Answer to Question #83680 in General Chemistry for ahmed Al Bulushi

Question

Why is Platinum catalyst gauze used for ammonia oxidation in the production of nitric acid? What are the safety requirements or percussion for this catalyst?

How to avoid Platinum catalyst gauze from getting spoiled?

what the advantages and disadvantages of Platinum catalyst gauze?

Answer 1

During the manufacture of nitric acid by the oxidation of ammonia, platinum-rhodium and platinum-palladium-rhodium alloy gauzes are used as catalysts. Traditionally the process is carried out in the temperature range 750 to 950 °C and pressures of 1 to 10 atmospheres, and under such conditions the volatile oxides of platinum, palladium and rhodium, PtO2, PdO and RhO2, respectively, are formed on the catalyst surfaces. The volatilisation and mechanical attrition can cause the catalyst alloys to lose weight. The weight lost from the catalyst gauzes is mainly due to platinum loss. In fact, apart from ammonia consumption, the major factor affecting the cost of nitric acid production is the loss of platinum. The platinum lost from catalyst gauzes during nitric acid production depends on the properties of the catalyst alloys, the operating conditions and the technical control.

A coiled platinum wire catalyst is used to catalyse the oxidation of ammonia. Similar heterogeneous catalysts are used extensively in industry because they are robust at high temperatures, which allows for a wide range of operating conditions. An additional benefit is there are no extra steps required to separate the catalyst from the product. Typically, gaseous reactants enter a tubular reactor at one end, pass over a supported catalyst and the products are collected at the other end.