Low-temperature upcycling of polyolefins into liquid alkanes via tandem cracking-alkylation

Zhang, Wei; Kim, Sung M.; Wahl, Lennart; Khare, Rachit; Hale, Lillian V.; Hu, Jianzhi; Camaioni, Donald M.; Gutiérrez, Oliver Y.; Liu, Yue; Lercher, Johannes A.

doi:10.1126/science.ade7485

Cited by 106 publications

(68 citation statements)

References 47 publications

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“…Recently, the chemical upcycling of polymers to commercially relevant feedstocks has gained attention for plastic waste valorization. − Photooxidative degradation of PS is a promising method because it uses mild visible light irradiation and an inexpensive oxidant, molecular O 2 . During this degradation pathway, carbon-centered radicals on the PS backbone are generated via hydrogen atom transfer (HAT).…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Insights Enable Divergent Product Selectivity in Catalyst-Controlled Photooxidative Degradation of Polystyrene

Stache

2023

ACS Catal.

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Polystyrene upcycling to valuable commodity feedstocks is essential for reducing plastic waste. Photooxidative degradation has emerged as a method for converting polystyrene to oxidized aromatic compounds. Investigating the mechanism of photooxidative degradation is essential for understanding the pathways to generating different small molecules. Here, we leveraged the reactivity differences between chlorine and bromine radicals to study the degradation mechanism of polystyrene. While degradation with chlorine radical yields primarily benzoic acid (50 mol %), bromine radical shows an increased preference for acetophenone (4 mol % for both products). After conducting several mechanistic studies, we discovered that activation of 3°C− H bonds is necessary to form acetophenone. However, for acetophenone production, a second hydrogen atom transfer from H−Br enables the reformation of a methyl group on the polymer chain end. Lastly, with the mechanistic insights in hand, we added exogenous bromine sources to increase the concentration of HBr and improved the acetophenone yield, becoming the major degradation product. We envision that our insights into the polystyrene degradation mechanism will further enable divergent product selectivity.

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Section: Introductionmentioning

confidence: 99%

Mechanistic Insights Enable Divergent Product Selectivity in Catalyst-Controlled Photooxidative Degradation of Polystyrene

Stache

2023

ACS Catal.

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“…Product control is thus exceptionally challenging. Recently, chemical reactions that use iridium- ( 13 ) and platinum-based catalysts ( 14 ) and ionic liquids ( 15 ) generated fuels and improved selectivity toward aryl moieties in the upcycling of PE. On a laboratory scale, PE can also be converted to propylene by dehydrogenation and tandem isomerizing ethenolysis ( 16 , 17 ).…”

mentioning

confidence: 99%

Chemical upcycling of polyethylene, polypropylene, and mixtures to high-value surfactants

Xu,

Munyaneza,

Zhang

et al. 2023

Science

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Conversion of plastic wastes to fatty acids is an attractive means to supplement the sourcing of these high-value, high-volume chemicals. We report a method for transforming polyethylene (PE) and polypropylene (PP) at ~80% conversion to fatty acids with number-average molar masses of up to ~700 and 670 daltons, respectively. The process is applicable to municipal PE and PP wastes and their mixtures. Temperature-gradient thermolysis is the key to controllably degrading PE and PP into waxes and inhibiting the production of small molecules. The waxes are upcycled to fatty acids by oxidation over manganese stearate and subsequent processing. PP ꞵ-scission produces more olefin wax and yields higher acid-number fatty acids than does PE ꞵ-scission. We further convert the fatty acids to high-value, large–market-volume surfactants. Industrial-scale technoeconomic analysis suggests economic viability without the need for subsidies.

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“…This system achieved quantitative polyethylene conversion to isoalkanes within 6 h at 70 °C, and the smallmolecule outputs phase-separated from the IL reaction milieu to enable facile recovery of the product. 136 It is worth noting that several experimental parameters interact with IL design to determine the effectiveness of ILmediated deconstruction. For example, temperature plays a controlling role in overcoming the activation energy to enable catalytic reactions.…”

Section: ■ Il Physicochemical Properties Impact Deconstruction Perfor...mentioning

confidence: 99%

“…Similarly, synergistic effects between the cation and anion of a [Bmim][FeCl 4 ] IL result in higher deconstruction catalytic activities at lower temperatures for PET versus either the analogous metal-free [Bmim][Cl] IL or the FeCl 3 salt alone . The incorporation of metallic atoms into ILs also has shown promise for polyolefin deconstruction . For instance, a Lewis acid chloroaluminate-based IL facilitated the upcycling of polyethylene to liquid alkanes by enabling simultaneous cracking and alkylation.…”

Section: Il Physicochemical Properties Impact Deconstruction Performancementioning

confidence: 99%

Ionic-Liquid-Mediated Deconstruction of Polymers for Advanced Recycling and Upcycling

Christoff‐Tempesta

Epps

2023

ACS Macro Lett.

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Ionic liquids (ILs) are a promising medium to assist in the advanced (chemical and biological) recycling of polymers, owing to their tunable catalytic activity, tailorable chemical functionality, low vapor pressures, and thermal stability. These unique physicochemical properties, combined with ILs' capacity to solubilize plastics waste and biopolymers, offer routes to deconstruct polymers at reduced temperatures (and lower energy inputs) versus conventional bulk and solvent-based methods, while also minimizing unwanted side reactions. In this Viewpoint, we discuss the use of ILs as catalysts and mediators in advanced recycling, with an emphasis on chemical recycling, by examining the interplay between IL chemistry and deconstruction thermodynamics, deconstruction kinetics, IL recovery, and product recovery. We also consider several potential environmental benefits and concerns associated with employing ILs for advanced recycling over bulk-or solvent-mediated deconstruction techniques, such as reduced chemical escape by volatilization, decreased energy demands, toxicity, and environmental persistence. By analyzing IL-mediated polymer deconstruction across a breadth of macromolecular systems, we identify recent innovations, current challenges, and future opportunities in IL application toward circular polymer economies.

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Low-temperature upcycling of polyolefins into liquid alkanes via tandem cracking-alkylation

Cited by 106 publications

References 47 publications

Mechanistic Insights Enable Divergent Product Selectivity in Catalyst-Controlled Photooxidative Degradation of Polystyrene

Mechanistic Insights Enable Divergent Product Selectivity in Catalyst-Controlled Photooxidative Degradation of Polystyrene

Chemical upcycling of polyethylene, polypropylene, and mixtures to high-value surfactants

Ionic-Liquid-Mediated Deconstruction of Polymers for Advanced Recycling and Upcycling

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