Vol.:(0123456789) 1 3 Aerosol Science and Engineering https://doi.org/10.1007/s41810-019-00046-1 REVIEW A Review of Synthesis, Structure and Applications in Hopcalite Catalysts for Carbon Monoxide Oxidation Subhashish Dey 1  · Ganesh Chandra Dhal 1 Received: 11 April 2019 / Revised: 7 June 2019 / Accepted: 31 July 2019 © Institute of Earth Environment, Chinese Academy Sciences 2019 Abstract Carbon monoxide (CO) is a poisonous atmospheric pollutant. It highly afects human beings, plants, animals and environ- ment. Automobile exhaust is the largest source of CO emission in the environment. To control this automobile exhaust pollution, the catalytic converters are used. Many types of catalysts have been investigated for CO oxidation purposes, i.e., noble metal, base metal, rare earth, perovskite, spinel and mixed transient metal oxides. These catalysts are widely used in a catalytic converter. Among the various metal oxide catalysts, hopcalite (CuMnOx) is one of the most efcient catalysts for low-temperature CO oxidation. Hopcalite catalysts have been reported to be good from economical, thermal, activity, selectivity and availability points of view. The activity of hopcalite catalysts is strongly dependent on the surface area, crystallite size and binding energy of the catalysts. This study will provide a scientifc basis for designing future application of hopcalite catalysts for low-temperature CO oxidation. This manuscript provides a summary of published information regarding pure and substituted hopcalite catalyst, synthesis methods; properties and application for CO emissions control. A number of papers associated with CO oxidation over the hopcalite catalysts have been available, but no review papers appear in the literature that is dedicated to CO oxidation. Therefore, in an attempt to fll this gap, the present review updates and evaluates the progress and future scope of hopcalite catalyst for purifcation of exhaust gases. Keywords Carbon monoxide · Catalyst · Hopcalite · Preparation methods and applications 1 Introduction The increase in population has increased the numbers of vehicles presents on the roads and created a most signif- cant air pollution problem in the world. These air pollutants have harmful efects on all living beings. The emissions of pollutants are a by-product of the combustion of engine and evaporation of fuel (Air quality criteria for carbon monox- ide 1991). The major pollutant emissions from automobile exhaust are nitrogen oxide (NOx), unburned hydrocarbons (HC), carbon monoxide (CO) and particulate matter (PM). Out of all these pollutants, CO is one of the most poison- ous and also called the unnoticed poison of the twenty-frst century. The emissions from vehicles are usually the rea- son for 60% of CO produced in the environment (Automo- bile and carbon monoxide 2019). Carbon monoxide is a colorless, orderless and tasteless gas that is emitted from partial oxidation of carbon-containing fuels. It combines with hemoglobin present in blood cells and converted carboxyhemoglobin (CoHb), which reduces the oxygen- carrying capacity of the human body (Amin et al. 2012; Dey et al. 2017b, 2018). The harmful health efects of CO are headache, fatigue, seizure, coma, nausea, vomiting and even death. The global concentrations of CO range between 0.06 and 0.14 mg/m 3 (Hasunuma et al. 2014; Hoshyar et al. 2015). Diesel engines are widely used in heavy-duty vehicles because of improved fuel efciency and power yield com- pared to a petrol engine. In comparison to diesel engine, the petrol engine emits more CO into the environment as shown in Table 1 (Chhatwal et al. 1975; Cholakov 2010). In the current scenario, the fuel has been changed to CNG fuels to overcome this vehicular emission problem. The CO emission from CNG vehicles is two times lesser than from gasoline engine vehicles. The vehicle emissions depend on the vehi- cle design, maintenance, operation conditions, fuel composi- tion, etc. (Badr and Probert 1994; Behar et al. 2012). * Subhashish Dey subhasdey633@gmail.com 1 Department of Civil Engineering, IIT (BHU), Varanasi, India