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. 2019 Jul 17;9(7):86.
doi: 10.3390/membranes9070086.

Hydrophobic *BEA-Type Zeolite Membranes on Tubular Silica Supports for Alcohol/Water Separation by Pervaporation

Kyohei Ueno  1   2 , Saki Yamada  3 , Toshinari Watanabe  4 , Hideyuki Negishi  5 , Takuya Okuno  6 , Hiromasa Tawarayama  6 , Shinji Ishikawa  6 , Manabu Miyamoto  2 , Shigeyuki Uemiya  2 , Yasunori Oumi  7
Affiliations

Hydrophobic *BEA-Type Zeolite Membranes on Tubular Silica Supports for Alcohol/Water Separation by Pervaporation

Kyohei Ueno et al. Membranes (Basel). .

Abstract

Hydrophobic pure-silica *BEA-type zeolite membranes with large pores were prepared on tubular silica supports by hydrothermal synthesis using a secondary growth method and were applied to the separation of alcohol/water mixtures by pervaporation (PV), an alternative energy-efficient process for production of biofuels. Amorphous pure-silica tubular silica supports, free of Al atoms, were used for preparing the membranes. In this study, the effects of the synthesis conditions, such as the H2O/SiO2 and NH4F/SiO2 ratios in the synthetic gel, on the membrane formation process and separation performance were systematically investigated. The successfully prepared dense and continuous membranes exhibited alcohol selectivity and high flux for the separation of ethanol/water and butanol/water mixtures. The pure-silica *BEA membranes obtained under optimal conditions (0.08SiO2:0.5TEAOH:0.7NH4F:8H2O) showed high PV performance with a separation factor of 229 and a flux of 0.62 kg·m-2·h-1 for a 1 wt % n-butanol/water mixture at 318 K. This result was attributed to the hydrophobicity and large pore size of the pure-silica *BEA membrane. This was the first successful synthesis of hydrophobic large-pore zeolite membranes on tubular supports with alcohol selectivity, and the obtained results could provide new insights into the research on hydrophobic membranes with high permeability.

Keywords: *BEA-type zeolite; alcohol selectivity; butanol; electrophoretic deposition; ethanol; hydrophobic zeolite membrane; hydrothermal synthesis; pervaporation separation; secondary growth; tubular silica support.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
SEM images of seed crystals and particle size distributions derived from the SEM images (a,c) before and (b,d) after classification.
Figure 2
Figure 2
SEM images of the top surface of silica support (a) before and (b) after seeding.
Figure 3
Figure 3
X-ray diffraction (XRD) patterns of *BEA-type membranes prepared with different H2O/SiO2 ratios: (a) 8, (b) 40, (c) 100, and (d) 160.
Figure 4
Figure 4
Top (left) and cross-sectional (right) SEM images of *BEA-type membranes prepared with different H2O/SiO2 ratios: (a,b) 8, (c,d) 40, (e,f) 100, and (g,h) 160.
Figure 5
Figure 5
XRD patterns of *BEA-type membranes prepared with different NH4F/SiO2 ratios: (a) 5.63, (b) 6.25, (c) 7.50, and (d) 8.75.
Figure 6
Figure 6
Top (left) and cross-sectional (right) SEM images of *BEA-type membranes prepared with different NH4F/SiO2 ratios: (a,b) 6.25, (c,d) 7.50, and (e,f) 8.75.
Figure 7
Figure 7
Schematic of separation mechanism of hydrophobic *BEA membrane: (a) ethanol/water separation (ethanol molecule << *BEA pore) and (b) butanol/water separation (butanol molecule < *BEA pore).
See this image and copyright information in PMC

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