CATALYTIC WET AIR OXIDATION OF CARBOXYLIC ACID

Abstract

Today, the survival of process industries is increasingly dependent upon the environmental sustainability of their technologies. There is growing concern about the problems of waste minimization. Waste streams from various industries constitute high BOD, COD, pH, temperature, color, obnoxious odors. Rising concern about environment, strict implementation of environmental norms and the need to survive in competitive green pollution free market are slowly forcing the industries to upgrade and improve the waste minimization and treatment techniques. Among the various types of processes which can be used for treating aqueous wastes polluted with organic matter, wet air oxidation (WAO) is very attractive. The basic idea of the process is to enhance contact between molecular oxygen and organic matter to be oxidized. High temperature conditions convert the organic matter to carbon dioxide and water. The liquid phase is maintained by high pressure which also increases the concentration of dissolved oxygen and thus the oxidation rate. In this process insoluble organic matter is converted to simpler soluble organic compounds which are I turn oxidized to carbon dioxide and water without emissions of NON, SO2, Hcl, dioxins, furans, fly ash etc. the last residual organic compounds are fatty acids, espedially acetic acid. In the present work, CWAO of carboxylic acid,( acrylic acid) was carried out in a pressurized reactor at a partial pressure of air 4 kg/cm2 and temperature from 140°C to 180°C to reduce the COD of acrylic acid. The catalysts tested in CWAO of acrylic acid include both homogeneous (CuSO4 and FeSO4) and heterogeneous [Co: Bi (5:1) and Mn: Ce (1:1)1 catalysts. The characterization of catalysts by SEM and XRD proves that heterogeneous catalysts are far better than homogeneous catalysts. Among the four catalysts tested Mn: Ce (1:1) (5gm/L) found to be the best with almost 82% COD reduction at 180°C and partial pressure of air 4 kg/cm2 in 4hrs reaction time. These results agreed with the literature sited in the past.