Conversion Of Waste Plastics Research Articles

Depolymerization of PET with n-Hexylamine, n-Octylamine, and 3-Amino-1-Propanol, Affording Terephthalamides

The chemical conversion of plastic waste has been considered an important subject in terms of the circular economy, and the chemical recycling and upcycling of poly(ethylene terephthalate) (PET) has been considered one of the most important subjects. In this study, the depolymerization of PET with n-hexylamine, n-octylamine, and 3-amino-1-propanol has been explored in the presence of Cp*TiCl3 (Cp* = C5Me5). The reactions of PET with n-hexylamine and n-octylamine at 130 °C afforded the corresponding N,N′-di(n-alkyl) terephthalamides in high yields (>90%), and Cp*TiCl3 plays a role as the catalyst to facilitate the conversion in exclusive selectivity. The reaction of PET with 3-amino-1-propanol proceeded at 100 °C even in the absence of the Ti catalyst, affording N,N′-bis(3-hydroxy) terephthalamides in high yields. A unique contrast has been demonstrated between the depolymerization of PET by transesterification with alcohol and by aminolysis; the depolymerizations with these amines proceeded without the aid of a catalyst.

Chemical upcycling of polybutadiene into size controlled α,ω-dienes and diesters via sequential hydrogenation and cross-metathesis.

Plastic waste conversion into valuable chemicals is a promising alternative to landfill or incineration. In particular, the chemical upcycling of polybutadiene rubber (PBR) could provide a renewable route towards highly desirable α,ω-dienes with varying chain lengths, which can find ample industrial application. While previous research has shown that the treatment of polybutadiene with a consecutive hydrogenation and ethenolysis reaction can afford long-chain α,ω-dienes, achieving precise control over the product chain length remains an important bottleneck. In this work, it was discovered that undesired isomerization during the initial hydrogenation step compromises the product selectivity after ethenolysis, leading to a distribution of α,ω-dienes that covers the full range of chain lengths from C6 to C22. Based on this insight, we show that the suppression of isomerization affords a well-defined product distribution predominantly consisting of C4n+2-dienes (with n = 1-5). With tight control over both the hydrogenation degree and isomerization in the studied PBD samples, we demonstrate that rational modifications to the reaction conditions can steer the selectivity towards the desired chain lengths of the α,ω-diene products. In addition, these insights were expanded to cross-metathesis (CM), giving access to a diverse range of high-value bifunctional products.

Comparative analysis of thermal and catalytic pyrolysis methods for converting waste plastic into fuel oil

Comparative analysis of thermal and catalytic pyrolysis methods for converting waste plastic into fuel oil

Accurately Tuning the Pore size and Acidity of Mesoporous Zeolites for Enhancing Catalytic Hydrocracking of Polypropylene

Catalytic hydrocracking of plastics is one of the appealing strategies for converting waste plastics into high-value chemicals and fuels, featuring in environmentally friendly and economical. Zeolite is considered to be...

Recent Progress for Designing of Catalysts for Photothermal Conversion of Plastic Wastes

AbstractIn the context of the global struggle against plastics, catalytic upgrading and recycling of plastics has been the subject of considerable attention as a powerful strategy for achieving both environmental remediation and value‐added chemical production. Compared with conventional recycling methods, the emerging photothermal catalysis methodology integrates photochemical and thermal catalytic processes, which outstands with features of high conversion efficiency and mild reaction conditions. Herein, a comprehensive review for the recent research progress of photothermal conversion of plastic waste is presented. First, the types of photothermal catalysts for plastic upcycling are classified into three categories, metallic materials, semiconductor materials, and carbon‐based materials, based on the photothermal conversion mechanism. Their potential mechanisms as powerful photothermal converters and future directions in photothermal conversion of plastics are highlighted. Furthermore, the logical structural design of photothermal catalytic materials are summarized to enhance photothermal performance in plastic conversion. Finally, future opportunities and challenges in this promising but nascent field are discussed, and future research directions for photothermal conversion of plastics are presented.

