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Pyrolytic synergistic interactions, in which the production of pyrolyzates is enhanced or inhibited, commonly occur during the co-pyrolysis of different polymeric materials, such as plastics and biomass. Although these interactions can increase the yield of desired pyrolysis products under controlled degradation conditions, the desired compounds must be separated from complex pyrolyzates and further purified. To balance these dual effects, this study was aimed at examining pyrolytic synergistic interactions during slow heating co-pyrolysis of biodegradable plastics including polylactic acid (PLA) and poly(3-hydroxybutyrate-co-3-hydroxyhexaoate) (PHBH) and petroleum-based plastics including high-density polyethylene (HDPE), polypropylene (PP), and polystyrene (PS). Comprehensive investigations based on thermogravimetric analysis, pyrolysis-gas chromatography/mass spectrometry, and evolved gas analysis-mass spectrometry revealed that PLA and PHBH decompose at lower temperatures (273-378 °C) than HDPE, PP, and PS (386-499 °C), with each polymer undergoing independent decomposition without any pyrolytic interactions. Thus, the independent pyrolysis of biodegradable plastics, such as PLA and PHBH, with common plastics, such as HDPE, PP, and PS, can theoretically be realized through temperature control, enabling the selective recovery of their pyrolyzates in different temperature ranges. Thus, pyrolytic approaches can facilitate the treatment of mixed biodegradable and common plastics., (© 2024. The Author(s).)

Fast co-pyrolysis has been suggested as a promising technique to solve the environmental issues and simultaneously recover value-added products from polymer wastes. However, to date, no studies have focused on fast co-pyrolysis of printed circuit boards (PCB) and waste tire (WT). Therefore, we comprehensively investigated the fast co-pyrolysis of PCB and WT using pyrolysis-gas chromatography/mass spectrometry. The results show that an increase in temperature during fast pyrolysis improved the interactions between the PCB and WT pyrolyzates, increasing the formation of aliphatic and aromatic compounds. The formation of p-cymene was greatly induced by the isomerization and dehydrogenation reactions of D-limonene. Co-pyrolysis reduced the formation of brominated phenols and benzothiazole from PCB and WT pyrolysis, respectively, whereas promoted the interactions between Br- and S/N-containing radicals, concentrating them into heavy compounds. Increasing the temperature enhanced the release of heteroatom compounds. The findings suggest that debromination of PCB achieved via dehydrogenation of WT pyrolysis provoked secondary reactions of olefins and interactions of heteroatom radicals. The major products were accurately predicted by different fitting models using response surface methodology, indicating the synergistic interactions during co-pyrolysis. The results were beneficial for optimizing the experimental parameters to obtain the maximum yield of desired products., (Copyright © 2022 Elsevier B.V. All rights reserved.)

There are numerous combinations of biomass, plastic, and co-pyrolysis conditions. The presence of synergies, which make pyrolyzate distribution more complex, has been supported by research. In this study, the potential of response surface methodology (RSM) to predict the pyrolyzate yields affected by synergies during co-pyrolysis (500-700 °C) of cellulose and polyethylene was investigated, beyond gas, oil, and char yields. The results indicated that co-pyrolysis promoted liquid and C 5-28 hydrocarbon production with increasing temperature. The quadratic model could predict the total gas, CO, CO 2 , and liquid yields, including the synergy. The cubic model could predict the levoglucosan and C 5-28 hydrocarbon yields due to various synergies under different conditions. The linear model was suitable for the char yield distribution without interaction. Thus, this study reveals that RSM has a significant potential to predict pyrolyzate yields, enabling co-pyrolysis condition setting to maximize the desired product recovery with the fewest experiments., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

