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Dechlorination of PVC Using NaOH/EG Solution 60),62 ) : (a) Simple Dechlorination System; (b) Ball-mill Assisted Dechlorination System; (c) Dechlorination Behavior of Flexible PVC in the Presence and Absence of Ball-milling; (d) Dechlorination Behavior of Rigid PVC in the Presence and Absence of Ball-milling
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Recycling of waste plastics is essential for reducing environmental degradation and ensuring future resource security. The quantity of domestic plastic waste recycled is increasing yearly, reaching 83 % in 2014. However, only 26 % and 4 % of the recycled waste plastic is treated by mechanical and feedstock recycling, respectively, whereas 70 % is t...
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![Fig. 1. Incineration of MSW in % [5].](profile/Maurizio-La-Villetta/publication/324529657/figure/fig1/AS:615644068335636@1523792392862/Incineration-of-MSW-in-5_Q320.jpg)
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... As a result of using PVC in a wide variety of fields, the uncontrollable release of this polymer into the environment as scraps of various origin or microplastic has become a serious problem. Thermal treatment, such as pyrolysis, gasification or incineration, of PVC-containing waste results in energy recovery, and PVC can be used as a hydrocarbon source [2]. However, a high chlorine content in the PVC (57 wt.% [3]) posts additional drawbacks for this way of utilization. ...
Polyvinyl chloride (PVC) plays an important role in industry; however, due to its uncontrolled accumulation in the environment, the methods for its utilization are of high demand. Herein we wish to report an approach for the utilization of PVC via its use as a carrier for some azole-based drugs, such as 2-mercaptobenzothiazole (multi-activity drug), 4-oxo-1,4-dihydropyrazolo[5,1-c]-1,2,4-triazine-3,8-dicarboxylic acid diethyl ester (antidiabetic drug) and 5-methyl-6-nitro-7-oxo-1,2,4-triazolo[1,5-a]pyrimidinide (antiviral drug). The abovementioned approach involves the reaction between PVC and potassium or sodium salts of these azole-based drugs either in solution or under ball-milling conditions. The as-obtained PVCs modified with azole-based drugs were isolated for the first time and characterized by means of 1H NMR-spectroscopy as well as gel-permeation chromatography (GPC).
... However, as for the detailed analyses of the disposed waste and pyrolysis products, a number of thermal decomposition studies have been reported using pure plastics, especially polyethylene (e.g., Cheng et al., 2020;Park et al., 2019;Abbas-Abadi et al., 2013), pure sewage sludge (Zaker et al., 2019;Inguanzo et al., 2002), or sewage sludge mixed with pure plastics (e.g., Honus et al., 2018;Kumagai and Yoshioka, 2016;Miandad et al., 2016;Ahmad et al., 2014;Huang et al., 2010). The problem is, though, that in the real conditions, even separated waste tends to be 'contaminated' to a certain extent by other types of waste. ...
Using waste as an alternative energy source may partially replace fossil fuels. In this paper, energy recovery from waste blends (sewage sludge (SS), polyethylene (LDPE) and polypropylene (PP), paper rejects (PR), and waste tyres) was tested through laboratory-scale co-pyrolysis. For each copyrolysis test, 7 l of waste blend in different ratios were used. The results of pyrolytic oil and gas analyses show valuable compounds and chemical materials recovered. The detailed analyses show the effects of co-pyrolysis parameters, especially the ratios of waste blends with respect to the process temperature of 600◦C, on the pyrolytic gas and oil. The highest volumes of gas (0.66 m3) and oil (699 ml) were obtained from sample 5_8 (PES:SS:PR). Waste blend 15_1 (LDPE:SS) had the highest gross calorific value (GCV) of 43.82 MJ/m3 in gas, and had the highest proportion of flammable components (46.31% of methane). Sample 5_8 had the highest calorific value in pyrolytic oil (45 MJ/kg) and sample 5_3 had the lowest (28.113 MJ/kg), which is comparable to coal. High-quality pyrolytic gas and oil were obtained with average GCV of 44 MJ/m3 and 40 MJ/kg respectively, where the average GCV of the most calorific fossil fuels is 43.6 MJ/kg in crude oil and 34 MJ/m3 in natural gas. We conclude that co-pyrolysis of sewage sludge and waste is a convenient and simple method of waste disposal under a synergetic effect of efficient waste management, energy production, and reduction of dependence on fossil fuels,
... Pyrolysis is a promising method for recycling plastic waste to obtain chemical feedstocks and fuels. This method is not sensitive to feedstock quality, and the product can be tuned by changing the reactor type, operating conditions, or catalysts [16][17][18]. The pyrolysis of PLA and poly(hydroxyalkanoate) (PHA), the most prevalent biobased/ biodegradable plastics, has been investigated. ...