Mineralizing Biofilm towards Sustainable Conversion of Plastic Wastes to Hydrogen

AbstractThe integration of inorganic materials with biological machinery to convert plastics into fuels offers a promising strategy to alleviate environmental pollution and energy crisis. Herein, we develop a type of hybrid living material via biomineralization of CdS onto Shewanella oneidensis‐based biofilm, which is capable of sustainable hydrogen production from poly(lactic acid) (PLA) wastes under daylight. We reveal that the formed biofilm microstructure provides an independent anaerobic microenvironment that simultaneously supports cellular viability, maintains hydrogenase activity, and preserves the functional stability of CdS, giving rise to the efficient plastic‐to‐hydrogen conversion efficiency as high as 3751 μmol H2 g‐1 PLA. Besides, by genetically engineering transmembrane pili conduit and incorporating conductive nanomaterials to strengthen the electron transfer across cellular interface and biofilm matrices, we show that the conversion efficiency is further enhanced to 5862 μmol H2 g‐1 PLA. Significantly, we exhibit that a long‐term sustainable plastic‐to‐hydrogen conversion of 63 d could be achieved by periodically replenishing PLA wastes. Overall, by the synergistic integration of biotic‐abiotic characteristics the developed biofilm‐based biomineralized hybrid living material is anticipated to provide a new platform toward the efficient conversion of plastic wastes into valuable fuels, and bridge the gap between environmental contamination and green energy production.

Mineralizing Biofilm towards Sustainable Conversion of Plastic Wastes to Hydrogen.

The integration of inorganic materials with biological machinery to convert plastics into fuels offers a promising strategy to alleviate environmental pollution and energy crisis. Herein, we develop a type of hybrid living material via biomineralization of CdS onto Shewanella oneidensis-based biofilm, which is capable of sustainable hydrogen production from poly(lactic acid) (PLA) wastes under daylight. We reveal that the formed biofilm microstructure provides an independent anaerobic microenvironment that simultaneously supports cellular viability, maintains hydrogenase activity, and preserves the functional stability of CdS, giving rise to the efficient plastic-to-hydrogen conversion efficiency as high as 3751 μmol H2 g-1 PLA. Besides, by genetically engineering transmembrane pili conduit and incorporating conductive nanomaterials to strengthen the electron transfer across cellular interface and biofilm matrices, we show that the conversion efficiency is further enhanced to 5862 μmol H2 g-1 PLA. Significantly, we exhibit that a long-term sustainable plastic-to-hydrogen conversion of 63 d could be achieved by periodically replenishing PLA wastes. Overall, by the synergistic integration of biotic-abiotic characteristics the developed biofilm-based biomineralized hybrid living material is anticipated to provide a new platform toward the efficient conversion of plastic wastes into valuable fuels, and bridge the gap between environmental contamination and green energy production.

Current Advances in the Photoconversion of Plastics: the Catalysts and Reaction Pathways.

Plastic waste has caused severe global environmental pollution and health issues due to the high production rate and lack of proper disposal technology. Traditional methods to deal with plastic waste, such as incineration and landfilling, are deemed unsustainable and energy-intensive. A promising alternative is the photocatalytic conversion of plastic waste, using sunlight as a sustainable and carbon-neutral energy source to break down plastic waste under ambient pressure and low temperatures. This review aims to provide a comprehensive summary of recent advancements in plastic photoconversion, with an emphasis on the catalysts and reaction pathways. The mechanisms and reaction routes are first reviewed, followed by a detailed discussion of strategies to design catalysts for improved performance in photoconversion. Then, examples of photothermal degradation processes are presented. Finally, current strategies, challenges, and possible future directions of plastic photoconversion are summarized and discussed.

Photocatalytic Upcycling of Plastic Waste into Syngas by ZnS/Ga2O3 Z-Scheme Heterojunction.

The photocatalytic conversion of plastic waste into value-added products using solar energy presents a promising approach for promoting environmental sustainability. Nonetheless, the emission of CO2 during the conventional photocatalytic degradation process remains a major hurdle that impedes its further development. In this study, we propose an efficient photocatalytic conversion of polyethylene plastic into syngas (CO+H2 mixtures) by using a ZnS/Ga2O3 Z-scheme heterojunction photocatalyst. It is found that the strong redox capability of photogenerated holes and electrons in the Z-scheme heterojunction photocatalyst can promote the oxidative depolymerization of PE plastic, concurrently enabling the efficient reduction of the intermediate product CO2 into syngas. Furthermore, this system also demonstrates applicability in the conversion and upcycling of other polyolefin plastics including polypropylene and polyvinyl chloride. Our findings highlight the potential of polyolefin plastics photoreforming for the production of syngas under environmentally benign conditions.

Advancing Sustainability through Energy Innovation and Climate Action: Insights from ETUT

This study explores the potential of sustainable energy solutions to address global energy challenges and mitigate climate change. Oguz Han Engineering and Technology University (ETUT) serves as a case study, displaying its innovative approaches to energy efficiency, waste management, and renewable energy production. The university's implementation of energy-saving devices, smart building automation systems, and LED lighting demonstrates a commitment to reducing carbon emissions and promoting sustainable practices. Additionally, the study investigates the conversion of plastic waste into liquid fuel and the production of bioethanol from cotton stalks as potential solutions for waste management and renewable energy generation. Further, the research explores the deposition of thin film bismuth vanadium tetraoxide for hydrogen production, highlighting its potential as a clean energy source. Overall, this study emphasizes the importance of sustainable energy solutions and the role of academic institutions in driving innovation and promoting a greener future.

