Kinetics of Wet Oxidation of Formic Acid and Acetic Acid

Abstract

Oxidation of lower molecular weight carboxylic acids such as formic, acetic, glyoxalic, and oxalic acids is often the rate-controlling step during wet oxidation (WO) of an aqueous waste stream exhibiting very high chemical oxygen demand (COD). The kinetics of WO of formic acid was studied in the absence and presence of a cupric sulfate as catalyst in the temperature range 150−240 °C and oxygen partial pressure range 0.345−1.380 MPa. Wet oxidation of acetic acid was carried out in the presence of cupric sulfate in the temperature range 215−235 °C. Homogeneous copper sulfate was found to be a very good catalyst for oxidation of formic acid and acetic acid.

Kinetic modelling of catalytic wet air oxidation of phenol by simulated annealing

“…This is lower than that given for oxalic acid, being in contrast with the refractoriness noted by Shende and Levec [25] for non-catalytic WAO, although at temperatures and pressures higher than those studied here. Oxygen was found to have an order of 0.23 in the rate equation, being in disagreement with the first-order dependence observed by Baldi et al [43] and Shende and Mahajani [23]. Nonetheless, Baldi et al [43] carried out the reaction on a similar catalyst (CuO-ZnO) but at significantly higher temperatures (200-240 • C), while Shende and Mahajani [23] not only carried out the reaction at higher temperatures (150-240 • C), but also using a homogeneous CuSO 4 catalyst.…”

“…Oxygen was found to have an order of 0.23 in the rate equation, being in disagreement with the first-order dependence observed by Baldi et al [43] and Shende and Mahajani [23]. Nonetheless, Baldi et al [43] carried out the reaction on a similar catalyst (CuO-ZnO) but at significantly higher temperatures (200-240 • C), while Shende and Mahajani [23] not only carried out the reaction at higher temperatures (150-240 • C), but also using a homogeneous CuSO 4 catalyst. Acetic acid is considered as the most refractory of the carboxylic acids [44].…”

“…The very poor fitting obtained when checking kinetic networks not including a direct oxidation step from benzoquinones to oxalic and formic acid also supports this speculation. Finally, direct oxidation of acetic acid into carbon dioxide and water was not considered, as its reaction rate should be negligible at temperatures below 200 • C [23,24].…”

“…Only a few attempts have been made to give more detailed schemes based on lumping of partial oxidation products [11,18]. As well, the oxidation kinetics of low molecular weight acids have been investigated [22][23][24][25][26] but, though degradation schemes are proposed, only kinetic analysis for mother compound disappearance or lumped TOC reduction is given. However, the kinetic analysis accounting for all the intermediates is of interest from an environmental point of view, as some partial oxidation by-products are as toxic as phenol itself.…”

Fe salts as catalyst for the wet oxidation of o-chlorophenol

“…Among all the wet oxidation technologies, WAO, which can mineralise pollutants at elevated temperature and pressure, has the ability to convert most organic and inorganic compounds into end products such as minerals, carbon dioxide and water (Shende and Mahajani, 1997;Santos et al, 2001). WAO has been demonstrated as a viable process for o-chlorophenol wastewater treatment Lei and Wang, 2000).…”