Pyrolysis Gas Chromatography Research Articles

Investigation of Peat Pyrolysis Products by Pyrolytic Gas Chromatography

Investigation of Peat Pyrolysis Products by Pyrolytic Gas Chromatography

Study on pyrolysis process and mechanism of organic coating of waste polyesterimide enameled wire based on density functional theory

The pyrolysis treatment of waste polyesterimide enameled wire offers significant advantages such as continuous processing, non-hazardous nature, and high resource recovery rate. However, research on its pyrolysis process and mechanism remains insufficiently explored. In this study, techniques including thermogravimetry (TG), Fourier transform infrared spectroscopy(FT-IR), pyrolysis–gas chromatography-mass spectrometry(Py-GC/MS) were employed to investigate pyrolysis temperature, weight loss rate, pyrolysis and kinetic parameters, composition and distribution of pyrolysis products, and changes in functional groups under different temperatures and heating rates. The pyrolysis of polyesterimide enameled wire can be divided into three stages: volatilization of specific components (314.8 °C,1.6 %), rapid decomposition of polyesterimide (435.2 °C, 44.7 %), and generation of small organic molecules with the fixation of pyrolytic carbon (750 °C, 9.0 %). The main components of the pyrolysis gas products include aromatic compounds, ethers, aromatics, ketones, and carbon dioxide. At 400 °C, a substantial amount of pyrolysis gas products and free radicals are produced, with an increase in aromatic hydrocarbons. The carbon distribution in the pyrolysis products mainly focuses on C6-C10 and C11-C15, and many organic compounds such as benzoic acid, phenol, and aniline are generated. Based on density functional theory, the bond dissociation energies in the polyesterimide were calculated. This clarified the possible thermal decomposition pathways of the polyesterimide and provided the energy barrier values, elucidating the generation mechanism of pyrolysis products during thermal decomposition. The copper atom in specific location reduces the negative ESP of O and increases the positive ESP of H in EPI, which makes H more likely to attach to O. The presence of Cu increases the ESP range and promote the pyrolysis process. This study provides a theoretical basis for the high-value recycling of waste polyesterimide enamelled wire.

Modification mechanism of caking property of polystyrene waste using low-temperature pyrolysis and its use in coal-blending coking

Polystyrene (PS) waste was depolymerized using a low-temperature pyrolysis treatment (LTPT) to increase its caking index. The mechanism of caking index modification was revealed by using Fourier transform infrared spectroscopy, thermogravimetric (TG) analysis, pyrolysis-gas chromatography with mass spectrometric detection, and solid-state 13C nuclear magnetic resonance spectroscopy. The crucible coal-blending coking tests were carried out using an industrial coal mixture and the treated-PS with the highest caking index (PS300) or raw PS. Some properties of the resultant cokes were also analyzed. It was demonstrated that the caking index of PS dramatically increased by LTPT; however, exceeding 300 °C did not yield any benefit. The caking index increased due to the formation of the caking components, whose molecules are medium in size, caused by LTPT. Additionally, the coke reactivity index of the coke obtained from the mixture containing PS300 decreased by 5.1% relative to that of the coke made from the mixture with PS and the coke strength after reaction index of the former increased by 7.3% compared with that of the latter, suggesting that the ratio of depolymerized PS used for coal-blending coking could increase relative to that of PS.

Biochar as a UV Stabilizer: Its Impact on the Photostability of Poly(butylene succinate) Biocomposites.

