ACID CATALYSIS BY DEALUMINATED ZEOLITE Y. 2. THE ROLES OF ALUMINUM

Article abstract of DOI:10.1021/j100411a026

Hexane cracking activity was determined for a series of dealuminated zeolites which were prepared both by treatment with SiCl4 and by reaction with steam.Over a range of Si/Al ratios from 4.7 to 255 the cracking activity increased in a linear manner with respect to the number of lattice Al ions per unit cell.Thus, a constant turnover frequency is obtained, which is taken as evidence that the acid strenght does not vary over this range of Si/Al ratios.By contrast, a zeolite prepared by deamination of NH4-Y was very much less active than expected on the basis of the number of protonic sites.The acidity of the protons in this material is clearly less than in the dealuminated zeolite.These results support a model of strong Broensted acidity in which a structural aluminum atom has no next-nearest aluminum neighbors in a common 4-ring of the zeolite.