Li Yan, Chen Hongwei, Wang Chaoran, Ye Yu, Li Libo, Song Xiaowei, Yu Jihong
State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, College of Chemistry, Jilin University 2699 Qianjin Street Changchun 130012 P. R. China
College of Chemical Engineering and Technology, Shanxi Key Laboratory of Gas Energy Efficient and Clean Utilization, Taiyuan University of Technology Taiyuan 030024 P. R. China.
Chem Sci. 2022 Apr 19;13(19):5687-5692. doi: 10.1039/d2sc00702a. eCollection 2022 May 18.
Small-pore silicoaluminophosphate (SAPO) zeolites with 8-ring pore windows and appropriate acidities/polarities, for example, SAPO-34 (CHA) and SAPO-56 (AFX), have proven to be potential adsorbing materials for selective adsorption of CO. However, SAPO-35 zeolites (LEV framework topology) synthesized using conventional templates are less reported for highly selective CO adsorption which might be due to inappropriate Si contents and acidities in the framework. In this work, by using -methylpiperidine (NMP) as a template, SAPO-35 zeolites with various Si contents were synthesized under hydrothermal conditions, which allowed SAPO-35 zeolites with modulated acidities and polarities. The CO adsorption and separation properties of SAPO-35_ (: Si/(Si + P + Al) in molar ratio) were investigated, and a close relationship between the acidity, polarity and CO adsorption and separation capacity was revealed. SAPO-35_0.14 with the strongest acidity showed the highest CO uptake of 4.76 mmol g (273 K and 100 kPa), and appeared to be one of the best SAPO materials for CO adsorption. Moreover, increased Brønsted acidity can significantly enhance the adsorption selectivity of CO over N. At 298 K and 100 kPa, SAPO-35_0.14 showed the highest CO/N selectivity of 49.9, exhibiting potential for industrial processes. Transient binary breakthrough experiments on SAPO-35_0.14 further proved the efficient separation performance and stable circulation. The results of this study prove that the framework Si content of SAPO-35 zeolites is essential for regulating their CO adsorption performance. This work demonstrates that modulating the silicon content and acidity in SAPO zeolites a suitable choice of template, as well as polarity, is of great significance for the rational synthesis of zeolites with superior CO adsorption and separation abilities.
具有8元环孔窗且酸度/极性合适的小孔硅铝磷酸盐（SAPO）沸石，例如SAPO - 34（CHA）和SAPO - 56（AFX），已被证明是选择性吸附CO的潜在吸附材料。然而，使用传统模板合成的SAPO - 35沸石（LEV骨架拓扑结构）在高选择性CO吸附方面的报道较少，这可能是由于骨架中Si含量和酸度不合适所致。在本工作中，以N - 甲基哌啶（NMP）为模板，在水热条件下合成了具有不同Si含量的SAPO - 35沸石，从而得到了酸度和极性可调的SAPO - 35沸石。研究了SAPO - 35_（：Si /（Si + P + Al）的摩尔比）的CO吸附和分离性能，并揭示了酸度、极性与CO吸附和分离能力之间的密切关系。酸度最强的SAPO - 35_0.14在273 K和100 kPa下表现出最高的CO吸附量，为4.76 mmol g，似乎是用于CO吸附的最佳SAPO材料之一。此外，增加的布朗斯台德酸度可显著提高CO对N的吸附选择性。在298 K和100 kPa下，SAPO - 35_0.14表现出最高的CO / N选择性，为49.9，展现了在工业过程中的应用潜力。对SAPO - 35_0.14进行的瞬态二元穿透实验进一步证明了其高效的分离性能和稳定的循环性能。本研究结果证明，SAPO - 35沸石的骨架Si含量对于调节其CO吸附性能至关重要。这项工作表明，调节SAPO沸石中的硅含量和酸度——选择合适的模板以及极性，对于合理合成具有优异CO吸附和分离能力的沸石具有重要意义。
