Extraction Of Bio-based 1,3-propanediol And Design Of Extractor

1,3-Propanediol(1,3-PD) has been widely applied in many areas as a high-valued bulk chemical. The properties of PTT synthesized by 1,3-propanediol and terephthalic acid are much better than other polyester material. However the high price of 1,3-PD is the main obstacle for widespread use, what’s more, the cost of separation process constitutes of a large amount of total cost. Biosynthesis method has problems that there are more complex impurities in fermentation broth and will be difficult for subsequent separation. So it is very important to develop new separation methods that have good separation efficiencies.In order to solve the problems of bio-based 1,3-propanediol separation, in this paper, ethanol-acetone two-step precipitation and sugaring-out extraction were proposed. The salting-out extraction dynamics and design of extractor were also carried out. Main research achievements are organized as follows.First, a new technology of ethanol-acetone two-step precipitation was developed. The bacteria cells in the fermentation broth were removed by microfiltration-ultrafiltration and then the fermentation broth was distilled to remove the water. Ethanol precipitation was firstly conducted with the optimal ratio of 2:1 (mass ratio of ethanol to condensed broth). And acetone precipitation was then carried out with the optimal ratio of 5:1 (mass ratio of acetone to condensed broth) after the ethanol was recovered by reduced pressure distillation. Lastly, the crude 1,3-PD was obtained by distillation and rectification. With this method, the recovery of 1,3-PD was 94.3%, the removal rate of proteins and salts was 98.36% and 90.16%. In addition, I focused on the organic acid and inorganic salt ions precipitation respectively by two-step precipitation and found that ethanol precipitation has better performance for formic acid and succinic acid, while the acetone precipitation has better performance for formic acid, succinic acid and citric acid with the removal rate of 95.79%,80.0% and 85.03% respectively. Even though the two-step precipitation has some ability to remove lactic acid, the residual rate of lactic acid was 75.06% because of its high concentration in fermentation broth. On the side of inorganic salt ions precipitation, the removal rates of Na+and SO42- were 50.04% and 17.4% by ethanol precipitation while the removal rates of SO4 PO4 Ca,K,Mg were all above 90%.Next, sugaring-out extraction was used to separate 1,3-PD from fermentation broths.Glucose/n-propano 1 was selected as the study object from six sugaring-out separation systems.Under the optimum condition, the recovery of 1,3-PD is 82%, the removal rate of salts,proteins and bacterial cells were 99.7%, 70% and above 99% respectively. I also investigated the effects of six inorganic salts on sugaring-out separation and found that the effects of sugaring-out separation improved significantly when added a small amount of inorganic salt.Adding (NH4)2SO4 (5%, w/w) into the glucose/n-propanol sugaring-out separation system can increase the 1,3-PD recovery by 90.64%. The recoveried glucose in heavy phase that had removed n-propanol was diluted to 50,100,150g/L and used in strain cultivating for 12h, the OD6oonm was 5.8,4.2 and 2.3 respectively. Using the recoveried glucose (60g/L) in preparation fermentation medium at the glycerol concentration of 40g/L, the concentration of 1,3-PD and 2,3-butanediol was 15.8g/L and 18.8g/L at 48h of the fermentation. The advantage of this sugaring-out separation method is that it can couple the separation with the fermentation and realize the rationalization of resources.Lastly, the off-line monitoring method, on-line monitoring method by ultraviolet-visible spectrophotometer (UV-Vis) and in situ on-line monitoring method by infrared absorption spectrum (ReactIR) were used to discuss the extraction dynamics of six salting- out separation systems, and the extractor was then designed according to the result of extraction dynamics. The study on extraction dynamics showed that the extractor with height-diameter ratio of 1 is better applied to salting-out extraction, also showed that the distribution equilibrate as the phase separation equilibrate. The static mixer of the extractor was selected as the cascade of three SK-10/20 type static mixers. Their performance should be verified in practical applications.