Summary of the technology
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.
Description of the technology
The Carbonaceous Materials and Environment research group at the University of Alicante has developed a new catalyst that can efficiently remove chlorinated volatile organic compounds (particularly toxic 1,2-dichloroethane, widely used in various industrial processes) in gas streams at operating temperatures between 250-500 º C. These new catalysts (mixed oxides of cerium-praseodymium) have a low cost and both very active and stable, because they do not go through a significant deactivation process (unlike the catalysts commonly used at present). Consequently this is a novel technology suitable for the international market. The research group is looking for companies interested in acquiring this technology for its commercial development.
In order to solve the above mentioned limitations, we are introducing a new catalyst based on cerium and praseodymium mixed oxides which allows an efficient control of chlorinated VOCs emissions, especially 1,2-dichloroethane (DCE, C2H4Cl2) present in the gaseous emissions from chemical plants, emissions with high stability and toxicity. Many of the catalysts used in the combustion of VOCs, when used to remove chlorinated organic compounds are deactivated in a short time due to chlorine poisoning by chlorine, and therefore stop working. Consequently there is a need for durable catalysts, in time and use, that allow the destruction of volatile organochlorine. In this sense, we have developed a new catalyst was developed that accelerates the burning of chorinated volatile organic compounds, whose generic formula is: CexPr1-xO2 (where 0 ≤ x ≤ 1) This type of catalysts are prepared by dissolving in water the corresponding precursors and precipitating / coprecipiting the corresponding hydroxides. They are then filtered, dried and burned. Once carried out the catalytic combustion tests, results have been checked by DRX, Raman Spectroscopy and XPS. Our conclusions are as follows: • All fresh catalysts have a fluorite-type structure. • After the catalytic tests, catalysts with an important cerium content keep their fluorite type structure, while those containing a high percentage of praseodymium, undergo a transformation phase to tetragonal structure. • Those catalysts rich in cerium suffer a slight chlorination, while those the rich in praseodymium undergo a chlorination both in surface and mass. • The mixed oxide catalysts CexPr1-XO2 have a high activity to accelerate the burning of chlorinated volatile organic compounds. • The stability of the catalysts depends on the composition of the mixed oxide used.
Main advantages of its use
- This novel catalytic system imply many advantages in relation to other similar products available in the market. Its main advantages are:• Highly efficient catalyst in the combustion of chlorinated volatile organic compounds (especially for in the case of the toxic and stable 1,2-dichloroethane).• High stability and durability in the reaction process• Low manufacturing cost• High efficiency: a small quantity of catalists require• It does not produce secondary pollutants (nitrogen oxides)• It allows the treatment of gaseous streams at low temperature (between 250-500 º C).
- This innovative and stable catalytic system for the efficient combustion of volatile organochlorine compounds (especially of 1, 2-dichloroethane) has a higly efficient performance in the control of pollutant emissions in the following industrial sectors:• Production of polyvinyl chloride (PVC).• Cleaning of textiles.• Cleaning of metal parts.• Dispersion of plastics and elastomers.• Paints• Enamels and varnishes.• Waste gases from chemical plants.• Processes of evaporation of solvents.• Decontamination of soils and waters.