2,2,3,3,4,4,4-heptafluorobutyl acetate: Transesterification reaction of 2,2,3,3,4,4,4-heptafluoro-1-butanol and isopropyl acetate and side-product composition

As an investigation object, in the present work, the reactive distillation (RD) process based on the transesterification of isopropyl acetate and 2,2,3,3,4,4,4-heptafluorobutanol under acidic conditions is considered. The process is aimed at obtaining 2,2,3,3,4,4,4-heptafluorobutyl acetate (HFBA), which is used in the production of non-aqueous electrolytes, ethyllithium sulfate, charge retention medium, ultraviolet light-absorbing oligomers, etc. An important factor in the RD design is the selection of the proper process conditions, both in terms of the separation subsystem and the chemical constituent. This first requires a clear understanding of the mixture qualitative composition (including reaction side-product composition and their formation conditions) and the component distribution of the reaction mixture over the height of the column. The presence of alcohols (by-product—isopropanol (IPol)) in the system suggests their possible intermolecular dehydration (potentially, the formation of up to three ethers), and the acid residue—the appearance of acid and even anhydride (most unlikely). In the present work, the RD process was carried out in batch mode at atmospheric pressure, and the temperature of the reaction area varied from 95 to 105 ºC. The identification of by-products requires their significant amount in the reaction mixture. Thus, the process was carried out under «harsh» acidic conditions; H₂SO₄ was used as a catalyst (up to ≈0.2 mol. fr. in the reaction area). Through a combination of NMR spectroscopy (¹H and ¹⁹F) and GC-MS, it was determined that during the process, the following are primarily formed in the system: target HFBA (which, relative to other components of the system, is also a low-volatile component) and by-product IPol. As side-products were identified diisopropyl ether, acetic acid, water, and 2,2,3,3,4,4,4-heptafluorobutyl isopropyl ether (in the case of a batch process, the etherification reaction grows in influence during sulfuric acid concentration increasing in the reaction area). No bis(1H,1H-heptafluorobutyl)ether or acetic anhydride were identified in the system.