Ammonia decomposition over commercial Ru/Al₂O₃ catalyst: An experimental evaluation at different operative pressures and temperatures

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• 作者：Andrea Di Carlo ; Luigi Vecchione ; Zaccaria Del Prete
• 关键词：Ammonia cracking ; Hydrogen production ; Ru/Al2O3
• 刊名：International Journal of Hydrogen Energy
• 出版年：13 January, 2014
• 年：2014
• 卷：39
• 期：2
• 页码：808-814
• 全文大小：650 K

文摘

The ammonia decomposition process for hydrogen production was studied experimentally in a fixed bed tubular micro-reactor (I.D.聽=聽1聽cm and h聽=聽20聽cm) filled with 15聽ml of ACTA Hypermec 10010 Ru catalyst. With the aim of pointing out the best process conditions, experiments were carried out varying the reaction temperature between 400 and 500聽掳C, the feeding gas pressure between 1 and 10聽bar and the GHSV (Gas Hourly Space Velocity) between 300 and 2400聽h^鈭?. To maintain the temperature as uniform as possible along the reactor axis, a 3 zone heater was used and each zone was controlled independently. An acid H₂SO₄ trap was used downstream the reactor to remove by neutralization the residual ammonia from the product gas. Moreover, the residual ammonia amount in the gas and thus the NH₃ dissociation were evaluated for the catalyst in different operative conditions by measuring the PH of the trap and its changing rate over time. Dissociations close to the chemical equilibrium were obtained for every GHSV and temperature we tested with a pressures of 1 and 5聽bar in the reactor. In particular, the dissociation was always higher than 99% at 1聽bar, while at 5聽bar it varied from 96% at 400聽掳C to 99% at 500聽掳C. At 10聽bar the chemical equilibrium was reached for all GHSVs only at 450聽掳C and 500聽掳C with dissociations equal to 95.5% and 97.2%. At 400聽掳C a dissociation close to the chemical equilibrium (92%) was reached only for a GHSV of 300聽h^鈭? while for the remaining GHSVs the dissociation was always lower, down to 80.8% for a GHSV equal to 2400聽h^鈭?.

The kinetic parameters of the Temkin-Pyzhev model were evaluated for the ACTA Hypermec 10010 catalyst starting from the literature data on Ru catalyst. The results of this analysis showed that a pre-exponential factor of 1.5聽脳聽10^鈭?聽mol聽m^鈭?聽s^鈭?, an activation energy of 117聽kJ聽mol^鈭? and a reaction order of 0.27 can be adopted for numerical simulations.