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A study of the surface acidity of acid-treated montmorillonite clay catalysts

2001; Elsevier BV; Volume: 168; Issue: 1-2 Linguagem: Inglês

10.1016/s1381-1169(00)00540-9

1873-314X

U Flessner, Deborah J. Jones, Jacques Rozière, Jerzy Zając, Loretta Storaro, Maurizio Lenarda, Massimo Pavan, Antonio Jiménez‐López, Enrique Rodríguez‐Castellón, Marcella Trombetta, Guido Busca,

Catalysis and Oxidation Reactions

The surface acidity of a series of commercial Süd Chemie acid-treated montmorillonite clays (K-catalysts) has been evaluated by a wide range of complementary experimental techniques. The different methods applied allow a rather complete characterisation of the surface acidity providing a complete picture of the Lewis/Brønsted acid strength/density of the surface sites. IR data show that the Brønsted sites on these catalysts are relatively weak and provide evidence for a slight increase of the strength and the density of Brønsted sites in the order K5<K10∼K20<K30 in full agreement with the trend in iso-butene conversion, which is a measure of the strength and/or the abundancy of Brønsted sites. The apparent contradiction of these data with those obtained from the ammonia adsorption and iso-propanol conversion experiments can be explained by the structural and chemical modification of the clays upon acid treatment.