Ht derived catalysts generally exhibit a high thermal

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Unformatted text preview: and reduction procedure [2, 3, 65]. HT derived catalysts generally exhibit a high thermal stability, crucial for any high temperature applications. 20 1. Introduction Tab. 4: Composition of the HT catalyst precursor and their catalytic application [1] Composition Catalytic application Mg6Al2CO3(OH)16· 4 H2O dehydration, catalyst support Ni6Al2CO3(OH)16· 4 H2O methanation, hydrogenation, dealkylation Ni3Mg3Al2CO3(OH)16· 4 H2O hydrogenation, dealkylation, cracking Co3Mg3Al2CO3(OH)16· 4 H2O hydrogenation Co6Al2CO3(OH)16· 4H2O hydrogenation Ni0.9Co0.75Cu0.35Mg4Al2CO3(OH)16· 4 H2O hydrogenation, dehydrogenation Cu3Mg3Al2CO3(OH)16· 4 H2O dehydrogenation of secondary alcohols to ketons, hydrogenation of nitro groups Cu6Al2CO3(OH)16· 4 H2O isomerisation, hydrogenation of nitro groups, dehydrogenation of secondary alcohols to ketons Cu3Zn3Al2CO3(OH)16· 4 H2O dehydrogenation of secondary alcohols to ketons Ni3Zn3Al2CO3(OH)16· 4 H2O hydrogenation Ni3Mg3Al1.8Cr0.2CO3(OH)16· 4 H2O hydrogenation It is well known that the metal cations present in the brucite-type sheets of the HTs play a key role for the catalytic properties of the final catalyst as the catalytic behaviour depends greatly on the chosen metals as the catalytic centres [1]. However, also the anions present between the layers of the HTs can have an important influence on the catalytic properties. The anions present in the HT can also have an effect on other properties like the crystal size of the catalyst. Ni/Al derived from HTs containing carbonate showed smaller crystallite sizes of the NiO and metallic Ni particles and also generally higher activities than those containing nitrate and especially chloride [4, 42, 59, 66]. Nitric oxides, formed upon the calcination of nitrate containing HTs and 1. Introduction 21 ytrtrghrhrhhrhrhhffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff chloride enhance sintering of the NiO particles. Chloride is also a poison for the...
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