Catalytic incineration of volatile organic compounds

Volatile organic compounds (VOCs) make up a major class of air pollutants. This class includes pure hydrocarbons, partially oxidized hydrocarbons (organic acids, aldehydes, ketone), as well as organics containing chlorine, sulfur, nitrogen, or other elements. These compounds are usually found in most manufacturing processes, either for the raw materials, intermediates, or the finished products. Organic materials are present as chemicals, solvents, release agents, coatings, decomposition products, pigments, and so on that eventually must be disposed. Catalytic incineration is a well known process to destruct VOC emissions in air at low energy cost; it is useful when these contaminants are toxic and malodorous. The advantages of catalytic oxidation can be important mainly because of potential savings following the lower temperatures required. The environmental impact can be improved because both higher efficiency of abatement and lower levels of NO_x and CO₂ emissions can be reached. Furthermore the small pressure drops make the process very attractive. This article aims to show and discuss the results from continuous tests conducted in the laboratory scale reactors. Measurements of the abatement in the simulated industrial conditions, the assessment of the catalyst aging, and the identification of the possible poisoning will be shown. The catalyst powders were prepared by the incipient wetness impregnation method with aqueous solutions of metal nitrate and calcined at proper temperatures. The finished catalysts were characterized first by DTA-TGA. The effects of operating parameters, such as inlet temperature, space velocity, VOCs inlet concentration, and oxygen concentration on the catalytic incineration of VOCs over the catalysts were then performed. The activity of the catalyst decreased significantly with time while VOCs incineration was operated under a low temperature. However, the activity of the catalyst did not change much while the operating temperature was high. The catalysts were characterized by the surface and pore size analysis, XRD, XPS, EDS and SEM before and after the tests. Three kinetic models (i.e., the power-rate law, the Mars and Van Krevelen model, and the Langmuir-Hinshelwood model) were used to analyze the results. A differential reactor design was used for best fit of kinetic models in this study.