Bellamy-Hallam-Williams plots

Modified Bellamy-Hallam-Williams plot of shift in OH frequency of acidic hydroxyl groups of different zeolites against the shift in frequency of framework silanol hydroxyls as probe molecules of different basic strengths (represented by numbers 1-17) are adsorbed. See reference for details. [Figure reproduced from reference 23 with permission. Copyright 1997 American Chemical Society.]... 

A systematic way of carrying out such a comparison makes use of the so-called Bellamy-Hallam-William plot, a procedure borrowed from solution chemistry, which is as follows. A set of molecules of basic nature is considered. The shift suffered by H-bonding to each molecule in this set is measured by the O - H stretching mode of an acidic hydroxyl (e.g., in H-ZSM-5) and successively plotted against the same type of data for a reference O - H species (e.g., the isolated silanol in H-MCM-41). A proportionality is seen, the slope of the straight line constituting a measure of relative acidity of the two hydroxyl species. 

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