In the present study, biocomposite materials were created by incorporating biochar (BC) at rates of 1, 2.5, and 5 wt.% into a poly(butylene succinate) (PBSu) matrix using a two-stage melt polycondensation procedure in order to provide understanding of the aging process. The biocomposites in film form were exposed to UV irradiation for 7, 14, and 21 days. Photostability was examined by several methods, such as Fourier transform infrared spectroscopy (FTIR), which proved that new carbonyl and hydroxyl groups were formed during UV exposure. Moreover, Differential Scanning Calorimetry (DSC) measurements were employed to record the apparent UV effect in their crystalline morphology and thermal transitions. According to the molecular weight measurements of composites, it was apparent that by increasing the biochar content, the molecular weight decreased at a slower rate. Tensile strength tests were performed to evaluate the deterioration of their mechanical properties during UV exposure, while Scanning Electron Microscopy (SEM) images illustrated the notable surface alternations. Cracks were formed at higher UV exposure times, to a lesser extent in PBSu/BC composites than in neat PBSu. Furthermore, the mechanism of the thermal degradation of neat PBSu and its biocomposites prior to and upon UV exposure was studied by Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS). From all the obtained results it was proved that biochar can be considered as an efficient UV-protective additive to PBSu, capable of mitigating photodegradation.

Towards quantitative microplastic analysis using pyrolysis-gas chromatography coupled with mass spectrometry

Microplastic pollution from everyday plastic items has increased tremendously worldwide. Pyrolysis gas chromatography coupled to mass spectrometry (Py-GC/MS) has been widely investigated for the qualitative and quantitative analysis of microplastics in environmental samples. However, there are several pitfalls to consider when developing an appropriate protocol for their analysis. This study aimed at the development of an in-house database of primary (single) polymers, binary (two) polymers and tertiary (three) polymer mixtures. In this context the potential occurrence of gas phase reactions during pyrolysis of binary and tertiary polymers were investigated. Further, different diluters were tested for the accurate preparation of calibration standards for quantification purposes.Seven different polymers were included in this study, which were chosen due to their prevalence in daily plastic appliances. For each single polymer specific peaks could be identified and recommendation for quantifier analytes given. The analysis of binary polymer mixtures revealed gas phase reactions for PET with PVC, PVC with MDI-PU and PE with PVC. For these binary polymers, several different novel pyrolysis products, specific for the according binary polymer mixture, could be identified. These results confirmed that especially PVC exhibits strong interactions during co-pyrolysis with ester- and ether-based polymers. Similar results were obtained for tertiary polymers.For accurate preparation of calibration standards different diluters (silica, deactivated silica, calcium carbonate, THF and HFIP) were tested. It was observed that deactivated silica had only an influence on the pyrolysis of PET. Whereas, dilution with silica affected PA-6/66, PE, PET and MDI-PU. Only PVC was not influenced by dilution with silica.In conclusion, our results highlight the necessity of an international standard of reference material as well as a standardized analytical protocol for the analysis and quantification of polymers in environmental samples. It is crucial to use diluters suitable for the specific polymer, to exclude potential interactions of diluters with the polymer. The present work has to be seen as a foundation, but future work is needed to adequately address the quantification of polymers in environmental samples.

Pyrolysis behavior of sewage sludge coexisted with microplastics: Kinetics, mechanism, and product characteristics

Microplastics can accumulate in the excess sludge from wastewater treatment plants through domestic wastewater. This study investigated the co-pyrolysis behavior of sewage sludge coexisting with two types of microplastics (polyethylene (PE) and polylactic acid (PLA)) and found a superior comprehensive pyrolysis performance. By calculating the difference between theoretical and experimental weight loss during the pyrolysis process, it was found that the incorporation of microplastics PE and PLA created a synergistic effect at 270°C–450 °C, which was confirmed through the Malek method analysis from a pyrolysis mechanism perspective that it could increase the random nuclei on each particle, that is, enhance the heterogeneous diffusion of volatiles. The average activation energy was reduced by 84.99 kJ/mol, as determined using three isoconversional methods: Flynn-Wall-Ozawa (FWO), Kissinger-Akahira-Sunose (KAS), and Starink. Regarding the products, the aforementioned synergistic effect led to a reduction in char retention and larger specific surface area of the biochar, while the quantities of gaseous products and bio-oil escalated. Through a thermogravimetric analyzer and Fourier transform infrared spectroscopy (TG-FTIR), an increase in aromatic hydrocarbons, alkanes, aldehydes, ethers, and esters in the gaseous products were detected. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) revealed an increase in hydrocarbons, esters, and alcohols in the bio-oil, and acids and aldehydes decreased, overall enhancing the quality of the bio-oil. This study elucidated that pyrolysis completely transformed microplastics in sludge, thus eliminating environmental risks and provided a theoretical reference for understanding the pyrolysis behavior of sludge containing microplastics.

