Abstract:

Nitrous oxide (N₂O) is the third largest greenhouse gas next to CO₂ and CH₄, and its emission will aggravate the greenhouse effect. However, N₂O has a wide range of uses, so its recovery is of great significance. CO₂ and N₂O coexist in the tail gas from the production of acid via the phenol and cyclohexane processes. Since they have the same kinetic diameter and similar physical properties, it is a great challenge to separate them. In this paper, the effect of monovalent alkali metal cations (Li⁺, Na⁺, K⁺, Cs⁺) in A-type zeolites on the adsorption and separation performance of CO₂/N₂O was investigated. Then, the samples were characterized by XRD, ICP-OES, SEM and TGA and the adsorption performance, IAST selectivity and separation performance were studied. The research results show that with the increase of alkali metal cation radius, the adsorption capacity of CO₂ and N₂O decreases gradually, and CsA almost does not adsorb CO₂ and N₂O. However, the selectivity of CO₂/N₂O shows an opposite trend, with KA reaching the highest selectivity (2.6). The penetration experiment results of mixed gases ($V_{\mathrm{C}{\mathrm{O}}_{\mathrm{2}}}$/$V_{{\mathrm{N}}_{\mathrm{2}}\mathrm{O}}$=50%/50%) also indicate that KA has some CO₂/N₂O adsorption separation performance.

Key words: carbon dioxide, nitrous oxide, zeolite, alkali metal cations, ion exchange, adsorption separation

摘要：

氧化亚氮（N₂O）是仅次于CO₂和CH₄的第三大温室气体，排放后加剧温室效应，而N₂O具有广泛的用途，因此对其进行回收具有重要意义。苯酚法和环己烷法生产己二酸时排放的尾气中CO₂与N₂O共存，二者具有相同的动力学直径和相似的物理性质，它们的分离具有很大的挑战。研究了A型沸石中一价碱金属阳离子（Li⁺、Na⁺、K⁺、Cs⁺）对CO₂/N₂O吸附分离性能的影响，通过XRD、ICP-OES、SEM和TGA进行表征，并对吸附性能、IAST选择性以及分离性能进行了研究。研究结果表明，随着碱金属阳离子半径的增大，CO₂和N₂O的吸附容量逐渐降低，CsA几乎对CO₂和N₂O均不吸附；但CO₂/N₂O选择性却呈相反的趋势，其中KA的选择性达到最高（2.6），混合气体（$V_{\mathrm{C}{\mathrm{O}}_{\mathrm{2}}}$/$V_{{\mathrm{N}}_{\mathrm{2}}\mathrm{O}}$=50%/50%）穿透实验结果也表明KA具有一定的CO₂/N₂O吸附分离性能。

关键词: 二氧化碳, 氧化亚氮, 沸石, 碱金属阳离子, 离子交换, 吸附分离