Pervaporation of Butanol from their Aqueous Solution using a PDMS-Zeolite Composite Membrane

Abstract

− Pervaporation is known to be a low energy consumption process since it needs only an electric power to maintain the permeate side in vacuum. Also, the pervaporation is an environmentally clean technology because it does not use the third material such as an entrainer for either an azeotropic distillation or an extractive distillation. In this study, Silicalite-1 particles are hydrothermally synthesized and polydimethylsiloxane(PDMS)-zeolite composite membranes are prepared with a mixture of synthesized Silicalite-1 particles and PDMS-polymer. They are used to separate n-butanol from its aqueous solution. Pervaporation characteristics such as a permeation flux and a separation factor are investigated as a function of the feed concentration and the weight % of Silicalite-1 particles in the membrane. A 1,000 cm 3 aqueous solution containing butanol of low mole fraction such as order of 0.001 was used as a feed to the membrane cell while the pressure of the permeation side was kept about 0.2~0.3 torr. When the butanol concentration in the feed solution was 0.015 mole fraction, the flux of n-butanol significantly increased from 14.5 g/ m 2 /hr to 186.3 g/m 2 /hr as the Silicalite-1 content increased from 0 wt% to 10 wt%, indicating that the Silicalite-1 molecular sieve improved the membrane permselectivity from 4.8 to 11.8 due to its unique crystalline microporous structure and its strong hydrophobicity. Consequently, the concentration of n-butanol in the permeate substantially increased from 0.07 to 0.15 mole fraction. This composite membrane could be potentially appliable for separation of n-butanol from insitu fermentation broth where n-butanol is produced at a fairly low concentration of 0.015 mole fraction.

Preparation of Organic/Inorganic Siloxane Composite Membranes and Concentration of n-butanol from ABE Solution by Pervaporation

“…7(d)에 나타낸 결과 인 선택도의 경우 35.07로 21.96인 세라믹 지지체 복합막 보다 더 높 게 나타나는 것을 확인하였다. 이 결과는 PDMS-Zeolite 복합막을 이 용한 부탄올의 농축결과 보다 우수한 결과를 얻을 수 있었다[19].PDMS/γ-Al 2 O 3 /α-Al 2 O 3 막이 PDMS/PVDF 막 보다 높은 투과 플 럭스와 낮은 선택도를 나타낸 것은 투과성분과 막의 친화도로 설명 할 수 있다.일반적으로 탄소수가 많아질수록 비극성의 성질이 강해 지게 된다. 따라서 탄소수가 2개인 에탄올의 경우 극성을 나타내지 만 탄소수가 4개인 부탄올은 탄소수가 늘어나면서 비극성의 성질이 강해지게 된다.…”