Abstract
Acrylic acid is a major chemical intermediate used in the production of acrylate esters. The most popular route for the manufacture of ester grade acrylic acid is via propylene oxidation. In a typical process, chemical grade propylene is contacted with steam and air in a catalytic reactor train to produce the target compound with carbon dioxide and acetic acid as the major byproducts. Various catalytic systems exist, offering both high selectivity and conversion, and operation can be based on different reactor types and configurations. The highly exothermic nature of the reactions necessitates efficient removal of the reaction heat. In this work the rigorous simulation and optimization of a two-step multitubular oxidation reactor system for the production of acrylic acid was undertaken on the ASPEN Plus platform, with particular emphasis on minimizing energy requirements. In developing the model, several critical parameters were identified for proper representation of the reaction system in the sequential simulation platform. These included adjustments to the properties of molten salt thermal fluids for accurate determination of flow characteristics on the shell side, comprehensive and interactively coupled calculation of the overall heat transfer coefficient and the use of inert pre-heating and oxidation pre-heating zones at the front end on the propylene oxidation reactor tubes. The resultant model was successfully used to optimize for acrylic acid production with minimum energy input, demonstrating the applicability of digital twins for process analysis.
