(288g) Reliable Fabrication of Oriented Fe-MFI Membranes for Efficient Ethanol Recovery from its Dilute Aqueous Solution

The increased dependence on oil supplies from unstable countries and sensitive regions in the world have created a strong desire for the domestic production of alternative energies on a renewable stand [1]. Alternative energies including light-voltage, wind energy, biodiesel and bioethanol are being developed to replace fossil fuels worldwide. As a promising energy alternative for transportation, bioethanol is convenient to carry in place. Although there has been a furious debate on the production of bioethanol with corn-based feedstocks, the non corn-based bioethanol, predominantly produced from sugarcane or biomass such as corn kernels, switchgrass and perennial plants, can be converted from lignocellulose for global sustainability [2,3]. In recent years, major economies with a high demand of fossil fuels have set their own progressive goals to achieve an increasing proportion of biofuels in the energy system and reduce net greenhouse gas (GHG) emissions [4]. The required enzyme and energy to convert lignocellulose into fermentable sugars and the energy consumption to separate and purify ethanol from its dilute aqueous solution construct the main cost of the whole production process [5]. The cost for separating ethanol from its dilute aqueous solution can be substantially reduced by using membrane-based pervaporation processes either combined with distillation or not [6]. Nevertheless, the increase of separation factor with a relatively high permeation flux is desired to reduce the cost of ethanol recovery.

The Fe-MFI membranes were fabricated via the seeded growth method. The 1-3 micrometer-thick and preferentially b-oriented Fe-MFI membranes could be fabricated on alpha-alumina supported b-oriented seed layers. The preferentially b-oriented seed layer was synthesized using either the manual assembly method or the Langmuir-Blodgett technique. The preferentially b-oriented Fe-MFI membranes were formed under the induction of the seed layer without using a mesoporous intermediate layer and trimer-TPAOH. This could dramatically decrease the difficulties and costs for preparation of b-oriented MFI membranes. Furthermore, the 6-8 micrometer-thick and h0h-oriented Fe-MFI membranes were fabricated on randomly oriented seed layers. The fabrication of the two preferentially oriented Fe-MFI membranes with specific microstructures is highly reproducible.

A novel calcination method was proposed and developed to remove templates in the synthesized Fe-MFI membranes. The template removal was carried out at low-temperature conditions helped with catalytic decomposition of templates to keep the Fe-MFI membranes defect-free. Both UV-Raman and BET measurements were performed to demonstrate the efficiency of this low-temperature calcination method. At last, the pervaporation performance of the two oriented Fe-MFI membranes were checked with respect to ca. 5 wt.% ethanol aqueous solutions at feed temperatures from 30 to 60 °C. With respect to the fabricated Fe-MFI membranes of two microstructures, the separation factors ranged from 90 to over 500 could be achieved while keeping the permeation flux of ethanol relatively high.

Acknowledgements

This work was supported by the National Natural Science Foundation of China under three consecutive General-Program Grants (20476076, 20776100 and 21076154) and a Key-Program Grant (21136008).

References

[1] Koonin S. E. Getting serious about biofuels, Science 311 (2006) 435.

[2] Farrell A. E., Plevin R. J., Turner B. T., Jones A. D., O’Hare M., Kammen M. D. Ethanol can contribute to energy and environmental goals, Science 311 (2006) 506-508.

[3] Fairley P. Next generation biofuels, Nature 474 (2011) S2-S5.

[4] IEA Technology roadmap: biofuels for transport (2011), http://www.iea.org/publications/freepublications/publication/Biofuels_Roadmap.pdf

[5] Zhu J. Y., Zhuang X. S. Conceptual net energy output for biofuel production from lignocellulosic biomass through biorefining, Prog. Energ. Combust. 38 (2012) 583-598.

[6] Vane L. M. Separation technologies for the recovery and dehydration of alcohols from fermentation broths, Biofuels, Bioprod. Bioref. 2 (2008) 553-588.

[7] Nai S. F., Liu X. F., Liu W., Zhang B. Q. Ethanol recovery from its dilute aqueous solution using Fe-ZSM-5 membranes: Effect of defect size and surface hydrophobicity, Microporous Mesoporous Mater. 215 (2015) 46-50.