发酵液中丁酸络合萃取分离条件的研究

Conditions of separating butyric acid from fermentation broth by complexation extraction

研究了络合萃取-反萃法从发酵液中分离丁酸的工艺条件。比较了不同萃取体系,在以三辛胺为萃取剂、正辛醇为稀释剂的萃取体系,三辛胺体积分数为40%,发酵液初始pH值为2—3,萃取相比(体积比)为0.3时,分配系数和萃取率均达到较高值,分别为13.91和80.67%。增大相比能进一步提高萃取率,但萃取剂使用量将增大。2级萃取能使丁酸萃取率由85.47%提高到96.39%。以0.8 mol/L NaOH为反萃剂,丁酸总收率为86.4%。该萃取体系再生性较好,使用5次后萃取效率未见明显降低。该体系对丁酸选择性较高,适于在较低的操作成本下高效提取丁酸,同时实现丁酸和乙酸的有效分离,具有较好的工业应用前景。

The process conditions of complexation extraction-back-extraction for separating butyric acid from the fermentation broth were investigated. Various types of extraction systems were compared, with trioctylamine （TOA） and n-octyl alcohol as extractant and diluent respectively. The effects of TOA volume fraction, initial pH of fermentation broth and extraction phase ratio on distribution coefficient and extraction yield were studied. The distribution coefficient and extraction yield are 13.91 and 80.67% respectively under the optimum conditions of TOA volume fraction 40%, fermentation broth pH 2-3 and extraction phase ratio 0.3. The extraction yield can be enhanced from 85.47% to 96.39% by adopting a two-stage extraction. The further study shows that the overall yield of butyric acid can reach as high as 86.4% with 0.8 mol/L of NaOH as stripping solution. The extractant selected can be regenerated well because the extraction efficiency doesn＇t decrease evidently after 5 cycles. This process for butyric acid separation has a promising prospect in practical applications and many advantages of high selectivity, low cost, efficient separation of butyric acid and acetic acid and good regeneration ability.