固体触媒を用いた動物油脂由来バイオディーゼル燃料製造の検討

摘要

現在，世界の一次エネルギー需要の約40%を石油が担ってrnいる。2006年の石油需要は世界で9千万バレル/dayであるrnが，国際エネルギー機関の試算では中国やインドなどの新興rn国を中心に毎年1.3%増加し，2030年には1億2千万バレル/rndayとなる見込みである。その一方で，可採年数は約50年とrn枯渇が危倶されている。%Biodiesel fuel (BDF) has attracted attention as an alternative fossil fuel. BDF comprises fatty acid methyl esters (FAME) produced generally from triacylglycerols (TG) in vegetable oils treated with methanol. In Europe, BDF is manufactured from virgin vegetable oils grown on vast farmlands, while in Japan, where cultivation areas are small, it is manufactured from used cooking oils. Used cooking oils in Japan partly come from animal fats, which produce free fatty acids (FFAs) upon degradation. FFAs react with an alkali hydroxide used as the catalyst, and the produced soap brings about decrease a BDF yield. Since a massive amount of waste water due to homogeneous alkali catalysis of alkali hydroxide dissolved in methanol is discharged from the producing process, the post-processing is required. Due to these limitations, the applicability of the anion exchange resins as alternatives to the alkali catalyst was examined. It was clarified that the anion exchange resin was activated by binding with methoxide ions, which are regenerated during transesterification, allowing for their reuse. Compared to the hydroxide-type resins that are deactivated by adsorption of FFAs generated during the reaction, the methoxide-type resins maintain their activity, as no FFA is generated. Such deactivation could be controlled by esterifying FFAs with cation exchange resins before transesterification.