Recebido em 24/3/03; aceito em 21/7/03 CHEMICAL RECYCLING OF SPENT COMMERCIAL ZEOLITES. Pyro and hydrometallurgical processes were applied to the treatment of spent commercial zeolites (a molecular sieve and a ZSM-5 sample). Both catalysts were employed in pilot plant units. They were kept in their original shape, they were not regenerated and were not subjected neither to mechanical stress nor to overheating zones during their time on-stream. Two recycling processes were tested: (i) direct solubilization of samples in mixtures of HF + H 2 O 2 (60 o C, 1 h). Although silicon was solubilized, insoluble matter was found in both samples, particularly in the molecular sieve, due to its high amounts of alkaline and alkaline-earth metals; (ii) fusion with KHSO 4 (5 h, 600 ºC) with KHSO 4 /zeolite mass ratio 6:1. After fusion the solid was solubilized in water (100 ºC), leaving silicon as SiO 2 residue. In both processes, solubilized metals were isolated by conventional selective precipitation techniques. Analysis of final products by common analytical methods shows that metals present in the original catalysts were recovered with very high yields except when the molecular sieve was treated with HF + H 2 O 2. This reactant mixture proved to be suitable for processing zeolites with a low alkaline and alkaline-earth metal content whereas fusion with KHSO 4 appeared to be adequate for all types of zeolites.
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