氢能因具有高效、清洁、可持续等优点，被认为是最具发展潜力的化石燃料替代能源。氨气作为一种储氢材料，具有高储氢密度、易液化等优点，因此氨分解制氢是一种理想的氢气制备方法。开发中低温下高选择性、高活性、廉价的氨分解催化剂具有重要意义。Ru基催化剂是氨分解活性最高的单金属催化剂，但成本较高，Fe、Co、Ni等过渡金属是Ru的合适替代品。与此同时，催化剂载体的选择是制备高效催化剂的关键因素。采用浸渍法制备了以γ-Al2O3、SiO2、MgO、TiO2为载体，Fe、Co、Ni为活性组分的系列氨分解催化剂，在氨催化裂解反应平台开展了反应温度400～700 ℃、空速比18 000 h-1条件下的催化剂活性评估试验，并在此基础上对合成的催化剂进行了XRD、BET、SEM、TEM等表征分析，探究不同活性组合、载体种类、反应温度等因素对氨催化裂解的影响。结果表明，Ni/Al2O3催化剂活性最高，空速为18 000 h-1、600 ℃时的氨分解率达91.67%，650 ℃时可基本实现氨的完全分解。除SiO2载体外，Ni基催化剂的活性整体高于Fe和Co基催化剂。表征发现在Ni/γ-Al2O3催化剂存在NiO与γ-Al2O3形成的复合氧化物结构，同时γ-Al2O3载体更大的比表面积和孔体积有利于提高氨分解转化率。

Hydrogen energy is considered to be the most promising alternative energy source to fossil fuels due to its advantages of efficient, clean and sustainable. As a kind of hydrogen storage material, ammonia has many advantages such as high hydrogen storage density and easy liquefaction, so hydrogen production by ammonia decomposition is an ideal method for hydrogen preparation. The development of highly selective, active and inexpensive catalysts for ammonia decomposition at low and medium temperatures is of great significance for the development and utilization of hydrogen energy. Ru-based catalysts are the most active single-metal catalysts for ammonia decomposition, but their costs are high, and transition metals such as Fe, Co and Ni are suitable substitutes for Ru. Meanwhile, the choice of catalyst carrier is a key factor in the preparation of efficient catalysts. A series of ammonia decomposition catalysts with γ-Al2O3, SiO2, MgO and TiO2 as the carriers and Fe, Co and Ni as the active components were prepared by the impregnation method, and the catalyst activity evaluation test was carried out in the ammonia catalytic cracking reaction platform at 400 ℃ to 700 ℃ and the air-velocity ratios of 18 000 h-1.On the basis of this, the synthesized catalysts were characterized by XRD, BET, SEM and TEM to investigate the effects of different activity combinations, carrier types, reaction temperatures and other factors on the ammonia catalytic cracking. The results show that the Ni/Al2O3 catalyst has the highest activity, and the ammonia decomposition rate reaches 91.67% at 18 000 h-1 and 600 ℃, and the complete decomposition of ammonia could be basically achieved at 650 ℃. The activities of Ni-based catalysts are overall higher than those of Fe-and Co-based catalysts, except for SiO2 carrier. Characterisation reveales that a composite oxide structure formed by NiO and γ-Al2O3 existed in the Ni/γ-Al2O3 catalysts, while the larger specific surface area and pore volume of the γ-Al2O3 carriers are conducive to the improvement of the ammonia decomposition conversion rate.

0 引言

1 试验

   1.1 原料和试剂

   1.2 催化剂的制备

   1.3 催化剂的表征

   1.4 催化剂的活性评估

2 结果与讨论

   2.1 催化剂的活性评价

   2.2 催化剂表征结果

3 结论