Molecular sieve dehydration: a major development in the field of ethanol dehydration to produce fuel ethanol

Gasohol, a blend of ethanol and gasoline is a promising alternative to gasoline and has a great potential to come up as an environmentally clean fuel. Though anhydrous ethanol has various advantages, its generation is quite a difficult and costly task. The energy intensive technology ultimately results in an increased per liter production cost of bioethanol. Though the technology is costly, it is not capable of producing purely anhydrous ethanol. To be competitive, and find technical, economic acceptance, the cost for conversion of biomass to bioethanol must be lower than current gasoline prices. In this paper, a detail study of hybrid process that is capable producing an anhydrous ethanol of concentration more that 99.80% (w/w) is presented. It is well known that distillation alone cannot concentrate ethanol beyond its azeotropic point and finds economical acceptance up to 95% (w/w) ethanol only. On contrary, molecular sieves are able to concentrate ethanol to completely anhydrous state but finds economical acceptance for short span of 93–99.80% (w/w) ethanol. Complete dehydration by molecular sieves is never advisable. Therefore a new technology representing combination of simple distillation and molecular sieve dehydration is proposed. Paper also covers the critical review of different separation techniques available for dehydration of ethanol.