Evaluation of absorption and advanced oxidation processes to treat N-methyl-2-pyrrolidinone in an exhaust air stream.

摘要

N-methyl-2-pyrrolidinone (NMP) is a solvent which is being used in surface coating applications, cleaning, stripping and many other solvent processes. Its lower vapor pressure and lower toxicity made it an attractive alternative to the highly volatile chlorinated solvents which have been used for a variety of industrial applications in the past. This research was conducted to address and evaluate the removal efficiency of absorption and advanced oxidation technologies to remove and oxidize NMP from an exhaust air stream.;A simplified kinetics model combined with commercially available distillation software was used to predict the relative effects ozone concentration, hydrogen peroxide concentration, pH, and mass transfer processes in the absorption and oxidation of NMP in an exhaust air stream. A chemical mechanism for the hydroxyl radical oxidation of NMP was proposed. The research determined the relative effects of varying the concentrations of ozone and hydrogen peroxide, and the pH of the system. The optimum conditions for the oxidation of NMP using ozone and hydrogen peroxide were determined. These results were applied to the current commercial design of an air pollution control system to increase the oxidation of NMP in the system.;The addition of hydrogen peroxide and ozone to the scrubbing liquid oxidized NMP which had been absorbed into the liquid phase in a counter current packed bed scrubber. NMP reacted with the hydroxyl radical to form methylsuccinimide and 2-pyrrolidinone. Both methylsuccinimide and 2-pyrrolidinone reacted with the hydroxyl radical to form 2,5-pyrrolidinedione (succinimide). Atmospheric reactions between NMP and atmospheric oxidants would be expected to follow an oxidation mechanism similar to the proposed mechanism.;NMP in an exhaust air stream was removed to below detectable 1 PPM in a counter current packed bed scrubber. The current cost of producing high ozone concentrations and hydrogen peroxide is high relative to biological treatment. Advanced oxidation processes in combination with biological treatment should be explored as a potentially cost-effective treatment method for the scrubbing liquid prior to discharge or recycle of the scrubbing liquid.