Talk-Polywell.org

"We have developed an energy-saving technology for purifying biobutanol. It uses a kind of zeolite membrane and can recover concentrated 1-butanol (hereinafter referred to as butanol) of at least 80 wt% from dilute (about 1 wt%) aqueous butanol solution."

http://www.aist.go.jp/aist_e/aist_today ... ne_18.html