Yu Tao, Zheng Jinyu, Su Shikun, Wang Yundong, Xu Jianhong, Liu Zhendong
State key Laboratory of Chemical Engineering, Department of Chemical Engineering, Tsinghua University, Haidian District, Beijing 100084, China.
Sinopec Research Institute of Petroleum Processing Co., LTD., Beijing 100083, China.
JACS Au. 2024 Mar 1;4(3):985-991. doi: 10.1021/jacsau.3c00733. eCollection 2024 Mar 25.
Often, trace impurities in a feed stream will cause failures in industrial applications. The efficient removal of such a trace impurity from industrial steams, however, is a daunting challenge due to the extremely small driving force for mass transfer. The issue lies in an activity-stability dilemma, that is, an ultrafine adsorbent that offers a high exposure of active sites is favorable for capturing species of a low concentration, but free-standing adsorptive species are susceptible to rapidly aggregating in working conditions, thus losing their intrinsic high activity. Confining ultrafine adsorbents in a porous matrix is a feasible solution to address this activity-stability dilemma. We herein demonstrate a proof of concept by encapsulating ZnO nanoclusters into a pure-silica MFI zeolite (ZnO@silicalite-1) for the ultradeep removal of HS, a critical need in the purification of hydrogen for fuel cells. The Zn species and their interaction with silicalite-1 were thoroughly investigated by a collection of characterization techniques such as HADDF-STEM, UV-visible spectroscopy, DRIFTS, and H MAS NMR. The results show that the zeolite offers rich silanol defects, which enable the guest nanoclusters to be highly dispersed and anchored in the silicious matrix. The nanoclusters are present in two forms, Zn(OH) and ZnO, depending on the varying degrees of interaction with the silanol defects. The ultrafine nanoclusters exhibit an excellent desulfurization performance in terms of the adsorption rate and utilization. Furthermore, the ZnO@silicalite-1 adsorbents are remarkably stable against sintering at high temperatures, thus maintaining a high activity in multiple adsorption-regeneration cycles. The results demonstrate that the encapsulation of active metal oxide species into zeolite is a promising strategy to develop fast responsive and highly stable adsorbents for the ultradeep removal of trace impurities.
通常情况下，进料流中的痕量杂质会导致工业应用出现故障。然而，由于传质驱动力极小，从工业蒸汽中高效去除此类痕量杂质是一项艰巨的挑战。问题在于活性-稳定性困境，即具有高活性位点暴露度的超细吸附剂有利于捕获低浓度物质，但独立的吸附物种在工作条件下容易迅速聚集，从而失去其固有的高活性。将超细吸附剂限制在多孔基质中是解决这一活性-稳定性困境的可行方案。我们在此通过将ZnO纳米团簇封装到纯硅MFI沸石（ZnO@silicalite-1）中，展示了一种概念验证，用于超深度去除HS，这是燃料电池氢气净化中的一项关键需求。通过诸如高角度环形暗场扫描透射电子显微镜（HADDF-STEM）、紫外可见光谱、漫反射红外傅里叶变换光谱（DRIFTS）和魔角旋转核磁共振（H MAS NMR）等一系列表征技术，对锌物种及其与silicalite-1的相互作用进行了深入研究。结果表明，该沸石具有丰富的硅醇缺陷，这使得客体纳米团簇能够高度分散并锚定在硅质基质中。根据与硅醇缺陷的相互作用程度不同，纳米团簇以两种形式存在，即Zn(OH)和ZnO。就吸附速率和利用率而言，超细纳米团簇表现出优异的脱硫性能。此外，ZnO@silicalite-1吸附剂在高温下对烧结具有显著的稳定性，因此在多个吸附-再生循环中保持高活性。结果表明，将活性金属氧化物物种封装到沸石中是开发用于超深度去除痕量杂质的快速响应且高度稳定的吸附剂的一种有前景的策略。
