Hydrotalcite-like precursors HTlcs

Co-precipitation is also applied in the synthesis of hydrotalcite-like precursors (HTlcs) for catalysts e.g. based on Cu-Zn-Al, or Co-Al catalysts. Synthetic HTlcs, with a general formula (OHjg] [A ] nHgO, are hydrated hydroxycarbonates of a random lamellar structure. These materials can be visualized as brucite-type octahedral layers, in which cations partially substitute for cations (x = The cations are located in the center of... 

Hydrotalcite-like compounds (HTlcs) have attracted much attention in recent years as catalyst precursors and catalyst support. This is due to (i) their ability to accommodate a large variety of bivalent and trivalent cations (ii) the homogeneous mixture of the cations on an atomic scale and (iii) the formation of thermostable mixed oxides, often denoted as ex-HTlcs, with high surface area upon decomposition. The first two properties are a result of the precursor while the last property appears to be related to the decomposition mechanism. The transitions in the structural properties of Co-based hydrotalcites upon high temperature treatments have been extensively studied in our group.15,16 In the first decomposition step, water is removed from the structure. This transition is followed by dehy-droxylation and decarbonation, as well as carbonate reorganization in the interlayer. Thermal treatment in air finally leads to a solid solution of cobalt spinels (Co(Co, A1)2C>4). Mixtures of CoO and C0AI2O4 are formed upon treatment in inert. 

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