Ice-forming agents are mainly used for cold cloud catalytic operations from -6℃ to 20℃. Silver iodide (AgI) is the most commonly used and effective ice-forming agent because its crystal structure is similar to that of ice crystals, and it is highly effective in making ice crystals. Silver iodide forms extremely large and fine silver iodide particles in the air through combustion or explosion, and 1 gram of silver iodide can produce more than 1000 ice nuclei.

Anti-toxic stability: The ability of catalyst to resist deactivation of adsorbed active poisons is called anti-toxic stability, these poisons refer to compounds containing sulfur, phosphorus, halogens and arsenic, which may be impurities in raw materials, or by-products or intermediate compounds produced in the reaction; various catalysts have different anti-toxic resistance to various harmful impurities, and the same catalyst has different anti-toxic resistance to the same impurity under different reaction conditions.

Although the definition of catalyst is that the catalyst will not be consumed during the chemical reaction, the catalyst will maintain its original chemical state before and after the reaction and will continue to play a catalytic role.

Catalysts are subject to a variety of factors during use and can lose their activity either sharply or slowly. The causes of catalyst deactivation are complex. They can be summarized into some categories as follows.

There are many types of catalysts, which can be classified into liquid catalysts and solid catalysts according to the state; homogeneous catalysts and multiphase catalysts according to the phase state of the reaction system; homogeneous catalysts include acid, base, soluble transition metal compounds and peroxide catalysts.

Chemical reactions that take place in the presence of a catalyst are called catalytic reactions. In a chemical reaction, some of the original chemical bonds of the reacting molecules must dissociate and form new ones, which requires a certain activation energy. In some systems where chemical reactions are difficult to occur, the addition of a third substance (catalyst) that helps rearrange the chemical bonds of the reacting molecules acts to reduce the activation energy of the reaction, thus accelerating the chemical reaction and controlling the selectivity and steric regularity of the products.