The Influence of Planting Sites on the Chemical Compositions of Chrysanthemum morifolium Flowers (Chuju) as Revealed by Py-GC/MS Combined with Multivariate Statistical Analysis.

Chuju, a cultivar of Chrysanthemum morifolium, has been traditionally cultivated for over 2000 years in China for both ornamental and medicinal purposes. To date, investigations into the chemical composition of this plant have indicated that it contains compounds with extensive biological activities, although detailed information on the chemical composition of Chuju remains scarce. In the present study, the chemical compositions of Chuju flowers were investigated across five sites in the core Chuju planting area in Anhui province, China. Analytical pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was used to explore variations in flower chemical fingerprints from different Chuju planting sites. The study identified approximately 200 components in Chuju flowers and stems, including high levels of fatty acids, lipids, polysaccharides and terpenoids. Multivariate statistical analysis indicated that 16 chemical compounds were influential determinants of the chemical fingerprint and could be used to distinguish two clusters in the five core planting areas. The established Py-GC/MS analytical workflow could provide a basis for determining the chemical fingerprints of Chuju and help elucidate that products contain a reproducible content of bioactive compounds and overall quality for potential development of health and medicinal purposes.

Association between blood microplastic levels and severity of extracranial artery stenosis

Microplastics (MPs) contamination raises concerns about their impact on human health, particularly cardiovascular diseases. This study investigated the blood MPs levels in patients with extracranial artery stenosis (ECAS) and their possible link to disease severity. 20 ECAS and 10 control patients were recruited. Blood samples, collected before the digital subtract angiography (DSA) procedure, were analyzed by pyrolysis–gas chromatography mass spectrometry (Py-GC/MS), laser direct infrared (LDIR) spectroscopy, and scanning electron microscopy (SEM). Demographic and clinical information was also examined. Strict quality controls were implemented to prevent contamination. MPs were detected by Py-GC/MS in all blood samples, with concentrations significantly higher in ECAS group compared to control (174.89 ± 24.95 vs 79.82 ± 31.73 μg/g, p < 0.001), and polyvinyl chloride (PVC) and polyamide 66 (PA66) were the most abundant among the detected polymers. Further analyses suggested that higher concentrations of MPs may be associated with more severe artery stenosis (p < 0.001). Compared with the normal group, ECAS group had a higher level of D-dimer (0.61 ± 0.6 μg/L vs 0.28 ± 0.09 μg/L, p < 0.05) and longer Thrombin Time (sec) (18.30 ± 3.43 μg/L vs 16.25 ± 1.74 μg/L, p < 0.05). Additionally, LDIR and SEM detected the shape and physical properties of the MPs. In this study, we revealed significant higher blood MPs levels in ECAS patients, with a notable correlation between MPs concentrations and arterial stenosis severity.

High-Speed Removal Process for Organic Polymers by Non-Thermal Atmospheric-Pressure Spark Discharge at Room Temperature and Its Mechanism

Heel marks (HMs) are a type of dirt stain consisting of polyester-based urethane rubber on polyvinyl chloride (PVC) floor surfaces. The rapid removal of HMs was achieved by using non-thermal atmospheric-pressure plasma technology. Mimetic HMs were prepared by coating PVC floor samples with HMs to a thickness of 13.9 μm. The removal area, thickness, and volume were measured after applying spark discharges at high voltage and a repetition rate of 50 kHz. The treated surfaces were analyzed by using X-ray photoelectron spectroscopy (XPS) and pyrolysis–gas chromatography with time-of-flight mass spectrometry (Py-GC/TOFMS). Removal rates of 20 mm2/min in area, 52 mm3/min in volume, and 7 μm/min in depth were achieved with an inter-electrode distance of 10.0 mm and an air flow rate of 20 standard liters per minute. A removal depth of 10 μm/min was achieved without air supply. The mechanism of stain removal by spark discharge was modeled by decomposing the original high-molecular-weight molecules in polyester-based urethane rubber into low-molecular-weight molecules, such as methylene diisocyanate (MDI) components. The results of this study may facilitate the development of a novel electric vacuum cleaner capable of removing floor stains.

