Process for recovering the catalyst in an installation for the enrichment of ammonia in deuterium

摘要

In a process for the enrichment in deuterium of ammonia by isotopic exchange between hydrogen and liquid ammonia in the presence of an alkali metal amide catalyst enriched ammonia containing enriched catalyst, or an aqueous extract thereof, is electrolysed in a first electrolytic cell with alkali metal amalgam as the cathode so as to transfer the alkali metal of the amide into the amalgam, and the amalgam is then used as the anode in a second electrolytic cell containing as the electrolyte ammonia of lower isotopic concentration than the enriched ammonia, so that the alkali metal passes into the ammonia and in the presence of suitable catalysts, either in the second electrolytic cell or in a separate vessel, forms alkali metal amide, the solution of which in ammonia is then used in the isotopic exchange process. If an aqueous extract of the earthed catalyst is formed, the enriched ammonia containing the enriched amide may be treated with deuterium enriched water to form alkali metal hydroxide, the aqueous layer separated from the ammonia layer, and the aqueous solution of alkali metal hydroxide electrolysed to transfer the alkali metal into the amalgam, the remainder of the recovery process being carried out as before. Suitable catalysts for the reconversion of alkali metal into its amide are platinum black or iron, or the oxides of iron or titanium, and the catalysts may constitute the electrodes or the surface of the second electrolytic cell. This reconversion may also take place in a separate vessel from the electrolytic cell, although partial reconversion in the electrolytic cell cannot be prevented even in the absence of catalysts. Gaseous by-products formed in the process are nitrogen when the electrolyte in the first cell is a solution of alkali metal amide in liquid ammonia, oxygen when the electrolyte in the first cell is an aqueous solution of alkali metal hydroxide, and hydrogen in the second cell where the electrolyte is a solution of alkali metal amide in liquid ammonia. In the case where oxygen is produced, it may be used for conversion of deterium-enriched hydrogen to deuterium enriched water in the presence of a catalyst with a divided platinum base, and the water so formed used for conversion of the alkali metal amide to hydroxide. Fig. 1 illustrates the embodiment where enriched ammonia containing amide is electrolysed directly. Enriched ammonia containing enriched potassium amide catalyst leaves the isotopic exchange installation 1 via tube 2, and is electrolysed in electrolytic cell 3 where the cathode 4 is mercury amalgam (Hg+K), the anode being, for example, carbon. Potassium is transferred to the amalgam, and the ammonia solvent is removed via tube 6 to evaporator 7 from which any remaining amide is returned via tube 9 to electrolytic cell 3, and the evaporated ammonia free from amide is condensed and returned to installation 1. By-product N2 leaves cell 3 via tube 10. The amalgam is pumped to the second electrolytic cell 14 into which unenriched ammonia is fed, and electrolysis takes place, the amalgam serving this time as the anode 15. Potassium is released from the amalgam and converted into unenriched KNH2, it being assumed that suitable catalysts are present. The thus formed solution of amide in liquid ammonia is returned to installation 1, and by-product hydrogen is removed via tube 17. The amalgam is pumped back to cell 3. Other Figures not shown illustrate other embodiments as follows: in Fig. 2 conversion of potassium back into KNH2 is carried out in a separate vessel from the second electrolytic cell, and in Fig. 3 is illustrated the embodiment where the enriched ammonia containing the enriched catalyst is treated with enriched water to form a hydroxide solution which is subsequently electrolysed. Figs. 4, 5 and 6 correspond to Figs. 1, 2 and 3 respectively and illustrate the same processes showing rates of flow of gases and liquids through the systems.