129 45 influence of the

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Unformatted text preview: ............................................................ 129 4.5. Influence of the calcination temperature.................................................... 133 Contents V 5. C onclusions.............................................................................................. 141 6. Literature................................................................................................... 145 1. Introduction 1 1. Introduction 1.1. Motivation Hydrotalcite-type anionic clays, which were chosen as catalyst precursors, consist of positively charged metal hydroxide sheets with metals in the oxidation state +2 and +3. The positive charge is compensated by anions intercalated between the sheets, the space between the metal hydroxide layers is further filled with water. These anionic clays exhibit remarkable properties as catalytic precursors [1, 2, 3]. They retain the same structure despite changes in their composition. Another advantage is the uniform distribution of the metal ions in the layers. This allows investigating changes in the catalysts related to the composition, being able to neglect structural differences. Furthermore, as a result of an appropriate activation, metal containing catalysts may be obtained with a good dispersion of metallic particles that are stable at high temperatures even in the presence of steam [1, 4, 5, 6, 7, 8]. Because of that nickel catalysts derived from hydrotalcite-type precursors are regarded as promising catalysts for the study of high temperature reactions such as the catalytic partial oxidation of hydrocarbons to syngas, a mixture of CO and H2. Such catalysts have recently been proven successful in the partial oxidation of methane by Basile et al. [9]. The catalytic partial oxidation is attracting much attention as new more economic way to produce hydrogen. Hydrogen is a widely used feedstock in the chemical, the food and the refining industry. Especially in refineries the production of hydrogen has achieved increased importance in...
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This document was uploaded on 10/07/2013.

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