalize waste plastic pyrolysis’ to increase the proportion of waste plastic pyrolysis treatment from 0.1% in 2021 to 10% in 2030. The products of pyrolysis are both fuel and plastic raw materials, but the processing consumes significant energy. Therefore, as criticism continues that the marketability and economic feasibility of pyrolysis technology is poor, questions are being raised about its environmental friendliness. Against this background, this study investigated international trends in pyrolysis technology and performed a detailed comparative analysis with other technologies from an environmental perspective. According to the results of this study, currently environmentally advanced countries are very negative about using pyrolysis oil as fuel, and the following policy directions are suggested. 1) In order to comply with the mandatory use ratio of plastic recycled raw materials and at the same time achieve eco-friendliness, it is recommended to use pyrolysis technology as a plastic recycled raw material production technology rather than fuel conversion. 2) Since pyrolysis emits more greenhouse gases than physical recycling, pyrolysis technology is used as a complementary method to physical recycling to process waste plastics that are difficult to physically recycle. 3) Since physical recycling is very important in the resource circulation of waste plastic, the development of separation and sorting technology is promoted nationally.

The Potential Significance of Microwave-Assisted Catalytic Pyrolysis for Valuable Bio-Products Driven from Albizia Tree

The objective of this study is to investigate the feasibility of Na2CO3 and ZSM-5 as catalysts in the microwave pyrolysis of Albizia branches. An evaluation was conducted to determine the influence of power applied, experimental time, particle size, and catalysis type and ratio on the quality and quantity of pyrolysis products. Established methods such as GC-MS, FTIR, HHV, SEM, EDX, and BET were used to characterize the properties of bio-oil and biochar produced. The results demonstrated that using both catalyst types led to a substantial enhancement in biogas production. The improvement ranged from 5% to 41% with Na2CO3 and reached 45% with ZSM-5. At a lower power level of 300 W, the bio-oil yield augmented from 28% to 40% and 53% when using ZSM-5 and Na2CO3, respectively. The GC-MS analysis revealed that the utilizing of catalysts enhanced the levels of aromatic compounds, esters, and alcohols in bio-oil, along with an increase in the higher heating value (HHV) from 19.5 MJ/kg to 22 MJ/kg and 24.2 MJ/kg using Na2CO3 and ZSM-5, respectively. Moreover, the biochar's surface area and pore volume experienced a considerable rise, going from 0.5512 m2/g and 0.00011 cm3/g to a higher value of 115.2073 m2/g and 0.0774 cm3/g when treated with Na2CO3. The data indicated that both catalyst types enhanced the generation of CH4, and CO2 was lower with ZSM-5. The utilization of catalysts improves the quality of the biofuel produced and promotes the efficiency of the process in terms of energy consumption and processing time.

Properties and combustion characteristics of bioslurry fuels from agricultural waste pyrolysis

ABSTRACT The current research investigates the combustion characteristics of bioslurry fuel derived from the products of agricultural waste pyrolysis. The bioslurry fuel was prepared by mixing biochar and pyrolysis oil. The combustion characteristics of a suspended single droplet of the bioslurry were analysed. The results indicate that an increase in pyrolysis temperature (400–600°C) lead to higher concentrations of fixed carbon (56–60%), increased ash content (16–18%), and higher calorific values (25–32 MJkg−1). As the pyrolysis temperature rises, the biochar surface becomes more porous, lower volatile matter content and particle size. As biochar content increases, the bioslurry’s density, viscosity, and caloric value increase but stability index decreases. Higher biochar content in the bioslurry increases the ignition delay and burnout time while reducing the burning rate. The bioslurry fuel contained 30% biochar achieved a calorific value of 28 MJkg−1 and a viscosity of 600 cP, comparative to conventional fossil fuels. Highlights Up to 30% BC can be added to pyrolysis oil to produce SF. Pyrolysis temperature increased FC, ash, and calorific value of biochar. Biochar surface appears more porous with increasing pyrolysis temperature. Biochar content affects bioslurry combustion characteristics.

