Abstract
A method of measuring simultaneously the concentration of surface proton and Lewis acid sites is proposed. The method is based on 13C NMR spectroscopy of a suitable adsorbed amine. An investigation of several alkyl-substituted pyridines shows 4-ethylpyridine to be the most satisfactory choice. The method is tested on a silica-alumina cracking catalyst, and found to give good results for total acid concentration. Decomposition of the total acid into proton and Lewis acids requires a higher precision of measurement than presently achieved, but appears possible with existing instruments. Application of the method to silica-alumina with added water shows that the catalyst behavior in the presence of water is more complicated than assumed by previous workers.
Published Version
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