• Feedstock recycling (pyrolysis) scenarios for plastic packaging waste are designed. • Greenhouse gas emissions are evaluated based on results of a pyrolysis experiment. • Oil substitution by pyrolysis products and surplus heat utilization are considered. • Conditions in which feedstock recycling achieves net zero emission are determined. • Surplus heat needs to be highly utilized to maximize the environmental benefits. Focusing on plastic packaging waste, this study aimed to design feedstock recycling scenarios by harnessing industrial processes in a region and to specify the technological requirements to obtain climate benefits. The amount and resin composition of plastic packaging waste that could be collected from the region surrounding an oil refinery and sorted using different sorting schemes were projected. A pyrolysis experiment using samples tailored to mimic the projected composition and distillation test of the obtained oil were conducted. Then, greenhouse gas emissions in various pyrolysis scenarios were evaluated considering oil substitution by pyrolysis products and surplus heat utilization. Results indicated that, when the amount and quality of pyrolysis oil were appropriately adjusted by two-step preliminary sorting of plastic packaging waste and surplus heat could be utilized as substitute for fossil fuels at the refinery, the technological requirement to achieve net zero emission by the feedstock recycling were alleviated. [ABSTRACT FROM AUTHOR]

With the ever-growing concern regarding plastic waste and its impact on the environment, understanding the degradation pathways of polyimide (PI)-based plastics becomes increasingly crucial for developing sustainable waste management strategies. This study investigated the thermo-oxidative degradation of PI-based plastics, including PI, polyamide-imide (PAI), and polyetherimide (PEI). We used techniques including thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy, an in situ heated electron spin resonance spectrometer, and a customized pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) system. The TGA results revealed that the onset degradation temperature of PI-based plastics exceeded 460 °C. The degradation of PI was promoted under air, while the degradation of PAI was delayed. For PEI, the degradation under air coincided with its initial decomposition under N 2 , followed by the oxidation of the residual solid. Changes in the chemical structures were revealed during the characterization of the samples treated above 400 °C. The residual char, obtained in high yield, notably contained N-rich functional groups. Real-time analysis using Py-GC/MS revealed that the pyrolysis of the plastics produced gases such as NH 3 , HCN, H 2 O, CO, and CO 2 , with NH 3 and HCN being converted into NO x under an atmosphere of air. The pyrolysis of PI and PAI generated N-containing compounds, including aromatic amines, nitriles, and phthalimides. In contrast, the pyrolysis of PEI produced various phenolic compounds owing to the presence of the aromatic ether groups. The newly formed p -benzoquinone, CO 2 , H 2 O, and NO x were identified under air. This study provides comprehensive insights into the unique thermal and oxidative stabilities of PI-based plastics and holds the potential for recovering high-value N-containing materials from waste PI-based plastics. • Thermo-oxidative degradation of polyimide-based plastics was investigated. • Changes in chemical structures occurred over 400 °C and improved in air. • Residual char obtained in high yield contained N-rich functional groups. • Customized Py-GC/MS revealed distinct degradation steps under various atmospheres. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Polyurethanes (PUs) were converted into H 2 -rich syngas. • Toxic HCN was highly removed simultaneous with H 2 -rich syngas production. • Ni/Mg/Al catalysts simultaneously achieved H 2 -rich syngas recovery and HCN removal. • Synergy between Ni, Mg, and Al in the catalysts show excellent performance. • Variety of PUs (flexible and rigid forms and elastomers) were treated by this process. Abstract Polyurethanes (PUs) such as flexible (cushioning material and sponge) and rigid (different insulators) forms and elastomers (flexible tube and smartphone case) were thermally decomposed at 500 °C. The useless decomposition products were converted into H 2 -rich syngas and the toxic HCN in it was removed by Ni/Mg/Al catalysts at 800 °C under 50 vol% steam/He flow. The resultant total gas production was 1411–1623 mL/g (H 2 : 794–967 mL/g), which was almost 30 times larger than that obtained from simple pyrolysis of PUs where no H 2 was produced. Meanwhile, there was a drastic reduction of HCN concentration in the product gas from a maximum at 2.8 to 0.2–0.6 vol%. The excellent performance on the removal of HCN and the enhanced H 2 -rich syngas production is due to the synergy between Ni, Mg, and Al in the catalysts. This approach has great promise for treating a variety of PU wastes that cannot be recycled effectively otherwise. [ABSTRACT FROM AUTHOR]

