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Intensification of esterification process in TBP synthesis by in situ vapor stripping

Zhang, Yuqiang, Li, Jun, Jin, Yang, Chen, Ming, Yu, Defang
Journal of chemical technology and biotechnology 2019 v.94 no.5 pp. 1474-1479
Fourier transform infrared spectroscopy, butanol, byproducts, esterification, heavy metals, hydrochloric acid, metal ions, pentane, phosphates, temperature, vapors
BACKGROUND: Over the past few decades, tri‐n‐butyl phosphate (TBP) has been a widely used and irreplaceable extractant that can extract a variety of heavy metal ions and inorganic acids. The conventional process of tri‐n‐butyl phosphate synthesis has the problem of low yield. The in situ vapor stripping method was developed to intensify the tri‐n‐butyl phosphate synthesis reaction. RESULTS: In this work, the coupling process of in situ vapor stripping and reaction was proposed for the first time in the process of synthesis of TBP. It was found that the reaction of high concentration hydrogen chloride and 1‐butanol would produce water, which resulted in increasing the possibility of side reactions, especially when the temperature was higher than 55 °C. In the lower temperature range, n‐pentane was selected as the stripping medium, which effectively removed hydrogen chloride from the reaction system by in situ vapor stripping. The FT‐IR analysis confirmed that TBP can be synthesized successfully by the vapor stripping process. In addition, the effects of n‐pentane volume, temperature and stripping time on the yield of TBP and the amount of hydrogen chloride stripped were investigated. By applying the optimum reaction conditions, the yield of TBP was increased to 94%, larger than that of the current industrial process whose yield is only 80%. CONCLUSION: The in situ vapor stripping process is demonstrated to be an effective method for intensification of the esterification process in TBP synthesis. It can be used for other reactions which generate volatile gases as the byproduct. © 2018 Society of Chemical Industry