**5. Conclusions**

Based on the process principle of reactive distillation, a mathematical model of reactive distillation process was established. The improved Inside–Out method was provided in this work for the solution of a reactive distillation process. In view of the nonlinear enhancement of the reactive distillation mathematical model and the di fficulty of convergence, the calculation of the *K* value of the approximate thermodynamic model was improved to simplify the calculation process. The initial value estimation method suitable for the calculation of reactive distillation was proposed, which increased the possibility of convergence.

The algorithm was verified by using an isopropyl acetate reactive distillation column and a depropanization column as examples. In Example 1, the reaction extent calculated by the initial value estimation method was close to the simulation results, it facilitated the convergence process of the solution algorithm. The simulation results obtained in this work were compared with Zhang et al. [6], presenting grea<sup>t</sup> agreemen<sup>t</sup> with the reference, only the relative deviation of the reboiler heat duty reached 2.57%. In Example 2, the simulation results of the depropanization column presented a good agreemen<sup>t</sup> with the measured value, except for the smaller composition value. The results showed that the improved Inside–Out method calculation results were accurate and reliable.

**Author Contributions:** Conceptualization, X.S.; Data curation, J.W.; Formal analysis, S.X.; Project administration, L.X.; Writing—original draft, L.W.;Writing—review & editing, L.W. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by Major Science and Technology Innovation Projects in Shandong Province, gran<sup>t</sup> number [2018CXGC1102]; and The APC was funded by the Science and Technology Department of Shandong Province.

**Conflicts of Interest:** The authors declare no conflict of interest.
