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Respiratory Protection
Published in John F. Rekus, Complete Confined Spaces Handbook, 2018
Catalysis is a process that employs catalysts which are substances which influence the rate of chemical reaction without themselves entering into the reaction. A catalyst used for respiratory protection is Hopcalite, which is a mixture of copper and manganese oxides that accelerates the reaction between carbon monoxide and oxygen to form carbon dioxide.
Carbon Monoxide
Published in Béla G. Lipták, Analytical Instrumentation, 2018
The catalyst Hopcalite will oxidize carbon monoxide to carbon dioxide.1 The resultant temperature rise may be recorded continuously as a measure of carbon monoxide concentration. The catalyst temperature and residence times must be controlled to avoid interference by hydrocarbons. The method is not suitable for most air monitoring applications because of low sensitivity.
Air Purification
Published in O. Nelson Gary, Gas Mixtures, 2018
Carbon monoxide is relatively unaffected by its passage through soda lime, activated carbon, or any of the previously described desiccants. Special materials must be used for its removal. Hopcalite, a mixture of copper and manganese oxides, has traditionally been the most practical agent for removing carbon monoxide. It operates as a catalytic oxidizing agent, converting the carbon monoxide to carbon dioxide. The main requirement for using Hopcalite is that it be kept scrupulously dry, for it loses its catalytic ability in the presence of water. Currently, other Zeolite-type materials are being developed that will also catalytically remove carbon monoxide in humid gas streams.
Low-cost nanostructured Fe2O3-based composite catalysts synthesized by mechanical milling for CO oxidation reaction
Published in Chemical Engineering Communications, 2018
M. Alizadeh, S. A. Hosseini, S. M. M. Nouri, Z. Khalighi, B. Delfarah
Oxidation catalysts have been widely used for the removal of carbon monoxide and volatile hydrocarbons, especially in the catalytic convertors of automobiles and industrial stack plants (Bukhtiyarova et al., 2010; Dumitru et al., 2013; Tong et al., 2009; Urdă et al., 2009). Precious group metals such as platinum, palladium, and rhodium have shown great performance in those applications. However, due to their costs and raising some environmental issues, extensive research has been conducted to find low-cost replacement materials for oxidation reaction catalysts (Prasad and Singh, 2012; Royer et al., 2014; Seyfi et al., 2009; Zhang et al., 2011). Mixed metal oxide compounds such as hopcalite (CuMn2O3) are traditionally well known as CO oxidation catalysts. Recently, researchers have acknowledged different stable metallic oxide catalysts at nanoscale due to their good performance and low cost (Prasad and Singh, 2012; Royer and Duprez, 2011). Among them, iron oxide (Fe2O3) is a noteworthy catalyst because of its low cost and availability. However, the nanostructured iron oxide shows low activity below 300°C (Hosseini and Alizadeh, 2010; Khedr et al., 2006; Kwon et al., 2007). Several methods could be applied to increase the activity of the catalysts and reduce the activation energy of the CO to CO2 oxidation reaction. One method is combining oxide components with active metals such as gold, platinum, and silver. Several composite catalysts, e.g., Au/Fe2O3, Ag/Fe2O3, and Pd/Fe2O3 were prepared and examined for the conversion of CO to CO2 (Al-Sayari et al., 2007; Jiang and Yu, 2009; Narasimharao et al., 2015). The other effective method is to make a composite of two or more metallic oxides. In this context, some studies were conducted on making a composite of iron oxide with other oxides such as cobalt oxide and copper oxide, which have a high level of activity. In most related studies, chemical coprecipitation methods, which are relatively expensive methods, are used to prepare the composite catalysts (Biabani-Ravandi et al., 2013a, 2013b; Cao et al., 2008; Cheng et al., 2007). In the current research, a low-cost nanostructured iron oxide powder, which is a byproduct of the steel company, is applied as the base compound for CO oxidation catalysts. The effect of mechanical milling as one of the most facile methods for the activation of the catalysts is investigated. Also, the composite oxide catalyst powders were synthesized by mechanical milling and their catalytic behaviors for CO oxidation reaction were studied.