KINETICS OF ZEOLITE DISSOLUTION .4. INFLUENCE OF THE CONCENTRATION OFSILICON IN THE LIQUID-PHASE ON THE KINETICS OF ZSM-5 DISSOLUTION

Dissolution of (Na, TPA)-ZSM-5 in hot (60-degrees-C) 5 m NaOH solution containing different initial concentrations (0, 0.03, 0.0725, and 0.1 46 mol dm-3) of dissolved silica was followed by measuring the silicon and aluminum concentrations in the liquid phase, determining the stag e of polycondensation of silicate anions in the liquid phase, phase an alysis of the solid residues, and following the changes in the particu late characteristics of the suspended ZSM-5, during the dissolution. A n increase of dissolution rate with increasing concentration of silico n in the liquid phase was explained in relation to different reactions that occur in the system.