The production of urea, including nano-urea, involves the reaction of ammonia (NH3) and carbon dioxide (CO2).

 The production of urea, including nano-urea, involves the reaction of ammonia (NH3) and carbon dioxide (CO2). This reaction typically proceeds in two steps: first, ammonia and carbon dioxide react to form ammonium carbamate, which then decomposes to form urea and water. In nano-urea production, this process may be optimized at the nanoscale to enhance reaction rates and product properties. 

Here's a more detailed breakdown:

1. Conventional Urea Synthesis:

Ammonia and carbon dioxide are reacted under high temperature and pressure (e.g., 180-210°C and 180 bar).

The first reaction, producing ammonium carbamate, is exothermic (releases heat).

The second reaction, converting ammonium carbamate to urea, is endothermic (requires heat).

The overall conversion of CO2 to urea is typically around 65%. 

2. Nano-Urea Synthesis:

Nanoscale Optimization:

Nano-urea production utilizes techniques to enhance the reaction at the nanoscale, potentially leading to increased efficiency and different product characteristics.

Supercritical CO2:

In some methods, supercritical CO2 is used, which has unique properties that can improve mass transfer and reaction rates according to Google Patents.

High Surface Area:

The use of nanoporous materials or rotating surfaces can increase the surface area available for the reaction, promoting faster reaction rates.

Reduced Particle Size:

Nano-urea particles are produced with specific size and properties, potentially improving their effectiveness as a fertilizer. 

3. Key Considerations:

Reaction Conditions:

Temperature, pressure, and the molar ratio of ammonia to carbon dioxide are important parameters in both conventional and nano-urea synthesis. 

Byproducts:

Biuret is a byproduct of urea formation that can be undesirable. Optimizing the process can help minimize its formation. 

Reaction Mechanism:

Understanding the reaction mechanism, including the formation of ammonium carbamate as an intermediate, is crucial for optimizing the process. 

In summary, while conventional urea production relies on high-pressure and temperature reactions, nano-urea synthesis aims to leverage nanoscale phenomena to improve the process and potentially create a more efficient fertilizer, according to ResearchGate.