Novel Membrane Catalytic Reactor for Waste Polylactic Acid Recycling and Valorisation

塑料包装的处理代表了一个重大的环境问题;尽管近年来塑料的回收利用有所增加，但目前的回收利用方法主要是机械或化学技术，导致较低等级的第二生命产品，并且许多材料仍然被填埋。引入由植物来源的糖等生物来源生产的塑料有可能减少对化石来源的依赖，并减少与制造相关的温室气体排放。聚乳酸已成为最有前途的生物可再生和生物降解聚合物之一，在包装，纺织和生物医学应用中有着广泛的应用。然而，缺乏可靠的方法回收聚乳酸可能会限制其广泛应用和市场增长。因此，存在一个重要的机会来开发一种方法来解聚/降解商品PLA，以通过先前尚未开发的途径生产增值的小分子，如乳酸酯。这样的分子可以被回收，以制造新的聚乳酸或其他增值化学品，包括溶剂，香料和plastics.We建议解决上述问题，通过开发一种催化过程降解/解聚的聚乳酸，集成膜分离，选择性地分离小分子产品在指定的分子量截止范围内，作为有价值的产品。首先，将开发该工艺的催化部分，建立在Jones之前关于salalen均相催化剂的工作基础上，并包括选择和设计最佳金属载体组合以实现PLA高转化率的工作计划。其次，将筛选用于分离产物分子的商业膜，这将提供必要的数据，以能够设计和制造用于特定分子量截留的定制膜。然后，我们的目标是将催化剂涂覆到膜上，以避免处理、分离和重复使用浆料催化剂的潜在困难。然后将按比例放大测试的催化剂和膜设计。将建造一个更大规模（1升）的反应器进行交叉流膜试验。研究结果将用于开发膜孔结构的反应和扩散模型的动力学模型。已经制定了一项活动方案，以便对学术界、工业界和公众产生影响，预计这项工作将提供新的催化剂、支持物和膜设计及性能数据。实验室放大数据将用于确定这些技术的协同工作情况，并提供可用于将该技术应用于工业生产的工艺设计。拟议的技术预计将带来许多潜在的好处，包括减少对化石衍生塑料的依赖，增加生物衍生聚合物市场的潜力，生产乳酸乙酯等增值化学品，新型催化剂和膜设计，英国拥有知识产权和专利。

The disposal of plastic packaging represents a significant environmental problem; although recycling of plastics has increased in recent years, current recycling methods are mainly mechanical or chemical techniques that result in lower grade second life products and much material is also still disposed of to landfill. The introduction of plastics produced from biological sources such as plant derived sugars has potential to reduce reliance on fossil derived sources and decrease emissions of greenhouse gases associated with manufacture. Polylactide has emerged as one of the most promising biorenewable and biodegradable polymers which has uses in packaging, textile and biomedical applications. However the lack of a reliable method for recycling polylactide could limit its widespread application and market growth. A significant opportunity therefore exists to develop a process to depolymerise/degrade commodity PLA to produce value-added small molecules, such as lactate esters, via routes which have not previously been developed. Such molecules could be recycled to make new PLA or other value added chemicals, including solvents, fragrances and plasticizers.We propose to address the above problems by developing a catalytic process for degradation/depolymerisation of PLA, integrated with a membrane separation to selectively isolate small molecule products within a specified molecular weight cut off range, as valuable products. Firstly the catalytic part of the process will be developed, building on previous work by Jones on salalen homogeneous catalysts, and including a work plan to select and design the best metal-support combinations to achieve a high conversion of PLA. Secondly, commercial membranes will be screened for the separation of product molecules, which will provide the necessary data to enable design and fabrication of bespoke membranes for a particular molecular weight cut off. We then aim to coat catalysts on to the membranes, so as to avoid the potential difficulties of working with, separating and reusing slurry catalysts. The tested catalyst and membrane designs will then be scaled up. A larger scale (1 litre) reactor will be constructed for carrying out crossflow membrane tests. The results of the studies will be used to develop kinetic models of the reaction and diffusion models for the membrane pore structure. A programme of activities for delivery of impact to the academic and industrial communities and the general public has been devised.The work is expected to deliver new catalysts, supports and membrane designs and performance data. Laboratory scale up data will be used to determine how well these techniques work together and to deliver a process design that could be deployed to take the technology in to industrial production.The proposed technologies are expected to deliver a number of potential benefits including reduced reliance on fossil derived plastics, potential to increase the market for bio-derived polymers, the production of value added chemicals such as ethyl lactate, novel catalyst and membrane designs, UK held intellectual property and patents.