Effect of Si-Al ratio on ZSM molecular sieve

The Si/Al ratio (Si/Al ratio) is an important property of ZSM molecular sieve, which reflects the relative content of Si and Al in the molecular sieve. This ratio has an important effect on the activity and selectivity of ZSM molecular sieve.
First, the Si/Al ratio can affect the acidity of ZSM molecular sieves. In general, the higher the Si-Al ratio, the stronger the acidity of the molecular sieve. This is because aluminum can provide an additional acidic center in the molecular sieve, while silicon mainly determines the structure and shape of the molecular sieve.
Therefore, the acidity and catalytic activity of the molecular sieve can be controlled by adjusting the Si-Al ratio. Secondly, the Si/Al ratio can also affect the stability and heat resistance of ZSM molecular sieve.
Molecular sieves synthesized at higher Si/Al ratios often have better thermal and hydrothermal stability.
This is because silicon in molecular sieve can provide additional stability, resistance to reactions such as pyrolysis and acid hydrolysis. In addition, the Si/Al ratio can also affect the pore size and shape of ZSM molecular sieves.
In general, the higher the Si-Al ratio, the smaller the pore size of the molecular sieve, and the shape is closer to the circle. This is because aluminum can provide additional cross-linking points in the molecular sieve, making the crystal structure more compact. In summary, the effect of Si-Al ratio on ZSM molecular sieve is multifaceted.
By adjusting the Si-Al ratio, molecular sieves with specific pore size and shape, good acidity and stability can be synthesized, so as to better meet the needs of various catalytic reactions.