Alternative catalyst supports for hydrogen cyanide synthesis and ammonia oxidation

Abstract

The authors have examined several alternative catalyst supports consisting of various materials, geometric configurations, and catalyst loadings (Pt and Pt/Rh) for the Andrussow process for HCN synthesis and for the Ostwald process for NH[sub 3] oxidation. With increasing residence time, the HCN hydrolysis reaction decreases the amount of HCN formed. Experiments also show that the addition of Rh to a Pt-coated support slightly reduces the selectivity of HCN synthesis and that catalytically active supports can adversely affect the reaction selectivity. For the Ostwald process, increasing residence times cause the decomposition reactions of NO and NH[sub 3] to contribute and thus decrease the net NO[sub x] formation. In both HCN synthesis and NH[sub 3] oxidation, turbulent, well-mixed flow improves the product selectivity. Based on these tests, guidelines are presented for the design of an alternative Pt-coated catalyst support which gives competitive selectivities and conversions.