This article describes the production and properties of gases produced by the pyrolyses of poly(ethylene terephthalate) (PET), polypropylene (PP), polyethylene (PE), poly(vinyl chloride) (PVC), and polystyrene (PS), and three of their mixtures at process temperatures of 500, 700, and 900 °C. The overall aim was to characterize all 24 gases in terms of their production and physical properties, and compare the data obtained to those of traditional fuels, namely natural gas (NG) and propane. In addition to experimental and analytical approaches for determining quantities and compositions of the pyrolysis products, various mathematical methods and their combinations were also used to determine product properties. The highest conversion of material into gas occurred during the pyrolysis of PP at 900 °C (66.88 wt% conversion into gaseous products). The pyrolyses of PE and PP at 500 °C were found to generate pyrolysis gases with the highest energy, with gross calorific values of 86.58 and 81.09 MJ m −3 N , respectively. The highest chemical energy yield was obtained by the pyrolysis of PP at 900 °C. Gases produced from PVC had a high thermal conductivity of about 104.83 mW m −1  K −1 . The gas generated from PP at 500 °C exhibited a high specific heat of 2.94 kJ m −3 N  K −1 , and that obtained from PS at 500 °C had a very low kinematic viscosity (5.28 10 −6  m 2  s −1 ) and thermal diffusivity (7.90 10 −6  m 2  s −1 ). Even though numerous reports have dealt with pyrolysis gases, there is still not sufficient information about the specific physical properties of these gases. This article attempts to fill this gap and induce scientific interest in this field. [ABSTRACT FROM AUTHOR]

The current energy industry relies heavily on fossil fuels. As reserves of fossil fuels are diminishing, the demands for alternative forms of energy are growing. Therefore, the search for alternative fuels is crucial. This article discusses pyrolysis gases generated from major plastics as possible future successors to fossil fuels. The novelty of this study lies in the comprehensive discussion of the fuel characteristics of different pyrolysis gases that are so far unpublished. The article builds on Part I, which predominantly focused on the production and physical properties of pyrolysis gases from plastics. Various properties are determined by combining experimental and mathematical methods. An interesting aspect of the gases produced from poly(ethylene terephthalate) (PET) is their high upper flammability limits, which are 61.46% on average. Gases from poly(vinyl chloride) (PVC) are characterized by very high laminar burning velocities, with an average value of 178.62 cm s −1 , which is about five times higher than that of natural gas (NG). Gases produced from PVC at 500 and 700 °C have autoignition temperatures almost identical to that of NG. Furthermore, the results presented in this article show that, according to standards proposed by the California Air Resources Board and the Gas Research Institute, none of the pyrolysis gases are suitable fuels for gas engines, because the methane number of no gas meets the minimum value of 65 required in the EU and USA. This article discusses results valuable for determining the potential suitability of pyrolysis gases for use in power-engineering facilities, including combustion engines, and includes information on further research prospects. [ABSTRACT FROM AUTHOR]

A study of the morphology changes in polyurethane elastomers (PUEs) containing different hard- and soft-segment ratios during ramped-heating pyrolysis revealed that selectivity of urethane bond cleavage is controlled by only the segment composition. Several PUEs were synthesized using 4,4′-diphenylmethane diisocyanate, 1,4-butanediol, and poly(oxytetramethylene glycol) (PTMG) to examine the influence of segment composition on pyrolysis characteristics by pyrolysis–gas chromatography/mass spectrometry, evolved gas analysis–mass spectrometry, and isoconversional kinetic studies. Soft-segment-rich PUEs tended to undergo urethane bond cleavage via a 4-membered-ring transition state, while the linkages in other compositions were selectively cleaved via a 6-membered-ring transition state. The reaction selectivity can be explained by the different conformations of the urethane bonds: in the hard-segment domains by H-bonds between urethane unit N H and C O groups, and in soft-segment-rich environments by H-bonds between urethane N H groups and PTMG O linkages. The mechanism of PTMG pyrolysis was the same for all PUEs. [ABSTRACT FROM AUTHOR]