Ex-situ catalytic fast pyrolysis of waste polycarbonate for aromatic hydrocarbons: Utilizing HZSM-5/modified HZSM-5

Catalytic pyrolysis has been proven as a highly efficient process for transforming waste polycarbonate (PC) into valuable aromatic hydrocarbons, especially benzene, toluene, ethylbenzene, and xylene (BTEX). In the present work, the ex-situ catalytic fast pyrolysis of PC on metal- or alkali-modified HZSM-5 was investigated using the double micro-fixed bed system. Experimental results indicate that the rapid pyrolysis of PC may follow a homolytic chain scission mechanism, resulting in pyrolysis products dominated by phenols. Metal- or alkali-modified HZSM-5 significantly enhances the cleavage of C-OH bonds in phenols, improving the yield of aromatics. The yield of aromatics in the liquid product is 91 %, 72 %, and 77 % when loaded with nickel (Ni), iron (Fe), and cobalt (Co), respectively, all of which are higher than unmodified HZSM-5 with the yield of 43 %. Among them, the Ni/HZSM-5 has significantly enhanced the yield of BTEX reaching 81.64 %. When using alkali-modified HZSM-5 with a larger pore volume and higher specific surface area, the yield of aromatics can be increased to 60 %. Furthermore, the dual modification of alkali treatment and Ni loading on HZSM-5 simultaneously enhanced catalytic activity and resistance to coke formation. The yield of BTEX reaches 94.47 %. The BTEX formation mechanism can be explained by direct deoxygenation (DDO) of the pyrolytic volatiles of PC and the “phenol pool” mechanisms of primary products on the catalyst surface. This study enriches the understanding of catalytic pyrolysis of PC and provides a theoretical foundation for the harmless treatment of PC.

Energy recovery from syngas and pyrolysis wastewaters with anaerobic mixed cultures

The anaerobic digestion of aqueous condensate from fast pyrolysis is a promising technology for enhancing carbon and energy recovery from waste. Syngas, another pyrolysis product, could be integrated as a co-substrate to improve process efficiency. However, limited knowledge exists on the co-fermentation of pyrolysis syngas and aqueous condensate by anaerobic cultures and the effects of substrate toxicity. This work investigates the ability of mesophilic and thermophilic anaerobic mixed cultures to co-ferment syngas and the aqueous condensate from either sewage sludge or polyethylene plastics pyrolysis in semi-batch bottle fermentations. It identifies inhibitory concentrations for carboxydotrophic and methanogenic reactions, examines specific component removal and assesses energy recovery potential. The results show successful co-fermentation of syngas and aqueous condensate components like phenols and N-heterocycles. However, the characteristics and load of the aqueous condensates affected process performance and product formation. The toxicity, likely resulting from the synergistic effect of multiple toxicants, depended on the PACs’ composition. At 37 °C, concentrations of 15.6 gCOD/gVSS and 7.8 gCOD/gVSS of sewage sludge-derived aqueous condensate inhibited by 50% carboxydotrophic and methanogenic activity, respectively. At 55 °C, loads between 3.9 and 6.8 gCOD/gVSS inhibited by 50% both reactions. Polyethylene plastics condensate showed higher toxicity, with 2.8 gCOD/gVSS and 0.3 gCOD/gVSS at 37 °C decreasing carboxydotrophic and methanogenic rates by 50%. At 55 °C, 0.3 gCOD/gVSS inhibited by 50% CO uptake rates and methanogenesis. Increasing PAC loads reduced methane production and promoted short-chain carboxylates formation. The recalcitrant components in sewage sludge condensate hindered e-mol recovery, while plastics condensate showed high e-mol recoveries despite the stronger toxicity. Even with challenges posed by substrate toxicity and composition variations, the successful conversion of syngas and aqueous condensates highlights the potential of this technology in advancing carbon and energy recovery from anthropogenic waste streams.Graphical

Distribution and characterization of products obtained from pyrolysis of cooked food waste- Impact of heating rate

This work offers a comprehensive investigation of the pyrolysis products—liquid, gas, and solid derived from cooked food waste (CFW) at different heating rates (15–100 °C/min). The heating rate significantly influenced the yield of pyrolysis products. The maximum yield of bio-oil (oil + aqueous) was achieved at a heating rate of 50 °C/min, py-gas at 100 °C/min, and biochar at 15 °C/min. The yields were 34 wt% for bio-oil, 30 wt% for py-gas, and 32 wt% for biochar. Analysis of the bio-oil revealed significant proportions of fatty acids (Methyl-methyltetradecanoate) and esters (Oleic acid ethyl ester), constituting 25 %, and 26 % at 15 °C/min but declining with increasing heating rates. Another ester (9-Octadecenoic acid methyl ester) was found across all heating rate with highest concentration of 33 % at 100 °C/min. Aliphatic hydrocarbons (Octane, Dodecene, Heptadecane, Tetradecyne, Undecane, Dimethylhepta-1,3-triene, Tetradecane, Nonadecane), constituted highest concentration of 12 % at 25 °C/min and aromatic hydrocarbons (Toluene) showed maximum presence of 4 % at 50 °C/min. The aqueous phase showcased cyclic nitrogenated compounds (Piperidine), anhydrosugars (DGP), and furanics (Furanmethanol), with the highest concentrations of 46 %, 12 %, and 38 %, respectively observed at 100 °C/min. Instantaneous py-gas analysis indicated an elevated presence of CO2 and CO in the initial pyrolysis stages (up to 70 min) followed by higher H2 in the latter stages (>70 min). While increasing heating rates (15–100 °C/min) boosted cumulative fractions of CO2 and CO, the highest H2 fraction was observed at 50 °C/min. The proximate and ultimate analysis of biochars indicated increased ash, fixed carbon, HHV and H/C compared to raw CFW. The surface area and morphology were positively influenced by an increase in heating rate, resulting in a microporous biochar having maximum surface area of 340.6 m2/g at 50 °C/min.

