Polymerization state aluminate

The proposition of different views on the formation mechanism of zeolites is due to the complexity of the formation of zeolites. The crystallization system of zeolites has solid and liquid components. The solid phase contains amorphous gel and zeolite crystals, while the liquid phase contains silicate ions with various polymeric states, aluminate, and aluminosilicate ions with various structures and polymeric states. The procedure for the synthesis of zeolites is not complicated, but the crystallization mechanism involved is... 

Aluminosilicate zeolites are normally synthesized under basic conditions. The introduction of OH- ions to the synthetic system will necessarily lead to the introduction of correlated cations. These positively charged cations play an important role in the polymerization of polysilicates and aluminates by affecting the polymeric state and their distribution, and have an important effect on the colloidal chemistry of aluminosilicate as well. In addition, cations existing in the synthetic system also have important effects on the formation of the framework structure of zeolites. For example, plenty of synthetic data indicated that a tight correlation between the formation of the SBU cages of zeolites and the charge and size of the cations existed, and this was named the templating effect of cations by R.M. Barrer.[191... 

Many zeolites were crystallized from strongly basic solution containing silicate and aluminate. In strongly basic solution, silicate exists as polymerized-state polysilicates with a variable distribution of molecular weight. Aluminate reacted with polysilicate to form various zeolite structures via condensation reaction under hydrothermal or solvothermal conditions. Therefore, in the study of the synthetic chemistry of zeolites, one of the key issues is to understand the existing state and reactivity of the polymerized silicate. 

Studying the polymerization state of the silicate in the solution during the formation of zeolites is a very important and complex issue. After years of study, it has been found that some correlations exist between the polymerization state of the silicate in the solution and the structure type of zeolites, while the polymerization state and its distribution could be affected by many factors such as alkalinity, nature of the cation, organic templates, temperature, and pressure. These parameters could partially determine the condensation rate between polymerized silicate and aluminate, which will finally affect the formation of zeolite structure. 

Studies[20] on the polymerization state of aluminate in solution have been conducted for a long time and it has been found that the pH of the solution directly affects this state in solution. In basic solution, the main form of aluminate is AI(OH)4. When the... 

Condensation Reaction between Silicate and Aluminate Ions in Solution Along with the ongoing study of the crystallization mechanism of zeolites, it becomes increasingly necessary to study the polymerization state of aluminosilicate ions in solution and the condensation reaction between silicate and aluminate ions. The polymerization state of individual silicate and aluminate ions has been extensively studied, which has been discussed in Section 5.1.1. However, studies on the... 

Most syntheses of zeolites were conducted in strongly basic media. The silicate solution containing alkali metal cations such as Na+ or K+ is one of the main silicon sources in the synthesis of zeolites. The concentration of the basic species in the starting material for the synthesis of zeolites is usually about 0.5 5.5 mol/L. Within this concentration range, aluminate and silicate ions with various polymerization degrees existed in the system. The state and distribution of these ions could be affected by many factors. When the temperature and the concentration of SiC>2 were kept constant, the acid-base... 

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