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Separation of hexane isomers by introducing “triangular-like and quadrilateral-like channels” in a bcu-type metal-organic framework
Nano Research ( IF 9.9 ) Pub Date : 2020-03-09 , DOI: 10.1007/s12274-020-2714-z
Dongmei Wang , Xinglong Dong , Yu Han , Yunling Liu

The separation of hexane isomers is of vital importance to produce high quality gasoline in the petrochemical industry. However, the similar vapor pressure and boiling point of hexane isomers bring great difficulties and challenges in the separation process. Sieving effect, which allowing smaller molecules pass through and preventing others, should be a powerful strategy to solve this problem by making good use of porous materials. Therefore, physical separation by metal-organic framework (MOF) materials appears and becomes a burgeoning separation technique in industry. Due to the weak interaction between hexane isomers with absorbents, it puts forward higher requirements for the accurate design of MOF materials with optimal pore system. To address this issue, a novel MOF [Zn9(tba)9(dabco)3]·12DMA·6MeOH (abbreviation: Zn9(tba)9(dabco)3; H2tba = 4-(1H-tetrazol-5-yl)-benzoic acid; dabco = 1,4-diazabicyclo[2.2.2]octane; DMA = N, N-dimethylacetamide) with bcu network has been designed and synthesized by reticular chemistry strategy. Benefiting from the pre-designed topology and suitable linear ligand H2tba and dabco, the structure of Zn9(tba)9(dabco)3 exhibits two types of channels with triangular-like and quadrilateral-like geometry. Zn9(tba)9(dabco)3 with appropriate channel size and shape displays potential selective adsorption capacity of vapor-phase hexane isomers through sieving effect. Moreover, outstanding gas adsorptive separation properties of Zn9(tba)9(dabco)3 could also be speculated by theoretical ideal adsorbed solution theory (IAST), suggesting Zn9(tba)9(dabco)3 can be regarded as a potential adsorbent material for purification natural gas. Breakthrough experiments show that Zn9(tba)9(dabco)3 is capable of discriminating all four hexane isomers at 298 K, and the corresponding research octane number (RON) of the eluted mixture closes to 95, which is higher than the standard for industrially refined hexane blends (about 83). We speculate that sieving effect and diffusion are a synergetic contributory factor in their elution dynamics, which may be ascribed to temperature-dependent interaction between pore aperture and each isomer. This work presents a typical example for design of efficient MOF absorbents by reticular chemistry strategy.



中文翻译:

通过在bcu型金属有机框架中引入“三角形和四边形通道”来分离己烷异构体

己烷异构体的分离对于石化行业生产高质量汽油至关重要。然而,相似的己烷异构体的蒸气压和沸点在分离过程中带来了很大的困难和挑战。筛分效应(允许较小分子通过并阻止其他分子通过)应该是通过充分利用多孔材料来解决此问题的有力策略。因此,通过金属-有机骨架(MOF)材料进行的物理分离出现并成为工业中迅速发展的分离技术。由于己烷异构体与吸收剂之间的相互作用较弱,因此对具有最佳孔隙系统的MOF材料的精确设计提出了更高的要求。为了解决这个问题,新型的MOF [Zn 9(tba)9(dabco)3 ]·12DMA·6MeOH(缩写:Zn 9(tba)9(dabco)3; H 2 tba = 4-(1H-四唑-5-基)-苯甲酸; dabco = 1,4-二氮杂双环[ 2.2.2通过网状化学策略设计和合成了具有bcu网络的辛烷; DMA = N,N-二甲基乙酰胺。得益于预先设计的拓扑结构和合适的线性配体H 2 tba和dabco,Zn 9(tba)9(dabco)3的结构表现出两种类型的通道,具有三角形和四边形的几何形状。锌9(TBA)9(达布科)3具有合适通道尺寸和形状的分子筛通过筛分效应显示出气相正己烷异构体的潜在选择性吸附能力。此外,Zn 9(tba)9(dabco)3的出色的气体吸附分离性能也可以通过理论理想吸附溶液理论(IAST)推测,表明Zn 9(tba)9(dabco)3可以被视为潜在的吸附剂净化天然气的材料。突破性实验表明Zn 9(tba)9(dabco)3能够在298 K时分辨所有四种己烷异构体,并且洗脱混合物的相应研究辛烷值(RON)接近95,高于工业精制己烷共混物的标准(约83)。我们推测筛分效应和扩散是其洗脱动力学的协同贡献因素,这可能归因于孔和每个异构体之间的温度依赖性相互作用。这项工作为通过网状化学策略设计高效MOF吸收剂提供了一个典型实例。

更新日期:2020-03-09
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