Theory and Practice in Industrial Utilization

Theory and Practice in Industrial Utilization 1. Composite Catalyst Bed 

In an earlier paper (Nielsen, 5) the author has used the term thermo-resistancy to characterize the quality of the catalyst to keep its activity, and a certain set of experimental conditions were standardized as thermo-resistancy test conditions. For catalysts designed for use at about 450°, it was chosen to measure the difference between the activities measured, at 450°, 330 atm., and S.V. = 16,000, before and after a 20-hour run at 550°. In Table VI are shown the results of thermoresistancy tests on the 

Catalyst sistancy test0 °C. atm. Hours sistancy test0 A% NHi 

The method of reduction influences the properties of ammonia catalysts. A generally appropriate reduction schedule cannot be prescribed because different types of catalysts call for different reduction procedures to reach their most active state. It has previously been mentioned that the promoters used in ammonia catalysts have a retarding effect on the reduction. According to the author s experience, oxides of the alkaline earth metals, especially CaO, make the catalysts especially difficult to reduce. As will be remembered these oxides enter the magnetite matrix readily. 

The author supports the view of Latchinov and co-workers that all conditions tending to increase the concentration of water vapor in the gas during the reduction diminish the activity of the catalysts, thus high space velocity and low temperature and low pressure yield the most active catalysts. Water vapor influences areas of the catalyst already reduced in the same way as water vapor influences a totally reduced catalyst, which means that it inflicts it with a progressive permanent deterioration. 

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