Novel Membrane Catalytic Reactor for Waste Polylactic Acid Recycling and Valorisation

塑料包装的处理是一个严重的环境问题；尽管塑料回收近年来有所增加，但目前的回收方法主要是机械或化学技术，导致第二生命产品等级较低，许多材料仍被处理到垃圾填埋场。采用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，并减少与制造有关的温室气体排放。聚乳酸是一种最有前途的生物可再生和生物可降解聚合物，在包装、纺织和生物医学等领域具有广泛的应用前景。然而，缺乏可靠的回收聚乳酸的方法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/降解商品聚乳酸，以通过以前没有开发过的路线来生产增值小分子，例如乳酸酯。这些分子可以循环再用来制造新的聚乳酸或其他增值化学品，包括溶剂、香料和增塑剂。我们建议通过发展一种降解/解聚聚乳酸的催化过程，并结合膜分离来选择性地分离特定相对分子质量范围内的小分子产品，作为有价值的产品来解决上述问题。首先，将在Jones之前关于Salalen均相催化剂的工作的基础上，开发该工艺的催化部分，并包括选择和设计最佳金属载体组合以实现高转化率的工作计划。其次，将对商业膜进行筛选，以分离产品分子，这将提供必要的数据，使设计和制造特定截留分子量的定制膜成为可能。然后，我们的目标是将催化剂涂层到膜上，以避免使用、分离和重复使用浆状催化剂的潜在困难。然后，测试的催化剂和膜设计将被放大。将建造一个更大规模(1升)的反应器，以进行错流膜试验。研究结果将用于建立膜孔结构的反应动力学模型和扩散模型。已经制定了一项向学术界和工业界以及公众提供影响的活动方案，预计将提供新的催化剂、载体、膜设计和性能数据。实验室放大数据将被用来确定这些技术协同工作的效果如何，并提供可以部署的工艺设计，将技术带入工业生产。拟议的技术预计将带来一系列潜在好处，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、英国拥有的知识产权和专利。

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.