Dealumination equations

Thus, dealumination may be effected by reaction with SiCli, the reaction being postulated to occur as in equation [10]. 

If however dealumination follows dehydroxylation and equation (28) applies, then the N/Al is given by ... 

It is thus concluded that the dealumination process of Ktihl [36] leading to equation (28) did not happen in these samples in agreement with the conclusions of Kazansky [37]. 

Min investigated the reaction mechanism of this dealumination approach.[24] Breck and Skeels had found that, in the ammonium hexafluorosilicate solution, the extraframework silicon atoms could substitute for the aluminum atoms in the crystal lattice of the zeolite framework, but the mechanism of the whole reaction process was not clear. Through 29Si,27Al-MAS-NMR and IR characterization techniques, Min and coworkers investigated the removal of A1 atoms from the zeolite framework, the chemical environment of the extraframework silicon atoms, and the species of the silicon that can be inserted into the Al-removal framework vacancies during the reaction process, and finally they proposed the reaction mechanism [Equations (6.18)-(6.25)] as follows. 

It has been reported that F2, phosgene COCI2, and SiCU can be used for gas-phase dealumination. The commonly used method to obtain dealuminated zeolites involves SiCU (gas)-zeolite (solid) replacement. In 1985, Beyer[25] reported the preparation of high-silica Y-zeolite and even pure-silica Y-zeolite through interaction of SiCLt with NaY for dealumination and Si-addition. This technique is based on the fact that at high temperatures SiCl4 can easily react with zeolites to dealuminate, and the main reaction is given by Equation (6.27). 

Phenols react with deactivated carbonyl compounds such as chloral (2,2,2-trichloroethanal) in the presence of different dealuminated protonic zeolites (Y-EAU, MOR, MFI and BEA) to give the corresponding carbinols. A high para-selectivity was achieved using HBEA zeolite (Si A1 = 12.5) (equation 18). ... 

The adsorptive and catalytic properties of zeolites HY, HZSM-5 and HM (natural and synthetic) subjected to dealumination, ion exchange with rare-earth and transition elements have been studied.The changes in conversion and selectivity for w-xylene and n-pentane are shown to be connected with the changes of the zeolites microporous structure.These changes are in conformity with DR equation parameters. The DR equation could be applied to the simple test method elaboration of the starting and modified zeolites microporous structure through their adsorptive properties. 

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