Pyrolysis Coupled With Gas Chromatography/mass Spectrometry Research Articles

Synergistic effects and products distribution during Co-pyrolysis of biomass and plastics

Co-pyrolysis of agricultural biomass and plastic wastes is examined here from the perspective of enhanced value products, energy production, and pollution reduction. The effect of different species of plastic on the products distribution during co-pyrolysis with biomass, or rapeseed stalk (RS) with polyethylene terephthalate (PET), polypropylene (PP) and polyvinyl chloride (PVC) was performed using a pyrolyzer coupled with gas chromatography/mass spectrometry (Py-GC/MS). The results showed co-pyrolysis of rapeseed stalk with different plastics had little effect on the evolved product species. However, significant differences were observed on the content and yield of products. The co-pyrolysis of rapeseed stalk and polyethylene terephthalate provided primarily the monocyclic aromatic hydrocarbon (MAH). The co-pyrolysis of rapeseed stalk and polypropylene provided aliphatic hydrocarbons (mainly olefins) and promoted the generation of aliphatic hydrocarbons and alcohols due to the synergistic effect. The co-pyrolysis of rapeseed stalk and polyvinyl chloride could promote the production of phenols but inhibited the production of liquid products. The results also showed relatively high product quality from the co-pyrolysis of rapeseed stalk and polypropylene. The results provided plausible pathways for effective utilization of residual agricultural wastes and selected waste plastics for enhanced product quality and content.

Archaeometric Study of the Mural Paintings by Saturnino Gatti and Workshop in the Church of San Panfilo, Tornimparte (AQ): The Study of Organic Materials in Original and Restored Areas

In the context of the archaeometrical study of Saturnino Gatti’s wall paintings, a significant aspect concerned the study of the organic component to understand both the original binders used in the original areas and the products used for pictorial reintegration and restoration of the painted surfaces. Thanks to the results obtained from various non-invasive and multi-band imaging techniques, it was possible to define Gatti’s original painting technique and identify the materials subsequently applied in significant samples. To this end, molecular analyses based on mass spectrometry were carried out. Different procedures in gas chromatography–mass spectrometry (GC-MS) and in pyrolysis coupled with gas chromatography–mass spectrometry (Py-GC-MS) were adopted. The analyses revealed a variety of organic materials on the mural paintings, most of which are from past restoration interventions and have synthetic origin. The overspread presence of paraffin is likely due to the application of a mineral wax-based coating/consolidant. In particular, the execution technique encompassed the use of tempera-based paints, while retouched areas were characterised by the presence of oil-based resins.

Variations in the composition and structure of the lignins of oat (Avena sativa L.) straws according to variety and planting season

The differences in the composition and structure of the lignins from straws of different oat (Avena sativa L.) varieties, planted in two seasons (winter and spring), were studied in detail by different analytical techniques such as pyrolysis coupled to gas chromatography–mass spectrometry (Py-GC/MS), two-dimensional nuclear magnetic resonance (2D-NMR), derivatization followed by reductive cleavage (DFRC), and gel permeation chromatography (GPC). Overall, the analyses revealed that oat straw lignins were enriched in guaiacyl (G; 50–56 %) and syringyl (S; 39–44 %) units, with relatively lower amounts of p-hydroxyphenyl (H; 4–6 %) units. The lignins also incorporated significant quantities of p-coumarates (8–14 % of total lignin units), which are acylating the γ-OH of the lignin side chains, and predominantly over the S units. Furthermore, oat straw lignins also incorporated considerable amounts of the flavone tricin (5–12 % of total lignin units). Interestingly, this study revealed that the lignin content and composition of the oat straws vary with genotype and planting season. Since p-coumarates and tricin are high-value aromatic compounds especially attractive from a biorefinery point of view, the information disclosed here is highly relevant to plant breeding programs aimed at developing functional foods and lignin modifications for improved biorefinery applications.

