Potential Chemicals from Plastic Wastes
Plastic is referred to as a “material of every application”. From the packaging and automotive industries to the medical apparatus and computer electronics sectors, plastic materials are fulfilling demands efficiently. These plastics usually end up in landfills and incinerators, creating plastic waste pollution. According to the Environmental Protection Agency (EPA), in 2015, 9.1% of the plastic materials generated in the U.S. municipal solid waste stream was recycled, 15.5% was combusted for energy, and 75.4% was sent to landfills.
2. Production of Chemicals from Plastic Wastes
|Polymer||Low-Temperature Products||High-Temperature Products|
|Polyethylene (PE)||Waxes, paraffin oil,
|Gases and light oils|
|Polypropylene (PP)||Vaseline, olefins||Gases and light oils|
|Polystyrene (PS)||Styrene and its oligomers||Styrene and its oligomers|
|Polymethyl methacrylate (PMMA)||Methylmethacrylate
|Low methyl methacrylate, more decomposition products|
|Polyethylene terephthalate (PET)||Benzoic acid (BA),
|Polyamide 6 (PA6)||ε-caprolactum (CPL)|
2.1. Polyethylene (PE) and Polypropylene (PP)
|S. No.||Plastics||Method||Conditions||Product Yields||Key Findings||Source|
|1.||PE||Noncatalytic pyrolysis||T = 602 °C||Paraffins 45%; Olefins 32%; Naphthalenes 17%;Aromatics 6%;||A whole spectrum of HCs, including paraffins, olefins, naphthalenes, and aromatics.|||
|PP||T = 602 °C||Paraffins 27%; Olefins 36%; Aromatics 11%;|
|PS||T = 477 °C||Styrene 63%|
|2.||HDPE||Thermal-catalytic two-step pyrolysis||T = 500 °C||Light olefin 59%||Higher efficiency of the two-step reaction system compared to the in situ catalytic pyrolysis (single-step) for production of 10 wt.% ethylene, 32 wt.% propylene, and 17 wt.% butenes.|||
|3.||PP and PE||Fluidized bed reactor||T =
|BTX 32–53%||Higher feed rates and gaseous fluidizing medium have a positive effect on liquid oil production.|||
|4.||PE||Mini-autoclave reactor (unstirred)||T = 280 °C,
t = 24 h, Pt/Al2O3
|Liquid product 80%||Tandem catalytic conversion produces a high yield of low-molecular-weight liquid/wax products.|||
|5.||PS||Fluidized bed reactor||T = 520 °C||Styrene 83%||Complete conversion of PS to styrene oil was reported, with only traces of aliphatic compounds|||
|6.||PS + organic compounds||Autoclave reactor||T = 400 °C,
t = 1 h
Residue < 4%
|Maximum styrene yield in the liquid was obtained with naphthalene as an organic compound with PS|||
|7.||PS||Flow reactor||T = 350 °C,
t = 3 h, Fe2O3
(in liquid oil)
|Barium oxide powder was found to be most effective catallyst for chemical recyling of PS waste|||
|T = 350 °C,
t = 3 h, BaO
(in liquid oil)
|T = 350 °C,
t = 3 h, HSM5
(in liquid oil)
|8.||PS||Fixed-bed reactor||T = 510 °C thermal||Liquid 91.8%;
|Other aromatic compounds can behave like a chain transfer agent and reduce the Tg of product polymer.|||
|T = 510 °C BaO (cat.)||Liquid 91.2%;
|T = 510 °C FCC cat.||Liquid 90.7%; Residue 7.1%|
|9.||PS||Two-stage auger and fluidized bed reactor||T = 780 °C||BTEX 26.3%||Product yields depend on the reaction temperatures and fluidizing mediums used.|||
|10.||PET||Glycolysis||T = 190 °C; atm pressure||BHET 100% conversion,
|Lewis acidic ionic liquids [Bmim]ZnCl3 catalyst was found to be effective.|||
|Hydrolysis||T = 200–250 °C; P = 1.4–2 MPa||TPA, EG|||
|Methanolysis||T = 200 °C||DMT 64%;
|The product yields depend on the solubility of PET.|||
