A Japan-based research institute developed an energy-saving biobutanol refining technology that can collect butanol with a density of 80% by mass or higher from dilute 1-butanol solution (about 1 mass percent) by using a zeolitic separation membrane.
The technology was developed by the Research Institute for Innovation in Sustainable Chemistry (ISC) of Japan's National Institute of Advanced Industrial Science and Technology (AIST).
Like bioethanol, biobutanol is carbon neutral. But the calorific value of biobutanol is 34MJ/kg per volume, which is higher than that of ethanol (27MJ/kg per volume). Though bioethanol and biobutanol seem to have almost the same cost per calorific value, biobutanol has advantages in terms of conveyance, storage cost, design of fuel tank and so forth. Also, biobutanol is not easily mixed with water, which is a problem of ethanol.
Furthermore, main sugars that constitute cellulosic biomasses are C6 sugar and C5 sugar. But in ethanol fermentation using yeasts, C5 sugar is not used. On the other hand, butanol producing microorganisms can use C5 sugar, too, enabling more effective use of biomass.
This time, ISC optimized the synthesis condition and synthesized a silicalite separation membrane with a high alcohol permselectivity. By combining the membrane and a membrane isolation process (pervaporation), it became possible to collect high-density butanol from low-density butanol solution. Compared with a method using an existing separation membrane, the energy required to collect butanol is expected to decrease by 50-70%.
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