Diversified crop rotations and organic amendments as strategies for increasing soil carbon storage and stabilisation in UK arable systems

Adaptations in crop rotation with the inclusion of temporary grass-clover leys and organic amendments, have been promoted as effective ways to improve soil carbon (C) sequestration and mitigate climate change in agricultural systems. However, there are still a lot of uncertainties related to i) the combined effects of different crop rotations and different fertilisation sources, e.g., organic amendments, on soil C stocks; and ii) their potential effect on C stabilisation. The objective of this study was to evaluate the effect of different arable crop rotations with varying degrees of diversity in crop type and lengths of grass-clover ley periods and fertilisation sources on soil C stocks and C stabilisation down to 0.60 m soil depth. This was investigated in a long-term factorial field experiment-combining different crop rotation (cereal-intensive conventional vs. diversified legume-intensive organic) with different lengths of grass-clover ley periods (2 vs. 3 years), fertilisation sources (mineral vs. compost), and years (samples taken at the beginning and at the last year of one complete cycle of rotation; 8 years apart)-to explore their individual and interactive effect on soil C stock and C stabilisation at two soil depths (0–0.30 and 0.30–0.60 m). Soil C stabilisation was assessed using a unique combination of three different techniques: physical fractionation for separation of C associated to organic and mineral fractions, thermal analysis combined with differential scanning calorimetry and a quadrupole mass spectrometry (TG-DSC-QMS) for physical-chemical aspects, and pyrolysis coupled with gas chromatography-mass spectrometry (Py-GC/MS) for molecular structural information. The findings showed higher soil C stocks under the diversified organic rotation with 3 years of grass-clover ley period at both soil depths, regardless of the fertilisation source or sampling year. However, the organic rotation seemed to deliver stable soil C stocks only in the subsoil layer. Compost fertilisation, in turn, increased topsoil C stocks between the two sample dates under both rotations, and it appears to be stable. These results suggested that combining a diversified organic rotation with 3 years grass-clover ley with compost fertilisation could be one way for agricultural systems to deliver stable soil C sequestration.

Analysis of microplastics in the environment: Identification and quantification of trace levels of common types of plastic polymers using pyrolysis-GC/MS

This work describes the development of analytical workflows based on pyrolysis coupled with gas chromatography-mass spectrometry (Pyr-GC/MS) for the qualitative and quantitative analysis of 12 of the most common plastic polymers in environmental samples. The most suitable characteristic pyrolyzate compounds and respective indicator ions were selected for each polymer in order to obtain the most appropriate response for analytical purposes. Additionally, commercial pyrolyzates and polymers libraries were used to confirm the identity of the detected microplastics. The method was validated, showing a good linearity for all the plastic polymers (R2 > 0.97) and limits of detection between 0.1 (polyurethane) to 9.1 µg (polyethylene). The developed methodology was successfully applied for the analysis of plastic polymers in environmental microplastic samples collected in three Mediterranean beaches (NE Spain).•Fast and reproducible Pyr-GC/MS method for the analysis of the 12 most common plastic polymers in a single GC/MS run•Straightforward analytical workflows using pyrolyzates and polymers libraries enable a fast identification and quantification of microplastics in environmental samples

Pyrolysis gas chromatography mass spectrometry: A promising tool for disclosing metal-free tanning agents used in leather industry

Leather represents the principal industrial product derived from the skin of animals. Leather manufacturing has evolved from artisanal practice, making use of vegetable tannins, to industrial production, today mostly based on chromium salts. Chromium tanning accounts for the most efficient and affordable process available on the market, but the environmental pressure caused by heavy metal pollution has pushed towards the development of Metal-Free leather tanning agents. This paper aims at highlighting the potentialities and limits of analytical pyrolysis to characterise metal-free leather samples and to identify the tanning agents. To this aim, thirty-three bovine split leather samples tanned with various metal-free tanning agents (constituted by single or combined formulations of GRANOFIN® F90, glutaraldehyde, tetrakis(hydroxymethyl)phosphonium sulphate, oxazolidine and three different synthetic tannins), provided by bovine split suppliers (Tuscany, Italy) were analysed by flash Pyrolysis coupled with Gas Chromatography - Mass Spectrometry (Py-GC-MS). For most of the tanning formulations, Py-GC-MS was able to determine pyrolytic markers in reference materials, intermediates (wet-white metal-free and metal-free crust) and end-products (metal-free final products). Evolved Gas Analysis coupled with Mass Spectrometry (EGA-MS) was used to evaluate, from the molecular point of view, the thermodegradative profiles of metal-free leathers and compare them with that of chromium tanned leather.

