There is a certain correlation between octamethylcyclotetrasilazane and hexamethylcyclotrimethylazane in production, mainly reflected in the following aspects:
The raw materials are the same: both are usually produced using dimethyl dichlorosilane as the main starting material. In a suitable solvent, dimethyldichlorosilane reacts with ammonia gas to simultaneously produce hexamethylcyclotriazane and octamethylcyclotetrasilazane, as well as the byproduct ammonium chloride. The relevant reaction equation can be simply expressed as: 3 (CH ∝) ₂ SiCl ₂+6NH ∝ → (CH ∝) ₆ Si ∝ N ∝+6NH ₄ Cl; 4 (CH ∝) ₂ SiCl ₂+8NH ∝ → (CH ∝) ₈ Si ₄ N ₄+8NH ₄ Cl.
Reaction competition and transformation: When conducting ammonolysis reaction using dimethyldichlorosilane as raw material, the reaction conditions will affect the proportion of hexamethylcyclotriazane and octamethylcyclotetrasilazane in the product. Generally speaking, lower temperatures and shorter reaction times may be more favorable for the formation of hexamethylcyclotetrasilazane, while relatively higher temperatures and longer reaction times may make the reaction more inclined to form octamethylcyclotetrasilazane. In addition, during the preparation of hexamethylcyclotetrasilazane, a crystal byproduct containing octamethylcyclotetrasilazane is obtained. By adding a specific catalyst such as 4-aminotoluene-3-sulfonic acid and reacting at 120 ℃, octamethylcyclotetrasilazane can be cleaved and converted into hexamethylcyclotetrasilazane.
Separation and purification correlation: The methods used for separating and purifying hexamethylcyclotriazane and octamethylcyclotetrasilazane from the reaction products are similar, requiring filtration, distillation, and other operations. When preparing hexamethylcyclotriazane, after the reaction is complete, the ammonium chloride crystals need to be filtered out first, the solvent needs to be removed by distillation, and finally high-purity hexamethylcyclotriazane can be obtained by vacuum distillation. During this process, impurities such as octamethylcyclotetrasilazane can be separated.
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