Hopcalite catalysts

The heat of adsorption of 2-nitropropane is very high, so carbon-containing respirators should not be used in high vapour concentrations. Also, if Hopcalite catalyst (co-precipitated copper(II) oxide and manganese (IV) oxide) is present in the respirator cartridge, ignition may occur. 

Veprek, S., Cocke, D. L., Kehl, S. Oswald, H. R. 1986. Mechanism of the deactivation of Hopcalite catalysts studied by XPS, ISS and other techniques. Journal of Catalysis, 100, 250-263. 

The two catalysts reporetd here, both commercial VOC oxidation catalysts, are a cerium-promoted Hopcalite (Catalyst A), and a chromia/alumina (Catalyst B). catalyst B was designed primarialy for fluid-bed operation, but has been studied here in both fixed-and fluid-bed application. Catalyst A has been studied only in fixed-bed studies Further data on these materials, as well on the performance of a Pt/Ni/alumina catalyst, are given in [2]. 

The effect of temperature on the activity of the fresh catalysts was first studied. For the Hopcalite catalyst with feed A there was complete conversion above 300 °C. However, significant loss of activity was observed at lower temperatures, though activity could be restored by heating the catalyst above 300 °C. This is probably due to water vapor adsorption, given the known sensitivity of other Hopcalite formulations to water. There appears to be almost an on off switch for this material at 300 °C, but the long-term... 

A rather simple model can be developed to fit temperature-time data such as those of Figures 2 and 5, and to predict the total catalyst life. Consider the fixed-bed deactivation of the Hopcalite catalyst as an example. If ve assume that the deactivation rate is a function of current activity alone, then... 

Figure 7. comparison of temperature time data, Hopcalite catalyst, with equation (6). 

Figure 8 Simple parallel-consecutive reaction network describing the oxidation of VOCs by a supported hopcalite catalyst [86]...

Comparison of Noble Metal and Oxide Catalysts. - A few studies have directly compared the activity of noble metal and oxide based catalysts. The combustion of a range of C5-C9 hydrocarbon VOCs in humidified air by 0.1% Pt/3% Ni/Al203 and ceria promoted hopcalite commercial catalysts has been compared [96]. The Pt based catalyst showed no deactivation during 253 continuous operation, whilst over 297 days the temperature of hopcalite catalyst required an 85°C increase to maintain > 99% conversion. However, the final operating temperature of the hopcalite catalyst was 400°C, 30°C lower than the isothermal operating temperature of the Pt system. A first order concentration deactivation model was developed and predicted a 362 day lifetime for the... 

The other two forms of tritium gas usually are submitted on a palladium-coated molecular sieve collector. Any HT is converted to HTO by palladium-catalyzed oxidation in the collector the water is removed by heating it above its boiling point and condensing the vapor. The sorbent with the remaining organical-bound tritium is mixed with a Hopcalite catalyst and heated to 550°C to oxidize organic gases to water, which is distilled and condensed (Ostlund and Mason 1985). 

A catalyst that has been used effectively for oxidizing traces of acetylene in the air feed to low temperature separation plants and for providing hydrocarbon-free air for instruments and other special applications consists of a mixture of manganese dioxide and copper oxide, called Hopcalite. This catalyst also converts traces of carbon monoxide to carbon dioxide and u-aces of ozone to oxygen. The basic composition is about 60% manganese dioxide and 40% copper oxide however, relatively small additions of silver as a promoter have been found to make the catalyst particularly effective for most air streams (Rushton, 1954). Hie degree of conversion of several hydrocarbons over a commercial Hopcalite catalyst as a function of temperature is shown in Figure 13-10. 

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