Abiotic degradation and accelerated ageing of microplastics from biodegradable and recycled materials in artificial seawater

Microplastics (MPs) are considered one of the most widespread pollutants in all ecosystems worldwide. In the environment, MPs can undergo hydrolysis and/or oxidation, resulting in the release of low-molecular weight degradation products, along with additives, and adsorbed organic pollutants. In this study, the morphological, chemical, and thermal changes of microplastics obtained from two biodegradable plastics, polylactic acid and Mater-Bi®, and a recycled plastic, recycled-polyethylene terephthalate, were examined after accelerated ageing under photo-oxidative conditions in synthetic seawater in a Solarbox system, and after thermal treatment in the dark. Thermal properties were studied by thermogravimetric analysis, differential scanning calorimetry, and evolved gas analysis-mass spectrometry. Compositions and changes of chemical components of the polymers were evaluated by attenuated total reflection-Fourier transform infrared spectroscopy and pyrolysis-gas chromatography–mass spectrometry. The leachable fractions and degradation products released in synthetic seawater by degraded MPs were characterized by gas chromatography–mass spectrometry. This study allowed us to identify hydrolysis as the main degradation pathway of the polymers under analysis, and to characterize not only the oligomers and degradation products released in the water as a consequence of degradation, but also additives used in plastic item formulations. This study improves our understanding of these polymers' behavior under accelerated ageing conditions.

Identification of conservation and restoration materials for iron relics through ultraviolet-induced visible luminescence imaging and pyrolysis-gas chromatography/mass spectrometry

Understanding the previous protection and restoration efforts and the current state of cultural relics is essential before compiling a conservation and restoration plan. The lack of detailed archival records for some early conservation operations, the identification of restoration materials necessitates the use of scientific analytical methods. In this study, the composition and spatial distribution of historical restoration materials on five iron relics were investigated through pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and ultraviolet-induced visible luminescence imaging (UVL). The relics studied were iron weight 20791, iron adze head 2335, and iron axe 2334 from the Gansu Provincial Museum, iron sword D0008 from the Zhaotong Municipal Museum, and iron sword 450 from the National Museum of China. All five relics had undergone restoration without accompanying archival records. UVL revealed the distribution of various conservation materials. Notably, two distinct layers of the conservation material were observed on iron axe 2334. Differences in the fluorescence color and intensity of iron sword 450 provided information regarding the sampling strategy. The samples were collected under ultraviolet light emitting diode illumination to ensure representativeness and minimize damage to the relics. Through Py-GC/MS, the coating materials for iron weight 20791 and iron adze head 2335 were identified as boiled tung oil mixed with rosin resin. Iron axis 2334 had a two-layer coating: a base layer of boiled tung oil and a top layer of shellac. The coating material for iron sword D0008 was determined to be paraffin wax. The protective layer of iron sword 450 included multiple materials, including shellac, polystyrene, and bisphenol-A-type epoxy resin. This study confirms that UVL combined with Py-GC/MS serves as an effective technique for analyzing historical restoration materials. UVL guided the selection of representative samples for Py-GC/MS, reducing the time and amount of sampling required and minimizing further damage to the relics. This research provides valuable data for the restoration archives of five iron artifacts, offering a scientific basis for conservators to evaluate conservation methods, devise future conservation strategies, and exclude ineffective conservation materials.

