Soil and Groundwater Pollution Technology Offers


The new mixed oxide catalyst of cerium-praseodymium (CexPr1-XO2) allow the efficient combustion of chlorinated volatile organic compounds (especially 1,2-dichloroethane). These new catalytic systems are able to work in gas streams at temperatures between 250-500 º C in an dynamic and continuous way without suffering a significant deactivation process. In recent years, environmental legislation has restricted the air emissions permissible levels, and particularly the emission of volatile organic compounds (VOCs) harmful for both the environment and human health There is a wide variety of VOCs, of different chemical nature (aliphatic, aromatic, oxygenated and halogenated compounds) and consequence of different emission sources (waste gases from chemical plants, soil and water decontamination, solvents evaporation , etc..), but 1,2-dichloroethane (DCE, C2H4Cl2) is the most lasting, dangerous and commonly used in industry (used, for example, massively in the process of polyvinyl chloride production and consequently chemical plants produce significant amounts of waste that require efficient treatment). Until a few years ago, VOCs were usually eliminated by thermal incineration. However, new legislation on VOC emissions has originated significant improvements on treatment technologies. This is the case of the catalytic oxidation that in recent years has shown its ability to destroy VOCs at temperatures below those used in thermal incineration and has also produced a significant reduction of secondary pollutants (nitrogen oxides). Currently, catalytic oxidation processes require heating large gas flows that contain a small amount of VOCs and put the gas in contact with solid catalysts that can either be • Those containing noble metals as active phase: they have a excellent oxidation efficiency, although their cost is very high and gradually lose their activity with the presence of chlorine in the reaction mixture. • Those containing transition metals: they have a lower cost and are more stable and durable, although less active than those containing noble metals.