Catalytic conversion of plastic waste into diesel fuel through pyrolysis and hydroprocessing

This study evaluates the potential of hydro-processed plastic pyrolysis oil (HPO) as a sustainable alternative fuel derived from mixed plastic waste. The physicochemical properties of diesel, mixed plastic pyrolysis oil (MPPO), and HPO were thoroughly analyzed according to IS standards, enabling a direct comparison and alignment of HPO characteristics with EN590 diesel fuel standards. Gas chromatography-mass spectrometry (GC-MS) analysis identified key fuel components—n-alkanes, alkenes, benzene, and naphthalene with HPO showing 98 % compositional similarity to commercial diesel. The HPO blend with various percentage of pure diesel ratio is (30:70, 60:40 and 90:10). The hydroprocessing technique effectively reduced the alkene content of MPPO, enhancing the purity and quality of the resulting HPO. This refinement was crucial in ensuring that the oil met the necessary fuel standards. Engine performance evaluations further indicated that blending HPO with conventional diesel resulted in emissions with 95 % similarity to those of standard diesel fuel. This close match in emission profiles underscores the potential of HPO as a cleaner and more environmentally friendly fuel alternative. Additionally, the increased aromatic content in HPO, due to hydroprocessing, significantly improved combustion properties. This enhancement not only supports the feasibility of using HPO as a substitute for traditional diesel but also suggests that HPO may offer superior performance in specific applications. Overall, these findings highlight the potential of HPO as a sustainable fuel option, capable of addressing the environmental impacts associated with both plastic waste and fossil fuel consumption. The study demonstrates the environmental benefits of converting plastic waste into valuable fuel through pyrolysis and hydroprocessing, offering a promising strategy for sustainable plastic waste management and advancements in environmental sustainability and the fuel industry.

In situ formation of oxygen-deficient WO3-x nanosheets for enhanced photocatalytic activity in water splitting and plastic reforming

Photocatalytic pathways are essential for the sustainable production of chemicals and fuels, pivotal for achieving a pollution-free planet. Electron-hole recombination is a critical problem that has, so far, limited the efficiency of the photocatalytic materials. Here, oxygen-deficient WO3-x nanosheets were in situ grown in a polymeric carbon nitride (PCN) support during the thermal polycondensation of melamine. The introduction of defect in WO3-x, accompanied by spin polarization and the formed WO3-x/PCN heterostructure, greatly accelerated the charge separation and transfer. The synthesized WO3-x/PCN composite exhibited a tenfold increase in hydrogen generation activity than pure PCN under visible-light (420 ≤ λ ≤ 780 nm). The WO3-x/PCN also demonstrated consecutive 24 h and stable photocatalytic H2 production in the aqueous plastic-containing [poly(vinyl alcohol) (PVA), poly(ethylene terephthalate) (PET) and the PET bottle] solutions under visible light. The hydrogen production rates were determined to be 111.2, 50.5, and 7.8 μmol·h−1·g−1 in PVA, PET and PET bottle, respectively. In addition, the oxygen vacancies WO3 with their localized surface plasmon resonance effect, facilitated efficient utilization of NIR photon and the hydrogen evolution rate over WO3-x/PCN reached to 120 μmol h−1·g−1 under NIR light (700 ≤ λ ≤ 780 nm). This research not only advances the potential applications of WO3-x/PCN in sustainable energy production but also provides insights into environmental remediation through the conversion of plastic wastes.

The Potential Use of Plastic Waste as Sustainable Construction Material

Solid waste management is one of the major process which our country has to be given importance. One of the major threats in the solid waste is due to the Plastic Waste generation which are released to the open environment without any proper care. Since the plastic waste take more years to get degraded, the major issue arises is management of plastic waste among the total solid waste produced. They even cause environmental as well as health issues to the living being.The project elucidates about the use of LDPE waste as the construction material i.e., paving tile which is an innovative method for the conversion of plastic waste to a useful product. The pavement tiles showed best results of compressive strength and breaking load when tested. As a result, the so made pavement tile can be used either as pedestrian paving tile or can also be used as paving tile for residential driveways there by showing a compressive strength of 42 N/mm2 and a breaking load of 3 KN.

