Acid Strength of Pt-Zeolite Catalysts: Evidence of Metal-Support Interaction from Linear Free-Energy Relationship
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The acid strength of Pt-HBeta and Pt-HMordenite zeolite catalysts were estimated by H/D exchange of substituted benzenes with the use of linear free-energy relationship, through the use of the Hammet–Brown equation. The results indicated that compared with the parent acidic zeolite, the incorporation of Pt metal leads to a significant decrease in the acid strength, estimated by the slope (ρ) of the logarithm of the relative rate (k X/k H) with the σ+ constant of the substituent, indicating a lower degree of proton transfer to the ring in the transition state. The results support the model of metal-support interaction in Pt-zeolite catalyst, with formation of a metal-proton adduct.
KeywordsZeolites Acid strength Catalysis Linear free-energy relationship
Authors thank financial support from CNPq, FAPERJ and PRH/ANP.
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