Pyrolysis is an important method for breaking down organic waste to obtain useful low molecular weight compounds. To investigate the pyrolysis behavior of bisphenol A (BPA) and BPA pyrolysates at low pyrolytic temperatures, BPA and p -isopropenyl phenol (IPP) were pyrolyzed at 240–320 °C using a batch reactor. BPA decomposition was strongly enhanced at temperatures higher than 240 °C, and was almost complete after 30 min at 320 °C. Theoretically, pyrolysis of BPA gives phenol (PhOH) and IPP in a 1:1 molar ratio, corresponding to yields of 41 wt% PhOH and 59 wt% IPP. However, an unexpectedly low IPP yield (∼10 wt%) was obtained experientially, with a simultaneous increase in the yields of high molecular weight compounds. Compounds resulting from IPP polymerization were detected using electrospray ionization time-of-flight mass spectrometry (ESI-TOF-MS), suggesting that IPP was rapidly polymerized into high molecular weight compounds via radical propagation. On the other hand, a maximum PhOH yield of 62 wt% was obtained after 30 min at 320 °C, which is higher than the theoretical yield. As direct dealkylation of IPP is difficult, the excess PhOH is likely derived from thermal decomposition of the IPP polymerization products. Thus, the present work revealed the high reactivity of IPP for polymerization at pyrolytic temperatures, which facilitates increased recovery of PhOH from BPA. [ABSTRACT FROM AUTHOR]

The recycling of N -containing plastics by pyrolysis or steam-reforming is typically complicated by the generation of toxic HCN. In this study, polyimide, as an example of an N -containing plastic, was gasified and the product gas was reformed over various Ni/Mg/Al catalysts. Effects of catalyst properties, steam, and temperature on the HCN removal and H 2 -rich syngas production were investigated. More than 99% HCN removal (compared with pyrolytic conditions) and ∼3000 mL g −1 of H 2 -rich syngas with a H 2 /CO ratio of 10.4 were simultaneously achieved at 800 °C in the presence of a reduced-Ni 1.0 Mg 3.6 Al 4.8 catalyst, then HCN was mainly converted into N 2 . On the other hand, non-reduced same catalyst enhanced hydrolysis of HCN into NH 3 with more than 98% HCN removal at 800 °C, which is also a beneficial finding to recover useful NH 3 from HCN, directly. Therefore, the present work achieved that the improvement of the H 2 -rich syngas yield and quality, and conversion of toxic HCN into non-toxic N 2 or useful NH 3 using the same catalyst, simultaneously. [ABSTRACT FROM AUTHOR]

To investigate the interactions between beech wood (BW) and polyethylene (PE) during co-pyrolysis, they were pyrolyzed both individually and as their mixtures from ambient temperature to 650 °C at a heating rate of 10 °C min −1 using a thermogravimetric analyzer and a tube reactor. In the presence of PE, the production of levoglucosan (LG) and methoxyphenols with unsaturated alkyl side chains from BW was enhanced, resulting in maximum 1.65 and 1.55 times higher yields comparing with their expected yields from BW:PE (w:w) = 40:60 mixture, respectively. It was due to the stabilization of the radical species of those by H-abstraction from the PE pyrolysates in the vapor phase. According to this, CO, CO 2 , C 2 -C 3 compounds, and 5-membered ring compounds, which are LG decomposition products, showed 0.86, 0.85, 0.58, and 0.68 times smaller yields comparing with their expected yields. Methoxyphenols with saturated alkyl side chains, phenols, and catechols, also showed 0.77, 0.66, and 0.87 times smaller yields because they are mainly derived from methoxyphenols with unsaturated alkyl side chains. On the other hand, it was suggested that hydrogen radicals produced during the polyaromatization of BW stabilized PE radical species, resulting in products from PE with higher carbon numbers. Thus, the present work reveals that the interactions between BW and PE mainly involve H-exchange to stabilize radical species. These findings increase our understanding of the operative mechanism in the co-pyrolysis of lignocellulosic biomass and synthetic polymers, which will be useful in future for achieving pyrolysis reaction control and recovering desirable products from difficult-to-separate initial mixtures. [ABSTRACT FROM AUTHOR]

