Due to the high demand and the increasing production rate of plastic materials, vast amounts of wastes are generated every year. An important fraction of these wastes contain polystyrene (PS), which is seldom recycled, neither mechanically nor chemically. While several chemical recycling strategies have been developed, they are either very energy-demanding or produce chemicals that can hardly be employed in the synthesis of plastics (e.g., benzene and benzoic acid). Here, we report the upcycling of PS waste into aromatic polyacids, useful in polyester synthesis, such as polyethylene terephthalate (PET). To this end, a conventional Friedel–Crafts acylation was first investigated, to produce an acylated PS chain, using acetic anhydride and stoichiometric amounts of AlCl₃. As a catalytic alternative, the alkylation of PS was studied, using InCl₃ and isopropyl acetate. The acylated and alkylated PS samples were then oxidized to produce terephthalic (TA), isophthalic (IPTA), benzoic (BA), and trimesic (TMA) acid.

中文翻译：

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通过串联 Friedel-Crafts 和氧化反应将聚苯乙烯升级回收为芳香族多元酸


由于塑料材料的高需求和不断提高的生产率，每年都会产生大量的废物。这些废物中很大一部分含有聚苯乙烯 （PS），它很少被回收，无论是机械回收还是化学回收。虽然已经开发了几种化学回收策略，但它们要么非常耗能，要么产生几乎不能用于塑料合成的化学品（例如苯和苯甲酸）。在这里，我们报道了将 PS 废物升级回收为芳香族多元酸，可用于聚酯合成，例如聚对苯二甲酸乙二醇酯 （PET）。为此，首先研究了传统的 Friedel-Crafts 酰化反应，使用乙酸酐和化学计量量的 AlCl₃ 产生酰化 PS 链。作为催化替代物，使用 InCl₃ 和乙酸异丙酯研究了 PS 的烷基化反应。然后，酰化和烷基化 PS 样品被氧化以生成对苯二酸 （TA）、间苯二醇 （IPTA）、苯甲酸 （BA） 和三甲酸 （TMA）。