|Aminolysis||T = 70–110 °C||Diamides of TPA 66–89%||The bifunctional 1,5,7-triazabicyclo [4.4.0]dec-5-ene activates the carbonyl group and catalyzes the reaction.|||
|Pyrolysis||T = 450–600 °C
ZSM-5 zeolite and NiCl2 used as catalyst
|Aromatic hydroxyl groups increased by 22%||ZSM-5 facilitated the decomposition of carboxyl, aliphatic groups, and ether bonds in the primary products produced from the PET pyrolysis.|||
|Pyrolysis||T = 400–700 °C||Phenyl carboxylic acid 44–79%||Pd loaded on activated carbon used as a catalyst and produced more environmentally friendly products|||
|11.||PET||Py-GCMS, EGA-MS, and TGA||T = 600 °C||4(vinyl oxy carbonyl) BA 27%;
|Wide range of liquid products obtained by different pyrolysis mechanisms.|||
|12.||PU||Glycolysis||T = 200–210 °C;
t = 2 h
|Acetone-soluble products 80.8%;
Amines in total acetone soluble products 58.3 mgKOH/g
|Polyol products produced from the process and used as initiators to produce oxy-alkylated polyols.|||
|13.||PA 6 and PA66||Aminolysis||T = 100 °C;
P = 3.5 MPa;
t = 5.6 h;
Raney® Co 2724
|ACN = 2; HMD = 32%; CPL = 46.2%; Other components = 13.6%||Raney® Co provided a better catalytic activity along with long catalyst life|||
|T = 100 °C;
P = 3.5 MPa;
t = 5.6 h;
Raney® Ni 2400
|ACN = 19.6; HMD = 15%; CPL = 46.5%; Other components = 14.7%|
|14.||PA66||Microwave irradiation||T = 200 °C;
t = 0.16 h; HCl:PA66 =
|AA 90%; HMDA 86%; with 100% purity||The rate of PA hydrolysis depended on the PA type and HCl/amide molar ratio. With microwave treatment, high-purity and high-quality products were formed.|||
2.2. Polystyrene (PS)
2.3. Polyethylene Terephthalate (PET)
2.4. Polyurethane (PU)
2.5. Polyamides (PA)
The entry is from 10.3390/molecules26113175
- Plastic Market Size. Share & Trends Analysis Report by Product (PE, PP, PU, PVC, PET, Polystyrene, ABS, PBT, PPO, Epoxy Polymers, LCP, PC, Polyamide), by Application, by Region, and Segment Forecast, 2020–2027. Available online: (accessed on 23 December 2020).
- Adyel, T.M. Accumulation of plastic waste during COVID-19. Science 2020, 369, 1314–1315.
- Leblanc, R. Plastic Recycling Facts and Figures. Available online: (accessed on 21 January 2021).
- Hunertmark, T.; Mayer, M.; McNally, C.; Simons, T.J.; Witte, C. How Plastics Waste Recycling Could Transform the Chemical Industry. Available online: (accessed on 16 November 2020).
- Garforth, A.A.; Ali, S.; Martinez, J.H.; Akah, A. Feedstock recycling of polymer wastes. Curr. Opin. Solid State Mater. Sci. 2004, 8, 419–425.
- Dufaud, V.; Basset, J.M. Catalytic hydrogenolysis at low temperature and pressure of polyethylene and polypropylene to diesels or lower alkanes by a zirconium hydride supported on silica alumina: A step toward polyolefin degradation by the microscope reverse of Ziegler−Natta polymerization. Angew. Chem. Int. Ed. 1998, 37, 806–810.
- Hibbitts, D.D.; Flaherty, D.W.; Iglesia, E. Effects of chain length on the mechanism and rates of metal-catalyzed hydrogenolysis of n-alkanes. J. Phys. Chem. C 2016, 120, 8125–8138.
- Flaherty, D.W.; Uzun, A.; Iglesia, E. Catalytic ring opening of cycloalkanes on Ir clusters: Alkyl substitution effects on the structure and stability of C−C bond cleavage transition states. J. Phys. Chem. C 2015, 119, 2597–2613.
- Flaherty, D.W.; Hibbitts, D.D.; Iglesia, E. Metal-catalyzed C−C bond cleavage in alkanes: Effects of methyl substitution on transition-state structures and stability. J. Am. Chem. Soc. 2014, 136, 9664–9676.
