Types of Molecular Sieve Cracking Catalysts for Industrial Use

Types of Molecular Sieve Cracking Catalysts for Industrial Use

According to the classification of molecular sieves, the current industrial molecular sieve cracking catalysts can be roughly divided into three types: rare earth Y (REY), ultrastable Y (USY), and rare earth hydrogen Y (REHY). In addition, there are some retro-type catalysts.

1. REY type molecular sieve catalyst

REY type molecular sieve catalyst has the characteristics of high cracking activity, good hydrothermal stability and high gasoline yield, but its coke and dry gas yields are also high, and the octane number of gasoline is low. The main reason is that it has many acid centers and strong hydrogen transfer reaction ability.

REY type molecular sieve catalysts are generally suitable for straight-run gas oil raw materials, and the reaction conditions used are relatively mild. In the 1970s and 1980s, it was the main cracking catalyst used in my country.

2. USY type molecular sieve catalyst

The active component of the USY type molecular sieve catalyst is the Y type molecular sieve stabilized by dealumination. This molecular sieve framework has a high silicon-alumina ratio, a small unit cell constant, and its structural stability is improved, and its thermal and chemical resistance is enhanced. Moreover, due to the removal of part of the aluminum in the skeleton, the number of acid centers is reduced, and the hydrogen transfer reaction activity is reduced, so that the olefin content in the product increases, the octane number of gasoline increases, and the coke yield decreases.

3. REHY type molecular sieve catalyst

The REHY type molecular sieve catalyst reduces the exchange amount of RE3+ in the molecular sieve on the basis of the REY type catalyst, and replaces it with a part of H+, so that it takes into account the advantages of REY and HY molecular sieves. The activity and stability of REHY molecular sieve are lower than that of REY molecular sieve, but the stability of its crystal structure can be greatly improved by modification. Therefore, REHY type molecular sieve catalyst maintains the high activity and stability of REY molecular sieve, and also improves the selectivity of the reaction. The ratio of RE and H in the REHY molecular sieve can be adjusted as required.