Technique for preparing ammonia borane by borax-based solid-phase process

Abstract

The invention provides a new method for preparing ammonia borane by a solid-phase process by using borax as a boron source. The method comprises the following steps: mixing borax with trioxymethylene, calcium oxide and solid alkali according to certain mole ratio, adjusting to proper ball / powder ratio and rotation speed, and carrying out ball milling to implement solid-phase conversion from the borax into sodium borohydride; carrying out heat treatment on the material subjected to ball milling at 200-350 DEG C in a protective atmosphere to promote the thorough solid-phase reaction; adding the material into a reflux unit, adding proper amounts of organic solvent and ammonium salt, heating to react under reflux at 25-90 DEG C for 5-15 hours to implement double decomposition reaction between the sodium borohydride and ammonium salt (such as (NH4)2SO4), and carrying out ion exchange to generate an intermediate product NH4BH4 in the liquid phase; and taking out the material, carrying out centrifugal separation, discarding the slag to take the solution, and finally, carrying out liquid-phase rotary evaporation to obtain the white loose solid product ammonia borane (NH3BH3).

Description

technical field [0001] The invention relates to the technical field of synthesis and preparation of new energy materials, in particular to a preparation process of ammonia borane, a solid hydrogen storage material. Background technique [0002] Ammonia Borane, Ammonia Borane, molecular formula NH 3 BH 3 . The melting point of ammonia borane is 104°C. It exists in solid state at normal temperature and pressure. It is soluble in water or polar solvents. It is relatively stable in the air, non-volatile, non-toxic and odorless, safe and reliable. The theoretical hydrogen content of ammonia borane is 19.59wt%, and hydrogen can be released through pyrolysis or catalytic hydrolysis. It is the hydrogen storage compound with the largest unit hydrogen content found in the scientific and technological circles so far, and is considered to be the most promising hydrogen storage one of the materials. [0003] However, the synthesis of ammonia borane is relatively difficult and the pro...

AI Technical Summary

Problems solved by technology

[0003] However, the synthesis of ammonia borane is relatively difficult and the process is complicated, resulting in its high price, which seriously restricts the rapid application progress of ammonia borane

The existing ammonia borane preparation methods mainly contain two categories, one is the borane method, that is, the reaction of borane and liquid ammonia directly prepares ammonia borane, and most of the borane used is diborane, which is flammable and highly toxic. The conditions are harsh and the process is very complicated; the other is the sodium borohydride method, which selects sodium borohydride as the boron source, and reacts with ammonium salts in an organic solvent for several hours under reflux, and then obtains ammonia borane through multiple separations. Although the method is relatively simple and the risk is reduced, the cost of the product ammonia borane is still very high because the boron source used is relatively single, the separation is difficult, and the single-pass yield is low.