Pyrolytic Depolymerization Mechanisms for Post-Consumer Plastic Wastes

Fast pyrolysis of five post-consumer plastic waste materials was studied using pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS) technique. Prescription medicine bottles, landfill liners, and one type of industrial plastic waste represented polyolefin-based polymers, whereas packaging material represented polystyrene, and other industrial plastic waste represented polyurethane. The noncatalytic and catalytic degradation mechanisms of all five post-consumer plastic wastes were elucidated. The noncatalytic pyrolysis experiments were conducted at a temperature of 600 °C for a residence time of 5 min. For catalytic pyrolysis, a spent FCC catalyst was utilized for polystyrene, a sulfated zirconia-based catalyst was utilized for polyurethane, and a Y-zeolite catalyst was used for polyolefinic plastic waste. The results suggested that the thermal reaction has higher monomeric and oligomeric selectivity than the catalytic reaction. Results from the catalytic runs showed that the addition of catalysts greatly influences product compositions and has a significant effect on the selectivity of a specific compound. One of the plastic wastes, landfill liner, was selected for a batch scale pyrolysis at 420–440 °C using Y-zeolite as a catalyst to demonstrate the product properties and potential use of the liquid product formed. The complete product distribution of plastic crude oil was performed followed by distillation to produce aviation range fuel. The fuel properties of aviation range fuel were examined, and results suggested that the fuel fraction can be easily blended with commercially available fuels for direct applications.

Strategic hazard mitigation of waste furniture boards via pyrolysis: Pyrolysis behavior, mechanisms, and value-added products

Waste furniture boards (WFBs) contain hazardous formaldehyde and volatile organic compounds when left unmanaged or improperly disposed through landfilling and open burning. In this study, pyrolysis was examined as a disposal and recovery approach to convert three types of WFBs (i.e., particleboard, plywood, and fiberboard) into value-added chemicals using thermogravimetric analysis coupled with Fourier-transform infrared spectrometry (TG-FTIR) and pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS). TG-FTIR analysis shows that pyrolysis performed at an optimum temperature of 250–550 °C produced volatile products mainly consisting of carbon dioxide, carbon monoxide, and light hydrocarbons, such as methane. Py-GC/MS shows that pyrolysis at different final temperatures and heating rates recovered mainly phenols (25.9–54.7%) for potential use as additives in gasoline, colorants, and food. The calorific value of WFBs ranged from 16 to 18 MJ/kg but the WFBs showed high H/C (1.7–1.8) and O/C (0.8–1.0) ratios that provide low chemical energy during combustion. This result indicates that WFBs are not recommended to be burned directly as fuel, however, they can be pyrolyzed and converted into solid pyrolytic products such as biochar with improved properties for fuel application. Hazardous components, such as cyclopropylmethanol, were removed and converted into value-added compounds, such as 1,4:3,6-dianhydro-d-glucopyranose, for use in pharmaceuticals. These results show that the pyrolysis of WFBs at high temperature and low heating rate is a promising feature to produce value-added chemicals and reduce the formation of harmful chemical species. Thus, the release of hazardous formaldehyde and greenhouse gases into the environment is redirected.

Evolution of Composting Process in Maize Biomass Revealed by Analytical Pyrolysis (Py-GC/MS) and Pyrolysis Compound Specific Isotope Analysis (Py-CSIA)

An innovative approach based on the combination of analytical pyrolysis coupled with gas chromatography-mass spectrometry (Py-GC/MS) with compound-specific isotope analysis (Py-CSIA) is used to study the composting process of maize biomass. This multidisciplinary approach aims to elucidate the decomposition rate of the main biogenic materials (lignin, cellulose, proteins, lipids, and waxes) responses to the composting process. According to Py-GC/MS data/structural composition, a noticeable and significant decrease during the first stage of the composting process of carbohydrates and aromatic compounds is found, followed by a gradual increase of all compounds till the end of the experiment. This trend, along with an increase of fatty acids methyl-ester at the first composting stage, sustains the microbial activity and its stabilization over time. Py-CSIA data showed a significant enrichment in 13C in all identified compounds over time, supporting the semi-quantitative results and the decomposition of initial biomass throughout the composting process. This trend is also perceptible in lignin moieties, long-chain aliphatic structures, and isoprenoids, as highly recalcitrant compounds, presumably due to depolymerization and carbon translocation of side-chain molecules during the composting process. Compound-specific isotope values showed a good correlation with the bulk isotope data, and this served as validation of the technique. However, bulk values showed higher heterogeneity because those represent an average of all organic compounds in the sample. By combining isotopic and structural information using Py-GC/MS and Py-CSIA, we are able to provide further information and a more detailed approach to the study of the decomposition process of biomass by considering the diverse dynamics of the main biogenic compounds.

