Production of bio-plastics from organic acids derived from brown coal

点击翻译按钮获取中文摘要

Brown coals are abundant fossil resources, but they have not been utilized in a large amount because of their low calorific values. Condidering that brown coals consist of small aromatic ring structure and many functional groups, utilization methods reflecting the structure should be explored. On the other hand, the cost for producing bio-plastics is very high because raw materials are verr expensive. If bio-plastics can ve produced from a feedstock of low cost, they may be utilized widely as a environmentally benign material.From this viewpoint we have presented a new method to produce a feedstock for bio-plastics from brown coals under mild conditions. Several brown coals were oxidized in 30%-H_2O_2 aqueous solution at between 25 and 80ﾟC under atmospheric pressure. When an Australian brown coal was oxidized for 24h at 60ﾟC,80wt% of the coal decomposed to water soluble organics, 38% of which were, surprisingly, chemicals such as oxalic acid, formic acid, acetic acid, glycolic acid, and malonic acid.Next, poly hydroxyl butylic acid (a bio-plastics, PHB) was produced from these organic acids using Aladcligenes enthrophas. It was found that total concentration of organic acids should be kept less than 5 g/l in order to produce PHB in high yield. The yield of PHB reached 33% when only acetic acid was used as a feedstock. The reaction was controlled by NADPH produced from citric acid in TCA cycle. Malonic acid did not react at all, so it can be recovered in high selectivity from the mixture of the organic acids through producing PHB.Thus it was clarified that the proposed method is effective to produce bioplastics from brown coals.