An experimental and mechanism study on the pyrolysis of sulfur mustard

Experimental studies on the pyrolysis of sulfur mustard (HD) were conducted from 673 to 1473 K using Py-GC/MS combined with two separate columns. The HD pyrolysis rate exceeded 99 % at a pyrolysis time of approximately 2 seconds above 1073 K. The pyrolysis products of HD mainly include ethylene, vinyl chloride, carbon disulfide, thiophene, hydrogen chloride and hydrogen sulfide. The main reaction mechanism of HD pyrolysis was investigated using quantum chemistry methods combined with the TST/VTST theory. At 673 K, the initial reaction pathway of HD primarily involves an intramolecular HCl elimination and the cleavage of the C-S bond. The radical reactions will dominate the pyrolysis of HD once radical pool is formed. The reaction pathways of the important radical intermediates were analyzed, and the formation mechanisms of the main pyrolysis products were investigated. Theoretically, the high-pressure limit rate constants for the major reactions were calculated. This study contributes to a deeper understanding of the HD pyrolysis mechanism and provides a theoretical and data foundation for the destruction of HD.

Insight into catalytic effects of alkali metal salts addition on bamboo and cellulose pyrolysis

Alkali metal compounds have vital influence on biomass pyrolysis conversion. In this study, cellulose, and bamboo catalytic pyrolysis with different alkali metal salts catalysts (KCl, K2SO4, K2CO3, NaCl, Na2SO4, and Na2CO3) were investigated in the fixed-bed reaction system. The effects of cations (K+ and Na+) and anions (Cl-, SO42−, and CO32-) on the evolution properties of biochar, bio-oil, and gas products were explored under both in-situ and ex-situ catalytic pyrolysis. Results showed that alkali metal salts facilitated the yields of biochar and gases at the expense of that of bio-oil. Alkali metal chloride and sulfate showed a weaker catalytic effect, while alkali metal carbonate greatly promoted the generation of gas products and increased the condensation degree of biochar. With the addition of K2CO3 and Na2CO3, cyclopentanones content was over 50% from cellulose catalytic pyrolysis, and phenols content (mainly alkylphenols) reached over 80% from bamboo catalytic pyrolysis. Moreover, solid-solid catalytic reactions with K2CO3 and Na2CO3 catalysts had an important role in strikingly promoting conversion of pyrolysis products, and the solid-solid and gas-solid catalytic reactions with alkali metal carbonate catalysts were stronger than those with alkali metal chloride and sulfate catalysts. Furthermore, the possible catalytic pyrolysis mechanism of alkali metal salts on biomass pyrolysis was proposed, which is important to the high-value utilization of biomass.

Characteristics of granulated activated carbon from a mixture of plant raw material waste

Relevance. The need to increase the use of renewable energy sources in the economy to reduce the harmful effects on the environment. Aim. To assess the possibility of obtaining by the thermochemical method high-quality carbon adsorbents from a granular mixture of various wastes of plant origin. Objects. Samples of illiquid lumpy birch wood, walnut shells, sunflower seed husks, flax fires, anthracite coal. Methods. Physical experiments: conductive pyrolysis, water-steam activation and differential thermal analysis. The ash content and moisture content of the samples were determined according to SS R 56881-2016 and SS 33503-2015. Nitrogen adsorption isotherms were measured using a NOVA-1200e analyzer. The equilibrium activity for toluene was determined according to SS 8703-74, the adsorption activity for iodine was determined according to SS 6217-74. The determination of the density of the granules was carried out according to SS 15139-69. Results. The authors have established rational parameters for obtaining carbon adsorbents from granules of vegetable raw materials. The specific yield of pyrolysis products of a mixture of vegetable raw materials with pyrolysis resin was determined. The specific yield of carbonization products of the granular compacted mass showed an increase of 25% in comparison with the non-compacted mixture of vegetable raw materials. Rational parameters for obtaining activated carbon with the highest adsorption capacity are granules with a density of 1200 kg/m3 with a degree of burnout of the carbonization product of 70%. It was established that the obtained samples of adsorbents from granules of plant raw materials have high adsorption characteristics comparable to activated carbons obtained from fossil raw materials.