Over the past half century, extensive research has been conducted on the catalytic effects of rare elements (mainly oxides and chlorides), and some regular results have been obtained, which can be summarized as follows:
1. In the electronic structure of rare earth elements, 4f electrons are located in the inner layer and are shielded by 5s and 5p electrons, while the arrangement of outer electrons that determine the chemical properties of the substance is the same. Therefore, compared with the catalytic effect of d transition element, there is no obvious characteristic, and the activity is not as high as that of d transition element;
2. In most reactions, the catalytic activity of each rare earth element does not change much, with a maximum of 12 times, especially for heavy rare earth elements where there is almost no activity change. This is completely different from the transition element d, and their activity can sometimes differ by several orders of magnitude; The catalytic activity of 3 rare earth elements can be basically divided into two types. One type corresponds to a monotonic change in the number of electrons (1-14) in the 4f orbital, such as hydrogenation and dehydrogenation, and the other type corresponds to a periodic change in the arrangement of electrons (1-7, 7-14) in the 4f orbital, such as oxidation;
4. Numerous studies have shown that industrial catalysts containing rare earth elements mostly contain a small amount of rare earth elements, and are generally only used as active components in co catalysts or mixed catalysts.
Essentially, catalysts are materials with special functions. Rare earth compounds have particularly important significance in the development and application of such materials, because they have a wide range of catalytic properties, including oxidation-reduction and acid-base properties, and are rarely known in many aspects, with many areas to be developed; In many catalytic materials, rare earth elements have great interchangeability with other elements, which can serve as the main component of the catalyst, as well as a secondary component or co catalyst. Rare earth compounds can be used to produce catalyst materials with different properties for different reactions; Rare earth compounds, especially oxides, have relatively high thermal and chemical stability, providing the possibility for the widespread use of such catalyst materials. Rare earth catalysts have good performance, various types, and a wide range of catalytic applications.
At present, rare earth catalyst materials are mainly used in petroleum cracking and reforming, automotive exhaust purification, synthetic rubber, and many organic and inorganic chemical fields.
Post time: Oct-11-2023