ACIDITY MODIFICATION DURING THE AGGLOMERATION OF ZSM-5 WITH MONTMORILLONITE

Ammonia TPD analyses of ZSM-5 zeolites of three Si/Al ratios (15, 30, 43) agglomerated with sodium montmorillonite revealed a noticeable mod ification on the acid properties of the bound zeolites as compared wit h the raw materials. An initial increase of the proportion of the weak acidity was found on the agglomerated zeolites, though the total and strong acidity decreases. The higher the Si/Al ratio of the zeolite, t he higher is this increase. After several steps of ion exchange of the bound zeolites, the acidity reaches the expected values again, and th e total and strong acidities are enhanced at the expense of the weak a cidity. These results were related to a solid-state ion exchange betwe en protons of the zeolite and cations of the clay during the calcinati on subsequent to the agglomeration. (C) 1997 Elsevier Science B.V.