Tailoring a Thermally Stable Amorphous SiOC Structure for the Separation of Large Molecules: The Effect of Calcination Temperature on SiOC Structures and Gas Permeation Properties

Abstract

A SiOC membrane with high oxidative stability for gas separation was tailored by utilizing vinyltrimethoxysilane, triethoxysilane, and 1,1,3,3-tetramethyldisiloxane as Si precursors. Amorphous SiOC networks were formed via the condensation of Si–OH groups, the hydrosilylation of Si–H and Si–CH=CH 2 groups, and a crosslinking reaction of Si–CH 3 groups, respectively. The crosslinking of Si–CH 3 groups at temperatures ranging from 600 to 700 °C under a N 2 atmosphere was quite effective in constructing a Si–CH 2 –Si unit without the formation of mesopores, which was confirmed by the results of N 2 adsorption and by the gas permeation properties. The network pore size of the SiOC membrane calcined at 700 °C under N 2 showed high oxidative stability at 500 °C and was appropriate for the separation of large molecules (H 2 /CF 4 selectivity: 640, H 2 /SF 6 : 2900, N 2 /CF 4 : 98). A SiOC membrane calcined at 800 °C showed H 2 /N 2 selectivity of 62, which was approximately 10 times higher than that calcined at 700 °C because the SiOC networks were densified by the cleavage and redistribution reactions of Si–C and Si–O groups.

Preparation and Gas Separation of Amorphous Silicon Oxycarbide Membrane Supported on Silicon Nitride Membrane

“…No absorption peak of the C=C bond was seen near 1600 cm −1 because the C=C bond in TMTVS reacted with the Si-H bond in PHMS to form a Si-CH 2 -CH 2 -Si bond, which was completely consumed. Si-H disappeared at temperatures lower than 600 °C through the following equation [ 31 ]: Si-CH 3 + Si-H → Si-CH 2 -Si + H 2 …”

“…The ideal separation factor for H2 and CO2 was about 20, which was much higher than the corresponding ideal Knudsen diffusion selectivity (4.69), indicating that the membrane Figure 7a shows the nitrogen adsorption isotherm at −196 °C of the SiOC membrane obtained at 1000 °C. The low nitrogen adsorption capacity in the relative pressure range of 0.01 to 1.0 indicates that the SiOC membrane was non-porous, which may be caused by the compactness of the SiOC structure [31,53]. So, the permeance of gas through the membrane should obey a mechanism involving jumps between solubility sites for non-porous membranes [57].…”

“…Compared with the other two methods, the membrane separation method has received more and more attention due to its simple operation [ 21 ], low energy consumption [ 22 , 23 , 24 ], low investment cost [ 25 ] and high efficiency [ 26 , 27 ]. Many membranes have been studied [ 28 ], such as graphene oxide (GO) [ 29 , 30 ], polymers [ 31 , 32 , 33 , 34 , 35 ], pure metal membranes [ 28 ], mixed-matrix membranes [ 28 ] and zeolitic imidazolate frameworks (ZIFs) [ 36 , 37 , 38 , 39 , 40 ]. The porous structure of carbon membranes partially collapses at high temperatures [ 28 ].…”

Pore size tuning of bis(triethoxysilyl)propane (BTESP)-derived membrane for gas separation: Effects of the acid molar ratio in the sol and of the calcination temperature

“…This indicates that a BTESP network structure calcined at 600 o C has various carbon structures. The peaks derived from the bridged alkyl chain between the Si atoms had approximately disappeared, and a peak assigned to the methyl group (-6 ppm) was only detected [59][60][61] in the powder calcined at 800 o C.…”

Near zero-strain silicon oxycarbide interphases for stable Li-ion batteries

“…For the SiOC-H synthesis at 1000 °C, a redistribution process between residual Si–O bonds and the newly generated Si–C bonds favours the formation of the SiOC phase. 18 The removal of residual SiO 2 after the Mg reduction ensures the formation of the SiOC phase in both cases, resulting in a chemically inactive SiOC matrix in the final product. Fig.…”