The Research Of Plasma Catalytic Decomposition Of Ammonia

The use of ammonia as a hydrogen provider is a better choice because Ammonia is a non-carbonaceous hydrogen resource and there is no COx generation. Noble metals are generally good catalysts for the decomposition of ammonia;however they are too expensive to be used commercially. The reaction temperature of ammonia decomposition over transition metal catalysts is usually too high beyond 500 °C due to poor catalytic activity, which is adverse for application. Dielectric barrier discharge (DBD) plasma is typical non-equilibrium cold plasma that can be obtained at atmospheric pressure. DBD plasma has energetic electrons of 1-10 eV high, which can generate low excited atomic and molecular species, free radicals and ions by non-elastic collision. Non-equilibrium plasma promoted ammonia decomposition might become a novel hydrogen generation method.In this paper, study on hydrogen generation from ammonia decomposition via DBD plasma or the combination method of DBD plasma with non-noble metal catalysts is conducted. Main results are obtained are as follows:1. At room temperature and atmospheric pressure, ammonia can be decomposed under the action of dielectric barrier discharge plasma. Experimental parameters, such as the gap between electrodes, the voltage and frequency of discharge, flow rate of NH₃, the length of discharge space and the materials of HV electrode have impact on the reaction . Among them, the voltage and flow rate of NH3 are the most important factor. By employing a wire-cylinder electrode geometry (the gap between the electrodes 3mm) and conducting the experiment at the condition of ammonia flow rate 10 ml/min, the voltage of discharge 23 KV and the discharge frequency 11 KHz, 93.0% ammonia conversion is obtained.2. By employing a plasma catalytic reactor, A Fe/Al₂O₃ catalyat in the DBD plasma zone and the decomposition of ammonia is carried out with the help of plasma catalysis. At the ammonia flow rate of 40 ml/min, more than 99% of ammonia is decomposed into N₂ and H₂ when the reaction temperature is beyond 390℃ and input power equals to 4.6W. Compared with pure dielectric barrier discharge plasma, plasma catalysis consumes 75% less energy decomposing the same amount of ammonia.