- Escola, J.M.; Aguado, J.; Serrano, D.P.; Briones, L. Hydroreforming over Ni/H-beta of the thermal cracking products of LDPE, HDPE and PP for fuel production. J. Mater. Cycles Waste Manag. 2012, 14, 286–293.
- Marcilla, A.; Beltrán, M.I.; Navarro, R. Evolution of products generated during the dynamic pyrolysis of LDPE and HDPE over HZSM5. Energy Fuels 2008, 22, 2917–2924.
- Bai, B.; Jin, H.; Fan, C.; Cao, C.; Wei, W.; Cao, W. Experimental investigation on liquefaction of plastic waste to oil in supercritical water. Waste Manag. 2019, 89, 247–253.
- Passos, J.S.; Glasius, M.; Biller, P. Screening of common synthetic polymers for depolymerization by subcritical hydrothermal liquefaction. Process. Saf. Environ. Prot. 2020, 139, 371–379.
- Murata, K.; Hirano, Y.; Sakata, Y.; Azhar Uddin, M. Basic study on a continuous flow reactor for thermal degradation of polymers. J. Anal. Appl. Pyrolysis 2002, 65, 71–90.
- McCaffrey, W.C.; Kamal, M.R.; Cooper, D.G. Thermolysis of polyethylene. Polym. Degrad. Stab. 1995, 47, 133–139.
- Demirbas, A. Recovery of chemicals and gasoline-range fuels from plastic wastes via pyrolysis. Energy Sources 2005, 27, 1313–1319.
- Artetxe, M.; Lopez, G.; Amutio, M.; Elordi, G.; Bilbao, J.; Olazar, M. Cracking of high-density polyethylene pyrolysis waxes on HZSM-5 catalysts of different acidity. Ind. Eng. Chem. Res. 2013, 52, 10637–10645.
- Jung, S.H.; Cho, M.H.; Kang, B.S.; Kim, J.S. Pyrolysis of a fraction of waste polypropylene and polyethylene for recovery of BTX aromatics using a fluidized bed reactor. Fuel Process. Technol. 2010, 91, 277–284.
- Zhang, F.; Zeng, M.; Yappert, R.D.; Sun, J.; Lee, Y.H.; LaPointe, A.M.; Peters, B.; Abu-Omar, M.M.; Scott, S.L. Polyethylene upcycling to long-chain alkylaromatics by tandem hydrogenolysis/aromatization. Science 2020, 370, 437–441.
- Ward, P.G.; Goff, M.; Donner, M.; Kaminsky, W.; O’Connor, K.E. A two-step chemo-biotechnological conversion of polystyrene to a biodegradable thermoplastic. Environ. Sci. Technol. 2006, 40, 2433–2437.
- Karaduman, A. Pyrolysis of polystyrene plastic wastes with some organic compounds for enhancing styrene yield. Energy Sources 2002, 24, 667–674.
- Zhang, Z.; Hirose, T.; Nishio, S.; Morioka, Y.; Azuma, N.; Ueno, A. Chemical recycling of waste polystyrene into styrene over solid acids and bases. Ind. Eng. Chem. Res. 1995, 34, 4514–4519.
- Achilias, D.S.; Kanellopoulou, I.; Megalokonomous, P.; Antonakou, E.; Lappas, A.A. Chemical recycling of polystyrene by pyrolysis: Potential use of the liquid product for the reproduction of polymer. Macromol. Mater. Eng. 2007, 292, 923–934.
- Park, K.B.; Jeong, Y.S.; Guzelciftci, B.; Kim, J.S. Two-stage pyrolysis of polystyrene: Pyrolysis oil as a source of fuels or benzene, toluene, ethylbenzene, and xylenes. Appl. Energy 2020, 259, 114240.
- Yue, Q.F.; Xiao, L.F.; Zhang, M.L.; Bai, X.F. The glycolysis of poly(ethylene terephthalate) waste: Lewis acidic ionic liquids as high efficient catalysts. Polymers 2013, 5, 1258–1271.
- Sinha, V.; Patel, M.R.; Patel, J.V. PET waste management by chemical recycling: A review. J. Polym. Envrion. 2010, 18, 8–25.
- Kao, C.Y.; Wan, B.Z.; Cheng, W.H. Kinetics of hydrolytic depolymerization of melt poly(ethyleneterephthalate). Ind. Eng. Chem. Res. 1998, 37, 1228–1234.