Molecular-chemical characterization of soil organic matter in wetlands by pyrolysis-gas chromatography/mass spectrometry

The carbon cycle in ecosystems is fundamentally controlled by the composition and transformation of organic molecules. Alpine wetland soils have enormous carbon storage, but they are sensitive to climate change, and can easily shift from carbon sink to carbon source. However, we currently lack understanding in molecular-chemical composition of soil organic matter (SOM) in alpine wetlands. In this study, we tried to decipher molecular-chemical features of SOM in typical alpine wetlands using the pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Results indicated that nitrogen-containing compounds were the most abundant moieties among pyrolytic products of SOM. More than 83 % of pyrolytic moieties had a molecular weight of no more than 200 Daltons and a H/C ratio of no more than 2.0. O/C ratio of most pyrolytic products were less than 0.5. A van Krevelen diagram potentially indicated that SOM in wetlands might consist of massive heterogeneous molecules where aromatic compounds and their derivatives served as the core, with aliphatic hydrocarbon molecules of varying carbon chain lengths attached externally. About 72.25 % of variances in SOM were explained by 50 pyrolytic products, of which toluene was the most important. A significantly negative relation was observed between molecular weight (MW) and abundance of pyrolytic products, while positive relations were found between H/C, O/C, and abundance of pyrolytic products. Our work implied that SOM in wetlands was mainly composed of molecules with low MW and aromatic function groups.

Quantitative analysis of microplastics in Nile tilapia from a recirculating aquaculture system using pyrolysis–gas chromatography–mass spectrometry

AbstractMicroplastic (MP) ingestion through fish consumption is a concern for human exposure. While the presence of plastic particles in fish tissues has been documented worldwide, information on microplastic concentrations in edible tissues, especially those smaller than 10 µm, remains scarce. Spectrometric techniques provide a complementary analytical tool to measure MP mass for human exposure studies without intrinsic size limitations; however, their application to fish analysis is limited. In this study, we utilized pyrolysis gas chromatography–mass spectrometry (Py-GC–MS) for the identification and quantification of MPs in fish muscle tissues. Two sample preparation methods, pressurized liquid extraction, and chemical digestion, were tested for compatibility with Py-GC–MS analysis. An analytical method using chemical digestion was validated for analyzing particles ≥ 0.7 µm for 4 polymer types: polypropylene, polyethylene, polystyrene, and polymethyl methacrylate. The developed method was applied to 24 adult Nile tilapia (Oreochromis niloticus) samples from a recirculating aquaculture system. MPs were detected in 42% of the samples, with an average concentration of 0.14 ± 0.32 µg/g, while high variations within subsamples were observed. Our findings reveal trace amounts of MPs in edible fish tissues from aquaculture, highlighting the potential risk of microplastic ingestion through fish consumption. This underscores the need for further risk assessments to evaluate the impact on human health and to develop appropriate mitigation measures. Graphical Abstract

Identification and analysis of microplastics in para-tumor and tumor of human prostate

