High Hexane Sorption Capacity of Loosely Crosslinked PDMS Rubbers at Low Temperatures: Macromolecular and Physicochemical Elucidation for VOC Recovery
High Hexane Sorption Capacity of Loosely Crosslinked PDMS Rubbers at Low Temperatures: Macromolecular and Physicochemical Elucidation for VOC Recovery
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DOI：
10.1016/j.seppur.2022.122634
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发表时间：
2022-11
影响因子：
8.6
通讯作者：
M. Inoue;E. Ismail;S. Samitsu;H. Kanoh;I. Ichinose
中科院分区：
文献类型：
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作者：
M. Inoue;E. Ismail;S. Samitsu;H. Kanoh;I. Ichinose
采用有机溶剂稀释聚二甲基硅氧烷（PDMS）大分子单体和交联剂的反应混合物，制备了一系列软质PDMS橡胶。当在室温下浸入纯己烷中时，最软橡胶的溶胀度为600重量%。根据Flory-Huggins方程，计算出每1g橡胶的己烷吸附自由能变化为-7.4J g− 1，聚合物链的熵贡献比常规PDMS橡胶大1.6J g− 1。松散交联的PDMS橡胶在298 K和195 K下分别可以吸附776 mg g− 1和606 mg g− 1的己烷。后者的值是4.4倍大于传统的PDMS橡胶。在23 Pa的低压下，PDMS橡胶在195 K时吸附的己烷量是298 K时的3500倍。这种高吸附量是因为这种软PDMS橡胶的膨胀能小。当从Clausius-Clapeyron方程计算时，松散交联的PDMS橡胶的吸附热为30.3 kJ mol− 1。该值显著小于商业活性炭的值（75 kJ mol-1）。与活性炭不同，PDMS橡胶对水不敏感，即使在饱和湿度下也能选择性地吸附VOC。由于其溶胀势大、吸附/脱附热小，在化工、石油天然气等行业中，聚二甲基硅氧烷（PDMS）橡胶将成为回收烷烃、异烷烃等挥发性有机物的不可缺少的吸附剂。
A series of soft polydimethylsiloxane (PDMS) rubbers was obtained by diluting reaction mixtures of a PDMS macromer and a crosslinker with an organic solvent. The degree of swelling of the softest rubber was 600 wt% when immersed in pure hexane at room temperature. From the Flory–Huggins equations, the free energy change for hexane sorption per 1 g rubber was calculated to be −7.4 J g−1and the entropy contribution of the polymer chains was 1.6 J g−1larger than that of the conventional PDMS rubber. The loosely crosslinked PDMS rubber could sorb 776 mg g−1of hexane at 298 K and 606 mg g−1at 195 K. The latter value was 4.4 times larger than that of the conventional PDMS rubber. At a low pressure of 23 Pa, the PDMS rubber sorbed a 3500-fold greater amount of hexane at 195 K, as compared with the value at 298 K. This high sorption amount is because the expansion energy of such soft PDMS rubber is small. The sorption heat of the loosely crosslinked PDMS rubber was 30.3 kJ mol−1when calculated from the Clausius–Clapeyron equation. This value is substantially smaller than that of commercial activated carbon (75 kJ mol−1). Unlike activated carbon, PDMS rubber is insensitive to water and selectively sorbs VOCs even under a saturated humidity. Because of the large swelling potential and small sorption/desorption heat, the loosely crosslinked PDMS rubber will be an indispensable sorbent for the recovery of flammable gasses such as alkane andiso-alkane VOCs in the chemical and oil and gas industries.