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A review of catalytic oxidation of carbon monoxide over different catalysts with an emphasis on hopcalite catalysts
Carbon monoxide (CO) is a dangerous poisonous air pollutant that greatly affects humans, plants, animals, and the environment. It is largely present in industrial flue gas, automobile exhaust gas, heavy traffic congestion, residences where wood is burned indoors, and natural sources like forest fires. To control it, a catalytic converter is mainly used for CO oxidation that is a feasible technology for the removal of CO. A wide variety of catalysts are used in catalytic converters, such as those based on noble metals, base metals, perovskite, spinel, hopcalite, and monel, among which hopcalite (CuMnOx) catalysts are economical, and show good thermal activity, selectivity and availability for low-temperature CO oxidation. A hopcalite catalyst is prepared by different methods, and preparation parameters such as shaking temperature and pH (8–11.5) have an impact on its activity. This article focuses on summarizing the reaction process of hopcalite catalysts in CO catalytic oxidation and the key factors influencing their activity as follows: appropriate promotors, supports, pre-treatment, and advanced preparation methods in the activity of a hopcalite catalyst toward CO oxidation. CO conversion was considerably higher than 100% at low temperature 50–125 °C with extra O2 in the feed gas. In fact, hopcalite is known to be an easily available and highly active catalyst for the low-temperature (25 °C) low-cost, complete oxidation of CO. Promoters, supports, pre-treatment, and advanced preparation methods have been added to improve the activity and stability of a hopcalite catalyst in CO oxidation. Also, deactivation generally occurs here via the hopcalite catalyst undergoing sintering and fouling during CO oxidation. A change in the hopcalite catalyst might result in an improvement in its overall performance in converters in the future.
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