Rapid Surface Reconstruction of Amorphous‐Crystalline NiO for Industrial‐Scale Electrocatalytic PET Upcycling

The conversion of plastic waste into valuable chemicals through innovative and selective nano‐catalysts offers significant economic benefits and positive environmental impacts. However, our current understanding of catalyst design capable of achieving industrial‐grade current densities is limited. Herein, we develop a self‐supported amorphous‐crystalline NiO electrocatalyst for the electrocatalytic upcycling of polyethylene terephthalate (PET) into formate and hydrogen (H2) fuel. The catalyst achieves an industrial current density of over 1 A cm‐2 at 1.5 V vs. RHE, with an 80% Faradaic efficiency and a formate production rate of 7.16 mmol cm‐2 h‐1. In situ Raman spectroscopy, X‐ray absorption spectroscopy, and density functional theory calculations reveal that the rapid transformation of amorphous‐crystalline NiO into γ‐NiOOH at the amorphous‐crystalline interface provides a thermodynamic advantage for formate desorption, leading to the high activity required for industrial applications, which is difficult to achieve for fully crystalline NiO. A techno‐economic analysis indicates that recycling waste PET using this catalytic process could generate a profit of $501 per ton. This work presents a cost‐effective and highly efficient approach to promoting the sustainable utilization of waste PET.

Rapid Surface Reconstruction of Amorphous-Crystalline NiO for Industrial-Scale Electrocatalytic PET Upcycling.

The conversion of plastic waste into valuable chemicals through innovative and selective nano-catalysts offers significant economic benefits and positive environmental impacts. However, our current understanding of catalyst design capable of achieving industrial-grade current densities is limited. Herein, we develop a self-supported amorphous-crystalline NiO electrocatalyst for the electrocatalytic upcycling of polyethylene terephthalate (PET) into formate and hydrogen (H2) fuel. The catalyst achieves an industrial current density of over 1 A cm-2 at 1.5 V vs. RHE, with an 80% Faradaic efficiency and a formate production rate of 7.16 mmol cm-2 h-1. In situ Raman spectroscopy, X-ray absorption spectroscopy, and density functional theory calculations reveal that the rapid transformation of amorphous-crystalline NiO into γ-NiOOH at the amorphous-crystalline interface provides a thermodynamic advantage for formate desorption, leading to the high activity required for industrial applications, which is difficult to achieve for fully crystalline NiO. A techno-economic analysis indicates that recycling waste PET using this catalytic process could generate a profit of $501 per ton. This work presents a cost-effective and highly efficient approach to promoting the sustainable utilization of waste PET.

Nanocatalysts convert waste plastic bottles into value-added products

Nanocatalysts convert waste plastic bottles into value-added products

Efficient photoreforming of plastic waste using a high-entropy oxide catalyst

Simultaneous catalytic hydrogen (H2) production and plastic waste degradation under light, known as photoreforming, is a novel approach to green fuel production and efficient waste management. Here, we use a high-entropy oxide (HEO), a new family of catalysts with five or more principal cations in their structure, for plastic degradation and simultaneous H2 production. The HEO shows higher activity than that of P25 TiO2, a benchmark photocatalyst, for the degradation of polyethylene terephthalate (PET) plastics in water. Several valuable products are produced by photoreforming of PET bottles and microplastics including H2, terephthalate, ethylene glycol and formic acid. The high activity is attributed to the diverse existence of several cations in the HEO lattice, lattice defects, and appropriate charge carrier lifetime. These findings suggest that HEOs possess high potential as new catalysts for concurrent plastic waste conversion and clean H2 production.

Sustainable recovery of monomers from PET and PC waste via Thermocatalytic depolymerization for synthesis of polycarbonates and co-polycarbonates

The increasing global demand for sustainable plastics recycling methods has propelled the research and development of innovative depolymerization processes. The Thermocatalytic depolymerization (TCDP) of polyethylene terephthalate (PET) and polycarbonate (PC) has been performed at 200 ℃. Ethylene glycol (EG) is used as a reactant and as well a polymer bond-cleaving agent and Yttrium Oxide (Y2O3) is used as an effective catalyst. Y2O3 acted as a dual role during depolymerization reaction, which converts EG into cyclic ethylene oxide (CEO) and as well as to break the ester and carbonate bonds in the polymer structure of PET and PC respectively. The TCDP reaction conditions were optimized and the maximum quantity of Bis(2-hydroxyethyl) terephthalate (BHET) (80%) and (Bisphenol A (BPA)) (83%) has been recovered by TCDP reaction of PET and PC respectively. The polycarbonate and co-polycarbonate (Co-PC) were synthesized using recovered BPA and BHET with triphosgene via polycondensation reaction. The structure of monomers and polymers was confirmed by existing analytical (FTIR, NMR, XRD and GPC) techniques. The thermal properties of PC and Co-PC were performed by TG analysis. The TGA results reveal that the degradation temperature (Td) of PC and Co-PC are observed at 420.5 and 442.8 °C respectively, which shows that the Td of Co-PC has been increased by 22 ℃ than PC. The TCDP process is an effective method to recover specific value-added products from waste plastics, which could be made into a new versatile material for different applications. This research finding will provide a new direction to convert plastic waste into useful chemicals, which could reduce waste plastic and their carbon footprint and contribute to a more sustainable future by reusing plastic materials and achieving a circular economy.

