For the capture of CO₂ from flue gas and decarbonization of natural gas streams, an ideal adsorbent should have a high selectivity for CO₂ over N₂ and CH₄. In this work, through adjusting the proportions of extra-framework K⁺ and Cs⁺ cations and varying the Si/Al ratios of the zeolite ZK-5, the small “molecular gate” adsorbent ZK-5-n-K has been prepared. An increase in the number of K⁺ cations prevents the ingress of the larger molecules CH₄ and N₂, while allowing entry of the smaller CO₂; the net result is that CO₂ capture from CH₄ or N₂ is achieved with unusually high selectivity, of the order of 1 × 10⁵. Grand canonical Monte Carlo simulations show that the extra-framework K⁺ and Cs⁺ cations are positioned at different locations in the ZK-5; K⁺ locates near the 8-ring window, whereas Cs⁺ resides in the interior regions. The separation performances of 12 different K⁺- and Cs⁺-doped ZK-5 structures (with four different Si/Al ratios of 3.17, 3.36, 3.46, and 3.57) have been investigated. Transient breakthrough simulations have been used to quantify the CO₂ capture performances in four sets of separations: 30%/70%, 5%/95%, and 2%/98% CO₂/CH₄ mixtures at a total pressure of 1 MPa, and a 15%/85% CO₂/N₂ mixture at a total pressure of 100 kPa. In all cases, the selectivities were sufficiently high to ensure that the separation performance was primarily governed by the CO₂ uptake capacity. The overall conclusion to be drawn from this work is that ZK-5 is a suitable adsorbent for the decarbonization of natural gas.

为了从烟道气中捕集CO ₂和天然气流脱碳，理想的吸附剂应具有比N ₂和CH ₄高的CO ₂选择性。在这项工作中，通过调节骨架外K ⁺和Cs ⁺阳离子的比例并改变沸石ZK-5的Si / Al比，制备了小的“分子门”吸附剂ZK-5- n -K。增加K ⁺阳离子的数量可以阻止较大分子CH ₄和N _2的进入，同时允许较小CO _2的进入; 最终结果是CO ₂从CH ₄或N ₂捕获的捕获具有非常高的选择性，约为1×10 ⁵。大经典的蒙特卡洛模拟表明，额外的框架K ⁺和Cs ⁺阳离子位于ZK-5中的不同位置。K ⁺位于8环窗口附近，而Cs ⁺位于内部区域。研究了12种不同的K ⁺和Cs ⁺掺杂的ZK-5结构（四种不同的Si / Al比为3.17、3.36、3.46和3.57）的分离性能。瞬态突破模拟已用于量化CO ₂在四组分离中的捕集性能：总压力为1 MPa的30％/ 70％，5％/ 95％和2％/ 98％的CO ₂ / CH ₄混合物和15％/ 85％的CO ₂ /总压力为100 kPa的N ₂混合物。在所有情况下，选择性都足够高，以确保分离性能主要受CO ₂吸收能力的支配。从这项工作中得出的总体结论是，ZK-5是天然气脱碳的合适吸附剂。