Structural Characteristics of the Guaiacyl-Rich Lignins From Rice (Oryza sativa L.) Husks and Straw.

Rice (Oryza sativa L.) is a major cereal crop used for human nutrition worldwide. Harvesting and processing of rice generates huge amounts of lignocellulosic by-products such as rice husks and straw, which present important lignin contents that can be used to produce chemicals and materials. In this work, the structural characteristics of the lignins from rice husks and straw have been studied in detail. For this, whole cell walls of rice husks and straw and their isolated lignin preparations were thoroughly analyzed by an array of analytical techniques, including pyrolysis coupled to gas chromatography-mass spectrometry (Py-GC/MS), nuclear magnetic resonance (NMR), and derivatization followed by reductive cleavage (DFRC). The analyses revealed that both lignins, particularly the lignin from rice husks, were highly enriched in guaiacyl (G) units, and depleted in p-hydroxyphenyl (H) and syringyl (S) units, with H:G:S compositions of 7:81:12 (for rice husks) and 5:71:24 (for rice straw). These compositions were reflected in the relative abundances of the different interunit linkages. Hence, the lignin from rice husks were depleted in β–O–4′ alkyl-aryl ether units (representing 65% of all inter-unit linkages), but presented important amounts of β–5′ (phenylcoumarans, 23%) and other condensed units. On the other hand, the lignin from rice straw presented higher levels of β–O–4′ alkyl-aryl ethers (78%) but lower levels of phenylcoumarans (β–5′, 12%) and other condensed linkages, consistent with a lignin with a slightly higher S/G ratio. In addition, both lignins were partially acylated at the γ-OH of the side-chain (ca. 10–12% acylation degree) with p-coumarates, which overwhelmingly occurred over S-units. Finally, important amounts of the flavone tricin were also found incorporated into these lignins, being particularly abundant in the lignin of rice straw.

Effects of Cd and Sn modified MCM-41 on pyrolysis of cellulose

Biomass pyrolysis has become one of the promising technologies for fuel and fine chemical production. Cellulose constitutes the main body of plant biomass and may serve as a stereochemically pure reservoir to obtain active reagents for the synthesis of biologically active substances and structural units of valuable chemical substances. This study investigated the effect of cadmium (Cd) and tin (Sn) modified mesoporous sieve R-MCM-41 (R: Cd or Sn) on the pyrolysis of cellulose via thermogravimetric analysis (TGA) and pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS). The Si/R molar ratio of metal modified catalysts was between 100:1 and 10:1. TGA showed that Cd- and Sn-modified MCM-41 can effectively promote the degradation of cellulose, which was almost completely volatilized at 650 °C under the catalysis of Cd-MCM-41(50) and Sn-MCM-41(50). Py-GC/MS tests were carried out with different R-MCM-41s, reaction temperatures of 450 °C, 550 °C, and 650 °C, and the cellulose-to-catalyst ratios of 5:1, 1:1, and 1:5. The use of Sn-MCM-41 promoted the formation of glycolaldehyde and a limited amount of 1,2-cyclopentanedione and 5-methylfurfural. Cd-MCM-41 catalyzed pyrolysis produced higher levels of 5-hydroxymethylfurfural, 1-hydroxy-3,6-dioxabicyclo[3.2.1]octan-2-one (LAC), 2,5-dimethyl-4-hydroxy-3(2H)-furanone, 2-hydroxy-3-methyl-2-cyclopenten-1-one, 1,2-cyclopentanedione, 3-methyl-2,4(3H,5H)-furandione, furfural, hydroxyacetone, glycolaldehyde, and butanone. When the pyrolysis temperature increased from 450 °C to 650 °C, the content of most small-molecule chemicals in the products increased by 1.8–4.1 times. When applying over-dosage of Cd-MCM-41(50) in the pyrolysis, anhydrosugars were completely degraded and dehydration/decarbonylation reactions were extensively enhanced, resulting in major products of butanone, furfural, and 5-methylfurfural. The possible reaction mechanism was proposed.

