Method for preparing borazine

Abstract

The invention provides a method for preparing borazine, wherein the method comprises the steps: 1, dissolving ammonium salt and borohydride in a solvent, adding liquid ammonia, and carrying out a reaction for 0.5-3 h at the temperature of not higher than 0 DEG C under the protection of inert atmosphere; 2, heating the mixture obtained in the step 1 to 20-30 DEG C, and carrying out a reaction for 0.5-5 h; and 3, heating the mixture obtained in the step 2 to 60-100 DEG C, vacuumizing the reaction system, and carrying out a reaction at the temperature of 60-100 DEG C for 1-3 h to obtain borazine.According to the method for preparing the borazine, high-yield and high-output production of the borazine can be achieved, the method can be used for industrial production of the borazine, and the engineering requirement for preparing a continuous fiber reinforced boron nitride ceramic based composite material by taking the borazine as a precursor can be met.

Description

technical field [0001] The invention belongs to the technical field of inorganic material synthesis, and in particular relates to a method for preparing borazine. Background technique [0002] Boron nitride (hexagonal boron nitride) is a strong covalent bond compound with excellent high temperature resistance, oxidation resistance, ablation resistance, thermal shock resistance, chemical corrosion resistance and good high temperature dielectric and wave transmission properties, such as nitriding Boron does not decompose at high temperatures, only sublimes above 3000 ° C, and has a very low dielectric constant and loss tangent, and can maintain stable electrical properties in a wide temperature range. It is a high temperature resistant wave transparent radome material of choice. In the field of high-temperature wave-transmitting materials, compared with silica-based wave-transmitting composite materials, nitride-based wave-transmitting composite materials have better mechanic...

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Problems solved by technology

The mainstream preparation method of borazine at present is the synthetic method (Inorg.Chem., 1995.34 (4): 1002-1003) of using sodium borohydride and ammonium sulfate to react in tetraethylene glycol dimethyl ether reported by Senddon et al. , but this method needs to react at a temperature of 120-140°C for 3 hours. Since the product borazine has high reactivity, when the temperature exceeds 70°C, the borazine molecules pass through highly active boron-hydrogen bonds (B-H) / nitrogen Hydrogen bond (N-H) reaction occurs self-polymerization, forming white oligomer solid, so that the yield and purity of borazine in the product are greatly reduced, and when using this method to expand the concentration of reactant, the intermolecular concentration of borazine The polymerization reaction is more violent, so that the output of borazine is greatly reduced when the production volume is large

National University of Defense Technology Li Junsheng and others reported the method of using aluminum trichloride as a catalyst to catalyze the reaction of sodium borohydride and ammonium sulfate at 45 °C in tetraethylene glycol dimethyl ether solvent to prepare borazine (Eur.J. Inorg.Chem., 2010,1763-1766), the method catalyzes the reaction of sodium borohydride and ammonium sulfate by adding an aluminum trichloride catalyst, and at a lower temperature of 45°C, a higher conversion is ensured rate, and can effectively avoid the self-polymerization of borazine, but the preparation method has a low temperature, which is not conducive to the efficient collision of borohydride compounds and ammonium salts. Once the amount of a single batch of reactants is increased or the concentration of reactants is enlarged, the reaction The conversion rate of substance and the productive rate of product can reduce greatly, can't guarantee high yield under the situation of single batch high production capacity, the yield of borazine is the borazine prepared by single batch of 60~67%. It is only at the gram level, which cannot be used for high-yield and high-yield production of borazine, and cannot meet the engineering needs of borazine as a precursor to prepare continuous fiber-reinforced boron nitride ceramic matrix composites

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