Direct air capture (DAC) of CO plays an indispensable role in achieving carbon-neutral goals as one of the key negative emission technologies. Since large air flows are required to capture the ultradilute CO from the air, lab-synthesized adsorbents in powder form may cause unacceptable gas pressure drops and poor heat and mass transfer efficiencies. A structured adsorbent is essential for the implementation of gas-solid contactors for cost- and energy-efficient DAC systems. In this study, efficient adsorbent poly(ethyleneimine) (PEI)-functionalized Mg-Al-CO layered double hydroxide (LDH)-derived mixed metal oxides (MMOs) are three-dimensional (3D) printed into monoliths for the first time with more than 90% adsorbent loadings. The printing process has been optimized by initially printing the LDH powder into monoliths followed by calcination into MMO monoliths. This structure exhibits a 32.7% higher specific surface area and a 46.1% higher pore volume, as compared to the direct printing of the MMO powder into a monolith. After impregnation of PEI, the monolith demonstrates a large adsorption capacity (1.82 mmol/g) and fast kinetics (0.7 mmol/g/h) using a CO feed gas at 400 ppm at 25 °C, one of the highest values among the shaped DAC adsorbents. Smearing of the amino-polymers during the post-printing process affects the diffusion of CO, resulting in slower adsorption kinetics of pre-impregnation monoliths compared to post-impregnation monoliths. The optimal PEI/MeOH ratio for the post-impregnation solution prevents pores clogging that would affect both adsorption capacity and kinetics.

中文翻译：

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3D 打印聚（乙撑亚胺）功能化镁铝混合金属氧化物整体，用于直接空气捕获二氧化碳


直接空气捕获二氧化碳（DAC）作为关键的负排放技术之一，在实现碳中和目标方面发挥着不可或缺的作用。由于需要大量气流来捕获空气中的超稀二氧化碳，因此实验室合成的粉末状吸附剂可能会导致不可接受的气压下降以及传热传质效率差。结构化吸附剂对于实现经济高效的 DAC 系统的气固接触器至关重要。在这项研究中，高效吸附剂聚（乙撑亚胺）（PEI）功能化的 Mg-Al-CO 层状双氢氧化物（LDH）衍生的混合金属氧化物（MMO）首次被三维（3D）打印成整体材料，具有更多吸附剂负载量超过 90%。通过首先将 LDH 粉末打印成整体材料，然后煅烧成 MMO 整体材料，对打印过程进行了优化。与直接将 MMO 粉末打印成整体材料相比，这种结构的比表面积高出 32.7%，孔体积高出 46.1%。浸渍 PEI 后，在 25 °C 下使用 400 ppm 的 CO 原料气时，整体材料表现出较大的吸附容量 (1.82 mmol/g) 和快速动力学 (0.7 mmol/g/h)，这是成型材料中最高的值之一。 DAC吸附剂。打印后过程中氨基聚合物的涂抹会影响 CO 的扩散，导致浸渍前整体材料的吸附动力学比浸渍后整体材料更慢。浸渍后溶液的最佳 PEI/MeOH 比例可防止孔堵塞，从而影响吸附容量和动力学。