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

Abstract

Nitroso compounds, such as 2-methyl-2-nitrosopropane, nitrosobenzene, and 4-nitrosophenol, were tested as volatile inhibitors for vapor-phase inhibition of acrylic acid polymerization during its reflux at 113 °C under reduced pressure. The experimental parameters were set to mimic the conditions employed for the industrial distillation of acrylic acid. Nitrosobenzene was found to be the most efficient vapor-phase inhibitor for the distillation of acrylic acid. The inhibition time was also found to be dependent on the pressure used for the experiments. Decreasing the pressure from 110 to 85 mbar resulted in an almost 2-fold increase in the inhibition time. The combination of nitrosobenzene with a liquid-phase inhibitor, namely, 4-hydroxy-2,2,6,6-tetramethylpiperidine 1-oxyl, significantly improved the efficiency of vapor-phase inhibition by decreasing the consumption of nitrosobenzene in the liquid phase.

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

“…A mixture of 100 ppm of TEMPOL, 100 ppm of nitrosobenzene, and 10 ppm of manganese acetate tetrahydrate was tested in the liquid phase at 113 °C under the same conditions as those used for the previous tests (Table ). It is worth mentioning that this combination was found to be an efficient vapor-phase-inhibition system for AA distillation . As shown in Table , the average time to gelation for this combination of inhibitors was 116 h in the liquid-phase tests.…”

“…It is worth mentioning that this combination was found to be an efficient vapor-phase-inhibition system for AA distillation. 11 As shown in Table 2, the average time to gelation for this combination of inhibitors was 116 h in the liquid-phase tests. This is lower than the 122 h obtained with 8.…”

“…Recently, we found nitrosobenzene to be a very effective inhibitor in the vapor phase during AA distillation. 11 On the other hand, it was also shown that the inhibition efficiency in both the liquid and vapor phases was poor when nitrosobenzene was used in combination with some standard liquid inhibitors, such as PTZ. This decrease in the inhibition efficiency was caused by side reactions between PTZ and nitroxyl radicals, formed in situ from nitrosobenzene, leading to the formation of hydroxylamine and green oxidation products from the reaction with PTZ.…”

“…However, such a combination of inhibitors can have an antagonistic inhibition effect, for example, because of side reactions between the inhibitors. Recently, we found nitrosobenzene to be a very effective inhibitor in the vapor phase during AA distillation . On the other hand, it was also shown that the inhibition efficiency in both the liquid and vapor phases was poor when nitrosobenzene was used in combination with some standard liquid inhibitors, such as PTZ.…”

Polymerization and Applications of Poly(methyl methacrylate)–Graphene Oxide Nanocomposites: A Review

“…Hydroquinone has significant advantages in the polymerization of acrylic polymers as opposed to other types of inhibitors due to its versatility including nontoxic, effective use in ambient and elevated polymerization environments, and ease in control during the reaction. Other than hydroquinone, nitroso-based compounds such as 2-methyl-2-nitrosopropane and nitrosobenzene are utilized as inhibitors for acrylic polymers . Nevertheless, these compounds need a more critical temperature and pressure control to obtain a successful polymerization process.…”