Separation of benzoic acid residue by flash-vacuum distillation-melt crystallization |
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| Authors: | Jiao Xu Weijiang Zhang Tao Yang Shujun Jiao Xuedong Hu |
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| Institution: | 1. Chemical Engineering Research Center, Tianjin University, Tianjin 300072, China
2. Hebei Tongyuan Material Circulation Company Limited, Shijiazhuang 050032, China |
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| Abstract: | A large amount of residue including benzoic acid, benzyl benzoate and fluorenone can form in the production of benzoic acid
by oxidizing toluene. To recycle the resources and reduce secondary pollution, the treatment of benzoic acid residue was carried
out to obtain the three purified materials by flash-vacuum distillation combination method, and the influence of the operating
parameters, such as the top pressure, reflux ratio and top and bottom temperatures was investigated to obtain the best operating
conditions. The experimental results show that the benzoic acid purity can reach 97% through distillation under the following
conditions: the top pressure is 1 600 Pa, the bottom temperature is 190–200 °C, the top temperature is 130–135 °C, and reflux
ratio is 5:1. The best operating conditions for benzyl benzoate distillation column are: the top pressure is 400 Pa, bottom
temperature is 250–260 °C, the top temperature is 150–160 °C, and reflux ratio is 5:1. The benzyl benzoate purity can reach
95% and the fluorenone purity can reach 92%. When refined by melt crystallization, the benzoic acid purity can be improved
up to 99.6%, and the purities of benzyl benzoate and fluorenone are both above 95%. |
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| Keywords: | benzoic acid residue benzoic acid benzyl benzoate fluorenone flash-vacuum distillation melt-crystallization |
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