I-Corps: Materials for CO2 Capture

在石油工业中，CO2作为气体混合物中的污染物或杂质出现，并且由于CO2排放的环境影响，立法者开始要求从燃烧产物中分离CO2。因此，CO2分离在发电厂、重工业、制氢、天然气脱硫和空气净化厂等行业中是一个问题。然而，目前可用于CO2分离的选择是有限的且不经济的。一种当代的方法是吸收，这是一种成熟的方法，但能源密集且昂贵。例如，基于单乙醇胺（MEA）的化学吸收的基准，一种广泛使用的吸收剂，由于溶剂再生的高成本，目前每公吨CO2的成本超过70美元;总体而言，使用传统技术捕获发电厂的CO2排放需要工厂能量输出的20 - 30%。 这种高成本是工业上广泛采用CO2捕集技术的最大障碍。因此，工业界迫切需要开发高性能和低成本的技术和材料，以实现资本效率高的CO2捕集。一种有前途的CO2捕集替代方法是多孔材料吸附：用于CO2分离的候选吸附剂应选择性地从气体混合物中吸附CO2，并具有大的表面积以将CO2分子容纳到孔中。基于I-Corps团队成员最近开发的一种新型合适的吸附剂，该项目的目的是将一系列新的吸附剂（沸石咪唑骨架，或ZIF）商业化，这些吸附剂具有从其他气体中分离CO2的上级选择性，并具有显著的表面积来储存CO2。美国政府和其他几个国家和实体（如加拿大、中国和欧盟）已经实施了严格的排放标准，但目前还没有一种最佳产品或现有产品可满足所需的需求。拟议的ZIF具有出色的高选择性CO2捕获能力，因此在市场需求严峻的时候提供了革命性的解决方案。金属-有机骨架（MOFs）是由有机连接体和含金属节点构成的杂化多孔材料。MOFs提供的典型比表面积以及因此提供的气体吸附能力比沸石高一个数量级。 ZIF是M0F的子家族。它们具有M（Im）4沸石型骨架，其中四面体元素M是由咪唑酯（Im）部分桥连的过渡金属。ZIF可以吸附CO2排放，在需要再生之前，其储存量是现有吸附剂的五倍。例如，每单位体积的ZIF-69可以储存高达其体积83倍的二氧化碳。 此外，ZIF可以表现出高的化学和热稳定性，因此可以是用于CO2捕获的稳健方法。在这项全面的研究中，我们提出了一种新的ZIF亚类的合成，如通过基于蒙特-卡罗的模拟所示，与同构ZIF相比，具有100倍的CO2捕获能力。这种CO2捕获能力的增加伴随着对CH4、H2和N2的捕获能力的仅可忽略的变化;因此，CO2与其他气体的吸收比显著增加，表明在我们的新型ZIF中对CO2分离的非常高的选择性。这一系列能力可以显著降低燃烧发电厂、重工业、天然气加工和制氢公司的碳分离和捕获成本。

CO2 appears as a contaminant or impurity in gas mixtures in oil industries, and because of the environmental impacts of CO2 emissions, lawmakers are beginning to require the separation of CO2 from combustion products. Consequently, CO2 separation is an issue in power plants, heavy industries, hydrogen production, natural gas sweetening, and air purification plants, among other industries. However, the currently available options for CO2 separation are limited and uneconomical. One contemporary method is absorption, a well-matured but energy-intensive and expensive approach. For example, the benchmark for chemical absorption based on monoethanolamine (MEA), a widely used absorbent, currently imposes costs of over $70 per metric ton of CO2 due to the high cost of solvent regeneration; overall, capturing CO2 emissions from power plants using conventional technologies requires 20-30% of the plant's energy output. This high cost is the single largest obstacle for the widespread industrial adoption of CO2 capture technologies. Therefore, industry has an urgent need for the development of high-performance and low-cost technologies and materials that enable capital-efficient CO2 capture. A promising alternative process for CO2 capture is adsorption by porous materials: candidate adsorbents for CO2 separation should selectively adsorb CO2 from gas mixtures and have large surface areas to accommodate CO2 molecules into the pores. Based on a novel, suitable adsorbent recently developed by members of the proposed I-Corps team, the aim of this project is to commercialize a new series of adsorbents (zeolitic imidazolate frameworks, or ZIFs) that exhibit superior selectivity for separating CO2 from other gases and that have significant surface area to store it. This technology has been developed at a critical time for the CO2 capture market. Strict emission standards have been imposed by the U.S. government and several other countries and entities such as Canada, China, and the European Union, but there is not yet an optimal or even existing product available to meet the required needs. The proposed ZIF, with its outstanding capability for high-selectivity CO2 capture, therefore provides a revolutionary solution at a time of severe market need. Metal-organic frameworks (MOFs) are hybrid porous materials constructed from organic linkers and metal-containing nodes. The typical specific surface areas - and hence, gas adsorption capacities - that MOFs provide are an order of magnitude higher than those of zeolites. ZIFs are a subfamily of MOFs. They have an M(Im)4 zeolite-type framework in which tetrahedral elements, M, are transition metals bridged by imidazolate (Im) moieties. ZIFs can adsorb CO2 emissions and store five times more than existing adsorbents before requiring regeneration. For example, each unit volume of ZIF-69 can store up to 83 times its volume in CO2. Moreover, ZIFs can exhibit high chemical and thermal stability, and therefore can be robust processes for CO2 capture. In this comprehensive study, we propose the synthesis of a new subclass of ZIFs that, as indicated by Monte-Carlo-based simulation, have a 100-fold-increased CO2 capture capacity compared to the isostructural ZIFs. This increase in CO2 capture capacity was accompanied by only negligible changes in capture capacity for CH4, H2, and N2; therefore, the uptake ratio of CO2 to the other gases increased significantly, indicating very high selectivity for CO2 separation in our novel ZIFs. This set of abilities could significantly reduce the cost of carbon separation and capture at combustion-based power plants, heavy industries, natural gas processing, and hydrogen production companies.