ADSORPTION PERFORMANCE OF TOLUENE ON HYDROPHOBIC MODIFIED MOLECULAR SIEVES UNDER HIGH HUMIDITY
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摘要: 工程实践中Y分子筛在高湿度环境下吸附性能大幅降低,通过聚二烯丙基二甲基氯化铵(PDDA)预处理后进行mesoSiO2壳层生长得到Y@mesoSiO2,将聚二甲基硅氧烷(PDMS)通过化学气相沉积法接枝到Y@mesoSiO2壳层上,可获得疏水特性优异的Y@mesoSiO2-S核壳分子筛。采用SEM、TEM、XRD、XPS和比表面积及孔径分析仪对改性前后Y分子筛形貌和结构进行分析,通过静态和动态吸附实验评价其对水和甲苯的吸附性能。结果表明:mesoSiO2壳相在核相Y分子筛外表面成功生长,并将PDMS成功接枝在Y@mesoSiO2壳层后,Y@mesoSiO2-S的BET比表面积相比Y分子筛增加了2%;静态水蒸气吸附量从298 mg/g降至79 mg/g,动态水蒸气吸附量从245 mg/g降至76 mg/g,材料表面与水接触角得到显著提升。在RH80%时,Y@mesoSiO2-S和Y分子筛对甲苯的饱和吸附量分别为167.2,2.6 mg/g,相比RH20%,分别降低了6.7%和98.3%。与无mesoSiO2壳层的Y-S相比,Y@mesoSiO2-S的BET比表面积增加了46%,其在高湿度环境下(80%RH)对甲苯的饱和吸附量增加了51%。说明通过在Y分子筛与有机硅烷之间引入mesoSiO2壳层,可有效避免有机硅烷直接接枝在Y分子筛表面造成的孔道堵塞问题,同时提升了Y分子筛的疏水性能,改善其在高湿度环境下对甲苯的吸附性能。Abstract: Engineering practice showed that the adsorption performance of Y molecular sieve was greatly reduced under high humidity environment. In this paper, Y@mesoSiO2 was obtained by pretreating polydiallyl dimethylammonium chloride (PDDA) along with the growth of mesoSiO2 shell on Y molecular sieve. Polydimethylsiloxane (PDMS) was further grafted onto mesoSiO2 shell to prepare Y@mesoSiO2-S via chemical vapor deposition method. The morphology and structure of the modified Y molecular sieve were analyzed by SEM, TEM, XRD, XPS, surface area and pore size analyzer. Besides, the adsorption of water and toluene was evaluated by static and dynamic adsorption experiments. The results showed that the mesoSiO2 shell successfully grew on the outer surface of Y molecular sieve and PDMS was successfully grafted onto the Y@mesoSiO2 shell. Compared with Y molecular sieve, the BET specific surface area (SBET) of Y@mesoSiO2-S increased by 2%; meanwhile, the water contact angle was enhanced significantly, causing the static water absorption decreased from 298 mg/g to 79 mg/g, and the dynamic water absorption decreased from 245 mg/g to 76 mg/g. The saturated adsorption capacity of toluene on Y@mesoSiO2-S and Y molecular sieve were 167.2 mg/g and 2.6 mg/g at an RH of 80%, respectively, which decreased by 6.7% and 98.3% relatively, compared with an RH of 20%. When compared with Y-S without mesoSiO2 shell, Y@mesoSiO2-S presented increased SBET and the saturated adsorption capacity of toluene with 46% and 51% at an RH of 80%, respectively. This indicated that mesoSiO2 shell was introduced between Y molecular sieve and PDMS, which could avoid clogging of porosity caused by direct grafting PDMS on the surface of Y molecular sieve. Furthermore, this strategy could improve the hydrophobic property of Y molecular sieve, resulting in enhanced adsorption performance on toluene under high humidity.
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Key words:
- Y molecular sieve /
- hydrophobic modification /
- toluene /
- high humidity /
- adsorption property
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