Performance of erythorbic acid as an oxygen scavenger in salted fresh and degraded monoethylene glycol under a magnetic memory effect

Abstract

Studies show that erythorbic acid is an effective oxygen scavenger in the food industry, thereby suggesting its potential for use in monoethylene glycol (MEG) regeneration systems. However, its performance under magnetic memory effects has not been studied. This study was conducted with 85-vol.% fresh MEG (F-MEG) and degraded MEG (D-MEG) solutions, preadjusted to pH 9.0 and pretreated with a magnetic field (MF). Two oxygen concentrations,~7,000 and~1,000 ppb, high-salinity concentrations (HF-MEG and HD-MEG), and organic acids were also employed. The applied MF strength, generated by a cylindrical permanent magnet, was~0.65 T.The erythorbic acid scavenging performance was enhanced upon exposure of the HF-MEG solutions to an MF. Conversely, the magnetized salt-free D-MEG solutions displayed a lower scavenging performance than the nonmagnetized solutions: Oxygen removal was more effective in the D-MEG solutions than in the HF-MEG solutions, regardless of magnetization, due to formic acid formation during the thermal oxidization process. Furthermore, the magnetized HF-MEG solutions exhibited a progressive increase in pH over time, whereas the nonexposed and D-MEG solutions presented different responses. Iron ions, acting as metal catalysts, also affected the oxygen scavenging performance in the D-MEG tests. The results suggest that the erythorbic acid scavenging performance can be improved by promoting the forward reaction using an MF. In addition, in the presence of erythorbic acid and only under specific conditions, formic acid can be used as secondary oxygen scavenger in oil and gas industry. Stable alkaline conditions are also necessary to achieve better scavenging performance. These results can be attributed to the influence of the MF on the spin state mechanism, given that the electron spin dynamics are affected by the Zeeman effect.