Catalytic Chemical Sorting of Intractably Mixed Plastics

全球迫切需要制定更好的塑料回收战略。据估计，迄今为止共生产了83亿吨塑料，但令人难以置信的是，在回收标志推出40多年后，生产的废塑料中只有不到10%被回收利用。剩下的要么倒进垃圾填埋场，燃烧产生二氧化碳和其他有害气体，或者最糟糕的是，被丢弃在环境中。塑料将继续在解决我们社会日益增长的需求方面发挥关键作用，从整体上根除它们并不是一个现实的解决方案。因此，一个关键的挑战是充分有效地处理我们产生的废塑料。我们迫切需要更好的塑料垃圾处理方案。塑料回收的一个关键挑战是处理复杂的塑料废物，例如多层薄膜和混合物，其中的成分不能通过机械手段轻易分离，或者其中的特定组合在主要的化学回收方法中造成问题。WRAP的《塑料流2025》报告估计，继瓶子之后，薄膜是第二大消费塑料包装形式（2017年为395kt），其中只有4%被回收，这使其成为一个重要的技术目标。因此，开发一种可以补充现有机械和化学方法的技术，在现有方法可能无法应用的领域将是有利的——要么帮助解决最具挑战性的塑料废物流，要么为现有工艺提供更清洁、更有价值的废物流。本工作提出发展“催化化学分选”。不同塑料中不同聚合物骨架的不同化学性质意味着可以利用特定官能团的反应性，在存在另一种聚合物的情况下选择性地解聚，包括混合物和共混物。这一概念的扩展将使复杂塑料废物的顺序、选择性解聚成为可能。为了实现这一目标，我们将从根本上推进催化解聚系统，使用混合计算和实验方法来识别和开发能够实现选择性和容忍真实塑料废物复杂性的铅系统，例如同一塑料中的添加剂，杂质，污染物和隐含聚合物混合物。该项目的重点是发展对这一挑战的理解和催化的基本应用，然而，考虑到塑料回收的重要性，研究将由我们的项目合作伙伴的见解指导，以便在项目完成后，科学方法适用于使用已开发的化学和计算工具开发针对行业特定挑战的开发。

There is an urgent global need to devise better strategies to recycle plastics. It is estimated that a total of 8300 million metric tonnes of plastics have been produced to date yet, incredibly, more than 40 years after the launch of the recycling symbol, less than 10% of waste plastics that have been manufactured are recycled. The rest are either poured into landfill, burned to produce CO2 and other harmful gases or, worst of all, discarded into the environment. Plastics will continue to be critical in addressing the growing demands of our society and to eradicate them as a whole is not a realistic solution. A key challenge therefore is fully and effectively dealing with the waste plastics that we generate. Better end-of-life options for plastic waste are urgently required. A key challenge in plastic recycling is addressing complex plastics wastes, exemplified by multilayer films and blends in which the components cannot be readily separated by mechanical means or in which the specific combinations cause problems in the leading chemical recycling methodologies. WRAP's Plastic Flow 2025 report estimates that, after bottles, film is the next largest consumer plastic packaging format (395kt in 2017) of which just 4% was recycled, making this an important technological target. Hence the development of a technology that can complement existing mechanical and chemical methods would be advantageous in areas where current methods may not be possible to apply - to either help address the most challenging plastic waste streams in their entirety or to provide cleaner, more valuable, waste streams for existing processes.This work proposes to develop 'catalytic chemical sorting'. The different chemistry of different polymer backbones in different plastics means that the reactivity of the specific functional groups can be leveraged to selectively depolymerise one polymer in the presence of another, including from mixtures and blends. Extension of this concept would enable the sequential, selective depolymerisation of complex plastic wastes. In order to achieve this, we will fundamentally advance catalytic systems for depolymerisation using a hybrid computational and experimental approach to identify and develop lead systems that can achieve selectivity and be tolerant of the complexities of real plastic wastes, such as additives, impurities, contaminants and implicit polymer mixtures within the same plastic. This project is focussed on the development of the understanding and fundamental application of catalysis to this challenge, however, given the importance of plastic recycling, the research will be guided by insights from our project partners such that on completion of the project, the scientific approach is suitable for development towards industry-specific challenges using the chemistry and computational tools that have been developed.