Hopcalite catalyst activity

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... 

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 high activity that supported gold catalysts have shown for CO oxidation at ambient temperature makes them ideal candidates for use as respiratory protectors. A copper manganese oxide, Hopcalite, has been used for many years to remove CO in toxic environments. Thus, supported gold catalysts may be chosen in the future. 

A 10 Ndm3 min-1 feed composed of 75.0% H2, 0.7% CO and balance C02 with air for oxidation was fed into the relatively large test reactor carrying 230 cm3 catalyst microsperes of 1 mm diameter. Of the non-precious metal catalysts, that composed of hopcalite showed the highest activity, achieving almost full conversion in the temperature range 130-160 °C. The minimum CO output achieved was 40 ppm. A minimum 02/CO ratio of 2.5 was determined for this catalyst to achieve a carbon monoxide conversion exceeding 90%. The catalysts tested are summarized in Table 2.7. 

Case histories for the deactivation of commercial Hopcalite and chhromia/alumina catalysts in the oxidation of volatile organic compounds (V0C) are presented. Feeds of pure hydrocarbons, chloro-carbons, and mixtures of the two are considered. Both fixed- and fluid-bed configurations have been studied. Deactivation with mixed feeds is a severe test of V0C catalyst capabilities. There seems here no clear distinction between between the type of reactor, but significant differences between activity and selectivity do exist. A simple model for predicting fixed-bed operation is presented. 

In the intervening period between the end of World War I and the beginning of World War II, the catalytic properties of this remarkable class of catalysts was improved by the efforts of Frazer and his co-workers (22,49). Notwithstanding the large amount of research work carried out by numerous other investigators attracted to this field by the unique properties of the hopcalite, no other catalyst was discovered which could approach the activity and utility of the hopcalites in technical applications. 

Hopcalite, manufactured by the Mine Safety Appliances Co., has been found to be an excellent catalyst for this purpose it is a mixture of sintered metallic oxides. In a preliminary series of experiments, the catalyst qualitatively decomposed 90 p.p.m. of ozone in an air stream, and its activity remained unchanged after 100 hours of operation, when the experiment was discontinued. 

The industrial catalysts currently used for CO oxidation are Hopcalite (mainly MnO, and CuO), but these catalysts are not stable in a water environment, and do not exhibit catal dic activity at around room temperature and deactivate rapidly, being thus unsuitable for long-term use [183,251,263,265]. 

Manganese oxides have long been known to be catalysts for a variety of gas clean-up reactions. Manganese/copper mbced oxide (Hopcalite) is the catalytically active component in gas mask filters for CO CO is converted to CO2 at room temperature [4]. Further applications of manganese oxide catalysts are the NH3 oxidation to N2 [5], the combustion of VOC [6,7] and methane [8], the oxidation of methanol [7], the O3 decomposition [9] and the NOx reduction [14]. Perovskite-type oxide catalysts (e.g. LaMnOs) have been proven to be effective catalysts for the total oxidation of chlorinated hydrocarbons [10]. Several studies have shown that besides preparation method and calcination temperature the kind... 

Because of the high cost of silver-promoted Hopcalites, attempts have been made to prepare catalysts consisting of silver coated on inert bodies. The major difficulty is that of securing satisfactory adherence of the active material to the support. Wet-method preparations on pumice show good behavior and long catalyst life. 

Roiter (12) removed acetylene from air by passing it over Hopcalite at 160°C. and over pyrolusite ores with added AgMnO< at 40 C. These catalysts were effective for acetylene concentrations up to 10 parts per million, but for higher concentrations the catalyst loses its activity because of the formation of acetylides. 

Low Temperature Oxidatix)n. The majority of heterogeneous catalysts used for oxidation are used at elevated temperatures. However, some of these metal oxide systems are capable of catalyzing specific oxidation reactions at ambient temperature. The most widely studied catalyst of this type is the mixed oxide CuMn204, which is active for the oxidation of carbon monoxide at room temperature. The same catalyst is also an active oxidation catalyst at increased temperatures, and this has been demonstrated in the previous section. The mixed copper manganese oxide is called hopcalite and was first discovered around 90 years ago (96). Early studies demonstrated that manganese oxides promoted with various transition metal oxides were active catalysts. 

Of the non-precious metal catalysts, the sample composed of pure hopcalite showed the highest activity achieving almost full conversion in the temperature window between 130 and 160 °C. The minimum CO concentration achieved was 40ppm. Of the precious-metal catalysts, the platinum/ruthenium samples showed the highest activity, namely more than 99.8% conversion. In particular, the platinum/ruthenium sample based upon the hopcalite carrier showed even higher conversion in the wide temperature window between 90 and 160 °C 7 ppm carbon monoxide were detected in the purified reformate [328]. However, hopcalite is not stable towards moisture, which would generate problems in practical applications [329]. 

The US catalyst was known as Hopcalite 1 and, later, the more active Hop-calite 2 containing 60% Mn02, 40% CuO, was introduced." ... 

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