Correlation between bacterial decay and chemical changes in waterlogged archaeological wood analysed by light microscopy and Py-GC/MS

AbstractErosion bacteria are the main degraders of archaeological wood excavated from waterlogged environments. Light microscopy and analytical pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS) were exploited to study waterlogged archaeological wood (Pinus sylvestrisL.) at different stages of bacterial decay. The research explored the biochemical changes related to erosion bacteria degradation of the secondary cell wall in the wood cells and the chemical changes related to abiotic processes induced by the long-term waterlogged burial environment. Erosion bacteria were demonstrated by chemical analysis to cause significant holocellulose depletion. Detailed analysis of the holocellulose and lignin pyrolysis products revealed only minor chemical changes in the residual structure even after heavy erosion bacteria decay. Chemical changes in the lignin polymer is associated to enzymatic unlocking of the lignocellulose to gain access to the holocellulose fraction of the cell wall. Chemical changes in the holocellulose fraction are suggested to stem from depolymerisation and from alterations in the polymer matrix of the residual wood cell wall structure. Interestingly, a difference was observed between the sound reference wood and the waterlogged archaeological wood without erosion bacteria decay, indicating that long-term exposure in waterlogged environments results in partial decay of the holocellulose even in absence of bacterial activity.

Organosulphur-modified biochar: An effective green adsorbent for removing metal species in aquatic systems

Organosulphur-modified biochar (BC) can be used as a green adsorbent for removing potentially toxic metal ions from aqueous solutions. In this study, sugarcane bagasse BCs (produced at pyrolysis temperatures from 300 to 700°C) were modified in a single-step reaction with isothiocyanate. The performance and selectivity of raw and modified BCs for removing Cd2+, Ni2+, Pb2+ and Cr3+ from mono- and multi-element aqueous solutions were investigated. The characterisation of the BCs was performed by proximate analysis, Fourier transformed infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS) and pyrolysis coupled to gas chromatography-mass spectrometry (Py-GC-MS). The results showed that the organosulphur modification increased S and N contents on the surface of the BCs, particularly isothiocyanate groups. The maximal adsorptions were observed for raw and modified BCs produced at 700°C and pH 6. The adsorption kinetics of Cd2+, Ni2+, Pb2+ and Cr3+ before and after BC modification was best described by the pseudo-second order kinetic model. The results indicated that the removal of metal ions by modified-biochars follows the order Pb2+> Cr3+> Cd2+ ≅ Ni2+ and Cd2+> Pb2+> Ni2+≅Cr3+ for mono-element and multi-element systems, respectively. The mechanisms involved in the adsorption were physisorption, chemisorption, complexation, precipitation, and ion exchange. The presence of other metal ions in the multi-element system caused a synergistic effect on adsorption of Cr3+, Cd2+ and Ni2+ and an antagonistic effect on adsorption of Pb2+. Organosulphur-modified BC can be an effective andselective adsorbent for removing Cd2+, Ni2+, Pb2+ and Cr3+ from aqueous solutions.

Unexpected behavior of commercial artists’ acrylic paints under UVA artificial aging

The study of the behavior of acrylic paints after UV-A (400–300 nm, near UV) artificial exposure was further investigated by extending it to more commercially available artists’ acrylic paints. The accelerated aging of eight acrylic-based commercial paints was studied using a combination of analytical techniques including Nuclear Magnetic Resonance (NMR) spectroscopies, Pyrolysis coupled with Gas Chromatography/Mass Spectrometry (Py-GC/MS), Fourier Transform Infrared in ATR mode (FTIR-ATR), Direct Analysis in Real Time coupled to Mass Spectrometry (DART-MS) and microscopic techniques, such as Stereoscopic Microscopy (SM) and Scanning Electron Microscopy coupled with Energy Dispersive X-ray Spectroscopy (SEM-EDS). All the aging process was characterized and monitored to study the signs of decay. During the aging process a gradual loss of the organic surfactant occurred in all the paints, similar to the results contained in a previous study. Interestingly, two of the studied paints presented an unexpected behavior related to the properties of the acrylic binder. In one of such paints solid-state 13C Cross Polarization Magic Angle Spinning (13C CPMAS) NMR spectroscopy was performed. The results obtained by changing the recycled delay and carrying out variable temperature experiments, suggested a change in the internal mobility of the aged sample that could be attributed to the presence of ionomers.According to this study, the aging of acrylic binders may not be the same in all paints and may be affected by the interaction of different components of the formulation. Understanding these processes will give more tools for the preservation of modern art paintings and cultural heritage since this type of commercial paints and other conservation materials of the same composition were extensively used during the 20th century.

