Urea Complete Conversion to Compound Fertilizer in Industrial-scale Tandem Reactors.

A compound fertilizer with NH4H2PO4 and KH2PO4 offer significant advantages in enhancing both crop yield and quality. Ammonia (NH₃) is essential for the synthesis of the compound fertilizer, which was produced by an energy intensive chemical process. Developing efficient and environmental friendly methods to produce ammonia-containing compound fertilizers is crucial and extremely challenging. Here, we present a tandem catalysis system capable of achieving complete conversion of abundant urea into compound fertilizer in industrial-scale reactors by combining electrochemical and subsequent chemical processes. In a typical cycle, with the use of 200 g urea, 1580 g of solid compound fertilizer (KH2PO4 and NH4H2PO4) and 232 L of pure H2 are produced without any further separation process. The key to the realization of this system is to precisely control the rate of urea consumption and NO2- formation in electrochemical process. By maintaining a precise molar concentration ratio of urea to NO2- at ½ in electrolyte, urea can completely react with NO2- to form N2, while CNO- can be converted into NH4+ to form compound fertilizer in the second step of H3PO4 treatment, achieving complete conversion of urea without by-products formation.