Influence of cations on the physicochemical and structural properties of aluminosilicate gel precursors. Part 1. Chemical and thermal properties

Influence of anions on the kinetics of zeolite A crystallization:

“…Hence, it is possible to control the pathway of zeolite crystallization, including structural and particulate properties of crystallized zeolite(s) by controlled addition of different cations into reaction mixture. Generally, structure-forming alkali cations (Li + , Na + ) enhances, and the structure-breaking alkali cations (K + , Rb + , Cs + ) decrease the rates of critical processes (nucleation, crystal growth), and thus the rate of crystallization the low-silica zeolites (A, X) [6][7][8]. Concentration of alkali cations added in the system in an usual way, namely in the form of hydroxides, is limited because OH À ions act as mineralizing agent [1,2,9], and thus, the simultaneous influence of alkali cations and OH À ions on the crystallization process cannot be discriminated.…”

Acid and Alkaline Sol-Gel Synthesis of Amorphous Aluminosilicates, Dry Gel Properties, and Their Use in Probing Sol Phase Reactions

“…ing alkaline silica and alumina sources is often performed in In the 1950s and 1960s, amorphous aluminosilicates were the preparation of zeolites (5)(6)(7). However, most of the time, used in large amounts as acid catalysts.…”

“…Particularly the structural relationships in the field of ceramics since the common direct coprecipitabetween the wet and dry aluminosilicate gels and the re-tion techniques no longer meet the increasing demands on sulting crystalline products have gained a lot of attention product quality and control (8)(9)(10). (5)(6)(7)(8)(9)(10). It has been shown that the synthesis and/or drying Whereas the alkaline synthesis procedure gives rise to procedure of the gel determines to a large extent the effec-high surface charges (16), the presence of alkali cations tiveness of further processing steps such as sintering and may deteriorate the thermal and chemical stability of the products (18).…”

A novel synthesis of nano-sized mullite from aluminosilicate precursors

“…Second reason is their structural composition. The presence of "structureforming" Na + ions in the reaction mixture was needed to enhance the formation of zeolite nuclei in the gel matrix [18][19][20]. Once the nuclei were formed it was possible to remove sodium without destroying the nuclei.…”