Pyrolysis behavior and product distribution of exinite submacerals

This paper systematically investigated the pyrolysis behavior and product distributions of exinite submacerals isolated from different low-rank coal using thermogravimetric analyzer coupled with Fourier Transform infrared spectroscopy (TG-FTIR) and Pyrolyzer coupled with gas chromatography/mass spectrometry (Py-GC/MS). The functional groups in exinite submacerals were studied by FTIR simultaneously. Results suggested that all submacerals were less aromatic with abundant aliphatic chains and more oxygen-containing functional groups. Besides, the TG profiles lateral shifted towards higher temperatures with the heating rates. The kinetic parameters (E and A) indicated that the calculated activation energy and frequency factor of the resinite were the largest, and the barkinite was close to cutinite, while the sporinite was the smallest. The release of CO2, CH4, H2O and CO were measured during pyrolysis process. The temperature intervals and contents for these volatile species reflected the difference in pyrolysis mechanism and the contents of functional groups for different submaceral. According to the fast pyrolysis (650 ℃) by Py-GC/MS, the volatile species could be classified into eight categories including alkanes, alkenes, cycloalkanes, arenes, alcohols, phenols, heteroatomic compounds and ketones. The pyrolysis behavior and product distributions of submacerals were closely related to the chemical structure of its special parent material. The sensitivity of different chemical structures in exinite submacerals to temperature achieved different trends of pyrolysis behavior and product distribution.

Characterization of volatile and non-volatile fractions of spices using evolved gas analysis and multi-shot analytical pyrolysis

In the present work, evolved gas analysis-mass spectrometry (EGA-MS) and analytical pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS) were used to characterize both the volatile and non-volatile fractions of six commercially available spices. Analysis of spices is usually performed through the study of their headspace composition by solid phase microextraction (SPME). In this new approach, EGA-MS was used to establish thermal degradation regions, and Py-GC/MS was used to obtain compositional information on each region separately using double-shot pyrolysis. This study demonstrates that EGA-MS and Py-GC/MS provide the same advantages of solid-phase micro extraction and increase the range of detectable products by performing high-temperature desorption and degradation of the non-volatile fraction of spices. Our approach provided both qualitative and semi-quantitative data that could be used in the future to improve authentication studies by considering the results not only of headspace composition, but also on the pyrolytic behavior of the lignocellulosic matrix.

Formaldehyde-Free Polybenzoxazines for High Performance Thermosets

We report the synthesis and ring-opening polymerization of new formaldehyde-free benzoxazines. The polybenzoxazines obtained displayed high thermal stability and high char yields. Data from the literature combined with our analyses by differential scanning calorimetry and thermogravimetric analyses gave deeper understanding about the use of aromatic aldehydes instead of formaldehyde for the generation of polybenzoxazines. Using pyrolysis coupled with gas chromatography/mass spectrometry (Py-GC/MS) at different temperatures, we provided qualitative data to propose some polymerization and degradation mechanisms associated with these new structures. A dialdehyde was also used for the first time in order to obtain difunctional monomers, instead of using diamines or bisphenols. Interestingly, we demonstrated that formaldehyde, which is a CMR (carcinogenic, mutagenic, and/or reprotoxic) substance, could be avoided for the synthesis of polybenzoxazines without any loss of thermal performance. Finally, some interesting structure–properties relationships are herein discussed. In particular, the use of benzyl amines, rather than aromatic amines, was found to significantly increase the char yields.

