Catalyst continued pentoxide

Asphalt feedstock (flux) is contacted with hot air at 200-280°C (400-550°F) to obtain desirable asphalt product. Both batch and continuous processes are in operation at present, but the batch process is more prevalent because of its versatihty. Nonrecoverable catalytic compounds include copper sulfate, zinc chloride, ferric chloride, aluminum chloride, phosphorus pentoxide, and others. The catalyst does not normally contaminate the process water effluent. 

Both the rate and tire equilibrium conversion of a chemical reaction depend on the tem-peraUire, pressure, and compositionof reactants. Consider,for example, the oxidation of sulfur dioxide to sulfur trioxide. A catalyst is required if a reasonable reaction rate is to be attained. Witli a vanadium pentoxide catalyst the rate becomes appreciable at about 573.15 K (300°C) and continues to mcrease at higher temperatures. On the basis of rate alone, one would operate tire reactorat the highest practical temperature. However, the equilibrium conversion to sulfur trioxide falls as temperature rises, decreasing from about 90% at 793.15 K (520°C) to 50% at about 953.15 K (680°C). These values represent maximum possible conversions regardless of catalyst or reaction rate. The evident conclusion is that both equilibrium and rate must be considered in the exploitation of chemical reactions for commercial purposes. Although reaction rates are not susceptible to thermodynamic treatment, equilibrium conversions are. Therefore, the purpose of this chapter is to detennine the effect of temperature, pressure, and initial composition on the equilibrium conversions of chemical reactions. 

While our studies for identification of the active/selective phase continues, in a parallel effort, we have conducted some experiments to assess the role of dicyclopentadiene, one of the intermediates proposed in the literature [7]. The objective behind this phase of the study was to examine the routes that originate from dicyclopentadiene and result in phthalic anhydride versus maleic anhydride formation. The catalyst used in this set of experiments was vanadium pentoxide that was pre-reduced in situ at 400 °C with hydrogen. 

Catalysts similar to those mentioned for benzene oxidation are applicable to the naphthalene reaction. The early work and published results hav shown that vanadium and molybdenum oxides are effective and quite active catalysts. With supported vanadium pentoxide catalysts, commercial yields of phthalic anhydride on the order of 80-85 per cent of the weight of the naphthalene are obtained. Such catalysts have a long life—6 months or mpre of continuous use—and have yielded up to 20,000 times their weight of phthalic anhydride. Fused or supported vanadium pentox- ... 

Sulfuric acid, one of the most important industrial chemicals, is prepared by a similar method. The acid anhydride of H2SO4 is sulfur trioxide, SO3, Direct oxidation of sulfur produces sulfur dioxide, SOj, which can be subsequently oxidized in the presence of a vanadium pentoxide (VjO ) catalyst to SO3 (see page 420 for discussion of catalysis). The hydration reaction of SO3 is very exothermic. The heat liberated vaporizes the water, and the steam cloud carries away much of the SO3 in the form of a sulfuric acid mist. For more efiectlve results, the SOj is dissolved in concentrated H2SO4 to form disulfiiric acid, 1 38307, while water is added continuously to maintain a constant con-... 

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