通过酸解对聚氨酯进行化学分离 - 将酸解与水解相结合,实现芳香胺的价值化

IF 9.2 1区 化学 Q1 CHEMISTRY, MULTIDISCIPLINARY
Green Chemistry Pub Date : 2024-07-15 DOI:10.1039/d4gc00819g
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引用次数: 0

摘要

由于 2022 年全球聚合物产量将超过 4 亿吨,因此必须提高回收率,以防止主要通过填埋和焚烧流程进行报废处理。随着人们对聚氨酯(PU)的依赖程度越来越高,2022 年全球聚氨酯产量将近 2600 万吨。由于聚氨酯主要用作热固性材料,其广泛的交联网络使得热塑性材料的熔化和重塑工艺变得不相容。因此,大部分回收的聚氨酯都是通过机械粉碎和胶粘工艺进行处理,或通过乙二醇和酸解工艺进行化学回收,以回收多元醇,所有这些都提供了一种性能不同于母体材料的二次材料。在这里,我们展示了成熟的酸解工艺既可用于聚氨酯解聚,也可用于分离多元醇和二苯胺加合物,重点是分析聚氨酯硬段中产生的二苯胺成分并对其进行估值。通过评估软质聚氨酯泡沫在纯净条件下与琥珀酸、己二酸或邻苯二甲酸发生酸解反应的结果,发现琥珀酸可形成相应的甲苯二胺琥珀酰亚胺,并很容易从多元醇中分离出来。而甲苯二胺又可以通过钌催化的氢化或简单的水解进行转化。最终,对软质聚氨酯泡沫进行酸解/水解,可获得多元醇和二苯胺,总回收率为 83%。商用再粘合软质泡沫也达到了类似的回收率。由于目前的聚氨酯回收方法只针对通常以低质量获得的多元醇部分,这一进展表明,目前工业应用的酸解方法可以改变,从而可以从软质聚氨酯泡沫中获得二元胺和多元醇。初步结果表明,该工艺适用于硬质聚氨酯泡沫,这种聚氨酯部分因其分子复杂而难以回收利用。最后,还提出了一种机理途径来解释观察到的产品分布。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

Chemical separation of polyurethane via acidolysis – combining acidolysis with hydrolysis for valorisation of aromatic amines†

Chemical separation of polyurethane via acidolysis – combining acidolysis with hydrolysis for valorisation of aromatic amines†

Chemical separation of polyurethane via acidolysis – combining acidolysis with hydrolysis for valorisation of aromatic amines†

As the global production of polymers exceeded 400 million tons in 2022, it is imperative that recycling rates are increased to prevent the predominant end-of-life handling through landfilling and incineration processes. With an increasing reliance on polyurethane (PU), the 2022 global production of PU reached almost 26 million tons. As PU is mainly utilised as a thermoset material, the extensive cross-linked networks render melting and remolding processes known from thermoplastic materials incompatible. As such, the majority of PU that is recycled is processed through mechanical shredding and gluing processes or chemical recycling via glycolysis and acidolysis processes for polyol recovery, all providing a secondary material with properties different from the parent material. Here, we show that the well-established acidolysis process can be used to both depolymerise PU and separate the polyol and dianiline adducts with a specific focus on analysing and valorising the dianiline component arising from the hard segment of PU. By evaluation of the reaction outcome from acidolysis of flexible PU foam with succinic acid, adipic acid or phthalic acid under neat conditions, succinic acid was found to form the corresponding succinimide of toluene diamines that is readily separable from the polyol. The toluene diamine could in turn be reformed through ruthenium-catalysed hydrogenation or simple hydrolysis. Ultimately, the combined acidolysis/hydrolysis of a flexible PU foam yields the polyol and dianiline in a combined 83 wt% recovery. A similar recovery rate was achieved for a commercial rebonded flexible foam. As current PU recycling methods only target the polyol fraction often obtained in a low quality, this advancement shows that current industrially applied acidolysis could be altered so that both the diamines and polyol can be obtained from flexible PU foam. Preliminary results show that the process is applicable to rigid PU foams, a PU fraction that is difficult to recycle due to its molecular complexity. Finally, a mechanistic pathway is suggested to account for the observed product distributions.

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来源期刊
Green Chemistry
Green Chemistry 化学-化学综合
CiteScore
16.10
自引率
7.10%
发文量
677
审稿时长
1.4 months
期刊介绍: Green Chemistry is a journal that provides a unique forum for the publication of innovative research on the development of alternative green and sustainable technologies. The scope of Green Chemistry is based on the definition proposed by Anastas and Warner (Green Chemistry: Theory and Practice, P T Anastas and J C Warner, Oxford University Press, Oxford, 1998), which defines green chemistry as the utilisation of a set of principles that reduces or eliminates the use or generation of hazardous substances in the design, manufacture and application of chemical products. Green Chemistry aims to reduce the environmental impact of the chemical enterprise by developing a technology base that is inherently non-toxic to living things and the environment. The journal welcomes submissions on all aspects of research relating to this endeavor and publishes original and significant cutting-edge research that is likely to be of wide general appeal. For a work to be published, it must present a significant advance in green chemistry, including a comparison with existing methods and a demonstration of advantages over those methods.
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