Naslov
Dissolution Of High-Silica Zeolites In Alkaline Solutions. 2. Dissolution Of Activated Silicalite-1 And Zsm-5 With Different Aluminum Content

Autori
Čižmek, Ankica ; Subotić, Boris ; Šmit, Ivan ; Tonejc, Antun ; Aiello, Rosario ; Crea, Fortunato ; Nastro, Alfonso

Izvornik
Microporous materials (0927-6513) 8 (1997), 3-4; 159-169

Vrsta, podvrsta i kategorija rada
Radovi u časopisima, članak, znanstveni

Ključne riječi
organic-free pentasils ; zsm-5 ; silicalite-1 ; dissolution ; kinetics ; mechanism

Sažetak
Dissolution of organic-free ("activated") high-silica pentasils (silicalite-l and ZSM-5 with different Al-content) in 5 M NaOH solution at 60 degrees C was investigated by different methods such as X-ray diffractometry, Fourier transform infrared spectroscopy (FTIR), scanning-electron microscopy (SEM) and measuring the silicon and aluminum concentration in the liquid phase. Analysis of the experimental results showed that the process of dissolution of the "activated" high-silica pentasils is controlled by two essential reactions ; a forward one caused by breaking of the Si-O-Si and/or Si-O-Al bonds owing to the action of OH- ions from solution, and a backward one caused by the reaction between soluble species from the liquid phase or by their reaction on/with the surface of the dissolving solid. The rate of the forward reaction decreased with an increase of the Al-content in the ZSM-5 crystals, whereas the backward reaction resulted in the formation of amorphous SiO2 (ZSM-5) and/or different crystalline modifications of SiO2 or even different hydrates of sodium silicate (silicalite-l). A kinetic equation of the dissolution process was derived on the basis of the proposed mechanism of dissolution. [References: 19]

Izvorni jezik
Engleski

Znanstvena područja
Fizika, Kemija

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