Triethyl Citrate Synthesis by Reactive Distillation

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• 作者：Aspi K. Kolah ; Navinchandra S. Asthana ; Dung T. Vu ; Carl T. Lira ; Dennis J. Miller
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2008
• 出版时间：February 20, 2008
• 年：2008
• 卷：47
• 期：4
• 页码：1017 - 1025
• 全文大小：138K
• 年卷期：v.47,no.4(February 20, 2008)
• ISSN：1520-5045

文摘

A continuous reactive distillation process is proposed for the synthesis of triethyl citrate from citric acid andethanol in the presence of macroporous Amberlyst 15 ion-exchange resin catalyst. The process design, developedusing ASPEN Plus simulation software, is based on laboratory kinetic and thermodynamic studies and pilot-scale reactive distillation experiments. Pilot-scale experiments were carried out in a 5-m glass reactive distillationcolumn; catalyst effectiveness was then determined from ASPEN Plus simulation of pilot-scale experimentsusing a user-written reaction kinetic module based on activity coefficients. Because citric acid esterificationkinetics are slow, complete conversion could not be obtained in the pilot-scale column. Using parametersdetermined from simulation of a pilot-scale column experiment, design of a reactive distillation column tocompletely convert citric acid to triethyl citrate was carried out. Optimum column performance occurs atlow reflux ratios (L/D < 0.1) to avoid water reintroduction and at moderately elevated pressure (2.5 bar) toincrease temperature and enhance kinetic rates without leading to product degradation. The effect ofethanol feed position and values of reflux and boilup ratios were also examined. A large number of reactivestages is required because of the slow reaction of diethyl citrate to triethyl citrate. As a final step, the designof a complete commercial-scale process to produce 25 million lbs/y triethyl citrate, with the reactive distillationcolumn as the core component, was carried out. Three different process schemes were examined. In thefirst scheme, only a reactive distillation column is used. The second uses a prereactor followed by areactive distillation column. In the third and preferred scheme, a prereactor followed by a simpledistillation column to remove water is placed ahead of the reactive distillation column. In each configuration,triethyl citrate product yield is maintained above 98.5 wt %, with the main byproduct being diethyl citrate.Comparison of stream compositions and equipment design parameters is provided for the three schemesconsidered.