PATENTS

3338.            SHAPLEIGH, J. H.  (Hercules Powder Co.).  Gas Mixture for Ammonia Synthesis.  United States Patent 2,578,499, Dec. 11, 1951.  Chem. Abs., vol. 46, 1952, p. 2271.

Corrosion difficulties are encountered in handling NH₃ synthesis gas mixtures containing more than 2 p.p.m. N oxides.  While it is convenient to use fine gases for the N₂ source or to prepare it by the combustion of natural gas, the combustion products may contain as much as 250 p.p.m. N₂ oxides.  A gas mixture for NH₃ synthesis is prepared by mixing flue products from the combustion of hydrocarbon or natural gas with a mixture of H₂ and CO obtained by cracking hydrocarbon or natural gas over a supported Ni catalyst.  An excess of steam is added to this mixture, and it is passed over a CO conversion catalyst (Cr oxide – Fe oxide, Fe oxide, or promoted Fe oxide) at 300°-400°; this substantially reduces the CO content of the gas and the N oxides to <2 p.p.m.