Microwave assisted green chemistry approach of sodium metaborate dihydrate (NaBO_2 2H_2O) synthesis and use as raw material for sodiumborohydride (NaBH_4) thermochemical production

摘要

In the present study, a novel microwave assisted method has been developed for sodium metaborate dihydrate (NaBO_2-2H_2O) synthesis. Anhydrous NaBO_2, a derivative of borax, is an industrially and technologically important boron compound used as a raw material for the thermochemical production of sodium borohydride (NaBH_4). The effects of different microwave treatment conditions such as microwave power (90, 270 and 360 W) and irradiation time (1, 2, and 5 min) on the synthesis of NaBO_2-2H_2O were examined. After microwave irradiation at 270 W for 1 min, NaBO_2 crystals with 2 molar equivalents of water were formed. Anhydrous NaBO_2 was obtained following incubation at 400 ℃ for 33 min under calcination conditions. Then the resulting anhydrous NaBO_2 powder was reacted with MgH_2 under 60 bar hydrogen atmosphere at 470 ℃, leading to successful production of NaBH_4 with 93% yield.