See what are the effects of rare earths on molecular sieve catalysts.

The introduction of rare earth can stabilize the structure of the zeolite, adjust its acidity and increase its catalytic activity. At an appropriate rare earth exchange rate, an increase in the rare earth content can significantly increase the performance of the zeolite. The position and movement of rare earth ions in the molecular sieve lead to different modification effects.

The rare earth element introduced by precipitation gives the molecular sieve the ability to resist metal contamination. An important field of rare earth application is mainly used to prepare rare earth molecular sieve cracking catalysts.

At present, the catalyst prepared by Y molecular sieve is still in the main process of catalytic cracking. The introduction of rare earths plays an important role in the modification of zeolites. The effects of rare earth catalysts on the performance of catalytic cracking catalysts are reviewed. Summarize and introduce the action mechanism.

The specific surface area and pore volume of the zeolite are reduced, and the influence of La ions is small. This may be due to the addition of rare earth ions to the hydrate and the entry of the aluminum species into the molecular sieve framework, and the molecular sieve collapses the peak temperature of all rare earth exchanges. Above the exchange, it indicates that other rare earth ions also have a stable molecular sieve structure, except for ordinary Los Angeles and Ce.

The results show that the acid strength distribution is improved after the introduction of rare earth ions. However, the rare earth ions are too much to be introduced, and the rare earth ions are free in the cage and cannot form ligands or polarized water molecules. Conversely, the total molecular sieve can reduce the acidity, that is, the rare earth content is controlled within a suitable range.

Another rare earth element is introduced into the zeolite molecular sieve by precipitation. Its main function is to resist metal pollution. The rare earth element introduced by the precipitation mainly exists in the independent stage of the rare earth oxide, and does not contribute to the stability and activity of the molecular sieve. Big.