- Zahn, H.; Pfeifer, H. Aminolysis of polyethylene terephthalate. Polymer 1963, 4, 429–432.
- Jia, H.; Ben, H.; Luo, Y.; Wang, R. Catalytic fast pyrolysis of poly(ethylene terephthalate) (PET) with zeolite and nickel chloride. Polymers 2020, 12, 705.
- Dimitrov, N.; Kratofil Krehula, L.; Pticek Sirocic, A.; Hrnjak Murgic, Z. Analysis of recycled PET bottles products by pyrolysis-gas chromatography. Polym. Degread. Stab. 2013, 98, 972–979.
- Sheratte, M.B. Process for Converting the Decomposition Products of Polyurethane and Novel Compositions Thereby Obtained. U.S. Patent 4,110,266, 29 August 1978.
- Duch, M.W.; Allgeier, A.M. Deactivation of nitrile hydrogenation catalysts: New mechanistic insight from a nylon recycle process. Appl. Catal. A 2007, 318, 190–198.
- Cesarek, U.; Pahovnik, D.; Zagar, E. Chemical recycling of aliphatic polyamides by microwave-assisted hydrolysis for efficient monomer recovery. ACS Sustain. Chem. Eng. 2020, 8, 16274–16282.
- Rahimi, A.; Garcia, J.M. Chemical recycling of waste plastics for new materials production. Nat. Rev. Chem. 2017, 1, 46.
- De la Puente, G.; Sedran, U.A. Recycling polystyrene into fuels by means of FCC: Performance of various acidic catalysts. Appl. Catal. B Environ. 1998, 19, 305–311.
- Hussain, Z.; Khan, K.M.; Basheer, N.; Hussain, K. Co-liquefaction of Makarwal coal and waste polystyrene by microwave-metal interaction pyrolysis in copper coil reactor. J. Anal. Appl. Pyrolysis 2011, 90, 53–55.
- Bartolome, L.; Cho, B.; Do, H.; Imran, M.; Al-Masry, W. Recent Developments in the Chemical Recycling of PET; INTECH Open Access Publisher: Rijeka, Croatia, 2012.
- Global Polyethylene Terephthalate Production 2014–2020, Statista Research Department, 10 December 2015. Available online: (accessed on 23 December 2020).
- Polyurethane Market by Raw Material (MDI, TDI, Polyols), Products (Coatings, Adhesives, and Sealants, Flexible & Rigid Foams, Elastomers), End-User (Building & Construction, Automotive & Transportation, Bedding & Furniture)-Global Forecast to 2021. Available online: (accessed on 23 December 2020).
- Cit, I.; Smag, A.; Yumak, T.; Ucar, S.; Misirhogiu, Z.; Canel, M. Comparative pyrolysis of polyolefins (PP and LDPE) and PET. Polym. Bull. 2009, 64, 817–834.
- Loong, K.C. Simulation: Optimize the Production of Benzoic Acid by Using Benzene and Acetic Anhydride. Ph.D. Thesis, Universiti Tunku Abdul Rahman, Petaling Jaya, Malaysia, 2011.
- Benzoic Acid Market Size, Industry Analysis Report, Regional Outlook (U.S. Germany, UK, Italy, Russia, China, India, Japan, South Korea, Brazil, Mexico, Saudi Arabia, UAE South Africa), Application Development Price Trend, Competitive Market Share and Forecast, 2016–2023. Available online: (accessed on 21 January 2021).
- Rahman, W.M.N.W.A.; Wahab, A.F.A. Green pavement using recycled polyethylene terephthalate (PET) as partial fine aggregate replacement in modified asphalt. Procedia Eng. 2013, 53, 124–128.
- Taherkhani, H.; Arshadi, M.R. Investigating the mechanical properties of asphalt concrete containing waste polyethylene terephthalate. Road Mater. Pavement Des. 2019, 20, 381–398.
- Merkel, D.R.; Kuang, W.; Malhotra, D.; Petrossian, G.; Zhong, L.; Simmons, K.L.; Zhang, J.; Cosimbescu, L. Waste PET chemical processing to terephthalic amides and their effect on asphalt performance. ACS Sustain. Chem. Eng. 2020, 8, 5615–5625.