Waste tires pyrolysis kinetics and reaction mechanisms explained by TGA and Py-GC/MS under kinetically-controlled regime

The fast pyrolysis of waste tires (WTs) is studied by quasi-isothermal thermogravimetric (TGA) analysis, kinetic modelling and an analytical pyrolyzer coupled with gas chromatography/mass spectrometry (Py-GC/MS). The TGA demonstrated that the WTs pyrolysis is ruled by devolatilization/condensation and depropagation reactions, up to 482 °C. At higher temperatures, the cyclization and aromatization of primary products take place to form mostly monoaromatics. Py-GC/MS experiments were performed under kinetic regime according to the thermal map established by the ratio between Biot́s (31.25) and Py-numbers (7.7⋅106). Limonene (51%) and isoprene (20.5%) were the major compounds detected at temperatures below 435 °C, while above 600 °C limonene was converted to mono-aromatics (SBTX = 28.7%). The approach to equilibrium of Diels-Alder reaction demonstrated that there is an equilibrium-ruled behavior between isoprene and limonene, particularly at T > 600 °C. The Ea values calculated by the Starinḱs model ranged from 101.5 to 176.7 kJ/mol, while for model-based kinetics it was 152.7 kJ/kmol. The integration of TGA, kinetic modelling and Py-GC/MS provided insights into pyrolysis reaction mechanism.

Pyrolysis behaviors and product distribution of Shengli Lignite at different heating rate and final temperature by TG-FTIR and Py-GC-MS

ABSTRACT The slow pyrolysis characteristics of Shengli lignite (SL) from ambient temperature to 800°C at heating rates of 20°C/min and 100°C/min were investigated by thermogravimetric analysis coupled with Fourier transform infrared spectrometry (TG-FTIR) and by pyrolysis coupled with gas chromatography-mass spectrometry (Py-GC-MS). The final temperatures had larger effect on the pyrolysis products. The pyrolysis at 800°C of 20°C/min and 100°C/min (from the Py-GC-MS) obtained a variety of aliphatic compounds and monocyclic aromatic compounds, including short-chain olefins, alcohols, and ketones. But at 400°C, almost no short-chain aliphatic compounds were obtained, and a faster heating rate (100°C/min) was beneficial for obtaining long-chain aliphatic alkanes, alcohols, and acids (n-Hexadecanoic acid and Octadecanoic acid). It provides evidence that the aliphatic chains in lignite structure were long-chain, and the short-chain aliphatic compounds were from the secondary decomposition. The bicyclic compounds, monocyclic aromatic compounds were always important products. The real-time FTIR showed obvious differences in the pyrolysis at different heating rates. In the slower pyrolysis process (20°C/min), the absorbance of CO2 was much higher than that in the other processes, but in the faster pyrolysis process (100°C/min), the diversity of the pyrolysis products was substantially improved by the -OH, C = O, -COOH, C-CH3 and aromatic C-H functional groups, so maybe more valuable gas/liquid products could be produced at larger heating rate. The products at some specific temperatures (from the DTG peaks) were also provided for the reaction analysis.

The role of the polymeric network in the water sensitivity of modern oil paints

Spectroscopic and mass spectrometric analytical techniques were used to characterise two naturally aged Winsor & Newton (W&N) Winsor Green (phthalocyanine green, PG7) artists’ oil colour paint swatches dating to 1993 and 2003. Infrared and Energy Dispersive X-ray (EDX) analysis indicated that the swatches were of closely similar composition, yet the swatch from 2003 was water-sensitive whilst the swatch from 1993 was not. Water-sensitivity is a conservation challenge associated with significant numbers of modern oil paintings and this study aimed to further develop our understanding of the molecular causes of water sensitivity. SEM elemental mapping of samples taken from both swatches provided no indication for the formation of epsomite – a known cause of water sensitivity in some modern oil paintings. Liquid chromatography coupled with mass spectrometry (HPLC-MS) and gas chromatography coupled with mass spectrometry (GC-MS) also revealed very similar qualitative-quantitative composition in terms of unbound and esterified medium fractions. The polymeric network was investigated using analytical pyrolysis. A combination of flash pyrolysis coupled with gas chromatography mass spectrometry (Py-GC-MS) together with evolved gas analysis mass spectrometry (EGA-MS) revealed that the polymeric material was relatively more abundant in the non-water-sensitive paint. This is the first multi-analytical study that has demonstrated a correlation between water-sensitivity and the degree of polymerisation of the oil medium; independent of other known causes of water-sensitivity.