The inhibition of acrylic acid and acrylate ester polymerisation in a heterogeneously catalysed pilot-scale reactive distillation column

Due to a complex thermodynamic behavior and a high risk of polymerisation, the current production process for n-butyl acrylate is challenging and cost-intensive. The process intensification for the esterification reaction between acrylic acid and n-butanol to synthesise n-butyl acrylate in a reactive distillation column has not been studied much experimentally and is addressed in this paper. A main challenge that currently hinders the implementation of this promising process is the risk of polymerisation of acrylic acid and n-butyl acrylate. This article presents an experimental investigation of the inhibition period of acrylic acid and n-butyl acrylate polymerisation, which is dependent on the amount of inhibitor added, the temperature and the gas phase composition. Hydroquinone monomethyl ether and phenothiazine are the most common inhibitors and are hence used within this study. The liquid–liquid separation is also studied together with the experimental investigation of the inhibition period. Furthermore, the dilution of the inhibitor in a pilot-scale reactive distillation column is investigated together with the development of startup and shutdown procedures. The results of the experimental and theoretical investigations are used to develop a concept to avoid any polymerisation occurring in a pilot-scale reactive distillation column. This concept was used to successfully conduct a pilot-scale reactive distillation experiment.

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► Influence of atmosphere, temperature and inhibitor concentration on IP is shown.
► Investigation of influence of LLE and startup and shutdown period.
► Concept for polymerisation inhibition in RD columns is introduced.
► Successful implementation of concept validated by conducting an RD experiment.