Life Cycle Assessment of Metal Organic Frameworks

随着减少大气中碳排放的需要日益增加，电厂烟气中二氧化碳的去除正被强调为实现这一目标的一个主要因素。2023年3月，英国政府宣布为两个集群的8个项目提供资金，这些项目专注于碳捕获和封存技术。目前的主要技术是胺溶剂，它与二氧化碳结合，将其从烟道气中分离出来，然后通过可逆反应将其去除，从而使二氧化碳得以安全储存，胺可以再次使用。然而，这种溶剂的再生是高度耗能的，胺的降解会释放出对环境有害的废物。近年来获得更多接触的另一种技术是MOF(金属有机骨架)，它是金属离子和有机连接物的规则笼状结构，可以捕获二氧化碳，然后可以倒空储存，MOF再次使用。根据目前这项技术的TRL，它仍然比胺贵得多，但随着成本的下降，它被视为替代胺的最可行的选择。再生能量低得多，对环境有害的废物很少，完全可回收利用的可能性很小。由于MOF还相对较新，几乎没有研究来证实这些说法，所以这个项目将涉及绘制MOF的生命周期图，从它们最初的制造到使用，最后到它们的处置或回收成为新的MOF材料，以便与目前市场上的同类材料相比，有效地比较该技术的有害环境影响和更高的能效。这将通过进行生命周期评估(LCA)来完成。一种标准化的方法，用于评估从获得原材料到处置的产品或服务，将工作过程分为4个主要阶段(目标和范围、库存、影响评估、解释)，然后可用于跟踪产品或服务在其整个生命周期中的质量数量、能量平衡和环境影响。对于MOF CC，只有2个这样的研究，而且只针对特定的材料和制造工艺，所以创建一个可以应用于许多MOF的完整和详细的模型将是有益的。从现在起，该模型将扩展到包括更多的过程和细节，并将转换为更大的行业规模的模型。还有一些因素影响MOF的长期使用，需要进行测试和分析。使用MOF的两个主要参数是温度和压力，因为MOF必须加热到大约100摄氏度才能进行吸附，并通过对材料施加真空来去除二氧化碳。因此，需要研究MOF相对于这些因素的物理降解，以确定材料在需要处置或回收之前可以有效使用的时间长度。正在设计和测试钻机，以验证温度和/或压力波动，以确定每个MOF在长期使用期间的坚固程度。

With the increasing need to reduce carbon emissions into the atmosphere, removal of carbon dioxide in flue gas from power plants is being highlighted as a major factor towards this goal. In March 2023, the UK government announced funding for 8 projects across 2 clusters focussing on Carbon Capture and Storage technologies. The current predominant technology is amine solvents, which binds with the CO2 to isolate it from the flue gas, which can then be removed through a reversible reaction to allow the CO2 to be stored safely and the amines to be used again. However, this regeneration of the solvent is highly energy intensive, and the degradation of amines releases waste products that are harmful to the environment.An alternative technology that has been gaining greater exposure in recent years are MOFs (metal organic frameworks), which are regular cage-like structures of metal ions and organic linkers which trap CO2, and can then be emptied for storage and the MOF used again. Based on the current TRL for this technology, it is still much more expensive than amines, but as costs come down, it is being seen as the most viable option to replace amines. The regeneration energy is much lower, and there is very little waste product that is harmful to the environment, with the possibility of being completely recyclable.As MOFs are still relatively new, there is little research to corroborate these claims, so this project will involve mapping the life-cycle of MOFs, from their initial manufacture to their use, and finally to their disposal or recycling into new MOF materials, to allow an effective comparison of the reduction in harmful environmental impacts and greater energy efficiency of the technology compared to current market equivalents.This will be done by conducting an LCA (life-cycle assessment), a standardised method for assessing a product or service from the acquisition of raw materials through to disposal, laying out the working process in 4 main stages (goal and scope, inventory, impact assessment, interpretation) that can then be used to track the mass quantities, energy balances and environmental impacts of that product or service over its complete life cycle. There are only 2 such studies for MOF CC and for only specific materials and manufacturing processes, so creating a complete and detailed model that can be applied to numerous MOFs would be beneficial. From here, the model will be expanded to include more processes and details, as well as being converted to a larger, industry-scale model.There are also a number of factors which affect the long-term use of MOFs which need to be tested and analysed. The two main parameters for use of MOFs are temperature and pressure, since the MOF must be heated to roughly 100oC to perform adsorption, and the CO2 is removed by applying a vacuum to the material. As such, the physical degradation of MOF against these factors needs to be studied, to determine the length of time the material can be used for effectively before requiring disposal or recycling. Rigs are being designed and tested to validate temperature and/or pressure swing to determine how robust each MOF is during prolonged use.