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

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.

Effect of the Formation of Ultrathin Selective Layers on the Structure and Performance of Thin-Film Composite Chitosan/PAN Membranes for Pervaporation Dehydration

“…Membrane processes are an alternative to traditional separation methods. Pervaporation is one of the most efficient membrane methods for the separation of low molecular weight liquid mixtures, which is widely used for the dehydration of alcohols and other organic substances [ 4 , 5 , 6 , 7 , 8 , 9 ] and characterized by high efficiency with low energy consumption, a compact equipment, environmental friendliness and the ability of the automation [ 10 ]. Pervaporation is also a promising and perspective technology for the separation of azeotropic mixtures without application of additional reagents.…”

“…Various polymeric and inorganic membranes have been developed for the pervaporation dehydration of alcohols [ 4 , 5 , 6 , 11 , 12 , 13 , 14 , 15 , 16 , 17 ]. Polymeric membranes are more attractive due to the fabrication simplicity, flexibility and cost-effectiveness compared to inorganic membranes.…”

Process Intensification in Bio-Ethanol Production–Recent Developments in Membrane Separation

“…The ethanol-selectivity can be enhanced by mixing hydrophobic fillers to the polymers (MMMs) [65,67,68]. Inorganic membranes, consisting of pure filler materials, in the table showed a higher ethanol-separation ability with higher flux [55][56][57]. Both silicalite and beta-zeolite membranes are types of zeolite membranes.…”

“…Several trays are required to concentrate, e.g., 10% ethanol to over 80%, by distillation. On the contrary, over 80% ethanol can be obtained after a single permeation through a hydrophobic membrane [55][56][57][58][59]. Membrane separation is not limited by the azeotrope.…”

Pervaporation Zeolite-Based Composite Membranes for Solvent Separations

“…With such a performance, these membranes are in fact promising candidates to recover bioethanol from fermentation stages. Unlike Ma’s investigation, Ueno et al obtained low permeation (0.62 kg m −2 h −1 ) but higher selectivity (β of 229) for butanol separation using BEA-type zeolite membranes [ 45 ]. Aiming at the recovery of n-butanol from diluted aqueous systems, Cheng et al [ 53 ] recently embedded ZSM-5 zeolite into polydimethylsiloxane (PDMS); these resulting mixed matrix membranes (loaded with 40 wt.% ZSM-5) showed an acceptable n-butanol separation (β of 77) and total flux of 0.11 kg m −2 h −1 , in which 0.062 kg m −2 h −1 corresponded to n-butanol when testing a 1.5 wt.% n-butanol solution (at 47 °C).…”