| 摘要 |
<p>The present invention relates to methods for the conversion of ammonia in two-stage catalytic systems and can be used in the production of nitric and hydrocyanic acids as well as in the production of hydroxylaminesulphate. This invention essentially relates to an ammonia conversion method which comprises feeding a gaseous mixture of ammonia and of an oxygen-containing gas through a two-stage catalytic system. In the advance direction of the gaseous mixture, the first stage comprises a layer of platinoid matrices while the second stage comprises a layer of a honeycomb, oxide and non-platinoid catalyst. This method also comprises maintaining, in the flows of gaseous mixture circulating through the honeycomb channels of the second stage catalyst, a ratio between the average operation speed and the speed of sound in such conditions which varies from 4.8 x 10-4 to 0.024. The first stage is capable of converting from 86 to 97 % of the total amount of ammonia to be processed. This method comprises using as catalysts for the first and second stages catalytic compositions which are selected from the following series. For the first stage: a composition containing 92.5 % of Pt, 4 % of Pd and 3.5 % of Rh; a composition containing 81 % of Pt, 15 % of Pd, 3.5 % of Rh and 0.5 % of Ru; a composition containing 92.5 % of Pt and 7.5 % of Rh; a composition containing 95 % of Pt and 5 % of Rh; or a catalyst and a sorbant of platinoids according to a composition containing 95 % of Pd and 5 % of Ni. For the second stage: a composition containing 92 % of Fe¿2?O3 and 8 % of Cr2O3; a composition containing 89.5 % of Fe2O3, 5 % of ZrO2, 5 % of MgO and 0.5 % of ZrBaO; a composition containing 79 % of Fe2O3, 20 % of Al2O3 and 1 % of MgO; a composition containing 79.7 % of Fe2O3, 20 % of Al2O3 and 0.3 % of V2O5; or a perovskite containing 90 % of (Cao0.1Lao0.9MnO3), 8 % of Al2O3 and 2 % of SiO2.</p> |
