PRODUCTION OF 15N-ENRICHED NITRIC ACID (H15NO3)

Techniques that employ N-15 have proved to be an important tool in many areas of the agronomic and biomedical sciences. Nevertheless, their use is limited by methodological difficulties and by the price of compounds in the international market. Nitric compounds ((NO3-)-N-15) have attracted the interest of researchers. However, these compounds are not currently produced in Brazil. Thus, in the present work (HNO3)-N-15 was obtained from the oxidation of anhydrous (NH3)-N-15. The method we used differs from the industrial process in that the absorption tower is replaced with a polytetrafluoroethylene-lined, stainless-steel hydration reactor. The process output was evaluated based on the following parameters: reaction temperature; ratio of reagents; pressure and flow of (NH3(g))-N-15 through the catalyst (Pt/Rh). The results showed that, at the best conditions (500 degrees C; 50% excess O-2; 0.4 MPa; and 3.39 g. min(-1) of (NH3)-N-15), a conversion percentage (N-(NH3)-N-15 to N-(NO3-)-N-15) of 62.2%, an overall nitrogen balance (N-(NH3)-N-15 + N-(NO3-)-N-15) of 86.8%, and purity higher than 99% could be obtained.