The use of sulfur-based plastics has led to the accumulation of end-of-life sulfur-based plastic waste that should ideally be recycled. In this study, several technologies were applied to investigate the thermal-oxidative degradation property of sulfur-based plastics (polyphenylene sulfide (PPS), polyether sulfone (PES), and polysulfone (PSU)). Thermogravimetric analysis (TGA) revealed that these plastics undergo major decomposition at 450–650 °C under N 2 , whereas two-stage weight loss at 450–690 °C was observed in air. X-ray photoelectron spectroscopy (XPS) and in-situ radical monitoring by heated electron spin resonance (heated-ESR) spectroscopy revealed that the samples had altered their chemical structures, and that radicals are involved in samples treated at low temperature (≤ 400 °C). The thermo-oxidative products were analyzed by customized pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). PPS pyrolysis mainly produced sulfur-containing aromatic compounds, with H 2 O, CO 2 , and SO 2 released during two-stage degradation in air, which suggests that pyrolysis and oxidation occur simultaneously during the first stage. PES pyrolysis generated various oxygen-containing products, whereas the oxidation of PES resulted in a great number of furans and dioxins at the expense of phenolics. Extensive evolution of SO 2 was initially observed, irrespective of the degradation atmosphere. PSU pyrolysis produced various aromatics, phenolics, and esters, with SO 2 formed as the major sulfur-containing compound, which was released at a lower temperature (∼50 °C) in air compared to N 2 , confirming that PSU is less thermally stable than PPS and PES in air, as observed by TGA. The thermo-oxidative degradation behavior of sulfur-based plastics was comprehensively characterized by combining conventional techniques (TGA and XPS) with advanced analytical technologies (heated-ESR and customized Py-GC/MS). • The thermo-oxidative degradation of sulfur-based plastics was investigated. • Heated-ESR spectroscopy revealed excited radicals at low temperature. • Thermo-oxidative products were analyzed online using customized Py-GC/MS. • The release of products formed in different atmospheres was studied. [ABSTRACT FROM AUTHOR]

The global increase in natural gas (NG) consumption and its steady decline in availability have spurred the search for new or alternative energy sources, such as pyrolysis gases. This article examines whether it is possible to burn pyrolysis gases from common plastic wastes in conventional burners without any adjustment to burner design. To determine the interchangeability of individual gases, several multi-index methods applicable to combustion devices in Europe, the USA, and the UK were used. This report is a continuation of a previous article (Part I) discussing the results of graphical methods for determining interchangeability. Similar to Part I, the results here imply that poly(vinyl chloride) (PVC) gases produced at a minimum of 700 °C have the highest replacement potential, and gases produced by polystyrene (PS) pyrolysis at 900 °C also conform with replacement requirements. For plastics mixtures, gases generated by pyrolysis at a minimum of 700 °C would be suitable alternatives to NG. These findings may contribute to plastic waste reduction as well as the discussion of reducing NG consumption. There is significant potential for follow-up research in this area, because the replacement of conventional fuels with gases obtained from wastes has not yet been sufficiently explored. [ABSTRACT FROM AUTHOR]

The development of effective recycling methods for plastic wastes is critical in terms of resource security and environmental conservation. In this work, we focused on the gaseous pyrolysis products of plastic wastes as alternatives to natural gas (NG) and propane. The pyrolysis of polyethylene (PE), polypropylene (PP), polystyrene (PS), poly(vinyl chloride) (PVC), poly(ethylene terephthalate) (PET), and their mixtures was carried out under isothermal conditions at 500, 700, and 900 °C. The potential for replacing NG and propane with the pyrolysis gases was assessed by graphical interchangeability methods for the first time. The pyrolysis gas compositions obtained from the mixed plastics and HCl-scrubbed gas from the PVC were deemed suitable NG alternatives in Europe and the USA. In addition, PE and PP pyrolysis gases showed the potential for replacing propane in the USA, whereas gases from PET showed the least interchangeability. Thus, the graphical interchangeability methods are promising for evaluating the potential of plastic waste pyrolysis gases as alternatives to NG. [ABSTRACT FROM AUTHOR]

Kapton film, which is a typical aromatic polyimide (PI) film, exhibits excellent thermal stability and flexibility. Therefore, it is used widely for flexible printed circuit boards in combination with other resins and metals. However, this makes it difficult to recycle it. In this work, we focused on the steam pyrolysis technique, which is a method of depolymerizing condensation polymers without solvents, catalysts, or high pressure, as a way of overcoming this issue. The steam pyrolysis of Kapton film was carried out using a thermogravimetric (TG) analyzer equipped with a steam generator. In addition, the TG results were evaluated further using model fitting techniques. It was found that steam enhanced the hydrolysis of the imide ring, which occurred on the surface of the PI film. The hydrolysis selectivity was as high as 89% at 528 °C. However, steam did not significantly enhance the Kapton decomposition rate, owing to rapid carbonization, which took place because of the simultaneous occurrence of pyrolysis. Thus, the obtained results implied that high-yield monomer recovery can be achieved by lowering the temperature to prevent pyrolysis and by improving the steam contact efficiency to enhance hydrolysis within the material. [ABSTRACT FROM AUTHOR]

