Urea Complete Conversion to Compound Fertilizer in Industrial-Scale Tandem Reactors

Area of Science:

• Green Chemistry and Catalysis
• Sustainable Agriculture
• Chemical Engineering

Background:

• Compound fertilizers, essential for crop yield and quality, rely on ammonia (NH3) synthesis via energy-intensive processes.
• Developing efficient, environmentally friendly ammonia production methods for fertilizers is a significant challenge.
• Urea is an abundant nitrogen source, but its conversion into valuable fertilizer components requires advanced catalytic systems.

Purpose of the Study:

• To develop a tandem catalysis system for the complete conversion of urea into compound fertilizer (KH2PO4 and NH4H2PO4) and pure hydrogen (H2).
• To achieve this conversion in industrial-scale reactors using a combined electrochemical and chemical process.
• To establish an environmentally friendly and cost-effective method for ammonia extraction from urea.

Main Methods:

• A tandem catalysis system combining electrochemical and chemical processes was employed.
• Electrochemical process involved precise control of urea consumption and nitrite (NO2-) formation.
• A specific molar concentration ratio of urea to NO2- (1/2) in the electrolyte was maintained for complete urea conversion.

Main Results:

• Complete conversion of urea into solid compound fertilizer (KH2PO4 and NH4H2PO4) and pure H2 was achieved in a single cycle.
• Using 200 g of urea yielded 1580 g of compound fertilizer and 232 L of H2 without by-product formation.
• The process allows for ammonia extraction from urea-containing wastewater or urine.

Conclusions:

• The developed tandem catalysis system offers an efficient and sustainable route for producing compound fertilizers from urea.
• This method significantly reduces the energy requirements and environmental impact associated with ammonia production.
• The anticipated lower cost of fertilizer production presents a viable alternative to current market methods.