Aluminum magnetic susceptibility

It would be expected that chromia-alumina catalysts prepared by coprecipitation techniques should differ from impregnated catalysts, and this difference has been demonstrated by Eischens and Selwood (5) who measured the magnetic susceptibility of a chromia-alumina catalyst (35 wt % Cr) prepared by coprecipitation with ammonium hydroxide from a solution of aluminum nitrate and chromium nitrate. The susceptibility of the reduced catalyst indicated a much greater dispersion of the chromium than was characteristic of the impregnated catalysts. This was attributed to the presence of a three-dimensional dispersion of the chromium in the coprecipitated catalysts, as compared to a two-dimensional dispersion in the case of the impregnated catalysts. 

Magnetic susceptibility measurements were made on the several samples by the Gouy method. Susceptibility isotherms for two temperatures are shown in Fig. 9. These curves gives the susceptibility per gram of chromium in the several catalysts, as a function of chromium concentration. The expected rise of susceptibility with decreasing chromium concentration, and the position of point I are clearly shown, especially at low temperatures. In calculating the susceptibility of chromium in each sample it has been assumed that the susceptibilities of aluminum ions and oxide ions remain constant. This procedure is... 

Kirkpatrick RJ (1988) MAS NMR spectroscopy of minerals and glasses. In Spectroscopic methods in mineralogy and geology, Rev. Mineral., Vol. 18, Hawthorne, FC (ed), p 341-403 Kubicki JD, Sykes D, Apitz SE (1999) Ab initio calculation of aqueous aluminum and alirminum-carboxylate energetics and 27A1 NMR chemical shifts. J Phys Chem A 103 903-915 Kutzelnigg,W (1980) Theory of magnetic susceptibilities and NMR chemical shifts in terms of locahzed orbitals. Isr J Chem 19 193-200... 

Any type of open, porous structure, allowing intimate contact between the solid and aqueous phase, is likely to yield a hydrous phase. In the interaction between water and aluminum, for instance, transmission electron microscopy studies indicate that the initial product consists of very fine fibrils, ca. 3.5 nm thick similarly, Selwood has postulated a threadlike or strand structure to account for the unusually high degree of dispersion evident from magnetic susceptibility studies of various hydrous metal oxide systems. A further obvious possibility here is that open, three-dimensional, cage-type structures (as found, for instance, in zeolites) may be involved. 

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