A kind of method for preparing borazine

Abstract

The invention provides a method for preparing borazine, comprising: the first step, dissolving ammonium salt and borohydride in a solvent, then adding liquid ammonia, in an inert atmosphere protection, at a temperature not higher than 0°C The reaction time is 0.5-3h; the second step is to heat up the mixture obtained in the first step to 20-30°C for 0.5-5h; the third step is to heat up the mixture obtained in the second step to 60-100°C while the reaction system Vacuumize, and then react at 60-100°C for 1-3h to obtain borazine. The method for preparing borazine can realize high-yield and high-yield production of borazine, can be used for industrial production of borazine, and can meet borazine as a precursor to prepare continuous fiber-reinforced boron nitride ceramics Engineering needs of matrix composites.

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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