Development of hydrogen-selective triphenylmethoxysilane-derived silica membranes with tailored pore size by chemical vapor deposition

Abstract

Amorphous silica membranes were developed, based on an in silico molecular design, to exhibit excellent hydrogen-selective performance for separating hydrogen from mixtures containing larger organic molecules, such as methylcyclohexane and toluene. Triphenylmethoxysilane (TPMS) was synthesized and used as a novel precursor to prepare membranes by the counter-diffusion chemical vapor deposition method. Under the optimized bubbler temperature and counter-diffusion chemical vapor deposition reaction time, the fresh membranes showed high reproducibility and high hydrogen permeance in the order of 10 −6 mol m − 2 s − 1 Pa − 1 and high H2/SF6 ideal selectivity of over 12000 at 573 K. Moreover, the TPMS-derived membrane exhibited good stability after hydrogen regeneration, even after placement in a dehumidifier cabinet at room temperature for 90 days. Single gas permeation performance and normalized Knudsen-based permeance evaluation showed that the TPMS-derived membrane (three phenyl groups on the precursor) had a pore size of 0.486 nm, and exhibited looser structures with larger pore size than those of a diphenyldimethoxysilane (DPDMS)-derived membrane (two phenyl groups on the precursor). These results suggest that the pore size of silica membranes can be tailored with various structured silica precursors containing phenyl groups.

Silica-Based Membranes with Molecular-Net-Sieving Properties: Development and Applications

“…Organosilicon compounds containing Si-C bonding in the structure were reported using phenyl groups (Ohta et al, 2008;Zhang et al, 2016) or alkyl groups (Nomura et al, 2007(Nomura et al, , 2014. Nakao group used tetramethoxysilane (TMOS), phenylmtrimethoxysilane (PTMS), diphenyldimethxysilane (DPDMS), and triphenylmethoxysilane (TPMS) in a counter diffusion technique (Ohta et al, 2008;Zhang et al, 2016). A SiO-CH 3 bond in methoxide groups reportedly decomposes more easily, and the intermediate of the precursors undergoes oligomerization to form silica networks, which is followed by an oxidation reaction.…”

“…When firing organosilica at higher temperatures, densification and decomposition of organic groups occurs simultaneously, which leads to a complicated process but allows additional Fig. 8 Gas permeance of TPMS-derived SiO 2 membranes prepared for different CVD time (Zhang et al, 2016) control of pore-size distribution (Lee et al, 2011). Plasma-enhanced chemical vapor deposition (PECVD) is commonly used to prepare thin films, and has been utilized in preparing silica membranes.…”

Synthesis of Silica Membranes by Chemical Vapor Deposition Using a Dimethyldimethoxysilane Precursor

“…The subject of silica membranes has been covered in recent reviews [1][2][3] and several recent papers [4][5][6][7][8]. Notable past work includes the original papers [9,10], the use of sol-gel techniques [11,12], chemical vapor deposition (CVD) [13,14] and plasma methods [15,16], the employment of diverse CVD precursors [17][18][19][20][21] and compositions [22][23][24], the determination of porosity [25], and the elucidation of the mechanism of permeation [26][27][28]. Important precedents are the use of dimethyldimethoxysilane (DMDMOS) [17] and other methyl-substituted siloxanes [29,30].…”

High‐temperature CO2 removal from CH4 using silica membrane: experimental and neural network modeling

“…Separation using a silica membrane is mainly based on a molecular sieving effect where the molecules pass through the small pores based on their kinetic diameter . Silica membranes with high combined values of flux and selectivity can be obtained through two methods of preparation, which are sol–gel technique and chemical vapor deposition . An alumina membrane prepared using the colloidal sol method is used as a support in the polymer sol route.…”

“…26,27 Silica membranes with high combined values of flux and selectivity can be obtained through two methods of preparation, which are sol-gel technique and chemical vapor deposition. [28][29][30] An alumina membrane prepared using the colloidal sol method is used as a support in the polymer sol route. The pore size in the polymer sol route is determined by the degree of branching of the inorganic polymer where a low degree of branching provides a narrower pore system.…”