Galliation

It is well known that the elements in framework of zeolite molecular sieves greatly influence the properties and behaviors of these materials [1-3], The introduction of heteroatoms into the framework has become one of most active fields in study of zeolites. The investigations were mostly focused on the methods to introduce heteroatoms into the framework (for examples, hydrothermal synthesis and post-synthesis), the mechanisms for incorporations, the effect of heteroatoms on the acid-base properties and the catalytic features of modified samples [1-10]. Relatively less attention was paid to the effect of treatment process on the porous properties of samples although the incorporation of heteroatoms, especially by the so-called post-synthesis, frequently changes the distribution of pore size. Recently, we incorporated Al, Ga and B atoms into zeolites (3 by the post-synthesis in an alkaline medium named alumination, galliation and boronation, respectively. It was found that different trivalent elements inserted into the [3 framework at quite different level. The heteroatoms with unsuitable atom size and poor stability in framework were less introduced, leading to that a considerable amount of framework silicon were dissolved under the action of base and the mesopores in zeolite crystal were developed. As a typical case, the boronation of zeolites (3 and the accompanied formation of mesopores are reported in the present paper. 

Galliation of Zeolites - Liquid-Solid Isomorphous Substitution... 

Table 6.11 Galliation of several zeolites with various Si/A ratios...

Zeolite OFT concentration/(mol/L) Gd203 concentration/(mol/L) Si/Al Si/Ga of galliated zeolite... 

Liu[31] reached the following conclusions for the galliation isomorphous substitution and its mechanism on the basis of the aforementioned investigation in zeolite galliation ... 

A variety of zeolites, especially those with high silica contents, can be galliated with Ga(OH)4 under mild conditions ... 

In 1991, Dwyer and Karim[32] reported another galliation route, which uses ammonium hexafluorogallate to react with zeolite Y under mild conditions, and the reaction proceeds as shown in Equation (6.29). 

At present, this liquid-solid substitution approach has been extended to the secondary synthesis of zeolites containing Si, Fe, Sn, Ti, Cr, and other heteroatoms. An exception is that BF4 cannot be used for liquid-phase dealumination and boron-addition of zeolites to prepare boron-containing zeolites.[33] In the following galliation of NH4Y will be taken as an example to discuss the isomorphous substitution secondary synthesis technique. 

Dapsens PY, Menart MJ, Mondelli C, Perez-Ramirez J (2014) Production of bio-derived ethyl lactate on GaUSY zeolites prepared by post-synthetic galliation. Green Chem 16 ... 

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