Molecular sieve manufacturer: use structural information to optimize molecular sieve synthesis

Zeolite is a natural ore with unique physical adsorption properties. Scientists have been trying to synthesize zeolite by reducing the geological conditions formed by natural zeolite. In the early stage, the hydrothermal conversion method was used to synthesize silicate zeolite. However, due to the limitations of chemical analysis and optical analysis at that time, it was impossible to identify whether the zeolite was synthesized. Until the 1940s, scientists discovered the necessary conditions for the synthesis of zeolite, and identified the existence of zeolite through X-ray powder diffraction technology.
The early synthesis work of molecular sieves mainly focused on the influence of alkali metals on the synthesis of molecular sieves, and then turned to the influence of organic structure directing agents on the synthesis of molecular sieves. Do you know how molecular sieves use structural information to optimize their synthesis? Next, the molecular sieve manufacturer will introduce the discovery of aluminum phosphate molecular sieve.
Aluminum phosphate molecular sieve is another major breakthrough in the history of molecular sieve synthesis. Soon, people discovered aluminum silicate molecular sieve. Scientists found that the framework structure of aluminum phosphate molecular sieve is the four-coordination of phosphorus and aluminum atoms, which is similar to the coordination mode between aluminum and silicon atoms in zeolite. Although aluminum phosphate material with micropores has a similar structure to molecular sieve, it is not really molecular sieve technically, because there is no composition of molecular sieve aluminosilicate.
Silicon atoms and phosphorus atoms in the framework of aluminum phosphate and aluminum silicate molecular sieves are alternately coordinated, and also follow the Lowenstein rule applicable to molecular sieves, that is, silicon atoms and aluminum atoms cannot coordinate directly with the same atoms, and it is also found that phosphorus atoms and silicon atoms cannot coordinate directly. Based on the Lowenstein rule, it can be inferred that there are only rings with an even number of atoms in the structure of phosphate materials, that is, rings containing 4, 6, 8 and 12 atoms, resulting in the absence of ring structures with odd number of atoms similar to ZSM-5 and other similar molecular sieves in aluminum phosphate materials. The structure with an even number of rings only exists in molecular sieves composed of aluminum silicate and phosphate.
It was not until ECR-40 molecular sieve was synthesized that an odd number of rings were found in the molecular sieve composed of phosphate. In the structure of ECR-40 molecular sieve, it is found that there is no Si-P coordination and anti-Lowenstein rule Al-Al coordination in the coordination sequence between silicon, aluminum and phosphorus atoms. Therefore, aluminosilicate material has a special structure composed of Al16P12Si6O72, which is different from other aluminosilicate molecular sieves. The preparation process can reduce the ratio of silicon to aluminum to zero, which is the synthesis of aluminosilicate molecular sieves. Using this composition structure, the synthesis route can be optimized, and the yield of molecular sieve in the process of gel synthesis can be improved.