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Efficient Polymerization Inhibition Systems for Acrylic Acid Distillation: New Liquid-Phase Inhibitors

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journal contribution
posted on 14.03.2012, 00:00 authored by Jaroslav Mosnáček, Renaud Nicolaÿ, Kishore K. Kar, Stanley O. Fruchey, Michael D. Cloeter, Richard S. Harner, Krzysztof Matyjaszewski
Phenothiazine and other compounds with similar structures, namely, phenoxazine, promazine, promazine hydrochloride, N,N′-dimethylphenazine, carbazole, N-ethylcarbazole, N-benzylphenothiazine, and N-(1-phenylethyl)­phenothiazine were tested as liquid-phase inhibitors for acrylic acid. N-Alkylated phenothiazine (PTZ) derivatives, such as N-benzylphenothiazine and especially N-(1-phenylethyl)­phenothiazine, showed improved efficiency for liquid-phase inhibition, in comparison with PTZ. It was also shown that N-alkylated PTZ derivatives could be used in combination with nitroso compounds that can be employed as vapor-phase inhibitors. The combination of N-(1-phenylethyl)­phenothiazine and nitrosobenzene showed superior liquid-phase-inhibition efficiency, with time to gelation of >122 h, in comparison with 64 h obtained with PTZ alone. The structure of liquid-phase inhibitors had no influence on the extent of Michael addition reactions during heating of acrylic acid.