While microplastics are widely found in various human organs and tissues, the relationship between microplastics and human health, especially prostate health, remains unclear. This study aims to identify and quantify the properties, types, and abundance of microplastics in paired para-tumor and tumor tissues of human prostate. Additionally, the potential correlation between microplastics abundance and prostate cancer are investigated. Paired para-tumor and tumor samples of the prostate were collected from 22 patients who underwent robot-assisted radical prostatectomy. A combination of laser direct infrared spectroscopy, scanning electron microscopy and pyrolysis-gas chromatography-mass spectrometry was utilized to analyse the properties, type and abundance of microplastics. Correlations between microplastics abundance, demographic characteristics and clinical features of patients were also examined. Laser direct infrared analysis revealed the presence of microplastics, including polyamide, polyethylene terephthalate, and polyvinyl chloride, in both para-tumor and tumor tissues of human prostate. However, polystyrene was exclusively detected in tumor tissues. The particle size distribution in the prostate tissue mainly ranged from 20 to 100μm. Approximately 31.58% of para-tumor samples exhibited sizes between 20 and 30μm, while 35.21% of tumor samples displayed sizes between 50 and 100μm. The shapes of these microplastics varied considerably with irregular forms being predominant. Additionally, microplastics were detected by pyrolysis-gas chromatography-mass spectrometry in 20 paired prostate tissues. The mean abundance of microplastics was found to be 181.0μg/g and 290.3μg/g in para-tumor and tumor of human prostate samples, respectively. Among the 11 target types microplastics polymers, only polystyrene, polypropylene, polyethylene, and polyvinyl chloride were detected. Notably, polystyrene, polyethylene, and polyvinyl chloride, except for polypropylene, demonstrated significantly higher abundance in tumor tissues compared to their respective paired para-tumor. Furthermore, a positive correlation was observed between polystyrene abundance in the tumor samples of human prostate and frequency of take-out food consumption. This research provides both qualitative and quantitative evidence of the microplastics presence as well as their properties, types, and abundance in paired para-tumor and tumor samples of human prostate. Correlations between microplastics abundance, demographics, and clinical characteristics of patients need to be further validated in future studies with a larger sample size. This work was supported by the National Key Research and Development Program of China (2022YFC2702600) and the National Natural Science Foundation of China (Grant No. 82071698, No. 82101676, and No. 82271630).

Analysis of forensic polymer samples using double shot pyrolysis gas chromatography – Mass spectrometry

Polymers are present in many different products, such as paints, plastics, and rubbers, which are routinely encountered in forensic casework. Comparison of such samples involves an initial visual examination followed by comparison of the chemical compositions of the exhibits. Techniques such as Fourier transform infrared spectroscopy (FTIR) and pyrolysis gas chromatography – mass spectrometry (PyGC-MS) have been reported for determining the chemical compositions of polymers in forensic samples. Double-shot pyrolysis gas chromatography – mass spectrometry (DS-PyGC-MS) is an extension of single-shot pyrolysis gas chromatography – mass spectrometry (SS-PyGC-MS) which is the current PyGC-MS method used in most forensic laboratories. DS-PyGC-MS involves a preliminary thermal desorption GC-MS step, followed by the pyrolysis GC-MS step, with this second step being analogous to SS-PyGC-MS. The pyrolyser furnace operates at a lower temperature during the thermal desorption step, allowing low volatility compounds, such as additives, to be thermally desorbed and detected, minimising interference from the polymeric component of the sample. This pilot study analysed four different polymeric substrates, commonly encountered in forensic casework, by DS-PyGC-MS. The substrates chosen were tyre rubber, road cones, cling film, and shotgun wads. The aim was to investigate whether more chemical information was generated by DS-PyGC-MS compared to SS-PyGC-MS, potentially providing increased discrimination of such samples. Qualitative results showed that tyre rubber and road cones were ideal substrates for DS-PyGC-MS. A wide range of additives were detected in these samples in the thermal desorption step, which were not detected using SS-PyGC-MS. All of the rubber tyres (n=5) and road cones (n=6) were able to be uniquely distinguished using DS-PyGC-MS. Some additional compounds were detected in the thermal desorption analysis of shotgun wads (n=4), providing increased discrimination compared to SS-PyGC-MS. For the cling film samples analysed (n=7) the polyethylene-based cling films (n=6) could not be distinguished from each other, with no compounds detected in the thermal desorption step. The other cling film sample contained a mixture of polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT) and could easily be distinguished from the polyethylene-based cling films using either SS- or DS-PyGC-MS, or other common analytical methods such as Fourier transform infrared spectroscopy (FTIR). This pilot study has demonstrated that DS-PyGC-MS has the potential to provide more comprehensive chemical composition information for some polymeric substrates and is a promising method for the forensic comparison of polymer evidence.

