A new route to the preparation of nickel-containing microporous catalysts is described. Nickel(H) complexes with the linear polyamine diethyleiletriamine and the small tetraazamacrocycles cyclam, tetramethylcyclam and cyclen template a range of aluminophosphate fluorides, aluminophosphates and Substituted aluminophosphates with framework topologies of type AFI, CHA, SAS, SAV and AEl Calcination of these materials in oxygen at temperatures between 350 and 600 degrees C gives evenly distributed nickel cations or nickel oxide nanoparticles ill the Structures, depending oil the framework composition and the calcination conditions, as shown by EXAFS spectroscopy and elemental mapping in the scanning electron microscope. The catalytic performance for the conversion of n-butane of samples of AIPO-34, SAPO-34 and MgAPO-STA-7 containing isolated Ni(II) species has been measured and compared with samples without nickel. The nickel in these samples becomes reduced in a flow of n-butane to give finely dispersed nickel particles that are active catalysts for methane generation, rather than the C1-C4 product distributions observed for solid acid catalysts with the same frameworks. Ex situ transmission electron microscopy reveals that under catalytic conditions the nickel is reduced and sinters to form nickel metal nanoparticles oil the outside surface of the catalyst.
|Number of pages||8|
|Journal||Studies in Surface Science and Catalysis|
|Publication status||Published - 1 Jan 2005|