The introduction of biodegradable plastics is considered a practical approach to reducing plastic waste accumulation in the environment. Regardless of their biodegradability, plastics should be recycled to effectively utilize and circulate carbon as a resource. Herein, the use of pyrolysis was examined as a method for recycling two common biobased/biodegradable plastics: PLA and PHBH. The pyrolysis of PLA produced lactides (10.7 wt% at 400 °C), but the yield was decreased when the pyrolysis temperature was increased. The presence of steam promoted the hydrolysis of PLA: a steam concentration of 25 vol % increased, the production of lactides at 400 °C to 17.4 wt%. The pyrolysis of PHBH primarily yielded crotonic acid (30.1 wt% at 400 °C), and the yield increased with increasing pyrolysis temperature (71.8 wt% at 800 °C). Steam injection increased the hydrolysis of oligomers, resulting in a 76.1 wt% yield of crotonic acid at 600 °C with a steam concentration of 25 vol %. Thus, we determined that hydrolysis and pyrolysis progress simultaneously under a steam atmosphere, increasing the chemical feedstock recovery from PLA and PHBH. These findings may lead to the proposal of effective degradation methods for treating biobased/biodegradable plastic wastes and ways to maximize the conversion efficiency and target product yields.
... Essentially, low-temperature pyrolysis (e.g., between 250 and 350 • C) can be used to substantially remove chlorine via dehydrochlorination and prevent HCl from breaking C-H and C--C bonds to form chlorinated hydrocarbons . Nevertheless, thermal pretreatment cannot completely remove chlorine partly because some isolated chlorine atoms are locked in the remaining structure due to cyclization and cross-linking during thermal degradation (Kumagai and Yoshioka, 2016), and this fraction was estimated to be at least 2 % by weight (Westerhout et al., 1998). In addition, long processing time often causes secondary transformation of the primary pyrolysis volatiles by reaction with gases or char, resulting in the formation of organochlorine compounds (Zhou et al., 2020). ...
... A wide variety of polyolefin upcycling processes have been proposed in recent years. Pyrolysis involves treating the polymer at high temperatures, either with or without catalyst, yielding a mixture of gases, char, and liquid alkanes, olefins, and aromatics [24][25][26] . Although this method is straightforward, the high energy requirement and low product selectivity may limit the commercial potential of pyrolysis processes. ...
The dehydrogenation of long-chain alkanes to olefins and alkylaromatics is a challenging endothermic reaction, typically requiring harsh conditions which can lead to low selectivity and coking. More favorable thermodynamics can be achieved by using a hydrogen acceptor, such as ethylene. In this work, the potential of heterogeneous platinum catalysts for the transfer dehydrogenation of long-chain alkanes is investigated, using ethylene as a convenient hydrogen acceptor. Pt/C and Pt–Sn/C catalysts were prepared via a simple polyol method and characterized with CO pulse chemisorption, HAADF-STEM, and EDX measurements. Conversion of ethylene was monitored via gas-phase FTIR, and distribution of liquid products was analyzed via GC-FID, GC-MS, and 1H-NMR. Compared to unpromoted Pt/C, Sn-promoted catalysts show lower initial reaction rates, but better resistance to catalyst deactivation, while increasing selectivity towards alkylaromatics. Both reaction products and ethylene were found to inhibit the reaction significantly. At 250 °C for 22 h, TON up to 28 and 86 mol per mol Pt were obtained for Pt/C and PtSn2/C, respectively, with olefin selectivities of 94% and 53%. The remaining products were mainly unbranched alkylaromatics. These findings show the potential of simple heterogeneous catalysts in alkane transfer dehydrogenation, for the preparation of valuable olefins and alkylaromatics, or as an essential step in various tandem reactions.
... Plastics were pyrolyzed at high temperature, above 400 °C, in an anoxic or anaerobic environment to produce gas, liquid, and coke (Choi et al. 2021). Pyrolysis of plastics was currently the most used and had also been scaled up from laboratory to industrial levels (Kumagai and Yoshioka 2016). During the pyrolysis process, various temperatures and times produced different products, and representative studies focusing on the effects of temperature and time are summarized in Table 1. ...
Substantial quantities of discarded plastic have resulted in detrimental effects on the environment and ecosystems, calling for effective recycling of plastic wastes. Chemical methods for managing plastic wastes have been extensively studied, and selective recycling of products has grown in popularity. Pyrolysis, photocatalysis, and supercritical fluids were the main chemical methods reported for processing plastics. This article reviews reaction mechanisms and representative studies of pyrolysis, photocatalysis and supercritical fluid disposal of plastics. Three challenges are identified: first, high temperatures, above 400 °C, pose safety risks and potentially release harmful gases. Second, the photocatalytic decomposition of plastics is generally economical and environmentally friendly, however, reaction rates are uncontrollable. Third, the exceptional solubility and mass transfer properties exhibited by supercritical fluids have the potential to significantly augment the decomposition of plastics. Supercritical fluids can also serve as reactants that directly influence the thermal or kinetic mechanisms of the reaction. Whereas individual treatment methods are limited, coupled methods enable efficient plastic management and facilitate the selective acquisition of products. In particular, this review suggests that coupling photocatalysis and supercritical carbon dioxide should allow to dispose of plastics and convert carbon dioxide into valuable resources.
