Thermal stability and hydrothermal stability are one of the important properties of molecular sieve catalysts to be investigated.

Thermal stability and hydrothermal stability are one of the important properties of molecular sieve catalysts to be investigated. Many industrial catalytic reactions require high thermal stability of catalysts, especially hydrothermal stability, which often determine the life of catalysts and the selection of reaction processes. key.

Taking the catalytic cracking reaction of CTC as an example, since the reaction is carried out under the condition of water vapor, improving the hydrothermal stability of the catalyst is the key to the development of CTC catalysts. The results show that by assembling the catalytic active centers of the porous materials with phosphorus oxides Modification, introduction of skeleton heteroatoms, etc., can improve the stability of the active center of the catalytic material under water vapor condition. The ZSM-5 molecular sieve was immersed in phosphoric acid and then calcined at a certain temperature to introduce an appropriate amount of phosphorus oxides for modification. The experimental results show that, The hydrothermal stability of the catalyst is improved, and the deactivation rate of carbon deposition is effectively slowed down, and the synergistic effect of oxide species in the pores and the framework Si-O-Al optimizes the strength and distribution of acid centers in the porous catalytic material, reducing hydrogen The occurrence of side reactions such as transfer increases the selectivity of propylene. In order to explain the reason for the improved hydrothermal stability of molecular sieves modified by phosphorus oxides, the D2/OH exchange of P/HZSM-5 with different phosphorus contents before and after steam treatment , and the model of the interaction between phosphorus and HZSM-5 was studied by molecular simulation calculation. It was found that the acidity of P/HZSM-5 before water vapor treatment may come from the weaker P–OH acid site, and it varies with the phosphorus content. With the increase of , the decreasing trend of B acid sites gradually slowed down; the high-temperature steam treatment process was accompanied by dealumination, a small amount of phosphorus volatilization, the combination of phosphorus and aluminum species, and the condensation between P species at high temperature. A bridging hydroxyl group different from that in molecular sieves and a new acid site different from P–OH are generated in the ZnO, and these processes lead to a change in the acid properties of P/HZSM-5, a decrease in the density of surface hydroxyl groups, and an increase in the hydrothermal stability. In addition, , for the MTO reaction, a large amount of water is generated in the product, so whether the molecular sieve catalyst is resistant to high temperature hydrothermal and repeated high temperature regeneration is the key to selecting this catalyst. Because of the good thermal and hydrothermal stability of SAPO-34 molecular sieve, it It has become the preferred material for MTO catalysts. In addition, for the reaction of light oil cracking to light olefins, the reaction temperature is usually above 600 °C, which requires high thermal stability and hydrothermal stability of the catalyst. It is necessary to find a higher activity. , catalytic materials with better hydrothermal stability. There are many other refining and petrochemical catalytic reactions, including catalytic cracking in oil refining, which require catalytic materials or carriers with high thermal and hydrothermal stability. Stable porous materials and surface modification methods to improve hydrothermal stability are the focus of attention and research.