Producing aromatic‐rich oil through microwave‐assisted catalytic pyrolysis of low‐density polyethylene over Ni/Co/Cu‐doped Ga/ZSM‐5 catalysts

AbstractMicrowave (MW)‐assisted catalytic pyrolysis represents a promising method for transforming petroleum‐based plastic waste into valuable chemicals, offering a pathway towards more sustainable circular economy. In this study, catalytic pyrolysis of low‐density polyethylene (LDPE) was conducted under MW irradiation. The influence of various catalyst types (HZSM‐5, Ga/ZSM‐5, Ga/Ni/ZSM‐5, Ga/Co/ZSM‐5, and Ga/Cu/ZSM‐5) on product yield and distribution was examined. The results revealed that the Ga/ZSM‐5 catalyst yielded the maximum liquid oil, approximately 41%. Ga/Ni/ZSM‐5 performed excellently in the production of long‐chain olefins, constituting about 27% of the liquid fraction. However, Ga/Co/ZSM‐5 led to the production of heavy pyrolysis oil containing nearly 25% long‐chain paraffins, rendering it unsuitable for producing high‐value chemicals. Conversely, the Ga/Cu/ZSM‐5 catalyst yielded an aromatic‐rich pyrolysis oil, with benzene derivatives constituting approximately 90% of the liquid oil fraction, thus proving to be a suitable catalyst for the intended application. The liquid product distribution was compared with a petroleum assay by SimDist, and this suggested that utilizing the HZSM‐5 catalyst could yield an 86.4% naphtha fraction. The study also revealed that the Ga/Cu/ZSM‐5 catalyst generated the largest amounts of hydrogen and syngas, as determined by a MicroGC analysis of the gas products. This catalyst also exhibited the maximum coke deposition (1.35%) postreaction, which was attributed to its high aromatic hydrocarbon content in the pyrolysis oil and maximal hydrogen release. A comparison of fresh and spent catalyst properties was conducted to gain insights into catalyst activity and to correlate the effects of metal doping on product distribution. These findings underscore the potential of MW‐assisted catalytic pyrolysis, particularly with the Ga/Cu/ZSM‐5 catalyst, for the efficient conversion of plastic waste into valuable chemicals, thereby contributing to sustainable resource utilization and environmental conservation.

Optimizing process parameters and materials for the conversion of plastic waste into hydrogen

Abstract This study has investigated hydrogen production from waste plastics using pyrolysis, steam methane reforming, and water-gas-shift reactions modelled via Aspen Plus. After evaluating multiple alternatives, polypropylene (PP) was selected as the feedstock. The research has been focused on how reformer temperature, steam-to-fuel ratio (S/F), reformer pressure, and pyrolysis temperature impact syngas composition, heating values, syngas (H2/CO) ratios, and yields of hydrogen (H2), methane (CH4), and carbon dioxide (CO2). Key findings have indicated that raising reformer temperatures to around 1000°C maximizes hydrogen production in syngas, reaching peak levels of 2360 Nm3/Ton and 2525 Nm3/Ton for reformer temperature and steam-to-fuel ratio (S/F) ratios, respectively, via processes like steam methane reforming and the water-gas-shift reaction. Moreover, other parameters like steam-to-fuel (S/F) ratio and reformer pressure have produced the highest amount of hydrogen at 0.25 and 1 atm, respectively. Optimizing reformer temperature and steam-to-fuel ratio (S/F) have been selected as key in hydrogen production, with peak lower heating values (LHV) of 1.15 MJ/kg for temperature and 1.035 MJ/kg for S/F ratios, highlighting the importance of balancing these parameters for efficiency. Additionally, syngas' hydrogen (H2) composition increased with pyrolysis temperature, peaking at 8.5% at 700°C. Finally, this research has provided valuable insights into optimizing process parameters for sustainable hydrogen production. Moreover, the simulation process has provided cost-effective adjustments and informed decision-making for sustainable and scalable technologies, benefiting researchers, investors, engineers, and policymakers involved in innovative hydrogen generation.