Pore size tuning of sol-gel-derived triethoxysilane (TRIES) membranes for gas separation
Pore size tuning of sol-gel-derived triethoxysilane (TRIES) membranes for gas separation
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DOI：
10.1016/j.memsci.2016.11.006
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发表时间：
2017-02
影响因子：
9.5
通讯作者：
M. Kanezashi;Rui Matsugasako;H. Tawarayama;Hiroki Nagasawa;T. Tsuru
中科院分区：
文献类型：
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作者：
M. Kanezashi;Rui Matsugasako;H. Tawarayama;Hiroki Nagasawa;T. Tsuru
三乙氧基硅烷（TRIES）作为侧挂型烷氧基硅烷由三个乙氧基和一个Si-H键组成，被用作用于制造气体分离膜的Si前体。膜的制备参数，如溶胶制备条件和焙烧温度对Si-H基团和网络结构的影响进行了评估。水溶液中Si-H基团的脱氢程度与溶胶中H2O/Si摩尔比无关，但乙氧基（-OEt）的水解和聚合程度取决于H2O摩尔比。在550 °C下在N2下煅烧的TRIES膜显示网络尺寸随着溶胶中H2O/Si摩尔比的增加而减小。由TRIES得到的网络孔径大小也依赖于煅烧温度，并且在较低的煅烧温度下，网络尺寸减小。例如，在550 °C下煅烧的TRIES膜显示出对He/N2和H2/N2的高选择性，分别为约1000和600，然而，在300 °C下煅烧的情况下，努森扩散对小分子占主导地位（H2/N2选择性：4.3），分子筛有利于大分子（H2/CF 4：>100，H2/SF6：>400）。当通过在300 °C下煅烧来制造TRIES膜时，大多数Si-H基团仍然存在于网络中，TRIES膜的估计网络孔径为0.577 nm，其大于在350 °C下煅烧的四乙氧基硅烷（TEOS）膜的网络孔径（0.426 nm）。另一方面，当在550 °C下制造TEOS和TRIES膜时，两种膜显示出大致相同的网络孔径（TEOS：0.385 nm，TRIES：0.382 nm），这是由于在形成Si-OH基团以及形成Si-O-Si键时Si-H基团的脱氢。
Triethoxysilane (TRIES), which consists of three ethoxy groups and a Si-H bond as a pendant-type alkoxysilane, was utilized as a Si precursor for the fabrication of a gas separation membrane. The effect of membrane fabrication parameters such as sol preparation conditions and calcination temperatures on Si-H groups and network structures was evaluated. The degree of dehydrogenation of Si-H groups in aqueous solution was independent of the H2O/Si molar ratio in the sol, but the degree of hydrolysis and polymerization of ethoxy groups (-OEt) depended on the H2O molar ratio. TRIES membranes calcined at 550 °C under N2showed a decrease in network size with an increase in the H2O/Si molar ratio in the sol. The TRIES-derived network pore size also depended on the calcination temperature, and the network size was decreased under lower calcination temperatures. For example, a TRIES membrane calcined at 550 °C showed high selectivity for He/N2and H2/N2at approximately 1000 and 600, respectively, however, in the case of calcination at 300 °C, Knudsen diffusion dominated for small molecules (H2/N2selectivity: 4.3) and molecular sieving favored large molecules (H2/CF4: >100, H2/SF6: >400). When a TRIES membrane was fabricated by calcination at 300 °C, most Si-H groups were still present in the networks, the estimated network pore size for the TRIES membrane was 0.577 nm, which was larger than that of a tetraethoxysilane (TEOS) membrane calcined at 350 °C (0.426 nm). On the other hand, when TEOS and TRIES membranes were fabricated at 550 °C, both membranes showed approximately the same network pore size (TEOS: 0.385 nm, TRIES: 0.382 nm), due to the dehydrogenation of Si-H groups in the formation of Si-OH groups as well as for the forming of a Si–O–Si bond.