The protonic acid content of some acid-type solid catalysts was determined by base exchange with 0.1 N ammonium acetate solution followed by pH measurement. This procedure also permitted evaluation of the relative acid strengths of the catalysts. Measurements were made on silica-alumina catalysts of various compositions after heat treatments ranging from 100 to 900°and were compared with data from non-aqueous butylamine titrations and propylene polymerization tests. Polymerization activity correlated better with protonic acid content than with total acids determined by butylamine titration for the entire composition range from pure silica to pure alumina. The results are consistent with the view that protons on the catalyst surface are necessary for acid catalysis such as heat treatment at 900°was regained by rehydration.
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