A Ni–Mg–Al–Ca catalyst was prepared by a co-precipitation method for hydrogen production from polymeric materials. The prepared catalyst was designed for both the steam cracking of hydrocarbons and for the in situ absorption of CO 2 via enhancement of the water–gas shift reaction. The influence of Ca content in the catalyst and catalyst calcination temperature in relation to the pyrolysis–gasification of a wood sawdust/polypropylene mixture was investigated. The highest hydrogen yield of 39.6 mol H 2 /g Ni with H 2 /CO ratio of 1.90 was obtained in the presence of the Ca containing catalyst of molar ratio Ni:Mg:Al:Ca = 1:1:1:4, calcined at 500 °C. In addition, thermogravimetric and morphology analyses of the reacted catalysts revealed that Ca introduction into the Ni–Mg–Al catalyst prevented the deposition of filamentous carbon on the catalyst surface. Furthermore, all metals were well dispersed in the catalyst after the pyrolysis–gasification process with 20–30 nm of NiO sized particles observed after the gasification without significant aggregation. [ABSTRACT FROM AUTHOR]

Individual and mixed plastics consisting of polyethylene (PE), polypropylene (PP), polystyrene (PS), and poly(ethylene terephthalate) (PET) were decomposed at 600 °C in the presence and absence of either calcium oxide (CaO) or calcium hydroxide (Ca(OH) 2 ) under a steam atmosphere. In the presence of CaO, steam cracking was enhanced, increasing gas and liquid yields and decreasing the wax content derived from PE and PP. The production of sublimating substances from PET was also reduced. However, the presence of CaO and steam had a negative influence on PS degradation, reducing the oil yield. In addition, synergistic effects were observed in plastic mixtures. PET enhanced gasification, PS and PET reduced wax production from PE and PP, and mixing all four plastics enhanced oil production in the presence of CaO and steam. Both CaO and Ca(OH) 2 enhanced the total gas and oil yield of mixed plastics, achieving a maximum oil yield of 52.2 wt% in the presence of steam. Furthermore, solids were almost completely decomposed at 700 °C, with only 0.2 wt% of residue remaining. [ABSTRACT FROM AUTHOR]

Abstract: The addition of plastics to the steam pyrolysis/gasification of wood sawdust with and without a Ni/Al2O3 catalyst was investigated in order to increase the production of hydrogen in the gaseous stream. To study the influence of the biomass/plastic ratio in the initial feedstock, 5, 10 and 20 wt.% of polypropylene was introduced with the wood in the pyrolysis reactor. To investigate the effect of plastic type, a blend of 80 wt.% of biomass and 20 wt.% of either polypropylene, high density polyethylene, polystyrene or a mixture of real world plastics was fed into the reactor. The results showed that a higher gas yield (56.9 wt.%) and a higher hydrogen concentration and production (36.1 vol.% and 10.98 mmol H2 g−1 sample, respectively) were obtained in the gaseous fraction when 20 wt.% of polypropylene was mixed with the biomass. This significant improvement in gas and hydrogen yield was attributed to synergetic effects between intermediate species generated via co-pyrolysis. The Ni/Al2O3 catalyst dramatically improved the gas yield as well as the hydrogen concentration and production due to the enhancement of water gas shift and steam reforming reactions. Very low amounts of coke (less than 1 wt.% in all cases) were formed on the catalyst during reaction, with the deposited carbonaceous material being of the filamentous type. The Ni/Al2O3 catalyst was shown to be effective for hydrogen production in the co-pyrolysis/gasification process of wood sawdust and plastics. [Copyright &y& Elsevier]

