Transiation Metal Catalysts

The formation of carbon nanotubes (CNTs) occurs typically between 600 and 1000°C. Due to the low-temperature process, chemical vapor deposition (CVD) method is generally better for the production of the multiwall carbon nanotubes (MWCNTs) as compared to other synthesis methods. The transition metals used for CNT synthesis are Fe, Co, and Ni. The wet impregnation methods are used for binary catalyst preparation and the starting materials are ferric nitrate, cobalt nitrate, and nickel nitrate. The samples are prepared with 1, 3, and 5% catalyst weight percentage with a CaCO 3 substrate. Thermogravimetric and differential temperature analysis (TG-DTA) is

Methane decomposition can be utilized to produce COX-free hydrogen for PEM fuel cells, oil refineries, ammonia and methanol production. Recent research has focused on enhancing the production of hydrogen by the direct thermocatalytic decomposition of methane to form elemental carbon and hydrogen as an attractive alternative to the conventional steam-reforming process. In this context, we review a comprehensive body of work focused on the development of metal or carbonaceous catalysts for enhanced methane conversion and on the improvement of long-term catalyst stability. This review also evaluates the roles played by various parameters, such as temperature and flow rate, on the rate of hydrogen production and the characteristics of the carbon produced. The heating source, type of reactor, operating conditions, catalyst type and its preparation, deactivation and regeneration and the formation and utilization of the carbon by-product are discussed and classified in this paper. While other hydrogen production methods, economic aspects and thermal methane decomposition methods using alternative heating sources such as solar and plasma are briefly presented in this work where relevant, the review focuses mainly on the thermocatalytic decomposition of methane using metal and carbonaceous catalysts. © 2009 Professor T. Nejat Veziroglu.

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