Crosslinking Behavior of Ethylene‐Vinyl Acetate Copolymer Encapsulants in Dependence of the Additive Composition

ABSTRACTThe three‐dimensional crosslinking of encapsulants in photovoltaic (PV) modules significantly defines their thermomechanical properties and is usually initiated using peroxides and crosslinking accelerators. However, it has been shown that excess peroxides lead to undesirable side reactions such as browning, which is directly linked to the PV module power losses. Therefore, the encapsulant formulation should be adjusted accordingly, on the one hand, keeping the peroxide concentration possibly low and, on the other hand, enabling a sufficiently high gel content (GC). This work investigates the basic interaction of the crosslinking peroxide Luperox TBEC and the crosslinking accelerator Perkalink 301 (TAIC) with differential scanning calorimetry (DSC), to address this issue. In addition, their reaction potential with the antioxidant butylhydroxytoluene (BHT) is investigated. It is shown that stabilizing additives can have an influence on the peroxide crosslinking process, which can affect the resulting crosslinking state and require optimization of the lamination conditions. The additive content of commercial PV encapsulants is quantified using pyrolysis gas‐chromatography mass spectrometry (PY‐GCMS). Subsequently, a number of films with different TBEC and TAIC contents are produced, and their GC is analyzed as a function of the additive concentrations and lamination conditions. A range of formulations leading to a GC &gt; 75% was identified which can be used as a guidance for encapsulant manufacturers.

Effects of porosity and acidity on deoxygenation and denitrogenation in catalytic pyrolysis of protein-rich microalgae with metal-doped zeolites

The protein-rich defatted microalgae (Nannochloropsis gaditana) after lipid extraction was used as feedstock in catalytic pyrolysis to optimize economic returns of microalgae waste utilization. The effects of Ni- and Co-modified HZSM-5 on the formation of aromatic hydrocarbons (AHs), deoxygenation and denitrogenation in catalytic fast pyrolysis were studied via pyrolysis-gas chromatography and mass spectrometry (Py-GC/MS) at 500°C. Monometallic modified catalysts were synthesized by loading 0.5 wt%, 1 wt%, and 2 wt% of metal species onto HZSM-5 using ion exchange methods. The composition and pyrolysis pathways of primary volatiles detectable by gas chromatography (GC) were investigated, which included phenols, aliphatic hydrocarbons, AHs, acids, furans, N-heterocyclic compounds (N-HCs), amides and nitriles. The relative yields in AHs increased about 10.9 (0.5 wt% Ni/HZSM-5 or Ni0.5), 10.2 (Ni1), 6.8 (Ni2), 7.3 (Co0.5), 9.7 (Co1) and 7.8 (Co2) times compared to the relative yield from defatted microalgae pyrolysis. The doping of metals onto the HZSM-5 altered its porosity and acidity, leading to an impaired diffusion of reactants but also the creation of new acidic sites, which enhanced the selectivity towards monoaromatic hydrocarbons (MAHs) by aromatization and cleavage of N-containing heterocycles via the H radicals formation. Ni-loaded HZSM-5 outperformed Co-modified zeolite with respect to AHs production, deoxygenation and denitrogenation. The specific surface area (SBET) and pore volume were positively correlated with the formation of AHs, while strong acidity showed a strong positive correlation with the generation of nitriles and N-HCs. Relatively low loadings of Ni and Co (0.5–1 wt%) on HZSM-5 (Si/Al = 23) were recommended to decrease the N-containing compounds in pyrolysis vapors from defatted microalgae. The findings may shed light on the development of a high-performance HZSM-5 catalyst for the production of AHs and denitrogenation from protein-rich defatted microalgae.

ACFs-NH2 developed for dispersive solid phase extraction combined with Py-GC/MS for nanoplastic analysis in ambient water samples

Accurate determination of nanoplastics (NPs) in aquatic ecosystems constitutes a challenge for which highly sensitive analytical methods are necessitated. Herein, a sample pretreatment based on self-made amino-functionalized activated carbon fibers (ACFs-NH2) dispersive solid-phase extraction (DSPE) allows for high-recovery, followed by high-sensitivity detection of NPs by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The developed methodology allowed low detection limits (20–100 μg/L) to be achieved quickly in a few steps. Under optimal conditions, ACFs-NH2 (12.5 mg) was able to recover ≥98.45 % of polystyrene (PS) nanoplastics at high concentration (100 mg/L) in 10 mL seawater. Based on the high adsorption performance of materials, the adsorption dynamics and isotherms were determined to infer the interaction mechanism of PSNPs on ACFs-NH2. After adsorption, the target on the surface of the adsorbent can be directly pyrolyzed, which can simplify the operation steps and avoid the elution of organic solvents, making the process more environmentally friendly. This strategy is feasible for the analysis of trace NPs in water systems.