Polycarbonate (PC) is an engineering thermoplastic that is widely used in electrical and electronic equipment. This plastic often contains tetrabromobisphenol A (TBBA), the most common brominated flame retardant. Thermal degradation of the PC-TBBA leads to generation of numerous bromo-organic products in the pyrolytic oil, hindering its appropriate utilization, as well as corrosive hydrogen bromide gas. The purpose of this study was to experimentally investigate and compare the pyrolysis products of PC-TBBA and PC-TBBA + Cu 2 O at various temperatures, with an emphasis on the yield and distribution of brominated compounds. In pyrolysis of PC-TBBA + Cu 2 O, at the maximum degradation temperature (600 °C), as much as 86% of total Br was trapped in the residue, while 3% and 11% were distributed in the condensate and gas fractions, respectively. In contrast, the distribution of Br from non-catalytic pyrolysis of PC-TBBA (600 °C) was 0.5% residue, 40% condensate, and 60% gas. The results of this study revealed that in the presence of Cu 2 O, organo-bromine products were most likely involved in Ullman-type coupling reactions, leading to early cross-linking of the polymer network that efficiently hinders their vaporization. HBr in the gas fraction was suppressed due to effective fixation of bromine in residue in the form of CuBr. ga1 • Cu 2 O significantly alter the pyrolysis of bromine-containing PC polymer. • Cu 2 O mediates cross-coupling of bromo-organics at early stage of pyrolysis. • Cu 2 O significantly reduces vaporization of bromo-organic products and HBr gas. • Cu 2 O utilizes efficiently CO in reduction reactions, favoring CO 2 generation. [ABSTRACT FROM AUTHOR]

• PU elastomers with different hard segment (HS) domain structures were prepared. • Fast and slow pyrolysis of the synthesized polyurethane elastomers were conducted. • There was no significant difference in type of pyrolysates between the samples. • HS selectively produced compounds with isocyanate end group at around 280–340 °C. • Pyrolysis of HS domain and HS in soft segment occurred at different temperatures. The pyrolysis behaviors of seven kinds of polyurethane elastomers (PUEs) with different ratios between the hard segment (HS) and soft segment (SS) were investigated for both fast pyrolysis (300, 350, 450, 850 °C) and slow pyrolysis at the heating rate of 10 °C min–1 by thermogravimetric analysis (TG), pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS), and evolved gas analysis-mass spectrometry (EGA-MS). These PUEs were synthesized from 4,4′-diphenylmethane diisocyanate (MDI), 1,4-butane diol (BD), and poly(oxytetramethylene glycol) (PTMG). Atomic force microscopy measurements found that the HS domains were formed in PUEs containing HS, and these domains were aggregated at extremely high HS ratio. The main pyrolysate derived from HS was MDI under all conditions. In fast pyrolysis tests, the decomposition of SS proceeded sufficiently at 450 °C, and a lot of low molecular weight compounds were produced at 850 °C. In slow pyrolysis tests, three-step degradation was observed, and this degradation behavior was influenced by the HS domain and SS matrix structures. The first step is the HS pyrolysis inside the HS domain, then the HS surrounded by SS is pyrolyzed. Finally, the SS matrix is pyrolyzed. The HS pyrolysates changed from isocyanate to amine with increasing temperature. We believe that the newly found pyrolysis behavior of PUEs with different ratios between the HS and SS will promote future studies on the characterization of PUE materials and the pyrolytic recovery of chemical feedstock from PUE wastes. [ABSTRACT FROM AUTHOR]

Chitosan-cellulose composite fibers spun using a Lyocell technology are characterized by a homogeneous distribution and a close packing of the two biopolymers inside the fibrous matrix. Due to the intimate contact of cellulose and chitosan, synergistic effects can be observed during the pyrolysis of the composite fibers. In this study, the catalytic role of chitosan in altering the cellulose pyrolysis pathway in the composite fibers at moderate treatment temperatures up to 900 °C is confirmed. Analyses of the evolved gases during pyrolysis revealed that chitosan promoted cellulose dehydration and substantially decreased the formation of levoglucosan, explaining the higher char yield. The enhanced dehydration reaction is associated with the formation of intermolecular crosslinks due to the incorporation of nitrogen from chitosan in the resulting carbon structures. Nitrogen could also contribute to the in-plane disorder in the aromatic clusters when the pyrolysis is carried out at 500–700 °C, although the in-plane disorder is less noticeable from 700 to 900 °C. Nevertheless, the size of the aromatic cluster continues to grow when the composite fibers are pyrolyzed in a temperature range of 500–900 °C. [Display omitted] [ABSTRACT FROM AUTHOR]