- Arnold, T.S. What in Your Asphalt. Fed. Highw. Adm. Res. Technol. 2017, 81, 2.
- Simon, D.; Borreguero, A.M.; de Lucas, A.; Rodriguez, J.F. Recycling of polyurethanes from laboratory to industry, a journey towards the sustainability. Waste Manag. 2018, 76, 147–171.
- Zia, K.M.; Bhatti, H.N.; Bhatti, I.A. Methods for polyurethane and polyurethane composites, recycling, and recovery: A review. React. Funct. Polym. 2007, 67, 675–692.
- Alavi Nikje, M.M.; Nikrah, M.; Mohammadi, F.H.A. Microwave-assisted polyurethane bond cleavage via hydrogenolysis process at atmospheric pressure. J. Cell Plast. 2008, 44, 367–380.
- Grancharov, G.; Mitova, V.; Stoitchov, S.; Antonya, T.; Gitsov, I.; Troev, K. Smart polymer recycling: Synthesis of novel rigid polyurethanes using phosphorous-containing oligomers formed by controlled degradation of microporous polyurethane elastomer. J. Appl. Polym. Sci. 2007, 105, 302–308.
- Herzog, B.; Kohan, M.I.; Mestemacher, S.A.; Pagilagan, R.U.; Redmond, K. Polyamides. Ullmann’s Encyclopedia of Industrial Chemistry; Barbara, E., Ed.; Wiley-VCH Verlag GmbH & Co. KGaA: Weinheim, Germany, 2013; pp. 697–732.
- Chen, J.; Liu, G.; Jin, L.; Ni, P.; Li, Z.; He, H.; Xu, Y.; Zhang, J.; Dong, J. Catalytic hydrolysis of waste Nylon 6 to produce caprolactam in subcritical waste. J. Anal. Appl. Pyrolysis 2010, 87, 50–55.
- Datta, J.; Błażek, K.; Włoch, M.; Bukowski, R. A new approach to chemical recycling of polyamide 6.6 and synthesis of polyurethanes with recovered intermediates. J. Polym. Environ. 2018, 26, 4415–4429.
- Kamimura, A.; Ikeda, K.; Suzuki, S.; Kato, K.; Akinari, Y.; Sugimoto, T.; Kashiwagi, K.; Kaiso, K.; Matsumoto, H.; Yoshimoto, M. Efficient conversion of polyamides to ω-hydroxyalkanoic acids: A new method for chemical recycling of waste plastics. ChemSusChem 2014, 7, 2473–2477.
- Matsumoto, H.; Akinari, Y.; Kaiso, K.; Kamimura, A. Efficient depolymerization and chemical conversion of Polyamide 66 to 1,6- hexanediol. J. Mater. Cycles Waste Manag. 2017, 19, 326–331.
- Samieadel, A.; Fini, E.H. Interplay between wax and polyphosphoric acid and its effect on bitumen thermochemical properties. Constr. Build. Mater. 2020, 243, 118194.
- Samieadel, A.; Hogsaa, B.; Fini, E.H. Examining the implications of wax-based additives on the sustainability of construction practices: Multiscale characterization of wax-doped aged asphalt binder. ACS Sustain. Chem. Eng. 2019, 7, 2943–2954.
- Jixing, L.; Shuyuan, W.; Xuan, L.; Xiang, Y. Study on the conversion technology of waste polyethylene plastic to polyethylene wax. Energy Sources 2003, 25, 77–82.
- Khan, H.U.; Sahai, M.; Kumar, S.; Kumar, A.; Thakre, G.D.; Kaul Nanoti, S.M.; Shukla, B.M.; Garg, M.O. Process for the conversion of low polymer wax to paraffin wax, microcrystalline wax, lube, and grease base stocks using organic peroxides or hydroperoxide and metal oxides. U.S. Patent 9,714,385, 25 July 2017.
- Celik, G.; Kennedy, R.M.; Hackler, R.A.; Ferrandon, M.; Tennakoon, A.; Patnaik, S.; LaPointe, A.M.; Ammal, S.C.; Heyden, A.; Perras, F.A.; et al. Upcycling single-use polyethylene into high-quality liquid products. ACS Cent. Sci. 2019, 5, 1795–1803.
- Miller, S.J. Conversion of waste plastic to lubricating base oil. Energy Fuels 2005, 19, 1580–1586.
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