Abstract
Ammonia production is a capital-intensive industry as it requires high temperature (400-500oC) and also high pressure (150-300 bar) for its daily operations. An earnest effort was made to synthese ammonia gas using an in-house designed microreactor. The production of ammonia was carried out in a magnetic field reaction zone, with the reaction temperature of 30°C - 280°C and ambient operation pressure. Mn0.8Zn0.2Fe2O4 nanoparticles, synthesized using the sol gel method, were used as the catalyst for the ammonia synthesis. XRD confirmed the single phase ferrites and FESEM images revealed nanofibre-like morphology when sintered at 700oC in argon gas. Electron diffraction was performed using HRTEM and obtained diffraction patterns confirmed the crystal structure of the catalyst. By using the Kjeldahl method it was found that the reaction carried out in 1 Tesla magnetic field gave approximately 46% ammonia yield. The proposed new method could be appealing for ammonia manufacturers due to highly economical implication which may offer urea producers a potential contender in the competitive market place.
Highlights
In most industrial produced ammonia, the catalyst used is magnetite (Fe3O4) and the process is known as the HaberBosch process. This process requires a high temperature in the range of 300oC to 500oC and a high pressure (150-300 atm) giving approximately 14% ammonia yield [1]
In the conventional ammonia production case, the reactor must be able to operate at high temperature (400-500oC) and pressure (150-300 atm) environments to ensure the reaction can be done successfully [3,4]
The as-synthesized nanocatalyst was characterized by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Energy Dispersive X-ray Spectroscopy (EDX) and High Resolution Transmission Electron Microscopy (HRTEM)
Summary
In the first step of the process the nanocatalyst was loaded inside the reactor chamber. Hydrogen gas was introduced into the chamber and set on continuous flow to ensure that the catalyst was maintained in the reduced state. After 1 hour of running the hydrogen gas, the external magnetic field was turned on to magnetize the catalysts. Nitrogen gas was subsequently passed through the reactor chamber for about two hours (Fig. 1). The product (ammonia) was collected in a glass beaker filled with 0.1 M HCl to form NH4Cl (ammonium chloride). Titration (Kjeldahl method) was used to quantify the amount of ammonia synthesised [6,7,8]. The titration approach is shown below: HClreaction + NH3 → NH4Cl NaOH + HClexcess → NaCl + H2O
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