A process for the thermolysis reaction of tetraethylammonium borohydride to yield bis(tetraalkylammonium) decahydrodecaborane which comprises:
- (i) combining Et.sub.4 NBH.sub.4 in a mole ratio from about 0.3 to 1.0 with a boron-based solvent Et.sub.4 NBH.sub.3 in a mole ratio from about 0.2 to 4.0 to form a reaction mixture, (wherein Et is C.sub.2 H.sub.5), in a thermolysis reactor vessel having a plurality of outlets for various functions including an outlet for the introduction of reactants and an inert gas, an outlet through which the reaction temperature is monitored, and an outlet for discharging reaction products to a recovery system, said reactor vessel provided with an immersion oil heating means for heating including a temperature control means for controlling the reaction temperature, a means for maintaining an inert atmosphere of nitrogen over said reaction mixture, and a temperature measuring means for measuring temperature of the reaction mixture;
- (ii) connecting one of said outlets of said reactor vessel to a recovery system comprised of a tube member having a heated tube section on one end to prevent any reflux action to said reaction vessel, and said tube member having an air-cooled condenser section on the other end of said tube member, said air-cooled condenser section being connected to a distillate receiver, said distillate receiver having a discharge outlet that is connected in series with a 0.degree. C. cooled trap, a -78.degree. C. cooled trap, a back pressure regulator, and a wet test gas meter;
- said cooled traps for collecting the condensable gases and said wet test gas meter for measuring the non-condensable gases;
- (iii) introducing and maintaining an inert atmosphere of nitrogen in said reactor vessel and said recovery system;
- (iv) heating said reaction mixture while stirring and controlling said reacting mixture to maintain a thermolysis temperature between about 175.degree. C. and 186.degree. C. for a reaction time from about 1 to about 2.5 hours until chemical reaction ceases;
- (v) removing said reactor vessel from said immersion oil heating means, and cooling the residue in said reactor vessel to room temperature;
- (vi) filtering off any remaining triethylamine borane solvent and recovering the filter cake;
- (vii) washing said filter cake with hexane to remove any additional triethylamine borane;
- and
- (viii) drying said washed filter cake to remove any hexane adhering to said filter cake to yield (Et.sub.4 N).sub.2 B.sub.10 H.sub.10.