Deconstructing contemporary disposable vapes: A material and elemental analysis

Disposable e-cigarettes (vapes) are becoming increasingly popular but there are concerns about their impacts on human health, the environment and resource sustainability. A better understanding of these impacts and potential solutions requires characterisation and quantification of the materials and chemicals used in their construction. In the present study we dismantle nine types of popular, single-use vapes and analyse the components by X-ray fluorescence spectrometry and pyrolysis-gas chromatography mass spectrometry. The median dry mass of vapes was about 50 g, and the main material contribution was either plastic (up to about 80 %) or metal (up to about 85 %, and including the battery). Polycarbonate was the principal plastic used in the casing and nylon was always employed in the wick, but a range of other polymers were identified in other components used in wire insulation, sleeving, packaging, bundling and sealing. Various elements, as additives, residues or contaminants, were encountered in these parts that included As, Ba, Bi, Cr, Hg, Pb and Sb. Metal components were constructed of Al (often with Ti), stainless steel or Ni-based alloys (mainly in the coils), but other metals were often incorporated in alloys (e.g., Bi, Pb, W) or were present in trace quantities (including Co and Nb). Common metals in the Al-plastic-laminated Li-ion batteries were Cu, Co, Fe and Ni, but Au, Ba, Hg and Pb were also detected, while additional metals in the Cu-based printed circuit boards included Ag, Al, Ni, Sn, Ti and V, with traces of Ag, Bi, Mn, Nb and Pb present. The presence of toxic or potentially toxic metals in the vapes poses an environmental hazard through leaching after littering or landfilling, while metals within or in contact with the wick raise concerns about transfer to the e-liquid and exposure to the user. The overall material and chemical complexity of vapes presents challenges for safe disposal and component recycling, but the presence of critical elements, like Bi, Co, Nb, Sb, Sn, V and W, has additional implications for resource management.

Preparation of metal-modified carbon-based catalyst and experimental study on catalytic pyrolysis of distillers dried grains with solubles

Distillers dried grains with solubles (DDGS) offer high calorific value, suited for catalytic rapid pyrolysis for energy and chemical applications, yet tar and coke formation during bio-oil upgrading necessitates exploration of cost-effective, durable biocarbon-based catalysts for tar removal. In this study, a carbon-based catalyst was prepared by metal modification of alkaline biochar for catalytic pyrolysis with Distillers dried grains with solubles (DDGS) biomass. Brunauer–Emmet–Teller (BET), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) were used to characterized the morphology and microstructure of the metal-modified carbon-based catalysts. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) was used to analysis the pyrolysis-gas of catalytic pyrolysis. Furthermore, the effects of the loading and metal mass ratio of carbon-based monometallic catalysts (Fe and Co) and carbon-based bimetallic catalysts (Fe-Co) on the distribution of the DDGS pyrolysis products were further investigated. The results showed that the 8 wt% of loading rate of bimetallic catalyst significantly reduced the oxygenated compounds but increased the aromatic hydrocarbons. Compared with pyrolysis without catalyst, when the catalyst was 2Fe6Co (mass ratio of Fe/Co 1:3), the hydrocarbons increased from 36.42 % to 44.53 %, the oxygen-containing compounds decreased from 60.36 % to 52.35 %, and the aromatics increased significantly from 0.73 % to 25.37 %. This study provides a new route of increasing the aromatic hydrocarbon content of catalytic pyrolysis to offer theoretical basis for carbon-based catalysts of biomass conversion.