Modification of Natural Zeolite into Molecular Sieve Material and Its Application in Bioethanol Dehydration.

Abstract

Bioethanol dehydration process carried out using modified zeolites. Modifications made to improve the physical properties of natural zeolites, including pore size, chemical composition, and the ratio of Si/Al, so that the hydrophilic and become more effective in water adsorption. The objective of this study was to examine the methods in the modification of natural zeolite structure to obtain suitable characteristics for bioethanol dehydration, to get the best conditions of bioethanol dehydration, and to know the grades increase of bioethanol and adsorption capacity for each sample of modified zeolites. The natural zeolites were modified through hydrothermal synthesis at the temperature of 95 - 100o C, while the bioethanol dehydration process was carried out using a distillation system and batch adsorption. The modified zeolites mostly turned into zeolite type A in the form of sodium aluminosilicate. Zeolite samples leading to the structure of zeolite NaA were ZAM2, ZAM3, ZAM5 and ZAM6. The content of ethanol in bioethanol increased after the adsorption process of each zeolite sample. The ability of modified natural zeolites (ZAM2 and ZAM5) to increase the grade of bioethanol was better compared with that of purely natural zeolites (without modification), and this was also the case with their capacity of water adsorption in the bioethanol sample. The increased percentages of bioethanol grades in the immersion method using ZAM2 and ZAM5 with bioethanol of 90% were respectively 1.22% and 1.38%, while with bioethanol of 95% the percentages were 1.27% and 1.08%. Meanwhile, the resulted levels of bioethanol using purely natural zeolites with bioethanol of 90% and 95% were respectively 0.62% and 0.72%. The maximum capacity of adsorption was 17.67% for ZAM5 in the immersion with bioethanol of 90% for 24 hours. In general, the grade of ethanol increased after the adsorption process that uses all the modified zeolite samples.

Bioetanol adalah etanol yang dihasilkan dari fermentasi glukosa (gula). Bioetanol yang dihasilkan sangat tidak murni, sehingga memerlukan pengolahan lebih lanjut (Clark 2007). Jika bioetanol ingin digunakan sebagai bahan bakar (biofuel) perlu dimurnikan hingga mencapai 99% yang lazim disebut fuel grade ethanol (FGE). Bioetanol sebagai campuran bahan bakar harus betul-betul kering (anhidrat) supaya tidak korosif. Jika bioetanol masih mengandung air sebesar 4 – 5% akan mempengaruhi kinerja mesin dan dapat menyebabkan terjadinya korosi. Proses dehidrasi dilakukan untuk memperoleh etanol dengan kadar lebih besar dari 99%.