... For the recycling of waste plastics, researchers have made many efforts and applied them to several industries [1][2][3]. Passamonti F. J. et al. applied used low-density polyethylene (LDPE) to gas oil to investigate the effect of the application of used LDPE on the yield of different products from gas oil. The study's conclusions indicate that adding waste LDPE can significantly enhance the generation of dry gas and gasoline and enable the use of waste PE in fuel [4]. ...
In this work, waste polyethylene (PE)-modified 90# asphalt was made in order to investigate the performance of waste polyethylene-modified high-grade asphalt and the optimal blending quantity. Dynamic Shear Rheology (DSR) and Bending Beam Rheometer (BBR) tests were used to evaluate the high- and low-temperature performance of modified 90# PE-modified asphalt. Infrared spectroscopy and fluorescence microscopy were used to investigate the modification process and distribution status of waste PE in 90# asphalt. The DSR and BBR tests revealed that waste PE enhanced the high-temperature performance of 90# base asphalt and that 5% was the best blending rate. However, the change affects asphalt’s low-temperature performance, and the negative effect on asphalt’s low-temperature performance was minimized at 1% dosing. The incorporation of waste PE absorbed the light components of asphalt, while waste PE can form a reticulated structure in asphalt, which improves its high-temperature performance but degrades its low-temperature performance, according to the results of infrared spectroscopy and fluorescence microscopy.
... Chemical recycling of PVC waste is challenging owing to the high chlorine content and various additives (Nozue and Tagaya, 2021;Lu et al., 2021;Kumagai and Yoshioka, 2016). Many outstanding reviews have been conducted on the chemical recycling of plastic waste recently (Miandad et al., 2016;Lopez et al., 2018;Zhang et al., 2022;Hou et al., 2021;Chen et al., 2021a;Albright and Chai, 2021;Vollmer et al., 2020;Pan et al., 2020;Chen et al., 2020;Wang et al., 2022;Lee et al., 2021;Rahimi and García, 2017;Ignatyev et al., 2014;Sun et al., 2021). ...
The extensive production and consumption of plastics has resulted in significant plastic waste and plastic pollution. Polyvinyl chloride (PVC) waste has a high chlorine content and is the primary source of chlorine in the plastic waste stream, potentially generating hazardous chlorinated organic pollutants if treated improperly. This review discusses PVC synthesis, applications, and the current types and challenges of PVC waste management. Dechlorination is vital for the chemical recycling of PVC waste and PVC-containing plastic waste. We review dehydrochlorination and dechlorination mechanisms of PVC using thermal degradation and wet treatments, and summarize the recent progress in chemical treatments and dechlorination principles. This review provides readers with a comprehensive analysis of chemical recycling technologies for PVC waste and PVC-containing plastic waste to transform them into chemicals, fuels, feedstock, and value-added polymers.
... Pyrolysis (or thermal cracking) refers to the irreversible chemical decomposition caused solely by a rise in temperature [95]. It is not incineration, as the plastic waste is thermochemically decomposed without oxygen [109]. Depending on the applied treatment method, pyrolysis occurs between 200 • C and 1300 • C. Pyrolyzing plastic waste at temperatures of 500 • C and lower produces liquid oil, while exceeding 500 • C produces more gaseous or char products such as gas, wax, and coke [110,111]. ...
Achieving plastic circularity is imperative to using plastics without adverse effects. Today, only 9% of global plastic waste is recycled, signifying the need for more substantial advancements to accelerate our progress toward achieving plastic circularity. This article contributes to our collective efforts to accelerate plastic circularity by critically assessing the state-of-the-art, gaps, and outlook of the pathways and processes to circular plastics. It employs qualitative methods to derive new insights that empower scholars and practitioners to prescribe effective strategies to shape the future of plastic circularity and its research agenda. This article concludes that today’s circularity pathways for plastics are not economically viable, significantly hindering their scalability and widespread adoption. It further validates that focusing on the product design and effectiveness of the available collection and sorting systems can considerably improve our progress in achieving plastic circularity.
... Based on this situation, plastic products are facing the problem of a large production volume with a low recovery rate. At present, the widely used plastic treatment methods 4,5 are incineration, landfill disposal, degradation, and thermal cracking, while the recycling technology includes simple classification, recycling, and composite regeneration ( Table 1). The garbage landfill method 6 necessitates the treatment of numerous land resources, the blocking and pollution of groundwater, and the infiltration and waste of a large amount of recyclable plastic waste resources. ...
Recycling plastic waste efficiently and cleanly is one of the key ways to reduce environmental pollution and carbon emissions. At present, the disposal methods of waste plastics mainly include landfill,...
